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Biomedical subjects

J P Pretorius

Publications and source records attributed to J P Pretorius.

17 recordsLinked to original sources
PubMed1995

Hemostatic competency and elastase-alpha 1-proteinase inhibitor levels in surgery, trauma, and sepsis.

Previous studies investigated the effects of neutrophil elastase on isolated factors in the hemostatic process. Some of these reported effects are, however, procoagulative and others anticoagulative. The aim of this study was to ascertain the effect of elastase on the in vivo hemostatic competency. The effect of elastase activity on the hemostatic competency was determined in a group of 50 surgical intensive care unit patients and 23 control subjects. Surgical intensive care unit patients were subgrouped into a surgery, a trauma, and a sepsis-multiple organ failure group. Elastase activity was assessed by elastase-alpha 1-proteinase inhibitor levels and hemostatic competency by thromboelastography. Thromboelastography results showed a relatively normal coagulative ability in the surgery group, a varying degree of thromboelastographic hypocoagulability in the trauma group, and pronounced thromboelastographic instability in the sepsis-multiple organ failure group. Increases in elastase-alpha 1-proteinase inhibitor levels up to 200 micrograms/L were accompanied by a compromised coagulative ability as seen in a prolongation of both the first and second phases of the clotting time, as well as a decrease in the maximal clot elasticity.

Case-Control Studies↗
PubMed1994

[Computerization in intensive care].

Computers already constitute an integral part of intensive care units as almost all pieces of sophisticated equipment in intensive care contain a computerized component. However, a marked lack of computerization exists with regard to data collection, data analysis and in teaching support systems. This article presents a summary of the advantages of computerization of data in intensive care and cautions on possible pitfalls in the choice of equipment and in its implementation.

Hospital Information Systems↗
PubMed1992

In vivo assessment of regional microvascular albumin leakage during E. coli septic shock in the baboon model.

Changes in regional microvascular albumin flux during septic shock were studied noninvasively by scintigraphy in the baboon model. Use was made of an i.v. injection of 99mTc-labeled baboon serum albumin. Count ratios of lung to cardiac, liver to cardiac, and abdominal to cardiac regions were measured two-hourly for 6 hr in six control and six septic shock baboons (live E. coli) and compared. Increased ratios obtained during shock pointed to an increase in extravascular albumin. Linear regression lines fitted to these count ratios provided regional albumin leak indices. These indices demonstrated statistically significant increases (P less than 0.05) during septic shock for the abdominal region during the 6-hr study, and for all regions, but especially the abdomen, when data were calculated over 4 hr. Increasing ratios and leak indices correlated with postmortem data and with changes in neutrophil and platelet behaviour previously established during shock. Possible accompanying mediator releases could be responsible for the endothelial damage leading to the increased permeability.

Animals↗
PubMed1991

The effect of fluid resuscitation on cardiac function changes monitored by radionuclide ventriculography in the septic shock baboon model.

Dramatic cardiac volume losses accompanied by a drop in arterial pressure and in pulmonary capillary wedge pressure (PCWP) were found to characterise the baboon model in bacterial septic shock. Loss of vascular tone and a probable vascular fluid leak were regarded as contributing factors. To prove this hypothesis an experiment was planned with the baboon model in septic shock, and an added protocol for fluid administration whereby the pulmonary wedge pressure was kept at 7 +/- 2 mm Hg. The six baboons served as their own controls. Raising PCWP by means of fluid loading resulted in an attenuation of the drop in left ventricular volumes, to a smaller decrease in stroke volume (SV) and smaller increases in left ventricular ejection fraction. The drop in arterial pressure remained and left ventricular stroke work therefore reflected the decrease in SV. Compliance as by EDV/PCWP remained unchanged. Fluid loading therefore, although not normalising the haemodynamic parameters, led to smaller changes and an improvement in some measures of cardiac function.

Animals↗
PubMed1987

The 'lung in shock' as a result of hypovolemic-traumatic shock in baboons.

The "lung in shock" syndrome is a constellation of early morphologic changes in the lung within 1 hour after polytrauma as indicated by human lung biopsies. A hypovolemic-traumatic (soft-tissue trauma together with bone fractures) baboon model with reinfusion was established to study these morphologic and associated pathophysiologic events. This model was developed in order to test the efficacy of therapeutic modalities in future studies. Nineteen baboons (eight sham, 11 shock) were anesthetized with spontaneous respiration while complete hemodynamic and blood gas monitoring was performed, along with light and electron microscopic studies of the lungs. Besides the usual shock-related hemodynamic disturbances and the metabolic acidosis, pathologic changes were found both on light and electron microscopy of the lungs but not on X-rays and measurements of blood oxygenation. In the shock group, morphologic evidence of endothelial and interstitial edema was associated with significant increases in lung weight. The fluid accumulation occurred in spite of careful control of pulmonary artery pressures during the study. More striking histologic findings were significant cellular infiltration of lung tissue, especially by leukocytes, showing evidence of degranulation. This baboon study, similar to studies undertaken in canines, shows that the hypovolemic (hemorrhagic) shock in association with trauma (fracture, soft-tissue trauma) causes ultrastructural morphologic changes that may precede potentially life-threatening functional changes in the lung.

Animals↗
PubMed1987

Baboon (Papio ursinus) model to study deep vein thrombosis using 111-indium-labeled autologous platelets.

This study evaluates the chacma baboon as a model for investigations on deep vein thrombosis (DVT). There is a good correlation of the baboon and human thrombelastographic parameters (r-time, k-time, ma). Investigation on the diagnostic efficacy of 111 In-labeled platelets as an imaging agent for DVT cast considerable doubt on the procedure, owing to the age of the thrombus.

Animals↗
PubMed1987

The sensitivity of radionuclide and thermodilution techniques to detect cardiac dysfunction in the baboon model during prolonged anaesthesia.

This study was undertaken to evaluate the fluctuations of cardiac parameters in a baboon model during pentobarbitone anaesthesia which will serve as a baseline control for shock studies. Thermodilution and radionuclide methods were used to determine cardiac parameters. Radionuclide studies were repeated without any cardiac catheters to assess the effect of these on cardiac performance. The results represent baseline fluctuations in cardiac parameters against which cardiac dysfunction can be diagnosed in shock studies. The results also indicate that cardiac catheterisation does not affect cardiac performance significantly.

Anesthesia, Intravenous↗
PubMed1985

Equitable evaluation in the teaching of integrated clinical medicine.

When clinical medicine is offered as an integrated subject for undergraduate students it poses a problem when it comes to evaluation. Departmental heads become concerned about students' tendency to neglect or even disregard 'minor' subjects because of their small contribution to the composite evaluation mark. A method for allocating weights to various subjects was devised and a computer programme for random allocation of the percentage content of major and minor subjects established. As experience over the past 5 years has shown, the system has been found acceptable by both teachers and students.

Education, Medical, Undergraduate↗
PubMed1985

Evaluation of the diagnostic efficacy of autologous 111In-labelled platelets as a scanning agent for deep vein thrombosis in the chacma baboon.

The diagnostic efficiency of autologous 111In-labelled platelets (ILP) as a scanning agent in deep vein thrombosis (DVT) was investigated in 24 South African baboons (Papio ursinus). Thrombi were surgically induced by stasis, intimal injury and the injection of thrombin in the common femoral veins of adult baboons. The thrombi were allowed to age for 1, 2, 4, 8, 24, 48 and 72 h before injecting the ILP. Scanning was done with a large field gamma camera at 10 min post injection and again at 2, 4, 6, 8, 10, 14, 24, 48 and 72 h. Time-activity curves were thus obtained and it was possible to establish an optimal time after injection of the ILP to scan for each group of thrombi. The results indicate that only the younger thrombi (1-8 h after thrombus formation) were detected. Twenty-four hour and older thrombi were not visualised. A favourable time to scan in the case of the younger thrombi appeared to be approximately 20 h after the injection of ILP. However, the thrombus age limitation still impairs the diagnostic efficiency of the procedure.

Animals↗
PubMed1985

Relative observer accuracy for dichotomized variables.

We suggest that the relative accuracy of several observers of a disease manifestation can be assessed by comparing the strength of association between their observations and a known cause of that disease. In principle, the observer whose findings are most strongly associated with the causal variable has the least error. In practice many observations appear binary ("normal" or "abnormal") when the underlying distribution of the variable they measure is continuous. For this case of a dichotomized variable, several observers may find different prevalences of abnormality in the same sample either because their accuracy differs or because they use different thresholds above which they regard abnormality as present. A comparison of how strongly their observations are associated with a causal variable using statistical methods for binary observations may lead to incorrect conclusions about the relative accuracy of the observers. We suggest and evaluate a method, based on the biserial correlation coefficient, for comparing the relative accuracy of several observers who may differ in the thresholds they use.

Asbestosis↗
PubMed1983

High ischaemic heart disease mortality among young Afrikaners.

The death rates from ischaemic heart disease (IHD) of White South Africans in districts where more than 80% were Afrikaners were compared with those for the rest of the country. The rates for the predominantly Afrikaans districts were higher for males under the age of 50 years and for females under 55 years. Approximately a quarter of the IHD deaths up to these ages were associated with the unique Afrikaner component. The rates for non-Afrikaner females were similar to those for females in the USA. The rates for non-Afrikaner males, however, were higher.

Adolescent↗
PubMed1980

A study on child development in Cape Town. The cohort and sample.

A study of growth and development was initiated on a cohort of Coloured children born during May 1976 in Cape Town. Approximately 90% of the infants were born in hospital or in midwife obstetric units and about 14% weighed less than 2 500 g. Poor maternal education, low income and overcrowding are considered to be risk factors in child rearing. Sixty-five per cent of the mothers were not educated further than primary school level and over half the families were living below an effective minimum level of income. Similarly, over half the families lived in grossly overcrowded conditions.

Child Development↗