ISSN:0003-3022    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Isoflurane has protective properties during experimental global brain ischemia or hypoxia. However, this has not been evaluated in the more common case of focal ischemia,e.g., as caused by middle cerebral artery occlusion (MCAO). The authors therefore compared the effects of isoflurane, thiopental, and N2O/fentanyl anesthesia on neurologic and neuropathologic outcome in baboons subjected to 6 h of transorbital left MCAO. Prior to MCAO, animals were assigned to one of three groups: Group 1 (n = 7) received isoflurane (in O2/air) in concentrations sufficient to maintain deep burst suppression on the EEG (2.0% ± 0.5% inspired, mean ± SD); group 2 (n = 6) received thiopental (O2/air) in doses adequate to maintain similar EEG suppression (3.6 ± 0.7 g total); and group 3 (n = 6) received 60% N2O/40% O2and fentanyl (25 μg/kg load, 3 μg · kg−1· h−1infusion). Efforts were made to keep mean arterial pressure (MABP) between ≈80 and 100 mmHg, using nitroprusside/hydralazine or phenylephrine/metaraminol, with PaCO2at ≈30 mmHg. The selected anesthetic was established 45 min before MCAO, was maintained until 1 h after clip removal, and in decreasing concentrations for 5 h. Neurologic status was scored for 7 days and formalin-fixed brains were later sectioned for determination of infarction volume. Six of seven group 1 (isoflurane) animals were hemiplegic, and 7/7 had verified infarctions. By contrast, 4 of 6 group 2 (thiopental) animals were normal, with 2/6 having infarctions. Outcome in group 3 (N2O/fentanyl) was intermediate between groups 1 and 2 (3/6 hemiplegic, 4/6 with infarctions). Differences in the infarction rates between groups 1 and 2 was significant (P< 0.05), while a similar comparison of neurologic outcome scores achieved aPvalue of 0.055. Infarctions in group 1 were more hemorrhagic in character than in group 3 (groups 1 and 2 could not be meaningfully compared). These results must be considered in light of differences in MABP during the occlusion period; MABP in group 1 was ≈80 mmHg in spite of vasopressor use, while that in group 2 was ≈100 mmHg (in spite of vasodilators). Nevertheless, they fail to demonstrate any protective value of isoflurane anesthesia, at least when compared with thiopental.

ISSN:0003-3022    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

A randomized prospective study in both children and dogs compared ionization of calcium chloride and calcium gluconate. Five conditioned dogs under halothane anesthesia received calcium chloride (4, 8, 12 mg/kg) and calcium gluconate (14, 28, 42 mg/kg) intravenously. Ten children scheduled for burn wound excision and grafting received both calcium chloride (2.5 mg/kg) and calcium gluconate (7.5 mg/kg) injected through a central venous cannula. Ionized calcium was measured at 0, 0.5, 1,3,5, and 10 min in the children, and 0, 0.5, 1, 2, 3, 4, 5, 10, 20, and 45 min in the dogs. The authors conclude that equal elemental calcium doses of calcium gluconate (10%) and calcium chloride (10%) (approximately 3:1), injected over the same period of time, are equivalent in their ability to raise [Ca++] during normocalcemic states in children and dogs; the changes in [Ca++] following calcium administration are shortlived (minutes); rapidity of ionization seems to exclude hepatic metabolism as an important factor in the dissociation of calcium gluconate; and equivalent rises in [Ca++] produced by calcium gluconate or calcium chloride resulted in equivalent cardiovascular effects. The authors feel that either form of calcium salt would be satisfactory if indicated during cardiopulmonary resuscitation or for the treatment of ionized hypocalcemia due to massive blood transfusion.

ISSN:0003-3022    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

To determine the potencies of neostigmine, pyridostigmine, and edrophonium in reversing pancuronium and d-tubocurarine blockade, dose-response curves were established for first twitch height recovery and train-of-four ratio. One hundred and twenty ASA physical status I or II patients scheduled for elective surgery received either 0.06 mg/kg pancuronium or 0.36 mg/kg d-tubocurarine during a thiopental-nitrous oxide-enflurane anesthetic. Train-of-four stimulation was applied every 12s, and the force of contraction of the adductor pollicis muscle was recorded. When first twitch height had recovered spontaneously to 10% of its initial value, neostigmine (0.005, 0.01, 0.02 or 0.05 mg/kg), pyridostigmine (0.02, 0.04, 0.1, or 0.2 mg/kg), or edrophonium (0.1, 0.2, 0.4 or 1 mg/kg) was injected by random allocation. Recovery was measured 10 min after the injection of the antagonist. First twitch ED50's were 0.013, 0.085, and 0.17 mg/kg after pancuronium, and 0.017, 0.11, and 0.27 mg/kg after d-tubocurarine, for neostigmine, pyridostigmine, and edrophonium, respectively. The ED50 for pyridostigmine and edrophonium obtained after d-tubocurarine was significantly larger (P< 0.05) than that after pancuronium. The train-of-four dose-response curves were significantly flatter for edrophonium than for the other two agents, indicating a greater ability of edrophonium to antagonize fade at low doses. It is concluded that the potency of reversal agents may be different for different relaxants, and that potency ratios might depend upon the end-point chosen as full neuromuscular recovery.

ISSN:0003-3022    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The global myocardial extraction of lactate was measured in 13 halothane anesthetized dogs to assess the effect of electric counter-shock applied directly to the heart. Seven animals received two countershocks of 30 delivered joules each, while six animals were not shocked but were atrially paced to a rate of 190–200, both with and without occlusion of the vena cava to produce a mean arterial pressure of 40–50 mmHg. All animals had substantially positive lactate extraction in the baseline state (36 ± 10% for countershock groupvs.41 ± 3% for pacing group). Myocardial lactate extraction reached a markedly negative nadir 2.5 min after countershock (-19 ± 15%), but returned toward normal by 6 min (10 ± 6%). Lactate extraction was not significantly changed from baseline in the pacing group. The relationship between changes in regional myocardial blood flow (radiolabeled microspheres) and post-countershock myocardial damage (technetium pyrophosphate uptake) was assessed in six dogs shocked as above. Mean myocardial blood flow was increased minimally immediately after countershock (0.78 ± 0.08 ml · min−1· g−1vs.1.16 ± 0.3), but there was no difference in blood flow between damaged and undamaged tissue at either time point. The epicardial-to-endocardial ratio of blood flow was unchanged after countershock (0.97 ± 0.05vs.0.99 ± 0.08). There was no relationship between myocardial damage and either the absolute amount of blood flow after countershock (r = −0.03) or the change in blood flow compared with the pre-shock period (r = 0.01). These results show a dramatic reduction in aerobic metabolism immediately following electric countershock. The comparison with animals paced to profound tachycardia in the presence of systemic hypotension indicates that hemodynamic changes after countershock are not responsible for these changes. The lack of association between reduced myocardial blood flow and post-countershock myocardial damage does not support the hypothesis that post-countershock damage is caused by decreased myocardial perfusion. The authors speculate that the post-countershock anaerobic myocardial metabolism and myocardial lesions might be induced through direct damage of myocardial mitochondria.

ISSN:0003-3022    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Preterm infants may become apneic during the immediate postoperative period. To define this risk, the authors studied prospectively the breathing patterns of 47 preterm infants less than 60 weeks postconception with pneumocardiograms before and after general inhalational anesthesia. Eighteen infants (37%) had prolonged apnea (>15 s) postoperatively, and an additional seven infants (14%) had short apnea (6–15 s) postoperatively. An infant's risk of prolonged and short postoperative apnea was related to a young postconceptional age (P< 0.05) and to a history of necrotizing enterocolitis (P< 0.01). Furthermore, as the postconceptional age of the infant increased, the risk of postoperative apnea decreased proportionately (P< 0.025). Among the 18 infants with prolonged apnea, 83% experienced multiple apneic episodes. Manual stimulation was required in order for breathing to return in 13 (72%) of the infants. Breathing resumed spontaneously in four (22%) of the infants, and one infant required mechanical ventilation due to repeated prolonged apnea. The first apneic event occurred within 2 h postoperatively in 13 of the infants (72%); the remaining five infants (28%) had their initial apneic episode as late as 12 h after operation. The postoperative time to the last prolonged apneic event was inversely related to the postconceptional age (P< 0.01,r= −0.70) and extended up to 48 h postoperatively. The preoperative pneumocardiogram was not a reliable test for predicting postoperative apnea (sensitivity 56%, specificity 83%). Four infants with normal preoperative breathing pattern and no preoperative history of apnea experienced prolonged apnea after operation. These results confirm that, in preterm infants, apnea is a common problem following anesthesia. The authors conclude that preterm infants younger than 60 postconceptional weeks of age should be monitored continuously for at least 12 h postoperatively in order to prevent apnea-related complications.

ISSN:0003-3022    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

To study the effect of epoch length on the variability of power spectrum analysis of the EEG, 22 64-s segments of EEG were analyzed using epoch lengths of 2, 4, 8, 16, and 32 s. Nine of these segments exemplified EEG changes during transient anesthetic states or surgical conditions. Epoch-to-epoch variability was computed within frequency bins for all segments, and ANOVA with hierarchal classification was used to determine the length of the EEG segment necessary to identify a statistically significant change in those EEG segments recorded during changing conditions. In 16 segments, the epoch-to-epoch variability with power spectra were computed using 2-s epochs was significantly less than the variability when power spectra were computed using longer epoch lengths. In five segments, no significant difference existed between the variance at 2-s epochs and longer (4-s) epochs. In one case, an EEG containing a burst-suppression pattern, the variability was significantly increased when 2-s epochs were used. Analysis using 2-s epochs also identified changes more rapidly than analysis using any longer epoch length in eight of nine segments, and the differences were clinically significant as well (over 30 s faster when 2-s epochs were used instead of 16-s epochs). These findings suggest the preferability of short epoch lengths when power spectrum analysis is used for intraoperative EEG monitoring.

ISSN:0003-3022    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Intrathecally administered clonidine produces analgesia, but also produces hypotension. To assess the effects of epidural administration, the authors inserted lumbar epidural catheters in seven non-pregnant ewes, and injected, on separate days, clonidine (50–750 mcg), morphine (5–10 mg), and a clonidine-morphine combination (clonidine 150 mcg + morphine 5 mg). Clonidine produced dose-dependent antinociception and sedation, with the lowest maximally effective antinociceptive dose being 300 mcg. Morphine produced less intense antinociception than clonidine, and did not potentiate clonidine's effect. Antinociception, but not sedation, following clonidine injection was reversed by epidural injection of the α2-adrenergic antagonist, idazoxan. Epidurally administered naloxone and prazosin did not reverse clonidine's antinociceptive effect, nor did intravenously administered idazoxan. Epidurally administered clonidine did not decrease blood pressure or heart rate or affect arterial blood gas tensions or spinal cord histology. These data suggest that epidurally administered clonidine produces analgesia by a local, α2-adrenergic mechanism. In sheep, epidurally administered clonidine does not produce hypotension.

ISSN:0003-3022    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The effects of lidocaine on the fetal circulatory responses to asphyxia were evaluated in chronically instrumented pregnant sheep. Twenty-six preparations were studied. Animals were assigned to one of three groups. The animals in group I (N = 10) did not have umbilical cord occluders placed. Lidocaine at 0.1 mg · kg−1· min−1was infused to the mother for 180 min. The animals in group II (N = 11) had an umbilical cord occluder, which was inflated to induce fetal asphyxia (Pao215 mmHg) for 90 min. Occlusion was then maintained for an additional 180 min while lidocaine at 0.1 mg · kg−1· min−1was infused. The animals in group III (N = 5) also had an umbilical cord occluder inflated for 90 min. While occlusion was maintained for an additional 180 min, saline was infused, in place of lidocaine. The infusion rate of lidocaine of 0.1 mg · kg−1· min−1over 180 min resulted in a steady-state arterial lidocaine blood concentration in the mother of approximately 2.15 μg/ml. Fetal circulatory responses to asphyxia were evaluated before and after maternal infusion of lidocaine or normal saline. Measurements included heart rate, blood pressure, arterialpH, and blood gases. Cardiac output and organ blood flow were determined using the radio-labelled microsphere technique. In general, arterial and tissue lidocaine concentrations in asphyxiated fetuses were higher than those in the nonasphyxiated ones, the differences being significant in the brain, heart, liver, and adrenal glands. Ninety minutes of asphyxia resulted in a decrease in fetal heart rate, while the blood pressure and cardiac output did not change significantly. At the same time, there was a significant increase in blood flow to the fetal brain, heart, and adrenals. These fetal responses were not altered after a further 180 min of asphyxia during which either lidocaine or normal saline was infused to the mother. It is concluded that lidocaine, in moderate concentrations, does not alter fetal responses to asphyxia, although placental transfer of the drug is enhanced by fetal acidosis.

ISSN:0003-3022    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The purpose of the present study was to determine the effect of intravenously administered ephedrine upon uterine artery blood flow velocity (UBFV) in the gravid guinea pig subjected to terbutaline infusion and acute hemorrhage. Ephedrine, 1.0 mg/kg, was administered intravenously to ten chronically instrumented pregnant guinea pigs near term, before and after intravenous infusion of terbutaline and acute hemorrhage. Before terbutaline and hemorrhage, ephedrine increased maternal mean arterial pressure (MMAP) by 30 ± 1% (P= .0001) and 17 ± 1% (P= .0001) at 30 s and at 1 min after injection, respectively; UBFV was decreased by 10 ± 4% (P< .01) and 14 ± 4% (P< .01) at 1 min and at 90 s after injection, respectively. Infusion of terbutaline (1.5–6.0 ug · kg−1· min−1) increased maternal heart rate (MHR) by 22 ± 1% (P= .0001), decreased MMAP by 13 ± 2% (P= .0001), and decreased UBFV by 24 ± 3% (P= .0001). During hypotension resulting from acute hemorrhage, ephedrine, 1.0 mg/kg, was superior to placebo in restoring MMAP and UBFV toward the prebleed values. The authors concluded that ephedrine, 1.0 mg/kg, results in a small, transient decrease in UBFV in the normotensive gravid guinea pig. However, ephedrine aids restoration of UBFV in the gravid guinea pig rendered hypotensive by acute hemorrhage during terbutaline infusion.

ISSN:0003-3022    

出版商:OVID    

年代:1987

数据来源: OVID