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R E Jackson

Publications and source records attributed to R E Jackson.

51 records · Page 3Linked to original sources
PubMed1981

Effects of chronic digitalization on cardiac and renal Na+ + K+-dependent adenosine triphosphate activity and circulating catecholamines in the dog.

To extend our understanding of the mechanism of action of digitalis drugs, we studied electrocardiograms (ECGs), renal function, plasma concentrations of catecholamines, and myocardial and renal Na+ + K+-dependent adenosine triphosphate (Na+ + K+ ATPase) activity in chronically digitalized dogs. Five healthy, male, mongrel dogs received a therapeutic regimen of digoxin (0.1 mg/kg on day 1 in three divided doses followed by 0.025 mg/kg per day) orally for 2-4 months. This resulted in plasma digoxin concentrations of 1.1 to 4.7 ng/ml as determined by radioimmunoassay. Six control dogs received daily gelatin capsules by mouth. ECGs monitored throughout the study showed no changes. Digitalized dogs had elevated plasma norepinephrine concentrations (347 vs. 137 pg/ml in controls) and no change in plasma epinephrine concentrations. Digitalized dogs had elevated glomerular filtration rates (0.74 vs. 0.94 ml/min per g of kidney) without significant changes in renal handling of electrolytes and water. All of the above studies were done without the aid of restraining drugs or infusions. The animals were killed with an overdose of pentobarbital for in vitro studies. In digitalized dogs, microsomal Na+ + K+ ATPase-specific activity was 26 to 33% lower in the renal cortex, medulla, and papilla, and 46% lower in the cardiac left ventricle than in control dogs. Digitalization did not alter the osmolalities of renal tissues. We conclude that chronic reduction Na+ + K+ ATPase activity by one-third dose does not cause abnormalities in renal handling of electrolytes and water, and inhibition of Na+ + K+ ATPase in the left ventricular muscle by one-half is associated with no obvious ECG changes in the dog. Further, elevated plasma norepinephrine concentrations may contribute to both the therapeutic and the toxic effects of digitalis.

Animals↗
PubMed1976

Amelioration of the symptoms of acute mountain sickness by staging and acetazolamide.

Treatment by 4 d of residence at 1600 m plus the administration of 500 mg acetazolamide b.i.d. for the last 2 d at 1600 m and the first 2 d at 4300 m was compared with no treatment prior to ascent to 4300 m for prophylaxis of acute mountain sickness. The treatment successfully prevented almost all symptoms of acute mountain sickness. It had no effect on the diminished capacity for maximal or prolonged heavy physical work. The treatment produced a relative acidosis and a comparatively greater arterial oxygen tension at 4300 m.

Acclimatization↗
PubMedDate not supplied

Use of two-dimensional echocardiography for the diagnosis of pulmonary embolus.

We investigated the diagnostic utility of transthoracic echocardiogram (2-D ECHO) in identifying acute right heart strain in patients with suspected pulmonary embolus (PE) undergoing a pulmonary angiogram during their hospitalization. A retrospective case control study was conducted over a 3-year period at a tertiary, community teaching hospital. Patients were eligible if they had a pulmonary angiogram and a transthoracic echocardiogram. Cases were defined as an angiogram positive for PE and controls were defined as an angiogram negative for PE. We excluded cases in which the time interval between 2-D ECHO and angiogram was greater than 2 days. The 2-D ECHO was considered positive for right heart strain if two of the following were present: enlarged right ventricle, moderate or severe tricuspid regurgitation, increased right ventricular pressures, or paradoxical septal wall motion. We were able to identify 71 patients, of whom 24 met our criteria for PE. Of these, 13 had an echocardiogram consistent with our definition of acute right heart strain, for a sensitivity of 0.54. Forty-six of the 47 patients without PE did not have findings of acute right heart strain. The echocardiogram was positive in 14 patients, for a positive predictive value of 0.93. In seven patients with systolic blood pressures of less than 100 mmHg, five had a PE, all of whom met our criteria for acute right heart strain. We conclude that 2-D ECHOs show promise in identifying PE and hemodynamic compromise as a result of PE, and that further studies are warranted.

Adult↗
PubMedDate not supplied

Impact of lay responder actions on out-of-hospital cardiac arrest outcome.

INTRODUCTION: Little peer-reviewed literature exists regarding the actions of the person who recognized and called 911 at the time of an out-of-hospital cardiac arrest (OHCA). OBJECTIVES: To describe the characteristics of persons who recognized OHCAs and to assess the impact of their actions on survival. METHODS: Subjects were a convenience sample of individuals who called 911 after a case of home OHCA in which the victim was transported to one of two suburban community teaching hospitals. A retrospective mail survey was conducted asking demographics, including age, race, educational level, prior first aid training, and actions upon recognition of OHCA, including phone calls made and caller estimate from collapse to 911 call. Callers whose initial action was calling 911 were compared with those who made other calls first. Outcomes (discharged alive, DC) were obtained from hospital records. Fisher's exact test and chi-square tests were used for analysis. RESULTS: Of 378 cases, 173 (45.8%) responded to the mail survey. The lay responders (LRs) who called 911 were younger than the victims (59.9 vs 68.0, p < 0.001) and were most commonly spouses (65.3%) or adult children (22.0%) of the patient. Most (84.7%) called 911 first at the time of recognition of arrest. A first call to 911 tended to predict DC (11.0% vs 0.0%, p = 0.13). When a phone call other than 911 was made first, there were no survivors (0/23). An estimated delay to 911 call of >4 minutes was not associated with an adverse outcome (10.5% vs 6.9%, p = 0.49). There was no difference in demographic variables between immediate and delayed 911 callers. CONCLUSION: Lay responder demographics are similar to those of patients. In this study, an LR call to 911 first appears to be associated with improved OHCA survival. The LR estimates of delay to 911 call were not associated with increased mortality. The authors identified no patient or witness characteristics that were associated with a delay to calling 911 first.

Adult↗