Morphine suppresses the oxytocin response in breast-feeding women.

The activity of opiate-mediated regulatory mechanisms of oxytocin secretion during breast-feeding was studied by the administration of either morphine, naloxone or placebo to women prior to the commencement of breast-feeding. Seventeen healthy women in the first week after delivery who had established lactation were randomized to receive either intravenous morphine 5 mg (n = 6), naloxone 2.4 mg (n = 6) or a placebo, sterile water (n = 5), which was given prior to commencement of breast-feeding. Oxytocin levels were measured by radioimmunoassay prior to initiation of breast-feeding and then at 2-min intervals until the feed was complete. Breast-feeding produced a significant rise in oxytocin levels in the control and naloxone groups but no significant rise in the patients given morphine. There was a significant reduction in oxytocin response following morphine administration when compared to placebo but not between naloxone and placebo. In conclusion, oxytocin secretion to breast-feeding is inhibited by exogenous morphine when compared to a control group but the administration of naloxone did not produce a significant difference from control.

Spinal cord protection in the absence of collateral circulation: meta-analysis of mortality and paraplegia.

A meta-analysis of paraplegia complicating aortic surgery on patients having neither intercostal nor spinal collaterals, epitomized by patients with acute traumatic aortic rupture, was done. Index Medicus and Medline were searched for all suitable English publications between 1972 and 1992. New paraplegia occurred in 9.9% of 1492 patients who underwent surgery. However, 19.2% of patients undergoing surgery with only simple aortic cross-clamping developed paraplegia, in contrast to 6.1% if distal aortic perfusion was augmented by either "passive" or "active" methods (p < 0.00001). The risk of paraplegia increased progressively as cross-clamp times lengthened if simple aortic cross-clamping was used (p < 0.00001), but only once did the cross-clamp time exceed 30 minutes (p < 0.05). Paraplegia occurred in 8.2% of patients with "passive" shunts from the ascending aorta (p < 0.001 vs simple cross-clamping). Shunts from the left ventricular apex, however, had an incidence of paraplegia of 26.1% and, therefore, did not decrease the risk of paraplegia. "Active" augmentation of distal perfusion had the lowest risk of paraplegia: 2.3% (p < 0.00001 vs simple cross-clamping or "passive" shunts). Mortality, however, was higher in these potentially polytraumatized patients when they were perfused distally using methods requiring full systemic heparinization (18.2%), compared to mortality with methods not requiring heparin (11.9%; p < 0.01). In conclusion, simple aortic cross-clamping has a high risk of paraplegia if the cross-clamp time extends beyond 30 minutes. "Active" modalities of augmenting distal perfusion provide optimal spinal protection.

Prevalence of neural tube defects in Cape Town, South Africa.

The aim of the study was to document the frequency of neural tube defects (NTD) over a 20-year period in Cape Town and to determine the effects of race, gender, maternal age, parity and season of conception on the prevalence. Multiple sources of ascertainment were used, including all maternity hospital records, neurosurgical and spinal defects clinic data, as well as those from the Human Genetics Department and Fetal Abnormality Group. The prevalence rates for NTD fluctuated between 1.74 and 0.63 per 1,000 births, but showed no significant trends over the 20-year period. Prevalence rates were highest for the white population group of 2.56 per 1,000 births compared to 0.95 per 1,000 for blacks and 1.05 per 1,000 for those of mixed ancestry. The higher rates in the whites, who are of British and European extraction and belong to the more affluent section of the community, would suggest that the possible effects of nutrition and infection are overshadowed by genetic factors. There was a female preponderance for both spinal bifida (M:F ratio 0.89) and anencephaly (M:F ratio 0.67). The highest NTD rates were found at both ends of the maternal age range (< 20 years and > 35 years of age). The prevalence was highest at the extremes of birth order (1.65 and 1.58 for birth order 1 and > 7, respectively, and 0.56 and 0.45 for birth order 5 and 6, respectively). A seasonal variation occurred which differed from that reported for the Northern Hemisphere and may reflect local climatic conditions.

Traumatic aortic rupture: twenty-year metaanalysis of mortality and risk of paraplegia.

A metaanalysis of articles concerning the surgical management of acute traumatic rupture of the descending thoracic aorta published in the English-language literature between 1972 and July 1992 was performed. The overall mortality of 1,742 patients who arrived at the hospital alive was 32.0%, one-third died before surgical repair was started. Paraplegia was noted preoperatively in 2.6% of these hospitalized patients, and paraplegia complicated the surgical repair in 9.9% of 1,492 patients who reached the operating room in a relatively stable condition. Patients then were analyzed according to the surgical intervention used. Simple aortic cross-clamping (n = 443) was associated with a hospital mortality of 16.0% and incidence of paraplegia of 19.2%, despite lower average mean cross-clamp times (32 minutes; p < 0.01 versus passive or active methods of providing distal perfusion). In a subset of 290 patients in whom individual data were available, the cumulative risk of paraplegia was shown to increase substantially if the duration of aortic cross-clamping exceeded 30 minutes, but only when distal perfusion was not augmented (p < 0.00001). "Passive" perfusion shunts (n = 424) were associated with a mortality of 12.3%, and the incidence of paraplegia decreased to 11.1% (p < 0.001). However, shunts inserted from the apex of the left ventricle had a contradictory high 26.1% incidence of paraplegia compared with shunts from the ascending aorta (8.2%; p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of morphine and naloxone administration on maternal oxytocin concentration in late pregnancy.

OBJECTIVE: Modification of the inhibitory control of oxytocin secretion by endogenous opiates in late pregnancy may be one of the factors involved in the onset of labour. The interrelationships between exogenously administered opioids and oxytocin may demonstrate activity of this control mechanism. This study was undertaken to investigate the effect of an opiate and an opiate antagonist on maternal oxytocin levels in late pregnancy. DESIGN: Patients were randomized to receive either morphine (5 mg), naloxone (2.4 mg) or sterile water (1 ml) intravenously. PATIENTS: Thirty women with singleton pregnancies greater than 36 weeks gestation who were not in labour were studied. MEASUREMENTS: Blood for peripheral oxytocin levels was sampled every 2.5 minutes for 15 minutes before and 15 minutes after administration of the assigned substance. Oxytoxin was measured by radioimmunoassay. Peripheral beta-endorphin levels were measured at the beginning and end of the study. RESULTS: There was no significant change in the maternal oxytocin concentration after administration of either morphine, naloxone or sterile water compared to pretreatment levels. beta-Endorphin levels did not change significantly, either from the beginning to the end of the study, or between groups. CONCLUSION: In late pregnancy exogenous opiates and opiate antagonists have no effect on maternal peripheral oxytocin levels.

Study approaches of nursing students: effects of an extended clinical context.

In the first part of this study a comparison is made between the approaches to studying adopted by failing and achieving nursing college students. It is concluded that failing students manifest approaches to studying that are, in some respects, conceptually difficult to interpret. This conclusion is presented against a background of similar findings that have emanated from other recent studies on student learning. The second part of this study investigates the influence of contextual perceptions on the manifestation of the approaches to studying adopted by achieving students. In thus exploring the manifestation of different forms of contextualized approaches to studying (which are referred to as study orchestrations) a distinction is made between the influences attributable to 'conventional' and 'clinical' sets of contextual variables. In an extension of previously reported studies, it is concluded that the combined set of these contextual variables explains significantly more of the variation in study approaches than the set of 'conventional' variables. It is further concluded that, under the influence of an extended set of contextual variables, conceptually related, but differing forms, of study orchestration may be manifested; a general form which is readily interpretable in terms associated with 'conventional' academic contextual variables and a clinical form which, in the present study, is associated specifically with a nursing academic environment. The implications of these conclusions for nursing education are discussed and areas for future research are indicated.