Anesthesia and analgesia
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Anesthesia and analgesia · Oct 1998
Randomized Controlled Trial Multicenter Study Clinical TrialPostoperative analgesic effects of three demand-dose sizes of fentanyl administered by patient-controlled analgesia.
Many studies have demonstrated the postoperative analgesic efficacy of fentanyl delivered i.v. by patient-controlled analgesia (PCA) devices at demand doses ranging from 10 to 50 microg, but none has sought to define the optimal fentanyl PCA dose. In this randomized, double-blind, multicenter study, we compared the safety and efficacy of three administered demand-dose sizes of fentanyl (20, 40, and 60 microg) in 150 patients after major surgery. Efficacy was dose-dependent; positive response rates (i.e., a global assessment score of "very good" or "excellent" and the absence of severe opioid adverse effects) were 42%, 52%, and 68% for the 20, 40, and 60 microg demand-dose groups, respectively, and were significantly higher in the 60 microg demand-dose group. The number of doses administered and missed attempts were significantly smaller in the 40 and 60 microg demand-dose groups compared with the 20 microg demand-dose group. This suggests that the 20 microg demand dose provided inadequate pain relief. Adverse respiratory events were more frequent and mean respiratory rates were significantly slower with the 60 microg demand dose, compared with the 20 or 40 microg demand doses. These results indicate that, of these three doses, the 40 microg demand dose was optimal for fentanyl PCA management of moderate to severe pain after major surgery. ⋯ The postoperative analgesic efficacy of fentanyl delivered i.v. by patient-controlled analgesia devices has been demonstrated for demand doses ranging from 10 to 50 microg, but the optimal fentanyl dose remains unknown. In this randomized, double-blind study, we compared three demand dose sizes of fentanyl (20, 40, and 60 microg) and found that the 40 microg demand dose was the most appropriate for fentanyl patient-controlled analgesia management of postoperative pain.
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Anesthesia and analgesia · Oct 1998
Randomized Controlled Trial Clinical TrialThe effect of the interaction of propofol and alfentanil on recall, loss of consciousness, and the Bispectral Index.
The Bispectral Index (BIS) correlates well with the level of consciousness with single anesthetic drugs. We studied the effect of the interaction of propofol with alfentanil on propofol concentration and BIS associated with 50% probability of loss of consciousness and lack of recall (Cp50 and BIS50, respectively). We studied 40 consenting volunteers at two institutions who were randomly assigned to receive stepped increases of propofol (10 subjects at each site), propofol plus alfentanil 50 ng/mL (10 subjects at Emory site), or propofol plus alfentanil 100 ng/mL (10 subjects at Duke site) by using a target-controlled infusion device. Measures of sedation, BIS, deltaBIS (absolute change of BIS after a painful stimulus), memory, and drug concentration were obtained at each target drug concentration. The relation among BIS, measured drug concentration, sedation score, and presence or absence of recall was determined by linear and logistic regression for different drug regimens, and the prediction probability (Pk) was calculated. The addition of alfentanil in increasing doses did not significantly affect the BIS50 and propofol Cp50 values for loss of consciousness and lack of recall. DeltaBIS was significantly decreased by both an increase in the concentration of propofol and the presence of alfentanil. The Pk for BIS was >0.93 with all drug regimens, better than those of the target and measured propofol concentrations. We conclude that BIS correlated well with the hypnotic component of anesthesia independent of the presence of an opioid. Moreover, the level of consciousness, and, therefore, the BIS index, is affected by a painful stimulus, and this response is ablated either by opioids or increasing propofol concentration. ⋯ In volunteers, the sedation and changes in memory function produced by propofol correlated well with changes in the Bispectral Index. This relationship was not altered by the addition of an analgesic (alfentanil). However, in moderately sedated patients who received a painful stimulus, the Bispectral Index increased, but this response was blocked by the analgesic or increasing propofol concentrations.
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Discharge time (total recovery time) is one determinant of the overall cost of outpatient surgery. We performed this study to determine what factors affect discharge time. Details regarding patients, anesthesia, surgery, and recovery were recorded prospectively for 1088 adult patients undergoing ambulatory surgery over an 8-mo period. The contribution of factors to variability in the discharge time was assessed by using multivariate linear regression analysis. In the last 4 mo of the study, nurses indicated the causes of discharge delays > or =50 min in Phase 1 or > or =70 min in Phase 2 recovery. When all anesthetic techniques were included, anesthetic technique was the most important determinant of discharge time (R2 = 0.10-0.15; P = 0.001), followed by the Phase 2 nurse. After general anesthesia, the Phase 2 nurse was the most important factor (R2 = 0.13; P = 0.01-0.001). In women, the choice of general anesthetic drugs was significant (R2 = 0.04; P = 0.002). The three most common medical causes of delay were pain, drowsiness, and nausea/vomiting. System factors were the foremost cause of Phase 2 delays (41%), with lack of immediate availability of an escort accounting for 53% of system-related delays. We conclude that efforts to shorten discharge time would best be directed at improving nursing efficiency; ensuring availability of an escort for the patient; and preventing postoperative pain, drowsiness, and emetic symptoms. The selection of anesthetic technique and anesthetic drug seems to be of selective importance in determining discharge time depending on patient gender and type of surgery. ⋯ The relative importance of anesthetic and nonanesthetic factors were evaluated as determinants of discharge time after ambulatory surgery. Postoperative nursing care was the single most important factor after general anesthesia; anesthetic drugs, anesthetic technique, and prevention of pain and emetic symptoms were of selective importance depending on patient gender and type of surgery.
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Previous studies of gastric contents in children presenting for surgery specifically excluded those with gastrointestinal disorders. Because these children often need sedation or anesthesia for procedures such as upper endoscopy, it is important to determine the gastric fluid volume and pH in this group to better characterize their risk of aspiration. We therefore analyzed the gastric fluid volume and pH of children with a variety of gastrointestinal symptoms presenting for upper endoscopy. After obtaining institutional review board approval, the stomach contents of 248 children (aged 2 mo to 18 yr) presenting for upper endoscopy were prospectively measured under direct endoscopic vision. Children were fasted for both solids and liquids for at least 6 h (<6 mo) or 8 h (>6 mo). Gastric fluid pH was measured using pH paper. Children received either deep sedation or general anesthesia and were grouped according to their presenting diagnosis. Results were analyzed by using analysis of variance, Kruskal-Wallis, and correlation (P value < 0.05). The mean gastric fluid volume was 0.35 +/- 0.45 mL/kg (range 0-3.14 mL/kg), and the mean gastric fluid pH was 1.37 +/- 1.6 (range 1-7). Of the children, 33% had gastric fluid volumes >0.4 mL/kg, 87% had gastric fluid pH <2.5, and 30% had gastric fluid volume >0.4 mL/kg and pH <2.5. Children with the presenting complaint of abdominal pain had the largest gastric fluid volumes. These data are not appreciably different from historical controls (healthy children fasted for an equivalent period of time who did not have gastrointestinal symptoms). ⋯ When fasted for at least 6-8 h, children with a history of gastrointestinal symptoms presenting for upper endoscopy did not have gastric contents with increased volume and acidity compared with previously published groups of children without gastric symptoms who were fasted the same length of time. These results do not support the argument that children with gastrointestinal symptoms pose an increased anesthetic risk for aspiration.
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Anesthesia and analgesia · Oct 1998
The effects of the lateral position on cardiopulmonary function during laparoscopic urological surgery.
Laparoscopic urological surgery is usually performed transperitoneally with retroperitoneal insufflation of carbon dioxide (CO2) in the lateral position. We studied whether a difference in the side of lateral position affected hemodynamic and pulmonary functions during pneumoperitoneum. Fifteen patients (eight in the right and seven in the left lateral position) undergoing elective laparoscopic urological surgery were studied under general anesthesia. Hemodynamic variables and blood gas data were recorded. Before insufflation, mean arterial pressure (MAP), mean pulmonary arterial pressure (MPAP), central venous pressure (CVP), and pulmonary capillary wedge pressure (PCWP) in the right lateral position were higher than those in the left lateral position. Pneumoperitoneum increased MAP, MPAP, CVP, PCWP, and cardiac index but decreased systemic vascular resistance in the right lateral position. Similar changes occurred during pneumoperitoneum in the left lateral position, but the changes were less than those in the right lateral position. The respiratory index (PaO2/PAO2), intrapulmonary shunt, and SpO2 did not change during pneumoperitoneum in either lateral position. Changing the side of the lateral position affected hemodynamic function but did not affect pulmonary oxygenation during pneumoperitoneum. ⋯ The right and left lateral positions produced different hemodynamic changes during laparoscopic urological surgery. The increases in preload and cardiac index and the decrease in systemic vascular resistance were greater in the right than in the left lateral position. Respiratory changes were not affected differently between the right and left lateral positions.