摘要:

The effect of isoflurane on cerebrospinal fluid pressure (CSFP) was determined in 20 patients undergoing craniotomy for intracranial supratentorial neoplasm or hematoma. In 15 of these patients, following endotracheal intubation, hyperventilation sufficient to result in Paco225–30 torr was begun simultaneously with the introduction of 1 per cent isoflurane. In the remaining five patients ventilation was equivalent, but normocapnia was maintained by adding CO2to the inspired gases. In the hypocapnic patients CSFPs did not increase above awake values (range 5–45 torr) following isoflurane administration. In the normocapnic patients CSFPs consistently increased. In three of these five patients the increases were precipitous, but were corrected rapidly by establishment of hypocapnia. The authors conclude that the known cerebral vasodilator properties of isoflurance can be countered effectively by hypocapnia. Furthermore, unlike the situation with halothane, it is not necessary to establish hypocapnia prior to introducing isoflurane in order to avoid CSFP increases.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Sevoflurane was submitted to phase-1 studies in man following extensive testing in animal species without evidence of toxicity. Sevoflurane, 2–3 per cent inspired during maintenance, was administered with oxygen to produce one hour of anesthesia in six healthy adult male volunteers. Respiratory and cardiovascular functions, the electroencephalogram, arterial blood gases, blood sevoflurane, inorganic fluoride and total, nonvolatile fluorine concentrations, and inspired and mixed expired sevoflurane concentrations were measured during exposure. Concentrations of expired sevoflurane, blood and urinary fluoride, and total nonvolatile fluorine metabolites were also measured after anesthesia. During exposure spontaneous respiratory frequency increased 28 per cent, respiratory minute volume changed insignificantly, and Paco2s averaged 50 torr. Pao2s remained near 400 torr. Arterial systolic blood pressure declined an average of 17 per cent. Pulse rate changed insignificantly. After an hour of exposure arterial blood serum inorganic fluoride concentrations averaged 22 μM and plasma nonvolatile organic fluorine concentrations averaged 9.1 mg/l, or 61.3 μM. Uptakes of sevoflurane averaged 94 (±63 SD) mmol. Following exposure 37 (±12) mmol of unaltered sevoflurane were estimated to be excreted in exhaled air and 0.90 mmol of inorganic fluoride and 163 mg, or 1.43 (±0.26) mmol of organic fluorine were excreted in the urine. Recoveries in exhaled air and urine averaged 51.5 (±2.4) per cent of uptake. There was no significant drug-exposure-related change in the chest radiogram, electrocardiogram, electroencephalogram, urinalysis results, complete blood count, prothrombin time, serum electrolytes, transaminases, or hepatic and renal functions during four weeks following exposure compared with preexposure values. Sevoflurane produced anesthesia of excellent quality; it appears to undergo limited biotransformation and to have little or no systemic toxicity.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

The authors describe an 18-compartment hybrid computer multiple model of the uptake and distribution of halothane. This model uses 88 equations and 124 parameter settings. Three submodels are incorporated into the basic model: 1) The mass transport of halothane is simulated on the digital portion of the hybrid computer. 2) A breath-by-breath pulmonary model with two compartments describes air pressure-flow relations in the airway system. 3) A beat-to-beat cardiovascular model with 15 compartments describes in detail blood pressure-flow relations. In addition, a baroreceptor-heart rate loop is included: an increase in arterial pressure causes a decrease in heart rate. The slope of the baroreceptor response is progressively decreased by halothane until at 2 per cent there is no response.The model of halothane uptake and distribution is separate from the blood and air pressure-flow models, but is, in effect, driven by them. Myocardial “contractility” (stroke volume) and certain regional vascular resistances can be affected by the concentration of halothane in one or any proportion of any combination of three compartments: arterial blood (arteriolar concentration), cerebral gray matter, or myocardial. In turn, these factors significantly affect the uptake and distribution of halothane.The responses to three steady-state concentrations, as well as to a step change in concentration from 0 to 2 per cent, were examined. Twenty-four outputs were recorded, including halothane concentrations in ten compartments; myocardial “contractility”; left and right ventricular and right atrial pressures; cardiac output; stroke volume, R–R interval; and blood flows in six regions. Two variables—alveolar concentration of halothane and arterial blood pressure—were recorded during a step change of 0 to 5 per cent.The model describes the appropriate steady-state and dynamic cardiovascular responses to halothane. It also demonstrates the complex interrelationships among cardiac output, regional blood flow distribution, and the uptake and distribution of halothane. During step changes in halothane concentration, most of the responses occur early, a phenomenon also seen in man and goats.Thus, the model is useful not only for representing organ and tissue halothane concentrations, but also for gaining new insights into cardiovascular alterations produced by rapidly changing concentrations of halothane and into the complex interactions between the circulation and the uptake and distribution of halothane.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

The authors have described a basic hybrid computer multiple model of the circulation, ventilation, and uptake and distribution of halothane in a companion paper. A multiple model consists of two or more submodels, each of which is complete in itself and could operate independently. In a multiple model, however, each submodel interacts with the others. The present paper describes the addition of a CO2-control loop (submodel), through which the partial pressure of CO2modulates ventilation, as well as myocardial “contractility,” arterial pressure, cardiac output, and regional vascular resistances. The concentration of halothane modifies these CO2-induced modulations. The CO2- and halothane-induced changes in ventilation and circulation in turn modify the uptake and distribution of halothane. Thus, a complex set of interrelationships among the submodels and compartments exists.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Transient hyperreflexia, the Babinski reflex, and other transient neurologic signs may follow anesthesia in healthy persons. The authors describe the appearances and durations of these signs and relate them to anesthetic agent, time following cessation of anesthesia, and state of arousal.Twenty-nine neurologically normal male patients undergoing superficial operations were anesthetized with halothane-nitrous oxide, enflurane-nitrous oxide, or nitrous oxide-narcotic. During awakening, patients experienced transient hyperreflexia and shivering following all anesthetic techniques. Quadriceps hyperreflexia occurred in three of eight patients after halothane–N2O, seven of 12 patients after enflurane–N2O, and no patient after N2O-narcotic anesthesia. Sustained ankle clonus and upgoing plantar responses were observed most frequently following enflurane–N2O (50 per cent of patients). Following halothane–N2O, ankle clonus was observed in 12.5 per cent of patients and upgoing plantar responses in 25 per cent of patients. Neither sign occurred after N2O-narcotic anesthesia. Shivering, too, was observed most frequently following enflurane anesthesia (66 per cent of patients). There were equal reductions of body temperature in shivering and nonshivering patients. In every patient, regardless of the anesthetic used, the lash reflex and the pupillary response to light returned to normal with the return of consciousness as measured by the response to verbal commands.It is concluded that the neurologic proflle during awakening from general anesthesia is most abnormal following enflurane-N2O, compared with halothane–N2O and N2O-narcotic anesthesia. Abnormalities are found most frequently when patients are poorly responsive to verbal commands. Although their incidence diminishes with time, abnormal responses to neurologic examination may persist for 40 min or more after cessation of anesthesia.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

The effect of epinephrine given epidurally with local anesthet***s on uterine blood flow is controversial. Previous work in pregnant ewes demonstrated a transient but significant (14 per cent) decrease in uterine blood flow when 2-chloroprocaine with epinephrine (10 μg/ml) was used. The authors administered 2-chloroprocaine, 10 ml, with epinephrine (5 μg/ml) to 12 healthy women during the first stage of labor. By use of intravenously injected133Xe, intervillous blood flow was measured before and 15–20 min after epidural anesthesia to a somatic level of at least T10. Intervillous blood flow did not change significantly despite a decrease in mean blood pressure of 11 torr. These conflicting results are probably best explained by methodologic and species differences. It is postulated that human placental vasculature, unlike that of the ewe, undergoes vasodilatation when perfusion pressure is decreased to maintain placental blood flow.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Intrathecal injection of morphine was used to provide obstetric analgesia in 20 primiparous women in labor. When the cervix was at least 3 cm dilated, morphine, 1 or 2 mg, was injected intrathecally. In all parturients, labor pains were completely relieved after 15–60 min and analgesia lasted as long as eight to 11 hours. The analgesia was not associated with any alteration of pin-prick sensation or motor power, and there was no change in the arterial blood pressure or heart rate. All infants were delivered vaginally by use of episiotomy and a low forceps, except two infants of mothers in the 2 mg morphine group who needed cesarean section. During the second stage of labor, analgesia was supplemented by lidocaine, 2 per cent, using local perineal infiltration in 14 parturients and pudendal block in two parturients, and by epidural block in four parturients. Nineteen of the 20 newborns cried immediately at birth, and had Apgar scores of 7–9 at 1 min and 8–10 at 5 min. During the first 24 hours of life, the neurobehavioral responses of all newborns were scored as normal. Systemic maternal side effects such as somnolence, nausea, vomiting, and itching occurred in a high proportion of the parturients. However, in the majority of cases, these side effects were mild. Only two parturients of the 2 mg morphine group complained of marked somnolence, itching, and vomiting, which persisted post partum; these were effectively reversed by the specific antagonist naloxone.The analgesic effect of intrathecal morphine can be attributed to its action on the opiate receptors in the substantia gelatinosa of the dorsal horn of the spinal cord. However, supraspinal effects of morphine cannot be excluded. The low lipid solubility of morphine can explain its slow onset and prolonged duration of action. Also, this will result in minimal systemic absorption of morphine, which protects the fetus and results in selective maternal analgesia.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

To determine the relationship between respiratory muscle strength and changes in normal vital capacity (VG), graded levels of muscle weakness were produced in six healthy supine male subjects by four successive doses ofd-tubocrarine (0.05 mg/kg each). The maximal effect ofd-tubocurarine abolished hand-grip strength and ability to sustain head lift for 5 s, but VC was decreased to only 66 ± 3 per cent of control. At each level of weakness decreases in VC were significantly less than were decreases in respiratory muscle strength (RMS) monitored by maximum static inspiratory and expiratory pressures. The first dose decreased RMS to 86 ± 3 per cent of control, but VC was unchanged. Following the second dose, VC (97 ± 1 per cent of control) was minimally affected compared with RMS (71 ± 4 per cent). The VC after the third dose was still 85 ± 3 per cent of control, while RMS had decreased to 58 ± 2 per cent. Following the final dose ofd-tubocurarine (cumulative total 0.20 mg/kg), RMS was 39 ± 2 per cent of control, compared with VC, 66 ± 3 per cent of control. The relationship between VC and RMS was curvilinear and conformed to predictions based on the static mechanical characteristics of the normal respiratory system. These findings demonstrate that while VC is relatively spared during partial curarization, this sparing of VC does not indicate a similar extent of preserved RMS. Rather, it reflects the relative ease with which weakened respiratory muscles are able to drive the normal respiratory system in the supine subject. The same weakened muscles may be unable to generate sufficient force to handle mechanical challenges such as coughing and vomiting.

ISSN:0003-3022    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

A chronic model for investigation of spinal anesthesia in the dog is described. This model incorporates the use of a chronically implanted catheter in the lumbar subarachnoid space. An 18-gauge thin-walled Crawford needle is passed percutaneously into the subarachnoid space. An 18-gauge epidural catheter is then threaded through the needle into the subarachnoid space and the distal end attached to a special metal valve which is sutured under the skin. One-milliliter volumes of various local anesthetic solutions were injected intrathecally via the valve and catheter. Durations of the effects of the local anesthetics were evaluated. Duration of subarachnoid conduction blockade was defined as the time during which hind-limb paralysis persisted in the dog. The times to onset and durations of motor blockades were evaluated following the intrathecal injection of dibucaine, tetracaine, lidocaine, bupivacaine, chloroprocaine, and mepivacaine. Times to onset ranged from 1.1 to 2.3 min. Durations of motor blockade were longest for dibucaine and tetracaine, followed in order of decreasing duration by bupivacaine, lidocaine, chloroprocaine, and mepivacaine. The durations of subarachnoid conduction motor blockades in the dog are qualitatively similar to reported values for spinal anesthesia in man. Therefore, the technique described may provide a useful model to evaluate factors that may influence spinal anesthesia.

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