Anesthesia and analgesia
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Anesthesia and analgesia · Nov 2003
Randomized Controlled Trial Comparative Study Clinical TrialThe site of action of epidural fentanyl in humans: the difference between infusion and bolus administration.
Most published studies suggesting that epidural fentanyl acts predominantly at spinal sites administered the drug as a bolus injection, whereas most studies suggesting that it acts predominantly at supraspinal sites administered the drug as an infusion. In this study we tested the hypothesis that the mode of administration (bolus versus infusion) of epidural fentanyl determines its site of action. Ten healthy volunteers were enrolled in this randomized, double-blinded, cross-over study. On separate study days fentanyl was administered into the epidural space as a bolus (0.03 mg followed by 0.1 mg 210 min later) and as an infusion (0.03 mg/h followed by 0.1 mg/hr 210 min later for 200 min). Using a thermal and electrical experimental pain model, the heat ( degrees C) and electrical current (mA) causing maximum tolerable pain were assessed repetitively over a period of 420 min. The analgesic efficacy measures were obtained at a lumbar and a cranial dermatome. Plasma fentanyl concentrations were determined throughout the study. Epidural bolus administration of fentanyl resulted in segmental analgesia (leg > head), whereas the epidural infusion of fentanyl produced nonsegmental analgesia (leg = head). There was a significant linear relationship between the analgesic effect and the plasma concentration of fentanyl for the epidural infusion but not for the epidural bolus administration of fentanyl. These findings support our hypothesis and might explain the apparent conflict in the literature regarding the site of action of epidural fentanyl. ⋯ In an experimental pain study in volunteers, epidural fentanyl caused segmental analgesia when administered as a bolus and nonsegmental systemic analgesia when administered as a continuous infusion. This finding may help resolve the long-standing controversy surrounding the site of action of epidural fentanyl.
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Anesthesia and analgesia · Nov 2003
Randomized Controlled Trial Clinical TrialThe use of a continuous popliteal sciatic nerve block after surgery involving the foot and ankle: does it improve the quality of recovery?
Popliteal sciatic nerve block is a commonly used technique for surgery involving the foot and ankle. However, pain can be difficult to control as the local anesthetic block wears off. Therefore, we hypothesized that extending the block by using a continuous infusion of bupivacaine (0.25%) would provide improved pain management and might facilitate the recovery process after foot or ankle surgery. In this randomized, double-blinded, placebo-controlled study, 24 consenting patients undergoing foot or ankle surgery with a standardized general anesthetic technique were studied. Before surgery, a popliteal sciatic nerve block was performed in all patients with an 18-gauge Tuohy epidural needle and a peripheral nerve stimulator. After injection of bupivacaine 0.25% 30 mL and placement of a 20-gauge catheter, patients were randomly assigned to receive either 0.9% saline (control) or bupivacaine 0.25% at a constant rate of 5 mL/h for up to 48 h after surgery. An 11-point verbal rating scale (0 = no pain to 10 = worst pain imaginable) was used to assess the severity of pain. Opioid analgesic use was recorded at specific time intervals after surgery. Follow-up evaluations were performed at 24 h, 48 h, 72 h, and 1 week after surgery to assess pain scores, as well as patient satisfaction with their pain management and quality of recovery, by using a 100-point verbal rating scale (1 = highly dissatisfied to 100 = highly satisfied). In the bupivacaine group, there was a statistically significant reduction in the maximal pain scores (>50%) and in opioid use (>60%) during the postoperative period compared with the control group. Patient satisfaction with postoperative pain management (95 +/- 3 versus 77 +/- 13) and quality of recovery (96 +/- 7 versus 83 +/- 14) was significantly improved in the bupivacaine group (versus control). In addition, 40% of the patients in the bupivacaine group (versus none in the control group) were able to be discharged home on the day of surgery (P = 0.087). In conclusion, a continuous infusion of bupivacaine 0.25% decreased postoperative pain and the need for opioid analgesic rescue medication after orthopedic surgery involving the foot and ankle, leading to improved patient satisfaction and quality of recovery. ⋯ A continuous infusion of bupivacaine 0.25% (versus saline) at the popliteal fossa by using a simple elastomeric pump is an effective method of decreasing postoperative pain, reducing the opioid analgesic requirement, and increasing patient satisfaction with pain management after orthopedic surgery involving the foot and ankle. More importantly, the use of the continuous sciatic nerve block in the popliteal fossa facilitated an earlier discharge after lower extremity surgery.
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Anesthesia and analgesia · Nov 2003
Randomized Controlled Trial Clinical TrialPretreatment with small-dose ketamine reduces withdrawal movements associated with injection of rocuronium in pediatric patients.
We evaluated the pretreatment of small-dose of ketamine or normal saline in the reduction of withdrawal movements induced by rocuronium injection. One-hundred pediatric patients (aged 1-6 yr) were randomly assigned into 2 groups. A 22-gauge IV cannula was inserted into the dorsum of the hand, and ketamine 0.2 mg/kg or normal saline was given, followed by a 5 mg/kg thiopental injection 10 s later. IV rocuronium (0.8 mg/kg) was injected over 5 s. The patient's response to rocuronium injection was graded by using a four-point scale in a double-blinded manner. We observed that the incidence of withdrawal movements was 83% in the saline group and 27% in patients pretreated with ketamine (P < 0.05). Some patients in both groups developed skin erythema at the site of injection. We conclude that pretreatment with small-dose ketamine significantly attenuates withdrawal movements associated with IV injection of rocuronium in pediatric patients anesthetized with thiopental. ⋯ Pretreatment with small-dose ketamine 0.2 mg/kg provides a simple and safe means of reducing the incidence of withdrawal movements induced by the injection of rocuronium, a short-acting nondepolarizing muscle relaxant.
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Anesthesia and analgesia · Nov 2003
Randomized Controlled Trial Comparative Study Clinical TrialOxygenation using tidal volume breathing after maximal exhalation.
We compared, in volunteers, the oxygenation achieved by tidal volume breathing (TVB) over a 3-min period after maximal exhalation with that achieved by TVB alone. Twenty-three healthy volunteers underwent the two breathing techniques in a randomized order. A circle absorber system with an oxygen flow of 10 L/min was used. The end-expiratory oxygen concentration (EEO(2)) was monitored at 15-s intervals up to 3 min. TVB after maximal exhalation produced EEO(2) values of 68% +/- 5%, 75% +/- 5%, and 79% +/- 4% at 30, 45, and 60 s, respectively, which were significantly larger (P < 0.05) than the corresponding values obtained with TVB alone (58% +/- 5%, 66% +/- 6%, and 71% +/- 5%, respectively). In both techniques, the EEO(2) increased exponentially, with time constants of 35 s during TVB after maximal exhalation versus 58 s during TVB without prior maximal exhalation. In conclusion, maximal exhalation before TVB can hasten preoxygenation by decreasing the nitrogen content of the functional residual capacity, with a consequent increase of EEO(2) to approximately 70% in 30 s and 80% in 60 s. ⋯ Oxygenation by using maximal exhalation before tidal volume breathing produced a significantly faster increase in end-expiratory oxygen concentration than oxygenation with tidal volume breathing alone.
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Anesthesia and analgesia · Nov 2003
Clinical TrialThe effects of isoflurane-induced electroencephalographic burst suppression on cerebral blood flow velocity and cerebral oxygen extraction during cardiopulmonary bypass.
We investigated the effects of isoflurane-induced burst suppression, monitored with electroencephalography (EEG), on cerebral blood flow velocity (CBFV), cerebral oxygen extraction (COE), and autoregulation in 16 patients undergoing cardiac surgery. The experimental procedure was performed during nonpulsatile cardiopulmonary bypass (CPB) with mild hypothermia (32 degrees C) in fentanyl-anesthestized patients. Middle cerebral artery transcranial Doppler flow velocity, right jugular vein bulb oxygen saturation, and jugular venous pressure (JVP) were continuously measured. Autoregulation was tested during changes in mean arterial blood pressure (MAP) within a range of 40-80 mm Hg, induced by sodium nitroprusside and phenylephrine before (control) and during additional isoflurane administration to an EEG burst-suppression level of 6-9/min. Isoflurane induced a 27% decrease in CBFV (P < 0.05) and a 13% decrease in COE (P < 0.05) compared with control. The slope of the positive relationship between CBFV and cerebral perfusion pressure (CPP = MAP - JVP) was steeper with isoflurane (P < 0.05) compared with control, as was the slope of the negative relationship between CPP and COE (P < 0.05). We conclude that burst-suppression doses of isoflurane decrease CBFV and impair autoregulation of cerebral blood flow during mildly hypothermic CPB. Furthermore, during isoflurane administration, blood flow was in excess relative to oxygen demand, indicating a loss of metabolic autoregulation of flow. ⋯ The effects of isoflurane on cerebral blood flow velocity (CBFV) and oxygen extraction (COE) as a function of perfusion pressure were studied. When added to fentanyl anesthesia, isoflurane induced a 27% and 13% decrease in CBFV and COE, respectively. CBFV became more pressure-dependent with isoflurane indicating an impaired autoregulation.