Anesthesia and analgesia
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Anesthesia and analgesia · Oct 1998
Randomized Controlled Trial Comparative Study Clinical TrialComparison of patient-controlled epidural analgesia with and without background infusion after gastrectomy.
To assess the analgesic efficacy and side effects of concurrent infusion in patient-controlled epidural analgesia (PCEA) after upper abdominal surgery, 40 patients undergoing elective gastrectomy under general anesthesia were allocated to two groups in this randomized, double-blind study: one received a 2.5-mL incremental bolus in a solution of 0.2% bupivacaine and 10 microg/mL fentanyl, and the other received the same bolus dose plus a 2.5-mL/h infusion of the same solution. The number of demands was smaller (P < 0.001) in the PCEA plus infusion group than in the PCEA alone group during the 48-h postoperative period. The average hourly fentanyl and bupivacaine doses were larger (P < 0.0001) in the PCEA plus infusion group than in the PCEA alone group. Visual analog scale pain scores on coughing in the PCEA plus infusion group were lower than in the PCEA alone group (P < 0.05). There was a greater incidence of pruritus in the PCEA plus infusion group (P < 0.05), but no serious side effects were observed in either group. In conclusion, a background infusion in PCEA with a mixture of fentanyl and bupivacaine decreases the incidence of postoperative pain and reduces the degree of pain associated with coughing without serious side effects after gastrectomy. ⋯ A background infusion in patient-controlled epidural analgesia with a mixture of fentanyl and bupivacaine decreased the incidence of postoperative pain and reduced the degree of the pain associated with coughing without serious side effects in this randomized, double-blind study after gastrectomy.
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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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Anesthesia and analgesia · Oct 1998
The analgesic potency of dexmedetomidine is enhanced after nerve injury: a possible role for peripheral alpha2-adrenoceptors.
This study investigated the analgesic potency and site of action of systemic dexmedetomidine, a selective alpha2-adrenoceptor (alpha2AR) agonist, in normal and neuropathic rats. Ligation of the L5-6 spinal nerves produced a chronic mechanical and thermal neuropathic hyperalgesia in rats. von Frey fibers and a thermoelectric Peltier device were used to measure mechanical and heat withdrawal thresholds over the hindpaw. Systemic dexmedetomidine dose-dependently increased the mechanical and thermal thresholds in the control animals (50% effective dose [ED50] 144 and 180 microg/kg intraperitoneally [i.p.], respectively). Neuropathic animals responded to much smaller doses of dexmedetomidine with mechanical and thermal ED50 values of 52 and 29 microg/kg i.p., respectively. There was no difference between the control and neuropathic animals with respect to dexmedetomidine-evoked sedation, as determined by decreased grid crossings in an open-field activity chamber (ED50 12 and 9 microg/kg i.p., respectively). Atipamezole, a selective alpha2AR antagonist, blocked the analgesic and sedative actions of dexmedetomidine inboth the neuropathic and control animals. However, L-659,066, a peripherally restricted alpha2AR antagonist, could only block the analgesic actions of dexmedetomidine in the neuropathic rats, with no effect in control animals. In conclusion, nerve injury enhanced the analgesic but not the sedative potency of systemic dexmedetomidine and may have shifted the site of alpha2 analgesic action to outside the blood-brain barrier. ⋯ We tested the analgesic efficacy of the alpha2 agonist dexmedetomidine in normal and nerve-injured rats. The analgesic potency of dexmedetomidine was enhanced after nerve injury with a site of action outside the central nervous system. Peripherally restricted alpha2 agonists may be useful in the management of neuropathic pain.
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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.
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Anesthesia and analgesia · Oct 1998
Uncompensated blood loss is not tolerated during acute normovolemic hemodilution in anesthetized pigs.
Clinically, hemodilution to a hematocrit of 9% has been studied, but the effects of hypovolemia during this degree of hemodilution have not been elucidated. We studied the response to blood loss during extreme hemodilution and evaluated indicators of hypovolemia. Systemic and myocardial hemodynamics, oxygen transport, and blood lactate concentrations were measured in 12 anesthetized pigs exposed to a graded blood loss of 10, 20, 30, and 40 mL/kg. Six animals were hemodiluted (hematocrit 10.8% +/- 1.4%, mean +/- SD), and six animals served as controls (hematocrit 34.6% +/- 1.5%). Hemodilution decreased systemic oxygen delivery to 9.5 +/- 0.6 mL x kg(-1) x min(-1) (controls 21.7 +/- 3.9 mL x kg(-1) x min(-1)) (P < 0.01) despite a 31% increase in cardiac output. Systemic oxygen uptake was unchanged. Arterial lactate increased to 3.3 +/- 1.1 mM/L (controls 1.6 +/- 0.6 mM/L) (P < 0.05), and mixed venous oxygen saturation (SvO2) decreased to 38.2% + 4.8% (controls 68.6% +/- 2.9%) (P < 0.01). At a blood loss of 10 mL/kg, cardiac output continued to be greater in the hemodiluted animals (P < 0.01). Arterial blood pressure decreased to 61 +/- 8 mmHg (controls 84 +/- 18 mm Hg) (P < 0.05), whereas heart rate was unchanged. Systemic oxygen delivery decreased to 8.8 +/- 1.2 mL x kg(-1) x min(-1) (controls 14.1 +/- 2.5 mL x kg(-1) x min(-1)) (P < 0.01). Systemic oxygen uptake was maintained by a further increase in oxygen extraction, and SvO2 decreased to 29.7% +/- 7.3%, compared with 55.3% +/- 9.0% in controls (P < 0.01). Arterial lactate increased to 4.9 +/- 1.4 mM/L (controls 1.8 +/- 0.8 mM/L) (P < 0.01). Myocardial oxygen delivery and lactate uptake were unchanged. When the blood loss equaled 30 mL/kg, myocardial lactate production occurred, and two hemodiluted animals died of circulatory failure. Central venous and capillary wedge pressures changed minimally during the blood loss and did not differ between groups. We conclude that a decrease in arterial blood pressure and SvO2 were early signs of hypovolemia during hemodilution, whereas central venous pressure and pulmonary capillary wedge pressure were insensitive indicators. ⋯ Anesthetized pigs with extremely low hemoglobin levels (one third of normal) showed poor tolerance to blood loss >10 mL/kg. A decreasing arterial blood pressure, a decreasing oxygen saturation in the venous blood, and an increase in arterial blood lactate concentration were useful indicators of blood loss.