General Approach to the Obstetric Patient

General Approach to the Obstetric Patient

All patients entering the obstetric suite potentially require anesthesia, whether planned or emergent. The anesthetist should therefore be aware of the presence and relevant history of all patients in the suite. Pertinent historic items include age, parity, duration of the pregnancy, and any complicating factors. Patients definitely requiring anesthetic care (for labor or cesarean section) should undergo a focused pre-anesthetic evaluation as early as possible. This should consist of a maternal health history, anesthesia-related obstetric history, blood pressure measurement, airway assessment, and back examination for regional anesthesia.

All women in true labor should be managed with intravenous fluids (usually lactated Ringer's injection with dextrose) to prevent dehydration. An 18-gauge or larger intravenous catheter is employed in case rapid transfusion should become necessary. Blood should be sent for typing and screening in patients at high risk for hemorrhage or with a borderline acceptable hematocrit. Regardless of the time of last oral intake, all patients are considered to have a full stomach and to be at risk for pulmonary aspiration. Because the duration of labor is often prolonged, guidelines usually allow small amounts of clear liquid for uncomplicated labor. In contrast, patients at high risk for an operative delivery should take nothing by mouth. The minimum fasting period for elective cesarean section should be 6 h. Prophylactic administration of a clear antacid (15-30 mL of 0.3 M sodium citrate orally) every 3 h can help maintain gastric pH greater than 2.5 and may decrease the likelihood of severe aspiration pneumonitis. An H2-blocking drug (ranitidine, 100-150 mg orally or 50 mg intravenously) or metoclopramide, 10 mg orally or intravenously, should also be considered in high-risk patients and in those expected to receive general anesthesia. H2- blockers reduce both gastric volume and pH but have no effect on the gastric contents already present. Metoclopramide accelerates gastric emptying, decreases gastric volume, and increases lower esophageal sphincter tone. All patients should ideally have a tocodynamometer and fetal heart rate monitor. The supine position should be avoided unless a left uterine displacement device (> 15° wedge) is placed under the right hip. Uterine contractions can be directly measured via a catheter in patients with ruptured membranes, particularly those receiving oxytocin.