Anaesthesia for morbidly obese patients: a study of haemodynamic changes during bariatric surgery

Morbid obesity with body mass index (BMI) > 40 kg/m2 requires surgical correction if the diet program fails. Laparoscopic adjustable gastric banding (LAGB) (bariatric surgery) is the standard surgical procedure. The haemodynamic effects of the typical pneumoperitoneum had been studied but, the additional effects of morbid obesity and the consequences of LAGB surgery had not. Therefore, we conducted this study to determine the haemodynamic changes under anaesthesia during bariatric surgery.

Under general anaesthesia, 7 patients (4 males) were studied. Their mean age was 36.2 yr (range 25-50 yr) and mean BMI was 49.7 kg/m2 (range 39.3-67.3). Besides routine monitoring of vital signs, non invasive cardiac output monitor (NICO, Novametrix, Wallingford, CT, USA) was used to monitor cardiac output (CO), cardiac index (CI) and stroke volume (SV). All the haemodynamic variables were taken at three phases: A) after induction of anaesthesia, B) during pneumoperitoneum and C) after gas deflation.

The mean HR and BP showed significant high values during phase B compared to phase A. The mean values of CO were 7.2 +/- 1.1 and 9.06 +/- 2.6 L/min during phases A and B respectively with significant differences. The mean values of SV were 91.1 +/- 12.3 and 123.2 +/- 42.6 ml during phases A and B respectively with significant differences. The mean values of CI during phases A and B were 3.1 +/- 0.7 and 3.4 +/- 1.09 L/min/m2 respectively with significant differences.

We have reported high CO and CI during pneumoperitoneum, which may be due to increased heart rate induced by sympathetic stimulation.