Physiological Changes:

Cardiovascular Effects: The critical determinants are IAP and patient positioning. If the IAP is kept below 15mmHg, venous return actually is augmented as blood is squeezed out of the splanchnic venous bed, producing an increase in cardiac output. At IAP levels greater than 15mmHg venous return decreases as the IVC is compressed. This results in decrease in cardiac output and arterial blood pressure. These cardiovascular changes are complicated by the patient's position during surgery. The head-up position favored for upper abdominal procedures e.g. Nissen's fundoplication and cholecystectomy further reduces venous return and cardiac output. This effect is more marked during fundoplication in which a greater degree of head up tilt (25⁰-30⁰) is required than for laproscopic cholecystectomy (15-30 degrees). Conversely when the patient is positioned head down, as for pelvic Laproscopy examination, venous return is augmented and blood pressure returns to normal or supra normal values. Other cardiovascular phenomena can result from insufflating gas into the peritoneum. Children have a high level of vagal tone and occasionally peritoneal stimulation by a blast of insufflated gas or penetrated by trocars and laparoscopes can provoke bradycardia or asystole. Patients with normal cardiovascular function tolerate variations in preload and afterload well, but those with cardiovascular disorders, anemia or hypovolemia require meticulous attention to volume loading, positioning and insufflation pressures.

Causes of cardiovascular collapse: