Reverse Trendelenburg's position vs. supine-horizontal position for induction of general anesthesia in obese neurosurgical patients

Abstract

INTRODUCTION: The induction of general endotracheal anesthesia (GETA) is associated with variable period of apnea. Obese patients have reduced oxygen supply during period of apnea. Hypoxemia and subsequent hypercarbia, during period of apnea, are strong stimuli of cerebral blood flow and intracranial pressure increase. OBJECTIVE: The objective of our study was to determine the patient position with safe apnea period (SAP), which will minimize the risk of hypoxemia, as an optimal positioning for induction of GETA in obese neurosurgical patients. METHOD: Obese patients (BMI > 30kg m(-2)) were randomly placed to one of two positions for induction of GETA: group I (n=20) consisted of patients assuming 30 degree reverse Trendelenburg's position; group II (n=20) was in supine-horizontal position. After the arterial oxygen saturation of 100% measured by pulse oximetry (SpO2), patients were allowed to remain apneic. The time required for SpO2 to decline from 100% to 94% was recorded as SAP. The lowest SpO2 after restoration of ventilation and recovery time to 98% SpO2 were also recorded. RESULTS Time needed for SpO2 to decline to 94% was: 196.9 +/- 21.53 sec in group I, and 130.65 +/- 25.73 sec in group II. There was significant difference between groups (I vs. II; p < 0.05). SpO2 of patients in the reverse Trendelenburg's position dropped the least and took the shortest time to restore to 98%. The recovery time was much longer in group II, 132.65 +/- 33.75 (I vs. II; p < 0.05). CONCLUSION: 30 degree reverse Trendelenburg's position provides longer SAP when compared with horizontal-supine positions. This extra time may preclude adverse sequelae resulting from hypoxemia during induction of obese neurosurgical patients.