Physiologic Responses Cardiovascular

Cardiovascular effects of intra-abdominal insufflation with CO2 are clinically insignificant in healthy and normovolemic patients.

Table 1 summarizes the cardiovascular effects of an intra-abdominal pressure of 15 mmHg with typical CO2 absorption (moderate hypercapnia). Certainly, the response of any individual patient will vary.

With 15 mmHg pressure of CO2 insufflation, central venous pressure, systemic vascular resistance, heart rate, and mean arterial pressure increase. However, the effect on cardiac output may range from a decrease of 17% to 28% (15,31,32), to no net change (14,19), to an increase of 5% to 7% (35,54).

Intra-abdominal CO2 insufflation pressure between 5 and 10 mmHg may increase cardiac output in patients by 4% to 28% (29-31). Intra-abdominal pressure above 40 mmHg risks marked reduction of cardiac output (19). Hypovolemia will negatively alter these hemodynamic effects. The head-down tilt position for pelvic laparoscopy has a moderately favorable impact on hemodynamics.

Urine output decreases during laparoscopy (64,65).

Patients with cardiac disease (ischemic or myopathic) are at greater risk for intraoperative hemodynamic problems (55,56).

Numerous studies have confirmed the more marked cardiovascular effects of laparoscopy in individuals with cardiac disease. However, thorough patient preparation, attentive monitoring, and careful intraoperative management make pneumoperitoneum tolerable even for these patients (57-59).

Numerous studies have confirmed the more marked cardiovascular effects of laparoscopy in individuals with cardiac disease. However, thorough patient preparation, attentive monitoring, and careful intraoperative management make pneumoperitoneum tolerable even for these patients.

TABLE 1 ■ Hemodynamic Response to Laparoscopy

Intra-abdominal pressure of 15 mmHg

Moderate hypercapnia

Combined

Central venous pressure Systemic vascular resistance Heart rate

Mean arterial pressure Cardiac output

Increase Increase Increase Increase Decrease

Increase Decrease Increase Increase Increase

Increase Increase Increase Increase Variable

Reduction in lung capacity and compliance, and worsening of ventilation-perfusion mismatch are the most pronounced pulmonary effects of intraabdominal insufflation with CO2. These effects are exacerbated by the head-down tilt position for pelvic laparoscopy.

When compared to open surgery, laparoscopy tends to be associated with less stress, immunologic compromise, and inflammation. However, results of published studies have been markedly variable in this regard.

The kidney appears to be particularly compromised more than other organs by the combination of hypovolemia and increased intra-abdominal pressure.

The mechanisms involved in oliguria during CO2 insufflation include (i) increased renal vein resistance (with subsequent decreased renal blood flow); (ii) renal parenchymal compression; (iii) activation of hormonal factors such as the renin-angiotensin system; and (iv) increased levels of antidiuretic hormone.

Urine output decreases during laparoscopy.

Normal pulmonary function is adequate to eliminate the small amount of absorbed CO2. In most patients, any tendency toward an increase in PaCO2 owing to CO2 absorption and worsened lung mechanics is easily addressed by increasing minute ventilation.

Operative laparoscopy can be performed safely in patients with cardiac ejection fractions less than 15% (60), or morbid obesity (54).

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