Comparative evaluation of haemodynamic parameters following two regimes of fractionated doses of levobupivacaine for spinal anaesthesia in patients of lower segment caesarean section -A randomized, comparative, controlled study

Spinal anaesthesia is a commonly practiced anaesthetictechnique in patients  undergoingelective or emergency lower segment caesarean sections. It is a safe, costeffective and easy to perform technique which provides a denser block and somore preferred. It also avoids  thevarious complications of general anaesthesia like stress response, airwaymanagement, post-operative nausea and vomiting and thereby facilitates earlierresumption of feeding and mobilization. Spinal anaesthesia has a quick onsetand provides satisfactory sensory and motor blockade. Administration of theappropriate choice and dose of local anaesthetic into the  subarachnoid space results in rapid onset ofdeep spinal anaesthesia with a greater degree of success .The rapidity of onsetof spinal block is advantageous in cases where delivery of the foetus needs tobe hastened  due to compromised fetalstate.1

The required dosage of effective block for LSCS has beenassociated with maternal arterial hypotension of 60-90% with maternal andneonatal morbidity2.The haemodynamic stability andprolonged duration of analgesia were observed by injecting the localanaesthetic drug in divided doses into the subarachnoid space.3-5

Spinal anaesthesia(SA) has rapidonset and is associated with various problems e.g. bradycardia , hypotension .Maternal hypotension may lead to decrease in uteroplacental perfusion which mayresult in fetal acid base imbalance, maternal nausea and vomiting and may be animportant contributory factor for maternal morbidity related to regionalanaesthesia.1 Maternal hypotension andsubsequent consequences are reduced to some extent by various measures likepreloading or coloading of crystalloids or colloids , low dose localanaesthetic, left uterine displacement, prophylactic use of vasopressors etcbut with reduction in incidence and severity of hypotension..

Several factors like height, weight, pregnancy andanatomical changes influence the dose of local anaesthetic drug for  its intensity and duration of spinal block.Many physiological and anatomical changes during pregnancy affect spinalanaesthesia. The hormonal and mechanical factors make pregnant women requireless local anaesthetic than non-pregnant women to attain same level of spinalanaesthesia.6

Levobupivacaine is an effective long acting amide localanaesthetic and is an S enantiomer of racemic bupivacaine , since it does notconatin R isomer , cardiotoxicity and neurotoxicity is lesser than bupivacaine.

In this regard, in addition to above mentioned measures,fractionated doses of local anaesthetic for spinal anaesthesia has been used toassess its effect on haemodynamic parameters in caesarean section.

In these studies, a fraction of two-third of calculateddose of local anaesthetic followed by one-third was used for spinal anaesthesia,with the incidence of hypotension during spinal anaesthesia in about 16 %patients as compared to 46% patients who had hypotension with non fractionateddoses (bolus doses).

Extensive search of literature did not show any studycomparing the two fractionated doses (one -thirdfollowed by two-third versus two-third followed by one-third)of localanaesthetic agent for spinal anaesthesia in the patients of caesarean section.

In the present study, haemodynamic parameters will becompared in spinal anaesthesia induced with either of two regimes offractionated doses (one -third followed by two-third versus two-third followedby one-third ) or single bolus dose of Levobupivacaine 0.5% Heavy  in patients of caesarean section.