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Biomedical subjects

J C Morrison

Publications and source records attributed to J C Morrison.

At least 37 records · Page 2Linked to original sources
PubMed2000

A prospective, randomized, controlled trial of high and low maintenance doses of magnesium sulfate for acute tocolysis.

OBJECTIVE: This study was undertaken to compare a high-dose protocol for magnesium sulfate tocolytic therapy with a low-dose regimen with respect to time needed to achieve tocolysis. STUDY DESIGN: Patients between 24 and 34 weeks' gestation with preterm labor were included. Patients with ruptured membranes or nonreassuring fetal assessments were excluded. Gravid women received a 4-g loading dose of magnesium sulfate and were prospectively randomly assigned to receive a maintenance dose of 2 or 5 g/h. RESULTS: The median times to tocolysis were 120 minutes (semi-interquartile range, 30 minutes) in the low-dose group and 90 minutes (semi-interquartile range, 28 minutes) in the high-dose group (P <.001). CONCLUSION: Patients treated with a higher maintenance dose of magnesium sulfate had a higher frequency of side effects; however, tocolysis was achieved more rapidly and they required shorter admissions to the labor and delivery unit without increased maternal or neonatal morbidity.

Adult↗
PubMed2000

Determination of amniotic fluid volume in twin pregnancies: ultrasonographic evaluation versus operator estimation.

OBJECTIVE: We sought to determine the accuracy of amniotic fluid volume estimation (visually) in diamniotic twin pregnancy versus ultrasonography techniques. STUDY DESIGN: In this prospective study the volume of each sac in 23 sets of diamniotic twin pregnancies was subjectively and objectively estimated by a second-year obstetric resident, nurse sonographer, maternal-fetal medicine fellow, and maternal-fetal medicine staff. The actual volume was confirmed by amniocentesis and a dye-dilution technique. RESULTS: There was no difference in the total number of correct estimates of volume by level of operator experience (P =.98), ultrasonography technique (P =.87), or combined subjective versus objective correct estimates (P =.87). Identification of low volume was not different among the four evaluators (P =.48), but the percentage of correct estimates was poor (7%-29%). The 2-diameter pocket was a better predictor of oligohydramnios (57%) than the amniotic fluid index or the largest vertical pocket (12.5%; P =.002). CONCLUSION: The extremes of volume (low or high) are poorly identified by the subjective or objective assessment of volume.

Adult↗
PubMed2000

Chronology of optic nerve head and retinal responses to elevated intraocular pressure.

PURPOSE: To determine the chronology of optic nerve head and retinal responses to elevated intraocular pressure (IOP). METHODS: After 1 to 39 days of unilaterally elevated IOP, experimental and fellow rat eyes were examined for morphology and immunohistochemical labeling alterations and for ganglion cell DNA fragmentation. RESULTS: Mean IOP for the experimental eyes was 36 +/- 8 mm Hg, an approximately 15-mm Hg elevation above normal values. By 7 days of pressure elevation above 40 mm Hg, endogenous immunostaining for brain-derived neurotrophic factor and neurotrophin 4/5 was absent from the nerve head and superior retina, whereas normal labeling was present in the inferior retina and distal optic nerve of these same eyes. These changes were preceded by a loss of gap junctional connexin43 labeling and astrocytic proliferation in the nerve head and by increased retinal ganglion cell layer apoptosis in the retina. Nerve head depletion of neurotrophins coincided with evidence of axonal degeneration, loss of astrocytic glial fibrillary acidic protein staining, and spread of collagen VI vascular immunolabeling. After longer durations at these same pressures, neurotrophin labeling returned to nerve head glia and scattered retinal ganglion cells. CONCLUSIONS: Optic nerve head and retinal responses, including the depletion of endogenous neurotrophins, are readily identified in the rat eye after experimental IOP elevation. However, the apparent chronology of these responses suggests that the withdrawal of neurotrophic support was not the only determinant of retinal ganglion cell apoptosis and axonal degeneration in response to pressure.

Animals↗
PubMed2000

Sonographic measurements of fetal parts to predict pulmonary maturity among twins and singletons.

To determine if sonographic examination of fetus can be readily utilized to predict a mature lecithin/sphingomyelin (L/S) ratio among twins and singletons. Twins (n = 36) undergoing amniocentesis for assessment of pulmonary maturity were matched with singleton (1:2) for maternal demographics, gestational age (GA), and indications for procedure. At the time of amniocentesis, twins and singletons with mature L/S ratios differed significantly in mean GA (33.2 +/- 2.7 vs 34.5 +/- 4.6 wks, p = 0.01), biparietal diameter (BPD), abdominal circumference (AC), femur length (FL) and estimate of birth weight (EFW). Based on ten receiver operating characteristics curves constructed, the following diagnostic thresholds predicted a mature L/S ratio with a true positive rate of 100% among twins and singletons, respectively: 1) BPD $84 and $92 mm; 2) head circumference $315 and $320 mm; 3) AC $295 and $350 mm; or 4) FL $64 and $72 mm; or 5) EFW $2400 and $3200 g. Using any one of these five criteria correctly identified pulmonary maturity among 59% of twins and 28% of singletons (p = 0.001). Sonographic measurement of fetal parts or EFW may be a noninvasive method to predict a mature L/S ration among twins as well as singletons.

Adult↗
PubMed2000

Patterns of intraocular pressure elevation after aqueous humor outflow obstruction in rats.

PURPOSE: To determine the diural intraocular pressure (IOP) response of Brown Norway rat eyes after sclerosis of the aqueous humor outflow pathways and its relationship to optic nerve damage. METHODS: Hypertonic saline was injected into a single episcleral vein in 17 animals and awake IOP measured in both the light and dark phases of the circadian cycle for 34 days. Mean IOP for light and dark phases during the experimental period were compared with the respective pressures of the uninjected fellow eyes. Optic nerve cross sections from each nerve were graded for injury by five independent masked observers. RESULTS: For fellow eyes, mean light- and dark-phase IOP was 21 +/- 1 and 31 +/- 1 mm Hg, respectively. For four experimental eyes, mean IOPs for both phases were not altered. Six eyes demonstrated significant mean IOP elevations only during the dark phase. Of these, five showed persistent, large circadian oscillations, and four had partial optic nerve lesions. The remaining seven eyes experienced significant IOP elevations during both phases, and all had extensive optic nerve damage. CONCLUSIONS: Episcleral vein injection of hypertonic saline is more likely to increase IOP during the dark phase than the light. This is consistent with aqueous outflow obstruction superimposed on a circadian rhythm of aqueous humor production. Because these periodic IOP elevations produced optic nerve lesions, both light- and dark-phase IOP determinations are necessary for accurate correlation of IOP history to optic nerve damage in animals housed in a light- dark environment.

Animals↗
PubMed2000

Effect of general anesthetics on IOP in rats with experimental aqueous outflow obstruction.

PURPOSE: To determine the effect of several common general anesthetics on intraocular pressure (IOP) after experimental aqueous outflow obstruction in the rat. METHODS: A single episcleral vein injection of hypertonic saline was used to sclerose aqueous humor outflow pathways and produce elevated IOP in Brown Norway rats. Animals were housed in either standard lighting or a constant low-level light environment. Awake IOPs were determined using a TonoPen (Mentor, Norwell, MA) immediately before induction of anesthesia by either isoflurane, ketamine, or a mixture of injectable anesthetics (xylazine, ketamine, and acepromazine). For each anesthetic, IOPs were measured immediately after adequate sedation (time 0) and at 5-minute intervals, up to 20 minutes. RESULTS; Awake IOPs ranged from 18 to 52 mm Hg. All anesthetics resulted in a statistically significant (P: < 0.01) reduction in measured IOP at every duration of anesthesia when compared with the corresponding awake IOP. With increasing duration of anesthesia, measured IOP decreased approximately linearly for both the anesthetic mixture and isoflurane. However, with ketamine, IOP declined to 48% +/- 11% (standard lighting) and 60% +/- 7% (constant light) of awake levels at 5 minutes of anesthesia, where it remained stable. In fellow eyes, the SD of the mean IOP in animals under anesthesia was always greater than the corresponding SD of the awake mean. Anesthesia's effects in normal eyes and eyes with elevated IOP were indistinguishable. CONCLUSIONS: All anesthetics resulted in rapid and substantial decreases in IOP in all eyes and increased the interanimal variability in IOPs. Measurement of IOP in awake animals provides the most accurate documentation of pressure histories for rat glaucoma model studies.

Acepromazine↗
PubMed1999

Antenatal testing among 1001 patients at high risk: the role of ultrasonographic estimate of amniotic fluid volume.

OBJECTIVE: Our goal was to compare the accuracy of the amniotic fluid index and the 2-diameter pocket technique with respect to accuracy in predicting an adverse pregnancy outcome among patients at high risk undergoing antenatal testing. STUDY DESIGN: All women with high-risk pregnancies and intact membranes who underwent antenatal testing during an 18-month period were prospectively enrolled. Ultrasonographic estimates of amniotic fluid volume were performed by means of the amniotic fluid index and the 2-diameter pocket technique. Relative risks with 95% confidence intervals and receiver operator characteristic curves were calculated for patients with an ultrasonographic estimate of oligohydramnios (amniotic fluid index of </=5 cm or 2-diameter pocket of </=15 cm2) versus normal fluid level (amniotic fluid index of >5 cm or 2-diameter pocket of >15 cm2). Outcome variables studied were intrapartum and neonatal complications. RESULTS: Among 1001 patients the mean (+/-SD) amniotic fluid index was 10.5 +/- 5 cm and the mean (+/-SD) 2-diameter pocket was 18.7 +/- 13.6 cm2. Significantly more patients (46%) were considered to have oligohydramnios according to the 2-diameter pocket criteria than according to the amniotic fluid index (21%, P <.0001, relative risk 1.7, 95% confidence interval 1.5-1.8). No significant differences in the incidences of nonreactive nonstress test results, meconium-stained amniotic fluid, cesarean delivery for fetal distress, low Apgar scores, or infants with cord pH of <7.10 were observed between the oligohydramnios and normal amniotic fluid groups (P >.05) when assessed by relative risk with confidence interval and by receiver operator characteristic curves. CONCLUSIONS: Current ultrasonographic measurements with the amniotic fluid index and the 2-diameter pocket technique are poor diagnostic tests to determine whether a patient is at high risk for an adverse perinatal outcome.

Adult↗
PubMed1999

Does an amniotic fluid index of </=5 cm necessitate delivery in high-risk pregnancies? A case-control study.

OBJECTIVE: This study was undertaken to determine whether women with high-risk pregnancies and an amniotic fluid index of </=5 cm require labor induction to prevent adverse perinatal outcomes. STUDY DESIGN: All women at high risk at >/=34 weeks' gestation with an amniotic fluid index of </=5 cm were admitted to the hospital for labor induction. Each woman was compared with the next patient at high risk seen with an amniotic fluid index of >5 cm and the same pregnancy complication. Case patients were also matched with control subjects for maternal race, age, parity, and gestational age. RESULTS: Prospectively, 79 women at high risk with an amniotic fluid index of </=5 cm were compared with 79 control subjects. There were no statistically significant differences between the 2 groups in the risks of thick meconium (P =.29), variable decelerations (moderate P =.27, severe P =.37), amnioinfusion (P =.37), cesarean delivery for fetal distress (P =.4), and umbilical artery pH <7.10 (P =.29). CONCLUSION: High-risk pregnancies with an amniotic fluid index of </=5 cm appear to carry intrapartum complication rates similar to those of similar high-risk pregnancies with an amniotic fluid index of >5.

Adult↗
PubMed1999

Planned cesarean hysterectomy: A preferred alternative to separate operations.

OBJECTIVE: The aim of this study was to evaluate our institutional experience with planned cesarean hysterectomy. STUDY DESIGN: In this retrospective case-control investigation of a 16-year experience, 100 pregnant women who underwent planned cesarean hysterectomy were compared with 37 patients who underwent cesarean delivery followed by a hysterectomy performed within 6 months. RESULTS: Women undergoing planned cesarean hysterectomy did not have any demonstrable increase in intraoperative or postoperative complications when compared with the cesarean delivery plus later hysterectomy group. Primarily as a result of significantly reduced hospital stay and shorter total operative time, there was a significant financial advantage associated with a single planned cesarean hysterectomy with respect to separate operations. CONCLUSIONS: A policy to undertake planned cesarean hysterectomy for carefully selected patients appeared to produce advantages without increasing risks for these patients. Secondarily, it provided resident physicians the opportunity to learn the operation with supervision and under controlled circumstances.

Adult↗
PubMed1999

Evaluation of fetal lung maturity in diamniotic twins.

OBJECTIVE: This study was undertaken to evaluate the correspondence in fetal lung development between diamniotic twins. STUDY DESIGN: Lecithin/sphingomyelin ratios were determined for amniotic fluid specimens collected from each sac in 58 diamniotic twin pregnancies. RESULTS: Overall, the lecithin/sphingomyelin ratios of twin A and twin B and those of the larger and smaller twins of each pair were closely correlated (r >/= 0.83, P <.001). When stratified by gestational age, however, the percentage disparity in lecithin/sphingomyelin ratios between members of twin pairs was significantly greater at </=32 weeks' gestation (25%) than at >32 weeks' gestation (15%, P =.027). An analysis of the lecithin/sphingomyelin ratios of twins with a large lecithin/sphingomyelin ratio disparity (>/=20%) suggested that this disparity was a result of 1 twin having a lecithin/sphingomyelin ratio that was advanced for gestational age with respect to that of the co-twin. Disparities in lecithin/sphingomyelin ratio were not significantly affected by fetal sex or by discordance in size between the twins. CONCLUSION: At relatively early stages of diamniotic twin gestation (</=32 weeks' gestation), lecithin/sphingomyelin ratios should be obtained for both amniotic sacs to ensure accurate assessment of fetal lung maturity in both twins.

Amniocentesis↗
PubMed1999

Oral nicardipine versus intravenous magnesium sulfate for the treatment of preterm labor.

OBJECTIVE: The aim of this study was to compare the efficacy and safety of oral nicardipine in acute therapy for preterm labor with those of parenteral magnesium sulfate. STUDY DESIGN: Patients between 24 and 34 weeks' gestation with documented preterm labor were randomly assigned to receive oral nicardipine (n = 57) or intravenous magnesium sulfate (n = 65) as initial tocolytic therapy. Patients in the nicardipine group received a 40-mg loading dose and then 20 mg every 2 hours as needed to stop contractions (total 80 mg). Patients in the magnesium sulfate group received a 6-g bolus followed by 2 to 4 g/h to provide uterine quiescence. Patients could be switched to another tocolytic regimen if they continued to have contractions after 6 hours of therapy. The main outcome variables examined were time to uterine quiescence, time gained in utero, recurrence of preterm labor, failure of tocolysis, and pertinent maternal and neonatal outcomes. RESULTS: There were no significant differences in maternal demographic characteristics between the groups. Among patients who responded with uterine quiescence within 6 hours, there was a significant decrease in the time to uterine quiescence in the nicardipine group (P <.01). Patients in the magnesium sulfate group were more likely to have recurrence of preterm labor necessitating further tocolytic attempts (P =.048). The patients in the magnesium sulfate group had more adverse side effects, mainly nausea and vomiting (P =.004). There were no differences in birth weight, estimated gestational age at delivery, or neonatal complications between the 2 groups. CONCLUSIONS: Oral nicardipine is an effective, safe, and well-tolerated tocolytic agent. In this prospective clinical trial patients randomly assigned to receive oral nicardipine had arrest of preterm labor more rapidly than did those randomly assigned to receive parenteral magnesium sulfate. Patients who received magnesium sulfate were more likely to have adverse medication effects and recurrent preterm labor.

Administration, Oral↗
PubMed1999

Irreversible corneal decompensation in patients treated with topical dorzolamide.

PURPOSE: To describe irreversible corneal decompensation after topical dorzolamide hydrochloride (Trusopt; Merck and Co, Inc, West Point, Pennsylvania) therapy in nine patients who had histories consistent with corneal endothelial compromise. METHOD: Multicenter review of patients' charts. RESULTS: Nine eyes of nine patients developed overt corneal decompensation after starting topical dorzolamide, a condition that did not resolve with drug cessation. This occurred after 3 to 20 weeks (mean, 7.8) of therapy. All nine patients had undergone intraocular surgery. Eight patients had undergone cataract surgery; three were aphakic and three had posterior chamber intraocular lenses. Two patients had anterior chamber intraocular lenses and also had undergone trabeculectomies. Four patients had undergone penetrating keratoplasties, each case complicated by episodes of corneal allograft rejection that were successfully treated. Two patients had asymptomatic Fuchs endothelial dystrophy. Seven patients have since undergone successful penetrating keratoplasties. CONCLUSION: The reports suggest that dorzolamide can cause irreversible corneal edema in a subset of glaucoma patients with endothelial compromise. The findings suggest a rationale for research into the long-term effects of dorzolamide on the corneal endothelium.

Administration, Topical↗
PubMed1999

Risk factors for secondary arrest of labor among women >41 weeks' gestation with an unfavorable cervix undergoing membrane sweeping for cervical ripening.

OBJECTIVE: To identify the risk factor(s) for secondary arrest of labor among women with an unfavorable cervix at > 41 weeks' gestation. METHODS: Prospectively all gravid women with a Bishop score of < or = 4 and no contraindication to a vaginal delivery were candidates for this study. Univariate analysis followed by logistic regression modeling were used to identify variables with a significant association. RESULTS: Over a 9-month period, 115 women entered into the study. In univariate analysis, variables with a significant association with cesarean delivery: (1) non-Caucasian race (P = 0.007), Bishop score < 7 at hospitalization; P = 0.001, and reason for admission (P = 0.017). Logistic regression analysis yielded OR 4.7 (1.6, 15) non-Caucasian race and 9.5 (3.2, 30.8) Bishop < 7 on admission. CONCLUSION: Pregnancies > 41 weeks with an unfavorable cervix, non-Caucasian race and a failure to achieve a Bishop score of > or = 7 prior to hospitalization were significant risk factors for abdominal delivery.

Cervical Ripening↗
PubMed1999

Membrane sweeping versus dinoprostone vaginal insert in the management of pregnancies beyond 41 weeks with an unfavorable cervix.

OBJECTIVE: To determine the best method of cervical ripening to prevent postdate inductions in women with an unfavorable cervix at 41 weeks' gestation. STUDY DESIGN: Women presenting at 41 weeks' gestation with a Bishop score of < or = 4 received daily dinoprostone (Cervidil) vaginal inserts (group I) or daily membrane sweeping (group II). RESULTS: One-hundred and eighty-two women were prospectively randomized with 91 women in each arm. The women in group II, membrane sweeping, had Bishop scores significantly greater on admission for delivery (p < 0.001), had less time elapsed from admission to delivery (p = 0.018), and had fewer labor inductions at 42 weeks (p = 0.04) than the women in group I, the dinoprostone group. In addition, a greater number of women in group II were admitted in spontaneous labor (p = 0.006) than in group I. Total antenatal costs for the membrane sweeping group was $15,120 versus $59,540 for the dinoprostone group. CONCLUSION: Daily membrane sweeping was more effective than dinoprostone administration with fewer postdate inductions at one-fourth the cost.

Adult↗
PubMed1999

Sterilization and its consequences.

UNLABELLED: The purpose of this review is to analyze critically the two techniques of sterilization (bilateral tubal ligation [BTL] and vasectomy) so that a physician may provide informed consent about methods of sterilization. A MEDLINE search and extensive review of published literature dating back to 1966 was undertaken to compare preoperative counseling, operative procedures, postoperative complications, procedure-related costs, psychosocial consequences, and feasibility of reversal between BTL and a vasectomy. Compared with a vasectomy, BTL is 20 times more likely to have major complications, 10 to 37 times more likely to fail, and cost three times as much. Moreover, the procedure-related mortality, although rare, is 12 times higher with sterilization of the woman than of the man. Despite these advantages, 300,000 more BTLs were done in 1987 than vasectomies. In 1987, there were 976,000 sterilizations (65 percent BTLs and 35 percent vasectomies) with an overall cost of $1.8 billion. Over $260 million could have been saved if equal numbers of vasectomies and BTLs had been performed, or more than $800 million if 80 percent had been vasectomies, as was the case in 1971. The safest, most efficacious, and least expensive method of sterilization is vasectomy. For these reasons, physicians should recommend vasectomy when providing counseling on sterilization, despite the popularity of BTL. TARGET AUDIENCE: Obstetricians & Gynecologists, Family Physicians LEARNING OBJECTIVES: After completion of this article, the reader will be able to predict the failure rates and likelihood of successful reversal of tubal ligation and vasectomy; to recall the difference in cost between the two sterilization procedures, and to describe the short-term and long-term complications associated with each of the two methods of sterilization.

Counseling↗
PubMed1999

Low amniotic fluid volume is poorly identified in singleton and twin pregnancies using the 2 x 2 cm pocket technique of the biophysical profile.

BACKGROUND: This study was done to determine the accuracy of the 2 x 2 cm pocket identifying low amniotic fluid (AF) volume in singleton and twin pregnancies. METHODS: The AF volume was evaluated by ultrasonography for the presence of a 2 x 2 cm pocket before amniocentesis. The actual AF volume was then determined by a diazo-dye reaction with subsequent spectrophotometric analysis using paraminohippurate. RESULTS: The AF volume was low in 21 of the 79 singleton pregnancies and normal in 47; hydramnios was present in 11. Among amniotic sacs of the 60 twin pairs, oligohydramnios was found in 33 amniotic sacs. normal AF volume in 80 sacs, and high volume in 7. An AF pocket smaller than 2 x 2 cm was identified in only 3 of the 79 singleton pregnancies and in only 2 of the 120 twin amniotic sacs. CONCLUSIONS: Judging AF volume on the basis of a 2 x 2 cm pocket misses more than 90% of cases of oligohydramnios in singletons and twins.

Adolescent↗