Anesthesia and analgesia
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Anesthesia and analgesia · Mar 1999
Randomized Controlled Trial Comparative Study Clinical TrialRemifentanil administration during monitored anesthesia care: are intermittent boluses an effective alternative to a continuous infusion?
This randomized, double-blind study was designed to evaluate the analgesic effectiveness and respiratory stability of remifentanil when administered as intermittent bolus injections, a variable-rate infusion, or a combination of a constant basal infusion supplemented with intermittent boluses during monitored anesthesia care (MAC). Forty-five patients undergoing extracorporeal shock wave lithotripsy (ESWL) procedures were randomly assigned to one of the three modes of remifentanil administration. All patients received midazolam 2 mg i.v., followed by a propofol infusion at 50 microg x kg(-1) x min(-1). Two minutes before administering a series of test shock waves: Group I received a remifentanil infusion of 0.1 microg x kg(-1) x min(-1), and a saline bolus (5 mL); Group II received a saline infusion and a remifentanil bolus (25 microg in 5 mL); and Group III received a remifentanil infusion of 0.05 microg x kg(-1) x min(-1), and a remifentanil bolus (12.5 microg in 5 mL). The average pain intensity was scored on an 11-point scale, with 0 = no pain to 10 = severe pain. During the ESWL procedure, pain was treated by increasing the study drug infusion rate by 25%-50% and administering 5-mL bolus injections of the study medication in Groups I (saline) and II (remifentanil 25 microg). In Group III, intermittent 5-mL boluses (remifentanil 12.5 microg) were administered as needed. Patients in Groups II and III reported lower pain scores in response to the test shocks. Significantly more remifentanil was administered in Group I (379 +/- 207 microg) than in Group II (201 +/- 136 microg). However, more interventions were required for the treatment of intraoperative pain in the intermittent bolus group (Group II). When remifentanil is administered as the analgesic component of a MAC technique, these data support the use of intermittent bolus doses (12.5-25 microg) alone or in combination with a basal infusion (0.05 microg x kg(-1) x min(-1)) as alternatives to a variable-rate continuous infusion. ⋯ In this study, three different modes of remifentanil administration were used during monitored anesthesia care for extracorporeal shock wave lithotripsy procedures. These results suggest that using intermittent bolus injections of remifentanil (25 microg) or a continuous infusion (0.05 microg x kg(-1) x min(-1)) supplemented with intermittent bolus (12.5 microg) injections may be more effective than a variable-rate infusion of remifentanil during propofol sedation.
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Anesthesia and analgesia · Mar 1999
Randomized Controlled Trial Clinical TrialAdenosine reduces secondary hyperalgesia in two human models of cutaneous inflammatory pain.
Secondary hyperalgesia is characterized by increased sensitivity to noxious mechanical stimuli in the area surrounding injured skin. The pathophysiological mechanisms involve increased excitability of second-order neurons located in the spinal cord, i.e., central sensitization. The mechanisms behind this phenomenon may be of importance in clinical pain, including neuropathic pain. To study the effects of systemic infusion of the endogenous compound adenosine (ADO) on sensory function, a superficial cutaneous burn injury was induced by the 4-min topical application of mustard oil or by heat (47 degrees C for 7 min) during i.v. ADO infusion (60 microg x kg(-1) x min(-1)). Healthy human subjects (n = 10 for each model) were tested, using a blinded, placebo-controlled procedure. The area of secondary hyperalgesia, as well as tactile and thermal sensory function, was tested using psychophysical methods during and after treatments. ADO significantly reduced the area of secondary hyperalgesia in both models. The maximal reduction compared with placebo was 58% +/- 20% (heat burn) and 39% +/- 13% (mustard oil burn). No other differences in sensory function were observed. The results are interpreted as an ADO-induced modulatory effect on the mechanisms of central sensitization. ⋯ We tested the effects of adenosine on the development of increased sensitivity in the skin surrounding a superficial skin injury in humans. A superficial skin bum was induced with a chemical irritant or heat. The results show that adenosine reduces the skin area with increased sensitivity surrounding the injury.
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Anesthesia and analgesia · Mar 1999
Randomized Controlled Trial Comparative Study Clinical TrialArterial oxygenation during one-lung ventilation: combined versus general anesthesia.
The optimal anesthetic management of patients undergoing thoracotomy for pulmonary resection has not been definitely determined. We evaluated whether general i.v. anesthesia (propofol-fentanyl) provides superior PaO2 during one-lung ventilation (OLV) compared with thoracic epidural anesthesia (TEA) with supplemental local and general anesthetics. We studied 60 patients who had prolonged periods of OLV for elective thoracic surgery for lung cancer and who were prospectively randomized into two groups. In 30 patients (GA group), fentanyl/propofol/rocuronium anesthesia was used. Another 30 patients (TEA group) were anesthetized with propofol/rocuronium/epidural thoracic bupivacaine 0.5%. A double-lumen endotracheal tube was inserted, and mechanical ventilation with 100% oxygen was used during the entire study. Arterial and venous blood gases were recorded before surgery in a lateral position with two-lung ventilation, 15 and 30 min after OLV (OLV + 15 and OLV + 30, respectively) in all patients. We measured PaO2, venous central oxygen tension, arterial and central venous oxygen saturation, venous admixture percentage (Qs/Qt%), and arterial and central venous oxygen content. The mean values for PaO2 during OLV in the GA group after 15 min (175 mm Hg) and 30 min (182 mm Hg) were significantly (P < 0.05) higher compared with the TEA group (120 and 118 mm Hg, respectively). Furthermore, Qs/Qt% was significantly (P < 0.05) increased in the TEA group during OLV. There were no other significant differences. We conclude that using the TEA regimen is associated with a lower PaO2 and a larger intrapulmonary shunt during OLV than with total i.v. anesthesia alone. ⋯ Sixty patients undergoing elective lung surgery during a prolonged period of intraoperative one-lung ventilation were studied and randomized to receive general i.v. anesthesia or general i.v. anesthesia combined with thoracic epidural anesthesia. The arterial oxygenation in the first group was better than that in the second group during one-lung ventilation.
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Anesthesia and analgesia · Mar 1999
Randomized Controlled Trial Clinical TrialThe intubating laryngeal mask airway with and without fiberoptic guidance.
We conducted this feasibility study using the intubating laryngeal mask airway (ILMA) and a polyvinyl chloride tracheal tube to compare success rates, hemodynamic effects, and postoperative morbidity with two methods of tracheal intubation. After ethics approval and informed consent, 90 healthy ASA physical status I or II women with normal airways were enrolled in the randomized, controlled study. After a standardized inhaled anesthesia induction protocol, tracheal intubations using ILMA with fiberoptic guidance (ILMA-FOB) and ILMA inserted blindly without fiberoptic guidance (ILMA-Blind) were compared with the control group of direct laryngoscopy (laryngoscopy group). All 90 patients were successfully ventilated. For tracheal intubation, success rates were equal in all three groups (97%). Total intubation times were longer for the ILMA-FOB group (77 s versus 48.5 s for laryngoscopy and 53.5 s for ILMA-Blind). The laryngoscopy group had a larger increase in mean arterial blood pressure to tracheal intubation. There were no differences in postoperative sore throat or hoarseness among the groups. In conclusion, success rates are equally high for tracheal intubation using ILMA-Blind and ILMA-FOB techniques in women with normal airways. ⋯ The intubating laryngeal mask airway (ILMA) can be used as a primary airway for oxygenation and ventilation. Both methods of tracheal intubation using the ILMA were equally successful. Postoperative morbidity in the ILMA groups was similar to that in the laryngoscopy group. For women with normal airways, both the ILMA inserted blindly and the ILMA with fiberoptic guidance are suitable alternatives to laryngoscopy for tracheal intubation.
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Anesthesia and analgesia · Mar 1999
Pretreatment with dexmedetomidine: altered indices of anesthetic depth for halothane in the neuraxis of cats.
The sedative and anesthetic-sparing ability of the alpha2-adrenergic agonist dexmedetomidine is well documented. In this study, we identified the effects of halothane, with and without dexmedetomidine, on hemodynamic and electroencephalographic (EEG) variables and quantified the concentration of halothane resulting in various anesthetic depth indices mediated through the central nervous system (CNS) in chronically instrumented cats. Halothane was given alone or after dexmedetomidine (15 microg/kg p.o.). In both groups, four indices of anesthetic depth--minimum alveolar anesthetic concentration (MAC; no movement to noxious stimuli), MAC(BAR) (no autonomic response to noxious stimuli), MAC(BS) (EEG burst suppression), and MAC(ISOELECTRIC) (EEG isoelectricity)--were determined. Halothane decreased arterial blood pressure, heart rate, and higher frequency components of the EEG before the onset of burst suppression and isoelectricity. Dexmedetomidine pretreatment augmented the actions of halothane on arterial pressure, heart rate, and the EEG. Dexmedetomidine reduced the halothane concentrations resulting in MAC (from 1.22% +/- 0.06% to 0.89% +/- 0.08%) and MAC(BAR) (from 1.81% +/- 0.05% to 1.1% +/- 0.10%), but not those resulting in MAC(BS) (3.01% +/- 0.17% vs 3.14% +/- 0.10%) or MAC(ISOELECTRIC) (4.39% +/- 0.26% vs 4.65% +/- 0.12%). These results suggest that dexmedetomidine does not alter various CNS-mediated indices of anesthetic action to equivalent degrees and that there are dissimilar degrees of an anesthetic-sparing action at different levels of the neuraxis. ⋯ The anesthetic adjuvant dexmedetomidine seems to differentially alter central nervous system-mediated indices of anesthetic action. Lower brainstem or spinal determinants of anesthetic depth (movement and hemodynamic responses) are more attenuated than those of higher brain functions, such as the electroencephalogram.