ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundControversy exists as to the risk for postoperative apnea in former preterm infants. The conclusions of published studies are limited by the small number of patients.MethodsThe original data from eight prospective studies were subject to a combined analysis. Only patients having inguinal herniorrhaphy under general anesthesia were included; patients receiving caffeine, regional anesthesia, or undergoing other surgical procedures were excluded. A uniform definition for apnea was used for all patients. Eleven risk factors were examined: gestational age, postconceptual age, birth weight, history of respiratory distress syndrome, bronchopulmonary dysplasia, neonatal apnea, necrotizing enterocolitis, ongoing apnea, anemia, and use of opioids or nondepolarizing muscle relaxants.ResultsTwo hundred fifty-five of 384 patients from eight studies at four institutions fulfilled study criteria. There was significant variation in apnea rates and the location of apnea (recovery room and postrecovery room) between institutions (P < 0.001). There was considerable variation in the duration and type of monitoring, definitions of apnea, and availability of historical information. The incidence of detected apnea was greater when continuous recording devices were used compared to standard impedance pneumography with alarms or nursing observations. Despite these limitations, it was determined that: (1) apnea was strongly and inversely related to both gestational age (P = 0.0005) and postconceptual age (P < 0.0001); (2) an associated risk factor was continuing apnea at home; (3) small-for-gestational-age infants seemed to be somewhat protected from apnea compared to appropriate- and large-for-gestational-age infants; (4) anemia was a significant risk factor, particularly for patients > 43 weeks' postconceptual age; (5) a relationship to apnea with history of necrotizing enterocolitis, neonatal apnea, respiratory distress syndrome, bronchopulmonary dysplasia, or operative use of opioids and/or muscle relaxants could not be demonstrated.ConclusionsThe analysis suggests that, if it is assumed that the statistical models used are equally valid over the full range of ages considered and that the average rate of apnea reported across the studies analyzed is accurate and representative of actual rates in all institutions, the probability of apnea in non-anemic infants free of recovery-room apnea is not less than 5%, with 95% statistical confidence until postconceptual age was 48 weeks with gestational age 35 weeks. This risk is not less than 1%, with 95% statistical confidence, for that same subset of infants, until postconceptual age was 56 weeks with gestational age 32 weeks or postconceptual age was 54 weeks and gestational age 35 weeks. Older infants with apnea in the recovery room or anemia also should be admitted and monitored. The data do not allow prediction with confidence up to what age this precaution should continue to be taken for infants with anemia. The data were insufficient to allow recommendations regarding how long infants should be observed in recovery. There is additional uncertainty in the results due to the dramatically different rates of detected apnea in different institutions, which appear to be related to the use of different monitoring devices. Given the limitations of this combined analysis, each physician and institution must decide what is an acceptable risk for postoperative apnea.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundActivation of the sympathetic nervous system occurs when desflurane is inspired shortly after anesthetic induction and when the inspired concentration of desflurane is rapidly increased during steady-state periods of anesthesia. The purpose of this study was to determine the effectiveness and dose response of fentanyl pretreatment in attenuating the neurocirculatory responses to desflurane in healthy human volunteers.MethodsAfter Institutional Research Review Board approval, three study groups were selected and, in random order, received either placebo (n = 10), a 2.5-micro gram *symbol* kg sup -1 intravenous bolus of fentanyl citrate followed by a continuous infusion of 1 micro gram *symbol* kg sup -1 *symbol* h sup -1 (n = 9), or a 5.0-micro gram *symbol* kg sup -1 intravenous bolus followed by an infusion of 2 micro gram *symbol* kg sup -1 *symbol* h sup -1 (n = 11) before the administration of desflurane. Arterial (MAP) and central venous (CVP) pressures were measured directly, and heart rate (HR) was determined indirectly. Efferent muscle sympathetic nerve activity (SNA) was recorded from the peroneal nerve by microneurography. After neurocirculatory recordings at conscious unmedicated baseline and 12 min after fentanyl administration, anesthetic induction was carried out with 2.0 mg *symbol* kg sup -1 propofol and 0.2 mg *symbol* kg sup -1 vecuronium. Neurocirculatory measurements were repeated beginning 2 min after induction when desflurane was given via mask (semiclosed circle system, 6 l/min fresh gas flow, 100% Oxygen2) in three incremental 1-min steps (3.6%, 7.2% and 11%). Intubation occurred 10 min after propofol administration. Twenty minutes after intubation, recordings were obtained during two steady-state periods during which end-tidal concentrations had achieved 5.4% (0.75 MAC) and 11% (1.5 MAC) desflurane for at least 10 min. Data also were obtained during the rapid increase in the inspired gas concentration from 5.4% to 11% ("transition").ResultsNeurocirculatory variables did not differ between the three groups at conscious baseline, after fentanyl, and during steady-state periods of anesthesia. Propofol administration significantly reduced SNA and MAP. The MAP reduction was enhanced in the fentanyl-treated groups. After induction, the increases in SNA and MAP associated with the administration of desflurane by mask were not significantly reduced by fentanyl. The transition from 5.4% to 11% desflurane resulted in increases in SNA, HR, MAP, and fentanyl administration significantly attenuated the HR and MAP components. At the 11% steady-state measurement period, CVP was increased and MAP was decreased from conscious baseline, and these changes were not modified by fentanyl.ConclusionsThe administration of desflurane was associated with increases in SNA, HR, MAP, and CVP. Maximum sympathetic activation and hemodynamic responses occurred 4-5 min after initiating desflurane during induction and 2-3 min after increasing the inspired concentration of desflurane during the "transition" period. Although fentanyl partially attenuated the hemodynamic component in a dose-dependent fashion during the "transition" period, it did not significantly diminish the response during induction.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundAtelectasis, an important cause of impaired gas exchange during general anesthesia, may be eliminated by a vital capacity maneuver. However, it is not clear whether such a maneuver will have a sustained effect. The aim of this study was to determine the impact of gas composition on reappearance of atelectasis and impairment of gas exchange after a vital capacity maneuver.MethodsA consecutive sample of 12 adults with healthy lungs who were scheduled for elective surgery were studied. Thirty minutes after induction of anesthesia with fentanyl and propofol, the lungs were hyperinflated manually up to an airway pressure of 40 cmH2O. FI sub O2was either kept at 0.4 (group 1, n = 6) or changed to 1.0 (group 2, n = 6) during the recruitment maneuver. Atelectasis was assessed by computed tomography. The amount of dense areas was measured at end-expiration in a transverse plane at the base of the lungs. The ventilation-perfusion distributions (V with dot A/Q with dot) were estimated with the multiple inert gas elimination technique. The static compliance of the total respiratory system (Crs) was measured with the flow interruption technique.ResultsIn group 1 (FIO2= 0.4), the recruitment maneuver virtually eliminated atelectasis for at least 40 min, reduced shunt (V with dot A/Q with dot < 0.005), and increased at the same time the relative perfusion to poorly ventilated lung units (0.005 < V with dot A/Q with dot < 0.1; mean values are given). The arterial oxygen tension (PaO2) increased from 137 mmHg (18.3 kPa) to 163 mmHg (21.7 kPa; before and 40 min after recruitment, respectively; P = 0.028). In contrast to these findings, atelectasis recurred within 5 min after recruitment in group 2 (FIO2= 1.0). Comparing the values before and 40 min after recruitment, all parameters of V with dot A/Q with dot were unchanged. In both groups, Crsincreased from 57.1/55.0 ml *symbol* cmH2O sup -1 (group 1/group 2) before to 70.1/67.4 ml *symbol* cmH2O sup -1 after the recruitment maneuver. Crsshowed as low decrease thereafter (40 min after recruitment: 61.4/60.0 ml *symbol* cmH2O sup -1), with no difference between the two groups.ConclusionsThe composition of inspiratory gas plays an important role in the recurrence of collapse of previously reexpanded atelectatic lung tissue during general anesthesia in patients with healthy lungs. The reason for the instability of these lung units remains to be established. The change in the amount of atelectasis and shunt appears to be independent of the change in the compliance of the respiratory system.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundCase reports suggesting both pro- and anticonvulsant effect(s) of propofol have been published in recent years. The effects of sedative doses of propofol on epileptiform activities in patients suffering from intractable partial epilepsy were systematically investigated.MethodsFourteen patients suffering from complex partial seizures were studied. Electroencephalogram (EEG) was recorded from intracranial electrodes implanted in the hippocampi and temporal neocortex. Propofol was given as a computer-controlled infusion in four steps to achieve target plasma propofol concentrations of 0.3, 0.6, 0.9, and 1.2 micro gram/ml. Each concentration was maintained for 30 min, and steady-state kinetics were confirmed by blood levels drawn at 10th and 30th min at each level. Between the 15th and 30th min of each concentration of propofol, EEG was analyzed for presence of electroencephalographic seizure activity and/or number of interictal spikes (ILS). Effects of propofol on IIS frequency at different electrode sites were compared using a two-way repeated measures analysis of variance. A value of P < 0.05 was considered significant.ResultsNone of the patients developed a seizure during the 2 h of propofol infusion. No "false spikes" (spikes developing with propofol infusion in areas where no spikes were seen in baseline EEG) were seen. Although effects of propofol on IlS frequency were highly variable across patients and at different propofol doses in the same patient, there was no statistically significant effect of propofol on any electrode site with any of the doses studied.ConclusionsWe were unable to demonstrate a significant change in epileptiform activity with sedative doses of propofol in patients suffering from complex partial epilepsy.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundThe inability of edrophonium to rapidly reverse a deep nondepolarizing neuromuscular block may be due to inadequate dosage or a ceiling effect to antagonism of neuromuscular block by edrophonium. A ceiling effect means that only a certain level of neuromuscular block could be antagonized by edrophonium. Neuromuscular block greater than this could not be completely antagonized irrespective of the dose of edrophonium administered. The purpose of this study was to determine whether a ceiling effect occurred for antagonism of an atracurium-induced neuromuscular block by edrophonium and, if so, the maximum level of block that could be antagonized by edrophonium.MethodsIn 30 adult patients, atracurium was administered to maintain a constant neuromuscular block. The level of block varied between patients. Evoked adductor pollicis twitch tension was monitored. Incremental doses of edrophonium were administered while the infusion of atracurium continued. Increments were given until adequate recovery occurred, as defined by a train-of-four (TOF) ratio greater or equal to 70%, or until no further antagonism of the block could be achieved. The probability of being able to effect adequate recovery by antagonism with edrophonium was determined using a logistic regression model. Cumulative dose-response curves were constructed using the logit transformation of the neuromuscular effect versus the logarithm of the cumulative dose of edrophonium.ResultsIn 14 patients with a block of 25-77% depression of the first twitch response, antagonism by edrophonium to a TOF ratio greater or equal to 70% was possible, whereas in 16 patients with a 60-92% depression of T1, a TOF ratio > 70% was not achievable, indicating that a ceiling effect for antagonism by edrophonium occurred. A block of 67 plus/minus 3% (mean plus/minus SE) had a 50% probability of adequate antagonism. In patients in whom block was antagonized to a TOF ratio < 70%, 95% of the peak antagonistic effect occurred with an edrophonium dose of 0.8 plus/minus 0.33 mg *symbol* kg sup -1 (mean plus/minus SD).ConclusionsThere is a maximum level of neuromuscular block that can be antagonized by edrophonium to effect adequate recovery. The level corresponds approximately to the reappearance of the fourth response to TOF stimulation. It is probably safest to wait until this level of block occurs before edrophonium is given for reversal. Earlier administration will not hasten recovery.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundDirect laryngoscopy requires movement of the head, neck, and cervical spine. Spine movement may be limited for anatomic reasons or because of cervical spine injury. The Bullard laryngoscope, a rigid fiberoptic laryngoscope, may cause less neck flexion and head extension than conventional laryngoscopes. The purpose of this study was to compare head extension (measured externally), cervical spine extension (measured radiographically), and laryngeal view obtained with the Bullard, Macintosh, and Miller laryngoscopes.MethodsAnesthesia was induced in 35 ASA 1-3 elective surgery patients. Patients lay on a rigid board with head in neutral position. Laryngoscopy was performed three times, changing between the Bullard, Macintosh, and Miller laryngoscopes. Head extension was measured with an angle finder attached to goggles worn by the patient. The best laryngeal view with each laryngoscope was assessed by the laryngoscopist. In eight patients, lateral cervical spine radiographs were taken before and during laryngoscopy with the Bullard and Macintosh blades.ResultsMedian values for external head extension were 11 degrees, 10 degrees, and 2 degrees with the Macintosh, Miller, and Bullard laryngoscopy (P < 0.01), respectively. Significant reductions in radiographic cervical spine extension were found for the Bullard compared to the Macintosh blade at the atlantooccipital joint, atlantoaxial joint, and C3-C4. Median atlantooccipital extension angles were 6 degrees and 12 degrees for the Bullard and Macintosh laryngoscopes, respectively. The larynx could be exposed in all patients with the Bullard but only in 90% with conventional laryngoscope (P < 0.01).ConclusionsThe Bullard laryngoscope caused less head extension and cervical spine extension than conventional laryngoscopes and resulted in a better view. It may be useful in care of patients in whom cervical spine movement is limited or undesirable.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundMany clinicians now consider hypothermia indicated during neurosurgery. Active cooling often will be required to reach target temperatures < 34 degrees Celsius sufficiently rapidly and nearly always will be required if the target temperature is 32 degrees Celsius. However, the efficacy even of active cooling might be impaired by thermoregulatory vasoconstriction, which reduces cutaneous heat loss and constrains metabolic heat to the core thermal compartment. The authors therefore tested the hypothesis that the efficacy of active cooling is reduced by thermoregulatory vasoconstriction.MethodsPatients undergoing neurosurgical procedures with hypothermia were anesthetized with either isoflurane/nitrous oxide (n = 13) or propofol/fentanyl (n = 13) anesthesia. All were cooled using a prototype forced-air cooling device until core temperature reached 32 degrees Celsius. Core temperature was measured in the distal esophagus. Vasoconstriction was evaluated using forearm minus fingertip skin-temperature gradients. The core temperature triggering a gradient of 0 degree Celsius identified the vasoconstriction threshold.ResultsIn 6 of the 13 patients given isoflurane, vasoconstriction (skin-temperature gradient = 0 degree Celsius) occurred at a core temperature of 34.4 plus/minus 0.9 degree Celsius, 1.7 plus/minus 0.5 h after induction of anesthesia. Similarly, in 7 of the 13 patients given propofol, vasoconstriction occurred at a core temperature of 34.5 plus/minus 0.9 degree Celsius, 1.6 plus/minus 0.6 h after induction of anesthesia. In the remaining patients, vasodilation continued even at core temperatures of 32 degrees Celsius. Core cooling rates were comparable in each anesthetic group. However, patients in whom vasodilation was maintained cooled fastest. Patients in whom vasoconstriction occurred required nearly an hour longer to reach core temperatures of 33 degrees Celsius and 32 degrees Celsius than did those in whom vasodilation was maintained (P < 0.01).ConclusionsVasoconstriction did not produce a full core temperature "plateau," because of the extreme microenvironment provided by forced-air cooling. However, it markedly decreased the rate at which hypothermia developed. The [nearly equal] 1-h delay in reaching core temperatures of 33 degrees Celsius and 32 degrees Celsius could be clinically important, depending on the target temperature and the time required to reach critical portions of the operation.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundSpinal and epidural injection of local anesthetics are used to produce sympathetic block to diagnose and treat certain chronic pain syndromes. It is not clear whether either form of regional anesthesia produces a complete sympathetic block. Spinal anesthesia using tetracaine has been reported to produce a decrease in plasma catecholamine concentrations. This has not been demonstrated for epidural anesthesia in humans with level of anesthesia below C8. One possible explanation is that spinal anesthesia results in a more complete sympathetic block than epidural anesthesia. To examine this question, a cross-over study was performed in young, healthy volunteers.MethodsTen subjects underwent both spinal and epidural anesthesia with lidocaine (plain) on the same day with complete recovery between blocks. By random assignment, spinal anesthesia and epidural anesthesia were induced via lumbar injection. Before and 30 min after local anesthetic injection, a cold pressor test (CPT) was performed. Blood was obtained to determine epinephrine and norepinephrine plasma concentrations at four stages: (1) 20 min after placing peripheral catheters, (2) at the end of a 2-min CPT (before conduction block), (3) 30 min after injection of epidural or spinal lidocaine, and (4) at the end of a second CPT (during anesthesia). Mean arterial pressure, heart rate, noninvasive cardiac index, and analgesia to pin-prick were monitored.ResultsNeither spinal nor epidural anesthesia changed baseline resting values of catecholamines or any hemodynamic variable, except heart rate, which was slightly decreased during spinal anesthesia. Median level of analgesia was T4 during spinal and T3 during epidural anesthesia. CPT before conduction block reliably increased heart rate, mean arterial pressure, cardiac index, epinephrine, and norepinephrine. Conduction block attenuated the increase in response to CPT only in mean arterial pressure (spinal and epidural) and cardiac index (spinal only). Neither technique blocked the increase in heart rate, norepinephrine, or epinephrine to CPT.ConclusionsSpinal anesthesia did not result in a more complete attenuation of the sympathetic response to a CPT than did epidural anesthesia. In response to the CPT, spinal anesthesia blocked the increase in cardiac index, and epidural anesthesia resulted in a decrease in total peripheral resistance compared to the pre-anesthesia state. The differences between the techniques are not significant and are of uncertain clinical implications.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundTo determine suitability for ablation procedures in children, two commonly used anesthetic agents were studied: propofol and isoflurane.MethodsTwenty patients presenting for a radiofrequency catheter ablation procedure were included and randomly assigned to two groups. A baseline electrophysiology study was performed during anesthesia with thiopental, alfentanil, nitrous oxide, and pancuronium in all patients. At the completion of the baseline electrophysiology study (EPS), 0.8-1.2% isoflurane was administered to patients in group 1 and 2 mg/kg propofol bolus plus an infusion of 150 micro gram *symbol* kg sup -1 *symbol* min sup -1 was administered to patients in group 2. Nitrous oxide and pancuronium were used throughout the procedure. After 30 min of equilibration, both groups underwent a repeat EPS. The following parameters were measured during the EPS: cycle length, atrial-His interval, His-ventricle interval, corrected sinus node recovery time, AV node effective refractory period, and atrial effective refractory period. Using paired t tests, the electrophysiologic parameters described above measured during propofol or isoflurane anesthesia were compared to those measured during baseline anesthesia. Statistical significance was accepted as P < 0.05.ResultsThere was no statistically significant difference in the results obtained during baseline anesthesia when compared with those measured during propofol or isoflurane anesthesia.ConclusionsNeither propofol nor isoflurane anesthesia alter sinoatrial or atrioventricular node function in pediatric patients undergoing radiofrequency catheter ablation, compared to values obtained during baseline anesthesia with alfentanil and midazolam.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID