Anesthesia and analgesia
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Anesthesia and analgesia · Mar 2002
Randomized Controlled Trial Clinical TrialThe effects of urapidil on thermoregulatory thresholds in volunteers.
In a previous study we have shown that the antihypertensive drug, urapidil, stops postanesthetic shivering. One possible mechanism in the inhibition of postanesthetic shivering by urapidil may be alterations in thermoregulatory thresholds. We therefore studied the effects of urapidil on vasoconstriction and shivering thresholds during cold-induced shivering in volunteers. Seven healthy male volunteers were cooled by an infusion of saline at 4 degrees C on two study days separated by 48 h. Thermoregulatory vasoconstriction was estimated using forearm minus fingertip skin-temperature gradients, and values exceeding 0 degrees C were considered to represent significant vasoconstriction. The rectal core temperatures at the beginning of shivering and at vasoconstriction were considered the thermoregulatory thresholds. Before cooling, either 25 mg of urapidil or placebo was administered randomly and blindly to each volunteer. When shivering occurred continuously for 10 min, another 25 mg of urapidil was administered IV to completely stop shivering. Urapidil led to a decrease in core temperature at vasoconstriction and shivering threshold by 0.4 degrees C plus/minus 0.2 degrees C (P < 0.001) and 0.5 degrees C plus/minus 0.3 degrees C (P < 0.01), respectively. Oxygen consumption increased during shivering by 70% plus/minus 30% (P < 0.01) in comparison with baseline and decreased levels after shivering stopped, despite the continued low core temperature. Our investigation shows that urapidil stops postanesthetic shivering by decreasing important thermoregulatory thresholds. This means that shivering, not hypothermia, is treated, and hypothermia will need more attention in the postanesthesia care unit. ⋯ In this study we show that the antihypertensive drug urapidil stops cold-induced shivering and decreases normal thermoregulatory responses, i.e., the thresholds for vasoconstriction and shivering, in awake volunteers.
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Anesthesia and analgesia · Mar 2002
Randomized Controlled Trial Comparative Study Clinical TrialSpinal ropivacaine for cesarean delivery: a comparison of hyperbaric and plain solutions.
We compared, in this prospective, randomized, double-blinded study, the characteristics of spinal anesthesia with plain and hyperbaric ropivacaine for elective cesarean delivery. We hypothesized that the addition of glucose would change the onset, offset, and extent of motor and sensory block from intrathecal ropivacaine. Forty ASA physical status I--II women were given 25 mg of either ropivacaine (n = 20) or ropivacaine in 8.3% glucose (n = 20) intrathecally, via a combined spinal/epidural technique in the right lateral position. Sensory changes to ice and pinprick and motor block (Bromage score) were recorded at 2.5-min intervals. Adequate anesthesia for surgery was achieved in all patients in the Hyperbaric group, whereas in the Plain group, five (25%) patients required epidural top-up because of insufficient rostral spread (P < 0.05). With hyperbaric ropivacaine, we found the following: higher cephalic spread (median [range] maximum block height to pinprick, T1 [T4 to C2] versus T3 [T11 to C3], P < 0.001); lower coefficient of variation of maximum block height (17.7% vs 21.9%); faster onset to T4 dermatome (mean [SD] 7.7 [4.9] vs 16.4 [14.1] min, P = 0.015); and faster recovery to L1 (189.0 [29.6] vs 215.5 [27.0] min, P = 0.01). The onset of complete motor block (9.9 [5.3] vs 13.8 [5.4] min, P = 0.027) and complete recovery (144.8 [28.4] vs 218.5 [56.8] min, P < 0.001) was also faster. No neurologic symptoms were found at 24 h. ⋯ We compared hyperbaric and plain ropivacaine for combined spinal/epidural analgesia in the lateral position in patients undergoing elective cesarean delivery. Hyperbaric ropivacaine produced more rapid block with faster recovery and less requirement for epidural supplementation compared with plain ropivacaine.
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Anesthesia and analgesia · Mar 2002
Randomized Controlled Trial Clinical TrialPhysostigmine does not antagonize sevoflurane anesthesia assessed by bispectral index or enhances recovery.
In this double-blinded study, we investigated the effect of physostigmine on sevoflurane anesthesia and recovery. Forty female patients scheduled for breast biopsy were randomly assigned to receive either physostigmine 2 mg IV or an equal volume of normal saline after skin closure. Anesthesia was induced and maintained with sevoflurane in oxygen. After skin closure, a steady state of 0.6% inspired and end-tidal sevoflurane concentration was obtained, heart rate, blood pressure, and Bispectral index (BIS) baseline values were recorded, and physostigmine or normal saline was administered. Hemodynamics and BIS values were also recorded 5, 8, and 10 min after treatments. Anesthesia was discontinued, and orientation, sedation, sitting ability, and "picking up matches" scores were recorded immediately after extubation and 15 and 30 min later. No differences were found between the two groups in BIS (69, 70, 70, and 71 in the Physostigmine group versus 70, 74, 75, and 76 in the Control group) or blood pressure. Only heart rate was increased 8 min after physostigmine (P < 0.05 versus the control). Scores assessing early recovery were similar in the two groups at all time points. We conclude that physostigmine does not change BIS or enhance recovery after sevoflurane anesthesia. ⋯ This double-blinded, randomized study investigated the impact of physostigmine of BIS values during 0.6% sevoflurane anesthesia as well as in the postoperative recovery, when sevoflurane is administered as a sole anesthetic. Physostigmine has no effect on BIS values or on the tests assessing recovery.
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Anesthesia and analgesia · Mar 2002
Comparative StudyThe neuromuscular transmission module versus the relaxometer mechanomyograph for neuromuscular block monitoring.
The neuromuscular transmission module (M-NMT) is an integrated piezoelectric motion sensor module incorporated in the AS/3(TM) anesthesia monitor. We compared the neuromuscular block of 0.6 mg/kg rocuronium (twice the 95% effective dose) monitored by the M-NMT with that monitored by the Relaxometer mechanomyograph (MMG). The two monitors were alternately allocated to the left or right hands of 20 patients. T(1)%, the first twitch of the train-of-four (TOF), and the TOF ratio (T(4)/T(1)) were used for evaluating the neuromuscular block. There was no significant difference in the mean (min) plus minus SD onset time or time to 0.8 TOF ratio recovery measured by the M-NMT (1.5 plus/minus 0.3, 49.4 plus/minus 8.1) compared with MMG (1.8 plus/minus 0.6, 50.9 plus/minus 9.9), respectively. However, the time (min) to 25% T(1) recovery was significantly longer when monitored by the M-NMT (25.6 plus/minus 8) than by the MMG (20.2 plus/minus 6.3). During recovery from neuromuscular block, the difference between the TOF ratios measured by the two monitors showed a bias of -0.031, and the limits of agreement (bias plus/minus 1.96 SD) were -0.281 and +0.22. The M-NMT monitor could determine the time to tracheal intubation as well as full recovery from neuromuscular block, but it lagged behind the MMG in determining the time to rocuronium repeat dose administration. ⋯ Compared with the Relaxometer mechanomyograph, the neuromuscular transmission module could equally indicate time to tracheal intubation and full recovery from 0.6 mg/kg rocuronium neuromuscular block. Its small quick-fit sensor has the advantage, in an often crowded and busy operating room, of being incorporated in the AS/3(TM) anesthesia workstation.
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The tracheas of obese patients may be more difficult to intubate than those of normal-weight patients. We studied 100 morbidly obese patients (body mass index >40 kg/m(2)) to identify which factors complicate direct laryngoscopy and tracheal intubation. Preoperative measurements (height, weight, neck circumference, width of mouth opening, sternomental distance, and thyromental distance) and Mallampati score were recorded. The view during direct laryngoscopy was graded, and the number of attempts at tracheal intubation was recorded. Neither absolute obesity nor body mass index was associated with intubation difficulties. Large neck circumference and high Mallampati score were the only predictors of potential intubation problems. Because in all but one patient the trachea was intubated successfully by direct laryngoscopy, the neck circumference that requires an intervention such as fiberoptic bronchoscopy to establish an airway remains unknown. We conclude that obesity alone is not predictive of tracheal intubation difficulties. ⋯ In 100 morbidly obese patients, neither obesity nor body mass index predicted problems with tracheal intubation. However, a high Mallampati score (greater-than-or-equal to 3) and large neck circumference may increase the potential for difficult laryngoscopy and intubation.