摘要:

The autoradiographic14C-2-deoxy-D-glucose method was used to determine local cerebral glucose utilization (LCGU) during propofol anesthesia and recovery in 52 regions of the rat brain. Control rats intravenously received 5 ml · kg−1· h−1of the egg-oil-glycerol emulsion that constitutes the vehicle for propofol. Anesthetized animals received an iv bolus of propofol (20 mg/kg) followed by continuous infusion of the anesthetic at 12.5, 25, or 50 mg · kg−1· hr−1for 1 h prior to injection of14C-2-deoxy-D-glucose and for the following 45 min. In addition, a fifth group of animals were studied immediately after awakening from a 20 mg/kg bolus of propofol as indicated by the first reappearance of head lift. All rats were spontaneously breathing room air throughout the experimental procedure. The general pattern of the cerebral metabolic response to propofol anesthesia was a dose-related, widespread depression of LCGU. At the three infusion rates of propofol tested, overall mean LCGU was reduced by 33%, 49%, and 55%, respectively, and significant decreases were observed in 60%, 85%, and 90% of the regions assayed. These effects were rapidly reversible, since in the recovery group, LCGU returned to near control values in the majority of the brain areas. Although all of the anatomofunctional systems (sensorimotor, extrapyramidal, limbic, and reticular) were involved, forebrain structures showed a greater sensitivity to the depressant action of propofol than did hindbrain regions. The only structures in which glucose use was spared, even when the highest dose of propofol was infused, were the nuclei related to the auditory-vestibular system (cochlear and vestibular nuclei, lateral lemniscus, and superior olive). The pattern of metabolic changes produced by propofol resembles that observed after barbiturates, Althesin®, and etomidate.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The ability of nitrous oxide (N2O) to disrupt folate and vitamin B12metabolism was examined in young (2-month), middle-aged (12-month), and elderly (24-month) Fischer 344 rats. Abnormalities in folate metabolism were assessed in a noninvasive manner by measuring the urinary excretion of formic acid and formiminoglutamic acid (FIGLU), compounds that are elevated in the urine of mammals with a deficiency in folate. After a 6-h exposure to 60% N2O/40% O2, urinary formic acid excretion increased 3− to 25-fold the first day following N2O exposure and returned to background levels by the second day after exposure in all age groups. Urinary FIGLU excretion increased 100− to 300-fold in the first day following N2O exposure, with the highest FIGLU excretion rates found in the elderly rats and the lowest in the young rats. By the second day after N2O exposure, FIGLU excretion rates returned to baseline levels in all age groups. Plasma folate progressively decreased with increasing age, whereas no age-dependent changes were observed in red cell folate, liver folate, or plasma vitamin B12levels. The elderly rats demonstrated the highest vitamin B12content in the liver and the lowest vitamin B12content in the kidney compared to the other age groups. Hepatic methionine synthase activities (measured 16–21 days after N2O exposure) were elevated in the elderly compared to the middle-aged or young rats, but methionine synthase activities in kidney and brain were not different among the three different age groups. It was concluded that in rats, agingper seonly slightly influences the disruption of folate metabolism produced by exposure to N2O.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Relaxant responses to halothane and isoflurane were compared in helical strips of dog epicardial coronary arteries of different sizes: proximal large coronary arteries with outside diameters (OD) larger than 2.5 mm and distal small arteries with 0.7–0.9 mm OD. Responses to pharmacologic vasodilators, including nitroglycerin (NTG) and adenosine, were also studied for comparison. The relaxation induced by halothane in concentrations of 0.8–2.3% and by NTG (10−9–10−5M) was greater in proximal large coronary arteries than in distal small ones contracted with 20 mM KCl. In contrast, the relaxation by isoflurane (1.2–3.5%) and by adenosine (10−8–10−4M) was greater in small coronary arteries than in large ones. These results suggest that isoflurane is, like adenosine, preferentially a small artery dilator.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The degree of systolic hypotension causing failure and recovery were tested simultaneously with three oximeters (CSI 504US, Nellcor N-200, and Ohmeda 3740) in nine normal male volunteers. Perfusion of the right hand was slowly reduced and restored by 1) elevation of the hand plus systemic hypotension with nitroprusside if needed (EL); 2) clamp compression of the brachial artery (CL); 3) brachial cuff inflation (CU); and 4) intraarterial norepinephrine (NE). With EL, pulse pressure was normal whereas right radial arterial systolic pressure (SP) was 25.3 ± 12.4 mmHg at failure and 34.1 ± 13.3 at recovery (mean of three oximeters, n = 189). With CL, pulse pressure fell more than did mean pressure, and failure occurred at 37.3 ± 9.8 and recovery at 46.8 ± 17.6 mmHg, n = 84. With CL, threshold of function, defined as the average of failure SP and recovery SP, was 47.1 ± 13.5, n = 41 for Nellcor, higher than for either CSI (38.7 ± 14.5, n = 17) or Ohmeda (36.0 ± 3.4, n = 26) (P< 0.05). With EL, no difference among instruments was found (mean 29.7 ± 12.8, n = 189). Threshold was 58.2 ± 8.4, n = 17 with CU if cuff inflation was slow (filling veins), but recovery was similar to EL after rapid cuff occlusion. With NE, SP threshold was increased to 58.3 ± 21.0 with CL but only to 41.0 ± 13.8 with EL. Hypoxia to Sao270% reduced SP thresholds with CSI to 25.1 ± 12.0 and with Ohmeda to 21.0 ± 7.6 with EL, but had no effect on the Nellcor, nor on any oximeter with CL. With systolic pressure just above failure, flow measured by finger plethysmograph was usually zero and detection of an induced hypoxic transient was delayed in one test as much as 6 min. In normoxic subjects, Spo2decreased at threshold to 88.8 ± 11.5%, n = 210, suggesting that arterial O2was lost to tissue by pulsatile movement in and out of capillaries, or by transarterial diffusion. This suggests that failure of pulse oximeters on fingers occurs at pressures too low for adequate tissue perfusion except when vasoconstriction is present. There are minor threshold differences between instruments, but efforts to increase sensitivity may not be justified in view of the local arterial desaturation evident at current thresholds during normoxia.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The effect on endotracheal tube flammability of helium (He)-diluted oxygen and He-diluted nitrous oxide was determined with the oxidant O2(He) and oxidant N2O (He) indices of flammability. These values then were compared with the corresponding values for nitrogen dilution,i.e., oxidant O2(N2) and oxidant N2O (N2) indices of flammability. Four different types of endotracheal tubes were studied: polyvinylchloride (PVC), red rubber (RR), silicone (Si), and the Xomed (Xo) Lasershield® tube. The oxidant O2(He) indices are: PVC 0.274 ± 0.0055, RR 0.194 ± 0.0089, Si 0.194 ± 0.0055, and Xo 0.256 ± 0.0055. The oxidant N2O (He) indices are: PVC 0.526 ± 0.0055, RR 0.434 ± 0.0114, Si 0.416 ± 0.0055, and Xo 0.456 ± 0.0154. The oxidant O2(N2) indices are: PVC 0.254 ± 0.0055, RR 0.182 ± 0.0045, Si 0.200 ± 0, and Xo 0.230 ± 0. The oxidant N2O (N2) indices are: PVC 0.472 ± 0.0084, RR 0.356 ± 0.0055, Si 0.392 ± 0.0045, and Xo 0.444 ± 0.0114. These differences, although statistically significant, are modest and demonstrate only a small, and probably clinically not significant, preference of He over N2in decreasing flammability.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Skin-surface temperature gradients (forearm temperature – fingertip temperature) have been used as an index of thermoregulatory peripheral vasoconstriction. However, they have not been specifically compared with total finger blood flow, nor is it known how long it takes fingertip temperature to fully reflect an abrupt change in finger blood flow. Steady-state skin-temperature gradients were compared with total fingertip blood flow in 19 healthy volunteers. There was an excellent correlation between steady-state skin-surface temperature gradients and total fingertip blood flow measured with venous-occlusion volume plethysmography: gradient = 0.2 – 5.7 · log(flow), r = 0.98. The half-time for fingertip cooling after complete arterial obstruction (in 8 volunteers) was 6.6 ± 1.2 min. The authors conclude that skin-temperature gradients are an accurate measure of thermoregulatory peripheral vasoconstriction.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID