Cardiopulmonary Disorders

Patients with severe cardiopulmonary diseases have higher surgical risks regardless of the approach. Due to their low cardiopulmonary reserve, these patients may develop important complications during and after laparoscopic surgery.

Pneumoperitoneum is less well tolerated in these patients. CO2 is quickly absorbed during laparoscopy (14). This gas is highly soluble in water and easily diffuses in body tissues. Because of its high diffusion coefficient relative to oxygen and other respiratory gases, it readily moves out of the peritoneal cavity owing to a high diffusion gradient caused by the difference in concentration of CO2 between the intraperitoneal space and the surrounding components (e.g., blood). However, the characteristic of rapid absorption, which lessens the chance of a CO2 gas embolus, may also lead to potential problems (e.g., hypercapnia, hypercarbia, associated cardiac arrhythmias). In particular, patients with chronic obstructive pulmonary disease may not be able to compensate for the absorbed CO2 by increased ventilation; this may result in dangerously elevated levels of CO2 in these patients. CO2 also stimulates the sympathetic nervous system, which results in an increase in heart rate, cardiac contractility, and vascular resistance. Lastly, CO2 is also stored in various body compartments (e.g., viscera, bones, muscles). After prolonged laparoscopic procedures, it may take hours before the patient has eliminated the extra CO2 that has accumulated in these storage areas; again, this is more often the case in patients with pulmonary compromise (15,16).

The cardiovascular effects of pneumoperitoneum are diverse and are exaggerated in patients with cardiovascular disorders.

First, the effects of the pneumoperitoneum on venous return depend on atrial pressures, which, in turn, are a reflection of the hydration state of the subject. If atrial pressures are low (normal or hypovolemic state), then, during a pneumoperi-toneum of up to 20 mmHg, venous return is reduced owing to increased compression of the vena cava from the pneumoperitoneum. If atrial pressures are high (hypervolemic state), the vena cava resists elevated intra-abdominal pressure, and venous return is actually enhanced. These principles apply only to an intra-abdominal pressure of up to 20 mmHg. Therefore, all patients, and in particular those with

TABLE 3 ■ Differential Diagnosis of Ascites

Hypoalbuminemia

Hepatic congestion

Peritoneal infections

Neoplasms

Lymphatic obstruction

Meigs'syndrome, struma ovarii

Chronic pancreatitis or pseudocyst

Bile ascites

Urine ascites

Chylous ascites

The respiratory effects of pneumoperitoneum are also exaggerated in the patient with pulmonary disorders. Owing to increased intra-abdominal pressure, diaphragmatic motion is limited. Pulmonary dead space remains unchanged, but functional reserve capacity decreases.

pulmonary disease, must be closely monitored for several hours after lengthy laparoscopic procedures. It is important for the anesthetist not to rely on central venous pressure readings for any clinical decision making. If information regarding vascular volume and central venous pressure is needed, a Swan-Ganz catheter should be placed.

Tachycardia and ventricular extrasystoles may be seen as results of hypercapnia (17). Peritoneal irritation may lead to vagal stimulation and subsequently to brad-yarrhythmias. Also, dysrhythmias can serve as clinical warning signs for the occurrence of pneumothorax, hypoxia, and gas embolism (14).

The respiratory effects of pneumoperitoneum are also exaggerated in the patient with pulmonary disorders. Owing to increased intra-abdominal pressure, diaphragmatic motion is limited. Pulmonary dead space remains unchanged, but functional reserve capacity decreases (14).

The average peak airway pressure needed to keep up a constant tidal volume increases parallel to the increasing intra-abdominal pressure. Although usually not of great clinical importance in a healthy patient population, it is advisable to use positive end-expiratory pressure techniques when patients with lung disease undergo general anesthesia for a laparoscopic procedure (14).

The Trendelenburg position (used in lower urinary tract surgery) has an adverse effect on respiration as well. It elevates the diaphragm and decreases vital capacity. It can also lead to a dislocation of the endotracheal tube, which, in turn, may cause right mainstem bronchus intubation. Although of little clinical significance in healthy patients, the Trendelenburg position may cause pulmonary edema in patients with increased left-sided heart pressures.

Mechanical abdominal wall lift has been proposed as an alternative method of exposure in laparoscopic surgery to obviate or minimize the adverse physiologic effects of pneumoperitoneum in patients with high cardiopulmonary risk factors. Other theoretical advantages of this technology include minimization of the risk of CO2 embolism in trauma patients and tumor dissemination in patients undergoing laparoscopic surgery for cancer. Abdominal wall lift systems do appear to reduce the adverse cardiovascular and respiratory effects, but they do so at the expense of surgical exposure, which is less optimal than that provided by the positive-pressure pneu-moperitoneum. This reduced exposure increases the technical manipulation and exposure during the operation and, hence, the operating times. This problem is overcome by combination of abdominal wall lift with low-pressure (3-4 mmHg) pneu-moperitoneum. This combination provides good surgical exposure without adverse cardiovascular consequences (18).

Presence of ascites is considered a contraindication to laparoscopic surgery because of the increased risk of port site metastasis.

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