Anesthesia and analgesia
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Anesthesia and analgesia · Jan 1999
Comparative Study Clinical TrialEvaluation of a new operating room ventilator with volume-controlled ventilation: the Ohmeda 7900.
Changes in fresh gas flow (FGF) during volume-controlled ventilation with the circle system have clinically important effects on the ventilatory variables of children. Current operating room ventilators allow a portion of the FGF to be added to the delivered tidal volume. The Ohmeda 7900 (Madison, WI) ventilator was designed to compensate for changes in FGF. We compared this ventilator with a standard ventilator, the Ohmeda 7000. Twenty patients (13-56 kg) undergoing dental or lower extremity surgery were studied. A side-by-side comparison of the two ventilators was performed using each patient as his or her own control. Beginning with the 7900 ventilator, FGF was set at 3.0 L/min, and the inspiratory to expiratory ratio was set at 1:2. Respiratory rate and tidal volume were adjusted to achieve an ETCO2 of 30-40 mm Hg. After a 10-min period of stabilization, inspired minute ventilation (VI), expired minute ventilation (VE), and ETCO2 were measured. FGF was then increased to 6.0 L/min, and the measurements were repeated after 10 min; FGF was then decreased to 1.5 L/min, and measurements were repeated after 10 min. The patient was then ventilated with an Ohmeda 7000 ventilator, and the sequence was repeated. The Ohmeda 7000 ventilator demonstrated significant changes in VI, VE, plateau pressure, and ETCO2, with changes in FGF (P = 0.0039-0.0001). The Ohmeda 7900 ventilator demonstrated compensation for changes in FGF; there were no significant changes in VI, VE, and ETCO2. We conclude that the Ohmeda 7900 ventilator provides stable ventilatory variables regardless of alterations in FGF (1.5-6.0 L/min). ⋯ In this study, we compared the effects of changing fresh gas flow on volume-controlled ventilation using two operating room ventilators (Ohmeda 7000 and Ohmeda 7900). The Ohmeda 7900, but not the Ohmeda 7000, provided stable ventilatory variables with fresh gas flows between 1.5 and 6.0 L/min.
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Anesthesia and analgesia · Jan 1999
Clinical TrialCapnography monitoring during neurosurgery: reliability in relation to various intraoperative positions.
In neurosurgery, estimation of PaCO2 from PETCO2 has been questioned. The aim of this study was to reevaluate the accuracy of PETCO2 in estimating PaCO2 during neurosurgical procedures lasting >3 h and to measure the effect of surgical positioning on arterial to end-tidal CO2 gradient (P[a-ET]CO2) over time. One hundred four neurosurgical patients classified into four groups (supine [SP], lateral [LT], prone [PR], sitting [ST]) were included in a prospective study. PaCO2, PETCO2, and P(a-ET)CO2 were measured after induction of anesthesia (T0), after positioning (T1), each following hour (T2, T3, T4), and at the end of the procedure after return to the SP position (T5). Data are expressed as the mean +/- SD, and statistical analysis used linear regression, the Bland-Altman method, and analysis of variance. The mean durations of positioning and surgery were 4.1+/-1 h and 3.7+/-1.3 h, respectively. We performed 624 simultaneous measurements of PaCO2 (33+/-5 mm Hg) and PETCO2 (27+/-4 mm Hg), leading to a mean P(a-ET)CO2 of 6+/-4 mm Hg. P(a-ET)CO2 of the LT group (7+/-3 mm Hg) was larger (compared with the SP, PR, and ST groups) because of a lower PETCO2 (26+/-4 mm Hg). Negative P(a-ET)CO2 (PETCO2 > PaCO2) occurred 22 times, only in the SP (n = 9) and ST groups (n = 13). Changes in opposite directions of PETCO2 and PaCO2 between two successive measurements were found in 26% of the cases. Correlation coefficients in the four groups (PaCO2 versus PETCO2) were not in good agreement (0.46 to 0.62; P < 0.001). The mean bias was between 5 and 7 mm Hg. The superior (13-15 mm Hg) and inferior (-5 to 0 mm Hg) limits of agreement were too large to expect PETCO2 to replace PaCO2. In conclusion, during neurosurgical procedures of >3 h, capnography should be performed with regular analysis of arterial blood gases for optimal ventilator adjustment. ⋯ This study, which aimed to reevaluate the ability of PETCO2 to estimate PaCO2 during neurosurgical procedures according to surgical position, indicates that PETCO2 cannot replace PaCO2 for the following reasons: scattering of individual values; occurrence of negative arterial to end-tidal CO2 gradient (P[a-ET]CO2; PaCO2 and PETCO2 variations in opposite directions; large changes in P(a-ET)CO2 between two samples; and instability of P(a-ET)CO2 over time.
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Anesthesia and analgesia · Jan 1999
Clinical TrialDevelopment and psychometric testing of a quality of recovery score after general anesthesia and surgery in adults.
A variety of methods have been used to quantify aspects of recovery after anesthesia. Most are narrowly focused, are not patient-rated, and have not been validated. We therefore set out to develop a patient-rated quality of recovery score. We constructed a 61-item questionnaire that asked individuals (patients and relatives, medical and nursing staff; total n = 136) to rate various postoperative items describing features a patient may experience postoperatively. The most highly ranked items were included in a final nine-point index score, which we called the "QoR Score." We then studied two cohorts of surgical patients (n = 449). There was good convergent validity between the QoR Score and the visual analog scale score (rho = 0.55, P < 0.0001). Discriminant construct validity was supported by comparing resultant QoR Scores in patients undergoing day-stay, minor, and major surgery (P = 0.008), as well as a negative correlation with duration of hospital stay (rho = -0.20, P < 0.0001), and, using multivariate regression, demonstrating a significant negative relationship between QoR Score and female gender (P = 0.048) and older age (P = 0.041). There was also good interrater agreement (rho = 0.55, P < 0.0001), test-retest reliability (median rho = 0.61, P < 0.0001), and internal consistency (alpha = 0.57 and 0.90, P < 0.0001). There was a significant difference between the groups of patients recovering from major and minor surgery (P < 0.001). This study demonstrates that the QoR Score has good validity, reliability, and clinical acceptability in patients undergoing many types of surgery. ⋯ We set out to develop a patient-rated quality of recovery score (QoR) that could be used both as a measure of outcome in perioperative trials and for clinical audit. We first surveyed patients and staff to identify important aspects of recovery, then developed a nine-point QoR Score. This was then compared with other measures of postoperative outcome. We found that the QoR Score is a useful measure of recovery after anesthesia and surgery.
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Anesthesia and analgesia · Jan 1999
Clinical TrialThe intensity of preoperative pain is directly correlated with the amount of morphine needed for postoperative analgesia.
The aim of this study was to examine whether severity of preoperative pain intensity is related to postoperative pain and morphine consumption. Sixty consecutive patients scheduled for total hip surgery during intrathecal anesthesia were studied. Preoperative visual analog scale (VAS) scores and analgesic intake was assessed 1 day before surgery. Three groups of patients were identified: those with mild pain (n = 12, VAS score 0-4), moderate pain (n = 18, VAS score 4-7), and severe pain (n = 28, VAS score 7-10). Postoperative pain scores were recorded in the first 24 h, as was the amount of morphine delivered by the patient-controlled analgesia pump. There were no differences among the groups in VAS scores at any time. Severe preoperative pain levels correlated with significantly greater postoperative morphine intake. The mean morphine intake during the first 24 h postoperatively was 19.2 mg in the mild pain group, 21.2 mg in the moderate pain group, and 29.5 mg in the severe pain group (P < 0.05 compared with both other groups). We conclude that patients with severe preoperative pain self-medicate to achieve postoperative pain scores equivalent to those of patients with mild and moderate pain and require a greater postoperative morphine intake for adequate analgesia than patients with mild or moderate preoperative pain. ⋯ In this study, we showed that severity of preoperative pain intensity relates to postoperative pain levels and morphine consumption. Patients scheduled for total hip surgery with severe preoperative pain require more postoperative morphine in the first 24 h.
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Anesthesia and analgesia · Jan 1999
Comparative StudyA comparison of the effects of propofol and sevoflurane on the systemic toxicity of intravenous bupivacaine in rats.
We compared the effects of propofol and sevoflurane on bupivacaine-induced central nervous system and cardiovascular toxicity in rats. Thirty-four male Sprague-Dawley rats were anesthetized with 70% N2O/30% O2 plus the 50% effective dose (ED50) of propofol (propofol group, n = 12); 70% N2O/30% O2 plus ED50 of sevoflurane (sevoflurane group, n = 11); or 70% N2O/30% O2 (control group, n = 11). Bupivacaine was infused at a constant rate of 2 mg x kg(-1) x min(-1) while electrocardiogram, electroencephalogram, and invasive arterial pressure were continuously monitored. The cumulative doses of bupivacaine that induced dysrhythmias, seizures, and 50% reduction of heart rate were larger in the propofol and sevoflurane groups than in the control group. The cumulative dose of bupivacaine that induced a 50% reduction in the mean arterial blood pressure was larger in the propofol group than in the sevoflurane and control groups. The margin of safety, assessed by the time between the onset of dysrhythmias and 50% reduction of mean arterial blood pressure, was wider in the propofol group than in the sevoflurane group. We conclude that propofol and sevoflurane attenuate bupivacaine-induced dysrhythmias and seizures and that propofol has a wider margin of safety than sevoflurane. ⋯ In anesthetized patients, dysrhythmias may be the only warning sign of intravascular injection of bupivacaine. Because propofol has a wider margin of safety than sevoflurane, life-threatening cardiovascular depression may be prevented by stopping the injection of bupivacaine at the onset of dysrhythmias during propofol anesthesia.