ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundThe perfect preanesthesia medication and its ideal route of administration are still debated, but for pediatric surgical patients undergoing brief procedures, preanesthesia medication is frequently omitted because of the concern that it will prolong the child's recovery from anesthesia. The effects of nasally administered midazolam on anesthetic recovery and hospital discharge times were determined in 88 ASA physical status 1 and 2 ambulatory surgical patients undergoing a brief surgical procedure.MethodsUsing a randomized, double‐blind, placebo‐controlled design, 88 ambulatory surgical patients 10–36 months of age undergoing myringotomy and tube insertion were entered into the study. All patients were randomly assigned to one of three medication groups. One group received 0.2 mg/kg intranasal midazolam; a second group received 0.3 mg/kg intranasal midazolam; and the third group received intranasal saline drops. All patients were anesthetized with nitrous oxide, oxygen, and halothane administered via mask. The duration of anesthesia lasted between 9 and 10 min. After preanesthetic medication, the children were evaluated for ease of separation and induction of anesthesia. In addition, the time from when the anesthetic was discontinued until the child recovered from anesthesia and the time the child was discharged home were recorded by a nurse observer blinded to the patient grouping.ResultsChildren receiving midazolam had smoother, calmer parent‐child separation and anesthesia induction scores, and their anesthesia recovery times and hospital discharge times were the same as those receiving placebo.ConclusionsFor children undergoing brief surgical procedures, nasal midazolam provides satisfactory anxiolysis without delaying anesthesia recovery and hospital discharge.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundData concerning chest wall configuration and the activities of the major respiratory muscles that determine this configuration during anesthesia in humans are limited. The aim of this study was to determine the effects of halothane anesthesia on respiratory muscle activity and chest wall shape and motion during spontaneous breathing.MethodsSix human subjects were studied while awake and during 1 MAC halothane anesthesia. Respiratory muscle activity was measured using fine‐wire electromyography electrodes. Chest wall configuration was determined using images of the thorax obtained by three‐dimensional fast computed tomography. Tidal changes in gas volume were measured by integrating respiratory gas flow, and the functional residual capacity was measured by a nitrogen dilution technique.ResultsWhile awake, ribcage expansion was responsible for 25 plus/minus 4% (mean plus/minus SE) of the total change in thoracic volume (Delta Vth) during inspiration. Phasic inspiratory activity was regularly present in the diaphragm and parasternal intercostal muscles. Halothane anesthesia (1 MAC) abolished activity in the parasternal intercostal muscles and increased phasic expiratory activity in the abdominal muscles and lateral ribcage muscles. However, halothane did not significantly change the ribcage contribution to Delta Vth(18 plus/minus 4%). Intrathoracic blood volume, measured by comparing changes in total thoracic volume and gas volume, increased significantly during inspiration both while awake and while anesthetized (by approximately 20% of Delta Vth, P < 0.05). Halothane anesthesia significantly reduced the functional residual capacity (by 258 plus/minus 78 ml), primarily via an inward motion of the end‐expiratory position of the ribcage. Although the diaphragm consistently changed shape, with a cephalad displacement of posterior regions and a caudad displacement of anterior regions, the diaphragm did not consistently contribute to the reduction in the functional residual capacity. Halothane anesthesia consistently increased the curvature of the thoracic spine measured in the sagittal plane.ConclusionsThe authors conclude that (1) ribcage expansion is relatively well preserved during halothane anesthesia despite the loss of parasternal intercostal muscle activity; (2) an inward displacement of the ribcage accounts for most of the decrease in functional residual capacity caused by halothane anesthesia, accompanied by changes in diaphragm shape that may be related to motion of its insertions on the thoracoabdominal wall; and (3) changes in intrathoracic blood volume constitute a significant fraction of Delta Vthduring tidal breathing.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundChanges in the distribution of respiratory drive to different respiratory muscles may contribute to respiratory depression produced by halothane. The aim of this study was to examine factors that are responsible for halothane‐induced depression of the ventilatory response to carbon dioxide rebreathing.MethodsIn six human subjects, respiratory muscle activity in the parasternal intercostal, abdominal, and diaphragm muscles was measured using fine‐wire electromyography electrodes. Chest wall motion was determined by respiratory impedance plethysmography. Electromyography activities and chest wall motion were measured during hyperpnea produced by carbon dioxide rebreathing while the subjects were awake and during 1 MAC halothane anesthesia.ResultsHalothane anesthesia significantly reduced the slope of the response of expiratory minute ventilation to carbon dioxide (from 2.88 plus/minus 0.73 (mean plus/minus SE) to 2.01 plus/minus 0.45 l *symbol* min sup ‐1 *symbol* mmHg sup ‐1). During the rebreathing period, breathing frequency significantly increased while awake (from 10.3 plus/minus 1.4 to 19.7 plus/minus 2.6 min sup ‐1, P < 0.05) and significantly decreased while anesthetized (from 28.8 plus/minus 3.9 to 21.7 plus/minus 1.9 min sup ‐1, P < 0.05). Increases in respiratory drive to the phrenic motoneurons produced by rebreathing, as estimated by the diaphragm electromyogram, were enhanced by anesthesia. Anesthesia attenuated the response of parasternal electromyography and accentuated the response of the transversus abdominis electromyography to rebreathing. The compartmental response of the ribcage to rebreathing was significantly decreased by anesthesia (from 1.83 plus/minus 0.58 to 0.48 plus/minus 0.13 l *symbol* min sup ‐1 *symbol* mmHg sup ‐1), and marked phase shifts between ribcage and abdominal motion developed in some subjects. However, at comparable tidal volumes, the ribcage contribution to ventilation was similar while awake and anesthetized in four of the six subjects.ConclusionsHalothane anesthesia enhances the rebreathing response of neural drive to the primary respiratory muscle, the diaphragm. These findings provide direct evidence that, at the dose examined in this study, halothane‐induced respiratory depression is caused by alterations in the distribution and timing of neural drive to the respiratory muscles, rather than a global depression of respiratory motoneuron drive.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundIt is estimated that 1.5 million Americans are infected with the human immunodeficiency virus (HIV‐1), and the consequences of HIV infection are a leading cause of death in women aged 15–44 yr. Thus, HIV‐1 disease, or acquired immunodeficiency syndrome, occurs with increasing frequency in the parturient, and there is little information concerning the risks of regional anesthesia. Fear of spreading infection to the central nervous system or adverse neurologic sequelae have led some clinicians to advise against regional anesthesia. Thus, this study was undertaken to evaluate the possible problems or risks associated with regional anesthesia in parturients infected with HIV‐1 and to determine whether anesthesia affected the clinical course of the disease.MethodsThe clinical course and immunologic function of 30 parturients infected with HIV‐1 were evaluated prospectively. Extensive medical and laboratory evaluation before delivery and 4–6 months postpartum was undertaken. Medical problems related to HIV‐1 disease and use of antiviral drugs also were monitored. The anesthetic management was dictated by the clinical situation and the patient's wishes with careful postpartum follow‐up to evaluate possible neurologic changes or infection.ResultsRegional anesthesia was administered in 18 parturients, and 12 received small doses of opioids or no analgesia. There were no changes in the immunologic parameters studied (CD4sup + p24, beta sub 2 microglobulins), and HIV‐1 disease remained stable in the peripartum period. There were no infections, complications, or neurologic changes in the peripartum period. Sixty‐eight percent of the infants were HIV‐l‐negative and, in 21% of infants, the HIV‐1 status was indeterminate (probably negative).ConclusionsThis prospective study of parturients infected with HIV‐1 demonstrated that regional anesthesia can be performed without adverse sequelae. There were no neurologic or infectious complications related to the obstetric or anesthetic course. The immune function of the parturient was stable in the peripartum period. Although the number of patients studied was small, with careful medical evaluation, regional anesthesia is an acceptable choice in the parturient infected with HIV‐1.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundFor pediatric patients, sevoflurane may be an alternative to halothane, the anesthetic agent used most commonly for inhalational induction. The induction, maintenance, and emergence characteristics were studied in 120 unpremedicated children 1–12 yr of age randomly assigned to receive one of three anesthesia regimens: sevoflurane with oxygen (group S), sevoflurane with nitrous oxide and oxygen (group SN), or halothane with nitrous oxide and oxygen (group HN).MethodsAnesthetic was administered (via a Mapleson D, F or Bain circuit) beginning with face mask application in incremental doses to deliver maximum inspired concentrations of 4.5% halothane or 7% sevoflurane. End‐tidal concentrations of anesthetic agents and vocal cord position were noted at the time of intubation. Elapsed time intervals from face mask application to loss of the eyelash reflex, intubation, surgical incision, and discontinuation of the anesthetic were measured. Heart rate, systolic, diastolic, and mean blood pressures, and end‐tidal anesthetic concentrations were measured at fixed intervals. Anesthetic MAC‐hour durations were calculated. The end‐tidal concentration of anesthetic was adjusted to 1 MAC (0.9% halothane, 2.5% sevoflurane) for at least the last 10 min of surgery. Intervals from discontinuation of anesthetic to hip flexion or bucking, extubation, administration of first postoperative analgesic, and attaining discharge criteria from recovery room were measured. Venous blood was sampled at anesthetic induction, at the end of anesthesia, and 1, 4, 6, 12, and 18–24 h after discontinuation of the anesthetic for determination of plasma inorganic fluoride content.ResultsInduction of anesthesia was satisfactory in groups SN and HN. Induction in group S was associated with a significantly greater incidence of excitement (35%) than in the other groups (5%), resulting in a longer time to intubation. The end‐tidal minimum alveolar concentration multiple of potent inhalational anesthetic at the time of intubation was significantly greater in patients receiving halothane than in patients receiving sevoflurane. Induction time, vocal cord position at intubation, time to incision, duration of anesthesia, and MAC‐hour duration were similar in the three groups. During emergence, the time to hip flexion was similar among the three groups, whereas the time to extubation, time to first analgesic, and time to attaining discharge criteria were significantly greater in group HN than in groups S and SN. Mean heart rate and systolic blood pressure decreased during induction in group HN but not in groups S and SN. The maximum serum fluoride concentration among all patients was 28 micro Meter.ConclusionsSevoflurane with nitrous oxide provides satisfactory anesthetic induction and intubating conditions; however, induction using sevoflurane without nitrous oxide is associated with a high incidence of patient excitement and prolonged time to intubation. There were greater decreases in heart rate and systolic blood pressure during induction with halothane than with sevoflurane; however, these differences may be dose‐related. The more rapid emergence with sevoflurane when compared with halothane is consistent with the low solubility of sevoflurane in blood and tissues. Children receiving sevoflurane for up to 9.6 MAC‐hours did not develop high serum fluoride concentrations.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundPostoperative nausea and vomiting is a distressing anesthetic complication that may delay discharge after ambulatory surgery. Effective prophylaxis for postoperative nausea and vomiting can be achieved in adults with lower doses of ondansetron, a 5‐hydroxytryptamine subtype 3 receptor antagonist, compared with chemotherapy‐induced emesis. However, the doses of ondansetron used in preventing postoperative nausea and vomiting in children are based on data from chemotherapy‐induced emesis. The dose‐related efficacy of intravenous ondansetron in the prophylaxis of postoperative emesis in the pediatric outpatient population was determined.MethodsIn a double‐blind, randomized placebo‐controlled study, 130 patients (mean age 5.7 plus/minus 3.4 yr) received placebo, 10, 50, or 100 micro gram/kg ondansetron during a standardized anesthetic. Episodes of postoperative vomiting or retching were recorded.ResultsIntravenous ondansetron in a dose of 50 micro gram/kg was more effective than placebo or a dose of 10 micro gram/kg in controlling the incidence and frequency of emesis in the hospital and during the first 24 postoperative hours. Increasing the dose of ondansetron to 100 micro gram/kg intravenously did not significantly reduce the incidence or frequency of emesis compared to 50 micro gram/kg intravenously.ConclusionsIntravenous ondansetron in a dose of 50 micro gram/kg is as effective as larger doses for the prophylaxis of emesis in children undergoing surgical procedures known to be associated with an increased risk for postoperative nausea and vomiting.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundThere is a need for a standard by which to compare the degree of subjective and behavioral impairment caused by anesthetic drugs, because anesthesiologists may not be able to gauge how extreme or important a statistically significant change in psychomotor functioning is. This study examined the psychomotor and subjective effects of alcohol at blood concentrations equal or greater than 0.10% as a standard with which to compare those effects caused by sedative and analgesic agents commonly used in ambulatory surgery.MethodsTwelve healthy human volunteers (11 men and 1 nonpregnant woman), with an average age of 28 yr (range 24–34 yr) and an average alcohol consumption of four drinks per week, were selected in this institutional review board‐approved study. Each subject was exposed to five drug conditions (70 mg/70 kg propofol intravenously, 2 mg/70 kg midazolam intravenously, 50 micro gram/70 kg fentanyl intravenously, 0.8 g/kg alcohol orally, and placebo orally and intravenously) in a double‐blind randomized fashion over five weekly sessions. Testing was done at baseline and at different intervals until 240 min after drug administration. Testing included psychomotor performance (Maddox Wing, eye‐hand coordination, auditory reaction time test, and digit symbol substitution test), subjective effects (strength of drug effect scale, drug liking scale, and visual analog scale), and short‐term memory. Psychomotor performance was used as an index of objective impairment, and mood was used as an index of subjective impairment.ResultsAfter consumption of the alcoholic beverage, a blood alcohol level of 0.11 plus/minus 0.003% (mean plus/minus SE) was obtained at 15 min after injection. The study drugs not only produced statistically significant impairment (i.e., impairment greater than that seen with placebo) but also, at one or more times after injection, produced impairment similar to that observed with alcohol at a blood alcohol concentration of 0.11%. Midazolam produced a similar degree of impairment to that of alcohol for a longer duration than did fentanyl and propofol.ConclusionsThis study provides evidence that degree of impairment caused by sedative and analgesic drugs used in ambulatory surgery is similar to that obtained with a dose of alcohol that produces a blood alcohol concentration of 0.11%. We suggest that anesthesiologists can use alcohol as a standard by which to assess degree of impairment produced by drugs used for sedation/analgesia.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundRecent technology allows for quantitative and selective measurement of A beta, A delta, and C fiber nerve transmission. To gain further insight into the physiology of differential block after lidocaine spinal anesthesia, the function of these different fibers was quantitatively measured over time, and these measurements were correlated with regression of anesthesia to pinprick, touch, cold, and tolerance of tetanic electrical current (equivalent to surgical incision).MethodsSix volunteers received lidocaine spinal anesthesia with 50 mg lidocaine (5% in dextrose). Cutaneous current perception thresholds at 2,000, 250, and 5 Hz, which stimulate A beta, A delta, and C fibers, respectively, were determined at L2‐L3 (medial aspect above knee) before and every 10 min after spinal anesthesia. Dermatomal levels to pinprick, touch, and cold were assessed every 5 min after spinal anesthesia. Tolerance to tetanic electrical stimulus was assessed at L2‐L3 every 10 min after spinal anesthesia.ResultsDifferential block was demonstrated by the sequential return of sensation to touch, pinprick, and cold at L2‐L3. Recovery of function of A beta, A delta, and C fibers correlated with return of sensation to touch (R2= 0.7, p = 0.03), pinprick (R2= 0.75, p = 0.02), and cold (R2= 0.67, p = 0.04) respectively. Loss of tolerance of surgical anesthesia corresponded to return of A beta current perception thresholds to baseline, whereas current perception thresholds for A delta and C fibers were still increased to greater than baseline (p = 0.025).ConclusionsDifferential sensory block during spinal anesthesia is due to different recovery profiles of A beta, A delta, and C fibers. Return of A beta current perception thresholds to baseline correlated with duration of surgical anesthesia as assessed with an electrical stimulation model.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BackgroundLung growth in children is associated with dramatic increases in the number and surface area of alveolated airways. Modelling studies have shown the slope of the alveolar plateau (phase III) is sensitive to the total cross‐sectional area of these airways. Therefore, the influence of age and body size on the phase III slope of the volumetric capnogram was investigated.MethodsPhase III slope (alveolar dcCO2/dv) and airway deadspace (VDaw) were derived from repeated single‐breath carbon dioxide expirograms collected on 44 healthy mechanically ventilated children (aged 5 months‐18 yr) undergoing minor surgery. Ventilatory support was standardized (VT= 8.5 and 12.5 ml/kg, [florin] = 8–15 breaths/min, inspiratory time = 1 s, end‐tidal partial pressure of carbon dioxide = 30–45 mmHg), and measurements were recorded by computerized integration of output from a heated pneumotachometer and mainstream infrared carbon dioxide analyzer inserted between the endotracheal tube and anesthesia circuit. Experimental data were compared to simulated breath data generated from a numeric pediatric lung model.ResultsAn increased VDaw, a smaller VDaw/VT, and flatter phase III slope were found at the larger tidal volume (P < 0.01). Strong relationships were seen at VT= 12.5 ml/kg between airway deadspace and age (R2= 0.77), weight (R2= 0.93), height (R2= 0.78), and body surface area (R2= 0.89). The normalized phase III slopes of infants were markedly steeper than that of adolescents and were reduced at both tidal volumes with increasing age, weight, height, and body surface area. Phase III slopes and VDawgenerated from modelled carbon dioxide washout simulations closely matched the experimental data collected in children.ConclusionsMorphometric increases in the alveolated airway cross‐section with lung growth is associated with a decrease of the phase III slope. During adolescence, normalized phase III slopes approximate those of healthy adults. The change in slope with lung growth may reflect a decrease in diffusional resistance for carbon dioxide transport within the alveolated airway resulting in diminished acinar carbon dioxide gradients.

ISSN:0003-3022    

出版商:OVID    

年代:1995

数据来源: OVID