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Biomedical subjects

M Arad

Publications and source records attributed to M Arad.

At least 37 records · Page 2Linked to original sources
PubMed1993

The effects of continuous operation in a chemical protective ensemble on the performance of medical tasks in trauma management.

Treating casualties in a chemically hazardous environment constitutes a unique problem. Physical protection of the medical personnel may impair their performance and potentially affect patients' prognoses. The present study examined the effect of prolonged physical protection on the accomplishment of medical tasks related to trauma management. Sixty one emergency medical technicians, acclimatized to operating in protective gear, underwent four rounds of testing during eight hours of continuously wearing either a chemical protective suit or regular fatigues. The quality of the designated medical tasks, including sterility, was maintained throughout the study. A significant reduction in speed of performance was noted (approximately 30% slowing, p < 0.0001 in multivariate analysis) because of protective clothing. There was no additional decrement in performance following a prolonged stay in the protective gear. We conclude that in a chemically contaminated area, fully protected medical personnel are capable of treating trauma patients reasonably well, and for a relatively long period of time. The importance of pretraining and proper instruction is emphasized.

Acclimatization↗
PubMed1993

Postexercise syncope: evidence for increased activity of the sympathetic nervous system.

This report describes an association of postexertional syncope with increased levels of circulating catecholamines. A 36-year-old male who experienced postexercise bradycardia and asystole had higher basal plasma norepinephrine (120 versus 68 +/- 6 pg/ml) and epinephrine (18 versus less than 10 pg/ml) but a similar vagal tone (vagal tone index of 5.44 versus 5.81 +/- 1.00 U) when compared with 6 closely matched subjects who underwent an uneventful stress test.

Adult↗
PubMed1992

Safety of pyridostigmine in hypertensive patients receiving beta blockers.

In the last decade, pyridostigmine, a quaternary carbamate that reversibly inhibits the enzyme acetylcholinesterase, was proposed for pretreatment of nerve gas (organophosphate) poisoning. The objective of this study was to assess the cardiovascular effects of pyridostigmine in patients treated with beta blockers. Eight hypertensive patients receiving regular treatment with beta blockers were randomized in a double-blind crossover study to receive pyridostigmine (30 mg 3 times daily) or placebo for 2 days. Heart rate and blood pressure in the supine and standing positions were recorded every 2 hours during the day, and 24-hour Holter monitoring was performed. In addition, a symptom-limited exercise test was performed, and plasma catecholamine levels were determined at rest and at peak exercise. Pyridostigmine, as compared with placebo, did not induce any significant effect on heart rate, plasma catecholamine levels or resting blood pressure. Both systolic and diastolic blood pressures increased in accordance with exercise intensity (p less than 0.01), although a significantly lower diastolic blood pressure was observed when pyridostigmine was used (average decrease 5 mm Hg compared with placebo; p less than 0.01). No clinical adverse reactions were observed, confirming the relative safety of the combination of low-dose pyridostigmine with beta-adrenergic blocking agents.

Adrenergic beta-Antagonists↗
PubMed1992

Effects of captopril on metabolic and hemodynamic alterations in global ischemia and reperfusion in the isolated working rat heart.

In the isolated working rat heart model, we studied metabolic and hemodynamic effects of 5- and 30-min global ischemia followed by reperfusion and assessed the potentially beneficial effect of captopril 80 micrograms/ml added throughout the experiment. Creatine kinase (CK) and catecholamines were measured in coronary effluent. De novo eicosanoids (prostaglandin E2) synthesis was assessed in endocardial explants. Hemodynamic alterations occurred after 30-min ischemia and were reflected most dramatically by a reduction in cardiac output (CO 72 +/- 10% of baseline values in captopril vs. 68 +/- 16% in controls) without significant differences as a result of treatment. Captopril shortened reperfusion ventricular fibrillation (VF) duration (6.9 +/- 1.2 vs. 13.6 +/- 8.7 min, p less than 0.05) but had no effect on VF incidence. No differences occurred in norepinephrine (NE) outflow, whereas total CK release was greater in controls. Five controls versus none of the treated hearts (p less than 0.05) released trace amounts of epinephrine during reperfusion. Increased de novo PGE2 synthesis was demonstrated after 5-min I (465 +/- 168 vs. 238 +/- 75 pg/100 mg tissue per hour, p less than 0.01). Captopril stimulated production of PGE2 in normoxic hearts (p less than 0.02), but the difference was no more apparent in ischemic hearts. We conclude that captopril produces some biochemical and electrophysiologic evidence of myocardial salvage, but these effects are not sufficient to induce hemodynamic improvement after global ischemia and reperfusion.

Animals↗
PubMed1992

The effects of powered air supply to the respiratory protective device on respiration parameters during rest and exercise.

The common chemical warfare protective masks impose an excessive respiratory load on the wearer due to elevated breathing resistance and increased dead space. For patients with severe respiratory disease, the excessive respiratory effort may be intolerable. Besides, the substantial negative pressure created within the mask during inspiration may result in an inward leakage in individuals having difficulties with proper facial fitting of the mask. The purpose of the current investigation was to evaluate the effects of a blower, actively driving air, through the mask's filter, at a flow (mean +/- SD) of 42 +/- 2 L/min, on respiratory parameters during rest and moderate exercise. Ten healthy subjects of either sex participated in two experimental sessions, wearing the mask with and without the blower. Each session included 6 min of sitting at rest and 6 min of walking on a treadmill (3.2 mph, and 10 percent grade). In nine of the subjects, the active air supply produced a positive inspiratory pressure at rest (5 +/- 4 vs -24 +/- 9 mm H2O peak inspiratory pressure with and without the blower, respectively, p < 0.0001). Inspiratory carbon dioxide concentration (FICO2) at rest was diminished (0.4 +/- 0.4 vs 1.3 +/- 0.7 percent with and without the blower, respectively; p < 0.01) while FIO2 increased from 19.5 +/- 0.7 percent to 20.6 +/- 0.4 percent with the device (p < 0.01). These changes were associated with a significant decrease in respiratory rate (15 +/- 2 vs 18 +/- 3 per minute, p < 0.01). During exercise the blower barely decreased the negative inspiratory pressures, had no effect on other respiratory parameters measured, but significantly shortened the inspiratory/cycle-length time ratio (0.46 +/- 0.03 vs 0.53 +/- 0.03, p < 0.005). The effects of active air supply were not different between male and female subjects. We conclude that the blower is expected to be a useful accessory to respiratory protective devices for patients with pulmonary disease.

Adult↗
PubMed1992

Epicardial versus endocardial "in mirror" changes in prostaglandin synthesis after short periods of ischemia and reperfusion.

Cardiac ischemia and reperfusion are associated with increased prostaglandin levels in the coronary venous effluent. This study implemented an in vivo-in vitro technique to investigate regional alterations in heart tissue PGE2 and PGF2 alpha de novo production. Canine endocardial and epicardial explants were incubated following 5 min regional ischemia, or 5 min ischemia with 10 min reperfusion, induced in vivo in two groups of animals (n = 10 and 6, respectively). Ischemia produced a significant upsurge in endocardial but not in epicardial prostaglandin synthesis as compared with the non-ischemic zone: 7.6 +/- 0.7 versus 4.5 +/- 0.5 pg/mg tissue per h in PGE2 (P < 0.001) and 8.8 +/- 1.2 versus 6.8 +/- 1.2 pg/mg per h PGF2 alpha (P < 0.01). Following reperfusion, PGE2 was higher in the apparently normal than in the affected endocardium (5.8 +/- 0.6 versus 4.4 +/- 0.5 pg/mg per h, P < 0.05). Opposite changes occurred in the reperfused epicardium: 8.2 + 0.9 versus 4.9 +/- 0.7 pg/mg per h PGE2 (P < 0.01) and 11.1 +/- 0.9 versus 6.0 +/- 0.6 pg/mg per h PGF2 alpha (P < 0.001), for the reperfused as compared to the "normal" region, respectively. Our findings imply that the left ventricular wall is not homogeneous in its eicosanoid response to ischemia and reperfusion. "In mirror" changes were found between endocardium end epicardium and between the injured and the apparently normal regions.

Animals↗
PubMed1992

Medical limitations of gas masks for civilian populations: the 1991 experience.

Using a gas mask (GM) may involve considerable inconvenience, impairment of respiration and communication, and serious psychological reactions. The medical literature is primarily focused on the occupational aspects of using the GM by young and healthy workers. In contrast, there is hardly any information concerning the use of GMs by large, unselected populations, including children, the elderly, and the sick. Issuing GMs to all residents of Israel prior to Operation Desert Storm created an urgent need to define the populations whose health might be jeopardized by using the standard GM. Adding an active air supply system (AASS) to a standard GM may ease the burden on this high-risk group. We evaluated the physiological aspects of breathing with a GM, with and without AASS, in respect to pathophysiology of diseases, and reached a set of criteria for identifying those who may be endangered by a GM and are expected to benefit from the AASS. The method used to sort and identify those entitled to the AASS is described.

Chronic Disease↗
PubMed1992

Effects of heat-exercise stress, NBC clothing, and pyridostigmine treatment on psychomotor and subjective measures of performance.

This study investigated the effects of pyridostigmine pretreatment, NBC protective gear, and heat-exercise exposure on psychomotor performance and subjective sensations in eight healthy male volunteers. Exercise in heat enhanced performance of vertical addition (+7.3%, p less than 0.001) but prolonged the reaction time (+4.4%, p less than 0.01). The effects of pyridostigmine, protective gear, and the interactions between the various stressors were not significant. Cognitive performance was not dependent on body core temperature. Multiple complaints of subjective discomfort arose from wearing the protective garment. The results suggest the existence of a significant subjective discomfort but an absence of major cognitive decrements in a multiple-stresses state of chemical warfare alertness.

Exercise↗
PubMed1990

The effect of swimming exercise on spontaneous ventricular defibrillation and ventricular fibrillation threshold in the isolated perfused rat heart.

Effects of swimming exercise training on left ventricular contraction and relaxation, the incidence of spontaneous defibrillation and the ventricular fibrillation threshold were studied in the isolated, perfused rat heart. The heart/body weight ratio was 4.8 +/- 0.4 x 10(-3) in swimmers compared with 3.9 +/- 0.6 x 10(-3) in sedentary controls (p less than 0.0005). The spontaneous heart rate was lower in isolated hearts of trained animals (222 +/- 18 bpm compared with 244 +/- 28, p less than 0.05). Left ventricular systolic pressure was higher in trained hearts and the rate of ventricular relaxation enhanced (p less than 0.05). The ventricular fibrillation threshold was 7.2 +/- 5.2 and 10.8 +/- 6.1 mamp in hearts of swimmers and controls, respectively, the difference not being significant. The incidence of spontaneous defibrillation was not significantly different between the two groups. It is concluded that, while swimming induces cardiac hypertrophy and hemodynamic changes, it neither protects against the induction of ventricular fibrillation nor facilitates spontaneous defibrillation in the isolated, non-ischemic rat heart.

Animals↗
PubMed1990

Heat-exercise performance of pyridostigmine-treated subjects wearing chemical protective clothing.

Pyridostigmine bromide is currently the pretreatment of choice for operation in a chemical warfare (CW) environment. Under CW conditions, subjects are exposed to thermal stress caused by CW protective clothing. This investigation was conducted to determine if pyridostigmine affects various physiological and biophysical parameters of human temperature regulation in subjects wearing CW protective clothing. Pyridostigmine was administered orally in a randomized double-blind cross-over study in four doses of 30 mg every 8 h. An average of 33% whole blood cholinesterase inhibition was induced in the pyridostigmine treated group 4 h after ingestion of last tablet. The subjects were exposed to 170 min exercise-heat stress (Tdb = 33 degrees C; rh = 60%) consisting of 60 min in a sitting position and two 50-min walks (1.39 m.s-1, 5% grade) separated by 10 min of rest. Non-evaporative heat exchange was significantly higher, -14.0 and -10.6 W.m-2 (p less than 0.03), for the pyridostigmine-treated subjects. No additional differences were found between treatments in the physiological responses and heat balance parameters at the end of exposure: heart rate (HR) was (mean +/- S.D.) 154 +/- 16 and 151 +/- 24 bpm, rectal temperature (Tre) was 39.0 +/- 0.4 and 38.9 +/- 0.2 degrees C, heat storage over the 2 h of exercise was 62 +/- 15 and 70 +/- 15 W.m-2, and sweat rate was 832 +/- 185 and 748 +/- 52 g.h-1, in the pyridostigmine and placebo treatments, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Prostaglandins and the antiarrhythmic effect of preconditioning in the isolated rat heart.

Our study evaluated the relationship between the endogenous production of prostacyclin and the antiarrhythmic effect of ischemic preconditioning against ischemic and reperfusion-induced tachyarrhythmia. Langendorff perfused rat hearts underwent 30 min regional ischemia with reperfusion. Preconditioning was induced by a single episode of 5 min ischemia and 15 min reperfusion. Prostaglandin 6-keto F1 alpha (a stable metabolite of prostacyclin) was determined in the coronary effluent. In the control group the incidence of tachyarrhythmia was 31% during ischemia and 67% during reperfusion. Preconditioning did not affect ischemic arrhythmias but attenuated arrhythmias a reperfusion (8%, p < 0.01) and was associated with increased release of prostacyclin prior to reperfusion. Aspirin abolished the antiarrhythmic effect of preconditioning against reperfusion tachyarrhythmias. However, no relationship was found between suppression of prostacyclin production and the occurrence of arrhythmia in individual hearts. Thus, our findings suggest that metabolites of arachidonic acid via the cyclooxygenase pathway are involved in the protective effect of ischemic preconditioning against reperfusion-induced tachyarrhythmias.

6-Ketoprostaglandin F1 alpha↗
PubMedDate not supplied

In vivo assessment of the inotropic and toxic effects of oxidized ouabain.

Oxidized ouabain, a product of the oxidative cleavage of the rhamnose ring in ouabain has been found to have a higher inotropic toxic ratio in cultured cardiac myocytes. The purpose of our study was to evaluate the efficacy and toxicity of oxidized ouabain in comparison with ouabain in intact animals. Drugs were infused to healthy cats; the positive inotropic effect, and the time-course of development of arrhythmia were followed and recorded until death. Oxidized ouabain was associated with a higher increase in arterial blood pressure, a mean increase of 41 +/- 19% as compared with 21 +/- 8% in the ouabain group (p < 0.10). There were no significant differences in maximal increases of dP/dt or dP/dt/P (65 +/- 29%, 28 +/- 10% for oxidized ouabain and 49 +/- 16%, 27 +/- 11% for ouabain, respectively). The mean doses causing persistent arrhythmia (toxic dose) were 93 +/- 23 micrograms/kg of oxidized ouabain vs 39 +/- 14 micrograms/kg of ouabain. Lethal arrhythmias were produced by 215 +/- 46 micrograms/kg of oxidized ouabain and 62 +/- 16 micrograms/kg of ouabain. The ratio of toxic to lethal doses was 0.62 +/- 0.11 for ouabain vs 0.45 +/- 0.09 for oxidized ouabain (p < 0.05), but the inotropic to toxic dose ratios were not different. We conclude that oxidized ouabain acts similarly to the known cardiac glycosides in doses which produce inotropic effects in cats, has a lower potency as compared to ouabain, and appears to have a more benign course of intoxication.

Animals↗
PubMedDate not supplied

The effect of heart rate on the termination of electrically induced ventricular fibrillation in the isolated perfused rat heart.

Ventricular fibrillation (VF) which is normally sustained in large animals and humans, is transient in small animals. The purpose of the present study was to evaluate the possible effect of changing cardiac rate on spontaneous ventricular defibrillation. In isolated perfused rat heart, VF was electrically induced during normal spontaneous rhythm of the heart at normal rate and at various ventricular pacing rates. It was found that: 1) Electrically induced VF in isolated perfused, non-ischemic rat heart spontaneously terminated in 88% of the hearts; 2) Ventricular pacing rhythm of spontaneous rate plus 10% caused VF to be sustained in 26% of the hearts (which defibrillated spontaneously during normal rates); 3) Ventricular pacing at 200% of the basic rate led to sustained VF in about half the VF episodes (14 out of 33, p less than 0.005). In the remainder, which defibrillated spontaneously, a sustained VF could be achieved by further increase in ventricular pacing rate; 4) Slow pacing rate, as a result of the surgical production of atrioventricular (A-V) block, enhanced the probability of spontaneous defibrillation (21 of 21 episodes after slow pacing vs 24 of 34 episodes following pacing at previous normal sinus rhythm, p less than 0.05). Selective modulation of conduction velocity, refractory period or both, achieved by changes in ventricular pacing rate was assumed to play an important role in determining whether electrically-induced VF would be transient or sustained.

Animals↗
PubMedDate not supplied

The effect of calcium concentration on spontaneous ventricular defibrillation and VF threshold.

In order to investigate the influence of the effective refractory period on spontaneous ventricular defibrillation, isolated rat hearts were perfused with Krebs-Henseleit solution containing 0.5, 2.7 and 5.1 mM calcium. After measuring the fibrillation threshold at spontaneous rate (SR), ventricular fibrillation (VF) was induced during basic ventricular pacing of 110% SR, or the highest rate permitting 1:1 electromechanical coupling. The VF threshold was significantly reduced from 13.6 +/- 3.5 to 7.9 +/- 5.3 and 5.1 +/- 3.4 mA at 0.5, 2.7 and 5.1 mM Ca++ concentrations, respectively. The incidence of spontaneous recovery from VF, induced during basic pacing, was 100%, 83% and 50% at calcium concentrations of 0.5, 2.7 and 5.1 mM, respectively, (p less than 0.01 for the incidences at 0.5 mM versus 5.1 mM Ca++). The incidence of spontaneous defibrillation decreased when the hearts were driven rapidly, with spontaneous recovery rates of 92%, 58% and 0% (p less than 0.0001] for corresponding increases in Ca++ concentration. Induced ventricular fibrillation of fine morphology was frequently observed at 5.1 mM Ca++. It appears that progressive impairment of spontaneous defibrillation is caused by an increase in calcium concentration, this effect being more pronounced at high ventricular rates. Variations in the effective refractory period, caused by alterations in extracellular calcium concentration and differences in intracellular Ca++ accumulation, may account for the above results.

Animals↗
PubMedDate not supplied

Rehabilitation outcomes in patients with full weight-bearing hip fractures.

Evaluation of the functional outcome for hip fractured elderly patients has been controversial due to a typical casemix containing both weight bearing and non weight bearing postoperative fractures. The purpose of this study was to investigate factors associated with rehabilitation outcomes in patients who are able to fully weight bearing following surgical repair of femoral neck fracture. We studied 217 consecutive patients admitted for rehabilitation after surgery for hip fracture. Age, gender, marital status, type of fracture and admission Functional Independence Measure (FIM) were evaluated as possible predictors of rehabilitation outcome. Functional gains were evaluated according to FIM. Dependent outcome variables were calculated as absolute (total FIM gain and daily FIM gain) as well as relative (to potential). Results showed a significant improvement in absolute total and daily FIM gains (19.32+/-8.29, and 0.87+/-0.44, respectively). Relative total functional gain was 0.40+/-0.19. Absolute total functional gain did not depend on FIM admission, whereas all other parameters were significantly correlated with FIM scores on admission, indicating a relatively adverse rehabilitation in patients with an admission FIM of 40 points or lower. The majority (83.9%) of patients were discharged home. A significant association exists between the ability to go home and marital status (P=0.009), as well as with admission FIM (P<0.0001). We conclude that encouraging outcome results are achieved in the elderly with full weight bearing fractures. The absolute functional gains do not depend on FIM admission scores and argues for inclusion of patients with low admission FIM scores to rehabilitation programs. However, the relative gains are significantly better in patients with higher admission FIM scores, thus supporting inclusion of selected patients. This poses serious ethical issues for healthcare policy-makers.

Journal Article↗
PubMedDate not supplied

Clock drawing task, mini-mental state examination and cognitive-functional independence measure: relation to functional outcome of stroke patients.

The use of reliable and valid brief cognitive screening instrument for selecting the appropriate candidates for stroke rehabilitation is crucial. Clinicians often face the question which test should be preferred, that will best correlate with functional outcome. The objective of this study was to compare the clock drawing task with other cognitive tests used for the evaluation of discharge functional outcome in elderly stroke patients. We conducted a retrospective chart study including 151 consecutive patients, admitted for inpatient comprehensive rehabilitation following acute stroke. The clock drawing task (CDT), mini-mental state examination (MMSE) and the cognitive-functional independence measure (cognFIM) were used to assess the cognitive status. Functional status outcome was evaluated by the functional independence measure (FIM), using absolute and relative parameters of efficacy and efficiency. Correlation coefficients (Pearson correlation) between the three cognitive tests resulted in r-values ranging from 0.51 to 0.59 (P<0.001). All three tests correlated significantly with motor outcomes. MMSE did not confer additive value to CDT. It is concluded that CDT is similar to mini-mental and both are somewhat better than cognFIM with respect to the evaluation of functional status outcome following stroke. The correlations between the tests as well as the simplicity of administration favor the use of either CDT or MMSE in the initial assessment of elderly stroke patients.

Journal Article↗