Anesthesia and analgesia
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Anesthesia and analgesia · Feb 1999
Comparative StudyAn examination of the interactions between the antinociceptive effects of morphine and various mu-opioids: the role of intrinsic efficacy and stimulus intensity.
We examined the effects of several opioids that vary in intrinsic efficacy at the mu-opioid receptor alone and in combination with morphine in a rat warm water tail withdrawal procedure using 50 degrees C and 52 degrees C water (i.e., low- and high-stimulus intensities). Morphine, levorphanol, dezocine, and buprenorphine produced dose-dependent increases in antinociception using both stimulus intensities. Butorphanol produced maximal levels of antinociception at the low, but not at the high, stimulus intensity, whereas nalbuphine failed to produce antinociception at either stimulus intensity. For cases in which butorphanol and nalbuphine failed to produce antinociception alone, these opioids dose-dependently antagonized the effects of morphine. When levorphanol, dezocine, and buprenorphine were combined with morphine, there was a dose-dependent enhancement of morphine's effects. Similar effects were obtained at the low-stimulus intensity when butorphanol was administered with morphine. In most cases, the effects of these combinations could be predicted by summating the effects of the drugs when administered alone. These results indicate that the level of antinociception produced by an opioid is dependent on the intrinsic efficacy of the drug and the stimulus intensity. Furthermore, the level of antinociception produced by the opioid, not necessarily the opioids' intrinsic efficacy, determines the type of interaction among opioids. ⋯ Compared with high-efficacy opioids, lower efficacy opioids produce lower levels of pain relief, especially in situations of moderate to severe pain. When opioids are given in combination, the effects can only be predicted on the basis of the antinociception obtained when the drugs are administered alone.
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Anesthesia and analgesia · Feb 1999
Comparative StudyThe effects of clonidine and dexmedetomidine on human neutrophil functions.
Neutrophil functions are inhibited by various anesthetics. Clonidine and dexmedetomidine, alpha2-agonists, are often used as adjuncts to anesthesia. Thus, we conducted the current study to determine the effect of clonidine, dexmedetomidine, and xylazine at clinically (or veterinary anesthetically) relevant concentrations (and 10 and 100 times these concentrations) on several aspects of human neutrophil functions using an in vitro system. The three alpha2-agonists had no effects on chemotaxis, phagocytosis, or superoxide anion (O2-) production of neutrophils, except that the highest concentration of clonidine inhibited chemotaxis. Increases in intracellular calcium concentrations in neutrophils stimulated by chemotaxin were not influenced by clonidine, dexmedetomidine, or xylazine. Unchanged calcium concentrations may contribute to failure to modulate the neutrophil functions. In addition, these drugs did not scavenge O2- generated by the cell-free (xanthine-xanthine oxidase) system. This is the first report concerning the effect of clonidine or dexmedetomidine on human neutrophil functions. Our findings suggest that we may not have to take extra precautions in using the alpha2-agonists in patients with infection, but that we cannot expect these drugs to be prophylaxis against autotissue injuries whose pathogenesis includes activation of neutrophils. ⋯ Neutrophils are involved in the antibacterial host defense system and autotissue injury. We found that clinically relevant concentrations of clonidine and dexmedetomidine do not affect chemotaxis, phagocytosis, or superoxide production by human neutrophils. These findings indicate that it may not be necessary to take special care in using alpha2-agonists in patients with infection, sepsis, or systemic inflammation.
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Anesthesia and analgesia · Feb 1999
Comparative StudyBeta-adrenergic blockers and vasovagal episodes during shoulder surgery in the sitting position under interscalene block.
Shoulder surgery is often performed with patients in the sitting position under interscalene block anesthesia. Vasovagal episodes, characterized by a sudden decrease in heart rate and/or blood pressure, have a reported incidence of 17%-24% in this setting. We performed a retrospective study to determine whether there was an association between the use of beta-adrenergic blockers and the incidence of these episodes. Of the 150 patients identified, 20 (13.3%) had a vasovagal event. Similar proportions of patients had received a beta-adrenergic blocker in the group who had a vasovagal event compared with those who did not (20% vs 18%; P = 0.95). No other differences could be identified. We conclude that vasovagal episodes occur frequently in this setting with no identifiable risk factors. Beta-adrenergic blockers were not associated retrospectively with either an increased or decreased incidence of these episodes. The most likely mechanism involves the Bezold-Jarisch reflex. ⋯ In this retrospective study of 150 patients who underwent shoulder surgery in the sitting position under interscalene block, we found a 13% incidence of vasovagal episodes. Unlike a previous study, this was not affected by the use of beta-blockers. A randomized, prospective study is necessary to clarify this issue.
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Anesthesia and analgesia · Feb 1999
Comparative StudyTransnasal transesophageal echocardiography: a modified application mode for cardiac examination in ventilated patients.
In 42 endotracheally intubated patients, we examined the utility of a miniaturized monoplane probe for transnasal transesophageal echocardiography (TEE). Transnasal TEE was prospectively evaluated in 26 deeply and 16 mildly sedated patients receiving topical anesthesia with lidocaine jelly 2%. The patients with deep sedation were additionally examined with transoral monoplane and multiplane TEE. Transnasal esophageal insertion of the TEE probe was successfully performed in 90% of patients. Endotracheal malpositioning was corrected in two patients. Nasal bleeding required treatment in another patient. Topical anesthesia was adequate in 82% of mildly sedated patients. Left ventricular short- and four-chamber long-axis views of good quality were obtained with transnasal (transoral) monoplane TEE in 76% (81%) and 92% (96%) of patients (differences not significant). Compared with conventional multiplane TEE, transnasal monoplane TEE missed diagnoses in 19% of patients. The relative error (mean +/- SEM) of quantification with transnasal TEE was <9% +/- 2% for ventricular diameters and <7% +/- 2% for cross-sectional area measurements, with a bias of 0.5 +/- 3.8 cm2 and 0.1 +/- 2.4 cm2 (mean +/- 2 SD) for left ventricular end-diastolic and end-systolic short-axis areas. The relative error in measuring intracardiac flow velocities was >40%, but systolic to diastolic peak velocity ratios at the valvular site were determined with an error <4% +/- 3%. Transnasal monoplane TEE can be performed even in mildly sedated patients with an endotracheal tube without further need for analgesia or sedation. The technique is as useful as conventional transoral TEE to image standard tomographic planes for quantification, but it is less suited for comprehensive echocardiographic diagnosing. ⋯ Transnasal insertion of a miniaturized monoplane transesophageal echocardiography (TEE) probe was studied in endotracheally intubated patients. Nasal passage was well tolerated even by patients with only mild sedation. Imaging quality was similar to conventional transoral monoplane TEE with larger transducers, but technical restraints cause a deficit in complete cardiac diagnosing obtained with multiplane TEE.
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Anesthesia and analgesia · Feb 1999
Comparative StudyCraniotomy procedures are associated with less analgesic requirements than other surgical procedures.
The conventional wisdom that neurosurgical patients experience minimal postoperative pain and require little analgesia has been challenged. To address this, we reviewed our anesthesia and postanesthesia care unit (PACU) records for 1995 and compared pain management in patients undergoing major intracranial and selected extracranial procedures. We recorded patient weight, operative time, time in the PACU, intraoperative and postoperative opioid use, PACU pain scores, and level of consciousness in patients who had undergone open fixation of mandible or maxilla (Group E), clipping of aneurysms or excision of tumors (Group I), or lumbar laminectomy (Group L). Group I (n = 78) patients received less fentanyl in the operating room (0.016 microg x kg(-1) x min(-1) versus 0.023 microg x kg(-1) x min(-1) for Group E [n = 134] and 0.023 microg x kg(-1) x min(-1) for Group L [n = 21]; P < 0.05), received less morphine in the PACU (0.0004 vs 0.0013 vs 0.0015 mg kg(-1) x min(-1); P < 0.005), reported lower pain scores (0.76 vs 2.5 vs 2.4; P < 0.05), and spent less time in the PACU (89.5 vs 109 vs 105 min; P < 0.05) than Group E or L patients. Our results were similar when only patients with Glasgow Coma Scale scores > or = 14 were used in a subset analysis. We conclude that patients suffer less pain and use fewer opioids in the PACU after intracranial surgery than after facial reconstruction or lumbar laminectomy. Our results confirm that the average craniotomy patient has less postoperative pain than patients who undergo other surgical procedures, although patients who undergo frontal craniotomy may require more aggressive pain management. ⋯ This study compares the pain report and analgesic use in patients after intracranial versus extracranial surgery. The results confirm the commonly held but recently challenged belief that neurosurgery patients suffer less pain postoperatively than other patients. In this study, we found that most patients report minimal pain after intracranial surgery but that a small subset of patients, many of whom have undergone frontal craniotomies, require aggressive treatment of postoperative pain.