Anesthesia and analgesia
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Anesthesia and analgesia · Dec 1999
Randomized Controlled Trial Clinical TrialThe effects of intradermal fentanyl and ketamine on capsaicin-induced secondary hyperalgesia and flare reaction.
In this study, we evaluated the effects of intradermal fentanyl and ketamine on capsaicin-induced hyperalgesia and axon-reflex flare. In addition, we obtained dose-response curves for possible local anesthetic effects. Saline (200 microL) and either fentanyl (1 microg or 10 microg in 200 microL) or ketamine (100 microg or 1000 microg in 200 microL) were injected simultaneously into the central volar forearm of 12 healthy volunteers. Nine minutes later, capsaicin (10 microg in 20 microL) was injected intracutaneously exactly between the two injection sites. Areas of touch-evoked allodynia and pinprick hyperalgesia, as well as intensity of pinprick hyperalgesia at the injection sites and axon-reflex flare, were evaluated. Fentanyl did not affect the area or intensity of secondary hyperalgesia. Only the larger concentration of fentanyl locally diminished axon-reflex flare without affecting mechanical detection thresholds. Inhibitory effects of ketamine on intensity of secondary hyperalgesia and axon reflex flare were observed only in the larger concentration. However, this concentration also clearly elevated mechanical detection thresholds. No inhibitory effects of ketamine in the smaller concentrations were observed. We conclude that fentanyl inhibits neuropeptide release on peripheral application without modulating secondary hyperalgesia. Ketamine failed to inhibit both secondary hyperalgesia and axon reflex flare as long as nonlocal anesthetic concentrations were applied. ⋯ We investigated the peripheral effects of fentanyl and ketamine on capsaicin-induced hyperalgesia and axon-reflex flare. In large concentrations, the opioid diminished axon-reflex flare without effects on secondary hyperalgesia. We found no evidence for the involvement of endogenous glutamate in secondary hyperalgesia or axon reflex flare.
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Anesthesia and analgesia · Dec 1999
Randomized Controlled Trial Clinical TrialThe effects of sodium nitroprusside-induced hypotension on splanchnic perfusion and hepatocellular integrity.
The purpose of our study was to investigate the effects of sodium nitroprusside-induced hypotension on splanchnic perfusion and hepatocellular integrity. Thirty patients undergoing radical prostatectomy were allocated randomly to a sodium nitroprusside (SNP) or control group (control). Regional pco2 was measured using gastric tonometry, and the regional to arterial difference in partial pressure of CO2 and intramucosal pH were calculated. The cytosolic liver enzyme alpha-glutathione S-transferase and standard liver enzyme markers (alanine aminotransferase, aspartate aminotransferase, and gamma-glutamyltransferase) were also measured. Mean arterial pressure in the SNP group was 50 mm Hg for 97 min during surgery. A significant increase from baseline in regional pco2 (from 40.0+/-4.2 mm Hg to 45.3+/-1.3 mm Hg) and regional to arterial difference in partial pressure of CO2 (from 4.1+/-1.1 mm Hg to 9.7+/-1.4 mm Hg) was seen at 90 min after skin incision only in the SNP group. Intramucosal pH decreased significantly from 7.40+/-0.02 to 7.35+/-0.03 during the same period in this group. Tonometric variables returned to baseline values within 2 h postoperatively. Alpha-glutathione S-transferase concentrations increased significantly in the SNP group from baseline to peak concentrations at the end of surgery (SNP: 9.93+/-4.94 microg/L; control: 5.85+/-1.86 microg/L). A return to baseline values was seen 24 h postoperatively. No significant changes in standard liver enzyme markers were seen throughout the study period. It is concluded, that splanchnic perfusion was transiently impaired during controlled hypotension. This is supported by significant changes in tonometric data. Increased serum levels of alpha-glutathione S-transferase may indicate a disturbance in hepatocellular integrity. ⋯ We studied gastric mucosal tonometry and the cytosolic liver enzyme alpha-glutathione S-transferase to evaluate the effects of controlled hypotension induced by sodium nitroprusside on splanchnic perfusion and hepatocellular integrity. Splanchnic perfusion decreased and alpha-glutathione S-transferase increased during and after a hypotensive period, but returned to baseline values within the first postoperative day, indicating a transient impairment of splanchnic perfusion and hepatocellular integrity.
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Anesthesia and analgesia · Dec 1999
Randomized Controlled Trial Clinical TrialOral clonidine premedication enhances postoperative analgesia by epidural morphine.
This study was designed to evaluate the effects of oral clonidine premedication on postoperative analgesia by epidural morphine in a prospective, randomized, double-blinded design. Sixty consenting patients, scheduled for total abdominal hysterectomy, were randomly assigned to one of three groups (n = 20 each); the clonidine-morphine group received oral clonidine 5 microg/kg 90 min before arriving in the operating room and epidural morphine 2 mg before induction of general anesthesia, the clonidine-placebo group received oral clonidine 5 microg/kg and no epidural morphine, and the placebo-morphine group received no clonidine and epidural morphine 2 mg. An epidural catheter was placed at the L1-2 or L2-3 interspace, and 1.5% lidocaine was used for surgical anesthesia in all patients. General anesthesia was then induced with propofol, and maintained with a continuous infusion of propofol and 67% nitrous oxide in oxygen during surgery. Four patients were subsequently withdrawn from the study. After surgery, patient-controlled analgesia using IV morphine was used to assess analgesic requirement. Morphine consumptions determined every 6 h after surgery in the clonidine-morphine and placebo-morphine groups were significantly less than the clonidine-placebo group until 12 h after surgery, whereas those of the clonidine-morphine group were significantly less than the placebo-morphine group from 13 to 42 h after surgery. Visual analog (pain) scale (VAS) scores in the clonidine-morphine group were significantly lower than the placebo-morphine group at 48 h at rest, and at 1, 24, 36, and 48 h with movement. Similarly, VAS scores in the clonidine-morphine group were significantly lower than the clonidine-placebo group at 1 and 6 h both at rest and with movement, whereas VAS scores in the clonidine-placebo group were significantly lower than the placebo-morphine group at 24, 36, and 48 h at rest and with movement. The incidence of nausea and pruritus was similar between groups. We conclude that the combination of oral clonidine and epidural morphine produces more potent and longer lasting postoperative analgesia than either drug alone without increasing the incidence of adverse effects after major gynecologic surgeries. ⋯ A small dose of epidural morphine is often used for postoperative analgesia. We found that oral clonidine premedication 5 microg/kg improves the analgesic efficacy of epidural morphine without increasing the incidence of adverse side effects.
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Anesthesia and analgesia · Dec 1999
Randomized Controlled Trial Comparative Study Clinical TrialQuantitative comparison of leakage under the tourniquet in forearm versus conventional intravenous regional anesthesia.
We compared the quantitative leakage between forearm and conventional IV regional anesthesia (IVRA). Forearm IVRA remains unpopular because of the theoretical risk of local anesthetic leakage through the interosseous vessels. IVRA was simulated on the forearm or arm during two separate, randomized sessions using a double tourniquet in 14 volunteers. A radiolabeled substance, DISIDA (99m Tc-disofenin) with a structure similar to lidocaine, was injected instead of local anesthetic. Volumes of 0.4 mL/kg (maximum 25 mL), were used for forearm IVRA and 0.6 mL/kg (maximum 45 mL) for conventional IVRA. A gamma camera recorded radioactivity levels in the limb distal to the tourniquet every 30 s while the tourniquet was inflated (25 min) and for 20 min postdeflation. The leakage of radiolabeled substance during inflation was similar in both groups, 6%+/-12% (mean +/- SD) from the forearm and 10%+/-20% from the upper arm. After deflation, mean loss of radioactivity was higher in conventional IVRA, 70%+/-7% vs 57%+/-11% and 82%+/-5% vs 69%+/-11% at 3 and 20 min, respectively (P < 0.001). We conclude that forearm IVRA results in tourniquet leakage comparable to conventional IVRA and is potentially safer because the required dose of local anesthetic is smaller. ⋯ Using a tourniquet on the forearm for IV regional anesthesia does not increase the risk of drug leakage. This is potentially a safer technique compared with conventional IV regional anesthesia because a much smaller dose of local anesthetic is required.
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Anesthesia and analgesia · Dec 1999
Comparative Study Clinical TrialThe hemodynamic effects of anesthetic induction in vascular surgical patients chronically treated with angiotensin II receptor antagonists.
The use of angiotensin II receptor subtype-1 antagonists (ARA), recently introduced as antihypertensive drugs, is becoming more prevalent. We studied the prevalence and severity of hypotension after the induction of general anesthesia in 12 patients treated with ARA until the morning of surgery. The hemodynamic response to induction was compared with that of patients treated with beta-adrenergic blockers (BB) and/or calcium channel blockers (CB) (BB/CB group, n = 45) and angiotensin-converting enzyme inhibitors (ACEI) (ACEI group, n = 27). A standardized anesthesia induction protocol was followed for all patients. Hypotension occurred significantly (p < or = 0.05) more often in ARA-treated patients (12 of 12) compared with BB/CB-treated patients (27 of 45) or with ACEI-treated patients (18 of 27). There was a significantly (P < or = 0.001) increased ephedrine requirement in the ARA group (21+/-3 mg) compared with the BB/CB group (10+/-6 mg) or the ACEI group (7+/-4 mg). Hypotension refractory to repeated ephedrine or phenylephrine administration occurred significantly (P < or = 0.05) more in the ARA group (4 of 12) compared with the BB/CB group (0 of 45) or the ACEI group (1 of 27), but it was treated successfully by using a vasopressin system agonist. Treatment with angiotensin II antagonism until the day of surgery is associated with severe hypotension after the induction of anesthesia, which, in some cases, can only be treated with an agonist of the vasopressin system. ⋯ Hypotensive episodes occur more frequently after anesthetic induction in patients receiving Angiotensin II receptor subtype-1 antagonists under anesthesia than with other hypotensive drugs. They are less responsive to the vasopressors ephedrine and phenylephrine. The use of a vasopressin system agonist was effective in restoring blood pressure when hypotension was refractory to conventional therapy.