Anesthesia and analgesia
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Anesthesia and analgesia · Jun 1999
The age-related effects of epidural lidocaine, with and without epinephrine, on spinal cord blood flow in anesthetized rabbits.
The effect of epidural or spinal epinephrine when added to local anesthetics on spinal cord blood flow (SCBF)are controversial. We evaluated the effects of epidural lidocaine, with or without epinephrine, on spinal cord blood flow in young and adult rabbits receiving 2% plain lidocaine, 2% lidocaine with epinephrine (1:200,000), or saline epidurally. Colored microspheres were injected through the left ventricle 10 min before and 7.5 and 30 min after epidural injection. The organs (brain, heart, kidneys, and the L6-7 segment of the spinal cord) were analyzed for regional blood flow determination. A significant decrease in mean arterial pressure was observed after the administration of lidocaine, with or without epinephrine, in both adult and young animals compared with saline. SCBF did not change over time in adult rabbits. Conversely, a significant decrease in SCBF was observed in the two groups of young rabbits receiving lidocaine. This decrease correlated with the decrease in mean arterial pressure but did not correlate with the use of epinephrine. We conclude that any reduction in blood pressure occurring in pediatric patients receiving a combined epidural-general anesthetic may result in decreased SCBF. ⋯ In young rabbits, any decrease in blood pressure was followed by a decrease in spinal cord blood flow, a decrease that did not correlate to the use of epinephrine and was not observed in adult animals. These data suggest that blood pressure should be monitored closely to promptly treat any decrease in blood pressure when combined epidural-general anesthesia is used in children.
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Anesthesia and analgesia · Jun 1999
Randomized Controlled Trial Clinical TrialThe effects of clonidine on sensitivity to phenylephrine and nitroprusside in patients with essential hypertension recovering from surgery.
Clonidine reduces postoperative circulatory instability in patients with essential hypertension. It also increases the sensitivity to vasopressors before and during anesthesia. We investigated blood pressure responses to phenylephrine and nitroprusside pre- vs postoperatively and the effect of clonidine on these responses in patients with essential hypertension. Twenty patients received clonidine 6 microg/kg orally 120 min before anesthesia and 3 microg/kg IV over the final hour of surgery or an identical placebo. During increasing bolus doses of phenylephrine and nitroprusside (30-300 microg), the maximal systolic pressure responses were recorded at baseline on the day before surgery, before the induction of anesthesia, and 1 and 3 h postoperatively. Sensitivity to phenylephrine and nitroprusside was interpolated from linear regression of the data. There was no difference between preoperative and postoperative sensitivity to phenylephrine or nitroprusside in either group. Clonidine increased sensitivity to phenylephrine versus placebo before and after surgery (response to dose of 1.5 microg/kg: 42+/-14 vs 27+/-8 mm Hg preinduction, 37+/-10 vs 26+/-8 mm Hg 3 h postoperatively; both P < 0.01), but not to nitroprusside (38+/-6 vs 37+/-10 mm Hg preinduction and 40+/-6 vs 39+/-8 mm Hg postoperatively). Clonidine increases the sensitivity to phenylephrine but not nitroprusside at baseline and postoperatively in hypertensive patients. ⋯ Clonidine increases the sensitivity to bolus injections of the vasoconstrictor phenylephrine, but not the vasodilator sodium nitroprusside, before and after surgery in patients with preexisting hypertension. The doses of vasopressors should be reduced accordingly in hypertensive patients receiving perioperative clonidine.
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Anesthesia and analgesia · Jun 1999
Meta AnalysisThe use of nonpharmacologic techniques to prevent postoperative nausea and vomiting: a meta-analysis.
We assessed the efficacy of nonpharmacologic techniques to prevent postoperative nausea and vomiting (PONV) by systematic review. These studies included acupuncture, electroacupuncture, transcutaneous electrical nerve stimulation, acupoint stimulation, and acupressure. Of the 24 randomized trials retrieved by a search of articles indexed on the MEDLINE and EMBASE databases (1980-1997), 19 were eligible for meta-analysis. The primary outcomes were the incidence of nausea, vomiting, or both 0-6 h (early efficacy) or 0-48 h (late efficacy) after surgery. The pooled relative risk (RR) and numbers needed to treat (NNT) were calculated. In children, no benefit was found. Some results in adults were significant. Nonpharmacologic techniques were similar to antiemetics in preventing early vomiting (RR = 0.89 [95% confidence interval 0.47-1.67]; NNT = 63 [10-infinity]) and late vomiting (RR = 0.80 [0.35-1.81]; NNT = 25 [5-infinity]) in adults. Nonpharmacologic techniques were better than placebo at preventing early nausea (RR = 0.34 [0.20-0.58]; NNT = 4 [3-6]) and early vomiting in adults (RR = 0.47 [0.34-0.64]; NNT = 5 [4-8]). Nonpharmacologic techniques were similar to placebo in preventing late vomiting in adults (RR = 0.81 [0.46-1.42]; NNT = 14 [6-infinity]). Using nonpharmacologic techniques, 20%-25% of adults will not have early PONV compared with placebo. It may be an alternative to receiving no treatment or first-line antiemetics. ⋯ This systematic review showed that nonpharmacologic techniques were equivalent to commonly used antiemetic drugs in preventing vomiting after surgery. Nonpharmacologic techniques were more effective than placebo in preventing nausea and vomiting within 6 h of surgery in adults, but there was no benefit in children.
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Anesthesia and analgesia · Jun 1999
Randomized Controlled Trial Clinical TrialTransient hyperdynamic response associated with controlled hypocapneic hyperventilation during sevoflurane-nitrous oxide mask induction in adults.
We assessed hemodynamic variables during sevoflurane face mask anesthetic induction in female ASA physical status I or II patients. Anesthesia was induced with a single-breath inhalation method with 8% sevoflurane in 50% nitrous oxide in oxygen. Thirty patients were randomized either to breathe spontaneously (SB group, n = 15) or to receive controlled ventilation (CV group, n = 15) for 6 min after the loss of consciousness. Noninvasive blood pressure and heart rate (HR) were recorded at 1-min intervals. Mean +/- SD HR increased from 83+/-18 to 112+/-24 bpm at 4 min in the CV group (P < 0.001 between groups and within group compared with baseline). Mean arterial pressure increased from 97+/-9 to 106+/-26 mm Hg at 4 min in the CV group, which was significantly higher than that in the SB group (P < 0.01). In the SB group, mean arterial pressure decreased significantly, from 96+/-8 to 78+/-13 mmHg, at 6 min (P < 0.001), and HR remained unchanged. Therefore, hyperventilation should be avoided during the induction of sevoflurane anesthesia via a mask. ⋯ In this randomized, prospective study, we found that controlled hypocapneic hyperventilation delivered manually during sevoflurane/ N2O/O2 mask induction was associated with a significant transient hyperdynamic response. This kind of hemodynamic arousal can be detrimental to many patients and can be avoided by conducting sevoflurane mask induction with unassisted spontaneous breathing.