D L. Prior*, J Sprung, J D. Thomas, D G. Whalley.

The Cleveland Clinic Foundation, Cleveland, OH, USA.

The cardiovascular effects of pneumoperitoneum (PP) include increases in systemic vascular resistance, arterial pressure and central venous pressure. Cardiac index is relatively unchanged in patients of ASA Class 1-2, but may be compromised in patients with cardiac disease. Laparoscopic surgery with PP is frequently undertaken in obese patients. The aim of the study was to determine the impact of obesity in combination with PP on left ventricular wall stress, a major determinant of myocardial oxygen demand.

Methods: Transoesophageal echocardiography (TOE) was performed during laparoscopic surgery on 7 obese females with body mass index (BMI) greater than 35 kg/m², and 8 female controls of normal weight. Patients were ventilated to maintain normocapnia. Blood pressure was measured invasively. Left ventricular (LV) meridional end-systolic wall stress was calculated from blood pressure values and systolic LV dimensions obtained from transgastric short axis TOE images at the midpapillary level. The effect of 20 mmHg PP was assessed in the supine, Trendelenburg and reverse Trendelenberg positions. Data were compared using ANOVA and P < 0.05 was considered significant.

Results: Obese patients were younger than controls (29.9±4.5 vs 42.3±7.3 yr), had higher weight (132.9±26.9 vs 61.6 ±13.2 kg) and BMI (47.9±6.7 vs 21.6±3 kg/m²). Wall stress values and systolic blood pressure are shown in the graph. Wall stress was higher in obese patients at baseline and with PP. Wall stress increased markedly with PP in obese, but not in  control patients. Although there was no difference in systolic BP at baseline, it increased significantly with PP only in obese patients.

Conclusions: Obese patients may be at higher risk of myocardial ischaemia during laparoscopic abdominal surgery than patients of normal weight due to higher wall stress both before and during the period of pneumoperitoneum.

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