ARTIFICIAL BLOOD, HOPE FOR THE FUTURE?

A sigh of relief, the tension is relieved as the gynaecologist took the baby out with great  difficulty through the incision. The  indication for caesarean section was severe fetal distress and the OT atmosphere has now turned pleasant as the paediatrician reported that the APGAR score is 9. The anaesthesiologist is busy preparing  oxytocin infusion and sedation.The patient who was given regional anaesthesia is now anxious to see her baby.But the enjoyment did not last long as the surgical team noted profuse bleeding with a flabby uterus not responding to ergometrine or oxytocin.A request for issuing blood was  sent to blood bank but the request was returned ,stating that the husband refused any kind of blood transfusion as he is a strict Jehovah's witness which he didn't mention at the time of taking the consent!

 Jehovah's witnesses, a fellowship of more than 1 million americans, object to the administration of blood in any form for any indication.This objection is based on "THE HOLY BIBLE"  Acts 15:28,29 which states "For it has seemed good to the Holy Spirit and to us to lay on you no greater burden than these requirements: that you abstain from what has been sacrificed to idols, and from blood, and from what has been strangled, and from sexual immorality. If you keep yourselves from these, you will do well. Farewell.” According to them blood removed from the body should be discarded "You should pour it upon the ground as water"  (Deuteronomy 12:24.)This makes pre operative blood conservation technique like preoperative phlebotomy and storage impractical

The search for an oxygen carrying blood substitute started with world war II as the military realized the difficulties of whole blood transport and storage.Subsequently several trials were made to bring out an ideal blood substitute using chemicals which can carry oxygen.
1)Perfluorocarbon compounds:Of the various substances that carry or facilitate the transport of oxygen the perfluorocarbons gave the most promising results.They were created by replacing H2 atoms of hydrocarbons with flurine. This was following the first real success in  "fluid breathing system" proposed by Leland Clark in 1966. He found that oxygen and carbondioxide are very much soluble in fluorocarbon liquids and can be used for artificial ventilation of the lungs which are immersed in these compounds where satisfactory oxygen uptake  and giving out of CO2 takes place by the alveoli through the liquid media, in the absence of external oxygen supply.He performed his experiment in anaesthetised rat where the animal is paralysed intubated and immersed in PF liquid.After bubbling oxygen through the liquid this is pumped into the animal's lungs and recirculated. Most of the animals kept in the fluid for upto an hour survived for several weaks. Subsequently trials were made in humans during war time.               Figure: Demonstrating a living mouse immersed  in  perfluorocarbon compound along with a goldfish.

• Fluosol-DA was the most notable compound among PFCs, regarded as a first generation PFC.It contained perfluorodecalin and perfluorotripropylamine emulsified with Pluronic F-68  It was approved by the FDA for use in percutaneous transluminal coronary angioplasty initially but was subsequently withdrawn(see below)
• They have high affinity for oxygen approximately 10-20 times greater than plasma.The  oxygen content of PFCs  is directly proportional to oxygen partial pressure and are most efficient as oxygen carriers at a partial pressure of more than 300mmHg, which limited their use, as patients needed high inspired oxygen concentration. A short intravascular half life, unstable at extreme temperatures, Low oxygen carrying capacity ,poor shelf life and adverse effects such as acute complement activation and disruption of pulmonary surfactant, all lead to their withdrawal  from the market. But still these compounds have found some place in "Liquid ventilation" of lungs in ARDS.