[Remifentanil and eye surgery. A randomized, clinical comparison of propofol/remifentanil anesthesia and propofol/fentanyl/alfentanil anesthesia]

INTRODUCTION

The aim of this study was to investigate how many patients, after anesthesia with either propofol/remifentanil or propofol/fentanyl/alfentanil, within 20 minutes from the end of surgery could be transferred directly to the general ward. The number of undesired preoperative incidents, the anesthetists', the surgeons', and the patients' evaluations of the anesthesia were registered. An evaluation of the economic consequences of the two methods was also intended.

MATERIAL AND METHODS

The study was clinically controlled, randomised, and partly blinded. A total of 80 patients undergoing eye surgery were recruited. The patients were scored 10, 15, and 20 minutes after the end of surgery according to a modified Aldrete score. With sufficient awakening score, the patients were transferred to the general ward.

RESULTS

Thirty-six patients in each group underwent the examination. In the propofol/remifentanil-group 31 (86%) could be transferred to the general ward compared to 15 (42%) in the proponol/fentanyl/alfentanil-group. In the propofol/remifentanil-group there were less reactions to the start of surgery, more episodes with preoperative hypotension and postoperative shivering. Otherwise there were no differences between the groups. It was estimated that the additional expenses for medcine were by far outweighed by the lower costs postoperatively.

DISCUSSION

With a propofol/remifentanil-anesthesia, the patients had a predictably short awakening time, so they could be transferred directly to the general ward. This may, especially in ambulatory surgery, mean cost savings and perhaps higher patient satisfaction.

Simultaneous assessment of drug interactions with low- and high-extraction opioids: application to parecoxib effects on the pharmacokinetics and pharmacodynamics of fentanyl and alfentanil

BACKGROUND

Parecoxib is a parenteral cyclooxygenase-2 (COX-2) inhibitor intended for perioperative analgesia. It is an inactive prodrug hydrolyzed in vivo to the active inhibitor valdecoxib, a substrate for hepatic cytochrome P450 3A4 (CYP3A4); hence, a potential exists for metabolic interactions with other CYP3A substrates. This study determined the effects of parecoxib on the pharmacokinetics and pharmacodynamics of the CYP3A substrates fentanyl and alfentanil compared with the CYP3A inhibitor troleandomycin. Alfentanil is a low-extraction drug with a clearance that is highly susceptible to drug interactions; fentanyl is a high-extraction drug and, thus, is theoretically less vulnerable. We therefore also tested the hypothesis that the extraction ratio influences the consequence of altered hepatic metabolism of these opioids.

METHODS

After Institutional Review Board-approved, written, informed consent was obtained, 12 22- to 40-yr-old healthy volunteers were enrolled in the study. The protocol was a randomized, double-blinded, balanced, placebo-controlled, three-session (placebo, parecoxib, or troleandomycin pretreatment) crossover. Subjects received both alfentanil (15 microg/kg) and fentanyl (5 microg/kg; 15-min intravenous infusion) 1 h after placebo, parecoxib (40 mg intravenously every 12 h), or troleandomycin (every 6 h). Study sessions were separated by 7 or more days. Opioid concentrations in venous blood were determined by liquid chromatography-mass spectrometry. Pharmacokinetic parameters were determined by noncompartmental analysis. Opioid effects were determined by pupillometry, respiratory rate, and Visual Analog Scale scores.

RESULTS

There were no significant differences between the placebo and parecoxib treatments in alfentanil or fentanyl plasma concentration, maximum observed plasma concentration, area under the plasma time-concentration time curve, clearance, elimination half-life, or volume of distribution. However, disposition of alfentanil, and to a lesser extent fentanyl, was significantly altered by troleandomycin. Clearances were reduced to 12% (0.64 +/- 0.25 ml. kg-1. min-1) and 61% (9.35 +/- 3.07) of control (5.53 +/- 2.16 and 15.3 +/- 5.0) for alfentanil and fentanyl (P < 0.001). Pupil diameter versus time curves were similar between placebo and parecoxib treatments but were significantly different after troleandomycin.

CONCLUSIONS

Single-dose parecoxib does not alter fentanyl or alfentanil disposition or clinical effects and does not appear to cause significant CYP3A drug interactions. CYP3A inhibition decreases alfentanil clearance more than fentanyl clearance, confirming that the extraction ratio influences the consequence of altered hepatic drug metabolism. Modified cassette, or "cocktail," dosing is useful for assessing drug interactions in humans.

Small doses of remifentanil and alfetanil in continuous total intravenous anesthesia in major abdominal surgery. A double blind comparison

AIM

The purpose of this study was to test the safety and efficacy of small doses of remifentanil and alfentanil in a continuous total intravenous anesthesia technique for patients undergoing major abdominal surgery.

METHODS

Sixty patients were enrolled in the study, and received in a double blind fashion either remifentanil (0.1 microg/kg/min) or alfentanil (alfentanil 0.75 microg/kg/min) in association with propofol (12 mg/kg/h at induction; 6-9 mg/kg/h for maintenance) and cisatracurium. Hemodynamic data, hypnosis monitoring data (Bispectral Index Score), ventilatory parameters and settings, drug utilisation were monitored during stress moments and during all the intraoperative period. Patients were evaluated also in the first 6 postoperative hours.

RESULTS

Mean amount of propofol for induction (BIS<60) was lower in the remifentanil group than in the alfentanil group. Significantly fewer patients receiving remifentanil responded to intubation in comparison with patients receiving alfentanil in terms of non invasive blood pressure (>30 mmHg) and heart rate variations. Significantly more patients receiving alfentanil had 1 or more responses to surgery. Incidence of hypotension was significantly higher in patients receiving remifentanil. There were no differences between the 2 groups in the times for spontaneous respiration, adequate respiration, adequate responsivness (OAA/s=5) and discharge from the recovery room. Time to extubation resulted slightly shorter (p<0.05) in patients who received remifentanil.

CONCLUSIONS

The use of remifentanil and alfentanil in association with propofol, in a continuous infusion total intravenous anesthesia technique, demonstrated to be safe and reliable strategies.

Remifentanil vs. alfentanil for direct laryngoscopy: a randomized study comparing two total intravenous anaesthesia techniques. TIVA for direct laryngoscopy

The ideal anaesthesia for direct laryngoscopy is profound and yet brief. The present study sought to determine whether a new anaesthetic technique based on infusion of the ultra short-acting opioid remifentanil was superior to our routine alfentanil multiple-dose technique in terms of haemodynamic stability, stress responses and recovery. A total of 58 patients were randomized to receive propofol and either remifentanil or alfentanil as part of a total intravenous anaesthesia. In the remifentanil group, systolic blood pressure during anaesthesia remained significantly lower than baseline values, while it increased significantly in the alfentanil group. None of the patients receiving remifentanil showed stress responses (hypertension, tachycardia, somatic or autonomic responses), compared to 22 patients (79%) in the alfentanil group (P < 0.0001). In the remifentanil group, hypotension or bradycardia requiring intervention arose in 5 (18%) and 3 patients (11%); neither response was seen in the alfentanil group. The period from the end of propofol infusion until extubation was 5 min longer in the remifentanil group (P < 0.0001), whereas the time from extubation until discharge was similar in the two groups. Thus, neither technique showed sufficient haemodynamic stability, and further studies are needed to determine optimal dosages of propofol and opioid.

Opioid-induced respiratory depression is associated with increased tidal volume variability

BACKGROUND AND OBJECTIVE

mu-agonistic opioids cause concentration-dependent hypoventilation and increased irregularity of breathing. The aim was to quantify opioid-induced irregularity of breathing and to investigate its time-course during and after an opioid infusion, and its ability to predict the severity of respiratory depression.

METHODS

Twenty-three patients breathing spontaneously via a continuous positive airway pressure (CPAP) mask received an intravenous (i.v.) infusion of alfentanil (2.3 microg kg(-1) min(-1), 14 patients) or pirinitramide (piritramide) (17.9 microg kg(-1) min(-1), nine patients) until either a cumulative dose of 70 microg kg(-1) for alfentanil or 500 microg kg(-1) for pirinitramide had been achieved or the infusion had to be stopped for safety reasons. Tidal volumes (VT) and minute ventilation were measured with an anaesthesia workstation. For every 20 breaths, the quartile coefficient was calculated (Qeff20V(T)).

RESULTS

Both the decrease of minute volume and the increase of Qeff20V(T) during and after opioid infusion were highly significant (P < 0.001, ANOVA). Patients in which the alfentanil infusion had to be terminated prematurely had lower minute volumes (P = 0.002, t-test) and higher Qeff20V(T) (P = 0.034, t-test) than those who received the complete dose. Changes in the regularity of breathing measured as Qeff20V(T) parallel those of minute ventilation during and after opioid infusion.

CONCLUSIONS

Opioids cause a more complicated disturbance of the control of respiration than a mere resetting to higher PCO2. Furthermore, Qeff20V(T) appears to predict the severity of opioid-induced respiratory depression.

Cold allodynia and hyperalgesia in neuropathic pain: the effect of N-methyl-D-aspartate (NMDA) receptor antagonist ketamine--a double-blind, cross-over comparison with alfentanil and placebo

Cold allodynia and hyperalgesia are frequent clinical findings in patients with neuropathic pain. While there have been several clinical studies showing the involvement of central sensitization mechanisms and N-methyl-D-aspartate (NMDA) receptor activation in mechanical allodynia/hyperalgesia and ongoing pain, the mechanisms of thermal allodynia and hyperalgesia have received less attention. The aim of the present study was to examine the effect of the NMDA-receptor antagonist ketamine on thermal allodynia/hyperalgesia, ongoing pain and mechanical allodynia/hyperalgesia in patients with neuropathic pain (11 patients with post-traumatic neuralgia and one patient with post-herpetic neuralgia). All the patients were known to suffer from severe cold allodynia (cold pain detection threshold (CPDT): 23.8 degrees C, median value). The mu-opioid agonist alfentanil was used as an active control. The study design was double-blind and placebo-controlled and the drugs were administered i.v. (bolus dose and infusion). CPDT in the asymptomatic contralateral area was found to be significantly decreased (cold allodynia) compared to CPDT in site- and age-matched normal controls. Heat pain detection thresholds were found to be normal and no consistent heat hyperalgesia occurred. Alfentanil significantly reduced cold allodynia (by increasing CPDT) in symptomatic area (P=0.0076). Ketamine did not significantly increase the threshold. Significant and marked reductions of hyperalgesia to cold (visual analogue score at threshold value) were seen following both alfentanil (4.5 before, 1.4 after, median value) and ketamine (6.8 before, 0.4 after, median value). Alfentanil and ketamine also significantly reduced ongoing pain and mechanical hyperalgesia. It is concluded that NMDA-receptor mediated central sensitization is involved in cold hyperalgesia, but since CPDT remained unaltered, it is likely that other mechanisms are present.

Postdelivery of alfentanil and ketamine has no effect on intradermal capsaicin-induced pain and hyperalgesia

OBJECTIVE

The predelivery of intravenous alfentanil (a mu opioid agonist) and ketamine (an -methyl d-aspartate antagonist) has recently been shown to decrease the secondary hyperalgesia induced by intradermal capsaicin. The focus of this study was to determine the effects of the postdelivery of intravenous alfentanil and ketamine on intradermal capsaicin-induced secondary hyperalgesia.

DESIGN

Double-blind, placebo-controlled, randomized, crossover study. Five minutes after an intradermal capsaicin injection, alfentanil and ketamine infusions were administered for a target plasma concentration of 75 ng/ml for alfentanil and 150 ng/ml for ketamine or placebo equivalent using a computer-controlled infusion pump and maintained for the remainder of the study. The investigator recorded the magnitude of the pain score at the time of injection and at 5-minute intervals. Fifteen minutes after the intradermal capsaicin injection, the region of secondary hyperalgesia and flare response was determined.

RESULTS

Alfentanil and ketamine plasma levels targeted after injection of intradermal capsaicin had no significant effect on pain scores, flare response, or secondary hyperalgesia.

CONCLUSIONS

Consistent with animal studies on preemptive analgesia, this study demonstrates that alfentanil and ketamine have a differential effect when delivered before and after a painful stimulus. Because of the differential effect seen, future studies on the pharmacology of human experimental pain should evaluate both predrug and postdrug delivery.

Patient-controlled sedation versus intravenous sedation for colonoscopy in elderly patients: a prospective randomized controlled trial

BACKGROUND

A prospective randomized trial was conducted to compare the safety, effectiveness, and patient acceptance of patient-controlled sedation and intravenous sedation for colonoscopy in a group of elderly patients undergoing outpatient colonoscopy.

METHODS

One hundred patients over 65 years of age were recruited and randomized to patient-controlled sedation (n = 50) or intravenous sedation (n = 50) groups by means of computer-generated numbers. In the patient-controlled sedation group, a mixture of propofol and alfentanil was delivered by means of a patient-controlled pump; each bolus delivered 4.8 mg propofol and 12 microg alfentanil. No loading dose was used and the lockout time was set at zero. In the intravenous sedation group, fixed doses of diazemuls (0.1 mg/kg) and meperidine (0.5 mg/kg) were given with further increases in dosages administered at the discretion of the endoscopist. Outcome measures assessed included cardiopulmonary complications, recovery time, pain score, and satisfaction score.

RESULTS

The mean (SD) age of patients in the patient-controlled sedation and intravenous sedation groups were, respectively, 72.4 years (5.3) and 73.5 years (6.1). The mean dose of propofol consumed in the patient-controlled sedation group was 0.79 (0.46) mg/kg. The mean doses of diazemuls and meperidine consumed in intravenous sedation group were, respectively, 5.8 (1.3) mg and 30.1 (6.8) mg. Hypotension occurred in 2 (4%) patients in the patient-controlled sedation group and 14 (28%) in the intravenous sedation group (p < 0.01). Oxygen desaturation was recorded for 4 patients (8%) in the intravenous sedation group. The median (interquartile range [IQR]) recovery time was significantly shorter in the patient-controlled sedation group compared with the intravenous sedation group (respectively, 0 minutes [IQR 0-5] vs. 5 minutes [IQR 5-10]; p < 0.01). There were no statistically significant differences between groups for pain and satisfaction scores.

CONCLUSIONS

Patient-controlled sedation appears to be safer than intravenous sedation, with comparable effectiveness and acceptance, in elderly patients undergoing elective outpatient colonoscopy.

Time course of cognitive recovery after propofol anaesthesia: a level of processing approach

The aim of this study was to investigate the time course of recovery of verbal memory after general anaesthesia, as a function of the level (shallow or deep) of processing induced at the time of encoding. Thirty-one patients anaesthetized with propofol and alfentanil were compared with 28 control patients receiving only alfentanil. Memory functions were assessed the day before and 1, 6 and 24 hr after operation. Results show that for the anaesthetized group, shallow processing was impaired for 6 hr after surgery whereas the deeper processing was not recovered even at 24 hr. In addition, no specific effect of age was found.

Mu-receptor agonism with alfentanil increases striatal dopamine D2 receptor binding in man

Animal studies indicate that mu-opioids indirectly modulate neurotransmission in the nigrostriatal dopaminergic pathway. We used positron emission tomography (PET) to study the effects of alfentanil (a mu-opioid receptor agonist) on striatal dopamine D2 receptor binding in eight healthy male volunteers. D2 receptor binding was determined by using [(11)C]raclopride as radioligand. Each subject underwent two PET sessions on the same day, the first without the drug (control) and the second during alfentanil infusion. Alfentanil was administered as target-controlled infusion to maintain pseudo steady-state plasma concentration of 80 ng/ml throughout the PET session. A freeze lesion model was used for pain testing at the end of both PET sessions. A mechanical pain stimulus of 5 N was rated by the subjects using a visual analog scale. Regions of interest for the putamen, caudate nucleus, and cerebellum were drawn on MRI images and transferred to PET images. Alfentanil increased the binding potential of [(11)C]raclopride in the putamen by 6.0% (P = 0.04) and in the caudate nucleus by 7.4% (P = 0.008). Alfentanil caused a small reduction in respiratory rate (P = 0.046) and oxygen saturation (P < 0.001), and a moderate consistent increase in end-tidal CO(2) (P < 0.001). Pain scores were significantly smaller after alfentanil PET scan (median VAS 9 (0-42) vs. 23.5 (15-52), P = 0.008). These results indicate that pharmacologically relevant concentrations of alfentanil increase D2 dopamine receptor binding in the striatum in man. This increase is assumed to reflect reduced dopamine release.

Postoperative nausea and vomiting after total intravenous anesthesia with propofol and remifentanil or alfentanil: how important is the opioid?

STUDY OBJECTIVE

To compare the frequency and duration of postoperative nausea and vomiting (PONV) following total intravenous anesthesia (TIVA) with propofol and either remifentanil or alfentanil in outpatients undergoing arthroscopic surgery of the extremities.

DESIGN

Randomized, third-party blinded study.

SETTING

University medical center.

PATIENTS

100 ASA physical status I and II patients scheduled for arthroscopic surgery of the knee or shoulder.

INTERVENTIONS

The anesthesia regimen consisted of a bolus followed by continuous infusion of propofol (2 mg/kg followed by 120 microg/kg/min) and the opioid (remifentanil 0.5 microg/kg followed by 0.1 microg/kg/min or alfentanil 10 microg/kg followed by 0.25 microg/kg/min). Patients breathed 100% oxygen spontaneously through a Laryngeal Mask Airway (or an endotracheal tube when medically indicated). Opioids were titrated to maintain blood pressure and heart rate within 20% of baseline and a respiratory rate of 10 to 16 breaths/min. Propofol was titrated downward as low as possible without permitting patient movement.

MEASUREMENTS

Nausea was determined by an 11-point categorical scale and was recorded before surgery and multiple time points thereafter. The times of emetic episodes were recorded. Treatment of PONV was at the discretion of the postanesthesia care unit (PACU) nurses who were blinded to the identity of the opioid used.

MAIN RESULTS

Nausea scores were 0 at all time points in over 70% of the patients in each group. None of the 100 patients vomited while in the hospital, and only one patient required antiemetic therapy.

CONCLUSION

When propofol-based TIVA is used for arthroscopic surgery, short-acting opioids do not significantly affect the risk of PONV.

Effects of low-dose alfentanil administration on central respiratory drive and respiratory pattern in spontaneously breathing ASA 1 patients

The aim of this study was to assess the short-term effects of the administration of low doses of alfentanil on respiratory drive and respiratory pattern. We studied 17 ASA I patients scheduled for minor surgery or endoscopic procedures. During spontaneous ventilation, Respiratory Rate, Tidal Volume, Total Respiratory Cycle, Inspiratory and Expiratory Time, Mean Inspiratory Flow, P0.1, S(a)O(2) and EtCO(2) were all measured. The inspired oxygen concentration was 21% and measurements were made at baseline, 5 min (T1), 10 min (T2) and 15 min (T3) following an intravenous bolus injection 10 microg.kg(-1) alfentanil. The administration of alfentanil produced a significant (p < 0.05) reduction in S(a)O(2), minute volume and P0.1. In ASA I spontaneously breathing patients, the pre-operative administration of low doses of alfentanil can initially reduce the respiratory centre activity leading to a reduction in minute volume and S(a)O(2). We therefore recommend careful monitoring of cardio-respiratory function in ASA I patients, following the administration of alfentanil.

Comparison of alfentanil and morphine in the prehospital treatment of patients with acute ischaemic-type chest pain

Patients with acute myocardial ischaemic pain would benefit from rapid pain relief. The clinical usefulness of alfentanil, which has a rapid onset of action, was therefore assessed as the initial pain relieving opioid in patients suffering from acute myocardial ischaemic pain. The effects of alfentanil were compared with those of morphine in the prehospital treatment of 40 haemodynamically stable patients suffering from acute ischaemic-type chest pain. After initial assessment, the patients were given either 0.5 mg alfentanil or 5 mg morphine intravenously in a randomized double-blind fashion. The dose was repeated 2 minutes later if severe pain persisted. Arterial pressure, heart rate, respiratory rate and pain expressed on a visual analogue scale was measured before and at 2, 4, 6, 10 and 15 minutes after administration of drugs. After randomization, four patients were excluded. Sixteen patients received alfentanil and 20 patients morphine. Pain relief was faster (p < 0.005) in the alfentanil group than in the morphine group. Alfentanil was found to provide effective analgesia during the follow-up period of 15 minutes. No haemodynamic or respiratory side effects occurred. It is concluded that alfentanil is an effective analgesic in the prehospital treatment of myocardial ischaemic pain.

Relative sensitivity to alfentanil and reliability of current perception threshold vs von Frey tactile stimulation and thermal sensory testing

Recent technological advances claim to allow quantitative measurement of the functional integrity of both large and small diameter sensory nerve fibers using the current perception threshold (CPT) sensory testing device. This device has yet to be validated against the corresponding gold standard references for sensory testing (thermal sensory testing [TST]) and von Frey tactile hair stimulation [VF]) to correlate its evaluation of similar sensory nerve perceptions. A baseline neurosensory examination using the CPT, TST and VF methods was performed on 19 healthy volunteers. Using a randomized, double-blind, placebo-controlled design, each subject received an alfentanil or diphenhydramine (as a placebo control) infusion in separate study sessions. The order of the study sessions was randomized and separated by 1 week. The 3 neurosensory examinations were repeated at 3 different targeted plasma levels of study drug. Changes in neurosensory thresholds were then compared between the 3 methods. All CPT measurements and the cold pain measurement showed a significantly higher degree of variability than the other TST and VF measurements. There appeared to be a correlation between the CPT 5 Hz pain threshold and the TST cold pain and warm sensation; intravenous alfentanil significantly elevated all 3 detection thresholds. In addition, there was no effect of alfentanil on the VF or the CPT 2000 Hz thresholds. However, we did not see the predicted relation between the 250 Hz CPT stimulus and cool sensation. From these studies, there is some evidence that similar fiber tracts may be measured between the CPT, TST, and VF methods, especially with the CPT 5 Hz measures and C-fiber tract activity.

Comparison of five experimental pain tests to measure analgesic effects of alfentanil

BACKGROUND

Several experimental pain models have been used to measure opioid effects in humans. The aim of the current study was to compare the qualities of five frequently used experimental pain tests to measure opioid effects.

METHODS

The increase of electrical, heat, and pressure pain tolerance and the decrease of ice-water and ischemic pain perception was determined at baseline and at four different plasma concentrations of alfentanil (n = 7) administered as target controlled infusion or placebo (n = 7). A linear mixed-effects modeling (NONMEM) was performed to detect drug, placebo, and time effect as well as interindividual and intraindividual variation of effect.

RESULTS

Only the electrical, ice-water, and pressure pain tests are sensitive to assess a concentration-response curve of alfentanil. At a plasma alfentanil concentration of 100 ng/ml, the increase in pain tolerance compared with baseline was 42.0% for electrical pain, 22.2% for pressure pain, and 21.7% for ice-water pain. The slope of the linear concentration-response curve had an interindividual coefficient of variation of 58.3% in electrical pain, 35.6% in pressure pain, and 60.0% in ice-water pain. The residual error including intraindividual variation at an alfentanil concentration of 100 ng/ml was 19.4% for electrical pain, 6.1% for pressure pain, and 13.0% for ice-water pain. Electrical pain was affected by a significant placebo effect, and pressure pain was affected by a significant time effect.

CONCLUSION

Electrical, pressure, and ice-water pain, but not ischemic and heat pain, provide significant concentration-response curves in the clinically relevant range of 200 ng/ml alfentanil or lower. The power to detect a clinically relevant shift of the curve is similar in the three tests. The appropriate test(s) for pharmacodynamic studies should be chosen according to the investigated drug(s) and the study design.

[Factors influencing early extubation after open heart surgery]

The authors have performed a retrospective study in order to review the occurrence and the influencing factors of early extubation among their patients. Those patients who had any severe complication in the immediate postoperative period (pericardial tamponade, low cardiac output syndrome, re-operation due to excessive bleeding, postperfusion lung syndrome, pulmonary edema) preventing early extubation, have been excluded from the study. In the remaining 690 patients early extubation within 8 hours and within 4 hours could be carried out in 525 (76.1%) and 164 cases (23.8%) respectively. Late (beyond 12 hours) extubation occurred in 68 cases (9.9%). Anaesthesia was governed by two different methods. Midazolam and alfentanyl (group 1) were used in 137 cases (19.9%) whilst 553 patients (80.1%) received propofol and alfentanyl (group 2). In group 1 and 2 early extubation was possible in 50.4 and 82.5% respectively (p < 0.0001). In further investigations 27 pre- and intraoperative variables of each patient have been studied and analysed. For statistical analysis authors used the SPSS software including T-test, Mann-Whitney-test, chi-square test and multivariate logistical regression analysis. On the basis of multivariate regression analysis factors influencing early extubation were as follows: age (B = 0.0775; p < 0.001), sex (B = 1.2900; p < 0.001), method of anaesthesia (B = 1.9753; p < 0.001), duration of anaesthesia (B = 0.0053; p < 0.001), re-do operation (B = 1.0482; p = 0.0469) and preoperative congestive heart failure (B = 0.9008; p = 0.0125). Pulmonary diseases known from patient history have not had a deep impact on early extubation. On the basis of our study early extubation has not resulted in an increased number of either the postoperative complications or the occurrence of perioperative myocardial infarction.

Concentration-effect relationship of intravenous alfentanil and ketamine on peripheral neurosensory thresholds, allodynia and hyperalgesia of neuropathic pain

Both mu opioid agonists and N-methyl-D-aspartate (NMDA) receptor antagonists are implicated in the regulation of neuropathic pain in post-nerve injury preclinical pain models. This study characterizes the effects of intravenously infused alfentanil (a mu-receptor agonist) and ketamine (an NMDA-receptor antagonist) on human neuropathic pain states, characterized by allodynia and hyperalgesia. Using diphenhydramine as the placebo, alfentanil and ketamine infusions were given in a randomized double-blind fashion 1 week apart via a computer-controlled infusion (CCI) pump that was programmed to target plasma levels of alfentanil at 25, 50 and 75 ng/ml and ketamine at 50, 100 and 150 ng/ml. At the beginning of each infusion and each targeted plasma level, baseline vital signs, neurosensory testing that included thermal thresholds, thermal pain and von Frey filament thresholds, and spontaneous and evoked pain scores were obtained. Moreover, the areas of allodynia or hyperalgesia to stroking and a 5.18 von Frey filament were mapped at the beginning and the end of each infusion. A total of seven males and five females with post-nerve injury allodynia and hyperalgesia were enrolled in the study. Elevations of cold, warm, hot pain and von Frey tactile thresholds were noted. Dose-dependent increases in cold and cold pain thresholds, and reductions in stroking pain scores were noted in both the alfentanil and the ketamine infusions. In addition, alfentanil showed a statistically significant dose-dependent reduction in both spontaneous and von Frey pain scores. Both the alfentanil and ketamine infusions showed a reduction in the stroking hyperalgesic area and ketamine showed a significant reduction in the von Frey hyperalgesia area. No significant CNS side effects and changes in vital signs were noted. A partial deafferentation state was found in the post-nerve injury patients who presented with allodynia and hyperalgesia. The effects of alfentanil on cold and cold pain thresholds and spontaneous pain scores correlates with previous studies suggesting an opiate central analgesic effect. In addition, the reduction of the hyperalgesic area and evoked pain scores with the alfentanil infusion suggests that opioids may have some peripheral effects in the post-nerve injury patients. Therefore, clinical utilization of opioids with careful titration may be beneficial in post-nerve injury patients with partial deafferentation. With the absence of significant CNS side effects, the ketamine infusion not only demonstrated the well-documented spinal cord mechanism of the NMDA receptor, but the result of the current study also suggests that a peripheral mechanism of NMDA receptor may exist. The relationship between central sensitization and regulation of peripheral NMDA-receptor expression requires further investigation.

Alfentanil-induced epileptiform activity: a simultaneous surface and depth electroencephalographic study in complex partial epilepsy

PURPOSE

Alfentanil is a high potency mu opiate receptor agonist commonly used during presurgical induction of anesthesia. This and other opiate receptor agonists have demonstrated proconvulsant effects in animals, but these properties have been less consistently demonstrated in humans. Most human scalp EEG studies have failed to demonstrate induction of epileptiform activity with these agents, which is inconsistent with findings using intracranial EEG. Simultaneous scalp and depth EEG recordings have yet to be performed in this setting. The relationship between opiate dose and proconvulsant activity is unclear.

METHODS

Simultaneous scalp and depth electrode recordings were performed on five patients with complex partial epilepsy (CPE) who underwent alfentanil anesthesia induction before depth electrode removal. Consecutive equal bolus doses of alfentanil were administered to each patient according to strict time intervals so as to assess their correlation with any induced epileptiform activity.

RESULTS

Epileptiform activity was induced by alfentanil in three of five patients. Two of these patients had electrographic seizures. Epileptiform activity was only detected from the depth electrodes, occurring within 2 min of the first bolus dose in all three cases. Further increase or spread of epileptiform activity did not occur despite cumulative bolus doses of alfentanil.

CONCLUSIONS

Alfentanil is proconvulsant in patients with CPE. Induced seizures may be subclinical and lack a scalp EEG correlate. There is a complex dose-response relationship. Alfentanil induction of anesthesia should be approached with caution in patients with CPE.

Comparison of patient-controlled sedation with propofol and alfentanil for third molar surgery--preliminary results of a pilot study

Propofol and alfentanil are commonly used for sedation and pain control. A preliminary study to compare the usefulness of these drugs was carried out in ten healthy patients requiring bilateral wisdom tooth surgery. The operations were done in two appointments with the patient receiving a different drug on each occasion. Anxiety levels were recorded on visual analogue scales pre and post-operatively. Both agents caused a decrease in anxiety scores, with propofol causing a more significant reduction. Vomiting and nausea with alfentanil was noted in three patients. Propofol also had an amnesic effect which alfentanil did not have. In conclusion, propofol would appear to be the drug of choice within the limitations of this pilot study.

[Premedication and sedation complications during ophthalmic anesthesia]

Sedation allows patients to tolerate unpleasant procedures while maintaining adequate cardiorespiratory function and the ability to respond purposefully to verbal command. For ophthalmic surgery patient's anxiety and discomfort can be relieved during placement of a peribulbar block and during surgery by intravenous sedation. Intravenous sedation should only be administered by an anesthetist. Three different classes of drugs are used for intravenous sedation: analgesics (fentanyl and alfentanil), benzodiazepines (midazolam) and profofol, an intravenous anesthetic. Sedation may result in ventilatory, cardiovascular and neurologic complications. Excessive sedation can induce hypoventilation from central ventilatory depression or airway obstruction. Uncontrolled and unexpected movements of the head could result in major surgical complications. For the prevention of the complications related to sedation the same monitoring as for general anesthesia is essential.

A comparison of patient-controlled analgesia fentanyl and alfentanil for labour analgesia

PURPOSE

To determine the analgesic efficacy of equipotent doses of PCA (patient-controlled analgesia) fentanyl and PCA alfentanil for labour pain.

METHODS

Twenty three, ASA I - II parturients between 32-42 wk gestational age in whom epidural analgesia was contraindicated were randomized to receive PCA fentanyl (Group F)or alfentanil (Group A). Plain numbered vials contained 21 ml fentanyl 50 microg x ml(-1) or alfentanil 500 microg x ml(-1). A one millilitre loading dose was administered. The PCA solution was prepared by diluting 10 ml study drug with 40 ml saline and the PCA pump was programmed to deliver a dose of 2 ml, delay of five minutes and a basal rate of 2 ml x hr(-1). Maternal measurements obtained were hourly drug dose, total dose, Visual Analog Pain Score (VAPS) q 30 min, sedation score q 1 hr and side effects. Neonates were assessed by 1,5, and 10-min Apgar scores, umbilical venous and arterial blood gases and neurobehavioural scores at four and 24 hr.

RESULTS

Mean VAPS from 7 - 10 cm cervical dilatation were higher in Group A than in Group F (85.7+/-13.9 vs. 64.6+/-12.1; P<0.01) There were no inter-group differences in VAPS from 1-3 cm, or from 4-6 cm dilatation, in maternal sedation scores or side effects, or in neonatal outcomes.

CONCLUSION

In the doses prescribed in this study, PCA fentanyl was found to provide more effective analgesia in late first stage labour than PCA alfentanil.

Alfentanil for intubation under halothane anaesthesia in children

Intubating conditions under halothane anaesthesia aided with alfentanil 20 micrograms.kg-1 were compared with suxamethonium 2 mg.kg-1 in 40 children presenting for day dental procedures. The condition of vocal cords, jaw relaxation and presence of movement and coughing were scored to give the overall intubating conditions. Successful intubation was achieved in 100% of the suxamethonium group and 94.7% of the alfentanil group. The cardiovascular response to intubation was attenuated in the alfentanil group. Some 43.7% of those receiving suxamethonium developed myalgia the day after surgery compared with 0% in the alfentanil group (P < 0.01).

Alfentanil causes less postoperative nausea and vomiting than equipotent doses of fentanyl or sufentanil in outpatients

BACKGROUND

The relative potencies of alfentanil, fentanyl, and sufentanil as a risk factor for postoperative nausea and vomiting have not been determined. They were compared in a randomized study designed to obtain equipotent plasma concentrations of these three opioids at the beginning of the recovery period.

METHODS

The study included 274 patients treated on an outpatient basis. The steady state opioid plasma concentration providing a predicted 50% reduction of the minimum alveolar concentration of isoflurane was used to determine the relative potency of the opioids. The opioids were prepared in equal volumes at concentrations of alfentanil 150 microg/ml, fentanyl 50 microg/ml, and sufentanil 5 microg/ml and were administered in vol/kg. Anesthesia was induced in a blinded fashion with a bolus of the study opioid (0.05 ml/kg) and 4-6 mg/kg thiopental and was maintained with isoflurane (0.6-1%) in a nitrous oxide-oxygen mixture with a continuous infusion of the study opioid (0.06 ml x kg(-1) x h(-1)). If necessary, up to five additional boluses of opioid (0.02 ml/kg) could be given. This opioid administration protocol was tested by pharmacokinetic simulations.

RESULTS

The incidence of postoperative nausea and vomiting was not different in the postanesthesia care unit, but in the ambulatory surgery unit it was significantly lower for alfentanil compared with fentanyl and sufentanil (12, 34, and 35%, respectively P < 0.005). Pharmacokinetic modeling showed that the end-anesthesia opioid plasma concentrations were approximately equipotent in the three groups. However, modeling does not support that the difference between groups in the postoperative period can be explained by a more rapid disappearance of alfentanil from the plasma.

CONCLUSIONS

Alfentanil, compared with approximately equipotent doses of fentanyl and sufentanil, is associated with a lower incidence of postoperative nausea and vomiting in outpatients.