Intrathecal fentanyl is superior to intravenous ondansetron for the prevention of perioperative nausea during cesarean delivery with spinal anesthesia

This study compares intrathecal (IT) fentanyl with IV ondansetron for preventing intraoperative nausea and vomiting during cesarean deliveries performed with spinal anesthesia. Thirty healthy parturients presenting for elective cesarean delivery with standardized bupivacaine spinal anesthesia were randomized to receive 20 microg IT fentanyl (Group F) or 4 mg IV ondansetron (Group O) by using double-blinded methodology. At eight specific intervals during the surgery, a blinded observer questioned the patient about nausea (1 = nausea, 0 = no nausea), observed for the presence of retching or vomiting (1 = vomiting or retching, 0 = no vomiting or retching), and recorded a verbal pain score (0-10, 0 = no pain, 10 = worst pain imaginable). Cumulative nausea, vomiting, and pain scores were calculated as the sum of the eight measurements. Intraoperative nausea was decreased in the IT fentanyl group compared with the IV ondansetron group: the median (interquartile range) difference in nausea scores was 1 (1, 2), P = 0.03. The incidence of vomiting and treatment for vomiting was not different (P = 0.7). The IT fentanyl group had a lower cumulative perioperative pain score than the IV ondansetron group; the median difference in the cumulative pain score was 12 (8, 16) (P = 0.0007). The IT fentanyl group required less supplementary intraoperative analgesia. The median difference in the cumulative fentanyl dose was 100 (75, 100) microg fentanyl, (P = 0.0002).

Bupivacaine-sparing effect of fentanyl in spinal anesthesia for cesarean delivery

BACKGROUND AND OBJECTIVES

Visceral pain decreases in cesarean patients under spinal anesthesia when the dose of local anesthetic is increased. However, larger doses of local anesthetic are associated with higher sensory blocks. We hypothesized that the addition of fentanyl could reduce the dose of bupivacaine necessary to achieve adequate surgical anesthesia.

METHODS

Two double-blinded, sequential, prospective studies were performed on 120 patients. In the preliminary study, the patients received 8, 10, or 12 mg of 0.5% hyperbaric bupivacaine intrathecally. In the second, main study, they received each bupivacaine dose with 10 microg of fentanyl. Each group consisted of 20 patients, and the groups were identified as B8, B10, B12, BF8, BF10, and BF12. Sensory and motor block, intraoperative pain defined by visual analogue scale (VAS), muscle relaxation, and side effects were assessed. We also measured the sensory and motor recovery and the onset of pain in the postanesthesia care unit (PACU).

RESULTS

Maximal block level and incidence of high block (> or = T1) were higher in the 12-mg groups. There was intraoperative pain in 35% of the B8 patients and 20% of the B10 patients, but none in the B12 patients and all fentanyl groups. Incidences of other side effects were not different. The addition of fentanyl to bupivacaine significantly delayed the onset of postoperative pain and sensory recovery, but motor recovery time did not change with additional fentanyl.

CONCLUSIONS

The optimal dose of hyperbaric bupivacaine to produce surgical anesthesia was 12 mg, which was accompanied by high sensory block. With the addition of 10 microg of fentanyl, the dose of bupivacaine could be reduced to 8 mg in spinal anesthesia for cesarean delivery.

Transdermal fentanyl during high-dose chemotherapy and autologous stem cell support

We report on our experience in the use of transdermal fentanyl in management of acute pain due to mucositis WHO-grade IV during high-dose chemotherapy (HDC) and autologous stem cell support (APBSCT). Between 8/96 and 12/98 74 patients received HDC and PBSCT for progressive disease or relapse of non-Hodgkin's lymphoma (n=32), multiple myeloma (n=37), Hodgkin's lymphoma (n=5). All patients suffered from mucositis WHO-grade IV with a need for continuous pain management. Instead of pethidine i.v. fentanyl TTS was used. Sufficient analgesia was achieved mostly with a dose of 50 microg/h. There was no need of supplementary analgesia. Relevant fentanyl-associated side effects were not seen. Patient compliance and acceptance were excellent. The results suggest that transdermal fentanyl is reliable in pain management of chemotherapy-associated mucositis grade IV.

Does the addition of fentanyl to bupivacaine in caudal epidural block have an effect on the plasma level of catecholamines in children?

We evaluated the effect of adding fentanyl to bupivacaine, compared with bupivacaine alone, on the stress response. The effect was evaluated by determining blood levels of epinephrine (E) and norepinephrine (NE) in pediatric patients receiving caudal epidural blocks. Sixty children, 1-8 yr of age, scheduled for elective herniorrhaphy, were randomly allocated to two groups of 30 patients each. Group A received inhaled anesthesia and caudal epidural block with bupivacaine 0.25% alone, 1.0 mL/kg. Group B received identical anesthesia; however, fentanyl 1 microg/kg was added to the bupivacaine in the caudal block. Blood samples for E and NE plasma levels were drawn at induction time (H(0)), at the end of surgery (H(1)), and in the postanesthesia care unit (H(2)). In both groups, there was a significant decrease in the E and NE plasma levels, when comparing H(1) and H(2) with H(0) within the same group (P < 0.001). There were no significant differences in the E and NE plasma levels between the two groups at H(0), H(1), and H(2) (P = 0.5, P = 0.12, P = 0.5, respectively). Pain scores (modified Children's Hospital of Eastern Ontario Pain Score) were also similar in both groups (P = 0. 19). This study suggests that adding fentanyl 1 microg/kg to bupivacaine in the caudal epidural block in children does not influence plasma levels of E and NE, nor does it improve the analgesic intensity of the caudal block.

Comparison of the length of stage II labor and incidence of forceps and cesarean delivery after epidural infusion of 0.125% bupivacaine with 2 mu/mL fentanyl as compared with 0.0625% bupivacaine with 2 mu/mL fentanyl

A large, retrospective chart review was conducted to analyze the length of stage II labor and instrumental and cesarean-section delivery rates in nulliparous women who received either 0.0625% bupivacaine with 2 mu/mL fentanyl or 0.125% bupivacaine with 2 mu/mL fentanyl. Data collected included length of stage II labor, incidence of operative or instrumental delivery rates, concentration of bupivacaine used, and demographic data. Demographics obtained included maternal age, weight, and height, as well as neonatal gestational age, weight, and Apgar scores. Further investigated were additional analgesic requirements of supplemental boluses of local anesthetic between the groups. No differences in demographics were noted between the groups. Instrumental delivery rates were similar between the groups with an incidence of 17.5% in the 0.125% bupivacaine group versus a 15% incidence in the 0.0625% bupivacaine group. Cesarean delivery rate was 17% in the 0.125% bupivacaine group versus a 21% ratio in the 0.0625% bupivacaine group. Duration of stage II labor was noted to be prolonged in the 0.125% bupivacaine group but was not statistically significant. Based on this data, it can be concluded that the use of 0.125% bupivacaine with 2 mu/mL fentanyl does not cause a statistically significant increase in instrumental or cesarean delivery rates, nor does it have a detrimental effect on length of stage II labor.

Effect of anaesthesia on the cardiac response to intravenous adenosine

The cardiac response to intravenous adenosine 112 micrograms kg-1 was studied in 16 patients scheduled for coronary artery bypass surgery before and during anaesthesia with 1% end-tidal isoflurane and fentanyl 10 micrograms kg-1. Mean time from injection to onset of adenosine-induced PR prolongation was significantly greater during anaesthesia (12.8 (SD 5) vs 9.9 (3) s, P = 0.032). Atrioventricular block (assessed by the total number of non-conducted P waves) was significantly less during anaesthesia (12 vs 27, P = 0.016). We conclude that anaesthesia including 1% isoflurane and fentanyl 10 micrograms kg-1 delays the onset and reduces the magnitude of adenosine-induced atrioventricular block.

Improved bowel function after gynecological surgery with epidural bupivacaine-fentanyl than bupivacaine-morphine infusion

PURPOSE

To compare postoperative gastrointestinal recovery between continuous epidural bupivacaine-fentanyl and bupivacaine-morphine.

METHODS

In a blinded, randomized, prospective trial, 60 women undergoing surgery for gynecologic cancer were studied. Anesthesia was provided by a combined general/epidural (L2-3 catheter) technique without epidural opioids. Postoperative epidural analgesia was by continuous infusion of bupivacaine 0.1% with either morphine 0.05 mg x ml(-1) (BM) or fentanyl 5 microg x ml(-1) (BF). Visual Analogue Scale (VAS) scores for pain at rest and during movement, and the return of bowel function were collected for three days and the duration of hospitalization were noted.

RESULTS

On POD-1, 18.5% of patients in the BM group had emesis compared with none in the BF group (P = 0.038) and fewer patients in the BM group tolerated clear oral fluids (11.1% BM vs 40.6% BF, P = 0.025). These differences became insignificant on POD-2 and 3. Median pain scores were comparable at rest and ranged from 10-20 in the BM group vs 0-20 in the BF group over the three days. Similarly, median pain scores with movement respectively ranged from 20-25 and 20-30 in the BF and BM groups. The mean duration of hospitalization was longer in the BM group (5.7 +/- 2.4) vs BF (4.5 +/- 1.2 days), P = 0.017.

CONCLUSION

Epidural BM and BF provided equally effective postoperative analgesia at rest and during movement. Compared with BM, epidural BF is associated with less emesis and an increased ability to tolerate oral fluids on POD-1 and an overall shorter hospital stay.

Low-dose bupivacaine-fentanyl spinal anesthesia for cesarean delivery

BACKGROUND AND OBJECTIVES

The hypotension following spinal anesthesia remains commonplace in cesarean delivery. Intrathecal opioids are synergistic with local anesthetics and intensify sensory block without increasing sympathetic block. The combination makes it possible to achieve spinal anesthesia with otherwise inadequate doses of local anesthetic. We hypothesized that this phenomenon could be used to provide spinal anesthesia for cesarean delivery while incurring less frequent hypotension.

METHODS

Thirty-two women scheduled for cesarean delivery were divided into 2 groups of patients who received a spinal injection of either 10 mg of isobaric (plain) bupivacaine 0.5% or 5 mg of isobaric bupivacaine with 25 microg fentanyl added. Each measurement of a systolic blood pressure less than 95 mm Hg or a decrease in systolic pressure of greater than 25% from baseline was considered as hypotension and treated with a bolus of 5 to 10 mg of intravenous ephedrine.

RESULTS

Spinal block provided surgical anesthesia in all patients. Peak sensory level was higher (T3 v T4. 5) and motor block more intense in the plain bupivacaine group. The plain bupivacaine patients were more likely to require treatment for hypotension (94% v 31%) and had more persistent hypotension (4.8 v 0.6 hypotensive measurements per patient) than patients in the minidose bupivacaine-fentanyl group. Mean ephedrine requirements were 23.8 mg and 2.8 mg, respectively, for the 2 groups. Patients in the plain bupivacaine group also complained of nausea more frequently than patients in the minidose bupivacaine-fentanyl group (69% v 31%).

CONCLUSIONS

Bupivacaine 5 mg + fentanyl 25 microg provided spinal anesthesia for cesarean delivery with less hypotension, vasopressor requirements, and nausea than spinal anesthesia with 10 mg bupivacaine.

[Combined subarachnoid-epidural technique for obstetric analgesia]

Combined spinal-epidural blockade for labor pain has enjoyed increasing popularity in obstetric anesthesia. The usual procedure is to use a single space and a single needle for dural puncture, inserting a spinal needle through an epidural needle followed by insertion of a catheter. A small dose of one or several substances (usually a lipophilic opioid and a local anesthetic) is first injected in the intrathecal space to provide rapid, effective analgesia with minimal muscle blockade. The epidural catheter is used if labor lasts longer than the spinal block, if the spinal block is insufficient, or in case of cesarean section. Combined spinal-epidural blockade is a safe, valid alternative to conventional epidural analgesia and has become the main technique for providing obstetric analgesia in many hospitals. The most widely-recognized advantage of the technique is high maternal satisfaction with rapid and effective analgesia. Mobility of the lower extremities is preserved and the mother is often able to walk. Because opioids are injected into the intrathecal space and because the technique is more invasive than standard epidural analgesia, the potential risk to mother and fetus increases.

[Validation of a method to inactivate fentanyl in the used devices of Durogesic]

A recent literature study has shown that after 3 days of use of a transdermic patch of fentanyl (Durogésic(R)), there was such an amount of drug remaining that may make its excessive use possible. First of all, we have developed a fentanyl assay by a spectrophotometric method and then, the remaining amount of fentanyl was determined in 29 used patches. This study has shown that a mean of 22% of fentanyl remained in the used patches, each original content astounded. Then, we have determined an easy and feasible method in a chemist's shop allowing inactivation of fentanyl in the used patches and so preventing its diversion.

Patient-controlled epidural analgesia with fentanyl-bupivacaine: influence of prior dural puncture

BACKGROUND AND OBJECTIVES

Combined spinal epidural anesthesia (CSEA) involves the epidural administration of local anesthetic and opioid solutions adjacent to the prior dural puncture, potentially increasing their diffusion into the subarachnoid space. This study was designed to evaluate the influence of dural puncture on the adequacy and extent of analgesia, and drugs requirements of patient-controlled epidural analgesia (PCEA) in the postoperative period.

METHODS

In this prospective double-blind study, 40 patients undergoing major abdominal surgery under general anesthesia followed with PCEA were randomly assigned to either group I (preoperative insertion of an epidural catheter) or group II (preoperative dural puncture with a 25-g Quincke needle + insertion of an epidural catheter). Postoperatively, a PCEA pump delivered an infusion of 0.1% bupivacaine + fentanyl (3 microg/mL) at 5 mL/h. Participants were allowed to self-administer 5-mL boluses of the same solution with a 15-minute lock-out interval. Hourly epidural solution requirements were recorded for 40 hours. Sensory and motor block, and pain scores were also analyzed.

RESULTS

There was no difference between groups with regard to epidural solution requirements, pain scores, spread of sensory blockade, or intensity of motor block.

CONCLUSION

Dural puncture with a 25-gauge Quincke needle, performed as part of CSEA, does not influence the drug requirements when a combination of 0.1% bupivacaine and fentanyl (3 microg/mL) is used for PCEA after major abdominal surgery.

The minimum effective concentration of opioids: a revisitation with patient controlled analgesia fentanyl

BACKGROUND AND OBJECTIVES

Whether patients titrate themselves to an individualized blood or plasma opioid concentration (the so-called minimum effective concentration or [MEC]) has been debated extensively. Nevertheless, there is consistent opinion that during patient controlled analgesia (PCA) patients balance acceptable pain relief against unacceptable side effects. This study sought to characterize fentanyl used by PCA with respect to MEC and factors influencing PCA use.

METHODS

An intensive study of 25 patients with observations over the first 24 hours after orthopedic surgery was planned on the premise that this approach would provide a measure of the fentanyl MEC. This necessitated repeated measurements of pain scores and plasma fentanyl concentrations before and 10 minutes after every PCA demand. In addition, a battery of psychological tests was given before and approximately 48 hours after surgery.

RESULTS

Logistic difficulties of maintaining a 24-hour study design resulted in its termination after 5 patients. The patients had convincingly distinct MECs (ranging from 0.23 to 0.99 ng/mL). The relationship between plasma fentanyl concentration and pain score was steep, such that small changes in concentration coincided with marked changes in pain relief. Despite preoperative expectations of achieving satisfaction in postoperative analgesia, not all patients titrated themselves to a pain-free state; all but one were satisfied with PCA. Surprisingly few side effects were reported. Unfortunately, the small sample size made systematic analysis of the psychological tests impossible.

CONCLUSIONS

This study found evidence to support the concepts of an individual MEC and a therapeutic window of fentanyl used with PCA.

Reducing stress responses in the pre-bypass phase of open heart surgery in infants and young children: a comparison of different fentanyl doses

High-dose opioids are advocated for paediatric cardiac surgery to suppress stress responses but they can produce unwanted side effects. There are no data on the dose-dependent effects of opioids on the stress response on which to base rational opioid administration. We conducted a dose ranging study on 40 children less than 4 yr undergoing elective open heart surgery using one of five fentanyl doses: 2, 25, 50, 100 or 150 micrograms kg-1 before surgery. The standardized anaesthetic also included pancuronium and isoflurane. Blood samples were taken at induction, before incision, after sternotomy, immediately before, and at the end of cardiopulmonary bypass. Patients in the 2 micrograms kg-1 group had significant rises in prebypass glucose (P < 0.01), pre- and post-bypass cortisol (P < 0.01), and pre- and post-bypass norepinephrine (P < 0.01). No significant rise occurred in glucose, cortisol and catecholamines in any of the higher dosage groups. Patients in the 2 micrograms kg-1 group had significantly higher mean systolic blood pressure (P < 0.02) and heart rate (P < 0.04). A balanced anaesthetic containing fentanyl 25-50 micrograms kg-1 is sufficient to obtund haemodynamic and stress responses to the pre-bypass phase of surgery. Higher doses of fentanyl (100 and 150 micrograms kg-1) offer little advantage over 50 micrograms kg-1, and can necessitate intervention to prevent hypotension.

Fetal oxygen saturation during epidural and paracervical analgesia

BACKGROUND

We wanted to assess changes in fetal oxygenation during maternal epidural or paracervical analgesia in labor.

METHODS

A prospective, open and non-randomized study. Twenty healthy parturients were enrolled before they asked for pain relief. Informed consent was obtained. Fetal and maternal oxygen saturations were measured before and up to 1 h after the initiation of analgesia. Fetal oximetry was performed with the Nellcor N-400 oximeter+FS-14B fetal oxygen sensor (Nellcor Puritan Bennett, Pleasanton, California, USA). Maternal oximetry was done with Datex Satlite portable monitor (Datex, Finland). Visual analog scale was used for assessing pain relief. Two-way analysis of variance and students t-test were used for statistical analyses.

RESULTS

Fetal oxygenation initially improved in both groups. The saturation then returned to baseline in both groups. In the epidural group, the values remained at baseline or slightly below, while in the paracervical group the saturation remained a little higher than baseline (p=0.009). No change was seen in maternal oxygenation or heart rate. No change in fetal heart rate was found either. Epidural block was superior to paracervical block with respect to pain relief (p=0.002).

CONCLUSIONS

There was a small but significant difference in fetal oxygenation between epidural and paracervical groups during the observation period. The magnitude of the difference is hardly clinically significant. A larger, randomized study is needed to elucidate the mechanisms behind this finding.

Inhaling nitrous oxide reduces the induction dose requirements of propofol

Inhaling nitrous oxide (N(2)O) before propofol induction appears to decrease propofol usage. To investigate the efficacy of N(2)O as a component of the drugs used to induce anesthesia, the effect of inhaling a N(2)O:oxygen (O(2)) mixture on the dose of propofol required to induce anesthesia was determined in a double-blinded manner. We randomized 117 unpremedicated patients scheduled for elective surgery into three groups. Group FN received 1 microg/kg fentanyl and breathed 4 L/min N(2)O + 2 L/min O(2). Group PN received placebo and breathed 4 L/min N(2)O + 2 L/min O(2). Group FO received 1 microg/kg fentanyl and breathed 6 L/min O(2). Propofol was infused at 20 mg/min after 1 min of gas mixture inhalation, and the infusion stopped when there was loss of response to verbal command. The mean (SD) propofol dose was 0.75 (0.30), 0.84 (0.26), and 1.33 (0.51) mg/kg, and the induction time 133 (57), 142 (47), and 226 (78) s for Groups FN, PN, and FO, respectively. We conclude that inhalation of 66% N(2)O in O(2) 1 min before the IV induction of anesthesia with propofol at 20 mg/min, reduces the induction dose of propofol by 44% and decreases the time required for the induction of anesthesia (P < 0.001).

An alternative algorithm for dosing transdermal fentanyl for cancer-related pain

Many cancer patients are undermedicated and inappropriately managed for pain, leading to a diminished quality of life. Patients with moderate to severe pain often require opioid analgesics. Recently published guidelines emphasize individualization of opioid treatment to provide the drug and route of administration that meet the needs of the particular patient. Intolerable side effects, ineffective pain relief, or a change in the patient's clinical status can dictate the need for a new pain management regimen. Physicians must be able to readily quantify relative analgesic potency when converting from one opioid to another or from one route of administration to another. Transdermal fentanyl (Duragesic) is an opioid agonist that has been shown to be safe and effective for the treatment of cancer pain. However, clinicians should realize that the manufacturer's recommendations for equianalgesic dosing of transdermal fentanyl may result in initial doses that are too low in some patients, and in a titration period that is too long. Under these circumstances, the patient is likely to experience unrelieved pain. An alternative dosing algorithm that considers both a review of the literature and our combined clinical experience with transdermal fentanyl should help clinicians individualize the treatment of pain.

An assessment of desflurane for use during cardiac electrophysiological study and radiofrequency ablation of supraventricular dysrhythmias in children

Desflurane has several properties making it a desirable agent for use in electrophysiological studies (EPS) for diagnosis and treatment of cardiac dysrhythmias. We studied 47 children, mean age 12.8+/-4.6 years, mean weight 52.9+/-24.0 kg, with clinical history of supra- ventricular tachycardia (SVT) during EPS using desflurane in a crossover comparison with fentanyl. The patients served as their own controls. All received oral premedication with lorazepam, and intravenous induction with thiopentone, rocuronium, and oxygen. Group 1 (n=24) were administered fentanyl 10 microg.kg-1 bolus i.v. with an infusion of 3 microg.kg-1.h-1 during initial EPS. Fentanyl was discontinued and desflurane, 6% endtidal, was administered and the EPS repeated. Group 2 (n=23) were initially administered 6% desflurane after induction, and following EPS the desflurane was discontinued and the patients administered fentanyl 3 microg.kg-1 bolus and EPS repeated (explanations of EPS abbreviations are provided). Desflurane reduced the mean arterial pressure (MAP) in all patients. In Group 1, desflurane shortened the sinus cycle length (SCL), i.e. increasing the heart rate, and atrial effective refractory period (AERP) while Group 2 demonstrated no such effect on AERP. There were no other significant differences between fentanyl or desflurane techniques in terms of EPS measurements. SVT was inducible with both agents in both groups. Desflurane seems an acceptable agent for use during EPS procedures.

[The combined use of fentanyl and clofelin in the anesthesiological support of adrenalectomy]

The analgetic effect of a combination of phentanyl and clonidine was investigated in 68 cases of adrenalectomy as an analgetic component of anesthesia. The analgesic potency of the used combination and stability of the autonomous functions were proved to be sufficient in surgical interventions for various types of adrenal tumors. It was found that the mechanism of the clonidine effect was not associated with vasodilatation and was based on its antinociceptive properties. The role of hemodynamic monitoring in prevention of possible complications and adverse effects of the described anesthetic technique was stressed.

Continuous spinal anaesthesia/analgesia for the perioperative management of high-risk patients

The intraoperative effects of continuous spinal anaesthesia, and the efficacy of postoperative continuous spinal analgesia in 48 elderly high risk patients undergoing major abdominal, vascular or orthopaedic surgery is reported. Intraoperative anaesthetic technique proved to be safe and provided satisfactory results in the immediate postoperative period. Furthermore, the postoperative analgesic regimen which involved intrathecal fentanyl and bupivacaine, and intravenous tenoxicam, provided effective analgesia for all patients. The intrathecal analgesic regimen was administered continuously through a PCA pump which had the facility to provide bolus doses when requested in predetermined lockout intervals. The mean doses of fentanyl and bupivacaine infused intrathecally for the first 24 h postoperatively were 14.5 +/- 1.5 microg h(-1) (mean +/- SD) and 0.72 +/- 0.08 mg h(-1) (mean +/- SD), respectively, while the requirements for analgesia decreased progressively overtime but lasted for 118 h. The technique provided effective analgesia with low pain scores that was reflected by the ease in performing physical exercises and the pleasant co-operation with the physiotherapist. Only minor complications related to anaesthesia/analgesia were encountered.

A comparison of intrathecal analgesia with fentanyl or sufentanil after total hip replacement

We designed this study to compare the postoperative analgesic effects of intrathecal fentanyl and sufentanil, the end points being onset, quality, and duration of action. A total of 42 geriatric patients, scheduled for elective total hip replacement under continuous spinal anesthesia, were randomized in two double-blinded groups as soon as they experienced a pain score higher than 3 of 10 on the visual analog scale in the recovery room. Either 7.5 microg sufentanil or 40 microg fentanyl in 2 mL normal saline were intrathecally administered. Pain scores, rescue analgesia (ketorolac and morphine), and adverse effects (respiratory depression, postoperative nausea and vomiting, and itching) were recorded for 24 h after surgery. In both groups, comparing sufentanil to fentanyl, the time to a pain score <3 (9 +/- 9 vs 11 +/- 8 min), the time to the lowest pain score (18 +/- 6 vs 20 +/- 15 min), and the time to the first systemic analgesic intervention for a pain score >3 (241 +/- 102 vs 214 +/- 120 min) were comparable as were the analgesic requirements during the first 24 h. We conclude that, after total hip replacement, both lipid soluble opioids produce excellent analgesia with comparable onset, duration of action, and low incidence of minor adverse effects.

IMPLICATIONS

We compared the postoperative analgesic properties of 40 microg intrathecal fentanyl and 7.5 microg sufentanil after total hip replacement. Both opioids provided satisfactory analgesia, with comparable onset (11 +/- 8 vs 9 +/- 9 min) and duration of action (214 +/- 120 vs 241 +/- 102 min), as well as low incidence of minor side effects.

Maximum tolerated dose of nalmefene in patients receiving epidural fentanyl and dilute bupivacaine for postoperative analgesia

BACKGROUND

This study investigated the ability of the modified continual reassessment method (MCRM) to determine the maximum tolerated dose of the opioid antagonist nalmefene, which does not reverse analgesia in an acceptable number of postoperative patients receiving epidural fentanyl in 0.075% bupivacaine.

METHODS

In the postanesthetic care unit, patients received a single intravenous dose of 0.25, 0.50, 0.75, or 1.00 microg/kg nalmefene. Reversal of analgesia was defined as an increase in pain score of two or more integers above baseline on a visual analog scale from 0 through 10 after nalmefene administration. Patients were treated in cohorts of one, starting with the lowest dose. The maximum tolerated dose of nalmefene was defined as that dose, among the four studied, with a final mean probability of reversal of anesthesia (PROA) closest to 0.20 (ie., a 20% chance of causing reversal). The modified continual reassessment method is an iterative Bayesian statistical procedure that, in this study, selected the dose for each successive cohort as that having a mean PROA closest to the preselected target PROA of 0.20.

RESULTS

The modified continual reassessment method repeatedly updated the PROA of each dose level as successive patients were observed for presence or absence of ROA. After 25 patients, the maximum tolerated dose of nalmefene was selected as 0.50 microg/kg (final mean PROA = 0.18). The 1.00-microg/kg dose was never tried because its projected PROA was far above 0.20.

CONCLUSIONS

The modified continual reassessment method facilitated determination of the maximum tolerated dose ofnalmefene . Operating characteristics of the modified continual reassessment method suggest it may be an effective statistical tool for dose-finding in trials of selected analgesic or anesthetic agents.

The use of bispectral analysis in patients undergoing intravenous sedation for third molar extractions

PURPOSE

The bispectral (BIS) index has been used to interpret electroencephalogram (EEG) recordings to predict the level of sedation and loss of consciousness in patients undergoing general anesthesia. It was the purpose of this project to assess the usefulness of BIS technology in determining the level of sedation in patients undergoing third molar extraction under conscious sedation.

PATIENTS AND METHODS

Twenty-five subjects undergoing third molar extraction in an outpatient setting were analyzed. The EEG activity was recorded continually during surgery using a microcomputer (Aspect-1050 Monitor; Aspect Co, Natick, MA) with real-time bispectral data obtained by EEG skin electrodes through a frontotemporal montage. The Observer's Assessment of Alertness and Sedation (OAA/S) scale was used to subjectively assess the level of sedation observed by the anesthetist before initiating the sedation procedure and then at 5-minute intervals until the end of the procedure. The BIS level was simultaneously recorded. The initial sedation was accomplished using a standard dose of midazolam (0.05 mg/kg) and fentanyl (1.5 microg/kg) followed by a 10- to 30-mg bolus of propofol until a level of sedation at which the patient's eyes were closed and he or she was responsive only to vigorous stimulation or repeated loud calling of their name (OAA/S level of 1 to 2). Local anesthesia was then administered. Additional doses of sedative medication (midazolam or propofol) were given during the procedure to maintain the desired level of sedation (an OAA/S level of 2 to 3). The time and dose of the drug given were recorded. The level of sedation based on a single anesthetist's interpretation (OAA/S) and the BIS readings were then compared.

RESULTS

A strong positive relationship between the BIS index and OAA/S readings was found (P < .0001). Pairwise comparisons of mean BIS index and its corresponding OAA/S level were significantly different from each other (P < .003) except for OAA/S levels 2 and 3 (P = .367).

CONCLUSION

BIS technology offers an objective, ordinal means of assessing the depth of sedation. There was a strong relationship between the objective BIS values and subjective assessment (OAA/S scale) of the depth of anesthesia. This can be invaluable in providing an objective assessment of sedation in oral and maxillofacial surgery where it may be difficult to determine the level of sedation clinically.