The weight debate.

Therapeutic interventions administered on Critical Care are often dosed on the basis of patient body size, to ensure treatments are effective in achieving their goals and to prevent harm from overdose. Many treatment modalities use predicted weights estimated from descriptors such as sex, weight and height to reduce error that is associated with using total body weight in critically ill patients. In this article we review the size descriptors that have been described, their origin and calculation. We then examine the role they play in dosing of common therapies utilised in Critical Care and potential areas of research for the future.

How does coarse gravel augmentation affect early-stage Chinook salmon Oncorhynchus tshawytscha embryonic survivorship?

Early-stage Chinook salmon Oncorhynchus tshawytscha embryos were incubated in artificial redds that mimicked hyporheic conditions in gravel-augmented habitat to assess survivorship. Two complementary experiments were conducted where units varied along gradients of (1) increasing interstitial flow velocity (0·05-2·50 cm s⁻¹) in a uniformly coarse (particles ≥22 mm) sediment mixture and (2) increasing sediment porosity with interstitial flow velocity held constant. Embryonic survivorship increased moderately along a gradient of interstitial flow velocity, while survivorship among units with varying sediment porosities was consistent. No evidence for flow-induced agitation and mortality was observed. Results suggest that high interstitial flow velocities may confer a moderate advantage for incubating salmonid embryos when conditions that typically reduce embryonic mortality (i.e. low concentrations of fine particles) are ideal.

Facial frequency manipulation normalizes face discrimination in AD.

People with AD have deficient contrast sensitivity and impaired face discrimination. The authors presented photographs of unfamiliar faces of three different sizes to enhance the low, middle, or high facial frequency information (cycles per face). Patients with AD demonstrated normal discrimination of small faces only, indicating that impaired contrast sensitivity at low facial frequencies contributes to their poor face discrimination.

Interferometric radar measurements of water level changes on the Amazon flood plain

Measurements of water levels in the main channels of rivers, upland tributaries and floodplain lakes are necessary for understanding flooding hazards, methane production, sediment transport and nutrient exchange. But most remote river basins have only a few gauging stations and these tend to be restricted to large river channels. Although radar remote sensing techniques using interferometric phase measurements have the potential to greatly improve spatial sampling, the phase is temporally incoherent over open water and has therefore not been used to determine water levels. Here we use interferometric synthetic aperture radar (SAR) data, acquired over the central Amazon by the Space Shuttle imaging radar mission, to measure subtle water level changes in an area of flooded vegetation on the Amazon flood plain. The technique makes use of the fact that flooded forests and floodplain lakes with emergent shrubs permit radar double-bounce returns from water and vegetation surfaces, thus allowing coherence to be maintained. Our interferometric phase observations show decreases in water levels of 7-11 cm per day for tributaries and lakes within approximately 20 km of a main channel and 2-5 cm per day at distances of approximately 80 km. Proximal floodplain observations are in close agreement with main-channel gauge records, indicating a rapid response of the flood plain to decreases in river stage. With additional data from future satellite missions, the technique described here should provide direct observations important for understanding flood dynamics and hydrologic exchange between rivers and flood plains.

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.

A nonsense mutation (G15059A) in the cytochrome b gene in a patient with exercise intolerance and myoglobinuria.

We describe a new mitochondrial DNA mutation in the cytochrome b gene in a patient presenting with progressive exercise intolerance and myoglobinuria associated with complex III deficiency in muscle. The point mutation results in the replacement of a glycine at amino acid position 190 with a stop codon. This change predicts premature termination of translation, leading to a truncated protein missing 244 amino acids at the C-terminus of cytochrome b. The mutation fulfills all the accepted criteria for pathogenicity, suggesting that this is the primary cause of the myopathy in the patient.

Pre-school follow-up of a cohort of children with myelomeningocele in Cape Town, South Africa.

A cohort of South African children with myelomeningocele was followed for 5 years. Fifty-three were from metropolitan Cape Town and 65 from rural areas including the tribal region of Transkei. The mean general developmental quotient (GQ) at 5 years of age was lower than that previously reported. Black and coloured children had lower GQs than white children, but there were no significant differences between those from the urban and the rural areas. Early closure of the lesion and delivery by caesarean section were associated with higher levels of general developmental functioning. Central nervous system infections and the placement of more than one shunt for hydrocephalus resulted in lower GQs. Lesions above L2 were associated with non-ambulation. Ambulation was more likely in children in Cape Town than in rural children. Urinary incontinence occurred more frequently in rural children and among those in lower socio-economic circumstances.

Group-level ethics in managed care.

Managed care, the newest scheme for health care delivery, is under fire for skimping on quality, hiding information from patients and restricting free choice of providers. Medical group managers now face ethical questions quite unlike the medical ethics taught in medical schools. The new questions are about how the entire network of U.S. health care institutions work. Five principles can guide an appropriate ethics for this group-level reflection: 1) institutions are means to support the common-wealth, not ends in themselves; 2) people have a right to shape their health care options; 3) competition does not exclude collaboration; 4) a proper cost-benefit analysis will regard the entire community, not merely one institution; and 5) mission statements should be written by the people involved in delivering the care.

A high prevalence of abnormal personality traits in chronic users of anabolic-androgenic steroids.

OBJECTIVE: (1) To assess the personality profiles of the anabolic androgenic steroid users (AAS) and (2) to determine whether valid premorbid personality traits could be obtained from cross sectional assessment using multisource data. METHODS: The first author became a participant-observer in a group of body builders. An experimental group of body builders who had been using AAS for no more than 18 months (n = 12) was identified. A group of control subjects, each of whom claimed that he did not, and never had, used AAS (n = 12) was also recruited during this period. Key informants played a crucial role in recruiting subjects representative of the AAS and body building communities. An interview schedule based on the Diagnostic and statistical manual of mental disorders (DSM3-R) personality disorder criteria was conducted with each subject. Additional data were obtained from an AAS using informant and significant others including family and friends. RESULTS: The user group was significantly heavier than the control group and showed abnormal personality traits, in contrast to the control group. Personality traits of AAS users before the onset of AAS use, assessed retrospectively, were not different from personality traits of control subjects. There were significant differences between the before and after personality traits in AAS user group. CONCLUSIONS: The results suggest (1) that AAS use is associated with significant disturbances in personality profile, and (2) that these personality disturbances are possibly the direct result of AAS use.

Hospital closure: Phoenix, Hydra or Titanic?

Very little has been published about the effects of hospital closure in terms of the service, financial or management issues of the process. Attempts through a case-study format to redress the balance and as such represents the reflections of practitioners who have recently undergone the experience of hospital closure and the often neglected issues arising both during and after the process.

The prevalence of antibodies to hepatitis C virus at two haemodialysis units in South Africa.

The prevalence of antibodies against hepatitis C virus (HCV) was determined in 103 haemodialysis patients who attended two dialysis units in South Africa. With the use of a second-generation enzyme-linked immunosorbent assay (UBI HCV EIA, Organon Teknika, The Netherlands) and a 4-recombinant immunoblot assay (Chiron Corporation, USA), antibodies to HCV were found in 22 patients (21%). Statistically significant associations with anti-HCV carrier status were duration of dialysis (P = 0.0005) and number of blood transfusions received (P = 0.008). With stepwise logistic regression analysis it was not possible to separate the effects of HCV status associated with these two variables. A transient elevation in alanine aminotransferase (ALT) occurred in 8 of the 22 anti-HCV-positive patients, compared with 14 of the 81 anti-HCV-negative patients (P = 0.054). As yet, no patients have clinical evidence of ongoing liver disease or persistently elevated ALT levels. Of the 45 dialysis staff members tested, none was positive for anti-HCV.

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.