The effect of multimodal analgesia on minimum alveolar concentration of isoflurane for skin incision at constant bispectral index

BACKGROUND: Multimodal analgesia (MMA) by synergy with volatile anesthetics minimizes their use thus decreasing operation theater pollution and greenhouse gas emission. AIMS: To estimate minimum alveolar concentration (MAC) requirement of isoflurane (ISO) for skin incision with use of MMA in the study group versus conventional regime in the control group for a constant bispectral index (BIS). To observe the side effects of analgesic drugs administered in the study. SETTINGS AND DESIGN: Forty-two patients of American Society of Anesthesiologist Class I and II scheduled for lumbar spine surgery were included in this prospective, randomized, double-blind, clinical study. They were randomly allocated into two groups of 21 each. MATERIALS AND METHODS: Group A (MMA group/study group) received injections diclofenac sodium, paracetamol, clonidine, and fentanyl and local infiltration (bupivacaine with adrenaline). Group B (conventional regime group/control group) received injections paracetamol and fentanyl and local infiltration (saline with adrenaline). Preemptive analgesia was practiced in the study. The MAC of ISO for skin incision was documented. STATISTICAL ANALYSIS USED: Independent sample t-test: To compare MAC(ISO) for skin incision between the two groups. One sample t-test: To compare the standard mean concentration with the means of the two groups. Chi-square test: To compare adverse effects between the groups. P < 5% was considered statistically significant. RESULTS: The MAC(ISO) requirement was significantly lower in the study group at the time of skin incision for BIS of 50–55 compared to the control group (P < 0.001). Post extubation, 43% had nausea and 9% had vomiting in the control group. None of the patients in either group had intraoperative awareness. CONCLUSION: We conclude that preemptive MMA has synergistic effect with ISO. It effectively reduces MAC(ISO) to skin incision to a greater degree.