Does Perioperative Lidocaine Infusion Decrease the Mininmum Alveolar Concentration of Isoflurane viz-a-viz Depth of Anaesthesia using Processed Electroencephalogram (Bispectral Index)

Introduction: Minimal alveolar concentration (MAC) ofvolatile anaesthetics is that which prevent movement in50% of subjects in response to a noxious stimulus. MACis influenced by several drugs like fentanyl, midazolam,propofol, clonidine. Various successful studies have been doneto demonstrate the effect of IV anaesthetics and opioids onMAC of various inhaled anaesthetics in balanced anaesthesiasettings. To assess the effect of a perioperative lidocaineinfusion on the MAC of isoflurane in a balanced anaesthesiatechnique by correlating it with the depth of anaesthesia asassessed by the Bispectral Index (BIS).Material and methods: It is a prospective randomized studyconsisting of 100 patients. The patients were categorized intogroup L and group S, Group L received a bolus of 1.5mg/kg of lidocaine five minutes before the induction of generalanaesthesia followed by 1.5mg/kg/hr of lidocaine infusiontill the end of the surgical procedure or upto a maximum ofthree hours (whichever was earlier). Group S received salinesimilarly. BIS was maintained between 40 to 60 and MAC ofisoflurane was measured in both group.Result: Significant difference with regard to MAC ofisoflurane used to maintain anaesthesia was noted betweenthe two groups. It was found overall average MAC ofisoflurane in Group L was (0.761±0.011) and control groupwas (0.885±0.020).Conclusion: Our study found that lidocaine loading dosefollowed by infusion significantly reduces volatile anaestheticrequirement as measured by MAC of isoflurane.

Effect of Age, Adrenaline and Operation Site on Duration of Caudal Analgesia in Paediatric Patients

The effect of age, operative site and addition of 1: 200,000 adrenaline to bupivacaine was evaluated on the duration of post operative analgesia after caudal block in 200 children between the age group of 1 year to 14 years. Anaesthesia was induced and maintained on Halothan/N2O/O2• After this caudal block was performed with 0.5 ml/kg of 0.25% bupivacaine in one group of 100 Children and with 0.25% bupivacaine with adrenaline 1 : 200,000 in another 100 children. The duration of post operative analgesia was noted to be significantly longer in young children, in children having penoscrotal operations and when adrenaline was added to bupivacaine. Conclusion was drawn that duration of post-operative analgesia depended upon age, site and addition of adrenaline to bupivacaine.