Laparoscopic Cholecystectomy in Pregnancy: A Video Case

Saad Shebrain, MD, MBBch; Elizabeth A. Steensma, MD; Dwight Slater, MD

Disclosures

April 21, 2011

Physiologic Changes in Pregnancy and Laparoscopy

Pregnancy is associated with both anatomic and physiologic changes. The physiologic changes aim to meet the demands of increased metabolic needs of both the mother and the fetus. These changes affect almost all body systems, but the cardiopulmonary and renal systems show significant effects, including:

  • Increased blood volume, which begins in week 6 of gestation and by the end of pregnancy reaches approximately 50% more than the prepregnant blood volume;[48,49]

  • Decreased peripheral vascular resistance with subsequent reduction in both systolic and diastolic blood pressures. These changes begin in week 5 of gestation, are lowest at midpregnancy, and then gradually reverse after week 32 of gestation;

  • Systemic blood pressure begins to decline in the first trimester, reaching its lowest level at midpregnancy, and gradually increasing to a level equal to or higher than the prepregnancy blood pressure;[50,51]

  • Increased heart rate, stroke volume, and cardiac output (the product of heart rate and stroke volume). Mean heart rate usually increases by 10-20 beats/minute over the course of pregnancy, reaching a peak in the late second trimester or early third trimester;

  • Increased renal blood flow (RBF) and glomerular filtration rate. RBF peaks in the third trimester at about 60%-80% above prepregnancy levels;[45,51,52] and

  • Changes in pulmonary mechanics with increased minute ventilation (product of respiratory rate and tidal volume) because of increases in tidal volume; the respiratory rate does not change. Functional residual capacity decreases by 15%.

Effects of Pneumoperitoneum

Pneumoperitoneum insufflation set at 12-15 mm Hg is essential to provide adequate visualization and exposure of the operative field for conducting a safe procedure. However, this amount of pressure is also associated with increased intra-abdominal pressure.[53] Creating a pneumoperitoneum affects the patient's physiology and hemodynamic status, and these effects are amplified during pregnancy, both mechanically and biochemically. From a respiratory standpoint, upward displacement of the diaphragm can further reduce lung compliance and increase peak airway pressures.[54] Furthermore, this reduces the patient's residual volume and functional residual capacity, both of which are already lower in pregnancy.[47]

Increased intra-abdominal pressure leads to decreased venous return to the right heart and subsequently, with a lower left ventricular end-diastolic volume, reduced cardiac output.[47] Because mean arterial pressure is directly proportional to cardiac output and systemic vascular resistance (SVR), an increase in SVR compensates for lower cardiac output.[47,54] For these reasons, a general consensus has been reached to use abdominal pressures between 8-12 mm Hg, and no greater than 15 mm Hg during laparoscopy.[55]

Reduced uterine blood flow from a pneumoperitoneum is a theoretical risk, because significant changes in intra-abdominal pressure occur normally during pregnancy with maternal Valsalva maneuvers.[56] Much attention has been paid to the potential for increased carbon dioxide (CO2) absorption, resulting in both maternal and fetal acidosis. Capnography, using an end-tidal CO2 (ETCO2) level between 32-34 mm Hg, has been shown to be safe.[15,57] If maternal acidosis does occur, it can be overcome with mild hyperventilation.

In terms of fetal effects, concerns have been raised about fetal absorption of CO2, acidosis, diminished uteroplacental blood flow secondary to the increased abdominal pressure, and decreased cardiac output.[15,46,47] In animal models, it has been shown that reducing the pneumoperitoneum as described above and monitoring maternal ETCO2 can temper these concerns.[58] Careful monitoring of both the fetus and the mother is essential to maximize safety when performing laparoscopic procedures. Acid-base disturbances, such as acidosis and hypercapnia, can result from absorption of CO2. To prevent this sequence of events, adequate elimination of CO2 through the lungs, by increasing the respiratory rate, must be ensured. Inadequate elimination (eg, a patient with lung disease) will exacerbate the adverse outcomes of these abnormalities, especially in patients with limited cardiopulmonary reserve. A synergistic effect of both acidosis and hypercapnia can depress myocardial contractility.

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