Anesthesia and analgesia
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Anesthesia and analgesia · Jun 1998
Randomized Controlled Trial Comparative Study Clinical TrialAnalgesic and cognitive effects of intravenous ketamine-alfentanil combinations versus either drug alone after intradermal capsaicin in normal subjects.
Combinations of opioids and N-methyl-D-aspartate (NMDA) antagonists enhance acute antinociception and reduce opioid tolerance in some animal experiments but have received little rigorous study in humans. To quantitatively assess the nature of the interaction of these two classes of drugs in producing analgesia and cognitive impairment, we compared i.v. infusions of ketamine, alfentanil, and ketamine-alfentanil combinations in 12 normal volunteers after an intradermal injection of capsaicin. Drug doses for a 70-kg subject in this six-session, randomized, double-blind, cross-over study were: ketamine 20 mg, ketamine 5 mg, alfentanil 2 mg, alfentanil 0.5 mg, ketamine 10 mg + alfentanil 1 mg, and ketamine 2.5 mg + alfentanil 0.25 mg, given over 35 min. Outcome measures were background pain, area and magnitude of hyperalgesia to pinprick, and cognitive performance on the Digit Symbol Substitution Test and the Perception Speed Test. The results demonstrated simple additivity for the effects of ketamine and alfentanil on pain, pinprick hyperalgesia, and cognitive impairment. We conclude that, at least in this experimental pain model, there is no clear advantage or disadvantage of a ketamine-alfentanil combination over equianalgesic doses of either component. ⋯ In a double-blind, controlled trial, we administered doses of an opioid analgesic (alfentanil), an N-methyl-D-aspartate receptor antagonist (ketamine), or their combination to normal volunteers and found no advantage of the combination over a larger dose of either drug alone in relieving pain caused by painful chemical stimulation.
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Anesthesia and analgesia · Jun 1998
Randomized Controlled Trial Comparative Study Clinical TrialArterial oxygenation and shunt fraction during one-lung ventilation: a comparison of isoflurane and sevoflurane.
The aim of this study was to evaluate the effect of isoflurane and sevoflurane on oxygenation and shunt fraction during one-lung ventilation (OLV). Twenty patients undergoing lobectomy for lung cancer and scheduled for long-term OLV were enrolled in this study. Patients were allocated to treatment with either isoflurane or sevoflurane. Arterial oxygenation, shunt fraction, and hemodynamics were evaluated at the end of two-lung ventilation; 20 min after the initiation of OLV; 20 min after the application of 4-cm positive end-expiratory pressure (PEEP) to the dependent lung; 20 min after 8-cm PEEP; and 20 min after the conversion from OLV to two-lung ventilation. There was no significant difference between isoflurane and sevoflurane with regard to oxygenation, shunt fraction, or hemodynamics during OLV. PaO2 values after the application of 4-cm PEEP increased from 131.1 +/- 11.8 mm Hg to 190.6 +/- 22.9 mm Hg in the isoflurane group (P < 0.05) and from 127.2 +/- 14.3 mm Hg to 192.4 +/- 26.9 mm Hg in the sevoflurane group (P < 0.05). The selection of either isoflurane or sevoflurane for OLV was made without regard to arterial oxygenation and shunt fraction. PEEP application to the dependent lung is useful for improving oxygenation during OLV, but 8-cm PEEP had no added effect compared with 4-cm PEEP. ⋯ We compared the effects of isoflurane and sevoflurane on oxygenation, hemodynamics, and shunt fraction during one-lung ventilation in 20 patients undergoing scheduled lobectomy for lung cancer. There was no significant difference between isoflurane and sevoflurane with regard to oxygenation, shunt fraction, and hemodynamics during one-lung ventilation. The application of 4-cm positive end-expiratory pressure increased the partial pressure of arterial oxygen during one-lung ventilation.
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Anesthesia and analgesia · Jun 1998
Randomized Controlled Trial Clinical TrialExperimental pain in healthy human subjects: gender differences in nociception and in response to ibuprofen.
We used electrically induced pain in healthy young subjects to study gender differences in nociception and the analgesic efficacy of ibuprofen. Cutaneous stimulation of the earlobe allowed measurement of pain detection thresholds and maximal pain tolerance. Drug and placebo were each administered twice using a double-blind, randomized, multiple cross-over design. Male subjects had greater stimulus thresholds (lower nociception) compared with female subjects (18 +/- 0.3 vs 15 +/- 0.3 volts, mean +/- SEM; n = 10 in each group) and a greater pain tolerance (24 +/- 0.4 vs 21 +/- 0.4 volts). Response variability was also greater in the male subjects, yet only the men exhibited a statistically significant analgesic response to ibuprofen (deltavolts; ibuprofen versus placebo: 2.80 +/- 0.33 vs -0.18 +/- 0.34; P < 0.05, n = 10). None of these results could be attributed to pharmacokinetic differences. The finding that ibuprofen was less effective in women than in men has potential clinical significance, especially as a factor in the response variability to nonsteroidal antiinflammatory drugs. ⋯ In this study, we examined ibuprofen, a widely used nonsteroidal antiinflammatory drug, for its ability to reduce experimental pain. We found that it had such properties in healthy young male subjects but not in young female subjects. This is a paradox because many of the painful conditions for which nonsteroidal antiinflammatory drugs are used (e.g., rheumatoid arthritis) occur more often in women.
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Anesthesia and analgesia · Jun 1998
Randomized Controlled Trial Clinical TrialThe combination of epinephrine and isoproterenol as a simulated epidural test dose in isoflurane-anesthetized adults.
During isoflurane anesthesia, an epinephrine-containing test dose produces unreliable heart rate (HR) responses with a high incidence of hypertension, whereas an isoproterenol-containing test dose results in a high incidence of hypotension. We designed this study to determine whether different combination doses of epinephrine and isoproterenol produce reliable HR changes without overt fluctuations of systolic blood pressure (SBP). Seventy-five healthy patients were anesthetized with 1% end-tidal isoflurane after endotracheal intubation and randomized to one of five groups (n = 15 each) according to the combination dose given i.v.: epinephrine 15 microg, epinephrine 15 microg + isoproterenol 1.5 microg, epinephrine 7.5 microg + isoproterenol 3 microg, isoproterenol 3 microg, and saline. HR and SBP were measured at 20-s intervals for 4 min after injection. Based on the conventional HR criterion (positive if > or = 20 bpm increase), the epinephrine 15 microg + isoproterenol 1.5 microg, the epinephrine 7.5 microg + isoproterenol 3 microg, and the isoproterenol 3 microg groups yielded 100% sensitivities, specificities, and positive and negative predictive values, whereas all groups yielded 100% efficacy according to the modified HR criterion (positive if > or = 10 bpm increase). Four (27%) and three patients (20%) in the epinephrine 15 microg and the epinephrine 15 microg + isoproterenol 1.5 microg groups, respectively, developed systolic hypertension (SBP > or = 180 mm Hg), whereas four (27%) patients in the isoproterenol 3 microg group developed systolic hypotension (SBP < or = 80% of the preinjection value). We conclude that epinephrine 7.5 microg + isoproterenol 3 microg provides the most reliable HR changes with the least SBP fluctuations. ⋯ To test whether an epidural catheter may be in a blood vessel, various vasoactive drugs are administered during general anesthesia. The authors found that the combination of epinephrine 7.5 microg and isoproterenol 3 microg produced the most reliable heart rate changes with minimal blood pressure fluctuations.
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Anesthesia and analgesia · Jun 1998
Randomized Controlled Trial Comparative Study Clinical TrialThe effects of general versus epidural anesthesia for outpatient extracorporeal shock wave lithotripsy.
Although many anesthetic techniques are described for immersion extracorporeal shock wave lithotripsy (ESWL), regional and i.v. techniques are the most commonly reported. This randomized, prospective study compared general anesthesia (GA) and epidural anesthesia (EPID) with regard to effectiveness, side effects, induction time, and recovery in patients undergoing ESWL using an unmodified Dornier HM-3 lithotriptor. Twenty-six healthy outpatients were randomized to GA (propofol, N2O, laryngeal mask airway) or EPID (lidocaine 1.5% with epinephrine). Intraoperative and postoperative supplemental medications, side effects, and complications were noted. Induction times and times required to meet standard recovery criteria were compared between groups. Patients were surveyed regarding their satisfaction with anesthesia. All patients in the EPID group had effective blocks with a single catheter insertion and local anesthetic injection. In the GA group, the LMA was inserted successfully in all patients. Time from room entry to procedure start was significantly less in the GA group (23 +/- 11 vs 34 +/- 9 min; P < 0.05). Patients in the GA group were ready for discharge home earlier (127 +/- 59 vs 178 +/- 49 min; P < 0.05). Only three patients experienced nausea (one in the GA group, two in the EPID group). There were no differences in patient or urologist satisfaction with anesthesia. We conclude that GA is associated with a rapid recovery compared with EPID. ⋯ General anesthesia with propofol, nitrous oxide, and a laryngeal mask airway is comparable to epidural anesthesia with lidocaine for outpatient extracorporeal shock wave lithotripsy procedures. However, early recovery is more rapid after general anesthesia compared with epidural anesthesia.