ISSN:0003-3022    

出版商:OVID    

年代:1997

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1997

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1997

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background:Recovery of the train‐of‐four (TOF) ratio to a value > 0.70 is synonymous with adequate return of neuromuscular function, but there is little information available concerning the subjective experience that accompanies residual neuromuscular block wherein the TOF ratio is in the range of 0.70 to 0.90.Methods:Ten American Society of Anesthesiologists' (ASA) physical status 1 volunteers were studied. Control measurements included grip strength in kilograms and ability to perform a 5‐s head‐ and leg‐lift. In addition, a standard wooden tongue depressor was placed between each subject's incisor teeth, and he or she was told not to let the investigator remove it. All subjects were easily able to retain the device despite vigorous attempts to dislodge it. Neuromuscular function was monitored with a Datex(TM) (Datex Medical Instrumentation, Inc., Tewksbury, MA) 221 electromyographic (EMG) monitor. TOF stimulation was given every 20 s, and the measured TOF fade ratio was continuously recorded. A 5 mg/kg bolus of mivacurium was then administered, and an infusion at 2 mg [center dot] kg sup ‐1 [center dot] min sup ‐1 was begun. The infusion was continued until the TOF ratio decreased to < 0.70 and was adjusted to keep it in the range of 0.65 to 0.75. Signs and symptoms of weakness were recorded when the TOF ratio had been stable +/‐ 0.03 for at least 10 min during an interval when there were no adjustments in the infusion. All tests noted previously were repeated at this time. The TOF ratio was then allowed to recover to 0.85–0.90. When stable at this level, all tests were repeated, and the infusion was discontinued. TOF measurements were continued until a ratio of 1.0 was attained and until a final set of observations was recorded.Results:The TOF ratio in all subjects was reduced to < 0.70. No volunteers required intervention to maintain a patent airway, and the hemoglobin oxygen saturation while breathing air was greater or equal to 96% at all times. TOF ratios less or equal to 0.90 were accompanied by diplopia and difficulty in tracking moving objects in all subjects. The ability to strongly appose the incisor teeth did not return until the TOF ratio (on average) exceeded 0.85. A sustained 5‐s head‐lift was not achieved until the TOF ratio averaged 0.60 (range, 0.45–0.75). At a TOF ratio of 0.70, grip strength averaged 59% of control (range, 50–75%). With certain exceptions (vision, ability to clench the teeth tightly), there was wide variation in symptomatology between patients for any given TOF ratio. It is impossible to give reliable TOF break‐points at which symptoms and signs will be present or absent.Conclusions:All subjects had significant signs and symptoms of residual block at a TOF ratio of 0.70; none considered themselves remotely “street ready” at this time. The authors believe that satisfactory recovery of neuromuscular function after mivacurium‐induced neuromuscular block requires return of the TOF ratio to a value > 0.90 and ideally to unity.

ISSN:0003-3022    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background:Sweating, vasoconstriction, and shivering have been observed during general anesthesia. Among these, vasoconstriction is especially important because‐once triggered‐it minimizes further hypothermia. Surprisingly, the core‐temperature plateau associated with vasoconstriction appears to preserve core temperature better in infants and children than adults. This observation suggests that vasoconstriction in anesthetized infants may be accompanied by hypermetabolism. Consistent with this theory, unanesthetized infants rely on nonshivering thermogenesis to double heat production when vasoconstriction alone is insufficient. Accordingly, the authors tested the hypothesis that intraoperative core hypothermia triggers nonshivering thermogenesis in infants.Methods:With Ethics Committee approval and written parental consent, the authors studied six infants undergoing abdominal surgery. All were aged 1 day to 9 months and weighed 2.4–9 kg. Anesthesia was maintained with propofol and fentanyl. The infants were mechanically ventilated and allowed to cool passively until core (distal esophageal) temperatures reached 34–34.5 degrees Celsius. Oxygen consumption‐the authors' index of metabolic rate‐ was recorded throughout cooling. Because nonshivering thermogenesis triples circulating norepinephrine concentrations, arterial blood was analyzed for plasma catecholamines at [nearly equal] 0.5 degrees Celsius intervals. Thermoregulatory vasoconstriction was evaluated using forearm ‐ fingertip, skin‐surface gradients, with gradients exceeding 4 degrees Celsius, indicating intense vasoconstriction. The patients were subsequently rapidly rewarmed to 37 degrees Celsius. Regression analysis was used to correlate changes in oxygen consumption and plasma catecholamine concentrations with core temperature.Results:All patients were vasoconstricted by the time core temperature reached 36 degrees Celsius. Further reduction in core temperature to 34–34.5 degrees Celsius did not increase oxygen consumption. Instead, oxygen consumption decreased linearly. Hypothermia also failed to increase plasma catecholamine concentrations.Conclusions:Even at core temperatures [nearly equal] 2 degrees Celsius below the vasoconstriction threshold, there was no evidence of nonshivering thermogenesis. This finding is surprising because all other major thermoregulatory responses have been detected during anesthesia. Infants and children thus appear similar to adults in being unable to increase metabolic rate in response to mild intraoperative hypothermia.

ISSN:0003-3022    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background:Epidural catheter movement has been noted with change of patient position and can result in inadequate anesthesia. This study was designed to measure movement and to develop a technique that minimizes catheter displacement.Methods:In 255 parturients requesting epidural anesthesia for labor or cesarean section, a multiorificed lumbar epidural catheter was inserted with the patient in the sitting flexed position. The distance to the epidural space, length of catheter inserted, and amount of catheter position change as the patient moved from the sitting flexed to sitting upright and then to the lateral decubitus position were measured before the catheter was secured to the skin. Adequacy of analgesia, the need for catheter manipulation, and whether the patient was considered obese were noted. Data were grouped according to body mass index (BMI): < 25, 25–30, and > 30 kg/m2.Results:The groups did not differ with respect to the length of catheter initially inserted or changes in catheter position between initial taping and removal. The distance to the epidural space differed significantly among the groups, increasing with greater BMI. Catheters frequently appeared to be drawn inward with position change from the sitting flexed to lateral decubitus position, with the greatest change seen in patients with BMI > 30. Only nine catheters were associated with inadequate analgesia, four of which were replaced. No analgesic failures occurred in the BMI > 30 group. In patients judged by the anesthesiologist to be obese or to have an obese back, BMI was greater, and the distance to the epidural space and the magnitude of catheter movement with position change were greater than in those who were not obese.Conclusions:Epidural catheters moved a clinically significant amount with reference to the skin in all BMI groups as patients changed position. If catheters had been secured to the skin before position change, many would have been pulled partially out of the epidural space. To minimize the risk of catheter displacement, particularly in obese patients, we recommend that multiorificed catheters be inserted at least 4 cm into the epidural space and that patients assume the sitting upright or lateral position before securing the catheter to the skin.

ISSN:0003-3022    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background:Cardiopulmonary bypass is associated with substantial release of catecholamines and cortisol for 12 or more h. A technique was assessed that may mitigate the responses with continuous 12‐h postoperative sedation using propofol.Methods:One hundred twenty‐one patients having primary elective cardiopulmonary bypass graft (CABG) surgery were enrolled in a double‐blind, randomized trial and anesthetized using a standardized sufentanil‐midazolam regimen. When arriving at the intensive care unit (ICU), patients were randomly assigned to either group SC (standard care), in which intermittent bolus administration of midazolam and morphine were given as required to keep patients comfortable; or group CP (continuous propofol), in which 12 h of continuous postoperative infusion of propofol was titrated to keep patients deeply sedated. Serial perioperative measurements of plasma and urine cortisol, epinephrine, norepinephrine, and dopamine were obtained; heart rate and blood pressure were recorded continuously, and medication use, including requirements for opioids and vasoactive drugs, was recorded. Repeated‐measures analysis was used to assess differences between study groups for plasma catecholamine and cortisol levels at each measurement time.Results:In the control state‐before the initiation of postoperative sedation in the ICU‐no significant differences between study groups were observed for urine or plasma catecholamine or cortisol concentrations. During the ICU study period, for the first 6–8 h, significant differences were found between study groups SC and CP in plasma cortisol (SC = 28 +/‐ 15 mg/dl; CP = 19 +/‐ 12 mg/dl; estimated mean difference [EMD] = 9 mg/dl; P = 0.0004), plasma epinephrine (SC = 132 +/‐ 120 micro gram/ml; CP = 77 +/‐ 122 micro gram/ml; EMD = 69 micro gram/ml; P = 0.009), urine cortisol (SC = 216 +/‐ 313 micro gram/ml; CP = 93 +/‐ 129 micro gram/ml; EMD = 127 micro gram/ml; P = 0.007), urine dopamine (SC = 85 +/‐ 48 micro gram; CP = 52 +/‐ 43 micro gram; EMD = 32 micro gram; P = 0.002), urine epinephrine (SC = 7 +/‐ 8 micro gram; CP = 4 +/‐ 5 micro gram; EMD = 3 micro gram; P = 0.009), and urine norepinephrine (SC = 24 +/‐ 14 mg; CP = 13 +/‐ 9 mg; EMD = 11 mg; P = 0.0004). Reductions in urine and plasma catecholamine and cortisol concentrations found for the CP group generally persisted during the 12‐h propofol infusion period and then rapidly returned toward control (SC group) values after propofol was discontinued. Postoperative opioid use was reduced in the CP group (SC = 97%; CP = 49%; P = 0.001), as was the incidence of (SC = 79%; CP = 60%; P = 0.04) and hypertension (SC = 58%; CP = 33%; P = 0.01), but the incidence of hypotension was increased (SC = 49%; CP = 81%; P = 0.001).Conclusions:Cardiopulmonary bypass graft surgery is associated with substantial increases in plasma and urine catecholamine and cortisol concentrations, which persist for 12 or more h. This hormonal response may be mitigated by a technique of intensive continuous 12‐h postoperative sedation with propofol, which is associated with a decrease in tachycardia and hypertension and an increase in hypotension.

ISSN:0003-3022    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background:Despite many advantages, spinal anesthesia often is followed by undesirable decreases in blood pressure, for which the ideal treatment remains controversial. Because spinal anesthesia‐induced sympathectomy and management with a pure alpha‐adrenergic agonist can separately lead to bradycardia, the authors hypothesized that epinephrine, a mixed alpha‐ and beta‐adrenergic agonist, would more effectively restore arterial blood pressure and cardiac output after spinal anesthesia than phenylephrine, a pure alpha‐adrenergic agonist.Methods:Using a prospective, double‐blind, randomized, cross‐over study design, 13 patients received sequential infusions of epinephrine and phenylephrine to manage hypotension after hyperbaric tetracaine (10 mg) spinal anesthesia. Blood pressure, heart rate, and stroke volume (measured by Doppler echocardiography using the transmitral time‐velocity integral) were recorded at baseline, 5 min after injection of tetracaine, and before and after management of hypotension with epinephrine and phenylephrine. Cardiac output was calculated by multiplying stroke volume x heart rate.Results:Five min after placement of a hyperbaric tetracaine spinal anesthesia, significant decrease in systolic (from 143 +/‐ 6 mmHg to 125 +/‐ 5 mmHg; P < 0.001), diastolic (from 81 +/‐ 3 to 71 +/‐ 3; P < 0.001), and mean (from 102 +/‐ 4 to 89 +/‐ 3; P < 0.001) arterial pressures occurred. Heart rate (75 +/‐ 4 beats/min to 76 +/‐ 4 beat/min; P = 0.9), stroke volume (115 +/‐ 17 to 113 +/‐ 13; P = 0.9), and cardiac output (8.0 +/‐ 1 l/m to 8.0 +/‐ 1 l/m; P = 0.8) did not change significantly after spinal anesthesia. Phenylephrine was effective at restoring systolic blood pressure after spinal anesthesia (120 +/‐ 6 mmHg to 144 +/‐ 5 mmHg; P <0.001) but was associated with a decrease in heart rate from 80 +/‐ 5 beats/min to 60 +/‐ 4 beats/min (P < 0.001) and in cardiac output from 8.6 +/‐ 0.7 l/m to 6.2 +/‐ 0.7 l/m (P < 0.003). Epinephrine was effective at restoring systolic blood pressure after spinal anesthesia (119 +/‐ 5 mmHg to 139 +/‐ 6 mmHg; P < 0.001) and was associated with an increase in stroke volume from 114 +/‐ 12 ml to 142 +/‐ 17 (P < 0.001) and cardiac output from 7.8 +/‐ 0.6 l/m to 10.8 +/‐ 1.1 l/m (P < 0.001).Conclusions:Epinephrine management of tetracaine spinal‐induced hypotension increases heart rate and cardiac output and restores systolic arterial pressure but does not restore mean and diastolic blood pressure. Phenylephrine management of tetracaine spinal‐induced hypotension decreases heart rate and cardiac output while restoring systolic, mean, and diastolic blood pressure.

ISSN:0003-3022    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background:Accuracy of jugular venous oxygen saturation (SjvO2) measurement depends on sampling of cerebral venous outflow blood not contaminated by systemic venous blood. The influence of the rate of blood withdrawal has not been determined.Methods:The authors examined the effect of withdrawing blood at different rates from jugular venous bulb catheters (JVBC) on SjvO2in 10 mechanically ventilated patients undergoing neurosurgical procedures. All patients received a standardized anesthetic consisting of propofol, fentanyl, vecuronium, and isoflurane. Routine monitors included electrocardiograph (ECG), invasive blood pressure, pulse oximetry, and a JVBC. During a period of stable anesthetic and surgical conditions, JVBC blood samples were drawn at 2, 4, and 10 ml/min using a calibrated pump (Harvard Pump model 900, Harvard Apparatus, South Natick, MA) during mild and moderate hypocapnia (arterial carbon dioxide tension [PaCO2], 26.0 +/‐ 0.5 and 33.0 +/‐ 0.5 mmHg).Results:Faster rates of withdrawal (10 and 4 ml/min vs. 2 ml/min) resulted in significantly higher SjvO2values at both levels of Pa sub CO2 (66.0 +/‐ 3% and 61.2 +/‐ 3% vs 56.9. +/‐ 3% at PaCO2= 26.0 0.5 mmHg, and 75.0 +/‐ 3% and 71.3 +/‐ 3% vs. 68.0 +/‐ 3% at PaCO2= 33.0 +/‐ 0.5 mmHg, respectively; P < 0.01).Conclusions:The authors conclude that the SjvO2values measured with intermittent sampling are affected by the rate of withdrawing blood from JVBC, probably as a result of extracranial contamination. They recommend blood samples should be drawn slowly.

ISSN:0003-3022    

出版商:OVID    

年代:1997

数据来源: OVID