摘要:

The study evaluated the effects of different anesthetics on the hepatic oxygen supply-demand relationship and hepatic lactate uptake (HLu). Miniature pigs (n = 33), weighing 20–31 kg, were divided into five groups and accordingly anesthetized with halothane, isoflurane, enflurane (0.9%, 1.5%, and 2.2% end-expired concentrations, respectively), fentanyl (100 μg/kg iv bolus followed by a continuous infusion of 50 μg · kg−1· h−1), or sodium pentobarbital (30 mg/kg iv bolus followed by a continuous infusion at a rate of 1–2 mg · kg−1· h−1). The surgical preparation allowed the authors to induce a stepwise decrease in hepatic blood supply without congestion in the preportal tissues. Prior to induced hepatic hypoperfusion, the values of hepatic oxygen delivery (HDO2) were the greatest in the isoflurane and fentanyl groups and the smallest in the halothane group, while the values of hepatic oxygen uptake (HVO2) were the smallest in the halothane group without differences among the other four groups. During stepwise decrease in hepatic blood and oxygen supply, HLu started to decrease at higher values of hepatic oxygen delivery in the fentanyl group (HDO2= 10 mlO2· min−1·100 g−1) than in all others (HDO2=6–7 mlO2· min−1·100 g−1). At values of HDO2equal to 2–3 mlO2· min-1· 100 g−1, the values of HLu became negative, signifying that the liver began to release rather than to metabolize lactate. There was a linear relationship between the values of HDO2and hepatic venous oxygen tension or saturation (r = 0.96;P< 0.001). Among the five anesthetics studied, isoflurane and fentanyl provided the greatest values of HDO2and hepatic venous oxygen supply-demand ratios. Halothane decreased hepatic oxygen demand and could have provided some protection from hepatic oxygen deprivation. However, the decrease in hepatic oxygen delivery produced by halothane was greater than the decrease in hepatic oxygen demand; therefore, halothane might not be the anesthetic of choice for surgical procedures where hepatic hypoxia is anticipated. Oxygen saturation in hepatic venous blood is an indicator of adequacy of hepatic oxygen supply.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The cell length of single, isolated rat and dog heart cells was monitored during exposure to halothane-containing solution to define the cellular mechanism of halothane's negative inotropic effect. Spontaneous contractile waves, which reflect spontaneous Ca release from the sarcoplasmic reticulum (SR) in resting rat heart cells, exhibited a significant increase in frequency and a decrease in amplitude in the presence of halothane 0.27 mM (0.9 vol%) and 0.55 mM (1.7 vol%). Electrically stimulated dog and rat heart cells abruptly exposed to halothane (0.47–0.55 mM or 1.5–1.7 vol%) revealed a transient increase in twitch amplitude (significantly different from control). Twitch amplitude then declined to values significantly below control as halothane exposure continued. This decrease in twitch reached 42 ± 13% (mean ± SD) of control in rat cells and 50 ± 14% in dog cells beating at 60 beats per min. In dog cells the magnitude of the transient increase in twitch amplitude was greater at faster beating rates compared with lower rates in the same cells (P< 0.01) and the transient increase was insensitive to verapamil. Halothane 0.55 mM (1.7 vol%) also significantly accelerated the rate of decline in the twitch amplitude of successive beats in rat cells stimulated after a rest interval (negative staircase). The findings regarding spontaneous contractile waves indicate a direct effect of halothane at the SR in resting cells, occurring independently of any changes in the slow inward current. The halothane-induced changes in beating cells can be explained by an enhancement of Ca release from the SR with an eventual reduction of SR Ca stores.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The authors studied the effects of thiopental on baseline airway tone in intact guinea pig tracheas using a preparation where the epithelial (inside) and serosal (outside) surfaces were isolated. Whole tracheas were excised, cannulated, and mounted in 50-ml tissue baths. The serosal and epithelial surfaces were perfusedviaseparate circuits with Krebs-Henseleit solution. All data were expressed as a percent of constriction produced by 2 × 10−6M carbachol (a concentration that elicited a 90 + % of maximal constriction). Thiopental elicited a dose-dependent constriction in all 25 tracheas. Increases in tone were first seen at 10−5M (14.3 ± 1.84%; mean ± SEM) and reached a peak at 10−3M (29 ± 3.16%;P<.0001). Responses to thiopental were similar when the epithelium was removed, when thiopental was added to the inner perfusate, and when tracheas were pretreated with 10−5M pyrilamine. Constriction was entirely inhibited by pretreatment with indomethacin 10−5M. The authors conclude that thiopental, at concentrations in the clinical range, causes a reproducible dose-dependent constriction of guinea pig trachea. This effect is mediated by constrictor prostaglandins.

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:

Contractile mechanisms of endothelin, a newly isolated vasoactive substance from endothelium, were evaluated in anterior cerebral arteries (ACA). Furthermore, the effects of thiopental, pentobarbital, ketamine, and diltiazem on the endothelin-induced cerebral vasoconstriction were also studied. Endothelin induced cerebral arterial contractions in concentrations above 3 × 10−10M. The median effective concentration (ED50: ×10−9M) of endothelin was 2.1 ± 0.7 (n = 6). Endothelin did not elicit contractions in preparations soaked in Ca2+-free solution, but addition of 2.5 mM Ca2+to the baths induced marked contractions. Thiopental and pentobarbital attenuated endothelin-induced contractions at concentrations above 3 × 10−4M, while ketamine was effective above10−3M. In contrast, diltiazem decreased endothelin-induced vasoconstriction at 10−6M. The findings suggest that endothelin may cause contractions of porcine cerebral arteries by influx of Ca2+through Ca2+channels. The cerebral vasomotion induced by endothelin, however, does not seem to be influenced by clinical doses of barbiturates and ketamine.

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

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