ENHANCED RECOVERY, AN ENCHANTING EXPERIENCE!

The Science, art and practice of Anaesthesiology are changing day by day.The recent advances and researches in the field aim at a faster, safer and smoother recovery from anaesthesia, enabling patients to resume their normal day to day activities early..The elective, day care and office based anaesthesia services have improved so much and the concept of enhanced recovery is widely accepted for practice. Enhanced recovery practices aim fast but smooth recovery following surgery and anaesthesia thereby reducing  patient discomfort, length of stay in hospital,prevent loss of manpower and increase productivity.This is achieved not just by cutting short anaesthesia or by providing inadequate or insufficient anaesthesia or by cutting short some surgical procedures but by avoiding certain medications or procedures by surgeons or anaesthetists which may  actually delay recovery. It has been clearly shown by studies that enhanced recovery benefits much to colorectal, orthopedic urologic and gynae cological surgeries in terms of early mobilisation, reduction of complications and quality of life.

The single intervention or individual components of a certain surgical procedure, when implemented together as a group have a greater impact on the overall outcome of that procedure.This is the fundamental theory or concept behind enhanced recovery  programmes.Even though the concept aims better and early post operative rehabilitation it gives utmost care to preoperative and intra operative assessment and care to make the morbidity less and to provide the highest possible quality of care  to patients undergoing surgical procedures.

The Components of Enhanced Recovery Programme.

1. Referral from a general practitioner to specialist

• Evaluation of  co morbidities like blood sugar and hypertension
• Optimization of hemoglobin level
• Advise to quit smoking
• Advise on limitation of the use of alcoholol

2.Pre operative optimization by Anaesthetists, Physician, and Surgeon.

• Management of Hypertension or Diabetes
• Informed consent and decision making by patient
• Optimization of drug therapy, minimizing the current medications or medication reconciliation
• Advise on postoperative oral intake or mobilization
• Discharge planning should be explained with full instructions given about  current medication and stoppage of medication.      
  
  

3.Pre operative preparation

• Admission on the day of surgery, Careful planning and advise to patients  about preoperative preparation and procedures make it possible for them to get admitted on the day of surgery . The whole documentation including consent must be completed before admission.Preoperative optimization including all necessary investigations and review must be made.
• Avoidance of bowel preparations; Bowel preparation adversely affects normal bowel recovery especially in colorectal surgeries.There is less risk of dehydration in colorectal and urological surgery when oral bowel preparation is not routinely used.It also helps in carbohydrate preloading.
• Avoidance of prolonged fasting; Prolonged starvation adversely affect tissue hydration and serum electrolytes.Minimize  fasting time and avoid overnight fasting orders.Fasting time of 2 hours for liquids and 6 hours for solids appropriate.Avoid over hydration too...

• Carbohydrate drinks. Encouraging patients to take carbohydrate drinks (carbohydrate preloading) helps to prevent protein catabolism. It also helps to prevent insulin resistance due to stress response.Carbohydrates provide energy during the fasting period and during surgery and studies have proven that carbohydrate preloading has positive outcomes during recovery and better perioperative control of body metabolism.Use specially formulated oral fluids (complex carbohydrates) that are rapidly emptied from the stomach as they have a relatively low osmolality. CHO loading also helps to reduce patient anxiety, reduces inflammatory response  and improve hydration.CHO preloading (drink) may be given 12 hours prior to surgery and up to two hours before reaching the operation suite.For patients with diabetes and delayed gastric emptying necessary precautions may be taken and the second dose may be avoided.

• Avoidance of sedative premedication.Sedative premedications especially long acting sedatives should be avoided as the residual effects can be avoided. To allay anxiety small dose of nonsedating anxiolytics preferred 
  

4.Intra operative care

• Always use minimally invasive techniques, especially laparoscopic resection.
• If the abdomen needs to be opened a transverse incision is recommended than longitudinal cuts.This will reduce post operative pain and subsequent use of sedatives or narcotics
• Avoid wound drains if possible. In colonic surgeries drains have been shown to be of no benefit.
• Avoid nasogatric tubes as they increase morbidity in bowel surgeries
• Individualized goal directed fluid therapy helps to avoid over hydration or dehydration. But central lines must be avoided.Fluid administration based on cardiac output monitoring recommended and esophageal doppler will be  of great help in this. Judicial use of colloids helps to administer the right minimal amount to keep the cardiac output.
• Anaesthetic care : Use short-acting anaesthetic agents whenever possible.Fentanyl and propofol are chosen for intravenous induction and for maintenance desflurane or sevoflurane may be used.Midazolam may be avoided.Remifentanyl based total intravenous anaesthesia is found to be useful.For abdominal and colorectal surgeries epidural anaesthesia is preferred.They are also helpful to reduce stress response to surgery or may be beneficial to combine with General anaesthesia to reduce the dose of intravenous or inhalational agents.Epidurals also help to prevent post operative paralytic ileus by blocking sympathetic discharge.Excellent post op analgesia by epidural LAs  without sedative effects helps early mobilisation or ambulation of post operative patients.Intraoperative use of ondansetron, droperidol or dexamethasone help to prevent PONV during emergence or in the post op period.Risk stratification of PONV using apfel scoring system and aggressive prophylaxis and treatment of PONV are recommended.Hypothermia may prolong recovery so intra operative warming devices and warm fluids must be used.Transverse abdominal plane block or TAP block is also an excellent choice for post operative pain relief especially in laparoscopic surgeries.Avoid the use of drains and nasogastric tubes as nasogastric tubes delay gastric emptying and may trigger nausea and vomiting. Nasogastric tubes and drains  can affect a patient’s ability to mobilise as they always create a psychological barrier for early mobilisation attempts. Drains should be avoided If NGT is essential it may be removed immediately at the end of surgery.Even though early mobilisation reduces the risk of DVT, Thromboprophylaxis is recommended in selected cases especially limb surgeries.

 5.Post operative care

• Active planned mobilization should be initiated within 24 hours.IV lines and catheters must be removed early.Patients must be encouraged to start early oral feeding  which will prevent dehydration and reduce the chances of post op ileus.Also it is proven that early feeding helps to prevent surgical wound infections.Post operative hyperglycemia must be avoided in diabetic patients.Epidural catheters may be removed early after administration of parenteral NSAIDS.For moderate to severe  pain oral opioid analgesics may also  be supplemented along with NSAIDS.Physiotherapists have an active role in early patient mobilization.Regular follow up should should be done and the follow up process should extend to the post discharge period also. This is achieved by a dedicated clinical staff who can communicate to the patient over telephone who will be informing the clinician about the status of recovery. Discharge is planned as per protocols and criteria.

Benefits of enhanced recovery programme 

• In UK, the process is active and an ENHANCED RECOVERY PARTNERSHIP PROGRAMME (ERPP) has been formed with participation of department of health, NHS cancer team  and the Royal colleges.The aim of the programme is to create  awareness among Physicians, Surgeons and General public about the advantages and benefits of early recovery thereby improving patient care, improving productivity, reducing morbidity and cost.

• Improved clinical outcome and early detection of complications are possible.Earlier return to work or social activity improves productivity and social well being.Reduced hospital stay reduces cost and hospital acquired infections.Reduced waiting time for surgery as the patients are prepared early for surgery.Early mobilization helps to prevent bowel dysfunction and DVT.
•  Finally, there are improved relationsh ips between primary care and hospital trusts and better
  Since a multidisciplinary team is involved in patient management improved communication and exchange of ideas improve patient care.Overall improvement in patient care and quality makes the process a nice experience for patient and health care team making enhanced recovery an enchanting experience.
  

References:

1.http://www.frca.co.uk/Documents/204%20Enhanced%20recovery%20after%20surgery%20%28ERAS%29.pdf

2.http://www.medscape.org/viewarticle/579805_2

3.http://www.nhsiq.nhs.uk/media/2433399/ijoa_er_editorial_lucas_ijoa_april_2013.pdf

4.http://www.frca.co.uk/Documents/204%20Enhanced%20recovery%20after%20surgery%20%28ERAS%29.pdf

EGO, WHERE YOU GO?

Professional ego is commonly observed in medical profession.It is the basic nature of every human being to claim the superiority over others thinking that he is more perfect and has got additional capabilities over his fellow colleagues.Medical profession is no exception.Among the physicians ego is more common among the anaesthesiologists because the choice and techniques to anaesthetise a particular patient are diverse and are based on individual experience and expertise

Several techniques and methods are possible to anaesthetise  a particular patient or to perform a particular procedure, (with the procedural advantages or complications specific to each of them) Often there will be debate on which technique is superior or suitable to the procedure.Individual experience may favour one to go for a particular procedure which may be deferred by others. Often the senior fellow or consultant will win in this argument as he is more powerful to execute his commands. In such instances it was advised to follow standard protocols or evidence based techniques,or majority opinion.Healthy discussions based on standard literature will help the clinicians to formulate an action plan and to proceed, which may help in their professional and academic improvement.

If the consultant is not successful with the procedure he proposed and that too witnessed by  his colleagues he may feel ashamed but  he may declare that the procedure is difficult but his ego does not permit him to allow his juniors to repeat the procedure and he may go for an alternate procedure.As a result the patient may suffer as he is not able enjoy the advantage of that particular procedure.This is true when epidural anaesthesia is to be performed for a hypertensive patient or PIH patient where a change in hands may make the procedure less difficult and often successful and the patient is gaining the benefit of regional anaesthesia over GA.

The procedural ego unveils especially when somebody fails to perform upto their self expectations.The physician will be tensed and nervous and keep on trying. During unsuccessful intubation he may not hand over the case to his fellow and instead keep on trying, introducing trauma and making the airway more difficult for others to manage.I have observed a specialist attempting  more than 8 times to insert a spinal needle in an obstetric patiebnt for caesarean, while the consultant observing this is advising him repeatedly to abandon the procedure and go for GA. The specialist was not giving ears as he thought, failing the procedure in front of staff  and gynaecologists may affect his reputation badly.This patient suffered severe post spinal head ache with nystagmus and vomiting for several days post op.You may also find some instances in regional anaesthesia procedures where the junior kept on praying that his senior should fail because he has already failed to perform. He is seen depressed and withdrawn the whole day because the senior was successful in single attempt.

Ego with investigations,was also observed  among a few anaesthetists, when they delete or modify some of the preoperative investigations ordered by surgeons.The anaesthetist may ask for a fresh set of investigations just because the previous tests were ordered by a surgeon. This is because many feel interpreting investigations ordered by other doctors is an inferior job but they are not aware of the financial burden, physical strain and pain involved in repeating the lab tests.

Ego with paramedics and nursing staff, needs to be mentioned.The physician's ego doesn't permit him to accept minor mistakes by him, which are pointed out by nursing staff or technicians.Look at this incidence, A faint pneumothorax shadow in X ray was missed by an anaesthesia specialist  but was observed by an X ray technician.The technician took the X ray and reported back to the specialist.Instead of admitting his mistake and attending the patient in ICU, the specialist filed a petition to higher authorities against the technician's rude behaviour! This is not appropriate as your ego should allow to appreciate and complement them.

Ego with patients,Here the physician fails to explain in detail about the anaesthetic procedure and about its complications.They just ask the patients a few serious questions during PAC and ask them to put their signature in the consent form.In fact they become restless and uncomfortable when the patient starts asking questions.On the contrary some physicians try to over exaggerate the complications and procedural details to make the patients feel that he will be doing something dangerous and great for patient's sake.Both of these are harmful practices as either the patient is unaware of the procedure or he will be too much nervous and tensed to face the situation.Pull out your ego and reassure the patient,explain about the possible complications, and gain the confidence and trust of patients and relatives.

It doesnt matter whether the physician is  an egoist or not,but denying treatment or harming patient's health on account of his ego, is strictly against medical ethics. One should identify his limitations and weakness as human beings and should have a helping mentality.He should be open to his colleagues, help them out in cases of difficulties, hear to them and should be willing to discuss with them.As we learn through mistakes,suppress your ego towards those who point out your mistakes. Since most of the procedures in anaesthesia are "blind techniques" patient, positional or technical variations may affect them. Luck also plays.So dont be hesitant to hand over the procedure to a senior colleague or ask your junior to try out with a different hand, when somebody fails in  few attempts.The ultimate aim of ego less practise is Safe and Quality patient care.

Ego is like your branded clothes.Its is important that you have it,but not necessary to show it always.You may have much of an ego in anesthesia because you aren't respected by the patient's relatives, you are not paid like surgeons and you have to work behind the curtains where no one understands how serious and risky is your job.But you may remember that Ego can be a great  motivator and destroyer as well.Those who are successful in life know how to control their ego.No one is superior to others and the medical law states "You know only a fraction of what you are supposed to know" and no one can learn everything in medicine.Say good bye to ego and be part of the team work for better and quality patient care through dynamic decision making and individual participation which makes the practice of anaesthesia more meaningful and sublime.

Still interested to read on? visit the following links.

1.http://www.dailymail.co.uk/news/article-2312847/Hospital-consultant-Jarrod-Homer-loses-tooth-fight-anaesthetist-Kamran-Abbas-Manchester-Royal-Infirmary.html

2.http://drsvenkatesan.wordpress.com/tag/doctors-ego/

OBSTRUCTIVE SLEEP APNEA SYNDROME AND SLEEPLESS ANAESTHETIST!

 

Which is the most common form of apnea? Perhaps the most common apnea,which causes lot of physiological disturbances due to anatomical alteration of body size or tissues, leading to serious pathological changes in body systems, is Obstructive Sleep apnea.Obstructive sleep apnea syndrome occurs when there are repeated episodes of complete or partial blockage of the upper airway during sleep.

During  episodes of sleep apnea,the diaphragm and respiratory muscles including the accessory muscles work hard to overcome the obstruction and the passage of air through the obstructed airway causes noisy breathing or snoring..Thus instead of getting a sound sleep for the victim, he falls into a "SOUND" sleep disturbing his partner or others.Thus due to obstruction the patient gradually stops his respiration momentarily and breathing usually resumes with a loud gasp,snort,or body jerk.These episodes can interfere with sound sleep[1]The physiological and pathological changes occurring in internal organs are due to relative deficiency of oxygen and retention of carbon dioxide. There is accumulating evidence that OSA is being considered as an independent risk factor for hypertension,diabetes mellitus,cardiovascular diseases and stroke, leading to increased cardiometabolic morbidity and mortality.

Definition:  

An apnoea is defined as the complete cessation of airflow for at least 10 sec.There three types of apnoea found clinically are obstructive,central and mixed.The frequency of apnoeas and hypopnoeas hourly is used to assess the severity of the OSAHS and is called the apnoea/hypopnoea index (AHI) or the respiratory disturbance index (RDI)According to the American Academy of SleepMedicine  recommendations,OSA is defined with AHI>5, and it is classified as mild OSA with AHI of 5 to 15;moderate OSA with AHI of 16 to 30; and severe OSA with AHI > 30.[2]

Respiratory effort–related arousal (RERA) is an event characterized by increasing respiratory effort for 10 seconds or longer leading to an arousal from sleep but one that does not fulfill the criteria for a hypopnea or apnea. The criterion standard to measure RERAs is esophageal manometry[12]

Symptoms:

Adults:
    Snoring
    Daytime sleepiness or fatigue
    Headaches on awakening in the morning.
    Poor concentration,Loss of memory, Depression,or Mental irritability
    Dry mouth or sore throat upon awakening
    Night perspiration
    Restlessness during sleep
    Sexual dysfunction
    Sudden awakenings from sleep with a sensation of gasping or choking

  In Children
    Drooling and often choking
    Excessive perspiration at night
    In drawing of the ribs while inspiration
    Learning and behavioral disorders
    Poor attention sleepiness and poor school performance
    Snoring
    Teeth grinding
    Restlessness during sleep
    Pauses or absence, cheyne stokes pattern of breathing
    Unusual sleeping positions, such as sleeping on the hands and knees, or with the neck hyperextended.

Causes of obstruction:

In adults the causes for obstruction include thick or large necks.They may have a relatively smaller airway with edentulous soft tissues where patency is maintained by active contractions of pharyngeal dilators which are depressed with sleep, alcohol, or sedatives.Babies and small children may have sleep apnea that is caused by swollen tonsils or hypertrophy of the uvula and soft palate.A larger than average tongue can also block the airway in many people as well as a deviated septum in the nose.

Risk factors:  

Age: Prevalence is high in the middle aged reaching a plateau by around 60 years.[3].Older people with OSAS are found have increased fat deposition in parapharyngeal area, lengthening of the soft palate,and
changes in body structures surrounding the pharynx.
Sex: OSAS is more common in men than women.
Obesity: BMI >30,Neck circumference more than 44 cm.The upper airway obstruction during sleep is attributed to increasing adiposity around the pharynx and body. Central obesity has been associated with reduction in lung volume,which leads to a loss of caudal traction on the upper airway, and hence, an increase in pharyngeal collapsibility.[4]
Family history and genetic predisposition: More common in first degree relatives of those with OSAS.
Craniofacial anomalies:Congenital or acquired alterations in the upper airway have been identified as risk factors for developing OSAS.Trauma, congenital anomalies like pierre robins syndrome.
Smoking and alcohol consumption: Cigarette smoking and alcohol have been shown to be risk factors for OSAS.Smoking induced airway inflammation is thought to be the causative factor while alcohol relaxes upper airway dilator muscles, increases upper airway resistance and may induce OSA in susceptible subjects

Pathophysiology:

People with sleep apnoea have a smaller pharyngeal airway than do matched controls.Also there will be alteration in bony structure and soft tissue surrounding the lumen.Due to the anatomical compromise,OSAS patients are susceptible to pharyngeal collapse during sleep or anaesthesia.Patients with OSA have increased pharyngeal dilator muscle activity which keep the airway patent during awake.Healthy individuals experience a loss of upper airway muscle tone at sleep onset (alpha-theta transition in the electroencephalogram) and experience some degree of breathing instability, an individual reliant on muscle tone due to an anatomical vulnerability will be particularly susceptible to apnoea when the dilator effect of pharyngeal muscles are lost.[5]Although pharyngeal dilator muscle responsiveness is likely impaired during NREM and REM sleep[6], the genioglossus can respond to both sustained mechanoreceptive (negative pressure) and chemo receptive stimuli, particularly when combined stimuli are present[7] The physiological response to this effect is a raise in CO2 due to respiratory obstruction and raise in negative intrathoracic pressure.The intrathoracic pressure appears to be a potent stimulus for genioglossal activation  and maintaining airway patency.Elevated endexpiratory lung volume may lead to increased caudal traction on the diaphragm which may keep the airway stable and patent.

Thus the sequence is airway obstruction, hypoxia, increase CO2,increased EMG activity causing genioglossus and other pharyngeal muscle activation,negative intrathoracic pressure and chemoreceptor activation causing arousal.The pharyngeal muscle patency may be restored even before arousal.The mechanism of arousal is thought to be activation of parabranchial nucleus of pons due to neurohumoral activation by hypoxia and hypercarbia.A deeper stage of sleep, central nervous system depressants, prior sleep fragmentation, and the presence of obstructive sleep apnea (OSA) have been observed to increase the arousal threshold to airway occlusion.[8]

 

Systemic effects:

Neurobehavioral and social:  Excessive daytime sleepiness, impaired vigilance, mood disturbances, and cognitive dysfunctions are the features of OSAHS. The sleepiness may interfere with efficiency in work and may worsen interpersonal and social relationships. The sleepiness may be  dangerous when driving and causes increase in road traffic accidents or  injuries when operating machinery. Partners of patients with OSAS experience poor sleep,and will be the first one who takes the patient to a doctor for evaluation of his sleep disorder.[9]

Cardiovascular: The intermittent hypoxia, Chronic hypercarbia, frequent negative intrathoracic pressure variations,and sleep disturbance and arousals lead to increase in blood pressure and lead on to sustained hypertension via chronically heightened sympathetic nervous system activity and arterial baroreceptor dysfunction.Myocardial infarctions are also common.The cerebrovascular system is also affected making the patient prone for CVAs and intracranial hypertension.Cardiac arrhythmias and cor pulmonale are commoner in these patients.[9]

Diabetes mellitus: OSAS is an independent risk factor for development of  Diabetes,associated with insulin resistance,Obesity further increase the risk. Obesity associated changes in pharyngeal muscles may also contribute to OSAS.[9] 

Liver: Hepatic dysfunction marked by  raised liver enzymes,fatty liver and fibrosis are also associated with OSAS [9]

Perioperative and postoperative considerations:

Patients with OSAHS may have increased perioperative risks.There is frequent prevalence of undiagnosed obstructive sleep apnea.Loss of control over airway, inability to mask ventilate, difficulty in intubation, intraoperative hypoxemia,abnormal raise in ETCO2 causing arrhythmias, intraoperative hypertension etc. are the problems anaesthesiologists face.The patients should be taken to OT adequately fasted and after acid aspiration prophylaxis.Fastrach LMA and fiberoptic bronchoscope are ideal for intubation and must be kept ready.It is advised to control the ventilations to match preoperative SPO2 and ETCO2.Spontaneous ventilations with LMA may cause hypoventilation and hypercarbia due to high rate of metabolism and increased thoracic mass.Whenever possible regional anaesthetic techniques or nerve blocks may be tried..Pre operative CPAP may be continued intra operatively also and extubation should be done when neuromuscular block is completely reversed and once the patient is fully conscious,communicative and able to generate adequate tidal volume.Semi sitting position or ramped position may be used to aid extubation, and the ETT may be pulled over a bougie or exchange catheter. Post operative respiratory depression is common and repetitive apnea may occur if the patient is somnolent.Monitor ETCO2 and SPO2 post operatively and if needed RBS and ABG may be performed frequently.Caution should be exercised when prescribing narcotics for post operative pain relief.

Diagnosis:     

 1)A sleep test or polysomnogram( PSG): may be used for confirmation.Sleep testing is performed in a sleep lab and is supervised by a trained technologist. The test will measure various body functions, including:

    Air flow
    Blood oxygen levels
    Breathing patterns
    Electrical activity of the brain
    Eye movements
    Heart rate
    Muscle activity
For more information about polysomnography visit:  http://classes.kumc.edu/cahe/respcared/cybercas/sleepapnea/trenpoly.html

 

                                                          The plysomnograph, Ref:[10]

                                                               UARS: upper airway resistance syndrome

2)Nocturnal sleep pulse oximetry:  The oxygen desaturation index (ODI) measures the mean number of episodes of oxygen desaturation per estimated sleep hour and is sometimes used as a surrogate for the
AHI.
3)Epworth sleepiness scale (ESS):  Used to measure excessive day time sleepiness[10].

Treatment:

1) Continuous positive airway pressure: 
Continuous positive airway pressure:(CPAP) is the preferred treatment of choice for OSAHS.[9] The required CPAP is titrated to a level that eliminates snoring, usually 5–20 cm Hg. A randomized placebo-controlled trial showed that CPAP can improve breathing during sleep, sleep quality, blood pressure,vigilance, cognition, and driving ability as well as mood and quality of life in patients with OSAHS.The drug Modafinil is found to be effective in treating OSAS along with CPAP.It was also observed that CPAP therapy improves hypertension usually by about 10mmHg.[11]

2) Mandibular repositioning splint:

Mandibular repositioning splints (MRSs)or oral devices work by holding lower jaw and the tongue forward, thereby increasing the pharyngeal airway.

3) Surgery:

Bariatric surgery is useful and often curative in patients with morbid obesity. Tonsillectomy is highly effective in children. Tracheostomy carries high morbidity and  may be curative but rarely used.[9]. Jaw advancement surgery, especially maxilla-mandibular osteotomy, is effective in patients with retrognathia.Somnoplasty uses radiofrequency energy to tighten the soft palate at the back of the throat.
Nasal surgery may be considered for correction of nasal obstructions, such as a deviated septum.

Uvulopalatopharyngoplasty: A procedure that  increases the width of the airway at the throat by removing soft tissue in the back of the throat and palate.

 Mandibular/maxillary advancement surgery : The procedure involves surgically moving the jaw bone and face bones forward to make more room in the back of the throat, done in severe cases of OSAS and in patient with facial anomalies.
   

Ref:

1). http://www.webmd.com/sleep-disorders
2).AASM,Sleep 1999; 21 : 667-89.
3).Young T, Skatrud J. Peppard PE. Risk factors for obstructive sleep apnea in adults. JAMA 2004; 291 : 2013-6.
4).Schwartz AR, Patil SP, Laffan AM, Polotsky V, Schneider H,Smith PL. Obesity and obstructive sleep apnea – pathogenic mechanisms and therapeutic approaches. Proc Am Thorac Soc 2008; 5 : 185-92.
5). Pathophysiology & genetics of obstructive sleep apnoea,Lisa Campana, Danny J. Eckert, Sanjay R. Patel† & Atul Malhotra.Indian J Med Res 131, February 2010, pp 176-187
6).Shea S, Edwards J, White D. Effect of wake-sleep transitions and rapid eye movement sleep on pharyngeal muscle responseto negative pressure in humans. J Physiol 1999; 520 : 897-908.
7).Stanchina ML, Malhotra A, Fogel RB, Ayas N, Edwards JK,Schory K, et al. Genioglossus muscle responsiveness to chemical and mechanical stimuli during non-rapid eye movement sleep.
Am J Respir Crit Care Med 2002; 165 : 945-9.
8).Respiratory arousal from sleep: mechanisms and significance.Berry RB, Bleason, Department of Medicine, Long Beach VA Medical Center, CA, 90822, USA.Sleep1997 Aug;20(8):654-75.
9). GC Mbata and JC Chukwuka1,Obstructive Sleep Apnea Hypopnea Syndrome Ann Med Health Sci Res. 2012 Jan-Jun; 2(1): 74–77.
10).www.sbu.se/upload/Publikationer/Content0/1/somnapne_fulltext.pdf
11)Shiomi T, Sasanabe R, Ohtake K, et al. Cardiovascular complications,Obesity-induced hypertension and obesity heart failure accompanying obstructive sleep apnea. Journal of the Japanese Society of Internal Medicine. 2004;93(6):1114–1119.
12)http://emedicine.medscape.com/article/295807-overview
Image courtesy:
1.Image header :evelyngarone.wordpress.com 
2. Image on diagnostic criteria and pathophysiology from Advances in Diagnosis and Treatment of Sleep Apnea Syndrome in Japan JMAJ 52(4): 224–230, 2009,Toshiaki and Ryujiro. 
3.The multicolour circular flow chart..http://www.dentonsleepdisorderlab.com/obstructive-sleep-apnea.html

10 COMMON 'PROCEDURAL BASICS' ANAESTHESIOLOGISTS MAY OVERLOOK!

“To err is human;to forgive,divine.”Remembering the famous poetry quote[1] by Alexander Pope (1688-1744).This means any human can make a mistake,so we should try to forgive them, just as,God said to show divine mercy to sinners and forgive them.Apart from medication error and faulty techniques, anaesthesiologists rarely make serious mistakes and any such mistake,if done may jeopardize the patient's life.It is usual that anaesthesiologists forget to observe some basic procedural steps,which may lead to technical difficulties but usually the situation is overcome by timely intervention or by modifying the technique.Here are some situations, where an anaesthesiologist may encounter difficulties during his routine anaesthesia practise when they fail to observe the basics.

1)The importance of sniffing position with pillow under occiput:

The standard procedure for endotracheal intubation consists of keeping the head in sniffing position supported by pillow under head.  Successful tracheal intubation is achieved by obtaining a good glottic view,which requires alignment of three optical axes corresponding to the oral, pharyngeal and laryngeal planes. Extension at the atlanto occipital joint together with a head elevation( moderate head elevation 5–10 cm above the surgical table) keeps the perfect axis for an easy intubation[2]Infants may need a small towel roll under the "shoulders" to align the head.Obese patients [3]elevated head-up position or "ramp"position is used. In this position, the shoulders are elevated with several pads, the head and neck are extended, and the external auditory meatus is in line with the sternal notch.Most the difficult airways arise due to defective positioning.

          figure 1

                                                     figure 2

2)Bag and mask ventilation without oral airway and intubation without applying cricoid pressure.

One 9 year old boy with respiratory distress was admitted to A and E following ARDS due to severe sepsis.The child was conscious but drowsy and dropping saturation. The anaesthesiologist was called in for intubation and he continued with initial bag and mask ventilation to maintain the saturation while preparing for intubation.An airway was not used and the air pumped into his lungs negotiated its way to stomach due to partial airway obstruction. While he did laryngoscopy, due to gag reflex he regurgitated and immediately aspirated. Further attempts to maintain saturation following intubation were not successful. Drowsy semiconscious patients with weak gag reflex may tolerate oral airway and definitely tolerate nasal airway which helps to direct the air into the lungs following ambu bag ventilation.[4].The basic rule states application of cricoid pressure with head down position will prevent aspiration.(application of cricoid pressure and its effectiveness is questioned and many controversies exist, but was found very useful practically)


















3)Intubation using a bougie in difficult airway.
Grades 2 and 3 glottic view may be managed by intubation over a bougie.Following laryngoscopy insert bougie into the glottis and then "rail road"the ETT over the bougie.The basic rule here is "dont remove the laryngoscope before railroading". Once you remove the scope after inserting bougie the epiglottis and pharyngeal soft tissues may come their way between the ETT and the bougie and cause intubation failure.Ask the assistant to pass the ETT over the bougie while the anaesthetist keeps the epiglottis elevated with his laryngoscope with one hand and stabilising the bougie with the other hand.

4)Removal of a Laryngeal mask airway.
Patients on spontaneous ventilation under LMA anaesthesia,it is advisable to remove the LMA in deep anaesthetic plane itself.If you wait till the patient is fully conscious,chance of biting the airway tube by patient is high which leads to total airway occlusion and any attempt to remove an LMA in this situation can cause damage to the LMA, laryngospasm or regurgitation by pharyngeal stimulation[5].The ideal sequence of removing LMA seems....remove in deep plane then cut down gases,insert oral or nasal airway,keep mask, turn head to one side, allow patient to recover by inhaling 100% oxygen.

5)Treating laryngospasm during recovery.
The treatment should be immediate,prompt and aggressive[6].Delay in treating laryngospasm may lead to serious morbidity.IPPV with 100% to break off the spasm is widely followed as the first line of management but there should not be any delay in administering suxamethonium.The most feared complications are hypoxia and negative pressure pulmonary edema.

6)Exsanguinate before IVRA.
Complete exsanguination of the upper limb is advocated before IVRA.Failure of proper exsanguination leads venous oozing during the procedure causing unsatisfactory operating conditions.Poor diffusion of the drug leads to 'patchy" anaesthesia or total failure of anaesthesia.The use of an esmarch or similar bandage is stressed.

7)Extubating a difficult airway.There are many gadgets available to deal with a difficult airway.With the introduction of fastrach LMA and fiberoptic bronchoscope, the success rate of intubation is high.Following ICU admission or surgical procedure many anaesthesiologists fail to observe the basic rule "while extubating a difficult airway take the same precaution and keep ready the same gadgets you used to intubate the case, since extubation failure or post extubation complications may necessitate immediate reintubation". Always use a guide wire or bougie over which the ETT is pulled out (extubation over bougie)and observe the vocal cord behaviour during extubation.

8)Testing loss of resistance. While testing for loss of resistance during epidural anaesthesia always use saline instead of air to avoid complications like pneumocephalus[7], spinal cord and nerve root compression, retroperitoneal air, subcutaneous emphysema, and venous air embolism[8] Alternatively saline with an air bubble technique also seems to be appropriate.

                                                                      Performing the LOR by saline, from NYSORA

9)Nasal intubation in pediatrics. Extreme caution should be taken while performing a nasal intubation in pediatric age group and any difficulty in ventilation should alert the anaesthetist of possibility of occlusion of the tip of  ETT with a piece of adenoid tissue carried away in it. Any incidence of difficulty in ventilation, high airway pressure,abnormal tracing of capnogram or fall in saturation following nasal intubation in children,the anaesthetist should not hesitate to remove the ETT immediately and proceed with mask ventilation and oral intubation. Never attempt to overcome the resistance by forced ventilatory attempts or by passing catheters into ETT..[9][10]The obstruction by adenoid is usually distal to murphy's eye and other common causes for the obstruction are kinking of ETT and severe bronchospasm following intubation.

10)Uncover during PAC!The last but not the least, make a detailed physical examination during PAC.It was found on many occasions that gross physical deformities were overlooked by anaesthetists due to lack of proper exposure of body parts.Such deformities include pectus excavatum, pectus carinatum,scoliosis, thyroid swellings and other congenital abnormalities,.All these situations may lead to devastating intra operative complications.

Ref:
1)http://www.quotecounterquote.com/2010/12/to-err-is-human-to-forgive-divine.html
2)http://www.anesthesia-analgesia.org/content/early/2011/05/18/ANE.0b013e31821c7e9c.full.pdf
3)http://www.anesthesia-analgesia.org/content/102/5/1592.1.full
4)http://www.acep.org/Clinical---Practice-Management/Focus-On---Bag-Valve-Mask-Ventilation/
5)http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD007082/pdf
6) http://www.respond2articles.com/ANA/forums/thread/1096.aspx
7)https://www.aana.com/newsandjournal/Documents/p449-453.pdf
8)http://www.ncbi.nlm.nih.gov/pubmed/9010941
9)http://www.cas.ca/English/Page/Files/657_1344758.pdf
10)http://www.thefreelibrary.com/Nasotracheal+tube+occlusion+from+adenoid+trauma.-a0188739844

POST DURAL PUNCTURE HEADACHE,A NEVER ENDING STORY!

“Toward the evening I was forced to take to bed and remained there for nine days, because all the manifestations recurred as soon as I got up. At midnight a violent headache set in that quickly became insupportable.” This was the first experience of spinal headache in the history and was experienced by the great August Bier in 1898,when he suffered severe headache after spinal anesthesia given to him  by his colleague,on his request.The headache follows any diagnostic or therapeutic procedure of the spinal or epidural space.


According to Carrie and Collins [1]  post dural puncture headache (PDPH) is "a headache occurring after dural puncture and has a significant effect on the patient's post operative well being i.e. headache which is not only postural but also continues for more than 24 hours at any level of intensity or so severe at any time that the patient is unable to maintain upright position.According to the International Headache Society, the criteria for PDPH [2] include a headache that develops less than seven days after a spinal puncture, occurs or worsens less than fifteen minutes after assuming the upright position, and improves less than thirty minutes in the recumbent position with at least one of the following (neck stiffness, tinnitus, hypacusia, photophobia, and nausea). The headache should disappear within fourteen days after a spinal puncture; if it persists, it is called a CSF fistula headache.The incidence[3] of PDPH is estimated to be between 30-50% following diagnostic or therapeutic lumbar puncture,0-5% following spinal anaesthesia and up to 81% following accidental dural puncture during epidural insertion in the pregnant woman.Other than spinal anaesthesia the procedures leading to PDPH include,diagnostic lumbar puncture( where a big sized needle is used) labour analgesia with accidental dural puncture and therapeutic epidural steroid injections.

Do the needle size and type matters? Of course, researchers of the past 100 years have found that there is a definite relationship between the incidence of  PDPH and needle size. Reducing the size of the spinal needle has made a significant impact on the incidence of post‐spinal headache. The incidence[4] is  approx 40% with a 22G needle; 25% with a 25G needle; 2%–12% with a 26G Quincke needle; and less than 2% with a 29G needle. With needles of 29G or smaller, the technical difficulties may lead onto a failure of the procedure and multiple attempts may be required causing multiple dural puncture which in fact increase the incidence.Pencil point whitacre needles are now preferred.If the needle bevel is oriented parallel to the nerve fibres during spinal anaesthesia the incidence can be lowered further.PDPH is rare in children owing to their low CSF pressure[5]

Characteristic features of head ache: Ninety per cent of headaches will occur within 3 days of the procedure,[6]and 66% start within the first 48 h.[7] Rarely, the headache develops between 5 and 14 days after the procedure.The head ache is commonly distributed over the frontal and occipital areas radiating to the neck and shoulders and sometimes the temporal, vertex and nuchal areas also may be affected.Neck stiffness may be present. The pain is exacerbated by movements of the head, standing position and relieved by supine position.Other symptoms include nausea,vertigo,tinnitus,visual disturbances and rarely cranial nerve palsies.The headache is usually relieved in seven days but cases were reported where it lasted upto 3 months.The cause for the head ache is CSF leak leading to intracranial hypotension

Diagnosis: Mainly by clinical features and history of possible dural puncture.Additionally a diagnostic CSF tap may show, a  low CSF opening pressure, minimally raised CSF protein, and a rise in CSF lymphocyte count.The  MRI may demonstrate diffuse dural enhancement, with evidence of a sagging brain or descent of the brain.[8] Cisternography or CT myelography may be used for diagnosing a CSF leak.Untreated cases may develop intracranial hematoma due to rupture of bridging veins following intracranial hypotension.

Treatment: 

1) Bed rest: No use at all [9] but along with other measures very effective in reducing headache.

2) Simple analgesics: Paracetamol and other NSAIDs for mild pain.

3) Posture: Supine position helps to maintain the CSF pressure and prone position increases intra abdominal pressure and  the CSF pressure and gives instantaneous relief. However prone position may not be comfortable for the patient.Supine position helps to avoid complications like intracranial hemorrhage and seizures due to low CSF pressure.

4) Abdominal binders: Should be tight enough to increase the intra abdominal pressure.

5) Caffeine : Caffeine is a CNS stimulant and cerebral vasoconstrictor.The recommended dose is 300-500 mg of oral caffeine once or twice in a day[10] [11]It is assumed that caffeine acts through vasoconstriction of dilated cerebral vessels.Caffeine is associated with some adverse events like cardiac arrhythmias and maternal seizures and necessary precaution may be taken. High doses of the drug may reach the baby through breast milk and can cause neonatal irritability[12]

6) Sumatriptan:  Sumatriptan is a 5‐HT_1D receptor agonist that promotes cerebral vasoconstriction,acts in a similar way to caffeine. It increases the cerebral vascular tone.

7) Synthetic ACTH: was first reported to be effective for treating PDPH in the 1990s. Postulated
mechanisms include CSF retention through increased mineralocorticoid mediated sodium reabsorption,
and a direct analgesic effect via its glucocorticoid activity[12]. A randomised controlled trial in 2004 found no effect of a single intramuscular injection of Synacthen compared with an intramuscular injection of normal saline.ACTH has been administered as an infusion [13] 1.5 microgram per kilogram. 

8) Desmopressin(DDAVP): injection intramuscularly  before spinal injection has also proven to be effective but more reasearch is required to prove its efficacy.

9)Adequate hydration:  was found to be helpful but overhydration must be avoided. 

10)Epidural Blood Patch: Perhaps the most effective treatment for PDPH is epidural blood patch(EBP).the concept of EBP has developed following the observation that bloody taps were associated with reduced incidence of headache.The first epidural blood patch was performed in 1960 by theAmerican  surgeon, Dr James Gormley.The mechanism is that once blood is introduced into the epidural space it coagulates and form a seal occluding the puncture site preventing further CSF leak.The procedure is associated with high success rate and low incidence of complications and has become the standard mode of treatment for PDPH.Before initiating the treatment one has to look for the contraindications like coagulopathy, local infections, fever or patient refusal.A sample of the patient's blood may be sent to lab for culture[14].If symptoms of PDPH persist after 24-48 hours,or the headache is disabling,consider an epidural blood patch. 

 Guidelines[15] for placement of epidural blood patch (St.George Hospital, London)

The procedure must be carried out in theatre. Two anaesthetists are required, one of whom should be a consultant.
1. Written, informed consent should be obtained from the woman following a careful explanation of the procedure. The discussion should also include the chances of success, significant side effects and the possibility of requiring a second blood patch(approximately 1 in 5).
2. The epidural space is located with a Tuohy needle, by the first anaesthetist, at the level of the supposed dural puncture, or an intervertebral space above or below. CSF may be present in the epidural space. 20 –  30 ml of the patient’s blood (provided by the second anaesthetist) is then injected into the epidural space over 30 – 60 seconds. Dull, lower back pain may limit the volume injected, although pausing for a few seconds or slowing the rate of injection may allow the full amount to be injected.
3. The second anaesthetist is responsible for drawing blood from the patient. As with the epidural, vene puncture must also be carried out using a full aseptic technique. After cleaning and draping the skin of the antecubital fossa, the skin should be anaesthetized with local anaesthetic prior to the insertion of a 14 or 16 gauge cannula. This should be done when the epidural needle is sited.
4. It has previously been thought that samples of the blood should routinely be sent for culture. This is an area of much controversy, and is backed up by little evidence,however until we have a definitive answer to this question it would seem prudent to continue to send blood for screening purposes. There is no evidence for the routine use of prophylactic antibiotics following blood patch.
5. The epidural blood patch should be carried out in the Obstetric theatre. Immediately following the procedure the patient should be taken to the recovery area for close observation. The patient is encouraged to lie still for one to two hours. After this time she can be transferred to the ward where she should be encouraged to walk.
6. It is important that the patient has repeated clinical assessment while an inpatient,although she may well go home the same day. Prior to going home, advice must be given regarding the need to contact labour ward or present to an Accident and Emergency department in the case of any complications. Specifically patients should be told about presenting features of cauda equina syndrome and epidural abscess.Where
possible written information should also be given. " During placing of EPB thus patient always should be asked about any acute occurrence of new pain, radiating pain and sharp shooting pain. Thus in EPB always a test dose of 2-3 ml of blood should be injected and patient should be evaluated. The total volume should be injected in increments of 2-3 mls".

 Mechanism of action of  EBP: After injection the patient should remain supine and immobile for
30 minutes to 2 hours to allow the blood to form a clot.Once injected the blood is distributed caudally and cephalad regardless of the direction of the bevel of the Tuohy needle. The blood also finds its distribution circumferentially around to the anterior epidural space. This has been proved [16] by using radiolabelled red cells or by MRI.There is evidence of  thecal space compression and escape of blood through the intervertebral foramina and into the paravertebral space.The injected blood spreads up about six spinal segments cephalad and three segments caudad.The procoagulat property of CSF accelerates clotting of blood and the puncture site is sealed followed by an immediate relief of headache.At 7–13 h, there is clot resolution leaving a thick layer of mature clot over the dorsal part of the thecal sac.[17]

Efficacy of blood patch: EBP is likely to be most effective if performed at least 24 hours after the onset of PDPH.The success rate varies between 75-90% and about 40% patients may need second EBP.The technique is safe and the rare transient complications include radiculopathy,backache, neckache and bradycardia.Major complications are rare,and may include meningitis, subdural haematoma, seizures, arachnoiditis, spastic paraparesis, dural puncture,cauda equina syndrome etc.If an epidural blood patch fails to relieve a PDPH, it is advisable to consider radiological imaging of the head to exclude other pathology prior to repeating the blood patch.

Prophylactic blood patch: The beautiful explanation in this regard is by Dr Nicola Jane Campbell FRCA, Effective management of post dural puncture headache  Anaesthesia tutorial of the week  181, 31st may 2010.He says,
A potentially attractive option in the face of a recognised dural puncture with a Tuohy needle is to resite the epidural so that a prophylactic epidural blood patch (PEBP) can be provided in the hope of preventing a subsequent PDPH. The popularity of this technique has diminished recently for a number of reasons including the limited evidence that PEBP reduces the requirement for a therapeutic EBP, the increasing use of intrathecal catheter placement following dural puncture which may itself reduce the risk of subsequent PDPH and the recognition that some dural punctures don’t result in a PDPH and many PDPHs do not require a therapeutic EBP. Administering a PEBP to patients following duralpuncture may therefore expose these patients to an unnecessary procedure with associated risks.
Epidural saline and Dextran: theoretically a suitable alternative to EBP and thought to be safe as they are sterile solutions.These techniques are very useful in Jehovah witnesses patients or patient with bacteremia and HIV infection .They increase the CSF pressure by mass effect but formation of a coagulum and subsequent sealing effect over the dura are doubtful.Regimens include (i) 1.0–1.5 litre of epidural Hartmanns solution over 24 h, starting on the first day after dural puncture;[18] (ii) up to 35 ml h^–1 of epidural saline or Hartmanns solution for 24–48 h, or after development of the headache; (iii) a single 30 ml bolus of epidural saline after development of headache;[19] and (iv) 10–120 ml of saline injected as a bolus via the caudal epidural space.The tamponade effect of epidural dextran is also transient and similar to saline offering no advantage over saline.In neither of these an aseptic inflammatory response over the dura was found.

Epidural Morphine: Administration of epidural morphine soon after inadvertent dural puncture as prophylactic measure to prevent PDPH has been advocated by  many authors but evidence lack due to absence of large controlled trials.

Fibrin glue: As an alternetive to blood patch fibrin glue injection into the epidural space was found to be helpful..The procedure may be done blindly or by CT guided percutaneous injection.The failure rates are high.  Chance of development of aseptic meningitis makes the procedure less acceptable to many. 

Intrathecal catheters:An alternative method of managing ADP by passing an epidural catheter through the needle into the subarachnoid space was described by Cohen in 1989. Since then, several studies have claimed a reduction in incidence of PDPH if the epidural catheter is inserted intrathecally at the time of dural puncture and removed after at least 24 h. Injection of a 10 ml bolus of normal saline into the intrathecal catheter before its removal further reduced the incidence of PDPH. [20]It was postulated that placement of
a spinal catheter through the perforation may provoke an inflammatory reaction that will seal the hole. However, neurological complications, such as cauda equina syndrome and infection, should preclude the use of intrathecal catheters and keeping the catheter for more than 24 hours is also not advocated

Surgical closure: Surgical closure of the dural perforation is the last resort to treatment

Preventing PDPH; Preventive measures like smaller needle size, shape of needles and direction of needle bevel in relation to dural fibers, should always be considered.For spinal blocks, pencil point needles of 25 G or smaller should be used, especially in the obstetric population.While performing Epidural anaesthesia Loss of resistance to saline performed with continuous pressure on the syringe plunger may have the effect of
moving the dura anteriorly as the needle approaches thereby reducing the likelihood of dural puncture
compared with an intermittent pressure technique with air.Other precautions should include ensuring an optimal patient position, slow controlled advancement of the needle and limiting patient movement during the procedure by using adequate local anaesthetic infiltration[12].When there is difficulty  use of ultrasound guidance for epidural placement may be considered.

Differential diagnoses: for PDPH:Tension Headache,Migraine Headache, Caffeine Withdrawal, Lactation Headache, Hypertension, Pneumocephaelus, Meningitis, Subarchnoid Heamorrahge, Spontaneous Intracranial Hypotension and eclampsia.

PDPH is the most distressing experience for post operative patient and can lead on to significant morbidity and death..Apart from increasing the duration of hospitalisation, it can cause  auditory and visual disturbances, nausea, vomiting ,cranial nerve palsy and intracranial hemorrhage due to low CSF pressure.The treatment should be aggressive with conservative methods initially and in severe and resistant cases with CNS involvement  EBP may be tried..Mostly the headache is benign and will be resolved spontaneously in 5-7 days

A current review about PDPH by Steve Schwalbe, MD is found to be interesting in this context..http://www.soap.org/media/newsletters/fall2000/pathophysiology_management.htm

Ref:
1) Carrie Less, Collins PD. 29 guage spinal needle. Br J Anesth 1991; 66 :145-6.
2) R. W. Evans, “Complications of lumbar puncture,” Neurologic Clinics, vol. 16, no. 1, pp. 83–105, 1998
3)http://www.frca.co.uk/Documents/181%20Post%20dural%20puncture%20headache.pdf
4) Barker P. Headache after dural puncture. Anaesthesia 1989; 44: 696–7
5) Carbajal R, Simon N, Olivier‐Martin M. Post‐lumbar puncture headache in children. Treatment with epidural autologous blood (blood patch). Arch Pediatr 1998; 5: 149–52
6) Reynolds F. Dural puncture and headache. Br Med J 1993; 306: 874–6
7) Leibold RA, Yealy DM, Coppola M, Cantees KK. Post‐dural‐puncture headache: characteristics, management, and prevention. Ann Emerg Med 1993; 22: 1863–70
8) Mokri B, Parisi JE, Scheithauer BW, Piepgras DG, Miller GM. Meningeal biopsy in intracranial hypotension: meningeal enhancement on MRI. Neurology 1995; 45: 1801–7
9) Spriggs DA, Burn DJ, French J, Cartlidge NE, Bates D. Is bed rest useful after diagnostic lumbar puncture? Postgrad Med J 1992; 68: 581–3
10) Sechzer PH. Post‐spinal anesthesia headache treated with caffeine. Evaluation with demand method. Part 2. Current Therapeutic Research, clinical and experimental 1979; 26: 440–8
11) http://www.update-software.com/BCP/WileyPDF/EN/CD007887.pdf
12) Dr Nicola Jane Campbell FRCA, Effective management of post dural puncture headache  Anaesthesia tutorial of the week  181, 31st may 2010
13) Collier BB. Treatment for post‐dural puncture headache. Br J Anaesth 1994; 72: 366–7
14)Crawford JS. Experiences with epidural blood patch. Anaesthesia 1980; 35: 513–15.
15) http://www.oaa-anaes.ac.uk/assets/_managed/editor/File/Guidelines/PDPH/PDPH_diagnosis_management%20PDPH_Wendler_StGeorges.pdf
16) Szeinfeld M, Ihmeidan IH, Moser MM, Machado R, Klose KJ, Serafini AN. Epidural blood patch: evaluation of the volume and spread of blood injected into the epidural space. Anesthesiology 1986; 64: 820–2
17) D.K.Turnbull,D.B, shepherd,Post dural puncture headache, pathogenesis, prevention and treatment Br J Anaesth 2003; 91: 718–29
18) Crawford JS. The prevention of headache consequent upon dural puncture. Br J Anaesth 1972; 44: 598–600
19) Moir DD. Recent advances in pain relief in childbirth. II: regional anaesthesia. Br J Anaesth 1971; 43: 849–57
20) http://www.joacc.com/article.asp?issn=2249-4472;year=2011;volume=1;issue=2;spage=57;epage=66;aulast=Nath