David H. Chestnut

Epidural Narcotics for Postoperative Analgesia

Epidural narcotic analgesia was assessed in 66 patients after surgery under epidural and light general anesthesia. Changes of forced expiratory volume in 1 second (FEV,) were measured after upper abdominal or thoracic surgery in 41 patients, and comparisons were made with results in an additional 17 upper abdominal surgery patients who received general anesthesia and muscle relaxants followed by intravenous morphine for postoperative pain relief. Metha- done, 1.0 mg, hydromorphone, 1.0 mg, or morphine sulfate, 5 mg, was administered epidurally and increments were repeated as necessary until satisfactory analgesia was reported, with the following results (mean ± SD): intravenous morphine: latency 3 to 10 minutes, duration 3.1 ± 1.6 hours; epidural methadone: latency 17.2 ± 4 minutes, duration 5.6 ± 2.7 hours; epidural hydromorphone: latency 22.5 ± 6 minutes, duration 9.8 ± 5.5 hours; epidural morphine: latency 36 ± 6 minutes, duration 16.4 ± 7 hours. Duration of action was slightly longer after lower abdominal surgery. Addition of epinephrine 1 /200.000 to the epidural narcotic solutions did not prolong duration. Narcotic requirements for satisfactory analgesia were approximately the same by the intravenous route as by the epidural route and equivalent to 8.5 to 9 mg of morphine. FEV, was reduced to 36.8 ± 13.2% of preoperative control values after general anesthesia and muscle relaxants and to 46 ± 12% of control after epidural and general anesthesia. Intravenous morphine improved FEV, to 45.3 ± 12% of control, whereas epidural narcotics and local anesthetics produced a greater increase of FEV, in the following amounts: epidural local anesthetic to 68.7 ± 9.1% of control and epidural narcotics to 67.1 ± 14.7% of control. Epidural narcotics did not cause sympathetic depression or bladder dysfunction, and analgesia was segmental. We conclude that epidural narcotics in adequate dosage are an effective means for production of prolonged and segmental postoperative analgesia.

In vitro release of endothelium-derived relaxing factor by acetylcholine is increased during the guinea pig pregnancy

The relaxation of isolated blood vessels by acetylcholine is dependent on the presence of intact endothelium and its release of a smooth muscle relaxing nitroso-like compound. Pregnancy is associated with altered vascular responsiveness to a variety of agents. Because many of these agents stimulate the release of endothelium-derived relaxing factor, we investigated in vitro the effect of pregnancy on acetylcholine-mediated relaxation of guinea pig uterine and carotid artery rings. The presence of intact and functional endothelium was confirmed both by examination under the scanning electron microscope and by vessel relaxation after the addition of acetylcholine. The addition of acetylcholine to the vessel bath produced dose-dependent relaxation of both carotid and uterine artery segments obtained from pregnant and nonpregnant animals after they had been submaximally preconstricted with phenylephrine. There was a significant increase in both response and efficacy to acetylcholine during pregnancy for both uterine and carotid arteries (p less than 0.0001 for each). The concentrations of endothelial cells (cells per square micrometer) were similar in uterine arteries from pregnant and nonpregnant animals. We conclude that the most likely explanation for these findings is a pregnancy-mediated enhancement of endothelium-derived relaxing factor activity.

Comparison of two oxytocin regimens to prevent uterine atony at cesarean delivery: a randomized controlled trial.

OBJECTIVE To determine if high‐dose oxytocin reduces the need for additional uterotonic agents at cesarean. METHODS A randomized, double‐masked trial of two oxytocin regimens was performed to prevent postpartum uterine atony in laboring women. The pharmacy prepared sequentially numbered oxytocin solutions containing either 10 U/500 mL or 80 U/500 mL of lactated Ringers solution infused over 30 minutes after cord clamping. The need for additional uterotonic agents was determined by the surgical team. Hypotension was diagnosed and treated with crystalloid or a pressor agent. To detect a 50% decrease in the need for additional uterotonic agents and considering a βerror of 0.2, 220 patients would be required in each group (α = 0.05, two‐tailed χ2 test). RESULTS The low‐dose group (n = 163) received 333 mU/min, and the high‐dose group (n = 158) received 2667 mU/min of oxytocin. The groups were similar with respect to risk factors for atony. Women in the low‐dose group received additional uterotonic medication significantly more often than those in the high‐dose group (39% compared with 19%, P < .001, relative risk 2.1, 95% confidence interval 1.4, 3.0). Moreover, more women in the low‐dose group received methylergonovine, 15‐methyl prostaglandin F2α or both (9% compared with 2%, relative risk 4.8, 95% confidence interval 1.4, 16) after additional oxytocin (median 20 U) had been added to the study solution. The incidence of hypotension was similar in both groups. CONCLUSION Compared with an infusion rate of 333 mU/min, oxytocin infused at 2667 mU/min for the first 30 minutes postpartum reduces the need for additional uterotonic agents at cesarean delivery.

Anesthetic management for obstetric hysterectomy: A multi-institutional study

A prospectively designed review of all obstetric hysterectomies performed in five university hospitals between November 1, 1984 and October 31, 1987 has been performed. There were 41,107 deliveries and 46 obstetric hysterectomies, an incidence of 0.11%. Twenty-five hysterectomies were elective and 21 were emergent. The indication for 11 of the 21 emergency hysterectomies was placenta previa and/or accreta. Women in the emergency group had greater intraoperative blood loss, were more likely to have intraoperative hypotension, and were more likely to receive donor blood than women in the elective group (P less than 0.05). Twelve patients (eight from the elective group and four from the emergency group) received continuous epidural anesthesia, and none required intraoperative induction of general anesthesia. There was no evidence that epidural anesthesia significantly affected blood loss, crystalloid replacement, or requirement for transfusion in the elective group. Abnormal placentation now represents a major indication for emergency obstetric hysterectomy. Furthermore, significant hemorrhage is more likely with emergency obstetric hysterectomy than with elective hysterectomy. Finally, elective cesarean hysterectomy is not a contraindication to performance of continuous epidural anesthesia.

Effect of pregnancy on uterine and carotid artery response to norepinephrine, epinephrine, and phenylephrine in vessels with documented functional endothelium

The effect of pregnancy on arterial sensitivity to vasoconstrictors is controversial. Some of the controversy may reflect methodologic differences. Vessel reactivity in vitro is altered by both the tension placed on the segment and the presence or absence of functional endothelium. We investigated the effect of pregnancy on guinea pig uterine and carotid arteries to norepinephrine, epinephrine, and phenylephrine. Each vessel segment was stretched to the optimal point along its length-tension curve, and functional endothelium was documented by acetylcholine-stimulated relaxation. A significant dose-response relationship was observed in each vessel for each agent (each p less than 0.0001). Pregnancy was demonstrated to be associated with a significant reduction in both uterine artery response and sensitivity to norepinephrine, epinephrine, and phenylephrine. However, there was no consistent pregnancy-associated effect on carotid artery response and sensitivity.

RESPIRATORY FAILURE ASSOCIATED WITH AMNIOINFUSION DURING LABOR

Saline amnioinfusion is a method to enlarge the amniotic cavity to relieve umbilical cord compression responsible for variable decelerations in fetal heart rate (14). Recently, amnioinfusion has been performed to dilute thick meconium to reduce the deleterious effects of fetal meconium aspiration (5,6). To our knowledge, there is no published report of a serious complication during amnioinfusion. We report the case of a patient who experienced acute respiratory failure during saline amnioinfusion.

Magnesium sulfate adversely affects fetal lamb survival and blocks fetal cerebral blood flow response during maternal hemorrhage.

Magnesium sulfate is commonly used in high-risk pregnancies, even though its actions in the fetus during maternal/fetal stress are not completely understood. The present study tested the hypothesis that magnesium sulfate alters the fetal cerebral blood flow response to hypoxemia produced during maternal hemorrhage. It was conducted in instrumented near-term fetal lambs at 123 days of gestation. Experimental treatment involved four periods of maternal hemorrhage over a 60-min period during fetal infusion of 0.25 g (n = 5) or 0.30 g (n = 6) magnesium sulfate, or normal saline (n = 11). The level of fetal cerebral blood flow was determined using radiolabeled microspheres. For all three treatment groups, maternal hemorrhage produced fetal hypoxemia and some fetal demise. During fetal infusion of saline, 1 of 11 (9%) of the fetuses died; with the 0.25-g magnesium sulfate regimen, 1 of 5 (20%) died; and with the 0.30-g magnesium sulfate regimen, 3 of 6 (50%) of the fetuses died. Magnesium sulfate caused an increase in the proportion of fetal death produced by maternal hemorrhage (P < 0.05). Among surviving fetuses, hemorrhage-induced hypoxemia increased fetal cerebral blood flow during saline infusion. In contrast, infusion of magnesium sulfate had an inhibitory effect on this compensatory increase in fetal cerebral blood flow (P = 0.003). These data indicate that, in the sheep, magnesium sulfate increases fetal mortality and inhibits the compensatory increase in fetal cerebral blood flow during maternal hemorrhage-induced fetal hypoxemia. (Anesth Analg 1996;83:493-9)

Influence of umbilical vein administration of oxytocin on the third stage of labor: A randomized, double-blind, placebo-controlled study

A randomized, double-blind, placebo-controlled study evaluated the influence of umbilical vein administration of oxytocin on the third stage of labor. Five minutes after delivery, 37 women received 10 units of oxytocin diluted in physiologic saline solution to a total volume of 20 ml; 41 women received 20 ml of saline solution alone. There was no significant difference between groups in mean (+/- SD) injection-placental expulsion interval (9 +/- 7 versus 10 +/- 8 minutes).

Tubal versus uterine transfer of cryopreserved embryos: a prospective randomized trial

OBJECTIVE To compare pregnancy rates after fallopian tubal and uterine transfer of cryopreserved embryos. DESIGN Prospective randomized trial with assignment to treatment groups by a random number table. SETTING University of Iowa Hospitals and Clinics, a tertiary care academic institution. PATIENTS Forty patients with patent fallopian tubes and at least three cryopreserved embryos. INTERVENTIONS Cryopreserved embryos were thawed and transferred to the fallopian tube by laparoscopy or to the uterus by a transcervical catheter. MAIN OUTCOME MEASURES Clinical and ongoing pregnancy rates. RESULTS Tubal transfer of cryopreserved embryos resulted in statistically higher clinical (68% versus 24%) and ongoing pregnancy rates (58% versus 19%) when compared with uterine transfer. CONCLUSIONS Tubal transfer of cryopreserved embryos is highly effective and offers an improved pregnancy rate when compared with uterine transfer of embryos. This method of transfer should be considered in patients with patent fallopian tubes and at least three cryopreserved embryos.

Pregnancy in a patient with a history of myocardial infarction and coronary artery bypass grafting

A 37-year-old woman conceived after experiencing a myocardial infarction and undergoing three-vessel aortocoronary artery bypass grafting. Pregnancy was complicated by angina, which was successfully treated with propranolol and bed rest. At term the patient underwent vaginal delivery, without evidence of intrapartum myocardial ischemia or failure.