Anesthesia and analgesia
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Anesthesia and analgesia · Feb 2000
Randomized Controlled Trial Clinical TrialThe effects of ketamine on the temporal summation (wind-up) of the R(III) nociceptive flexion reflex and pain in humans.
Animal studies have suggested that the temporal summation of nociceptive inputs might play a significant role in the development of central sensitization (i.e., hyperexcitability of central nociceptive neurons) and hyperalgesia via the activation of N-methyl-D-aspartate receptors. To further analyze these processes in humans, we evaluated the effects of small systemic doses of ketamine on the temporal summation (i.e., wind-up) of both the nociceptive flexion (R(III)) reflex and sensations of pain in six healthy volunteers. The R(III) reflex was recorded from the biceps femoris and was elicited by electrical stimulation of the sural nerve. First, the recruitment (stimulus/response) curve for the reflex was built using stimuli up to the pain tolerance threshold (applied once every 6 s). A series of 15 stimuli was then applied once a second at an intensity of 1.2 times the reflex threshold. These procedures were performed both before and after the randomized IV injection of either 0.15 mg/kg ketamine or a placebo. The R(III) reflex threshold and its recruitment curve were not significantly altered after the injection of ketamine or placebo. By contrast, the significant increases (i.e., wind-up) in both the reflex responses and the sensations of pain observed during the higher frequency stimulation were significantly reduced after the administration of ketamine, but not placebo. This method might be useful for quantifying and analyzing the wind-up phenomenon and, thus, for studying the neurophysiological and pharmacological mechanisms underlying hyperalgesia in humans. ⋯ The wind-up phenomenon (i.e., the progressive increase of the responses induced by repetitive nociceptive stimuli) was characterized in humans by using electrophysiological recordings of the nociceptive flexion reflex. We showed that, as in animals, this phenomenon, which might represent an elementary form of the central sensitization involved in various painful syndromes, depends on the activation of N-methyl-D-aspartate receptors, because it was selectively reduced after the administration of ketamine.
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Anesthesia and analgesia · Feb 2000
Randomized Controlled Trial Comparative Study Clinical TrialOral ketamine/midazolam is superior to intramuscular meperidine, promethazine, and chlorpromazine for pediatric cardiac catheterization.
An IM combination of meperidine, promethazine, and chlorpromazine (DPT) has been given as sedation for pediatric procedures for more than 40 years. We compared this IM combination to oral (PO) ketamine/midazolam in children having cardiac catheterization. A total of 51 children, ages 9 mo to 10 yr, were enrolled and randomized in this double-blinded study. All children received an IM injection at time zero and PO fluid 15 minutes later. We observed acceptance of medication, onset of sedation and sleep, and sedative efficacy. The cardiorespiratory changes were evaluated. Sedation was supplemented with IV propofol as required. Recovery time, parental satisfaction, and patient amnesia were assessed. Ketamine/midazolam given PO was better tolerated (P < 0.0005), had more rapid onset (P < 0.001), and provided superior sedation (P < 0.005). Respiratory rate decreased after IM DPT only. Heart rate and shortening fraction were stable. Oxygen saturation and mean blood pressure decreased minimally in both groups. Supplemental propofol was more frequently required (P < or = 0.02) and in larger doses (P < 0.05) after IM DPT. Parental satisfaction ratings were higher (P < 0.005) and amnesia was more reliably obtained (P = 0.007) with PO ketamine/midazolam. Two patients needed airway support after the PO medication, as did two other patients when PO ketamine/midazolam was supplemented with IV propofol. Although PO ketamine/midazolam provided superior sedation and amnesia compared to IM DPT, this regimen may require the supervision of an anesthesiologist for safe use. ⋯ Oral medication can be superior to IM injections for sedating children with congenital heart disease; however, the safety of all medications remains an issue.
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Anesthesia and analgesia · Feb 2000
Randomized Controlled Trial Clinical TrialRamosetron for preventing postoperative nausea and vomiting in women undergoing gynecological surgery.
In a prospective, randomized, double-blinded, placebo-controlled trial, we evaluated the efficacy of ramosetron at three different doses (0.15, 0.3, and 0.6 mg) for the prevention of postoperative nausea and vomiting (PONV) after gynecological surgery. One hundred twenty women, ASA physical status I or II, aged 21-63 yr, received IV either placebo or ramosetron 0.15, 0.3, or 0.6 mg (n = 30 of each) at the completion of surgery. A standard general anesthetic technique and postoperative analgesia were used. A complete response, defined as no PONV and no need for another rescue antiemetic, during 0-3 h after anesthesia occurred in 40%, 47%, 87%, and 90% of patients who had received placebo and ramosetron 0.15, 0.3, and 0.6 mg, respectively. Corresponding results during 3-24 h after anesthesia were 43%, 50%, 87%, and 90%, and 24-48 h after anesthesia were 50%, 53%, 90%, and 93% (P < 0.05). Patients who had received ramosetron 0.3 or 0.6 mg were satisfied compared with those who had received placebo (P < 0.05). There were no serious clinical adverse events caused by the study drug in any of the groups. In conclusion, ramosetron 0.3 mg is an effective antiemetic for preventing PONV during 0-48 h after anesthesia in female patients undergoing gynecological surgery. Increasing the dose to 0.6 mg provided no further benefit. ⋯ This randomized, double-blinded, placebo-controlled trial in 120 women found the effective dose of ramosetron for preventing postoperative nausea and vomiting after gynecological surgery to be 0.3 mg.
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Anesthesia and analgesia · Feb 2000
Randomized Controlled Trial Clinical TrialForced-air warming decreases vasodilator requirement after coronary artery bypass surgery.
Postoperative hypothermia is common and associated with adverse hemodynamic consequences, including adrenergically mediated systemic vasoconstriction and hypertension. Hypothermia is also a known predictor of dysrhythmias and myocardial ischemia in high-risk patients. We describe a prospective, randomized trial designed to test the hypothesis that forced-air warming (FAW) provides improved hemodynamic variables after coronary artery bypass graft. ⋯ In conclusion, aggressive cutaneous warming with FAW results in a higher mean skin temperature and a decreased requirement for vasodilator therapy in hypothermic patients after cardiac surgery. This most likely reflects attenuation of the adrenergic response or opening of cutaneous vascular beds as a result of surface warming. IMPLICATIONS Forced-air warming after cardiac surgery decreases the requirement for vasodilator drugs and may be beneficial in maintaining hemodynamic variables within predefined limits.
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Anesthesia and analgesia · Feb 2000
Randomized Controlled Trial Clinical TrialSufentanil does not prolong the duration of analgesia in a mepivacaine brachial plexus block: a dose response study.
To date, results of studies evaluating the efficacy of opioids and local anesthetic combinations in the brachial plexus are inconclusive. We examined whether increasing sufentanil in doses of 5, 10, and 20 microg decreased onset time or increased duration of an axillary brachial plexus block. Ninety-two patients scheduled for carpal tunnel release under axillary brachial plexus block were enrolled in the study. Patients were randomized to receive axillary plexus block with 40 mL 1.5% mepivacaine and saline (Group 1), sufentanil 5 microg (Group 2), 10 microg (Group 3), or 20 microg (Group 4). Onset and duration of sensory and motor block were measured. Opioid-related side effects were recorded. The addition of sufentanil did not improve speed of onset or increase the duration of sensory or motor block. Paradoxically, duration of sensory and motor block was longest in the control group: sensory, 241 min (188-284) and motor, 234 min (128-305), and decreased with increasing doses of sufentanil in Group 4: sensory, 216 min (115-315) and motor, 172 min (115-260) (P < 0.05). Side effects occurred in 55% of patients belonging to Groups 2 and 4, and in 60% of the patients in Group 3. In contrast, only 10% of the patients reported side effects in the control group. We conclude that sufentanil added to mepivacaine does not increase the onset or prolong the duration of an axillary plexus block. Furthermore, the addition of sufentanil was associated with a frequent incidence of side effects. ⋯ This study demonstrates that the addition of sufentanil in a dose-dependent manner to 1.5% mepivacaine in the axillary plexus does not improve onset or duration of blockade, and that this admixture is associated with an increased incidence of side effects.