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Biomedical subjects

J A Madden

Publications and source records attributed to J A Madden.

63 records · Page 4Linked to original sources
PubMed1978

Failure of low dose heparin to prevent pulmonary embolism after hip surgery or above the knee amputation.

In a randomized, double-blind trial, 5,000 USP units of sodium heparin or saline were give subcutaneously at least two hours before surgery and at 12 hour intervals thereafter to patients requiring total hip replacement, surgical correction of hip fracture, or major lower extremity amputation for vascular insufficiency. Lung perfusion scans were performed before surgery and at weekly intervals during the postoperative period. Pulmonary arteriograms were requested in patients developing new perfusion defects on serial scans. Two hundred twelve patient hospitalizations were analyzed. We diagnosed acute pulmonary embolism by serial lung perfusion scans or at autopsy in 37 patients. The incidence of pulmonary embolism in 40 patients with below the knee amputation was too low to warrant conclusions. The incidence of acute pulmonary embolism in 94 patients undergoing above the knee amputation was 25% in patients receiving heparin and 27% in patients receiving saline. The incidence of acute pulmonary embolism in 78 patients undergoing hip surgery was 13% in patients receiving heparin and 12% in patients receiving saline. We conclude that the regimen used had no significant effect on the incidence of acute pulmonary embolism in patients undergoing hip surgery or above the knee amputation.

Acute Disease↗
PubMed1975

Sodium kinetics in aorta of spontaneously hypertensive rats.

Transport rate constants (kij) for Na exchanges in isolated aorta of normotensive and spontaneously hypertensive rats (SHR) were determined with the use of 33Na as a tracer and the aid of digital computer simulation. A three-compartment model consisting of 1) extracellular, 2) intracellular, and 3) "endointracellular" spaces (compartments) was found to describe adequately the kinetics of 22Na. Results show that in SHR: I) K01, which is related to the overall Na outflow from tissue, was increased by 41%; ii) k12, describing Na movements from intra- to extracellular compartment, was increased by 67%; iii) k21, representative of Na movements from extra-to intracellular compartment, was decreased by 39%. These results indicate a faster turn-over of Na and a relative accumulation or translocation of Na into the extracellular space in aorta of SHR. The findings are interpreted in the light of recent reports on the role of Na in contractile response or reactivity of arteries. A humoral mechanism operative at the arterial wall level for the development of hypertension is at the arterial wall level for the development of hypertension is suggested. The main significance of the methodology employed in this work is that the values found for the kij are not subject to fluctuations intrinsic to auxiliary indicators of extracellular space.

Animals↗
PubMedDate not supplied

Seizures induced by the cocaine metabolite benzoylecgonine in rats.

The half-life (t1/2) of cocaine is relatively short, but some of the consequences of its use, such as seizures and strokes, can occur hours after exposure. This led us to hypothesize that a metabolite of cocaine may be responsible for some of those delayed sequelae. We evaluated the potential of the major metabolite of cocaine, benzoylecgonine (BE), to cause seizures. Two separate equimolar doses (0.2 and 0.4 mumol) of either cocaine or BE were injected ventricularly in unanesthetized juvenile rats. Treated rats were then evaluated for incidence, latency, and seizure pattern or for locomotor activity in animals without seizures. BE-Induced seizures occurred more frequently and had significantly longer latencies than those induced by equimolar amounts of cocaine. Whereas cocaine-induced seizures were best characterized as brief, generalized, and tonic and resulted in death, those induced by BE were prolonged, often multiple and mixed in type, and rarely resulted in death. Electrical recordings from the hippocampus showed a rhythmic progression in EEG frequency and voltage with clinical seizure expression. BE-Injected rats that did not have seizures had significantly more locomotor activity than cocaine-injected animals without seizures. The finding that cocaine- and BE-induced seizures differ in several respects suggests more than one mechanism for cocaine-induced seizures and emphasizes the importance of a cocaine metabolite, BE.

Animals↗
PubMedDate not supplied

Cellular actions of halothane on cat cerebral arterial muscle.

The effects of halothane on intracellular membrane potential (Em) and force development in cat MCA were studied. Halothane (0.07-0.14 mM/1) relaxed isolated MCA which had developed myogenic tone. Measurement of Em showed that halothane depolarized this preparation in a dose-dependent fashion in the face of vessel relaxation, demonstrating uncoupling of electrical and mechanical activity. Halothane markedly inhibited the contractile effects of histamine and serotonin suggesting that, apart from its direct action on cerebral arterial tone, it also blunts the action of vasoactive agents. When this preparation is partially depolarized from -62 to -50 mV with excess K+, halothane, while having only a small (1.2 mV) additional depolarizing effect, consistently elicits contraction rather than relaxation. Thus, the action of this particular volatile anesthetic on cerebral arteries can depend upon the resting level of Em. These studies indicate that halothane relaxes myogenic tone in cat MCA by an intracellular mechanism, but that the direction of its effect (i.e., relaxation vs. contraction) may depend upon the prior level of Em and muscle cell activation.

Animals↗