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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Multiple serum chemical values were examined in 92 patients with chronic glaucoma who were treated with the carbonic anhydrase inhibitors (CAIs) acetazolamide or methazolamide, seeking relationships between serum composition and symptomatic side effects. Of the 92 patients, 44 complained of a symptom-complex of malaise, fatigue, weight loss, depression, anorexia, and loss of libido, which we have found most commonly to threaten continuation of therapy. Patients who had this symptom complex were significantly more acidotic than those without it. Ten of 24 patients who had chemical evidence of excessive acidosis reported a dramatic alleviation of symptoms when sodium bicarbonate was administered, although their serum CO2-combining power changed little. There was no correlation of the symptom complex with serum potassium concentration, except in a few patients who were simultaneously receiving chlorothiazide diuretics for systemic hypertension and who became frankly hypokalemic.
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PMID:Carbonic anhydrase inhibitor side effects. Serum chemical analysis. 88 13

Regional cerebral blood flow (rCBF) was repeatedly measured by the hydrogen clearance method in the frontal cortex of stroke-prone spontaneously hypertensive rats (SHRSP) at the age of 50 days and thereafter. When SHRSP rats developed severe hypertension (over 200 mg Hg at the age of 60 days) rCBF began to decrease abruptly in the frontal cortex--one of the three predilection sites of stroke in these rats. In contrast, such a reduction in rCBF was not noted in either stroke-resistant spontaneously hypertensive rats (SHRSR) which developed moderate hypertension (under 200 mg Hg), or in Wistar-Kyoto rats (WK) with normal blood pressure (under 15 mm Hg). A similar marked reduction of rCBF with severe hypertension (over 200 mm Hg) was also detected in apoplectic gene-free renal infarction hypertensive rats (RHR) experimentally produced from age-matched WK animals. Blood samples were obtained through an implanted femoral artery canula without disturbing the nonanesthetized SHRSP, SHRSR and WK rats. Arterial blood gas analysis (PaCO2, PaO2 and pH) showed no significant differences at the age of 5 months in any of these rats. Chemical cerbrovascular reactivity, that is, an increase in rCBF in response to CO2 inhalation, showed no significant difference among SHRSP rats from the age of 50 days to 5 months. However, it markedly decreased in SHRSP rats at the age of 9 months and thereafter (the average age of male SHRSP rats which develop stroke is 9 months). The present study showed stroke did not occur in antihypertensive agent-treated SHRSP rats. In these SHRSP rats rCBF did not decrease as long as blood pressure was well-controlled.
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PMID:Developmental course of hypertension and regional cerebral blood flow in stroke-prone spontaneously hypertensive rats. 89 41

Circumstances under which the use of oxygen-therapy in lung disease can be effective and harmless, depend upon a careful evaluation of its indications: they are suggested by the clinical need of correction of hypoxaemia as well as by the awareness of factors determining respiratory failure and of problems concerning O(2) transport and supply to tissues in health and disease. Blood gases monitoring enables to control the effects of treatment on arterial O2 and CO2 tensions thus giving all the useful data for oxygen administering particularly as far as components of hyperoxygenated mixtures, flow rate, duration, use of very effective low-risk devices (Venturi masks) are concerned. Correction of hypoxaemia involves the reduction of hypertension of the pulmonary circulation and hyperglobulia, improvement of tolerance of exertion, and attention to the metabolic compensation of respiratory acidosis. These results are influenced by the nature of the pathogenetic factors behind broncho-obstructive disease, which may lead to either a primarily "bronchitis" or a primarily "emphysematous" syndrome. An interesting feature relates to prognosis in the case of patients making home use of hyperoxygenated mixtures as part of a rehabilitation program, or to improve their quality of life. The cost and benifits of such treatment should be carefully weighed. Lastly, in the event of protracted treatment, attention must be paid to the possibility of toxicity and the means to be adopted for its prevention.
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PMID:[Oxygen therapy in pneumology]. 101 8

The effects of hyperbaric oxygenation with 2 atm. pressure and 100 percent oxygen on cerebrovascular tone were assessed by the reactivity of the cerebral vessels to CO2 and vasomotor capacitance index (the cranial pressure divided by the mean arterial pressure) in 50 anaesthetized artifically ventilated dogs, in which intracranial pressure was raised by slow inflation of an extradural balloon. Hyperbaric oxygenation reduced the intracranial pressure only at the stage when the cerebral vessels were still responsive to CO2, as indicated by a rise in intracranial pressure of 30-70 mmHg; under these circumstances, both the reactivity of CO2 and the vasoconstrictor tone of cerebral vessels were improved by hyperbaric oxygenation. At this stage, rapid decrease of the intracranial pressure produced by deflation of the extradual balloon showed no rebound, and hyperbaric oxygenation rapidly restored the vasomotor tone. When CO2 failed to influence the intracranial pressure of about 100 mmHg hyperbaric oxygenation did not aid the recovery of the reactivity of the cerebral vessels to CO2 or the vasoconstrictor tone. In extreme intracranial hypertension (above 100 mmHg) when there was reactivity to CO2 and the electroencephalogram was flat, rapid balloon deflation was followed by a further gradual increase of intracranial pressure and hyperbaric oxygenation did not restore the cerebrovascular tone. The effect of hyperbaric oxygenation in experimental intracranial hypertension appeared to be dependent upon the vasoconstrictor tone of the cerebral vessels, which would be indicated by a vasodilator response to CO2.
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PMID:Effects of hyperbaric oxygenation on cerebral vasomotor tone in acute intracranial hypertension: an experimental study. 118 93

The left main pulmonary artery was ligated in 7 fully grown dogs. This resulted in an enlarged pulmonary collateral (systemic) flow to the left lung. By collecting gas from each lung separately, gas exchange in the pulmonary collateral circulation was studied and compared to that in the normal contralateral side. Studies were done repeatedly during a period of 3 years. Compared to that in the preoperative period, the ligated (left) side showed a decrease in ventilation (42.5 to 34.5 per cent of total), a marked increase in wasted ventilation (0.30 to 0.55), and a marked decrease in O2 uptake (45 to 11.2 per cent of total) and CO2 production (27.5 to 15.3 per cent of the total). There were no changes in arterial blood gases or pH. A significant, sustained, systemic hypertension was noted in all dogs in which the left main pulmonary artery was ligated (190/120). The mean blood flow through the pulmonary collateral circulation of the left lung with the dogs breathing room air was estimated to be 94 ml per min. When the dogs were made hypoxemic by breathing 12 per cent O2 through the normal right lung, there was a marked increase in pulmonary collateral (systemic) flow to the contralateral side (194 ml per min). This resulted in an increase in O2 consumption (29.4 per cent of total) and CO2 production (23.1 per cent of total) of the left lung. When the dogs were given 12 per cent O2 to breathe through the ligated left lung, there was no change in arterial PO2. There was a significant increase in blood flow through the pulmonary collateral circulation to 136 ml per min. Because of the gradient of O2 between the blood flowing into the left lung and that present in the alveoli, there was a net production of O2 from the left lung of 4.5 ml per min. When the pulmonary systemic circulation participates in gas exchange, it appears to increase during hypoxemia as well as during alveolar hypoxia.
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PMID:Gas exchange in the pulmonary collateral circulation of dogs. Effects of alveolar hypoxia and systemic hypoxemia. 119 Jun 16

Elevated blood pressure in psychophysiological studies of borderline hypertension is frequently attributed to the effects of increased sympathetic tone, and with few exceptions, the potential parasympathetic contributions have not been considered. Furthermore, of the investigations that have addressed vagal influences upon blood pressure, most have employed invasive pharmacological assessment of parasympathetic tone. In this study, cardiac parasympathetic and beta-adrenergic influences in borderline hypertension were evaluated noninvasively employing respiratory sinus arrhythmia as a vagal index and preejection period as a sympathetic index of cardiac functioning. Subjects were 30 borderline hypertensive and 23 normotensive males (age range, 24-45 years). The ECG, blood pressure, impedance cardiography, and respiration were measured during two baselines (initial and post-task), a memory-comparison reaction time task, the cold pressor, and CO2-rebreathing. Results indicated tonic differences between groups in all cardiovascular variables across tasks, with the exception of pre-ejection period, which showed no group effects at all. Hypertensives additionally manifested somewhat heightened systolic blood pressure reactivity and attenuated cardiac parasympathetic responsivity to specific tasks. Our findings provide no support for an exaggerated cardiac beta-adrenergic tonic level or reactivity in borderline hypertensives. On the other hand, the consistently lower magnitude of respiratory sinus arrhythmia in our hypertensives suggests that reduced parasympathetic control may be involved in the pathophysiology of hypertension.
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PMID:Cardiac autonomic mechanisms associated with borderline hypertension under varying behavioral demands: evidence for attenuated parasympathetic tone but not for enhanced beta-adrenergic activity. 133 72

The alpha 2-adrenergic receptor agonist dexmedetomidine produces an anesthetic state in a variety of species. Although its effects on cerebral blood flow and the electroencephalogram have been investigated, the effect of this drug on intracranial pressure (ICP) has not been reported previously. Dexmedetomidine therefore was intravenously administered to 24 New Zealand white rabbits that had been anesthetized with halothane and mechanically ventilated to maintain a constant arterial CO2 tension (PaCO2) between 34 and 39 mm Hg. After placement of an arterial catheter and ventricular cannula, baseline measurements of monitored variables, including heart rate, mean arterial blood pressure, ICP, end-tidal CO2, body temperature, and arterial blood gases, were recorded. Dexmedetomidine (20, 80, or 320 micrograms/kg IV) or saline solution was then infused over a 10-min period. The ICP transiently decreased by 31% in the 20-micrograms/kg group (from a mean value of 9.4 +/- 1.3 [SEM] to 6.5 +/- 1.0 mm Hg, P less than 0.05). In the 320-micrograms/kg group, ICP remained unchanged over the course of the study despite a significant increase in arterial blood pressure (32 mm Hg). The effects of dexmedetomidine on ICP were next investigated in the presence of intracranial hypertension produced by a cryogenic lesion (mean baseline ICP 16.8 mm Hg). In addition to the previously monitored variables, sagittal sinus blood flow was measured by the hydrogen clearance technique before and after the administration of dexmedetomidine (320 micrograms/kg IV). In these experiments, dexmedetomidine was associated with a 14% decrease in sagittal sinus blood flow that was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Intracranial pressure effects of dexmedetomidine in rabbits. 135 50

Benzodiazepines for sedation may decrease the PaO2, the arterial O2 saturation (SaO2), and the CO2 response more in the elderly than in the young. The purpose of this study was to assess changes in blood gases due to i.v. midazolam or sublingual flunitrazepam given as premedication in elderly patients for unilateral cataract surgery. METHODS. Fifty patients over 65 years of age with treated arterial hypertension and other co-existing diseases (ASA III-IV) were randomly assigned to have: (1) i.v. midazolam titrated until they became drowsy (17 patients; 2.85 +/- 0.84 mg [mean +/- SD]); (2) sublingual flunitrazepam (16 patients; 0.005 mg/kg); or (3) no sedation (17 patients; controls). On entering the operating theatre, the radial artery was cannulated and the first blood gas analysis was obtained. The premedication was then given. At 5, 10, 20, and 30 min after premedication, before and 10 min after retrobulbar block, before operation, 5 and 15 min after the beginning of the operation, 10 and 20 min after administration of 500 mg acetazolamide i.v. during the operation, and 10 and 20 min after the operation additional arterial blood samples were analysed (a total of 15 measuring points). Pulse oximetry, invasive blood pressure, and ECG were continuously monitored. All patients received oxygen 3 l/min during the operation by nasal cannula. Differences between the three groups were analysed by Student's t-test or U-test and a P value < 0.05 was considered significant. RESULTS. The patient demography, including duration of anaesthesia and operation, was similar in the three groups (Table 1). No significant differences were seen in heart rate, mean arterial pressure, PaO2, pulse-oximetric oxygen saturation (SpO2), base excess, or serum bicarbonate levels. The PaCO2 increased in patients after midazolam (P < 0.01) and flunitrazepam (P < 0.05) until the beginning of the operation compared with the control group (Fig. 3); 20 min after the operation there was still a significant difference between the midazolam group and the controls. SaO2 was significantly (P < 0.05) lower in the midazolam group 10 and 20 min after administration of premedication compared with the control group, but was within physiological limits (Fig. 5). Despite titration, 2 patients had severe respiratory insufficiency 3 min after midazolam: the SpO2 decreased below 85% and the paO2 below 55 mmHg. The paCO2 was higher (P < 0.05) in the midazolam group 10 min after acetazolamide compared with the controls. CONCLUSIONS. The results of the study show the potential hazards of i.v. midazolam in the elderly. If sedation is required for cataract surgery under local anaesthesia, we recommend sublingual flunitrazepam or the use of benzodiazepines with lower hypnogenic effects in the elderly. A thorough preoperative discussion of anaesthesia and the operation might be an adequate substitute for any premedication in high-risk patients; the best blood gas analysis results were obtained in the control group.
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PMID:[Premedication in retrobulbar anesthesia. A blood gas analysis comparison of sublingual flunitrazepam and intravenous midazolam]. 146 54

The continuous measurement of jugular venous oxygen saturation (SjvO2) with a fiberoptic catheter is evaluated as a method of detecting cerebral ischemia after head injury. Forty-five patients admitted to the hospital in coma after severe head injury had continuous and simultaneous monitoring of SjvO2, intracranial pressure, arterial oxygen saturation, and end-tidal CO2. Cerebral blood flow, cerebral metabolic rates of oxygen and lactate, arterial and jugular venous blood gas levels, and hemoglobin concentration were measured every 8 hours for 1 to 11 days. Whenever SjvO2 dropped to less than 50%, a standardized protocol was followed to confirm the validity of the desaturation and to establish its cause. Correlation of SjvO2 values obtained by catheter and with direct measurement of O2 saturation by a co-oximeter on venous blood withdrawn through the catheter was excellent after in vivo calibration when there was adequate light intensity at the catheter tip (176 measurements: r = 0.87, p less than 0.01). A total of 60 episodes of jugular venous oxygen desaturation occurred in 45 patients. In 20 patients the desaturation value was confirmed by the co-oximeter. There were 33 episodes of desaturation in these 20 patients, due to the following causes: intracranial hypertension in 12 episodes, hypocarbia in 10, arterial hypoxia in six, combinations of the above in three, systemic hypotension in one, and cerebral vasospasm in one. The incidence of jugular venous oxygen desaturations found in this study suggests that continuous monitoring of SjvO2 may be of clinical value in patients with head injury.
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PMID:Continuous monitoring of jugular venous oxygen saturation in head-injured patients. 160 65

To test the hypothesis that renal sensitivity to atrial natriuretic peptide (ANP) is impaired in Gordon's syndrome (hypertension and hyperkalaemia with normal glomerular filtration rate) we infused alpha-hANP into two patients with this syndrome (a sister and a brother, 19 and 18 years of age). For comparison, 11 healthy volunteers were also examined. The infusion of alpha-hANP increased urinary volume and excretion of sodium similarly in the patients and controls. The excretion of potassium did not change in either the patients or the controls. The infusion of alpha-hANP had no effect on the serum potassium levels or the plasma CO2 content in the patients. The present results do not confirm the hypothesis of lack of sensitivity to ANP as a pathophysiological concept in Gordon's syndrome.
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PMID:Normal renal sensitivity to atrial natriuretic peptide in Gordon's syndrome. 153 8


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