Biomedical subjects

R Vaillancourt

Publications and source records attributed to R Vaillancourt.

23 records · Page 2Linked to original sources

PubMedDate not supplied

The Ito "Flow-Through" Centrifuge. A new device for long-term (24 hours) plasmapheresis without platelet deterioration.

An efficacious procedure for continuous plasmapheresis in long-term extracorporeal circulation has not yet been devleoped. This technique could be important in plasma exchange or cross-exchange and in artificial organ support if it could be accomplished safely using heparin as the anticoagulant. When sheep were connected to the Celltrifuge for 23 hours and administered 150 units/kg per hour heparin anticoagulant, we found gross platelet clumping in separated plasma and a 60 per cent fall in platelet count. When 120,000 units of heparin were directly injected into the centrifuge bowl at the onset of the centrifugation followed by hourly heparin administration at 500 units/kg, there was no platelet clumping but the platelet count fell to 52 per cent. Under identical conditions the Ito Flow-Through Centrifuge, a new continuous flow centrifuge with no rotating seals, was used. We found no platelet aggregates and no drop in platelet count, and there was a 100 per cent recovery of platelets in the separated plasma. Platelets sampled from arterial blood and separated plasma were found to have normal function in vitro, and responded 100 per cent to both collagen and ADP. These results indicate that the Ito Flow-Through Centrifuge can be used in plasmapheresis with heparin anticoagulation with no donor platelet loss and normal function in separated plasma.

Animals↗

PubMedDate not supplied

The effect of dopamine on tracheal smooth muscle.

Dose-response curves to dopamine were obtained on guinea-pig, dog and human tracheal smooth muscle. Dopamine produced a relaxation of the guinea-pig tracheal chain, and this relaxation was completely blocked by propranolol. The potency of dopamine as a beta-agonist was 1/10 000 that of isoprenaline, 1/250 that of adrenaline and 1/50 that of noradrenaline. In human and dog tracheal smooth muscle, dopamine induced a contraction which could be entirely abolished by alpha-adrenoceptor antagonists. As an alpha-agonist, the potency of dopamine was 1/20 that of adrenaline and noradrenaline. Our data also show that a dopamine induced contraction is greatly potentiated if the smooth muscle specimen has been previously slightly contracted with histamine. We conclude that there are few, if any, specific dopaminergic receptors in the airways. Dopamine acts on both alpha- and beta-adrenoceptors, but in humans and dogs, its effect is predominantly on alpha-adrenoceptors.

Animals↗

PubMedDate not supplied

Effect of chronic low dose aspirin on platelet and vascular eicosanoid metabolism in nonhuman primates (Macaca fascicularis).

It has been suggested that inhibition of platelet cyclooxygenase by chronic low dose aspirin may spare vascular prostacyclin production. Conventional doses of aspirin (greater than 5 mg/kg) have been shown to inhibit the generation of both thromboxane A2 and prostacyclin. Low dose aspirin inhibits prostacyclin production by excised human venous tissue, thus questioning the selectivity of such regimens. However, many clinical and surgical conditions requiring platelet inhibition involve the arterial system. We have studied the effects of various aspirin regimens on platelet, venous, and arterial cyclooxygenase activity in a nonhuman primate (Macaca fascicularis). We determined the lowest chronic dose of oral aspirin required to effectively inhibit platelet cyclooxygenase and aggregation to be 1 mg/kg. After 14 days of 0, 1, or 2 mg/kg aspirin, intact veins and arteries were surgically removed and perfused, and luminal prostacyclin (6-keto-PGF1 alpha) generation was assessed. Levels of 6-keto-PGF1 alpha in venous perfusates were reduced by 89% and 86% (p less than 0.05) after 1 and 2 mg/kg, respectively. Arterial 6-keto-PGF1 alpha levels were unchanged by 1 mg/kg aspirin, but after 2 mg/kg were reduced by 66% (p less than 0.05). Preferential inhibition of platelet over arterial cyclooxygenase is thus achievable, but only over a narrow dose range.

6-Ketoprostaglandin F1 alpha↗

PubMedDate not supplied

Interaction of ethanol, prostacyclin, and aspirin in determining human platelet reactivity in vitro.

Ethanol partitions into cellular membranes and alters membrane-associated phenomena in numerous cell types. Since platelet aggregation and its inhibition by prostacyclin are mediated by membrane-associated receptors and enzymes, we examined the interaction of ethanol, prostacyclin, and aspirin on human platelet reactivity. Using platelet-rich plasma, we examined the effect of increasing concentrations of ethanol (0.05% to 1.0%) on the platelet-inhibitory effects of a submaximal dose (5 x 10(-10) M) of prostacyclin, the concomitant production of cyclic 3',5'-adenosine monophosphate (AMP), and the release of thromboxane A2. Ethanol alone had little effect on platelet aggregation induced by 5 micrograms/ml collagen; however, it potentiated the inhibitory effect of prostacyclin on platelet aggregation in a dose-dependent manner in the range of 0.05% to 1.0% ethanol. Whereas prostacyclin increased platelet cyclic AMP levels, ethanol had no further effect on cyclic AMP levels. Ethanol alone reduced thromboxane A2 generation, but this effect could not totally account for the observed interaction of ethanol and prostacyclin on aggregation, since aspirin did not totally abolish the interaction. The dose range in which the ethanol/prostacyclin/aspirin interactions occur encompasses the plasma levels of ethanol that may be achieved by the consumption of alcoholic beverages. The results may, in part, explain the dose-related physiological and pathological consequences of chronic alcohol consumption on the cardiovascular system.

Aspirin↗

PubMedDate not supplied

[Geriatric digestive surgery. An analysis of 163 cases].

The aim of our study is to analyze the clinical features and outcome of digestive surgery in the aged. From Jan. 1979 to Dec. 1981, 1,389 operations under general anesthesia were performed on patients 75 years old and more. From this group, 163 patients (111 females and 52 males, mean age: 79 +/- 0.7 years) underwent surgery of the alimentary tract. The procedures were divided in: colorectal (48%), biliary (32%), gastric (10%), small bowel (6%), esophagus (1%) and others (3%). An operation for cancer was performed in 63 patients: palliative (69%), curative (31%). The mean length of hospital stay is 23 days (pre-op 7 days, post-op 16 days). Only 16% of the patients needed intensive care. Postoperative complications occurred in 43 patients (26%); cardiovascular (47%), psychiatric (26%), pulmonary (23%) and others (4%). The overall mortality rate is 10%: 6% for elective cases and 24% for urgent cases (49 patients). The mortality is related to: sepsis and peritonitis (53%), cardiopulmonary disease (23%), hemorrhage (12%), cachexia (12%). At discharge, 62% of the patients returned home directly, 18% to convalescent homes, 10% to unknown places and 10% in nursing homes. Our data supports the benefit of surgery in the aged.

Aged↗