Cardiocirculatory Effects of Laparoscopic Surgery

Most studies investigating the cardiovascular changes associated with laparoscopic surgery report an increase in systemic vascular resistance (SVR), mean arterial blood pressure (MAP), and myocardial filling pressures, accompanied by a fall in cardiac index (CI) with little change in heart rate (1). The changes are typically pronounced after the beginning of the carbon dioxide (CO2) insufflation with a gradually increasing CI during the further course. The alterations in cardiovascular function depend on the interaction of several patient and surgical factors including intraabdominal pressure (IAP), patient postion, CO2 absorption, ventilatory regime, and surgical technique as well as the nature and duration of the procedure. Furthermore, the intravascular volume, preexisting cardiopulmonary status, neurohumeral factors and perhaps patient medication and the anaesthetic agents used all can influence the cardiovascular responses to the creation of pneumoperitoneum and laparoscopy. Increased intra-abdominal pressure causes compression of the abdominal venous and arterial vasculature. Aortic compression contributes to an increase in SVR and afterload, and venous compression causes -after a transient increase in venous returna decline in preload as flow through the inferior vena cava is significantly reduced. Although venous return decreases, central venous pressure (CVP) and pulmonary occlusion pressure (PAOP) rise during abdominal insufflation. This is caused by a cephalad shift of the diaphragm with an increased IAP and intrathoracic pressure. Thus, in this setting -in either the head-up or head down positionCVP and PAOP do not accurately reflect ventricular filling. Cardiovascular changes are proportional to the IAP attained. In an experimental model the threshold pressure that had minimal effects on haemodynamic function was 12 mm Hg. This has been largely confirmed by clinical studies (1). The patient position has significant effects on the haemodynamic consequences of pneumoperitoneum. Maximal haemodynamic changes are observed when the pneumoperitornuem is created in patients in the reverse Trendelenburg position. A decline in CI up to 50 % has been reported following insufflation of the abdomen in the head up postion, whereas no changes were observed in CI or EF with insufflation in the supine position. While the reverse Trendelenburg is accompanied by a venous pooling and a fall in preload, the trendelenburg position is associated with increased venous return. New insights into the cardiocirculatory changes effects of laparoscopic surgery provided a recent animal study in pigs investigating the effects of capnoperitoneum (CP) with an IAP of 14 mm Hg on the intrathoracic blood volume and haemodynamic parameters. While in the supine position ITBV, stroke volume (SV) and CO remained unchanged, CP in a head-down position lead to a decrease in ITBV and CO by 7 %. Finally, CP in a head-up position lead to a decrease in ITBV, SV and CO by 16, 29 and 28 % respectively. Most interestingly, the decrease in CO could be completely offset by volume loading (3). Finally, the issue of the systemic effects of the most commonly used insufflation gas, carbon dioxide (CO2) deserves attention. Mild hypercapnia can cause sympathetic stimulation that leads to an increase in heart rate and peripheral vasoconstriction, resulting in increased blood pressure and increased cardiac output. Severe hypercapnia can exert a negative inotropic effect on the heart, resulting in a depression of left ventricular function. The degree to which CO2 absorption contributes to the haemodynamic responses to a (capno) pneumoperitoneum is unclear since the majority of studies did not attempt to separate the effects related to hypercapnia from those related to the increased intra-abdominal pressure. In a pig model the decrease in stroke volume and tachycardia observed during CO2 pneumoperitoneum did not coccu when nitrogen was used (2). Thus CO2 absorption may indeed contribute to the haemodynamic effects of laparoscopy with CO2 insufflation.