Central nervous system decompression sickness: latency of 1070 human cases

Many aspects of central nervous system (CNS) decompression sickness (DCS) are poorly understood, including the temporal pattern of its presentation and the pathogenic mechanisms involved in the development of the disease. Using case histories and clinical series published in the literature and retrieved from treatment center records, this study is an attempt to define the interval between surfacing from a hyperbaric exposure and the onset of symptoms of CNS DCS. The results of 1070 cases of human CNS DCS were included in the study. The results show that the disease generally occurs rapidly: over 50% became symptomatic within 10 min of returning to 1 ATA, and in only 15% of cases was the onset of symptoms delayed for more than 1 h. Cerebral DCS had a more rapid onset than spinal cord disease: 50% of cerebral cases became apparent within about 3 min and a similar proportion of spinal cord cases within about 9 min from surfacing. The influence of these results on the diagnosis and treatment of dysbaric illness, on the safety of certain diving practices, and on possible pathogenic mechanisms is discussed.     

Experimental studies on the comparative infectivity and pathogenicity of Streptococcus suis type 2. I. Porcine and human isolates in pigs

Piglets between 1 and 40 days of age were inoculated with varying numbers and with different isolates of Streptococcus suis type 2 by the intranasal, intravenous and subarachnoid routes. Less than 100 organisms of an isolate cultured from apparently normal pigs caused subclinical infection in 1-day-old piglets after intranasal inoculation. This infection was naturally transmitted between litter mates. Intravenous inoculation of a similar isolate in 7-week-old pigs resulted in a sub-clinical bacteraemia in 3 of 8 piglets. One other piglet developed a bacteraemia 7 days after inoculation and concurrently developed signs of lameness and nervous dysfunction. Ten piglets were inoculated by the subarachnoid route with a porcine isolate and two with an isolate from a person with clinical disease. Only the latter two pigs developed the classical signs of nervous disease associated with infection by S. suis type 2. It is concluded that strains of S. suis type 2, of varying pathogenicity for both pigs and man, are endemic in New Zealand. It is suggested that the occurrence of disease is associated with both exposure to a pathogenic strain and other, as yet undetermined, secondary factors.     

Pulmonary vascular resistance during lipid infusion in neonates.

Using two-dimensional echocardiography, pulmonary vascular resistance was estimated from right ventricular pre-ejection period to ejection time (RVPEP/ET) in 11 preterm infants with respiratory distress, to test the effect of different doses of continuous lipid infusion. Echocardiography was performed at baseline with no lipid infusing 2 and 24 hours after 1.5 and 3 g/kg/day of intravenous lipid, 24 hours after discontinuing intravenous lipid emulsion, and 2 hours after restarting intravenous lipid. After 24 hours of intravenous lipid at 1.5 g/kg/day the RVPEP/ET rose to mean (SD) 0.287 (0.03) from a baseline value of 0.225 (0.02) and to 0.326 (0.05) after 24 hours of intravenous lipid at 3 g/kg/day. Pulmonary arterial pressure returned to baseline 24 hours after the intravenous lipid had been discontinued. Continuous 24 hour infusion of lipid caused significant dose and time-dependent increases in pulmonary vascular resistance. Intravenous lipid may aggravate pulmonary hypertension.     

Immunohistochemical study of oral keratoses including lichen planus

Biopsies of non-ulcerated oral mucosa from 13 patients with oral lichen planus and 12 patients with leukoplakia were immunohistochemically stained using monoclonal antibodies to pan T, pan B, T helper and T suppressor/cytotoxic cells and the stained lymphocytes enumerated using an image analyser. The results show the preponderance of T cells infiltrating both oral lichen planus and leukoplakia. The T helper: T suppressor/cytotoxic cell ratio was the same (1:2) for both oral lichen planus and leukoplakia. A similar proportion of T suppressor/cytotoxic cells was found infiltrating the epithelium. These data indicate that T cell subset analysis is of no value in distinguishing oral lichen planus from other oral keratoses.     

Effect of dietary butylated hydroxytoluene on nuclear envelope cytochrome P-450 during the initiation and promotion stages of hepatocarcinogenesis.

The anticarcinogenic effect of the dietary antioxidant butylated hydroxytoluene (BHT) correlates with a preservation of nuclear envelope (NE) cytochrome P-450 in rats undergoing chemically induced hepatocarcinogenesis. This effect of BHT on NE cytochrome P-450 was observed during both the initiation and the promotion stages of hepatocarcinogenesis. Complex interactions between the two different mechanisms of action of BHT (i.e., enzyme induction and antioxidant activity) may account for some of the differences between the patterns of response to BHT observed during initiation and promotion.     

Motor vehicle rollover and static stability: an exposure study.

OBJECTIVES: This study examined vehicle rollovers in terms of site-specific exposure and speeds of vehicles of varying stability. METHODS: Fifty-one rollover sites in two states were visited at the same time of day and day of week as the rollover. A sample of vehicles moving in the same direction as the rollover were observed, and vehicle-specific data were obtained from identification numbers. RESULTS: Low stability, exacerbated by the addition of passengers, increased the risk of rollover. Speed was not correlated with stability and is not a confounder. CONCLUSIONS: Rollovers could be substantially reduced if motor vehicles were manufactured with a static stability of 1.2 or greater.     

Cerebral blood flow, arteriovenous oxygen difference, and outcome in head injured patients.

Cerebral blood flow (CBF) and other physiological variables were measured repeatedly for up to 10 days after severe head injury in 102 patients, and CBF levels were related to outcome. Twenty five of the patients had a reduced CBF [mean (SD) 0.29 (0.05) ml/g/min]; 47 had a normal CBF, (0.41 (0.10) ml/g/min); and 30 had a raised CBF (0.62 (0.14) ml/g/min). Cerebral arteriovenous oxygen differences were inversely related to CBF and averaged 2.1 (0.7) mumol/ml in the group with reduced CBF, 1.9 (0.5) mumol/ml in the group with normal CBF, and 1.6 (0.4) mumol/ml in the group with raised CBF. Patients with a reduced CBF had a poorer outcome than patients with a normal or raised CBF. Mortality was highest in patients with a reduced CBF, and was 32% at three months after injury, whereas only 21% of the patients with a normal CBF and 20% of the patients with a raised CBF died. There were no differences in the type of injury, initial score on the Glasgow Coma Scale, mean intracranial pressure (ICP), highest ICP, or the amount of medical treatment required to keep the ICP less than 20 mm Hg in each group. Systemic factors did not significantly contribute to the differences in CBF among the three groups. A logistic regression model of the effect of CBF on neurological outcome was developed. When adjusted for variables which were found to be significant confounders, including age, initial Glasgow Coma Score, haemoglobin concentration, cerebral perfusion pressure and cerebral metabolic rate of oxygen, a reduced CBF remained significantly associated with an unfavourable neurological outcome.     

Unique variant of partial anomalous pulmonary venous connection with intact atrial septum

Summary Partial anomalous pulmonary venous connections (PAPVCs) are rare in association with an intact atrial septum. However, the diagnosis should be considered in patients with otherwise unexplained findings of left-to-right shunt and right heart enlargement. An unusual variant is presented, which we considered unsuitable for operative repair, based on findings at catheterization. Developmental, hemodynamic, and surgical considerations are discussed.