摘要:

Mixtures of local anesthetics can combine the best features of both components. The authors assayed the systemic toxicity of local anesthetic mixtures given subcutaneously to mice. Convulsions regularly preceded death. The median convulsant dose (CD50) of bupivacaine was one-fourth that of lidocaine, and one-seventh that of chloroprocaine. The median lethal dose (LD50) of chloroprocaine was twice the CD50, whereas the LD50of bupivacaine was but little greater than the CD50. Hence, the more potent the agent, the greater is the chance of death from a convulsant dose of local anesthetic.Conversion to lidocaine-equivalent doses permitted comparisons between mixtures. None of the mixtures were more convulsant or more lethal than their parent components; lidocainecontaining mixtures were significantly less lethal than the lidocaine norm. Mixing increased the distance between convulsant and lethal doses, with survival from convulsions induced by bupivacaine-containing mixtures enhanced in particular. It is concluded that local anesthetic toxicity is essentially additive.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

The dosage and blood concentration of lidocaine required to produce central nervous and cardiovascular system toxicity in both nonasphyxiated and asphyxiated fetuses were determined in ten pregnant baboons with fetuses of average gestation of 158 days (term, 185 days). Lidocaine was infused into the fetal jugular vein until cardiac arrest occurred, following which fetal brain, heart, lungs, liver and kidneys were obtained. Mean dosage and blood concentration of lidocaine associated with seizures were 9.4 mg/kg and 15.2 µg/ml, respectively, in the nonasphyxiated fetuses, and 3.9 mg/kg and 5.6 µg/ml, respectively, in the asphyxiated ones. The dosage and blood concentration of the drug required to produce cardiac arrest were significantly higher in the nonasphyxiated group (35 mg/kg and 269 µg/ml, respectively) compared to the sphyxiated group (9 mg/kg and 40 µg/ml, respectively). Tissue-plasma ratios of lidocaine were significantly higher (P< 0.05) in the brain, heart, and liver of the asphyxiated fetuses as compared with the nonasphyxiated ones. The relative proportion of the injected dose found in the organs was also higher (P< 0.05) in the asphyxiated group. These results indicate that the increased sensitivity of the asphyxiated fetus to lidocaine may be related in part to a greater uptake of local anesthetics by the fetal organs.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Morphine is used as an anesthetic supplement. Its disposition in surgical patients under enflurane–nitrous oxide anesthesia has not been determined. Available data on morphine concentrations in plasma after equivalent intravenous doses are conflicting, possibly as a result of varying degrees of specificity of the analytical methods for the unchanged, pharmacologically active form of the drug. This study determined the pharmacokinetics of morphine (0.05, 0.1, 0.14, or 0.2 mg/kg) injected intravenously in 10 surgical patients anesthetized with enflurane–N2O–O2. Arterial plasma was analyzed for unchanged morphine and conjugated morphine. Specificity of the analytical procedure for unchanged morphine was achieved by the combination of solvent extraction and radioimmunoassay techniques. Kinetic indices were derived by nonlinear least-squares analysis of log concentration (ng/ml)vs. time relationships. Morphine disposition was independent of dose in this fourfold range and was best described by a three-compartment model with a mean elimination half-time (t1/2β) of 104 ± 5 min. The apparent volumes of distribution (Vd) and of the central compartment (V1) were 3.4 ± 0.2 and 0.13 ± 0.02 1/kg, respectively, while the clearance (ClB) was 23 ± 1 ml·min1·kg−1. Extraction of morphine by the liver appeared to be complete. Conjugated morphine was eliminated from plasma with a t1/2βof 169 ± 15 min. The ultimate elimination of morphine from the body was dependent upon its reuptake from slowly perfused peripheral tissues, k10> k31(P< .001).

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

The effect of halothane on cerebellar control of motor activity and on cerebellar cyclic 3′,5′-guanosine monophosphate (cGMP) content was studied in mice. Isoniazide and picrotoxin were used to increase motor activity and induce seizures associated with an increase in cerebellar cGMP content. Halothane markedly decreased the cerebellar cGMP content (by 60 per cent at 0.61 per cent, the concentration at which 50 per cent of mice lost righting reflex) and prevented the isoniazide-induced increase in cGMP content. Halothane, 0.61 per cent, significantly reduced both isoniazide- and picrotoxin-induced motor activity; the ED50convulsive dose of isoniazide (137.7 ± 7.04) and of picrotoxin (1.9 ± 0.2 mg·kg−1, sc) was about three times higher (402.2 ± 17.9 and 5.8 ± 0.6 mg·kg−1, sc, respectively) in mice exposed to halothane. In contrast, halothane did not alter the ED50convulsive dose of strychnine, which has a different site and mechanism of action, blockade of glycine receptors, a mechanism not involving the cerebellar system. These results indicate that halothane has a significant effect on the cerebellar control of motor activity and that cGMP plays an important role in the alteration of cerebellar function by halothane.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

The radioactive microsphere technique was used to investigate the distribution of blood flow during halothane anesthesia when either sodium nitroprusside (SNP) or saralasin, a competitive inhibitor of angiotensin II, was infused. Seventeen fasted male Wistar rats were anesthetized with halothane and received either saralasin (n = 6) or SNP (n = 11) to decrease mean arterial pressure 20 torr. Cardiac output was unchanged with SNP, but blood flow decreased 23 per cent to the brain, and 25 per cent to the kidney, while splanchnic flow increased 19 per cent (P< .05). There were 37 per cent less microspheres present in the lung after drug treatment. Saralasin did not alter cardiac output or flow to other organs but did cause a 49 per cent decrease in the number of microspheres found in the lung after drug treatment. An additional group of rats first received SNP, and then saralasin. This combination was not well tolerated, resulting in lethal hypotension and a mortality of 60 per cent. In the thirteen animals which were able to complete the protocol, increases in blood flow to the heart, kidney and splanchnic circulation were seen while brain flow decreased (P< .05). The number of microspheres in the lung also decreased after combined therapy. These studies demonstrate the differential effects of SNP and saralasin in lowering blood pressure. The use of combined drug treatment, when tolerated, may improve organ perfusion.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

We studied the role played by a shift in perfusion to hypoxic lung areas after pulmonary embolism in post embolic hypoxemia. A tracheal divider was used to separate hypoxic (N2ventilated) from oxygenated (100 per cent O2ventilated) lung in anaesthetized dogs. Relative perfusion was assessed from total133Xenon (133Xe) exhaled from each lung area after intravenous infusions. When one lung area was ventilated with N2and the other with O2at a normal PaCO2to allow hypoxic pulmonary vasoconstriction (HPV), there was a significant (P< 0.001) shift away from the hypoxic side. Starch or blood clots were then infused to produce pulmonary emboli. Starch emboli were distributed predominantly to the oxygenated lung. After blood clot embolization in normocapnic dogs, pulmonary artery pressure increased 15 torr, perfusion to the hypoxic lung increased from 14 ± 2 to 23 ± 1 per cent, and PaO2fell from 278 to 186 torr. When the degree of HPV was reduced in another group of dogs by hypocapnea, a similar increase in pulmonary artery pressure (14 torr) created by blood clot embolism did not shift perfusion or create hypoxemia. In all dogs the perfusion shift to hypoxic lung was sufficient to account for all the post embolic hypoxemia. In this dog model, post embolic hypoxemia is explained by preferential distribution of emboli to oxygenated lung followed by perfusion shift to hypoxic lung as the effect of HPV is overcome by pulmonary hypertension.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

This study was undertaken to determine the serum levels of free morphine base resulting from the epidural administration of morphine, and to correlate these serum levels with analgesic effect. Results from twenty-one patients are presented. Following major surgery with bupivicaine or lidocaine continuous epidural block as the primary anesthetic, 5 or 10 mg/70 kg body weight of preservative-free morphine sulfate was administered through the epidural catheter when the patient noted the onset of postsurgical pain. Serum morphine levels were determined at intervals between 5 and 240 min post injection using a liquid chromatography technique with electrochemical detection, and analgesic effectiveness was assessed using a linear pain analogue scale and the subjective response of the patient.The mean peak serum level in the patients receiving 5 mg/70 kg was 28.0 ± 20.6 ng/ml with mean serum levels declining to 2.1 ± 1.6 ng/ml over the four-hour post injection period. The patients receiving 10 mg/70 kg had a mean peak serum level of 49.7 ± 35.6 ng/ml with mean serum levels declining to 5.4 ± 4.8 ng/ml over the 4-hour postinjection period. Average onset of significant analgesia was 15 min postinjection. Duration of adequate analgesia varied from 4 hours to several days, the mean being 37.9 hours for those receiving 5 mg/70 kg, and 51.6 hours for those receiving 10 mg/70 kg.Side effects included pruritis, ameliorated with diphenhydramine, and urinary retention. Somnolence and slowing of respiratory rate which developed in one patient were reversed with naloxone without notable effect on the duration or intensity of the analgesic response to the epidural morphine. This study demonstrates the analgesic effectiveness of and the serum morphine levels consequent to the epidural administration of morphine, and supports the concept of a selective spinal analgesic action.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

In a double-blind, randomized study 16 healthy parturients received epidural morphine, 0.025 per cent, or bupivacaine, 0.25 per cent, for continuous lumbar epidural analgesia in active labor. Morphine was dissolved in dextrose to avoid possible inhibition by saline of agonist-receptor binding. Adequacy of analgesia was assessed using a simple pain relief score and by observing maternal blood pressure, pulse rate, and response to pin scratch. Skin temperature was measured to identify sympathetic blockade. Neonatal status was determined by Apgar scores, umbilical cord blood gas values, and neurobehavioral assessment at 2–4 and 20–26 hours postpartum. Bupivacaine provided pain relief in all 8 subjects, while morphine produced acceptable relief in only 2 subjects given 2.5 mg and 3.5 mg, respectively (P< 0.05). Six parturients having unsatisfactory analgesia with morphine later achieved good pain relief with 2-chloroprocaine, 2 per cent. Blood pressure decreased 5 min after bupivacaine (P< 0.05) but not after morphine. Changes in blood pressure were transient, with no patient requiring vasopressor therapy. Skin temperature increased after bupivacaine (P< 0.05) but not after morphine. Numbness to pin scratch was demonstrated in both morphine subjects with pain relief and in all bupivacaine subjects. Apgar scores and umbilical cord blood gas values were similar in both groups. Borderline status in the Scanlon neurobehavioral examination occurred in 6 neonates in the morphine group at the first assessment while all bupivacaine neonates were normal (P< 0.05). When 2-chloroprocaine was given after morphine, its mean duration of action was increased from a normal value of 40–65 min to 83 ± 5.5 min. Thus, morphine in dextrose, in the low doses employed, is unsuitable for continuous epidural analgesia in labor. Insufficient occupancy of opiate receptors by morphine provides a likely explanation of these findings.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Two experiments were conducted testing the duration of action of nitrous oxide on human performance. In the first experiment, 11 subjects inhaled 30 per cent nitrous oxide for two periods of 40 min each, 45 min apart. Their mental and psychomotor skills were measured using free recall, tapping board, arithmetic and flicker fusion tests before and 2, 12, 22 and 32 min after establishing an end-tidal concentration of N2O of 30 per cent. Recovery was tested using the same tests 2, 12, 22 and 32 min after discontinuation of N2O. Eleven additional subjects inhaled oxygen only and served as a control group. In the second experiment, 8 subjects received both 30 per cent N2O and oxygen in crossover fashion, and their flicker fusion threshold was measured. When compared to baseline or oxygen administration, N2O significantly impaired tapping rate, number of words recalled, and performance in arithmetic tests. The effects of N2O were maximal at 2 min and remained similar throughout the entire administration. In flicker fusion tests, the effects of N2O were similar to those of stimulant drugs; N2O improved the subjects' ability to discriminate the fusion of flickering light. Recovery was complete in 22 min. The effects of, and recovery from the second administration of N2O were similar to those of the first experiment. There was no evidence of development of tolerance to mental and psychomotor effects of the drug.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID