Anesthesia and analgesia
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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 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 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
Validation of measures of parents' preoperative anxiety and anesthesia knowledge.
Parents' anxiety about their children's anesthesia may adversely affect the children's outcomes and compromise the quality of informed consent. Studies of these issues have been limited by the lack of validated measures of parental anxiety and knowledge surrounding anesthesia. In the present study, we evaluated psychometric properties of the Amsterdam Preoperative Anxiety and Information Scale (APAIS) and the Standard Anesthesia Learning Test (SALT) among 85 parents who participated in an evaluation of the effects of a videotape about pediatric anesthesia. The results supported the internal consistency, test-retest reliability, and concurrent validity of both instruments and documented the equivalence of two forms of the SALT. Factor analysis supported the previously demonstrated factor structure of the APAIS, further confirming its construct validity. We conclude that the APAIS and SALT are reliable and valid measures of parental anxiety and knowledge of pediatric anesthesia that can be used for clinical and research purposes. ⋯ This study verified the reliability and validity of two questionnaires for measuring parents' knowledge and anxiety about pediatric anesthesia. These questionnaires can be used in further research on factors affecting parental anxiety and knowledge before their children's surgery.
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Anesthesia and analgesia · Feb 1999
Comparative StudyThe effect of nitroglycerin on pacing-induced changes in myocardial oxygen consumption and metabolic coronary vasodilation in patients with coronary artery disease.
In the present study, we assessed the potential effect of nitroglycerin IV (NTG), a donor of exogenous nitric oxide, on metabolic coronary flow control in patients with coronary artery disease. In 12 patients scheduled for coronary artery surgery, arterial blood pressure, pulmonary capillary wedge pressure, coronary sinus blood flow (continuous thermodilution), myocardial oxygen supply (DVO2), and myocardial oxygen consumption (MVO2) were measured at sinus rhythm and in response to atrial pacing at 30 bpm greater than baseline sinus rate. These measurements were repeated during infusion of NTG 1 and 2 microg x kg(-1) x min(-1). At control, in the absence of NTG, MVO2 increased from 13.7 +/- 3.4 mL O2/min during sinus rhythm to 19.3 +/- 5.5 mL O2/min during pacing. NTG 1 and 2 microg x kg(-1) x min(-1) blunted the pacing-induced increase in MVO2 dose-dependently. During NTG 1 microg x kg(-1) x min(-1), MVO2 increased from 12.9 +/- 3.3 mL O2/min at sinus rhythm to 17.3 +/- 4.7 mL O2/min during pacing (P = 0.01 versus control pacing); during NTG 2 microg x kg(-1) x min(-1), MVO2 increased from 13.4 +/- 3.3 mL O2/min to 15.9 +/- 3.7 mL O2/min (P = 0.008 versus control pacing). However, the pacing-induced increase in DVO2 per mL O2/min increase in MVO2 (delta DVO2/delta MVO2), was significantly greater during the infusion of NTG 2 microg x kg(-1) x min(-1) (1.85 +/- 0.56; P = 0.023) compared with control (1.51 +/- 0.22). This was associated with an increase in coronary sinus hemoglobin oxygen saturation (30% +/- 5% at control pacing and 34% +/- 6% during pacing with NTG 2 microg x kg(-1) x min(-1); P = 0.018), which indicates that during the infusion of NTG, there was more metabolic coronary vasodilation than achievable solely on the basis of the metabolic stimulus. ⋯ Our findings suggest that nitroglycerin, a donor of exogenous nitric oxide, reduces pacing-induced increases in myocardial oxygen consumption and enhances metabolic coronary vasodilation in patients with coronary artery disease, in whom endogenous nitric oxide activity may be reduced.