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

Elevated pulmonary vascular resistance (PVR), differential cardiac dynamics, and increased lung water following cardiopulmonary bypass (CPB) have been proposed as limitations to the accuracy of the pulmonary artery occlusion pressure (PAOP) in estimating left ventricular preload. A prospective study of 22 patients undergoing elective myocardial revascularization is described wherein PAOP was compared with directly measured left atrial pressure (LAP). The reliability of PAOP to estimate LAP in the hour immediately following CPB and at 1, 4, 8, and 12 hours post-CPB was examined with repeated measures analysis of variance. Relationships between the PAOP-LAP difference and PVR, core temperature, arterial CO2 tension, and right and left ventricular stroke work indices (RVSWI, LVSWI) were tested by linear regression analysis. There was greater variability in measurements at 15, 30, and 45 minutes immediately after CPB, demonstrated by a pooled correlation coefficient of 0.73 versus 0.90 in the postoperative period. The degree of discrepancy between PAOP and LAP lessened with time. There was no determinable relationship of the PAOP-LAP gradient to PVR, level of PCO2, temperature, RVSWI, or LVSWI. Potential sources of discrepancy include airway pressure effects, position of the measuring catheters, positive end-expiratory pressure, infusion of protamine sulfate, extremes of pulmonary artery pressures, and effects of an open pericardium.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Pulmonary artery occlusion pressure is not accurate immediately after cardiopulmonary bypass. 213 34

Acetazolamide (ACZ), a potent carbonic anhydrase inhibitor, is known to decrease submaximal exercise tolerance under normoxic and hypoxic conditions. These decrements in performance occur despite the maintenance of O2 consumption and CO2 removal. Because ACZ is a diuretic, it induces a moderate hypohydration that may have a role in reducing the ability to sustain exercise through cardiovascular and thermoregulatory impairment. To investigate this potential impairment, seven healthy males between 21 and 35 yr of age were studied in a double-blind crossover design (placebo vs. ACZ). ACZ was administered in three 250-mg oral doses 14, 8, and 2 h before exercise. Subjects exercised at 70% peak O2 uptake for 30 min on a cycle ergometer in a normoxic thermoneutral environment (25 degrees C, 40% relative humidity). Results indicate that exercise minute ventilation was greater but O2 uptake, CO2 output, and respiratory exchange ratio did not differ with ACZ. ACZ led to lower mean skin (0.7 degrees C), higher rectal (0.6 degrees C), and higher mean body temperatures (0.4 degrees C) after 30 min of exercise. Whole-body sweat loss was reduced 23%, and heat storage during the exercise bout was increased 55%. Stroke volume decreased 25%, and arteriovenous O2 difference increased 15%. A significant inverse relationship (r = -0.63) between heart rate and stroke volume was observed. It is concluded that previously reported decreases in the ability to sustain submaximal exercise with ACZ may be related to hypohydration-induced impairment of the cardiovascular and thermoregulatory systems.
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PMID:Acetazolamide alters temperature regulation during submaximal exercise. 226 61

Gas mixing was studied in 10 anesthetized paralyzed dogs during high-frequency low tidal ventilation (HFV). After simultaneous washin of ethane (1%) and washout of resident argon (0.9%) the gas inflow was switched to atmospheric air for varied time intervals leading to varied levels of C2H6 washout and Ar washin. After the stop of HFV at predetermined test gas washout/washin levels, a constant-flow exhalation by a servo ventilator was performed and expirograms of C2H6 and Ar were recorded. Measurements were performed at varied ventilation frequencies (10-40 Hz), stroke volumes (20-40 ml), lung volumes (730-830 ml), expiratory flow rates (0.1-0.01 L/sec), breath-holding prior to exhalation (0-12 sec) and test gas washout levels achieved by varying the washout time (1 to 65 sec) before onset of exhalation. The expirograms showed a close to linearly rising alveolar plateau. They were analyzed for series dead space and alveolar slope which was normalized to the initial-to-final partial pressure difference. The normalized slopes of C2H6 washout and Ar washin were averaged, whereby the effect of shrinking lung volume due to continuing CO2/O2 exchange at low R was assumed to be suppressed. The slope was little affected by changes of stroke volume, decreased slightly with increasing frequency, and decreased considerably with breath-holding or increasing lung volume. As washout progressed, the alveolar slope first increased, attained a maximum at about half-washout and thereafter decreased. The finite values of the alveolar slope indicated that intrapulmonary gas mixing during HFV was incomplete. The slopes were larger than expected from diffusion calculations on symmetrically branching lung models. The behavior of the slope at varied washout levels suggested involvement of parallel ventilation/volume inhomogeneity coupled with sequential emptying.
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PMID:Gas mixing in dog lungs during high frequency ventilation studied by partial washout-single exhalation technique. 227 Mar 57

The interval preceding the growth of irreversible lesions in an abdominal apoplexy is variable (3-48 hours). It may be used to improve the ischaemic viscus oxygenation, also compensating possible metabolic imbalances. 16 rabbits were used for research, in which apoplexy by the ligature of the arteria mesenterica superior was induced. Dialysis-oxygenation peritoneal treatment was carried out for 8 rabbits, the results of which were evaluated on the basis of the intestine macroscopic morphologic aspect; on the basis of the hematic phosphates values and in enteral biopsy. The oxygenation-dialysis produced a rapid improvement in enteral hue and in enteral motility, an important increase of PO2 and a reduction of hematic phosphates compared with the control group. Histologic examination did not show any significant variation. The attempt to increase general oxygenation by supplying PO2 via the peritoneum, was partly successful (10-15%). The aim of oxygenation the ischaemic enteral zone was successful. This due to elimination of CO2 and toxic products using dialysis. This simple method seems to be effective but further tests on swine would be necessary for clinical applications.
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PMID:[Peritoneal oxygenation-dialysis as a temporary treatment of intestinal infarction]. 227 Aug 89

Factors contributing to maximal incremental and short-term exercise capacity were measured before and after 12 wk of high-intensity endurance training in 12 old (60-70 yr) and 10 young (20-30 yr) sedentary healthy males. Peak O2 uptake in incremental cycle ergometer exercise increased from 1.60 +/- 0.073 to 2.21 +/- 0.073 (SE) l/min (38% increase) in the old subjects and from 2.54 +/- 0.141 to 3.26 +/- 0.181 l/min (29%) in the young subjects. Peak cardiac output, estimated by extrapolation from a series of submaximal measurements by the CO2 rebreathing method, increased by 30% (from 12.7 to 16.5 l/min) in the old subjects, associated with a 6% increase (from 126 to 135 ml/l) in arteriovenous O2 difference; in the young subjects there were equal 14% increases in both variables (18.0 to 20.5 l/min and 140 to 159 ml/l, respectively). Submaximal mean arterial pressure and cardiac output were lower posttraining in the old subjects; total vascular conductance and cardiac stroke volume increased. Although peak power at the start of a short-term maximal isokinetic test did not change, total work accomplished in 30 s at a pedaling frequency of 110 revolutions/min increased in both groups, from 11.2 to 12.6 kJ and from 15.7 to 16.9 kJ in the old and young, respectively; fatigue during the 30-s test was less, and postexercise plasma lactate concentrations were lower. In older subjects, increases in aerobic power after high-intensity endurance training are at least as large as in younger subjects and are associated with increases in vascular conductance, maximal cardiac output, and stroke volume.
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PMID:High-intensity endurance training in 20- to 30- and 60- to 70-yr-old healthy men. 227 73

During the last decade several studies of cerebral blood flow (CBF) and metabolism in the acute phase of head injury have been published. It is the aim of this review to describe the dynamic changes in CBF, cerebral metabolic rate of oxygen (CMRO2), cerebral autoregulation (CA), and reactivity to PaCO2 and barbiturate (metabolic reactivity) in the acute phase after severe head injury and to discuss the therapeutical consequences with reference to prolonged artificial hyperventilation, hypothermia, barbiturate sedation, and mannitol therapy. On the basis of present knowledge concerning cerebral circulation and its regulation, the author reviews the literature concerning methodology for experimental and clinical CBF measurements and regulation of CBF and cerebral oxygen uptake. Emphasis is placed on studies of the effect of body temperature (hypothermia) as a therapeutic tool in the control of cerebral metabolism, blood flow, and intracranial pressure. Although hypothermia significantly reduces cerebral metabolism and blood flow, the effect of hypothermia on cerebral blood flow, metabolism, ICP, and outcome after acute head injury has never been investigated in clinically controlled studies. Experimental and clinical studies concerning sensitivity of CBF for changes in PaCO2 are reviewed. The normal CO2 reactivity defined as absolute (delta CBF/delta PaCO2) and relative (% change CBF/delta PaCO2) or delta in CBF/PaCO2 mm Hg are mentioned. In awake normocapnic man the relative CO2 reactivity averages 4%/mm Hg and the absolute CO2 reactivity 2ml/mm Hg. Uncontrolled prospective studies show a therapeutic effect of artificially prolonged hyperventilation on outcome. Only one preliminary controlled study indicates that the outcome is poorer and recovery prolonged. Nevertheless, in the acute phase of HI, artificial hyperventilation is used routinely for control of intracranial hypertension and during the intensive care management of the patients. The steal and inverse steal phenomena are reviewed. Although of considerable theoretical interest these phenomena are without clinical significance in patients with head injury, unless clinical CBF measurements are performed. The frequency of the inverse steal phenomenon in studies of rCBF with a 16-channel Cerebrograph (intraarterial approach) is found to be about 10%. During prolonged hyperventilation experimental studies and clinical studies of apoplexy show an adaptation of CBF and CSF-pH and bicarbonate.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Cerebral blood flow in acute head injury. The regulation of cerebral blood flow and metabolism during the acute phase of head injury, and its significance for therapy. 227 29

We employed fluorocarbon-23 (trifluoromethane) as a nuclear magnetic resonance gaseous indicator of cerebral blood flow in seven cats. Pulsed inhalation of this indicator and switching between two coils allowed the acquisition of both an arterial input and a cerebral response function, making possible multicompartmental curve fits to cerebral uptake and clearance data. The brain:blood partition coefficient for trifluoromethane was 0.9 for both gray and white matter. Fast-compartment blood flows were normal and showed appropriate CO2 reactivity. Slow-compartment blood flows did not demonstrate CO2 reactivity, probably because cranial as well as white-matter blood flows were lumped together in the slow compartment. Although cerebral blood flow was stable during administration of 60% trifluoromethane, the compound did prove to be a mild cardiac sensitizer to epinephrine in five cats.
Stroke 1990 Jan
PMID:Fluorocarbon-23 measure of cat cerebral blood flow by nuclear magnetic resonance. 230 Sep 75

Regional cerebral blood flow studies with xenon-133 are useful in the functional assessment of cerebrovascular diseases. Conventional models for cerebral blood flow calculation employ 11 minutes of data collection. However, in many circumstances it is not possible to maintain steady-state physiologic conditions for 11 minutes. We compared a monocompartmental model that requires only 3 minutes of data collection with the bicompartmental model that requires 11 minutes of data collection. The correlation between the absolute values for global cerebral blood flow (initial slope index, intravenous method) in 72 anesthetized patients was r = 0.88; for 54 awake patients inhaling xenon-133, the correlation was r = 0.77. Cerebral blood flow was determined with intravenous xenon-133 at baseline and during a CO2 challenge in 50 patients during cerebrovascular surgery under general anesthesia. Reactivity to a 10-mm Hg rise in PaCO2 was calculated in absolute terms and as a percentage change from baseline using both the 3-minute and the 11-minute models. The correlation of CO2 reactivity calculated with the two models was r = 0.9 for the absolute values and r = 0.8 for the relative change. Cerebral blood flow calculated with the two models correlated well in both awake and anesthetized patients. In addition, there was a good correlation between CO2 reactivity calculated with the two models. In situations in which physiologic conditions cannot be held stable for 11 minutes, the 3-minute initial slope index may be used to quantitatively assess cerebrovascular reserve with a CO2 challenge.
Stroke 1990 Feb
PMID:Three-minute blood flow index for assessment of cerebrovascular reserve. 230 4

Maximal VO2 on the treadmill (VO2max) and on the bicycle ergometer (VO2peak), maximal cardiac output (Qmax), by a CO2 rebreathing method, maximal heart rate (HRmax), blood hemoglobin concentration (Hb), and hematocrit (Hct) were measured on six subjects before (B) and 3 weeks after (A) prolonged exposure to chronic hypoxia. It was observed that after high-altitude exposure VO2max, VO2peak, and Qmax were lower (P less than 005) than before [A: 4.13 +/- 0.67; 3.28 +/- 0.41 and 16.89 +/- 2.49 (l/min +/- SD); B: 4.39 +/- 0.39; 3.53 +/- 0.34 and 21.81 +/- 1.27, respectively], whereas Hb and Hct were larger (A: 162 +/- 8 g/l and 0.46 +/- 0.02; B: 142 +/- 7 and 0.41 +/- 0.02) and HRmax was unchanged (178 +/- 7 vs 175 +/- 9 bts/min). Thus, the calculated stroke volume of the heart and the Hb flow at VO2 peak were lower in A than in B (95 +/- 15 vs 124 +/- 7 ml and 2,723 +/- 307 vs 3,129 +/- 196 g/min) (P less than 0.05, respectively), whereas the arteriovenous O2 difference was greater in A than in B (195 +/- 16 vs 162 +/- 19 ml O2/l; P less than 0.05). At any given submaximal work load, VO2 and HR were the same in B and in A, whereas Q was lower in A by approximately 2-3 l/min. However, because of the increased Hb, leading to a higher arterial O2 content, at any work load the O2 flow remained unchanged.
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PMID:Oxygen transport system before and after exposure to chronic hypoxia. 232 58

Phosphate has been proposed as an ergogenic aid since it may enhance O2 delivery and cardiac work efficiency by increasing plasma phosphate (P Pi), red blood cell phosphate (RBC Pi), 2,3-diphosphoglycerate (DPG), RBC adenosine triphosphate (ATP), and P50. In 10 normal, fasting males we measured cardiac output (Q) by CO2 rebreathing, heart rate (HR), O2 deficit (O2DEF), and O2 consumption (VO2) during cycle ergometer exercise (60% of peak VO2). Stroke volume (SV) and arteriovenous O2 difference (A-VO2) were calculated. Following a baseline blood sample (BASE) for P Pi, RBC Pi, DPG, RBC ATP, and P50 (3 h before exercise), a single oral dose of dicalcium phosphate (129 mmol) and glucose (500 ml/10% sol, PHOS), or placebo (PLA), was administered in a random, crossover, double-blind fashion. Blood sampling was repeated immediately before and after exercise (PRE-EX and POST-EX). PHOS induced increases in P Pi (3.87 to 4.35 mg.dl-1, P less than 0.05), RBC Pi (3.86 to 4.63 mg.dl-1, P = 0.08), DPG (11.8 to 13.1 mumol.g-1 Hb, P less than 0.05), RBC ATP (4.2 to 4.4 mumol.g-1 Hb, P less than 0.05), and P50 (26.8 to 27.9 mm Hg, P less than 0.05) from BASE to PRE-EX. All variables remained elevated through the exercise period, as evidenced by higher levels than BASE at POST-EX (P less than 0.05). However, P50 was not different across conditions at PRE-EX (PHOS P50 = 27.9, PLA P50 = 28.3 mm Hg) or POST-EX (PHOS P50 = 28.0, PLA P50 = 28.1 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Oxygen delivery and cardiac output during exercise following oral phosphate-glucose. 238 2


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