Cardiopulmonary Function and Laparoscopic Cholecystectomy

Abstract

Comments: The authors are to be congratulated on providing a timely and comprehensive review of cardiopulmonary function during laparoscopic cholecystectomy and postoperative pulmonary function changes. The review was sourced from a MEDLINE literature search from North American journals (Anesthesiology, Anesthesia and Analgesia, and the Canadian Journal of Anaesthesia) and also included European perspective through the British Journal of Anaesthesia. The review stressed the well known acute cardiovascular changes, i.e., depression of cardiac index (CI) and increase in systemic vascular resistance (SVR) after induction of anesthesia, insufflation of the abdomen with CO2 and institution of the reverse Trendelenberg (rT) position. The autiiors, however, went on to elaborate on the changes in CI, mean arterial blood pressure (MABP), and SVR in patients with mild heart disease and those with clinically severe systemic diseases (ASA III-IV). The most striking features were the considerable initial reduction in CI occurring simultaneously with large increases in MABP and SVR. The authors made a clear distinction between the sequential hemodynamic effects of anesthesia, positioning (usually 20, rT), mechanical and neuroendocrine effects, and those of exogenous CO2 insufflation. The initial reduction in CI may be directly because of the myocardial depressant and vasodilatory effects of the anesthetic. This change may be followed by a reduction in venous return (preload) caused by positioning in rT. Based on a comprehensive and audioritative review of the relevant literature, the authors went on to suggest a number of practical clinical applications. Considering the adverse hemodynamic effects of laparoscopic cholecystectomy, particular attention should be paid to the inflation pressure and the degree of tilt, especially in ASA III-IV patients. The magnitude of decrease in cardiac index is directly related to insufflation pressure. The authors recommend slow and gradual abdominal insufflation to a maximum pressure of 10 mm Hg followed by a limited 10A of head-up tilt, which has been claimed to provide cardiovascular stability in elderly ASA III-IV patients. An increase in ventilation may be required because of the large amounts of CO2 absorbed during laparoscopic cholecystectomy. Postoperative lung function after laparoscopic surgery is succincdy reviewed. The authors claim that data support the belief mat laparoscopic cholecystectomy leads to better postoperative lung function compared with the traditional open procedure. However, changes in vital capacity and functional residual capacity are qualitatively similar but of a lesser degree after laparoscopic cholecystectomy in healthy patients. Intraoperative pulmonary changes, the authors claim, are caused by reduced pulmonary compliance secondary to movement of the diaphragm during insufflation and to changes in CO2homeostasis secondary to absorption from the peritoneum. The authors conclude with the timely caveat that end-tidal CO2tension is not a reliable index of Paco2, especially in ASA III-IV patients. Serial Paco2 determination may be warranted in such higher risk patients.