The Four H’s of surgery on pregnant patients:
1. Prevent maternal hypotension
2. Prevent maternal hypoglycemia
3. Prevent maternal hypothermia
4. Prevent maternal hypoxia
The patient should be positioned in a partial left lateral tilt to reduce pressure on the vena cava and maintain adequate venous return. Reese and Willis determined that a tilt at 27 degrees was optimal for cardiopulmonary resuscitation and would also be sufficient for general operative procedures on patients beyond the first trimester . This concept is universally practiced in the abdominal delivery of fetuses at term or otherwise, for any indication mandating delivery.
The Swedish Birth Registry as described by Mazze and Källén provides the most extensive data regarding anesthetic and surgical risks to pregnant women . The analysis of the effects on pregnancy outcomes of 5405 nonobstetrical surgical procedures performed in 720,000 pregnant women from 1973 to 1981 was reported. General anesthesia was administered for approximately half of these procedures and frequently involved nitrous oxide supplemented by another inhalation agent or intravenous medications. These procedures were performed on 41 percent of women in the first trimester, 35 percent in the second, and 24 percent in the third (Fig. 11.1). Twenty-five percent were abdominal operations, and 20 percent were gynecological or urological procedures. The most frequently performed procedure was laparoscopy, and appendectomy was the most common second-trimester procedure.
Percentage of surgical procedures by trimester
Increased perinatal morbidity related to nonobstetrical surgery is often attributable to the underlying disease process rather than to adverse effects of surgery and anesthesia. The Swedish Birth Registry again provides valuable data .
The incidence of newborns with congenital malformations or those stillborn was not considerably different from that of nonexposed control neonates. However, there were significantly increased incidences of low birth weight, preterm birth, and neonatal death in infants born to women who had undergone surgery. Increased neonatal deaths were mainly due to preterm birth. These investigators concluded that these adverse outcomes likely were due to a synergistic effect of the maternal morbidity in conjunction with the surgical procedures. Hong reported that there was an increased preterm delivery rate in 235 women undergoing adnexal mass surgery .
The Role of Minimally Invasive Technologies
Pelviscopy, originally termed laparoscopy , was considered to be absolutely contraindicated in pregnancy until 1990. Nezhat et al. reported the first pelviscopic cystectomy in a gravid woman in 1991. Technology since then has led to the development of myriad endoscopic procedures as the safety of the technique in the pregnant population has been very widely appreciated .
Pelviscopy is now considered the standard of care in the management of much of the pathology in the gynecologic and obstetric populations. Examples include total pelviscopic hysterectomy, salpingectomy, oophorectomy, endometriosis resection, ovarian cystectomy, appendectomy, bowel resection, and ovarian detorsion. Several müllerian anomalies may be managed pelviscopically. Single-incision pelviscopy is emerging as an even less invasive operative intervention in treating the array of gynecological pathologies that afflict women.
Fatum et al. have shown that the benefits of pelviscopy in the nonpregnant patient can be applied to the gravid woman . The pelviscope affords a magnified, improved, and wide view of the operative field. The smaller incisions for the ports into the abdomen result in lesser postoperative pain and more rapid postoperative recovery. Reduction in postoperative pain leads to a decreased postoperative narcotic consumption, earlier ambulation, and a reduced risk of thromboembolism. Fetal depression is also less likely with reduced maternal narcotic use. Bowel manipulation is usually minimal during pelviscopy, which benefits a quicker return to bowel function, and a possible diminution in postoperative adhesions, ileus, and bowel obstruction [9–11]. The smaller scars from pelviscopy result in less incisional hernias , lower the risk of wound complications , and create less opportunity for wound dehiscence as the gravid uterus distends the abdomen. Women undergoing pelviscopic procedures also experience shorter hospital stays and promptly return to regular activities .
Visualization and performance of pelviscopic procedures require pneumoperitoneum . The cardiovascular and respiratory adaptations observed with pneumoperitoneum during laparoscopy are heightened in the pregnant patient compared with the general population . The combination of the enlarging uterus which mechanically displaces the diaphragm together with pneumoperitoneum produces decreased compliance of the thoracic cavity, a decrease in the functional reserve capacity, an increase in peak airway pressure, ventilation–perfusion mismatching, increased alveolar–arterial oxygen gradient, and increased pleural pressure. These changes are further accentuated by the Trendelenburg position commonly employed in pelviscopy [9, 13, 14]. The arterial carbon dioxide partial pressure is increased with pneumoperitoneum because of absorption of carbon dioxide from the peritoneal cavity. This increase and the concomitant decrease in arterial pH is of concern in that it may adversely affect the fetus because fetal arterial CO2 is directly related to maternal arterial CO2. Bhavani-Shankar et al. investigated this in eight gravid women at 17–24 weeks’ gestation that underwent pelviscopic surgery with carbon dioxide pneumoperitoneum . The minute ventilation was adjusted to keep the end tidal CO2 at 32 mmHg, and arterial blood gas was measured at preinsufflation, insufflation, postinsufflation, and postoperatively. There were no differences observed in the partial pressure of arterial CO2 to end-tidal CO2 gradient, or the partial pressure of arterial CO2 and pH during the different phases of monitoring. The investigators concluded that end-tidal CO2 correlated with arterial CO2 and that optimal maternal arterial CO2 could be maintained during pelviscopy by adjusting minute ventilation . Blood gas monitoring may not be necessary in healthy patients undergoing pelviscopy .
Cardiovascular and hemodynamic changes that occur with pneumoperitoneum are the result of a combination of the physiological effects of patient positioning, anesthesia, and carbon dioxide absorption. Insufflation decreases cardiac output, with a concomitant increase in systemic and pulmonary vascular resistance and blood pressure [13, 16]. The reverse Trendelenburg position has been shown to intensify the cardiovascular changes observed with general anesthesia and pneumoperitoneum with a reduction in the cardiac index of up to 50%. Significant hypotension is also detected resulting from aortocaval compression by the pregnant uterus in conjunction with the other cardiovascular changes induced by pneumoperitoneum [13, 16]. After 15 min of insufflation, a study investigating the hemodynamic changes in laparoscopic surgery in pregnant women revealed that the cardiac index dropped to 21% below baseline. Systolic blood pressure 20% below baseline was aggressively managed with intravenous ephedrine to minimize any decrease in uterine perfusion . Left uterine displacement and limiting the intra-abdominal insufflation pressure to 12 to 15 mmHg are essential to minimizing these cardiovascular changes .
Pelviscopy during pregnancy is not without controversy. Timing, the safest method of abdominal cannulation , and appropriate fetal and maternal monitoring are issues that have been raised over time. Pregnancy in the first trimester poses the least technical challenges during abdominal and pelvic surgery. The first trimester uterus is well below the point of initial trocar entry, and visualization of the pelvis and adnexa is optimal. Teratogenesis risk, however, is greatest during this trimester. Second trimester operations pose less risk to the fetus but are technically more difficult, requiring greater surgical skill. The third trimester is attendant with a greater potential for preterm labor, and visualization difficulties are further pronounced by the enlarging uterus. The safest interval for operative intervention for elective cases is during the second trimester. This is explained by the decreased rate of spontaneous abortion, and the risk of premature labor increases as the gestation progresses .
Trocar placement and insertion of the pelviscope are determined by uterine size and gestational age. Many surgeons utilize the open Hasson technique when operating in the second and third trimesters; however, studies have shown that closed-entry techniques are undertaken by others . The left upper quadrant (Palmer’s point) entry is frequently chosen for insertion of the Veress needle in the closed-entry technique, beyond the first trimester. With this approach, the primary trocar is placed in the midclavicular line, 2 cm below the ribcage. Ultrasound guidance has been utilized to improve the safety of Veress needle and trocar insertion. Similarly, a subxyphoid entry can be undertaken with the trocar placement 2–6 cm above the umbilicus, varying with the fundal height. The additional trocars are then placed under direct visualization. The use of vaginal instrumentation, cervical clamps, and uterine manipulators is contraindicated in the pregnant patient .
Because there are a large number of physiological changes seen with gestation and the cardiovascular and pulmonary changes induced by laparoscopic surgery, optimal perioperative monitoring is unclear. The standard precautions that apply to pregnant women undergoing surgery should be sustained in laparoscopic surgery. End-tidal CO2 should be maintained between 32 and 34 mmHg when using CO2 insufflation by increasing respiratory rate and tidal volume and systolic blood pressure should be kept within 20% of baseline .