ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The authors studied the influence of locally administered isoflurane anesthesia on the pulmonary vascular response to regional alveolar hypoxia (hypoxic pulmonary vasoconstriction [HPV]) over a range of cardiac outputs (COs) in seven mechanically ventilated, closed-chest dogs. The right lung was ventilated with 100% O2throughout the study. The left lung was ventilated with either 100% O2(normoxia) or an hypoxic gas mixture (hypoxia). Different alveolar concentrations of isoflurane (0, 1, and 2.5 MAC) were administered to the left lung in a randomized sequence. The CO was altered by opening and closing surgically produced arteriovenous fistulae, at all isoflurane concentrations, and by hemorrhage at 0 MAC isoflurane. The magnitude of the HPV response was measured by differential CO2elimination in the absence of isoflurane and by venous admixtures in all phases. During normoxia, the left lung effective flow (&OV0422;L%) measured from differential CO2excretion was 39.9 ± 1.2% of the total blood flow and decreased to 18.8 ± 2.6% when ventilated with the hypoxic gas mixture. Venous admixture (&OV0422;VA/&OV0422;T%) was significantly correlated with &OV0422;L% during hypoxic ventilation in the absence of isoflurane. &OV0422;VA/&OV0422;T% was 22.3 ± 2.7% during hypoxia with normal CO, and it increased significantly to 27.7 ± 1.1% when the CO was increased 43%. It was not significantly altered (23.6 ± 3.6%) when the CO was decreased by 54%. Isoflurane 2.5 MAC significantly increased &OV0422;VA/QT% during hypoxic ventilation of the left lung to 33.9 ± 2.6% with low CO and 35.4 ± 1.7% with normal CO. Isoflurane 1 MAC increased &OV0422;VA/QT% to 27.2 ± 2.7% with normal CO and 28.1 ± 2.6% with high CO. Comparing the effects of the different concentrations of isoflurane on &OV0422;VA/&OV0422;T% during left lung hypoxia under the same conditions of CO, mixed venous and alveolar oxygen tension, and pulmonary artery and pulmonary artery occlusion pressures revealed a significant direct effect of isoflurane dose such that: (% depression of HPV) = [22.8(% alveolar isoflurane) – 5.3]. The ED50for this response was 2.4% alveolar isoflurane. The authors conclude that isoflurane directly depresses HPV and that secondary influences of the anesthetic action should be considered in the interpretation of the action of inhalational agents on this responsein vivo.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

It has been reported that animals exposed to relatively “bloodless” cerebral ischemia have improved cerebral function post-ischemia. This suggests the possibility that large variations in cerebral blood volume during complete ischemia might affect outcome following reperfusion. The purpose of this study was to determine whether changes in dog head position (and therefore cerebral blood volume) during complete cerebral ischemia produced by occluding the aorta and venae cavae affect post-ischemic cerebral blood flow (CBF), cerebral metabolic oxygen requirements (CMRO2), or neurologic outcome. Two dogs were transfused with111In-labeled red blood cells. Gamma camera images taken during complete cerebral ischemia showed 45-degree head-up dogs to have 30% of the cranial blood volume of a 10-degree head-down dog. CBF and CMRO290 min post-ischemia were not significantly different between the head-up and head-down groups in the 14 dogs studied. There was also no significant difference in neurologic outcome at 48 h post-ischemia between head-up and head-down dogs. The authors conclude that head position during complete cerebral ischemia has a major effect on cranial blood volume, but no effect on post-ischemic CBF, CMRO2, or neurologic outcome.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The authors studied the effects of vasodilator treatment with either hydralazine or minoxidil on gas exchange and lung water accumulation over a 5-h period in canine oleic acid-induced pulmonary edema. Thirty dogs were given intravenous oleic acid 1 day prior to study to produce a stable, diffuse lung injury. On the day of study, one group of animals was given minoxidil, a potent systemic and pulmonary vasodilator. A second group was given hydralazine, a potent systemic vasodilator but weak pulmonary vasodilator, and a third group was not treated. Hemodynamic and gas exchange variables were assessed prior to treatment, and again after 5 h of treatment. Both drugs caused an increase in cardiac output and a decrease in peripheral vascular resistance. Minoxidil increased venous admixture from 17 ± 4 to 55 ± 6% (P< 0.05), whereas hydralazine-treated dogs had a smaller increase, from 26 ± 5 to 47 ± 6% (P< 0.05), and untreated animals did not show a significant change. Lung water increased 27 ± 12% in the untreated animals over the course of the study, 43 ± 18% in the hydralazine animals, and 60 ± 16% (P< 0.05vs.untreated) in the minoxidil animals. The authors conclude that adverse effects may result from peripheral vasodilators in animals with permeability pulmonary edema, but the extent and severity of these effects may vary, depending on the drugs' effects on the pulmonary circulation.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The authors investigated the hemodynamic, metabolic, electroencephalographic (EEG), and electromyographic (EMG) characteristics of narcotic-induced rigidity during induction of anesthesia with alfentanil (175 μg/kg) in 10 patients. Thiopental (4 mg/kg) was administered to a ten-patient control group. Rigidity was quantified in eight muscle groups (sternocleidomastoid, deltoid, biceps, forearm flexors, intercostal, rectus abdominus, vastus medialis/lateralis, and gastrocnemius). Marked rigidity was observed in all muscle groups in all patients receiving alfentanil and in none receiving thiopental. Central venous pressure increased with onset of rigidity, while mean arterial pressure and cardiac index remained unchanged. Manual ventilation was extremely difficult during alfentanil-induced rigidity. Arterial oxygen tension decreased more rapidly during rigidity than during the same time interval in the control group, while patients experiencing rigidity were more acidotic, as reflected by greater increases in base deficit. The EEG demonstrated an anesthetic state without seizure activity. The immediate increase in central venous pressure with the onset of rigidity, along with occasional simultaneous parallel variations in central venous pressure and the EMG, strongly suggest a mechanical mechanism for the change in central venous pressure. The metabolic changes during rigidity may be partly related to the absence of the normal cardiovascular reflexes that are reported to occur during voluntary isometric muscle contractions. A neurochemical mechanism of narcotic-induced rigidity is briefly reviewed.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The effects of local anesthetics and a divalent cation, Ca2+, on the function of rhodopsin were estimated from the measurements of light-induced proton uptake. The light-induced proton uptake by rhodopsin in the rod outer segment disk membrane was enhanced at lowerpH (4) but depressed at higherpHs (6 to 8) by the tertiary amine local anesthetics lidocaine, bupivacaine, tetracaine, and dibucaine. The order of local anesthetic-induced depression of the proton uptake followed that of their clinical anesthetic potencies. The depression of the proton uptakeversusthe concentration of the uncharged form of local anesthetic nearly describes the same curve for small and large dose of added anesthetic. Furthermore, a neutral local anesthetic, bemocaine, depressed the proton uptake at allpHs between 4 and 7. These results indicate that the depression of the proton uptake is due to the effect of only the uncharged form. It is hypothesized that the uncharged form of local anesthetics interacts hydrophobically with the rhodopsin in the disk membrane. The dual effect of local anesthetics on the proton uptake, on the other hand, suggests that the activation of the function of rhodopsin may be caused by the charged form. There was no significant change in the light-induced proton uptake by rhodopsin when 1 mM of Ca2+was introduced into the disk membrane at varyingpHs in the absence or presence of local anesthetics. This fact indicates that Ca2+ion does not influence the diprotonating process of metarhodopsin; neither does it interfere with the local anesthetic-induced changes in the rhodopsin molecule.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Animal studies suggest that hyperglycemia (glucose concentrations > 225 mg/dl) occurring prior to periods of brain ischemia exacerbates neurologic damage. Neurosurgical patients, a group at risk for intraoperative brain ischemia, often receive glucose. Therefore, the effects of intraoperative glucose administration (IGA) on these patients were studied. Sixteen patients undergoing supratentorial craniotomy were randomly assigned to receive either 5% glucose in 0.9% sodium chloride solution (G) or 0.9% sodium chloride solution (S) infusion (both at a rate of 3–4 ml · kg−1· h−1) during the first 4 h of surgery. All patients received glucose infusions postoperatively. Plasma glucose, insulin, free fatty acids, alanine, ketones, base excess,pH, triglycerides, and lactate were measured during the infusion period and 24 h postoperatively. Urinary nitrogen was measured, commencing with the infusion and continuing for 24 h. Neurologic testing included preoperative and postoperative neurologic and psychomotor exams, time to extubation (min), and degree of alertness at the completion of anesthesia. The G group had significantly greater intraoperative plasma glucose concentrations at all time periods studied during the infusion (P< 0.05). Glucose levels ranged from 200–242 mg/dl compared with 12–160 mg/dl in G and S groups, respectively. G group hyperglycemia was within the range associated with exacerbation of ischemic brain damage in animal studies. Free fatty acids and ketones were significantly greater (P< 0.05) intraoperatively in the S group. Lactate and insulin were significantly greater in the G group at 4 h. Total urinary nitrogen was comparable in both groups but was significantly greater intraoperatively (P< 0.05) in the G group (13 ± 2vs.7 ± 1 mg · kg−1· h−1). No differences in the other metabolic indices were found. Likewise, no difference between groups was found in the neurologic variables; however, the number of patients studied was small. In summary, IGA produced plasma levels that have been associated with potentiation of ischemic neurologic damage, while patients receiving saline had much lower glucose levels. Because there does not appear to be any metabolic compromise in those not receiving glucose, the results suggest that glucose should be avoided during intracranial surgery.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The authors investigated the respiratory effects of diazepam in 24 healthy volunteers using a modified Read® rebreathing circuit. Resting end-tidal CO2(PETCO2) and the slopes of the ventilatory (&OV0312;E/PETCO2) and occlusion pressure (P0.1/PETCO2) response to CO2were measured just prior to and 5, 20, 40, and 60 min after diazepam, 0.1 mg/kg iv. The slope of &OV0312;E/PETCO2for all 24 subjects analyzed as a single group was never significantly depressed. The slope of P0.1/PETCO2for all 24 subjects analyzed as a single group was significantly depressed only at 5 min after diazepam. The resting PETCO2, however, had small but statistically significant increases throughout the 1 h of study. Group or cluster analysis of the slope of P0.1/PETCO2clearly divided subjects into one group of five subjects, whose P0.1/PETCO2slope was significantly and consistently augmented for 1 h and a second group of 19 subjects whose P0.1/PETCO2slope was always less than control for the entire hour. Diazepam may, through effects on pulmonary mechanics and/or the central nervous system, sometimes enhance respiratory responses to CO2rebreathing. Failure to select for such group effects when studying drug effects by CO2rebreathing may obscure the severity and duration of respiratory depression that occurs in the majority of individuals. Resting PETCO2indicated consistent depression of resting minute ventilation by diazepam and may be a more appropriate or sensitive measure of mild or subtle drug-induced respiratory effects.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Adrenal medulla cells are cholinoceptive cells. Stimulation of the acetylcholine receptor causes the influx of Ca to the cells, and Ca acts as the coupler of the stimulus–secretion coupling. In this study, the authors investigated the effects of halothane on the receptor-mediated influx of45Ca using cultured bovine adrenal medulla cells. Halothane at clinical concentrations (0.5–2%) inhibited the influx of45Ca caused by carbachol, with simultaneous inhibition of catecholamine secretion. The influx of45Ca and the secretion of catecholamines caused by K depolarization were inhibited by a large concentration of Mg, which competes with Ca at Ca channels, but not inhibited by halothane. Inhibition of the45Ca influx by halothane was not overcome by increase in the carbachol concentration. Inhibition of the45Ca influx by halothane was examined in comparison with that caused by a large concentration of Mg by the application of Scatchard analysis as the function of the external Ca concentration. Halothane decreased the maximal influx of45Ca without altering the apparent kinetic constant of Ca to Ca channels. On the contrary, a large concentration of Mg increased the apparent kinetic constant without altering the maximal influx of45Ca. Based on these findings, the authors suggest that inhibition of the45Ca influx by halothane was not due to the direct competitive inhibition of Ca channels, nor to the competitive antagonism of agonist-receptor interaction. As a possibility, halothane seems to inhibit the receptor-mediated activation of Ca channels through the interference of coupling between the receptor and Ca channels.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The authors used denaturing polyacrylamide slab gel electrophoresis, employing 7.5–20% and 15–20% polyacrylamide gradients, to compare total skeletal muscle proteins of 12 normal and 19 malignant hyperthermia (MH)-susceptible individuals. The patients' MH status was determined by contracture testing. No consistent qualitative or quantitative differences could be detected. Because MH is believed to be triggered by a loss of control of sarcoplasmic [Ca2+], the authors compared: 1) the Ca2+-binding proteins of eight normal and ten MH muscles using Ca2+-dependent electrophoretic mobility shifts and a transblot/45CaCl2overlay technique; and 2) the total protein composition of a heavy sarcoplasmic reticulum fraction isolated from five normal and nine MH muscles. Again, no differences were detected. Finally, a similar electrophoretic study was conducted to compare the total protein composition of five normal and six MH-susceptible, central core disease-affected human muscles. No significant differences could be observed. It appears, therefore, that simple electrophoretic techniques cannot be applied in the diagnosis of MH susceptibility.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID