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Query: UMLS:C0085383 (hypocapnia)
 1,697 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study examines the possibility that changes of cerebral extracellular pH (PH e) or adenosine concentration may provide coupling mechanisms of a general nautre, adjusting cerebral blood flow (CBF) to metabolic demands. Although there is considerable indirect evidence that CBF varies inversely with pHe, results obtained during the last few years indicate that large increases in flow may occur in the absence of a fall in pHe. Thus, induction of hypoxia or epileptic seizures leads to maximal increase in CBF before pHe falls or even when there is initial alkalosis due to concomitant hypocapnia. Furthermore, CBF increases in hypoglycaemia and after administration of amphetamine, two conditions unassociated with tissue acidosis. The possibility that adenosine may be a coupling factor was examined in hypoxia and during epileptic seizures in rats. In both conditions a four- to fivefold increase in CBF occurs in spite of the fact that tissue adenosine concentrations remain at or below 1 mumolkg-u. It is concluded that adenosine accumulates first when there is a perturbation of cerebral energy state with a rise in AMP concentration. It seems unlikely that adenosine, formed by breakdown of AMP, acts as a general coupling factor.
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PMID:Coupling of cerebral metabolism and blood flow in epileptic seizures, hypoxia and hypoglycaemia. 2 37

EEG, end-tidal CO2, neck muscle EMG, eye movements, and ECG were recorded in 17 children undergoing enflurane anesthesia combined with N2O and O2. All subjects were classified in the lowest risk group and had normal pre-anesthetic EEG recordings. Eleven subjects were breathing spontaneously and six were under controlled ventilation. Thirteen subjects were hyperventilated for short periods. As previously reported for adults, various signs of increased central nervous excitability appeared. At the enflurane concentration of 4% all three cases with PaCO2 below 32 mmHg showed generalized high voltage epileptic activity of grand mal type followed by several minutes of postictal slowing. One of these subjects also showed motor manifestations of the electrographic seizure activity. At 3% enflurane, three out of eight subjects showed electrographic seizure activity of poly-spike-suppression type. One of these children also had motor manifestations during this type of seizure activity at a PaCO2 of 31 mmHg. The results indicate that electrographic seizure activity is common among children with moderate hypocapnia at enflurane concentrations of 3% or more.
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PMID:Electroencephalographic activity in children under enflurane anesthesia. 121 Oct 75

Epileptogenic complications after supratentorial intracranial surgery are, strictly defined, the events which promote a further complication, i.e. seizures in any form, partial, simple or complex, or generalized. The most common epileptogenic complications are, therefore, electrolyte imbalance, hypoxia, hypoglycemia, hypocapnia, and intracerebral or extradural hematoma. However, also inadequate anticonvulsant prophylaxis and use of convulsant drugs can yield to the onset of post-operative seizures. Anesthetic drugs have been each time defined pro or anti-convulsant: however, data from the literature show that it is not possible to certainly define the role of general anesthetics in the genesis of post-operative seizures.
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PMID:[Epileptogenic complications of neurosurgical interventions]. 162 Apr 64

Propofol was used for 1,350 sessions of electro-convulsive therapy (ECT). After 0.5 mg of intravenous atropine, patients received 1 to 1.5 mg.kg-1 bolus of propofol over a period of 20 seconds or less. This was convenient for loss of the eye-lash reflex. A bolus of 15 to 20 mg suxamethonium was given, in non allergic patients, to prevent trauma from the seizure. The patient was hyperventilated with pure oxygen through a facial mask. The electric shock was delivered bitemporally after a dental protection had been inserted. For each patient, the following data were noted: sex, use of tricyclic antidepressant drugs, atopy, amount of administered propofol and the effective intensity of the electric shock. The 99 patients were given 16.27 +/- 14 ECT sessions. Among them 26 took antidepressant drugs and 34 were atopic. There was no difference, except for weight, between the 25 men and 74 women. The mean dose of propofol was 1.37 +/- 0.3 mg.kg-1. The dose decreased with increasing age. There was no statistical relationship between the amount of propofol and intensity of the electric shock required to set off a seizure. The use of antidepressant drugs, and atopy did not influence the required amount of propofol. Speed of injection seemed to be the determining factor for narcosis with low doses of propofol. Hyperoxia and hypocapnia induced by hyperventilating with pure oxygen seemed to facilitate occurrence and duration of seizures. Although propofol has been said to reduce the length of seizures, there is controversy concerning the ECT efficacy criteria.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Use of propofol in 1350 anesthetized patients for electroconvulsive therapy]. 200 69

We studied the effects on breathing of seizures induced by focal injection of penicillin G into the parietal cortex in 13 anesthetized cats. Electrocorticograms, ventilation, end-tidal PCO2, and intrapleural and arterial pressures were monitored; changes of these variables were related to the stages of motor seizure. The first respiratory responses, tachypnea and hyperpnea, usually occurred before any peripheral muscular contractions developed. Progression of the seizure was always accompanied by further tachypnea and hyperpnea. The hyperpnea associated with all stages of seizure activity resulted in hypocapnia, which was sustained even during prolonged tonic-clonic motor convulsions that caused a threefold increase of metabolic rate. The extreme tachypnea of tonic generalized convulsions led to increased end-expiratory lung volume because of dynamic hyperinflation associated with very short expiratory durations in the tonic phase. We suggest that the profound effects of seizures on respiration are by feedforward mechanisms from the cortical focus itself and from subcortical circuits, such as hypothalamus, that become involved during seizure propagation and generalization. Peripheral respiratory feedback mechanisms are not important for the genesis of seizure-induced hyperpnea.
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PMID:Respiratory responses to focal and generalized seizures in cats. 203 5

The cerebral effects of sevoflurane were compared in dogs with those of enflurane and isoflurane. Initially, the minimum alveolar concentrations (MAC) of sevoflurane and enflurane were determined and the electroencephalographic (EEG) responses to increasing doses of sevoflurane (1.5, 2.0 and 2.5 MAC) or enflurane (1.5 and 2.0 MAC) in unparalysed animals were examined. Administration of sevoflurane was not associated with seizure activity at any concentration either during normocapnia (PaCO2 5.3 kPa) or hypocapnia (PaCO2 2.7 kPa), even in the presence of intense auditory stimuli. All dogs anaesthetized with enflurane demonstrated sustained EEG and motor evidence of seizure activity induced by auditory stimuli at concentrations of enflurane greater than 1 MAC, particularly during hypocapnia. In a separate group of dogs, the effects of increasing concentrations of sevoflurane and isoflurane (0.5, 1.5 and 2.15 MAC) were compared directly on arterial pressure, cardiac output and heart rate, cerebral blood flow and the cerebral metabolic rate for oxygen (CMRO2) using the venous outflow technique. Sevoflurane, in common with isoflurane, had minimal effects on cerebral blood flow at the concentrations studied, but significantly reduced the CMRO2 at end-tidal concentrations sufficient to produce a burst suppression pattern on the EEG (approximately 2.15 MAC). Both sevoflurane and isoflurane significantly decreased arterial pressure in a dose-dependent manner, but neither drug significantly altered cardiac output.
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PMID:Cerebral effects of sevoflurane in the dog: comparison with isoflurane and enflurane. 222 68

Day time video records of 14 girls with the Rett syndrome (RS) (6-17, mean 7 years) were analysed to correlate episodic abnormalities in respiration, movement and electroencephalograms (EEG). Records were compared with those of 12 healthy girls (6-18, median 14 years) who hyperventilated voluntarily. Three RS girls (6-7 years) had minimal respiratory dysrhythmia and showed no correlation between EEG respiration and movement. The other 11 RS girls (6-17 years) had severe awake respiratory dysrhythmia; 10 showing hyperventilation (with hypocapnia) which alternated with active expiratory apnoeic pauses and one with the latter only. All had periods of awake regular breathing with normal respiratory gases. In these girls EEG showed non-epileptic generalised slow activity some of which was paroxysmal. In the six youngest (6-10 years) of these 11 RS girls, non-epileptic paroxysms of EEG slow activity at 1 1/2-4 Hz occurred and were associated with periods of normal breathing and normal pCO2 levels whether girls were alert, drowsy or asleep, but were uncommon during episodes of hyperventilation (and hypocapnia). In four of these girls the EEG paroxysms occupied less than or equal to 1-3% of the time during periods of respiratory dysrhythmia (81 minutes) and 8-100% of the time during alert periods with normal breathing (29 minutes), p less than or equal to 0.001 for this difference. Short bursts of EEG slowing occasionally followed prolonged apnoeic pauses. In two cases brief partial complex seizures occurred. In five of these girls stereotypic movements exacerbated during episodes of respiratory dysrhythmia and reduced during normal breathing.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Correlation of electroencephalogram, respiration and movement in the Rett syndrome. 234 29

Cerebral computed tomography (CT) was performed before and after right-sided electroconvulsive therapy (ECT) in 40 patients aged 26-87 years with major affective disorders. Nine patients with a concomitant definite or possible non-acute organic brain disorder were included. Several patients had long seizure durations, maximum 6.5 min, caused by hyperventilation-induced hypocapnia. Twenty-nine patients received at least 16 treatments (maximum 46). No CT changes occurred following ECT. A questionable dilatation of the left temporal horn in a 69-year-old hypertensive man who recovered completely without side effects after 3 ECT sessions was probably unrelated to the ECT. Provided sufficient oxygenation, even relatively long ECT series and seizures lasting several minutes do not cause any brain damage visible on CT.
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PMID:Electroconvulsive therapy and cerebral computed tomography. A prospective study. 261 80

1. The goal of this study was to examine the regulation of resistance in the large arteries and small vessels that supply the brain stem. 2. We used a new method in anaesthetized cats to measure blood flow to the medulla (microspheres) and pressure (servo-null) in branches of the basilar artery that supply the medulla. Resistance was determined during normocapnia, hypercapnia, hypocapnia and seizures (produced with intravenous bicuculline). 3. Pressure in arteries that supply the medulla (150 microns internal diameter) was 71 +/- 4% (mean +/- S.E. of mean) of aortic pressure and large artery resistance was 31 +/- 4% of the total resistance in the medulla. Hypercapnia and seizures decreased large artery resistance by 67 and 50%, respectively, and hypocapnia increased large artery resistance by 58%. Small vessel resistance decreased by 82% during hypercapnia and by 43% during seizures, and increased by 96% during hypocapnia. 4. Thus, resistance of the large arteries (greater than 150 microns diameter) accounts for about one-third of the total vascular resistance in the brain stem. Both large arteries and small vessels respond to alterations in arterial carbon dioxide tension and seizures, and contribute to the regulation of blood flow to the brain stem.
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PMID:Role of large arteries in regulation of blood flow to brain stem in cats. 311 12

The influence of arterial O2 and CO2 tensions on electroconvulsive seizure duration was investigated in five mongrel dogs under consistent anaesthetic conditions. Seizure durations were measured in a randomized protocol of nine possible combinations of arterial gas tension spanning increased, normal or decreased levels of PaO2 and PaCO2. Seizure duration was directly related to PaO2 (p less than 0.00001) and inversely related to PaCO2 (p less than 0.0001). A significant synergism was evident at the extremes of PaO2 and PaCO2, with seizure duration being greater than predicted for hyperoxia-hypocapnia and hypoxia-hypercapnia and shorter than predicted for hypoxia-hypocapnia and hyperoxia-hypercapnia. We conclude that arterial gas tensions strongly influence ECT-induced seizure duration and through this may influence the therapeutic efficacy of electroconvulsive therapy.
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PMID:Arterial PaO2 and PaCO2 influence seizure duration in dogs receiving electroconvulsive therapy. 366 9


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