Published on 07/02/2015 by admin
Filed under Anesthesiology
Last modified 07/02/2015
This article have been viewed 2276 times
Scott A. Gammel, MD
Tubal ligations are performed either as an interval (not postpartum) procedure or as an immediate postpartum procedure using local, regional, or general anesthesia.
Laparoscopy is the most common surgical approach for interval tubal ligations. Anesthetic considerations include those related to pneumoperitoneum, head-down positioning (with related cardiovascular and pulmonary changes), and other potential complications.
Pneumoperitoneum is performed via a needle inserted at the lower margin of the umbilicus (a relatively avascular and thin portion of the abdominal wall). An incorrectly placed needle can lead to insufflation of the abdominal wall, retroperitoneum, mesentery, omentum, or bowel. CO2 is the gas of choice to perform pneumoperitoneum because it is highly soluble, is rapidly absorbed postoperatively, and provides a margin of safety if injected intravascularly. N2O is less soluble and is not eliminated as quickly, but its use is associated with less peritoneal and diaphragmatic irritation and less postoperative shoulder pain.
Head-down (Trendelenburg) positioning is associated with brachial plexus injury if shoulder rests are used (as a result of clavicular compression of nerve roots); however, current guidelines recommend that shoulder rests not be used for patients in the Trendelenburg position. Because the Trendelenburg position results in decreased functional residual capacity, decreased pulmonary compliance, and altered stomach position, tracheal intubation will reduce the risk of pulmonary aspiration and atelectasis. Mainstem intubation may result from cephalad shift of the mediastinum and carina.
Cardiovascular changes result from increased intraabdominal pressure, patient position, anesthesia, and hypercarbia. Decreases in cardiac output, increased peripheral and pulmonary vascular resistance, increased arterial pressure, and arrhythmias may result.
Respiratory changes include decreased vital capacity, decreased functional residual capacity, increased blood volume, and decreased pulmonary compliance, which can lead to atelectasis. Peak inspiratory pressures increase. A significant increase in arterial CO2 (15% to 25%) and decrease in pH occur during general anesthesia when CO2 is used for insufflation because of absorption of CO2 from the pneumoperitoneum. Spontaneous ventilation can also lead to significant hypercarbia.
Other complications include hemorrhage, (accounting for almost half of complications), cardiac arrhythmias (some of which may result from reflex increases in vagal tone from peritoneal stretching or electrocautery of fallopian tubes), gas embolism, pneumothorax, pneumomediastinum, pneumopericardium, and mesenteric ischemia. Complications from creation of pneumoperitoneum and placement of trocars are more common with laparoscopy performed for tubal ligation than with laparoscopy for gastrointestinal surgery.
After intravenous induction takes place, O2, N2O, and an inhaled anesthetic agent are used to maintain anesthesia. This is supplemented with short-acting opioids and neuromuscular blocking agents.
Common postoperative complications of general anesthesia are abdominal and shoulder pain and postoperative nausea and vomiting (PONV). Increasing the volume of infused preoperative and intraoperative fluids reduces the incidence of PONV and improves hemodynamic response to pneumoperitoneum and postoperative recovery.
Metoclopramide (10-20 mg, administered intravenously 15-30 min before induction) and droperidol (0.5-1.0 mg, administered 3-6 min before induction) are synergistic in decreasing nausea, vomiting, and recovery time. Droperidol alone (0.625-2.15 mg) administered after intubation is an effective antiemetic for outpatient tubal ligation, and its use shortens time in the postanesthesia care unit. Ondansetron (4-8 mg, administered intravenously) before induction also significantly reduces the incidence of PONV.
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