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PubMed1994

Postoperative epidural fentanyl infusion--is the addition of 0.1% bupivacaine of benefit?

A randomised, double-blind controlled clinical trial was conducted in 90 women scheduled for major abdominal gynaecological oncology surgery to determine the effect of adding 0.1% plain bupivacaine to a thoracic epidural fentanyl infusion. Following combined epidural and general anaesthesia, patients were randomised to receive epidural fentanyl 10 micrograms/ml, with (group FB) or without (group F) bupivacaine. After an initial 50 micrograms bolus of fentanyl, infusion rate was adjusted according to need between 2 and 10 ml/hr for 48 hours. The two groups (n = 40) were similar with regard to age, weight and preoperative status. Analgesia both at rest and with movement were significantly better in group FB (P < 0.0001) during the first 24 hours postoperatively, the greatest difference occurring in the 4 to 16 hour period. There was no significant difference between groups from 24 to 48 hours postoperatively. Fentanyl utilisation was significantly lower in group FB (median 41 versus 53 micrograms/hr, P < 0.001), although clinically the fentanyl dose-sparing effect of bupivacaine was small and did not reduce opioid-induced side-effects. There was no significant difference between groups with respect to side-effects or lower limb weakness, although fewer patients in group FB could be mobilised on the morning of the first postoperative day (P < 0.01). Nevertheless, all study patients were ambulant by the same afternoon. We concluded that, in this patient population, the addition of 0.1% bupivacaine to a thoracic epidural fentanyl infusion was beneficial in the early postoperative period.

Abdominal Neoplasms↗
PubMedDate not supplied

The use of transdermal fentanyl in pediatric oncology palliative care.

Transdermal fentanyl offers a noninvasive approach to the management of patients with opioid dependent and stable, chronic cancer pain. The transdermal delivery system offers distinct advantages where oral administration of opioids is difficult as a consequence of progressive disease and in patients whose compliance with oral medications is poor. Thirteen patients ranging in age from three years and nine months to 18 years and seven months were treated with transdermal fentanyl for between six hours and 112 days. All had previously been receiving oral morphine prior to the commencement of fentanyl and were transferred to fentanyl because of oral opioid side effects and poor oral compliance. Fentanyl was well tolerated and provided effective pain relief for 11 of 13 patients. Overall, patients and parents experienced satisfaction with fentanyl, both in terms of pain relief and improvement in quality of life.

Administration, Cutaneous↗
PubMedDate not supplied

Intrathecal ropivacaine versus ropivacaine plus fentanyl for out-patient arthroscopic knee surgery.

We evaluated the effects of low-dose intrathecal ropivacaine with or without fentanyl for arthroscopic knee surgery. Fifty patients were randomized in equal groups to receive an intrathecal solution (3 ml) containing either 10 mg isobaric ropivacaine or 8 mg isobaric ropivacaine plus 25 pg fentanyl. Complete motor blockade occurred in 22 patients (88%) in both groups. The time taken to reach sensory blockade to T10 and total motor blockade was shorter in the ropivacaine-treated group, but differences were not statistically significant. The duration of sensory and motor blockade was shorter in the ropivacaine plus fentanyl-treated group. The cephalad spread of sensory blockade was higher with ropivacaine than with ropivacaine plus fentanyl. We conclude that although 25 microg fentanyl added to 8 mg ropivacaine provided shorter motor and sensory blockade durations than 10 mg ropivacaine alone, small doses of ropivacaine plus fentanyl can be used safely for arthroscopic knee surgery.

Adult↗
PubMed2005

Rapid switching between transdermal fentanyl and methadone in cancer patients.

PURPOSE: The aim of this study was to examine the clinical effects of switching from transdermal (TTS) fentanyl to methadone, or vice versa, in patients with a poor response to the previous opioid. PATIENTS AND METHODS: A prospective study was carried out on 31 patients who switched from TTS fentanyl to oral methadone, or vice versa, because of poor opioid response. A fixed conversion ratio of fentanyl to methadone of 1:20 was started and assisted by rescue doses of opioids, and then doses were changed according to clinical response. Pain and symptom intensity, expressed as distress score, were recorded before switching doses of the two opioids and after subsequent doses. The number of changes of the daily doses, time to achieve stabilization, and hospital stay were also recorded. RESULTS: Eighteen patients were switched from TTS fentanyl to methadone, and seven patients were switched from methadone to TTS fentanyl. A significant decrease in pain and symptom intensity, expressed as symptom distress score, was found within 24 hours after switching took place in both directions. Unsuccessful switching occurred in six patients, who were subsequently treated with an alternative therapy. CONCLUSION: A rapid switching using an initial fixed ratio of fentanyl to methadone of 1:20 is an effective method to improve the balance between analgesia and adverse effects in cancer patients with poor response to the previous opioid. No relationship between the final opioid dose and the dose of the previous opioid has been found.

Administration, Cutaneous↗
PubMed1989

Fentanyl stimulates prolactin release through mu-opiate receptors, but not the serotonergic system.

Both serotonin (5-HT) and opiates exert a stimulatory effect on PRL secretion. Some evidence suggests that the action of opiates may be elicited through serotonergic neurons. We tested this hypothesis in the present study by evaluating the effect of perturbation of the serotonergic system on PRL secretion induced by fentanyl, a potent morphine-like analgesic. Female Sprague-Dawley rats ovariectomized for 3 weeks and given polyestradiol phosphate (0.1 mg/rat) for 1 week were used in the study. Fentanyl, at a dose of 20 micrograms/rat, induced significant PRL secretion that peaked at 10 min and lasted for more than 30 min. Pretreatment with naloxone (0.5 mg/kg BW, ip) did not block the acute phase of PRL secretion, but significantly lowered the PRL level at 30 min. Fentanyl at a smaller dose (5 micrograms/rat, iv) still induced significant PRL release 10, but not 30, min after injection. This effect was significantly blocked by pretreatment with the same dose of naloxone. On the other hand, whereas animals pretreated with ketanserin or LY53857 (both at a dose of 5 mg/kg BW, ip), two specific 5-HT2 receptor antagonists, had no effect on fentanyl-induced PRL secretion, the same treatment significantly blocked 5-HT-induced PRL secretion. Likewise, pretreatment with p-chlorophenylalanine (250 mg/kg BW, ip), a 5-HT synthesis inhibitor, for 2 days had no effect on the action of fentanyl, while 5-HT-induced PRL secretion was significantly augmented. We conclude that fentanyl acts through mu-opiate receptors to stimulate PRL secretion in a process that does not involve the serotonergic system.

Animals↗
PubMed1991

Cardiovascular, respiratory, and analgesic effects of fentanyl in unanesthetized rhesus monkeys.

To determine the suitability of the rhesus monkey as a model for investigation of opioids, we examined the analgesic, respiratory, and cardiovascular effects of fentanyl in six adult male rhesus monkeys. Fentanyl was administered in sequential bolus injections of 2, 4, 16, 64, and 128 micrograms/kg, with 10 min between each dose. Arterial plasma fentanyl concentrations and blood gas tensions were measured 3 and 9 min after each dose and 1, 2, 5, 20, 60, and 120 min after the final dose. At the same time periods, mean systemic arterial, pulmonary arterial, central venous, and pulmonary capillary wedge pressures, cardiac output, heart rate, and respiratory rate were measured. Analgesia was quantified as the time required for tail withdrawal from a standardized noxious stimulus. Tail latency response time increased significantly after the 4-microgram/kg dose (plasma fentanyl concentration = 2.7 +/- 0.9 ng/mL). Maximum tail latency response time was attained after the 64-micrograms/kg dose (43.4 +/- 26.0 ng/mL). Respiratory rate decreased significantly after the 2-microgram/kg dose, and PaCO2 increased significantly after the 4-microgram/kg dose. All animals became apneic, requiring tracheal intubation and controlled ventilation, after the 64-micrograms/kg dose. Also, mean arterial pressure and cardiac output decreased significantly after the 64-micrograms/kg dose. There were no other significant cardiovascular changes. Peak plasma fentanyl concentration after the 128-micrograms/kg dose was 117.0 +/- 49.6 ng/mL. It appears that plasma concentrations of approximately 40 ng/mL are sufficient to reach the full cardiovascular, respiratory, and analgesic effects of fentanyl in the rhesus monkey. Significant respiratory and analgesic effects are evident at concentrations as low as 3 ng/mL.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesia↗
PubMed1991

Effect of fentanyl and nitrous oxide on the desflurane anesthetic requirement.

The minimum alveolar anesthetic concentration (MAC) of desflurane (I-653) was determined when administered with 60% nitrous oxide (N2O) in oxygen after a standardized induction sequence consisting of 0, 3, 6, or 9 micrograms/kg intravenous (IV) fentanyl followed by 3-6 mg/kg IV thiopental and 1.5 mg/kg IV succinylcholine. For comparison, we also determined the isoflurane MAC with 60% N2O in oxygen after an induction dose of 3 micrograms/kg IV fentanyl and similar doses of thiopental and succinylcholine. All patients were undergoing elective surgical procedures. The minimum alveolar anesthetic concentration in patients given isoflurane and 60% N2O with 3 micrograms/kg fentanyl was 0.4%, approximately 20% below previously reported MAC values for isoflurane with 60% N2O alone. The minimum alveolar anesthetic concentration of desflurane with 60% N2O plus 0, 3, 6, and 9 micrograms/kg IV fentanyl was 3.7%, 3.0%, 1.2%, and 0.1%, respectively. Thus, the MAC-lowering effect of 3 micrograms/kg IV fentanyl appears to be similar with both isoflurane and desflurane. Fentanyl, 3-9 micrograms/kg IV, produces dose-dependent decreases in the MAC of desflurane.

Adult↗
PubMed1991

Ibuprofen provides longer lasting analgesia than fentanyl after laparoscopic surgery.

The authors compared the analgesic efficacy of one dose of oral ibuprofen with that of intravenously administered fentanyl for relief of pain after outpatient laparoscopic surgery. Thirty healthy female patients received either 800 mg of oral ibuprofen preoperatively or 75 micrograms of intravenous fentanyl intraoperatively plus respective intravenous or oral placebos in a randomized, double-blind manner. Patients recorded their degree of pain and nausea in the recovery room, in the same-day surgery stepdown unit, during the ride home, and upon arrival at home. The postanesthesia care nurse recorded the amount of fentanyl and droperidol needed to treat pain and nausea in the recovery room. Patients who received ibuprofen were more comfortable in the stepdown unit (P less than 0.05) and after arrival home (P less than 0.05) than those in the fentanyl group. Additionally, patients who received ibuprofen had lower nausea scores in the step-down unit (P less than 0.05); this may have been related to the lower total fentanyl dose in these patients. The authors conclude that ibuprofen may be a useful alternative to fentanyl for providing postoperative analgesia for outpatient surgery.

Administration, Oral↗
PubMed1992

Clinical effects of intrathecally administered fentanyl in patients undergoing cesarean section.

The clinical effects of spinally (subarachnoid) administered, preservative-free fentanyl were assessed in 120 healthy women who underwent cesarean section with spinal anesthesia using 0.5% hyperbaric bupivacaine. Subjects were divided at random into four groups (n = 30) the first of which received 2 mL of saline containing no fentanyl (group 0); the second, 0.25 micrograms/kg (group 25); the third, 0.5 micrograms/kg (group 50); and the fourth, 0.75 micrograms/kg (group 75) of fentanyl in a blinded manner. Surgical anesthesia was excellent in 100% of treated patients and in 87% of group 0. Respiratory rate decreased significantly in groups 50 and 75 and was recorded as early as 4 min after the administration of the drug. Nevertheless, respiratory depression did not develop in any patient, and 40 min later all groups had a similar respiratory rate. Regression of anesthesia to the T-12 dermatome took a longer time as the dose of fentanyl increased, but all patients had recovered by 240 min after the injection. Effective postoperative analgesia lasted longer and significantly increased with the dose of fentanyl administered: group 0, 197 +/- 77 min; group 25, 305 +/- 89 min; group 50, 640 +/- 142 min; and group 75, 787 +/- 161 min (data expressed as mean +/- SD; P less than 0.001 between groups). Neonatal status was the same in all groups. Sedation and pruritus were the main side effects. The combination of bupivacaine and a low dose of fentanyl (0.25 micrograms/kg) provides excellent surgical anesthesia with short-lasting postoperative analgesia and very few negative side effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Prolonged analgesia after epidural injection of a poorly soluble salt of fentanyl.

Epidurally administered fentanyl is commonly used in postoperative pain management. The onset of action is rapid, but the duration of analgesia is short. In this study we examined the hypothesis that a poorly soluble salt of fentanyl (fentanyl pamoate) would create a depot of the drug in the epidural space and thus provide prolonged analgesia. The dose-response relationship and duration of analgesic action of epidural fentanyl citrate (FC) and fentanyl pamoate (FP) were studied in white male Sprague-Dawley rats. Somatic and visceral nociceptive stimulation (tail flick and colorectal distension, respectively) were used to test the analgesic effects of the drugs. The calculated dose producing 100% of the maximum possible effect (100% MPE) for FP was 31 micrograms toward somatic and 33 micrograms toward visceral noxious stimulation, and for FC it was 3 micrograms toward both stimulations. The antinociceptive effects were similar, with 31 micrograms of FP and 3 micrograms of FC. The areas under the time-response curves (AUC) were significantly higher with FP than with FC when high doses (5 micrograms of FC or 50 micrograms of FP) were used, but with doses expected to produce 100% MPE, differences between the study drugs were not observed in the duration of analgesia. We conclude that the duration of antinociceptive effect of fentanyl can be prolonged when administered as a poorly soluble salt.

Analgesia, Epidural↗
PubMed2004

Patient-controlled analgesia with fentanyl for burn dressing changes.

In this randomized, double-blinded study in 60 ASA I or II adults with >20% body-surface area thermal burns, we investigated the feasibility of patient-controlled analgesia (PCA) with fentanyl for pain management during dressing changes and determined the optimal PCA-fentanyl demand dose. An initial loading dose of IV fentanyl 1 microg/kg was administered. Patients received on-demand analgesia with fentanyl (10, 20, 30, and 40 microg) whenever their visual analog scale (VAS) score was >2. Mean VAS scores in the 10 and 20 microg groups (7.73 +/- 1.33 and 7.20 +/- 1.21, respectively) were significantly higher than those in the 30 and 40 microg groups (4.47 +/- 0.83 and 3.90 +/- 0.63, respectively) (all P = 0.000). Demand/delivery ratios were significantly larger in the 10 and 20 microg groups (3.03 +/- 1.06 and 2.54 +/- 0.49, respectively) than those in the 30 and 40 microg groups (1.36 +/- 0.34 and 1.37 +/- 0.36, respectively) (all P = 0.000). VAS scores and demand/delivery ratios were comparable in the 30 and 40 microg groups (P = 0.260 and P = 0.977, respectively), which suggests comparable analgesic efficacy. There was no hemodynamic instability or respiratory depression. The optimal demand dose of PCA-fentanyl was 30 microg (5-min lockout interval) after an initial loading dose of IV fentanyl 1 microg/kg.

Adult↗
PubMed1994

Binding of fentanyl and pethidine to muscarinic receptors in rat brain.

Symptoms similar to the central anticholinergic syndrome are often seen after high dose fentanyl anesthesia. Therefore, the binding of fentanyl, alfentanil, pethidine and morphine to opioid and muscarinic receptors was investigated in rat brain homogenate with [3H]naloxone and [3H]QNB as the radioligands, respectively. Both pethidine and fentanyl inhibited [3H]QNB binding with Ki values in the micromolar range. Alfentanil and morphine had no affinity for muscarinic receptors. The ratio of the Ki values for muscarinic receptors versus opioid receptors was 2.5 for pethidine and 88 for fentanyl. It is concluded that binding of fentanyl to muscarinic receptors is likely to occur during high-dose fentanyl anesthesia.

Animals↗
PubMed1998

Higher environmental temperature potentiates cataleptic effect of fentanyl in rats.

The influence of higher environmental temperature (HET=30/-1 degrees C) on fentanyl-induced behavior was studied in unrestrained rats. Subacute exposure (3 days) of rats to HET significantly (P<0.01) increased the cataleptic effect of fentanyl citrate (0.5 mg/kg), in comparison to the corresponding exposure to normal environmental temperature (NET=22+/-1 degrees C). Also, the hyperthermic response of rats to a low dose of fentanyl citrate (0.2-0.5 mg/kg) was significantly (P<0.01) potentiated, and the hypothermic response to a high dose of fentanyl citrate (1.5 mg/kg) was significantly (P<0.05) attenuated after exposure to HET. Fentanyl-induced hyperexcitability, loss of righting reflex, loss of corneal reflex and analgesia were not significantly affected by HET. This study provides the first evidence on the influence of environmental temperature on drug-induced catalepsy. HET-induced potentiation of the cataleptic response to fentanyl could be the result of an interference with behavioral thermoregulation.

Analgesics, Opioid↗
PubMed2006

Fentanyl abuse and dependence: further evidence for second hand exposure hypothesis.

We have proposed a novel hypothesis regarding the potential role of occupational or second-hand exposure in physician substance use, abuse, and addiction. While only 5.6% of licensed physicians in Florida are anesthesiologists, nearly 25% of physicians followed for substance abuse/dependence are anesthesiologists. When we sort by drug of choice, anesthesiologists have more opioid abuse and dependence than other physicians and appropriate controls. Abuse of one opioid, fentanyl, appears to be increasing and has been noted among the State of Florida's causes of opioid deaths. Fentanyl and sufentanyl are commonly administered highly potent opioid analgesics, as much as 80-800 times as potent as morphine. We have recent data from the State of Florida impaired physicians database, which has allowed us to categorize all fentanyl abusing and/ or dependent physicians. Just knowing that a physician abuses fentanyl gives you a good clue as to their specialty; 75% are anesthesiologists! While drug abuse researchers, oncologists and others who handle drugs of abuse everyday, have no greater incidence of opioid abuse or dependence, anesthesiologists are at the top of every list. Can this be due to just access and stress? We have proposed an alternative hypothesis of second hand exposure. To test this hypothesis, we developed a sensitive LC/MS/MS assay to measure the intravenous anesthetic and analgesic agents, propofol and fentanyl in air. Not only did we detect propofol and fentanyl in cardiovascular surgery operating room air, we also found the highest concentrations were close to the patient's mouth where anesthesiologists work for hours. Like tobacco, second hand opioid exposure can sensitize and change the brain making abuse, dependence and behavioral disorders more likely. Thus environmental exposure and sensitization may be an important risk factor in physician addiction. Second hand exposure may affect treatment outcome and explain anesthesiologist's inability to return to work in the operating room. We are developing an animal model for second hand exposure and additional studies of the operating room and cardiac anesthesiologists are underway.

Analgesics, Opioid↗
PubMed2005

Participation of ATP-sensitive K+ channels in the peripheral antinociceptive effect of fentanyl in rats.

We examined the effect of several K+ channel blockers such as glibenclamide, tolbutamide, charybdotoxin (ChTX), apamin, tetraethylammonium chloride (TEA), 4-aminopyridine (4-AP), and cesium on the ability of fentanyl, a clinically used selective micro-opioid receptor agonist, to promote peripheral antinociception. Antinociception was measured by the paw pressure test in male Wistar rats weighing 180-250 g (N = 5 animals per group). Carrageenan (250 microg/paw) decreased the threshold of responsiveness to noxious pressure (delta = 188.1 +/- 5.3 g). This mechanical hyperalgesia was reduced by fentanyl (0.5, 1.5 and 3 microg/paw) in a peripherally mediated and dose-dependent fashion (17.3, 45.3 and 62.6%, respectively). The selective blockers of ATP-sensitive K+ channels glibenclamide (40, 80 and 160 microg/paw) and tolbutamide (80, 160 and 240 microg/paw) dose dependently antagonized the antinociception induced by fentanyl (1.5 microg/paw). In contrast, the effect of fentanyl was unaffected by the large conductance Ca2+-activated K+ channel blocker ChTX (2 microg/paw), the small conductance Ca2+-activated K+ channel blocker apamin (10 microg/paw), or the non-specific K+ channel blocker TEA (150 microg/paw), 4-AP (50 microg/paw), and cesium (250 microg/paw). These results extend previously reported data on the peripheral analgesic effect of morphine and fentanyl, suggesting for the first time that the peripheral micro-opioid receptor-mediated antinociceptive effect of fentanyl depends on activation of ATP-sensitive, but not other, K+ channels.

Analgesia↗
PubMed2004

Clinical effects and plasma concentrations of fentanyl after transmucosal administration in three species of great ape.

Fentanyl is approved for transmucosal use in the United States as a preanesthetic agent in human pediatric patients and in adults for breakthrough cancer pain. Using this formulation in three species of great ape, including eight orangutans (Pongo pygmaeus), nine chimpanzees (Pan troglodytes), and two gorillas (Gorilla gorilla), fentanyl was offered transmucosally at an intended dose of 10-15 microg/kg based on estimated body weight. The animals were trained to accept and suck slowly on a piece of placebo candy, given as a treat, after an overnight fast. On the day of the study, the animals were given the lollipop formulation of fentanyl. The resulting plasma concentrations of fentanyl supported transmucosal absorption, similar to that reported in humans. This study provides an alternative sedative regimen and yielded half-life data of transmucosal fentanyl in great apes. Although transmucosal fentanyl was a useful adjunct for sedating orangutans and gorillas, its acceptance by chimpanzees before chemical immobilization was suboptimal and unpredictable.

Adjuvants, Anesthesia↗
PubMed2003

The effect of rectal temperature on perianesthetic serum concentrations of transdermally administered fentanyl in cats anesthetized with isoflurane.

OBJECTIVES: To determine whether moderate hypothermia during 4 hours of anesthesia with isoflurane substantially affects serum concentrations of transdermally administered fentanyl in the perianesthetic period in cats. ANIMALS: 7 healthy mature cats. PROCEDURE: A fentanyl patch (25 microg/h) was applied to the shaved thorax 24 hours before induction of anesthesia. Anesthesia was induced at time 0. Each cat received 2 treatments in a random order. Treatments were isoflurane anesthesia with normothermia and isoflurane anesthesia with hypothermia. Cats were intubated, connected to a nonrebreathing circuit, and maintained at 1.3X minimum alveolar concentration for 4 hours. Cats in the hypothermia treatment groups were actively cooled to 35 degrees C following the induction of anesthesia. Serum fentanyl analysis was performed at -24, -12, 0, 1, 2, 3, 4, 4.5, 5, 6, 7, 8, 9, 10, 12, and 24 hours. RESULTS: Mean +/- SEM serum fentanyl concentration (SFC) for the hypothermia treatment group (0.598 +/- 0.3048 ng/mL) was significantly lower than the baseline concentration (1.834 +/- 0.6393 ng/mL) at 1 hour. This significant reduction persisted for the duration of anesthesia for the hypothermia treatment group. Serum fentanyl concentrations returned to baseline values within 1 hour of the end of anesthesia, regardless of body temperature. CONCLUSIONS AND CLINICAL RELEVANCE: Hypothermia during inhalant anesthesia induced a significant reduction in SFC obtained with transdermal administration. The impact of this reduction in SFC on the contribution of transdermally administered fentanyl to any reduction in the need for inhalant anesthesia remains to be determined.

Administration, Cutaneous↗
PubMed2006

Evaluation of the isoflurane-sparing effects of lidocaine and fentanyl during surgery in dogs.

OBJECTIVE: To evaluate the isoflurane-sparing effects of lidocaine and fentanyl administered by constant rate infusion (CRI) during surgery in dogs. DESIGN: Randomized prospective study. Animals-24 female dogs undergoing unilateral mastectomy because of mammary neoplasia. PROCEDURES: After premedication with acepromazine and morphine and anesthetic induction with ketamine and diazepam, anesthesia in dogs (n = 8/group) was maintained with isoflurane combined with either saline (0.9% NaCl) solution (control), lidocaine (1.5 mg/kg [0.68 mg/lb], IV bolus, followed by 250 microg/kg/min [113 microg/lb/min], CRI), or fentanyl (5 microg/kg [2.27 microg/lb], IV bolus, followed by 0.5 microg/kg/min [0.23 microg/lb/min], CRI). Positive-pressure ventilation was used to maintain eucapnia. An anesthetist unaware of treatment, endtidal isoflurane (ETiso) concentration, and vaporizer concentrations adjusted a nonprecision vaporizer to maintain surgical depth of anesthesia. Cardiopulmonary variables and ETiso values were monitored before and after beginning surgery. RESULTS: Heart rate was lower in the fentanyl group. Mean arterial pressure did not differ among groups after surgery commenced. In the control group, mean +/- SD ETiso values ranged from 1.16 +/- 0.35% to 1.94 +/- 0.96%. Fentanyl significantly reduced isoflurane requirements during surgical stimulation by 54% to 66%, whereas the reduction in ETiso concentration (34% to 44%) observed in the lidocaine group was not significant. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of fentanyl resulted in greater isoflurane sparing effect than did lidocaine. However, it appeared that the low heart rate induced by fentanyl may partially offset the improvement in mean arterial pressure that would be expected with reduced isoflurane requirements.

Adjuvants, Anesthesia↗