Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0085383 (hypocapnia)
 1,697 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The aim of this paper has been to review and discuss the past and the recent investigations concerned with the study of cerebral transport phenomena in pathological conditions which have been divided into two main parts: (1) the effects of experimentally induced blood brain barrier (BBB) injury by (a) HgCl2 or (b) hyper-osmolar intracarotic perfusate; and (2) the effects of ischemia or of an altered oxygen saturation and pCO2 tension on glucose and/or amino acids and/or protein transport across the BBB, in the syanptosomes and cerebral capillaries. The most important observations were as follows: (1) HgCl2 or hyperosmolar perfusates produced an increased BBB permeability to protein tracers but the brain uptake of glucose analogues was found decreased following the former, and increased (except for lactamide) after the latter treatment. (2) (a) In ischemia, the noted increased vesicular transport of peroxidase, as well as the increased saturable and non-saturable passage of glucose analogues across the BBB depended on the duration of cerebral deprivation of blood supply which never resulted in degeneration of endothelial cells of the brain vessels. (b) The progressively decreased specific 2-deoxy-D-glucose uptake in the synaptosomes seen during cerebral ischemia of 30-180 minutes returned to the level of controls 1 hour after reestablishment of cerebral circulation. (c) A decrease in brain uptake of glucose analogues and amino acids (with few exceptions) was observed in severe hypoxia and hypercapnia while an increase or no change in the brain uptakes was seen in hypocapnia. (d) Preliminary investigations of the 2-DG uptake by the cerebral capillaries obtained by fractionation of the brain from animals subjected to normal or altered oxygen saturation and pCO2 tension suggested that cerebral glucose uptake may be directly related to its capillary function.
 ...
PMID:Pathological aspects of brain transport phenomena. 78 95

The effects of droperidol and fentanyl on the intracranial pressure (i.c.p.) and cerebral perfusion pressure (c.p.p.) were studied in eight anaesthetized normocapnic patients with intracranial space-occupying lesions. The infection of droperidol resulted in a small and not significant increase in i.c.p. from 24.0 to 27.2 mm Hg, while c.p.p. decreased from 75.9 mm Hg to 57.8 mm Hg, as a result of a decrease in systemic arterial pressure. The addition of fentanyl produced no change in i.c.p., but a further decrease in arterial pressure decreased c.p.p. from 60.4 mm Hg to 47.8 mm Hg. In four patients values of c.p.p. less than 40 mm Hg were obtained. C.p.p. was was increased by hyperventilation in all but one of these patients. It is concluded that droperidol and fentanyl should be used in patients with intracranial hypertension only if hypocapnia has been established and when the arterial pressure is normal or increased.
 ...
PMID:The effects of droperidol and fentanyl on intracranial pressure and cerebral perfusion pressure in neurosurgical patients. 79 9

Three patients with paralytic poliomyelitis have been ventilated via tracheostomy with uncuffed silver cannula for 21 years, with high tidal volumes of atmospheric air (8.3, 7.2, and 5.4 ml/kg b.wt.), at a frequency of 20, passive expiration, and without periodic hyperinflation. No pulmonary complications were seen during the whole of this period. The total compliance was significantly decreased. The pulmonary physiological shunt relative to the total pulmonary blood flow (Qs/Qt) was slightly increased. PaO2 was nevertheless normal, probably due to a high alveolar PO2 caused by the hyperventilation. The physiological dead space realtive to the tidal volume (VD/VT) was within the noraml range, but VD was high in one case. Two of the patients disclosed an extremely low CO2 production and a PaCO2 averaging 12 mmHg, with small fluctuations during a 24-hour study. This profound respiratory alkalosis was only partly compensated in the arterial blood (pH: 7.54 and 7.50), suggesting a new state of acid-base equilibrium. The cerebrospinal fluid lactate was significantly increased to about 4 mmol/l, but the patients revealed no signs of impaired cerebral function. A reduction of the degree of hypocapnia by the use of a mechanical dead space is recommended.
 ...
PMID:Artificial hyperventilation during 21 years in three cases of complete respiratory paralysis. 81 38

In 7 baboons and 5 macaques the effects of hypercapnia, hypocapnia, hypertension, and combinations of hypertension plus hypocapnia and of hypertension plus hypercapnia on the regional perfusion pressure (rPP) in the brain area rendered ischaemic by occlusion of the middle cerebral artery (MCA) were studied. A new technique for recording the pressure in the occluded MCA was used. The regional tissure pressure (rTP) was recorded with the so called wick type pressure transducers. Hypercapnia produced a marked decrease in rPP in the ischaemic brain area. Hypertension, especially in combination with hypocapnia, produced a very pronounced increase in rPP in the ischaemic brain area. The clinical implications of these findings are discussed. Occlusion of the homolateral common carotid artery (CCA) was followed by a very slight and transient drop in the occluded MCA pressure. Occlusion of the occluded MCA pressure.
 ...
PMID:The influence of changes in arterial CO2 and blood pressure on the collateral circulation and the regional perfusion pressure in monkeys with occlusion of the middle cerebral artery. 81 1

In 7 baboons and 5 macaques the effects of hypercapnia, hypocapnia, hypertension, and combinations of hypertension plus hypocapnia and of hypertension plus hypercapnia on the regional perfusion pressure (rPP) in the brain area rendered ischaemic by occlusion of the middle cerebral artery (MCA) were studied. A new technique for recording the pressure in the occluded MCA was used. The regional tissue pressure (rTP) was recorded with the so called wick type pressure transducers. Hypercapnia produced a marked decrease in rPP in the ischaemic brain area. Hypertension, especially in combination with hypocapnia, produced a very pronounced increase in rPP in the ischaemic brain area. The clinical implications of these findings are discussed. Occlusion of the homolateral common carotid artery (CCA) was followed by a very slight and transient drop in the occluded MCA pressure. Occlusion of the contralateral CCA was followed by a marked and persistent drop in the occluded MCA pressure.
 ...
PMID:The influence of changes in arterial CO2 and blood pressure on the collateral circulation and the regional perfusion pressure in monkeys with occlusion of the middle cerebral artery. 81 73

A group of clinical senile dementia patients underwent a series of cerebrovascular examinations. Some of them were standard examinations (fundus oculi, electroencephalogram, rheoencephalogram, cerebral angiogram and pneumonencephalogram) while the others were studying regional cerebral blood flow (rCBF) and modification of flow under fonctional tests (hypercapnia, hypocapnia and intravenous injection of 50 mg chl. papaverine) using the 133Xe clearance technique. The senile dementia group (III) was compared with 'normal' old patients group (I) and with patients suffering from sequelae of a previous stroke or from minor mental disorders (group II). Elderly subjects regarded as 'normal' often present alterations in usual vascular examinations but reveal a relative integrity of cerebral autoregulation. Some patients considered irreversibly 'sclerotic' still have a good grey matter flow (r1CBF) with real vasomotor possibilities. In each of the three groups of elderly subjects, there seemed to be a lack of correlation between the clinical symptoms and certain specific vascular examination.
 ...
PMID:Cerebral vasoreactivity in senile dementia. 83 Feb 50

The purpose of this investigation was to assess the relative contributions of hyperpnea and hypocapnia in the induction of postexercise asthma. To achieve these ends, eight young asthmatics were exercised on a treadmill while minute ventilations (VE) and end-tidal CO2 (PET CO2) tensions were continuously recorded. The subjects were then restudied using a partial rebreathing technique that allowed separation of minute and alveolar ventilations so that independent evaluations could be made of the relative effects of bulk airflow on pulmonary mechanics as well as a systematic study of hypocapnia in a dose-response fashion. Sustained hyperpnea with VEidentical to those recorded during exercise was totally without effect when the mean PET CO2 was isocapnic or lowered to approximately 30 Torr. Reduction in PETCO2 to 21.3 +/-0.9 Torr brought about significant changes in mechanics, but in every variable measured, exercise produced the greatest alterations and did so at PETCO2 values that had no effect when studied in a controlled fashion. Consequently, neither high VE per se, nor hypocapnia can be considered as the mechanisms underlying exercise induced asthma.
 ...
PMID:Relative contributions of hypocarbia and hyperpnea as mechanisms in postexercise asthma. 83 72

The Valsalva manoeuvre was used to examine circulatory reflexes in 22 patients with acute myocardial infarction. Four patients had the 'square wave' response of cardiac failure and two responded normally to the manoeuvre. In the remaining 18 patients there was a 20 per cent or more fall in pulse pressure during the manoeuvre, but no ensuing rise in diastolic pressure, implying impairment of vasoconstriction. This impairment cannot be explained by acidosis, hypocapnia, or arterial hypoxaemia but may be explained by reflex inhibition of vasoconstriction. This abnormal response has important implications when transporting patients; furthermore, it could explain the rapid deterioration sometimes seen in patients with arrhythmias.
 ...
PMID:Circulatory reflexes in myocardial infarction. 83 30

Increased body temperature stimulates hyperventilation in man but little is known about its effects on ventilatory responsiveness to hypoxia. Hence this study examined the effects of hyperthermia on hypoxic ventilatory response (HVR), hypercapnic ventilatory response (HCVR), and oxygen consumption (VO2). Six fasting subjects had these variables measured under basal conditions and at two levels of hyperthermia. Hypoxic ventilatory response was measured as the shape paramater A of the VE/PAO2 curves. Since hyperthermia produces hyperventilation and, therefore, hypocapnia, HVR was measured at the hyperthermic (hypocapnic alveolar CO2 tension (PACO2) and at the basal (normothermic) PACO2. Hypoxic ventilatory response (A) increased when measured at basal PACO2 levels, from 113 +/- 8.8 (S.E.M.) to 189 +/- 21.8 at 0.7 degrees C. and 240 +/- 34.0 at + 1.40 degrees C. (P less than 0.005). HVR measured during hyperthermic hypocapnia also increased at each temperature level but did not reach statistical significance (P = 0.1). Hypercapnic ventilatory response, as measured by the slope S of VE/PACO2 lines, increased significantly at each temperature elevation (P less than 0.025). We conclude that raising body temperature causes a significant augmentation of ventilatory responses to hypoxia (during normothermic PACO2 conditions) and to hypercapnia.
 ...
PMID:Effects of hyperthermia on hypoxic ventilatory response in normal man. 83 15

Previous workers have reported that ethyl methylene blue (EMB) diminishes cyanide-induced increases in blood lactate (CIL); the present study investigates the mechanism underlying this interaction. Accordingly, sodium cyanide (1.2 mg./Kg.) was infused into the abdominal aorta of anesthetized, spontaneously breathing dogs. Following cyanide infusion, arterial lactate concentration increased 5.4 +/- 1.1 mmol./L. and arterial PCO2 decreased 22 +/- 3 mm. Hg. A second group of dogs was pretreated with EMB (8 to 15 mg./Kg.); this dose of EMB elicited twofold increments in oxygen consumption and induced the formation in vivo of methemoglobin (0.8 +/- 0.1 gm./100 ml.). Following cyanide infusion, the increase in lactate in EMB animals was only 0.6 +/- 0.2 mmol./L.; the decrease in arterial PCO2 was limited to 5 +/- 1 mm. Hg. In order to clarify the relationship between cyanide-induced hypocapnia and CIL, cyanide was infused into a third group of dogs that were maintained isocapneic via mechanical ventilation; despite constancy of arterial PCO2, lactate increased 6.0 +/- 0.7 mmol./L. To determine the effect of EMB-induced tissue hypermetabolism on CIL, twofold increments in oxygen consumption were produced in a fourth group of dogs by pretreatment with sodium salicylate. Following cyanide infusion, salicylate-pretreated animals increased lactate 7.2 +/- 1.2 mmol./L. In order to assess the relationship between EMB-induced methemoglobinemia and the decrease in CIL, similar concentrations of methemoglobin were produced in two subsequent groups of dogs by two different techniques (i.e., by aniline pretreatment or by infusion of methemoglobinemic blood that had been prepared in vitro by addition of sodium nitrite). CIL in these animals was again markedly diminished (i.e., increments of only 0.6 +/- 0.3 mmol./L.) It is concluded that EMB diminishes CIL by a mechanism other than elimination of cyanide-induced hypocapnia or induction of tissue hypermetabolism. The results suggest that methemoglobin formation may completely account for the ability of EMB to effect a decrement in CIL.
 ...
PMID:Interaction between ethyl methylene blue and cyanide-induced increases in blood lactate. 83 20


<< Previous 1 2 3 4 5 6 7 8 9 10