H1N1 PNEUMONIA, AN UPDATE

The outbreak of H1N1 influenza A virus infection was first detected in Mexico, in April 2009, with subsequent spread as pandemic to other countries .The diagnosis and management of H1N1 infection is of great concern to any health organisation so also its prevention. Patients having pneumonia  with prior symptoms of  H1N1 influenza, should be referred to intensive care units for further management, as prognosis is good except for the high risk patients.These high risk groups are

• Children younger than 5 years of age, but especially those younger than 2
• Individuals 65 years of age or older
• Pregnant women and women up to two weeks postpartum (including those who have had pregnancy loss)
• Individuals younger than 19 years of age who are receiving long-term aspirin therapy and who therefore might be at risk for Reye syndrome after influenza virus infection
• Individuals of any age with chronic medical conditions requiring ongoing medical care, including: chronic pulmonary disease,( including asthma) ,active malignancy  chronic renal insufficiency,chronic liver dise,diabetes mellitus,hemoglobinopathies such as sickle cell disease, immunosuppression, including HIV infection, immunoosuppressants, certain collagen vascular diseases, such as rheumatoid arthritis,antiphospholipid syndrome, etc
• Patients with inability to remove resp secretions due to inadequate cough reflex,  due to  spinal cord injury, neuromuscular diseases ,Children with metabolic diseases and Obesity are also cosidered under high risk. 

 
RECOMMENDATIONS

• Isolate all patients with respiratory signs suggestive of pneumonia
• Avoid use of fans as it causes air recirculation, normal icu air exhaust is enough
• Keep visitors to minimum
• Health care workers should wear, gloves, gown , FFP3 mask, eye protection as aerosol transmission is the major route of spread
• Hand hygiene
• Eye protection(goggles)

PROCEDURES  CAUSING INCREASED RISK OF TRANSMISSION BY AEROSOL

• Intubation and manual ventilation
• Tracheal suctioning
• Nasopharyngeal aspiration
• CPCR
• Bronchoscopy
• Autopsy procedures
• Nebulisation
• Nippv

DIAGNOSIS

• nasopharyngeal or throat swabs for viral culture or polymerase chain reaction

VENTILATION

• As far as possible consider non invasive ventilation, but intubation and ventilation may be considered if there is progressive increase in respiratory distress  and ABG is unsatisfactory.Following are the crieteria for invasive ventilation

1. Refractory hypoxemia,SpO2 < 90% on non-rebreathe mask @ 15L/min oxygen flow
2. Respiratory acidosis,pH < 7.2
3. Clinical evidence of impending respiratory failure,Respiratory rate > 40
4. Inability to protect or maintain airway
5. GCS <8

STRATEGY:

• Closed suctioning preferred
• Ventilatory strategies are similar to ARDS
• Consider inhaled nitric oxide and prone ventilation for better oxygenation
• High frequency oscillatory ventilation or ECMO should be considedered in refractory cases

ANTIVIRAL THERAPY

• H1N1 viruses are susceptible to neuramnidase inhibitors like osaltamivir and zanamivir(inhalation) but resistant to amantadine or rimantadine. Ideally treatment should start immediately to avoid viral replication but can be started at any stage of active  illness.The usual dosage in adults is 75 mg bid and 30-40mg bid for infants older than 1 year and children the dosage in critically ill is almost double than that used for influenza oseltamivir 150 mg bid through ryles tube may be used for 10 days. Dose adjustment required for creatinine clearance less than <30ml/mt.The recommended dose of zanamivir(above 5 yrs of age), is two inhalations(2 x 5mg) twice daily for 5 days.
• Rare but serious neuropsychiatric illness are reported as side effect for osaltam ivir.The adverse effects of  zanamivir include bronchospasm in asthmatics and gastrointestinal intolerance

SUPPORTIVE MANAGEMENT

• 20 percent of people require dialysis due to a/c renal failure
• Conservative fluid management advised
• Manage electrolyte abnormalities
• Secondary infection with streptococcal, staphylococcal and pneumococcal  bacteria  are common. appropriate culture and antibiotics administered.
• Control of hyperthermia by active cooling
• High flow oxygen therapy
• Low dose corticosteroid therapy is advantageous for treatment of septic shock, hypotension, or adrenal suppression but not recommended routinely(WHO)

Hypotension management shoul be aggressive and targeted

 • Systolic blood pressure < 90 mm Hg
 • Clinical evidence of shock:
 • Altered level of consciousness
 • Decreased urine output refractory to
 • Volume resuscitation
SOFA score  may be used for critical care assessment

Ref.links:
www.icmed.com/.../H1N1%20Influenza%20Management%20in%20the%20ICU%20gen...
http://www.utdol.com/home/content/topic.do?topicKey=pulm_inf/19054#

The United States Centers for Disease Control and Prevention
http://www.cdc.gov/h1n1flu/recommendations.htm