Anesthesia and analgesia
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Anesthesia and analgesia · Aug 2003
Clinical TrialThe effects of large-dose propofol on cerebrovascular pressure autoregulation in head-injured patients.
In healthy individuals, cerebrovascular pressure autoregulation is preserved or even improved when propofol is infused. We examined the effect of an increase in propofol plasma concentration on pressure autoregulation in 10 head-injured patients. Using target-controlled infusions, the static rate of autoregulation was determined at a moderate (2.3 +/- 0.4 microg/mL) and a large (4.3 +/- 0.04 microg/mL) plasma target concentration of propofol. Using norepinephrine to control cerebral perfusion pressure, transcranial Doppler measurements from the middle cerebral artery were made at a cerebral perfusion pressure of 70 and 85 mm Hg at each propofol concentration. Middle cerebral artery flow velocities at the large propofol concentration were significantly lower than at the moderate concentration, without any concurrent increase in arterio-jugular difference in oxygen content, a finding compatible with maintained flow-metabolism coupling. Despite this, static rate of autoregulation decreased significantly from 54% +/- 36% to 28% +/- 35% (P = 0.029). Our data suggest that after head injury, the cerebrovascular effects of propofol are different from those observed in healthy individuals. We propose that large doses of propofol should be used cautiously in head-injured patients, because there is the potential to increase the injured brain's vulnerability to secondary insults. ⋯ Propofol is used for sedation and control of intracranial pressure in head-injured patients. In contrast to previous data from healthy individuals, we show a deterioration of cerebrovascular pressure autoregulation with fast propofol infusion rates after head injury. Large propofol doses may increase the injured brain's vulnerability to secondary insults.
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Anesthesia and analgesia · Aug 2003
Randomized Controlled Trial Comparative Study Clinical TrialIsobaric versus hypobaric spinal bupivacaine for total hip arthroplasty in the lateral position.
Total hip arthroplasty (THA) is frequently performed under spinal anesthesia using either isobaric or hypobaric anesthetic solution. However, these two solutions have never been compared under similar surgical conditions. In the present study, we compared the anesthetic and hemodynamic effects of isobaric and hypobaric bupivacaine in 40 ASA physical status I-II patients undergoing THA in the lateral decubitus position under spinal anesthesia. With operative side up, patients randomly received, in a double-blinded manner, a spinal injection of 3.5 mL (17.5 mg) of plain bupivacaine mixed with either 1.5 mL of normal saline (isobaric group) or 1.5 mL of distilled water (hypobaric group). Sensory level and degree of motor block were evaluated on the nondependent and dependent sides until regression to L2 and total motor recovery. Hemodynamic changes during the first 45 min after spinal injection, and the time between spinal administration and first analgesic for a pain score >3 (on a 0-10 scale) were noted. Demographic characteristics of both groups were comparable. Upper sensory level and maximal degree of motor block were comparable between the operative and nonoperative sides in each group and between corresponding sides in both groups. Compared with the isobaric group, in the hypobaric group there was a prolonged time to sensory regression to L2 on the operative side (287 +/- 51 versus 242 +/- 36 min, P < 0.004) and a prolonged time to first analgesic (290 +/- 46 versus 237 +/- 39 min, P < 0.001). No difference in quality of motor block was noted at the end of surgery. Hemodynamic changes were comparable. We conclude that for THA in the lateral position, spinal hypobaric bupivacaine seems to be superior to isobaric in that it prolongs the sensory block on the operative side and delays the use of analgesics after surgery without further compromising hemodynamic stability. ⋯ For total hip arthroplasty in the lateral position, spinal hypobaric bupivacaine compared with isobaric prolonged sensory block at the operative side and delayed the time to first analgesic.
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Anesthesia and analgesia · Aug 2003
Randomized Controlled Trial Clinical TrialThe effect of exogenous epinephrine on the incidence of hypotensive/bradycardic events during shoulder surgery in the sitting position during interscalene block.
Sudden hypotensive and/or bradycardic events (HBE) have been reported in 13%-28% of patients undergoing shoulder surgery in the sitting position during interscalene block. The Bezold-Jarisch reflex is the most likely mechanism for these events. It has been hypothesized that exogenous epinephrine might be a key component to the occurrence of HBE. We conducted this prospective, randomized study to verify this hypothesis. Patients received a local anesthetic solution with (Group E; n = 55) or without (Group P; n = 55) epinephrine for interscalene block; no further exogenous epinephrine was administered. Blood pressure control was achieved with IV urapidil, a peripheral vasodilator, as needed. The incidence of HBE was 11% in Group P versus 29% in Group E (P = 0.015). Increased intraoperative heart rate and arterial blood pressure were recorded in Group E (P = 0.000). Urapidil was administered to 13% of Group P and to 31% of Group E patients (P = 0.018). Urapidil administration induced a HBE in 4% of Group P and in 5% of Group E patients. We conclude that exogenous epinephrine is involved in the development of HBE in this setting. ⋯ Sudden hypotensive and/or bradycardic events occur during shoulder surgery in the sitting position during interscalene block. In this study, we demonstrated that the presence of epinephrine in the local anesthetic mixture significantly increases the incidence of these events.
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Anesthesia and analgesia · Aug 2003
Randomized Controlled Trial Comparative Study Clinical TrialPostoperative sensitization and pain after cesarean delivery and the effects of single im doses of tramadol and diclofenac alone and in combination.
Combining different analgesic mechanisms can reduce postoperative pain. We investigated postoperative pain and sensory sensitization in a double-blinded, placebo-controlled, randomized, single-dose comparison of the monoaminergic and micro -opioid agonist tramadol, 100 mg, and diclofenac 75 mg given IM in combination or alone in 120 patients who had elective cesarean delivery. The time to first postoperative demand for rescue analgesia, pain, tramadol pharmacokinetics, and electrical sensory thresholds at or distant from the incision were studied. The median time to first rescue (interquartile range) was 197 min (70-1000 min) with tramadol plus diclofenac, 48 min (25-90 min) with tramadol plus placebo, 113 min (35-270 min) with diclofenac plus placebo, and 55 min (30-100 min) with double placebo (tramadol plus diclofenac versus all other groups, P < 0.05). Pain intensity decreased markedly over time in all groups, and time and drug effects were significant (analysis of variance; P < 0.00001). Side effects were similarly minimal with all treatments. Pain thresholds at or distant from the incision increased significantly after surgery only with tramadol plus diclofenac. Preoperative sensory thresholds correlated with postoperative sensory changes (r > 0.53; P < 0.0001). The pharmacokinetics of tramadol and O-desmethyltramadol were unchanged by diclofenac. The combination of tramadol and diclofenac resulted in improved analgesia compared with monotherapy. Only the analgesic combination prevented both primary and secondary hyperalgesia. Preoperative sensory thresholds may allow prediction of postoperative sensitization. ⋯ The parenteral combination of tramadol and diclofenac resulted in more prolonged and pronounced postoperative analgesia and reduced sensory sensitization compared with the single drugs, with no increase in side effects.