Morbidly obese patients are hemodynamically stable during laparoscopic surgery: a thoracic bioimpedance study

Morbid obesity caries an increased risk of cardiovascular morbidity and might be associated with intraoperative hemodynamic instability. Based on clinical observation, we hypothesized that during laparoscopic surgery, morbidly obese patients behave hemodynamically similar to the nonobese patients and remain hemodynamically stable.

In a prospective trial, thirty nonobese and tthirty morbidly obese (BMI > or = 35 kg/m(2)) patients scheduled for elective laparoscopic surgery were assigned to receive standard balanced anesthesia. We aimed at equianesthetic levels by keeping the BIS (bispectral index) value between 40-50 throughout surgery. End-tidal isoflurane was measured every 5 min. Noninvasive hemodynamic measurements included cardiac index (CI), mean arterial pressure (MAP) and heart rate (HR), recorded every 5 min and at specific predetermined times. Systemic vascular resistance (SVR) was calculated. Episodes of MAP < or = 60 and MAP > or = 130 mmHg or HR < or = 50 and HR > or = 110 bpm occurring throughout surgery and requiring pharmacological intervention were considered main end-points. Additionally, hemodynamic variables were compared at specific time points and overall throughout surgery. Secondary end-points were CI and SVRI.

Heart rate was higher in obese patients in head-up position (79 +/- 15 mmHg vs. 65 +/- 12 mmHg - P=0.011). SVR was higher in the nonobese group with head-up position (1978 +/- 665 dynes s cm(-5) vs. 1394 +/- 496 dynes s cm(-5) P=0.01). Mean overall intraoperative MAP, HR, CI and SVR were similar. There were no episodes of MAP < or = 60 and > or =130 mmHg or HR < or = 50 and > or =110 bpm in either of the groups.

Our study confirmed our hypothesis that for the most periods of laparoscopic surgery, obese patients are hemodynamically as stable as their nonobese counterparts.