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Biomedical subjects

J C Morrison

Publications and source records attributed to J C Morrison.

At least 19 recordsLinked to original sources

Vaginal birth after cesarean delivery: are there useful and valid predictors of success or failure?

OBJECTIVE: Before parturition are there useful and valid predictors of successful or unsuccessful vaginal birth after previous cesarean birth that could be used to enhance the obstetric care of a patient and her pregnancy? STUDY DESIGN: The clinical course and outcome of all patients who attempted vaginal birth after cesarean delivery at one level III center during 1989 were evaluated to identify factors prognostic of a successful or unsuccessful patient group; use of this information in stepwise logistic regression and cluster analysis was disappointing. RESULTS: No single criterion or optimal clusters of factors were found and no equation achieved greater than 75% predictability of outcome with acceptable sensitivity and specificity. CONCLUSIONS: Before parturition prediction of outcome of vaginal birth after cesarean delivery is tenuous regardless of past obstetric history or recent clinical parameters. Thus it seems appropriate to encourage a trial of labor in almost all patients with a prior low-segment uterine incision (transverse or vertical) unless there is a strong physician or patient-derived contraindication to such an undertaking.

Body Weight

Measurement of amniotic fluid volume: accuracy of ultrasonography techniques.

OBJECTIVE: Our purpose was to determine amniotic fluid volume by the dye-dilution technique and compare it with the amniotic fluid index, largest vertical pocket, and two-diameter pocket (defined as vertical x horizontal of the largest vertical pocket). STUDY DESIGN: This prospective study involved 40 women undergoing amniocentesis in late pregnancy to detect fetal lung maturity or evidence of chorioamnionitis. The amniotic fluid volume was quantified ultrasonographically by means of the amniotic fluid index, largest vertical pocket, and two-diameter pocket. During amniocentesis the fluid volume was calculated by the dye-dilution technique of Charles and Jacoby. RESULTS: Ultrasonographic measurements by amniotic fluid index, largest vertical pocket, and two-diameter pocket correctly predicted normal amniotic fluid and hydramnios (74%). A new measurement, two-diameter pocket, gave a significantly more accurate estimate of oligohydramnios than did amniotic fluid index (p < 0.002) or largest vertical pocket (p < 0.0003). CONCLUSION: All three indices are moderately accurate in identifying normal amniotic fluid volume and hydramnios. Two-diameter pocket is the most accurate test to predict oligohydramnios.

Adolescent

Oral magnesium and the prevention of preterm labor in a high-risk group of patients.

OBJECTIVE: The null hypothesis of this study is that treatment with oral magnesium gluconate 1 gm four times daily will not decrease the rate of preterm labor and delivery in a high-risk group of pregnant women. STUDY DESIGN: Fifty-four women at risk for preterm delivery were selected randomly to receive magnesium gluconate 1 gm orally four times daily or placebo. These women were monitored prospectively for signs and symptoms of preterm labor. A subgroup of 31 women also received a home uterine activity monitor. The serum magnesium level was measured initially and again 2 weeks after study enrollment. The data were analyzed with Fisher's exact test and analysis of variance. RESULTS: Preterm labor developed in 15 women in the placebo group and in 16 women in the magnesium group. There were no differences in birth weight or gestational age at delivery. The mean increase in serum magnesium level while the patients were taking magnesium gluconate was 0.10 mg/dl (p = not significant). Five women did not have an increase in serum magnesium level and preterm labor developed in all of them. CONCLUSION: Magnesium gluconate in a dose of 1 gm four times daily is not effective for preventing preterm delivery in a high-risk group of patients.

Administration, Oral

Interval to delivery in high-risk patients: do tocolytic agents really work?

Some question whether tocolytic drugs reduce uterine activity and prolong gestation. The interval from discontinuance of tocolytics until spontaneous labor and delivery in patients (n = 69) with documented preterm labor (PTL) versus subjects receiving prophylactic tocolytic therapy (n = 41) was studied. Women with documented PTL delivered sooner after cessation of tocolytics (6.1 +/- 6.9 days) than control (C) patients (14.7 +/- 10.8 days, P less than 0.001). Also, 28 of the 69 (41%) patients in the PTL group delivered within 24 h of discontinuation of tocolysis compared to 4 (10%) in the C group (P less than 0.0004). We conclude that tocolytic therapy for documented preterm labor suppresses uterine activity and when these agents are discontinued, contractions return and labor ensues.

Adult

Adjunctive antibiotic treatment of women with preterm rupture of membranes or preterm labor.

Subclinical infection is associated with preterm rupture of the membranes (PROM) and preterm labor (PTL) in many cases. It was hypothesized that antibiotic treatment might delay delivery and/or decrease infectious morbidity in those with PROM or PTL. Patients from 19 to 34 weeks with PROM and no labor or PTL with intact membranes (but not both) were separately randomized to receive ampicillin versus placebo in addition to usual therapy. There were 36 women with PTL (21 ampicillin/15 placebo) and 84 with preterm PROM (41 ampicillin/43 placebo). Demographically, the treatment and placebo groups were similar. Outcome variables analyzed included delivery delay after treatment, maternal chorioamnionitis/endometritis, Apgar score, neonatal infection, or respiratory distress, and hospital stay. There were no significant differences between the ampicillin and placebo groups in those with PTL or preterm PROM as it concerned outcome parameters. Adjunctive ampicillin used for treatment of idiopathic PTL or preterm PROM was not beneficial in this study.

Adult

Subcutaneous tocolytic infusion therapy for patients at very high risk for preterm birth.

Patients with multiple gestations or recalcitrant preterm labor are at very high risk for preterm birth in spite of adequate tocolysis. Subcutaneous infusion of tocolytic medications on an ambulatory basis has been used in several small series and has effectively prolonged gestation. This retrospective analysis presents data from 992 patients at very high risk for preterm delivery who were prescribed this therapy. The amount of tocolytic medication was individualized by utilizing the patient's volume of distribution and clearance. Pharmacists adjusted the dosage based on uterine activity strips received by nursing personnel. The average basal rate was .073 +/- .020 mg/h. Patients received an average of seven scheduled boluses per day and 1.54 +/- .93 unscheduled boluses per week (.25 +/- .03 mg each). The therapy extended the gestation a mean of 38 +/- 23 days and average gestational age at delivery was 36.3 +/- 2.6 weeks with a mean birthweight of 2759 +/- 681 g. This study, utilizing a large number of patients, confirms earlier reports that for women at very high risk for preterm delivery subcutaneous tocolytic infusion therapy is beneficial. Prospective studies evaluating such treatment on a randomized basis are indicated.

Adrenergic beta-Agonists

The diagnosis and management of dystocia of the shoulder.

Dystocia of the shoulder is an unpredictable obstetric emergency that may result in injury to the mother or fetus. In an effort to reduce such risks, attempts have been made to identify patients having a fetus who may subsequently develop shoulder dystocia. The literature, however, clearly reflects that even the combination of prenatal historic facts, estimated fetal weight and sequence of intrapartum events is ineffective in prospectively identifying infants whose births are complicated by shoulder dystocia. During a ten year period at the University of Mississippi Medical Center, the incidence of macrosomia, shoulder dystocia and subsequent brachial plexus injury was reviewed. The majority of instances (89 percent) of shoulder dystocia occurred in patients weighing less than 8 pounds 13 ounces at birth. In the current retrospective review, only 11 percent of the women had risk factors for macrosomia or shoulder dystocia and among these, none were identified prospectively. Additionally, 91 percent of patients with brachial plexus injury recovered with no sequelae. One instance of brachial plexus injury occurred at the time of cesarean section. These data reveal that macrosomia and subsequent shoulder dystocia cannot be predicted. Therefore, it is not feasible to prevent brachial plexus injury prospectively by prophylactic cesarean section. Great clinical acumen and technical expertise by the obstetrician using a variety of methods may be useful in avoiding, as much as possible, injury to the mother and fetus when shoulder dystocia does occur.

Birth Weight

Prophylactic intrapartum amnioinfusion for patients with oligohydramnios. A prospective randomized study.

This prospective study evaluated whether prophylactic saline amnioinfusion among patients with amniotic fluid index (AFI) < or = 5.0 cm decreases the incidence of adverse fetal outcomes. Randomization of 53 patients with decreased AFI at term, resulted in 21 patients' receiving prophylactic saline amnioinfusion early in labor, prior to development of an abnormal fetal heart rate tracing. For the treatment group the mean AFI on admission was 3.0 cm, and the postamnioinfusion AFI was 8.9 cm. For 32 comparison (noninfusion) patients, the mean AFI was 2.9 cm; the group consisted of 17 patients randomized to receive no amnioinfusion (control group) and 15 patients who refused to participate in the study. There was no statistically significant difference between the amnioinfused and nonamnioinfused patients with regard to age, parity, gestational age, AFI at admission or duration of first or second stage of labor. Amnioinfusion resulted in no statistically significant reduction in the incidence of recurrent variable decelerations/bradycardia (26.3% vs. 46.6%), intrapartum resuscitation with terbutaline (5.2% vs. 10.0%), cesarean section for fetal distress (9.5% vs. 9.3%), fetal-acidosis (10.5% vs. 12.0%) or Apgar scores < 7 at five minutes (5.2% vs. 0%) in patients with oligohydramnios.

Amniotic Fluid

Neurologic diseases in pregnancy.

Although most neurologic problems require conservative management, such as headaches and nerve compression syndromes, other demand aggressive treatment, such as plasmapheresis in Guillain-Barré syndrome and prompt surgery in those patients with hemorrhagic strokes secondary to a ruptured aneurysm or arteriovenous malformation. Myasthenia gravis, discussed in the autoimmune disease section, and epilepsy are associated with congenital anomalies, whereas the progeny of patients with multiple sclerosis are at a much greater risk than the general population of contracting this disease. Therefore, knowledge of these risks is essential in providing quality preconceptional counseling. Pregnancy provides many physiologic changes that alter the course of preexisting neurologic conditions as well as increasing the risks and morbidity of other diseases. It is for this reason that a cooperative team effort, including the obstetrician, neurologist, and, if needed, the neurosurgeon, is essential for an optimal outcome.

Cerebrovascular Disorders

Hematologic disorders in pregnancy.

Hematologic disorders in pregnancy are relatively common and encompass a wide spectrum of clinical conditions. The treatment and obstetric management of the majority of these diseases are well established, although controversy exists in areas such as sickle cell disease and ITP. Once the diagnosis of a specific disorder is confirmed, therapy is directed toward improved perinatal outcome. Recent advances in prenatal diagnostic techniques make in utero diagnosis feasible for most of the inherited disorders and aid in genetic counseling.

Anemia

Pathfinder direct fluorescent antigen test for diagnosing maternal chlamydial infections. An evaluation.

Chlamydia trachomatis is a frequent cause of genital infections in young women. Chlamydial infections may adversely affect perinatal outcome. We compared the Pathfinder direct fluorescent antigen (DFA) test for chlamydial infections to tissue culture isolation in an obstetric population. Among 984 samples, 152 (15.4%) were inadequate for evaluation using the Pathfinder DFA test. Among 783 evaluable specimen pairs, the sensitivity, specificity, and positive and negative predictive values of the Pathfinder, as compared to tissue culture isolation, were 25%, 97.5%, 32.1% and 96.4%, respectively. On the basis of that experience, we do not recommend the Pathfinder DFA test as a clinical screening device for detecting chlamydial infections complicating pregnancy.

Chlamydia Infections

Intrapartum clinical, sonographic, and parous patients' estimates of newborn birth weight.

The accuracy of estimating birth weight clinically, sonographically (using femur length and abdominal circumference), and by maternal prediction was studied prospectively in 106 term parous women who were in active labor. Estimates of birth weight by these women had lower standardized error (86.8 +/- 78.0 g/kg) than either clinical estimates (90.2 +/- 84.8 g/kg) or sonographically derived estimates (155.8 +/- 118.0 g/kg) of birth weight (P = not significant). Maternal estimates of birth weight were within +/- 10% of the actual weight in 69.8%, compared with 66.1% for clinical estimates and 42.4% for sonography. A term parous woman in labor can predict the birth weight with accuracy comparable to a clinical estimation by a physician or a sonographic estimate based on infant measurements.

Adult

Optic nerve head microvasculature of the rabbit eye.

Vascular luminal castings of rabbit eyes were microdissected and studied with scanning electron microscopy to elucidate the three-dimensional angioarchitecture of the optic nerve head. Using sequential microdissection, an incomplete arterial circle was identified as terminal branches of two to three short posterior ciliary arteries around the optic nerve head. Several recurrent branches from the arterial circle form a pial arterial network. This pial system supplies the optic nerve head microvasculature and receives numerous venules from them. The only large vessel to enter the optic nerve is a central retinal artery that has few branches within the optic nerve and provides several branches at the surface of the optic disc. Moderately numerous vessels connect the retinal and ciliary vascular layers within the optic nerve head. Few arterioles to the optic nerve head arise from the choroid; however, there are a small number of capillary and numerous venous connections between them. These results indicate that the principal blood supply of the rabbit optic nerve head is derived from the short posterior ciliary arteries by the arterial circle. The retinal arteries contribute to the surface vasculature of the optic nerve head. The pial system also plays a significant role in both supply and drainage of the rabbit optic nerve head.

Animals

Use of continuous flow erythrocytapheresis in pregnant patients with sickle cell disease.

The role of partial prophylactic red cell exchange transfusion in the management of pregnant patients with major sickle hemoglobinopathies is unclear. Over a 10-year period, 131 pregnant patients with major hemoglobinopathies (HbS 101, HbS-C 30) were managed by the same group of physicians. Of these, 103 received partial prophylactic exchange transfusion early during prenatal care while 28 received blood only when serious complications developed (control group). Patients treated with exchange transfusion received continuous flow erythrocytapheresis on an outpatient basis. The results indicate that there were fewer crises (P = .0001), a reduction in other significant medical complications (P = .002), and a decrease in maternal hospital days (P = .05) in those receiving prophylactic transfusions compared to women in the control group. The number of preterm deliveries (P = .004), the prevalence of low birthweight infants (P = .01), and the perinatal death rate (P = .01) were significantly lower among those who were routinely transfused. Two patients developed hepatitis, five had transfusion reactions, and 11 were found to have alloantibodies among those receiving prophylactic transfusions versus one, two, and five patients, respectively, in the control group. The results indicate a benefit of this methodology in the treatment of pregnant sickle cell patients in our population. However, a national collaborative randomized study is needed to adequately address the controversy regarding the use of red cell exchange in the pregnant sickler.

Adolescent

Effect of pregnancy on the accuracy of light-reflection rheography.

Light-reflection rheography is a noninvasive method to detect venous obstruction by indirectly measuring venous emptying time. In nonpregnant women it has greater than 90% sensitivity when compared with venography but has not been tested during gestation. To determine if the nonthrombotic occlusion of venous outflow by the pregnant uterus might alter the performance of light-reflection rheography, we examined 17 normal patients with a vascular Accuscan (Hemodynamics, Inc., Boca Raton, Fla.) in the third trimester of pregnancy and 11 patients during the early second trimester. These results were compared with the defined normal (nonpregnant) rate of venous emptying (slope 0.54 +/- 0.06). The mean (+/- SD) for the entire sample was 0.58 +/- 0.23 mm/sec in the right leg and 0.52 +/- 0.19 mm/sec in the left leg measured in the standard sitting position (p = 0.21). The results did not vary with gestational age. A subset of patients in late pregnancy were used to compare the effect of various positions (supine, lateral decubitus, and sitting) on test performance. Positions other than sitting provided results that were inconsistent. It appears that the large pregnant uterus does not significantly obstruct venous outflow from the lower extremities in the standard sitting position; thus the results of light-reflection rheography are not affected. Comparison of light-reflection rheography versus venography in pregnant patients with suspected venous thrombosis is being investigated.

Female