Anesthesia and analgesia
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Anesthesia and analgesia · Jan 1997
Randomized Controlled Trial Clinical TrialThe duration of impairment of autonomic control after anticholinergic drug administration in humans.
Impaired parasympathetic control of heart rate is associated with increased incidence of cardiac dysrhythmias and ischemia. Anticholinergic drugs, commonly administered during reversal of neuromuscular blockade, suppress parasympathetic control in the early postoperative period. This could potentially be detrimental in patients at risk of cardiovascular complications. ⋯ Both drugs resulted in a marked decrease in baroreflex sensitivity and high-frequency heart rate variability. The times to return to baseline values were approximately doubled after atropine compared to glycopyrrolate (177 +/- 22 vs 82 +/- 8 min for baroreflex sensitivity, 212 +/- 16 vs 111 +/- 14 min for high-frequency power, and 171 +/- 18 vs 95 +/- 18 min for high-frequency power normalized to total power; P < 0.01 for all variables). Atropine leads to more prolonged impairment of parasympathetic control than equipotent doses of glycopyrrolate, and its use may thus be less desirable in high-risk patients in the early postoperative period.
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Anesthesia and analgesia · Jan 1997
Randomized Controlled Trial Clinical TrialSmall-dose hypobaric lidocaine-fentanyl spinal anesthesia for short duration outpatient laparoscopy. II. Optimal fentanyl dose.
We performed a double-blind, controlled trial to determine the optimal dose of intrathecal fentanyl in small-dose hypobaric lidocaine spinal anesthesia for outpatient laparoscopy. Sixty-four gynecological patients were randomized into three groups, receiving 0, 10, or 25 micrograms fentanyl added to 20 mg lidocaine and sterile water (total 3 mL). Administration was with 27-gauge Whitacre needles and patients sat upright until the block was > T-8. ⋯ Based on these results, we concluded that 25 micrograms intrathecal fentanyl is required when 20 mg lidocaine is used for hypobaric spinal anesthesia (SA) to ensure reliable, durable anesthesia, reduce shoulder-tip pain, and minimize the need for intraoperative supplementation. This dose provides longer postoperative analgesia and does not increase side effects apart from pruritus. SA with small-dose hypobaric lidocaine-fentanyl was found to be a satisfactory technique for outpatient laparoscopy, although postdural puncture headache can occur in some patients.
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Anesthesia and analgesia · Jan 1997
Randomized Controlled Trial Clinical TrialDifferential sensory block after spinal bupivacaine in volunteers.
We performed this study to determine whether differential sensory block to touch, pinprick, and cold after spinal bupivacaine could be used to predict the dermatomal level of block to transcutaneous electrical stimulation (TES) equivalent to surgical stimulation, onset of tourniquet pain, or magnitude of hemodynamic depression. Eight subjects per group were randomized to receive 3.75, 7.5, or 11.25 mg of 0.75% bupivacaine with 8.25% dextrose in a double-blind fashion. Sensory block was assessed with touch, pinprick, cold, TES at T-12, L-2, S-1, and thigh tourniquet pain. ⋯ However, the extent of differential sensory block to touch, pinprick, and cold varied up to 10 dermatomes (2 SD) cephalad to block to TES and up to 7 dermatomes (2 SD) cephalad to the thigh tourniquet at the time of intolerable tourniquet pain. Sensory block to cold did not correlate with hemodynamic depression. Differential sensory block occurs after bupivacaine spinal anesthesia, but is a poor predictor for surgical anesthesia, tourniquet pain, and hemodynamic depression.
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Anesthesia and analgesia · Jan 1997
Clinical Trial Controlled Clinical TrialRegional brain activity changes associated with fentanyl analgesia elucidated by positron emission tomography.
Recent positron emission tomography (PET) studies have demonstrated areas of pain processing in the human brain. Given the inhibitory effects of opioids on neuronal activity, we predicted that fentanyl's analgesic effects would be associated with suppression of pain-evoked responses in these distinct brain areas. To test this, PET was used to measure cerebral blood flow responses, as reflections of regional neuronal activity, to painful and nonpainful thermal stimuli both in the absence and presence of fentanyl in humans. ⋯ During combined pain stimulation and fentanyl administration, fentanyl significantly augmented pain-related rCBF increases in the supplementary motor area and prefrontal cortex. This activation pattern was associated with decreased pain perception, as measured on a visual analog scale. In contrast to our hypothesis, these data indicate that fentanyl analgesia involves augmentation of pain-evoked cerebral responses in certain areas, as well as both activation and inhibition in other brain regions unresponsive to pain stimulation alone.
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Anesthesia and analgesia · Jan 1997
Cerebral ischemic disorders and cerebral oxygen balance during cardiopulmonary bypass surgery: preoperative evaluation using magnetic resonance imaging and angiography.
We compared the preoperative prevalence of small cerebral infarctions and carotid stenosis to jugular venous oxygen saturation (Sjvo2) during coronary artery bypass grafting (CABG). Sjvo2 served as an indicator of whether cerebral oxygen supply meets demand in patients on cardiopulmonary bypass (CPB). The study population consisted of 121 patients who were either older than 65 yr or had a history of cerebrovascular disease. ⋯ In patients with small infarctions, Sjvo2 was significantly lower than in patients without infarctions (controls) at initiation of CPB, 30 min after aortic cross-clamping, and during the rewarming period of CPB (P < 0.05). Thus, small cerebral infarctions were not uncommon in elderly patients undergoing CABG. Patients with small cerebral infarctions may be at risk for an imbalance in cerebral oxygen supply and demand during the rewarming period because they are unable to deliver the necessary compensatory blood flow.