Laparoscopy plays a prominent role in urology, a field that saw early adoption of these minimally invasive techniques starting with laparoscopic nephrectomy. Approaches and techniques in laparoscopy have evolved significantly over time, and the use of laparoscopy for surgery across organ systems has expanded. Alternatives to standard laparoscopy, including hand assistance and robotic assistance, further enhance capabilities.
PHYSIOLOGY OF LAPAROSCOPY
Laparoscopy with pneumoperitoneum exposes the patient to physiologic challenges that differ from those of open surgery but that can be met successfully with proper preparation and awareness (Ost et al, 2005).
As intra-abdominal pressure increases with pneumoperitoneum, the systemic vascular resistance increases and venous return decreases. A small increase in intra-abdominal pressure augments venous return and cardiac output. As intra-abdominal pressure rises, the increase in resistance exceeds the increase in pressure, and venous return and cardiac output fall (Figure 10–1). This transition point occurs at a lower intra-abdominal pressure in the hypovolemic compared with the normovolemic state. Given normovolemia, an intra-abdominal pressure of 15 mm Hg is associated with tolerable reduction of cardiac output.
Reduction of venous return and cardiac output during laparoscopy. (Adapted with permission from Wolf JS Jr, Stoller ML: The physiology of laparoscopy: basic principles, complications and other considerations, J Urol. 1994 Aug;152(2 Pt 1):294–302.)
The absorption of insufflated carbon dioxide (CO2) has direct cardioinhibitory effects, but CO2 also stimulates the sympathetic nervous system. If acidosis develops, then there are parasympathetic effects as well. Moderate hypercapnia (excess CO2 in blood) produces an increase in cardiac output and blood pressure and a decrease in systemic vascular resistance, which counteract the effect of intra-abdominal pressure.
Overall, an intra-abdominal pressure of 15 mm Hg and moderate hypercapnia in healthy patients produce a hyperdynamic state (increased central venous pressure, systemic vascular resistance, heart rate, and blood pressure) without significant alteration of cardiac output (Junghans et al, 2005).
Cardiovascular Physiological Complications
The cardiovascular complications of laparoscopy include tension pneumoperitoneum, cardiac dysrhythmias, fluid overload, and venous thrombosis.
When the intra-abdominal pressure is excessive, usually >40 mm Hg, the overwhelming increase of vascular resistance can produce tension pneumoperitoneum. This state can occur with loss of neuromuscular paralysis, for example, intraoperatively. Venous return, cardiac output, and blood pressure drop precipitously. Volume status must be optimized to prevent tension pneumoperitoneum at lower pressures. In general, the intra-abdominal pressure should be kept below 15–20 mm Hg. The response to tension pneumoperitoneum should be immediate desufflation.
Tachycardia and ventricular extrasystoles due to hypercapnia are usually benign, but fatal dysrhythmias can occur with very high arterial partial pressure of CO2 (PaCO2). Vagal stimulation by peritoneal distention can ...