Anesthesia and analgesia
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Anesthesia and analgesia · Jan 2004
Randomized Controlled Trial Comparative Study Clinical TrialMechanical versus manual ventilation via a face mask during the induction of anesthesia: a prospective, randomized, crossover study.
One approach to make ventilation safer in an unprotected airway has been to limit tidal volumes; another one might be to limit peak airway pressure, although it is unknown whether adequate tidal volumes can be delivered. Accordingly, the purpose of this study was to evaluate the quality of automatic pressure-controlled ventilation versus manual circle system face-mask ventilation regarding ventilatory variables in an unprotected airway. We studied 41 adults (ASA status I-II) in a prospective, randomized, crossover design with both devices during the induction of anesthesia. Respiratory variables were measured with a pulmonary monitor (CP-100). Pressure-controlled mask ventilation versus circle system ventilation resulted in lower (mean +/- SD) peak airway pressures (10.6 +/- 1.5 cm H(2)O versus 14.4 +/- 2.4 cm H(2)O; P < 0.001), delta airway pressures (8.5 +/- 1.5 cm H(2)O versus 11.9 +/- 2.3 cm H(2)O; P < 0.001), expiratory tidal volume (650 +/- 100 mL versus 680 +/- 100 mL; P = 0.001), minute ventilation (10.4 +/- 1.8 L/min versus 11.6 +/- 1.8 L/min; P < 0.001), and peak inspiratory flow rates (0.81 +/- 0.06 L/s versus 1.06 +/- 0.26 L/s; P < 0.001) but higher inspiratory time fraction (48% +/- 0.8% versus 33% +/- 7.7%; P < 0.001) and end-tidal carbon dioxide (34 +/- 3 mm Hg versus 33 +/- 4 mm Hg; not significant). We conclude that in this model of apneic patients with an unprotected airway, pressure-controlled ventilation resulted in reduced inspiratory peak flow rates and peak airway pressures when compared with circle system ventilation, thus providing an additional patient safety effect during mask ventilation. ⋯ In this model of apneic patients with an unprotected airway, pressure-controlled ventilation resulted in reduced inspiratory peak flow rates and lower peak airway pressures when compared with circle system ventilation, thus providing an additional patient safety effect during face-mask ventilation.
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Anesthesia and analgesia · Jan 2004
Randomized Controlled Trial Comparative Study Clinical TrialSpinal 2-chloroprocaine: a dose-ranging study and the effect of added epinephrine.
With the availability of preservative- and antioxidant-free 2-chloroprocaine (2-CP), there may be an acceptable short-acting alternative to lidocaine for spinal anesthesia. We examined the safety, dose-response characteristics, and effects of epinephrine with spinal 2-CP. Six volunteers per group were randomized to receive 30, 45, or 60 mg of spinal 2-CP with and without epinephrine. Intensity and duration of sensory and motor blockade were assessed. When 11 of the 18 volunteers complained of vague, nonspecific flu-like symptoms, breaking of the blind revealed that all spinal anesthetics associated with the flu-like symptoms contained epinephrine. There were no complaints of flu-like symptoms in the volunteers who received 2-CP without epinephrine. No further spinal anesthetics containing epinephrine were administered, resulting in 29 anesthetics (11 with epinephrine, 18 without epinephrine.) Plain 2-CP demonstrated a dose-dependent increase in peak block height and duration of effect at all variables except time to 2-segment regression and time to regression to T10. Time to complete sensory regression with plain 2-CP was 98 +/- 20, 116 +/- 15, and 132 +/- 23 min, respectively. 2-CP with epinephrine produced times to complete sensory regression of 153 +/- 25, 162 +/- 33, and 148 +/- 29 min, respectively. Preservative and antioxidant free 2-CP can be used effectively for spinal anesthesia in doses of 30-60 mg. Epinephrine is not recommended as an adjunct because of the frequent incidence of side effects. ⋯ Hyperbaric spinal 2-chloroprocaine is effective and has an anesthetic profile appropriate for use in the surgical outpatient over the dose range of 30-60 mg without signs of transient neurologic symptoms. The addition of epinephrine is not recommended because of the frequent incidence of side effects.
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Anesthesia and analgesia · Jan 2004
Randomized Controlled Trial Comparative Study Clinical TrialThe effects of three different approaches on the onset time of sciatic nerve blocks with 0.75% ropivacaine.
We studied three different injection techniques of sciatic nerve block in terms of block onset time and efficacy with 0.75% ropivacaine. A total of 75 patients undergoing foot surgery were randomly allocated to receive sciatic nerve blockade by means of the classic posterior approach (group classic; n = 25), a modified subgluteus posterior approach (group subgluteus; n = 25), or a lateral popliteal approach (group popliteal; n = 25). All blocks were performed with the use of a nerve stimulator (stimulation frequency, 2 Hz; intensity, 2-0.5 mA) and 30 mL of 0.75% ropivacaine. Onset of nerve block was defined as complete loss of pinprick sensation in the sciatic nerve distribution with concomitant inability to perform plantar or dorsal flexion of the foot. In the three groups, an appropriate sciatic stimulation was elicited at <0.5 mA. The failure rate was similar in the three groups (group popliteal: 4% versus group classic: 4% versus group subgluteus: 8%). The onset of nerve block was slower in group popliteal (25 +/- 5 min) compared with group classic (16 +/- 4 min) and group subgluteus (17 +/- 4 min; P < 0.001). There was no significant difference in the onset of nerve block between group classic and group subgluteus. No differences in the degree of pain measured at the first postoperative administration of pain medication were observed among the three groups. We conclude that the three approaches resulted in clinically acceptable anesthesia in the distribution of the sciatic nerve. The subgluteus and classic posterior approaches generated a significantly faster onset of anesthesia than the lateral popliteal approach. ⋯ Comparing three different approaches to the sciatic nerve with 0.75% ropivacaine, the classic and subgluteal approaches exhibited a faster onset time of sensory and motor blockade than the lateral popliteal approach.
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Anesthesia and analgesia · Jan 2004
Randomized Controlled Trial Clinical TrialIntrathecal meperidine decreases shivering during cesarean delivery under spinal anesthesia.
Shivering associated with spinal anesthesia is uncomfortable and may interfere with monitoring. We performed this prospective, double-blinded, and randomized study to determine whether intrathecal meperidine (0.2 mg/kg) decreases the incidence and intensity of shivering after spinal anesthesia for cesarean delivery. Forty parturients scheduled for nonemergent cesarean delivery were enrolled in two groups. Spinal anesthesia consisted of hyperbaric bupivacaine (0.75%; 10.5 mg), morphine 0.15 mg, and, in the experimental group, meperidine (0.2 mg/kg) or, in the control group, normal saline. Data collection, including sensory block level, blood pressure, core temperature, and shivering intensity, was performed every minute for 10 min, every 3 min for 33 min, and then every 5 min until the sensory level receded to L4. Time to highest sensory level, maximum number of blocked segments, sensory and motor blockade regression, and systolic blood pressure showed no difference between groups. The incidence of shivering was less (P < 0.02) in the meperidine group, as was its intensity (P < 0.003). Intrathecal meperidine (0.2 mg/kg) is effective in reducing the incidence and intensity of shivering associated with spinal anesthesia for cesarean delivery. ⋯ Previous studies have suggested that IV meperidine is helpful for treating intraoperative shivering. This study was undertaken to evaluate spinal meperidine and found that it decreases the incidence and intensity of shivering associated with spinal anesthesia for cesarean delivery.