Anesthesia and analgesia
-
Anesthesia and analgesia · Dec 2003
Randomized Controlled Trial Clinical TrialThe effects of desflurane and propofol on portosystemic pressure in patients with portal hypertension.
Physicians perform hepatic venous pressure measurements to guide medical therapy aimed at reducing portal hypertension. These measurements are frequently performed during general anesthesia. Since most general anesthetic drugs reduce liver blood flow, it is likely that hepatic venous pressures will be altered. We therefore examined the effects of two frequently used anesthetic drugs on hepatic venous pressure in a prospective randomized study to determine if pressure measurements taken during general anesthesia were similar to awake values. We studied 21 patients with hepatitis C, excluding patients with hepatofugal flow and portal vein thrombosis. All patients had free and wedged hepatic venous pressures measured awake with sedation and after anesthesia with either propofol or desflurane. Desflurane significantly increased free hepatic venous pressure (11.9 +/- 4.4 to 23.5 +/- 4.1 mm Hg; P < 0.05) and decreased hepatic venous pressure gradient (21.6 +/- 7.4 to 14.7 +/- 5.2 mm Hg; P < 0.05), whereas propofol did not change these variables. We conclude that desflurane, but not propofol, alters hepatic venous pressure measurements from the awake state, significantly increasing free hepatic venous pressure and decreasing the hepatic venous pressure gradient, an indirect measure of portosystemic pressure. Changes in the hepatic venous pressure gradient must be interpreted with caution during desflurane general anesthesia. ⋯ Desflurane reduces the blood pressure difference between the portal and systemic circulations. This can cause errors in assessment of the success of medical therapy of portal hypertension. Propofol has less effect on the difference between the portal and systemic circulation.
-
Anesthesia and analgesia · Dec 2003
Randomized Controlled Trial Clinical TrialAutomatic "respirator/weaning" with adaptive support ventilation: the effect on duration of endotracheal intubation and patient management.
Adaptive support ventilation (ASV) provides an automatic adaptation of the ventilator settings to patient's passive and active respiratory mechanics. In a randomized controlled study, we evaluated automatic respiratory weaning in ASV for early tracheal extubation after cardiac surgery. Eligible patients were assigned to either an ASV protocol or a standard one consisting of synchronized intermittent ventilation followed by pressure support. Eighteen patients completed the ASV protocol, and 16 completed the standard one. There were no differences between groups in perioperative characteristics, lengths of tracheal intubation and intensive care unit stay, and ventilatory variables, except less peak inspiratory pressure during the initial phase in ASV (17.5 +/- 0.8 versus 22.2 +/- 0.8 cm H(2)O; P < 0.01). ASV patients required fewer ventilatory settings manipulations (2.4 +/- 0.7 versus 4.0 +/- 0.8 manipulations per patient; P < 0.05) and endured less high-inspiratory pressure alarms (0.7 +/- 2.4 versus 2.9 +/- 3.0; P < 0.05). These results suggest that in this specific population of patients, automation of postoperative ventilation with ASV resulted in an outcome similar to the control group. The internal logic of the new device resulted in less manipulation of the setting and alarms that could simplify respiratory management. ⋯ Adaptive support ventilation (ASV), a ventilatory mode providing automatic adjustment of the settings was compared with standard management for rapid tracheal extubation after cardiac surgery. The two approaches were equal in terms of outcome. In ASV, we observed fewer ventilator settings manipulations and a smaller amount of alarms, suggesting that this automatic mode may simplify postoperative respiratory management without delaying extubation.
-
Anesthesia and analgesia · Dec 2003
Randomized Controlled Trial Clinical TrialRopivacaine and fentanyl concentrations in patient-controlled epidural analgesia during labor: a volume-range study.
We enrolled nulliparous women in induced labor in a randomized study to determine whether increasing the concentration of the solution used in a patient-controlled epidural analgesia (PCEA) device was required as labor progressed. Patients were assigned to 6 groups (n = 25 in each group), receiving ropivacaine/fentanyl in concentrations of either 0.1%/0.5 microg/mL or 0.2%/1 microg/mL via a PCEA pump. Three groups received boluses of 12, 16, or 20 mL dilute solution in early labor (uterine contractions every 3 min and 4-cm cervical dilation) then 6, 8, and 10 mL concentrated solution in late labor. Three other groups received boluses of 12, 16, or 20 mL dilute solution during both periods. The lockout interval was 25 min. The primary outcome was time until the first request for staff-administered analgesia supplement. Hourly assessments included pain scores on a visual analog scale (VAS) graded from 0 to 10, satisfaction scores, arterial blood pressure, motor block intensity, and the upper sensory level of epidural anesthesia. Patients, midwives, and the observer were unaware of study solutions and PCEA settings. The maximum pain score was defined as the highest score experienced by each patient during each period. Duration of analgesia was defined as the time from the start of each period to the first injection of rescue analgesia and was compared using a survival analysis. There were no differences among the groups with regard to demographic and obstetric variables, arterial blood pressure, motor block intensity, upper sensory level, or satisfaction scores. At least 75% of the women rated their satisfaction as either good or excellent during each period. During late labor, the maximum pain score was lower in the group receiving 20 mL dilute solution compared with the group receiving 6 mL concentrated solution. Maximum pain score was not significantly different between 20 mL dilute solution and 10 mL concentrated solution (difference between VAS values = -0.4; 95% confidence limits, -1.599 and 0.799; P = 0.5055). During late labor, the duration of analgesia was longer in groups receiving 20 mL dilute solution (99 +/- 4 min) (mean +/- SD) than in those receiving 12 mL (77 +/- 30 min) and 16 mL (80 +/- 23 min). Duration of analgesia did not differ between groups receiving 20 mL and 10 mL (92 +/- 23 min) or between groups receiving 12 mL and 6 mL (78 +/- 30 min) of each respective solution. Duration of analgesia was longer in the groups receiving 8 mL concentrated solution (94 +/- 16 min) than in those receiving 16 mL dilute solution. We concluded that 0.1%/0.5 microg/mL ropivacaine/fentanyl was effective throughout labor when 20 mL was injected with each PCEA demand. With 16 mg ropivacaine and 8 microg fentanyl, the duration of analgesia was prolonged by doubling the concentration when labor became active. When 12 mg ropivacaine and 6 microg fentanyl were injected at each demand, analgesia was less satisfactory and doubling the concentration was not clinically effective. These results suggest that the effectiveness of PCEA is dependent on drug mass rather than the volume or concentration administered with each successful pump demand. ⋯ There is no clinical reason for increasing the concentration of the patient-controlled epidural analgesia (PCEA) solution when labor becomes active provided that an effective dose is already being administered with each demand. The quality of PCEA depends on the drug mass given with each demand rather than the concentration of the pump solution.
-
Anesthesia and analgesia · Dec 2003
ReviewNew light on intravascular volume replacement regimens: what did we learn from the past three years?
Definition of the "ideal" intravascular fluid volume replacement strategy still remains a critical problem. This article analyzes studies on volume replacement by using a MEDLINE search of the past 3 years (from January 1, 2000, to December 12, 2002). Forty original studies in humans with a total of 2454 subjects were identified. Five studies were performed in volunteers (n = 113); the other 35 studies (n = 2341) were performed in a variety of patients (e.g., cardiac surgery, trauma patients, children, and intensive care unit patients). The influence of different volume replacement regimens on coagulation was one of the major topics of interest (16 studies with 1183 subjects), and other studies focused on metabolic state, alterations in macro- and microcirculation, volume distribution, and organ function (e.g., kidney function and splanchnic perfusion). Among all synthetic colloids, hydroxyethyl starch (HES) was the solution most often studied. Two new HES preparations have been approved (Hextend), a balanced hetastarch solution, and a new third-generation HES [130/0.4]). Only two studies used albumin, and no superiority of albumin was found over less expensive synthetic colloids. In almost all studies, the outcome either was no end-point or was not reported. Volume replacement has often been hitherto based on dogma and personal beliefs. Future well performed studies in this area will hopefully help to shed new light on the ideal volume replacement strategy. ⋯ By using a MEDLINE search covering the last 3 yr, the present knowledge on volume replacement regimens was analyzed. Forty studies in humans were identified. New hydroxyethyl starch preparations have shed light on this topic, whereas no additional data supporting the use of albumin have been presented.
-
Anesthesia and analgesia · Dec 2003
Case ReportsPreoperative fentanyl infusion with pharmacokinetic simulation for anesthetic and perioperative management of an opioid-tolerant patient.
For opioid-tolerant patients, conventional patient-controlled analgesia dosing may be ineffective. We present a cardiac surgery patient with a history of significant opioid tolerance and prior episodes of severe postoperative pain. Using the patient's response to a large-dose fentanyl infusion in conjunction with a pharmacokinetic simulation, effective intraoperative and postoperative fentanyl plasma concentrations were achieved. ⋯ A preinduction fentanyl infusion used in conjunction with pharmacokinetic simulation can be a useful tool for assessing individual limits of opioid tolerance, as well as determining an appropriate dose for acute pain management in opioid-tolerant patients.