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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The purpose of this investigation was to determine the effects of caffeine ingestion on maximal power output and fatigue during short term, high intensity exercise. Nine adult males performed 15 s maximal exercise bouts 60 min after ingestion of caffeine (7 mg.kg-1) or placebo. Exercise bouts were carried out on a modified cycle ergometer which allowed power output to be computed for each one-half pedal stroke via microcomputer. Peak power output under caffeine conditions was not significantly different from that obtained following placebo ingestion. Similarly, time to peak power, total work, power fatigue index and power fatigue rate did not differ significantly between caffeine and placebo conditions. These results suggest that caffeine ingestion does not increase one's maximal ability to generate power. Further, caffeine does not alter the rate or magnitude of fatigue during high intensity, dynamic exercise.
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PMID:Caffeine, maximal power output and fatigue. 322 80

The purpose of these studies was to evaluate the effects of chronic caffeine ingestion on the myocardium during fetal and neonatal growth and development. The isolated perfused working heart preparation was used to evaluate cardiac function. During gestation and lactation, one group of dams consumed a caffeine supplemented diet (10 mg/kg/day). Their offspring were sacrificed and the hearts analyzed 50 days after birth. We found that the intake of caffeine by the dams resulted in significant increases in the offspring's coronary flow, peak systolic pressure, and myocardial work. A second group of dams ingested a diet containing caffeine (10 mg/kg/day) during lactation only. Their pups continued to consume the caffeine diet until 50 days. Pup hearts exhibited significant reductions in cardiac output, stroke volume, pressure development, myocardial work, and external efficiency when compared to controls. Caffeine did not affect body or heart weight or adipose size or number in these experiments. Thus, continued caffeine consumption following birth may alter cardiac performance of the offspring.
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PMID:Effect of chronic caffeine intake on myocardial function during early growth. 357 92

The effects on embryonic cardiac function of caffeine administration (two non-cardioteratogenic and two cardioteratogenic doses) to Hamburger-Hamilton stage 19 (3-3 1/2 days of incubation) chick embryos were investigated. Using microcinephotoanalysis, we have determined that caffeine (1.0-4.7 mg/egg), within the initial three hours after treatment, produced a dose-dependent decrease in end diastolic volume, stroke volume, cardiac output, and ejection fraction. These effects were sustained for a longer period of time following dosing at a cardioteratogenic level (3.5-4.7 mg/egg). Caffeine (1.0-4.7 mg/egg) also increased cardiac rate with a maximum increase of 30% seen 60 minutes after treatment with doses of 2.7 mg and 3.5 mg. However, the increase in cardiac rate was not related to dose. At 20 hours after treatment, caffeine increased stroke volume, ejection fraction and cardiac output relative to the controls. End-diastolic volume and cardiac rate were not changed. These results are evidence for a biphasic effect of cardioteratogenic dosing with caffeine during the first 20 hours after treatment--initially a sustained decrease in cardiac output, suggesting decreased flow through the embryonic heart, followed by an increase in ejection fraction, suggesting increased cardiac workload.
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PMID:The effects of cardioteratogenic doses of caffeine on cardiac function in the 3-day chick embryo. 362 79

A case of a severe heat stroke is reported in a 30 yr old white man while running a long-distance race. At the time of admission, moderate hyperthermia (40 degrees C) and coma were two major symptoms found at physical examination. Within 24 h, the clinical picture evolved to multiple organ failure with marked rhabdomyolysis, acute renal failure with hyperkalaemia and lactic acidosis. At this time, were also found a consumptive coagulopathy and acute hepatic failure. After numerous complications, most of them infectious, the patient was discharged after four months in ICU and admitted in a physical rehabilitation department. Muscle biopsy performed three years after the heat stroke showed an abnormal reactivity to caffeine, but a normal reaction to halothane. The relationship between malignant hyperthermia and heat stroke remains uncertain.
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PMID:[A severe form of heat stroke in a long-distance runner]. 377 73

While the caffeine induced cerebral vasoconstriction is well documented, the effects of oral ingestion of the drug in a dose range comparable to the quantities in which it is usually consumed and the intensity and duration of the associated reduction in cerebral circulation are unknown. Cerebral blood flow was measured via the 133Xenon inhalation technique before and thirty and ninety minutes after the oral administration of 250 mg of caffeine or a placebo, under double-blind conditions. Caffeine ingestion was found to be associated with significant reductions in cerebral perfusion thirty and ninety minutes later. The placebo group showed no differences between the three sets of cerebral blood flow values.
Stroke
PMID:Caffeine induced changes in cerebral circulation. 390 22

Experiments were conducted to determine whether chronic caffeine consumption during early growth and development affected cardiac performance and development of adipose tissue. Dams were fed a nutritionally complete diet with or without the addition of 10 mg/kg caffeine during lactation. After weaning, the pups were maintained on this diet until they were sacrificed at 88 days of age. Body weight at the time of sacrifice was comparable for both groups. The hearts from caffeine-fed animals were significantly (P less than 0.05) larger based on both dry and wet weights although the dry weight/wet weight ratios were similar. Ventricular function curves were generated on each heart using an isolated working heart preparation. The isolated hearts of caffeine-fed rats exhibited a significant reduction in cardiac output, stroke volume, mean aortic pressure, and estimated myocardial work when compared to controls. The rats fed caffeine had greater plasma triglyceride levels with no significant differences in adipocyte size or number in the epididymal and perirenal depots. It is concluded that chronic caffeine intake from birth may alter cardiac function of the offspring.
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PMID:Effects of chronic caffeine ingestion on growth and myocardial function. 400 Nov 33

We describe 2 patients with intracranial hemorrhage after ingestion of diet pills containing phenylpropanolamine (PPA) in combination with caffeine. The first patient had bilateral simultaneous intracerebral hemorrhages, and the second had a subarachnoid hemorrhage. PPA is widely used most often without prescription and causes intracranial hemorrhage more often than has been realized. The mechanism may be induction of a transient hypertensive crisis.
Stroke
PMID:Intracranial hemorrhages due to phenylpropanolamine. 400 67

The mechanisms by which caffeine typically elevates blood pressure (BP) in humans have not been previously examined using a placebo-controlled design. Accordingly, oral caffeine (3.3 mg/kg body weight, equivalent to 2 to 3 cups of coffee) was given on 2 days and a placebo was given on 1 day to 15 healthy young men using a double-blind, crossover procedure. All 3 test sessions were held during a week of caffeine abstinence. Multiple measurements were made on subjects at rest (baseline values) and over a 45-minute interval after ingestion of caffeine for BP, heart rate, systolic time intervals and thoracic impedance measures of ventricular function. Baseline measurements were highly reliable for each subject across all sessions and yielded means for placebo vs caffeine days that were not different. Caffeine increased systolic and diastolic BP (p less than 0.01) and decreased heart rate (p less than 0.05). The pressor effect was due to progressively increased systemic vascular resistance and resulted in greater stroke work (p less than 0.01). There was no indication that caffeine increased cardiac output or contractility. These actions of caffeine were replicable when each caffeine day was tested separately against the placebo day. These results suggest that caffeine use by persons with cardiovascular diseases should be examined to determine whether caffeine's enhancement of vascular resistance may contribute to systematic hypertension and/or create excessive demands for cardiac work.
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PMID:Effects of caffeine on vascular resistance, cardiac output and myocardial contractility in young men. 401 15

Caffeine is consumed by an estimated 95% of pregnant women. Yet, it is not known if caffeine alters embryonic cardiovascular function. We measured the effect of caffeine on mean and phasic dorsal aortic blood flow and mean vitelline artery pressure with a 20-MHz pulse Doppler velocity meter and a servo-null pressure system, respectively. We calculated vascular resistance, stroke volume index, and heart rate. We injected 5-microliters aliquots of anhydrous caffeine dissolved in chick Ringer's lactate into a vitelline vein in doses from 1.2 X 10(-5) mg (0.15 mg/kg) to 1.2 X 10(-2) mg (150 mg/kg). Control embryos received 5 microliters chick Ringer's lactate. The hemodynamic measurements were continuously recorded from 1 min prior through 5 min after injection. 9 stage 24 chick embryos were studied at each dose. The data were analyzed by one-way analysis of variance and Tukey's HSD test. Caffeine had no effect on heart rate, but a direct dose-related effect on mean dorsal aortic blood flow, stroke volume index, mean pressure, and vascular resistance. The effect of caffeine on stroke volume index at 5 min was a linear log-dose relationship [y = 0.155 + 0.02 1n (dose), p less than 0.001]. In the chick, caffeine acutely affects cardiovascular function by increasing myocardial contractility and dilating resistance vessels. We speculate this action is mediated through direct cellular effects: increase in free Ca++ and cyclic adenosine monophosphate.
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PMID:Effect of caffeine on cardiovascular function in the stage 24 chick embryo. 647 87

Phenylpropanolamine (PPA) is a drug that has been associated with serious side effects including stroke. It is often combined with caffeine in diet preparations and "look-alike" pills. In order to determine if PPA/caffeine can lead to stroke in normotensive and/or hypertensive rats, we administered the combination in six times the allowed human dose calculated on a per weight basis for the rats two times per day for five days. Subarachnoid and cerebral hemorrhage was noted in 18% of the hypertensive rats. A single PPA/caffeine administration (same dose) lead to acute hypertension in both the normotensive and hypertensive animals. These results suggest that PPA/caffeine can lead to cerebral hemorrhage in previously hypertensive animals when administered in greater than the allowed dosage. An acute elevation in blood pressure may be a contributing factor.
Stroke
PMID:Cerebral hemorrhage associated with phenylpropanolamine in combination with caffeine. 669 15


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