Multiple dose pharmacokinetics of oral transmucosal fentanyl citrate in healthy volunteers

BACKGROUND

Oral transmucosal fentanyl citrate (OTFC) is a solid form of fentanyl that delivers the drug through the oral mucosa. The clinical utility of multiple doses of OTFC in the treatment of "breakthrough" cancer pain is under evaluation. The aim of this study was to test the hypothesis that the pharmacokinetics of OTFC do not change with multiple dosing.

METHODS

Twelve healthy adult volunteers received intravenous fentanyl (15 microg/kg) or OTFC (three consecutive doses of 800 microg) on separate study sessions. Arterial blood samples were collected for determination of fentanyl plasma concentration by radioimmunoassay. The descriptive pharmacokinetic parameters (maximum concentration, minimum concentration, and time to maximum concentration) were identified from the raw data and subjected to a nonparametric analysis of variance. Population pharmacokinetic models for all subjects and separate models for each subject were developed to estimate the pharmacokinetic parameters of fentanyl after multiple OTFC doses.

RESULTS

The shapes of the profiles of plasma concentration versus time for each dose of OTFC were grossly similar. No change was noted for maximum concentration or time to maximum concentration over the three doses, while minimum concentration did show a significantly increasing trend. Terminal half-lives for intravenous fentanyl and OTFC were similar. A two-compartment population pharmacokinetic model adequately represented the central tendency of the data from all subjects. Individual subject data were best described by either two- or three-compartment pharmacokinetic models. These models demonstrated rapid and substantial absorption of OTFC that did not change systematically with time and multiple dosing.

CONCLUSIONS

The pharmacokinetics of OTFC were similar among subjects and did not change with multiple dosing. Multiple OTFC dosing regimens within the dosage schedule examined in this study can thus be formulated without concern about nonlinear accumulation.

Delays in the detection of hypoxemia due to site of pulse oximetry probe placement

STUDY OBJECTIVES

To determine if there were any differences in the time to detect hypoxemia related to the site of peripheral pulse oximetry (ear, hand, and foot) during the rapid induction of hypoxemia in healthy volunteers.

DESIGN

Repeated-measures, longitudinal, observational study.

SETTING

Anesthesia clinical research area of the Department of Anesthesiology.

PATIENTS

13 healthy volunteers, aged 18 to 44 years.

INTERVENTIONS

Nellcor N-200 (Nellcor, Inc., Pleasanton, CA) oximeter probes were placed at the ear, hand, and foot. All units were turned on simultaneously with averaging times set for 5 seconds and signals sampled at 2 Hz. A computer-controlled anesthesia circuit was employed to induce mild hypercapnia and hyperoxia (end-tidal gas partial pressures: PETCO2 = 42 +/- 2 mmHg and PETO2 = 130 mmHg) for 5 minutes. PETO2 was then decreased to 45 +/- 2 mmHg over 60 seconds and held at that value for 5 minutes.

MEASUREMENTS AND MAIN RESULTS

The mean differences in time (sec) for pulse oximeters to detect hypoxemia (read less than 90%) between probe sites were determined and compared. The following mean differences in time (sec) for pulse oximeters to detect hypoxemia (read less than 90%) between probe sites were found: ear-hand = 6; hand-foot = 57; ear-foot = 63. Paired t-tests revealed statistically significant mean time delay differences of 51 seconds (p < 0.005) and 57 seconds (p < 0.005) for ear-hand versus hand-foot and for ear-hand versus ear-foot, respectively.

CONCLUSIONS

In healthy volunteers, significant delays in the detection of acute hypoxemia by pulse oximetry occur when pulse oximeters are placed at the toe as compared with probes at either the ear or hand.

Rapid onset of ulnar nerve dysfunction during transient occlusion of the brachial artery

Perioperative ulnar neuropathy is a complication that occurs even in patients who seem to be appropriately padded and positioned. The disproportionately high incidence of postoperative ulnar nerve injury compared with the median and radial nerves has largely been attributed to its vulnerability to compression or stretch at the cubital tunnel. Some clinical and laboratory evidence suggests that compromise of perfusion to the upper extremity may also play a role in this complication. To determine whether the ulnar nerve is more sensitive to ischemia of the upper extremity, we studied 10 men during general anesthesia. Somatosensory evoked potentials of the radial, median, and ulnar nerves were simultaneously recorded during general anesthesia with the brachial artery occluded proximal to the cubital fossa. All three nerves showed rapid changes in signal amplitude in response to occlusion of the brachial artery, but the amplitude of the ulnar nerve was affected earlier and to a greater degree. Compared with the median nerve, the change in ulnar nerve signal amplitude during ischemia was significantly greater after 4 min (P = 0.002). This trend persisted at 6 and 8 min (P = 0.008). At 4, 6, and 8 min of ischemia, the ulnar nerve likewise showed a greater decrease in amplitude compared with the radial nerve, with corresponding P values of 0.015, 0.008, and 0.008. We conclude that the ulnar nerve is more sensitive to ischemia of the upper extremity compared with the radial and median nerves. In addition to its increased vulnerability at the elbow, compromise of arterial flow may contribute to some cases of postoperative ulnar neuropathy.

IMPLICATIONS

Postoperative ulnar neuropathy is thought to result from compression or stretch of the ulnar nerve at the elbow. However, patients may sustain this complication despite careful padding and positioning. This study suggests that the ulnar nerve may also be unusually sensitive to decreases in blood supply to the arm. Care should not only to properly position and pad the elbows, but also to ensure adequate perfusion of the upper extremities.

Dose proportionality and pharmacokinetics of oral transmucosal fentanyl citrate

BACKGROUND

The pharmacokinetics of a single dose (15 microg/kg) of oral transmucosal fentanyl citrate (OTFC) have been characterized. A range of doses may eventually be used in clinical practice. The goal of this study was to determine if the pharmacokinetics of OTFC are dose proportional for doses ranging from 200 to 1,600 microg.

METHODS

Twelve healthy male volunteers were studied on four different occasions, receiving 200, 400, 800, and 1,600 microg OTFC in a double-blind, randomized protocol. Venous blood samples were collected at selected times during and after dosing for a 24-h period and assayed for fentanyl using a radioimmunoassay. Maximum concentration, time to maximum concentration, area under the curve, and elimination half-life were determined for each dose administered. In addition, respiratory rate, need for verbal prompting to breathe, and supplemental oxygen requirements were noted.

RESULTS

Mean fentanyl concentration time curves were similarly shaped with increasing doses. Both peak concentrations and area under the curve increased linearly with an increase in dose, whereas time to reach peak serum concentrations did not vary significantly between doses. Except for the 200-microg dose, the apparent elimination half-life remained relatively constant (358-386 min). The incidence of low respiratory rate, supplemental oxygen requirement, and number of breathing prompts significantly increased with increasing doses.

CONCLUSIONS

Oral transmucosal fentanyl citrate exhibits dose-proportional pharmacokinetics over the dose range of 200-1,600 microg.

The dose-response pharmacology of intrathecal sufentanil in female volunteers

The pharmacologic effects of intrathecal sufentanil (ITS) beyond what is clinically administered (10 microg) are not known. We observed 18 healthy, young, adult female volunteers who received 12.5, 25, or 50 microg of ITS in a randomized, double-blind fashion for 11 h. Analgesia was assessed by pressure algometry at the tibia. Respiratory function was assessed by pulse oximetry, respiratory rate, arterial blood gas, the ventilatory response to CO2, and a respiratory intervention score (RIS). The incidence and severity of side effects also were documented. Serum sufentanil levels were measured for 4 h after ITS administration. We found that ITS produced statistically significant changes in algometry, doubling the pressure required to produce moderate pain. However, doses of ITS greater than 12.5 microg failed to produce proportionate increases in the duration or intensity of analgesia. All doses of ITS produced significant respiratory depression, but only the RIS was significantly related to ITS dose. Neither respiratory rate nor sedation reliably predicted hypoxemia. Supplemental oxygen by nasal cannula consistently prevented pulse oximeter readings below 90%. Serum sufentanil concentrations were related to ITS dose in a statistically significant manner, reached clinically significant concentrations, and followed a time course similar to analgesia and measures of respiratory depression. However, there was no significant increase in measured analgesia associated with the increases in serum sufentanil concentrations. We conclude that in our volunteer model of lower extremity pain, administering ITS in doses larger than 12.5 microg does not improve the speed of onset, magnitude, or duration of analgesia and only causes dose-related increases in serum sufentanil concentrations, which may augment respiratory depression.

Duration of intrathecal labor analgesia: early versus advanced labor

Early first-stage labor pain is primarily visceral in origin. Increasing pain intensity and transition to somatic nociceptive input characterizes late first- and second-stage labor pain. The effect of this change in nociceptive input on the duration of intrathecal labor analgesia has not been well studied. This prospective cohort observational study compares the duration of intrathecal labor analgesia after intrathecal injections made in early labor (3- to 5-cm cervical dilation) and those made in more advanced labor (7- to 10-cm cervical dilation). Forty-one parturients (18 in early labor and 23 in advanced labor) received intrathecal sufentanil (10 micrograms) and bupivacaine (2.5 mg) as part of a combined spinal-epidural technique. Patients rated their pain using a 0-10 verbal pain scale prior to intrathecal injection and every 20 min thereafter. Duration of analgesia was defined as the lesser of time until the pain score exceeded 5 or until a request for supplemental epidural analgesia was made. The duration of spinal analgesia was significantly less when intrathecal injection was made in advanced labor (120 +/- 26 min) compared with early labor (163 +/- 57 min, P < 0.01). We conclude that cervical dilation and stage of labor significantly impact the effective duration of intrathecal sufentanil/ bupivacaine labor analgesia.

Transesophageal echocardiography: an objective tool in defining maximum ventricular response to intravenous fluid therapy

Ventricular preload is an important determinant of cardiac function, which is indirectly measured in the clinical setting by the pulmonary capillary wedge pressure (PCWP). Transesophageal echocardiography (TEE) is rapidly gaining acceptance as a monitor of cardiac function. Although it provides high-resolution images of cardiac structures, clinical assessment of ventricular preload using TEE has been subjective, since quantitative measurements have been difficult to perform in a timely fashion. Automated border detection (ABD) is a new technology used in conjunction with TEE that allows quantitative real-time, two-dimensional measurement of cavity areas. To determine whether enddiastolic area (EDA) measured by ABD can be used to determine an appropriate end point for intravenous fluid administration, nine mongrel dogs were studied. Anesthetized animals were hemorrhaged to achieve a central venous pressure of 0-5 mm Hg. Each animal was then given intravenous fluid (autologous blood followed by hetastarch) until a peak in thermodilution cardiac output (CO) was achieved. Measures of PCWP, EDA, CO, and left ventricular stroke work (LVSW) were obtained after each fluid bolus. Bivariate plots displaying administered volume versus CO, LVSW, and EDA revealed parallel curves for each of these variables with peaks evident at cumulative volumes of 50-55 mL/kg. Multiple regression with mixed model analysis of covariance was performed to determine the significance of EDA in relation to changes in CO and LVSW. Analysis was likewise performed comparing the relationship between PCWP and changes in CO or LVSW. A significant relationship was demonstrated when comparing EDA to changes in CO and LVSW (P = 0.03 and P < 0.0001, respectively). Similar analysis comparing PCWP to changes in CO and LVSW failed to demonstrate a significant relationship (P = 0.54 and P = 0.36, respectively). These data suggest that changes in EDA measured using TEE with ABD are related to trends in cardiac function and can suggest an appropriate end point for intravenous fluid administration as defined by maximum CO and LVSW. PCWP did not demonstrate a significant relationship to changes in CO and LVSW.

The effect of prior dural puncture on cisternal cerebrospinal fluid morphine concentrations in sheep after administration of lumbar epidural morphine

Combined spinal epidural anesthesia has become increasingly popular as a method of providing rapid onset of analgesia or surgical block with access for further administration of analgesics or anesthetics. No in vivo studies have evaluated the relationship between dural puncture and drug transfer from the epidural space to the cerebrospinal fluid (CSF). To determine whether morphine administered in the epidural space adjacent to a dural puncture results in increased CSF concentrations at the cisterna magna (CM), 12 adult ewes were studied. Each animal was assigned to one of three groups. Animals in Group 1 served as a control and received no dural puncture. Animals in Group 2 received a dural puncture with a 25-gauge (G) Whitacre needle, while Group 3 animals received a dural puncture with an 18-G Tuohy needle. One hour after dural puncture, each animal was given epidural morphine, 0.2 mg/kg. Six hours after the administration of epidural morphine, CSF from the CM was sampled and analyzed by gas chromatography-mass spectrometry for morphine concentration. The mean morphine concentration at the CM for Group 1 (control) was 22 +/- 12 ng/mL, whereas animals with 25-G and 18-G dural punctures had concentrations of 154 +/- 32 ng/mL and 405 +/- 53 ng/mL, respectively (P = 0.0005). These data demonstrate that a significant increase in CSF morphine concentration at the brainstem will occur when lumbar epidural morphine is administered adjacent to a dural puncture. Furthermore, the increase in CSF morphine concentration is positively correlated with the size of the needle producing the dural puncture. These findings highlight the potential for delayed respiratory depression when epidural opiate administration follows a dural puncture.

A comparison of topical and retrobulbar anesthesia for cataract surgery

PURPOSE

To evaluate and compare the efficacy of topical and retrobulbar anesthesia for cataract extraction with intraocular lens implantation.

METHODS

One hundred thirty-eight patients prospectively were assigned to the topical (group 1; n = 69) or retrobulbar (group 2; n = 69) anesthesia groups by permuted block restricted randomization. Group 1 received topical 0.75% bupivacaine and intravenous midazolam and fentanyl for anesthesia. Group 2 received intravenous methohexital followed by retrobulbar block with an equal mixture of 2% lidocaine and 0.75% bupivacaine plus hyaluronidase (150 U). A visual pain analogue scale was used to assess the degree of pain during the administration of anesthesia, during surgery, and post-operatively. The degree to which eye movement, touch, and light caused patient discomfort was assessed. Complications and surgical conditions were recorded.

RESULTS

There was no difference in the surgical conditions (P = 0.5) or pain during surgery (P = 0.35) between the two groups. There was more discomfort during administration of topical anesthesia (P < 0.0001) and postoperatively (P < 0.05) in the topical group. Chemosis, subconjunctival hemorrhage, and eyelid hemorrhage were seen almost exclusively in the retrobulbar group. One patient in group 2 had a retrobulbar hemorrhage. Although eyeball movement and squeezing of the eyelids were present more frequently in the topical group, neither was a problem to the surgeon.

CONCLUSION

Topical anesthesia can be used safely for cataract extraction. The degree of patient discomfort is only marginally higher during administration of the anesthesia and postoperatively. However, surgical training and patient preparation are the keys to the safe use of topical anesthesia.

Cardiovascular responses to graded doses of three catecholamines during lactic and hydrochloric acidosis in dogs

We have studied the cardiovascular effects of incremental doses of three catecholamines in dogs subjected to lactic (LAC) and hydrochloric (HCl) acidosis. Fifty-four dogs were allocated randomly to one of three groups: control, LAC and HCl acidosis (n = 18 each group). In the acidotic models, 2 mol litre-1 of lactic acid (4 ml kg-1 h-1) or 2 mol litre-1 of HCl (1 ml kg-1 h-1) was infused i.v. until arterial pH was reduced to 7.00 +/- 0.1. Within each group, six dogs received one of three different drugs in logarithmically incremental doses: adrenaline 0.1, 0.2, 0.4, 0.8, 1.6, 3.2 micrograms kg-1 min-1, noradrenaline 0.1, 0.2, 0.4, 0.8, 1.6, 3.2 micrograms kg-1 min-1 and dobutamine 5, 10, 20, 40, 80, 160 micrograms kg-1 min-1. Cardiovascular variables were monitored, with periodic measurements of plasma electrolyte and lactate concentrations. The pH reduction induced by HCl or lactic acid was associated with a statistically significant increase in mean pulmonary arterial pressure (MPAP), prominent especially in the LAC group where MPAP increased from mean 18 (SD 5) to 27 (6) mm Hg. In the acidotic models, the reduction in myocardial responsiveness to adrenaline or noradrenaline was more prominent than that for the control for corresponding doses of drugs. In the LAC group mean cardiac index decreased significantly from 5.2 (1.8) to 2.2 (0.7) litre min-1 m-2 after infusion of adrenaline 3.2 micrograms kg-1 min-1 and decreased from 5.1 (1.1 to 2.4 (0.9) litre min-1 m-2 after infusion of noradrenaline 3.2 micrograms kg-1 min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Buccal absorption of fentanyl is pH-dependent in dogs

BACKGROUND

Analgesia and sedation have been achieved noninvasively by fentanyl administration through the oral and nasal mucosa. In theory, the transmucosal bioavailability and absorption of fentanyl could be improved by converting more fentanyl to the unionized form by adjusting the surrounding pH. The authors tested this hypothesis in dogs.

METHODS

Under general anesthesia, each of six mongrel dogs was given fentanyl on repeated occasions, first intravenously (once), then by application to the buccal mucosa (six times). Buccal fentanyl administration was accomplished by placement of a pH-buffered solution of fentanyl into a specially constructed cell, which was clamped to the dog's buccal mucosa for 60 min. Fentanyl solutions with pHs of 6.6, 7.2, and 7.7 were studied to span a tenfold difference in the unionized fraction of fentanyl. Femoral arterial blood samples were sampled frequently and analyzed for fentanyl using a radioimmunoassay. Peak plasma concentration and the time of its occurrence for each buccal study were noted from the plasma concentration verses time profile. Terminal elimination half-life, bioavailability, and permeability coefficients were calculated using standard pharmacokinetic techniques.

RESULTS

The variables peak plasma concentration, bioavailability, and permeability coefficient increased three- to fivefold as the pH of the fentanyl buccal solution increased and more fentanyl molecules became unionized. There was no difference in terminal elimination half-life after intravenous fentanyl (244 +/- 68 min) or buccal fentanyl administration (pH 7.7, 205 +/- 89 min; pH 7.2, 205 +/- 65 min; pH 6.6, 196 +/- 48 min). In all buccal studies regardless of pH, time to peak plasma concentration occurred within 10 min of removal of the fentanyl solutions from the buccal mucosa.

CONCLUSIONS

The buccal absorption, bioavailability, and permeability of fentanyl are markedly increased as the pH of the fentanyl solution becomes more basic. Most likely, this is because of an increase in the fraction of unionized fentanyl.

Comparison of methohexital and alfentanil on movement during placement of retrobulbar nerve block

We compared the use of methohexital (0.5 mg/kg) with alfentanil (20 micrograms/kg) as a drug for limiting movement and pain during the placement of a retrobulbar block (RBB). Thirty patients (ASA class I-III) were randomly assigned to receive either methohexital or alfentanil (15 patients in each group). All but two patients (87%) treated with alfentanil were awake and responsive to command. All of the patients given methohexital were unresponsive at the time of block placement. However, less movement was observed when patients were treated with alfentanil compared to methohexital (P < 0.0002). None of the patients treated with alfentanil complained of pain during placement of the RBB. No difference was detected in the incidence of respiratory depression. However, one patient who received alfentanil had a prolonged period of apnea (approximately 30 s) with a significant decrease in oxygen saturation. The incidence of nausea and vomiting and the time to discharge from the outpatient department were similar in the two groups. The results of this study suggest that alfentanil may be used as a single drug to limit movement during placement of retrobulbar block for ophthalmic surgery.

Respiratory-related critical events with intravenous patient-controlled analgesia

OBJECTIVE

The objective of this study was to identify the underlying causes of respiratory-related critical events associated with intravenous patient-controlled analgesia (i.v. PCA).

DESIGN

The design is an observation study of prospectively collected data.

SETTING

An Acute Pain Service (APS) was established for the management of all patients receiving i.v. PCA therapy for pain management. As part of ongoing care, all respiratory-related critical events were documented and analyzed by staff members of the APS team.

PATIENTS

All patients receiving i.v. PCA therapy through the APS during the period of May 1990 through October 1992 were enrolled in the study.

INTERVENTIONS

Evaluation of all respiratory-related critical events was attempted to identify the underlying cause of the event and to determine if measures could be taken to prevent recurrence of similar events.

OUTCOME MEASURES

Any clinical event that could have or did lead to adverse patient outcome was used as an outcome measure.

RESULTS

A total of 3,785 patients received PCA therapy for a total of 11,521 patient care days. Fourteen critical events occurred, of which four led to increased patient care. There were eight programming errors (all involving misprogramming of the continuous infusion): three involved a family member activating the device, three were the result of an error in clinical judgment, and one involved a patient tampering with the device (one event involved more than one error). Of the four events that led to increased patient care, two involved a family member activating the device, one was the result of a programming error, and one was the result of an error in clinical judgment. All patients who experienced a critical event had an uneventful recovery.

CONCLUSIONS

Following review of the critical events, it was determined that the design of the PCA device contributed to the misprogramming errors and the device was removed from service. Changes in the training of physicians and nurses were instituted to avoid recurrence of other errors identified. The incidence of serious respiratory-related critical events was 0.1%. i.v. PCA therapy has the risk of potentially serious complications and requires constant physician and nursing care with an active quality assurance program.

Randomized clinical trial of pressure-controlled inverse ratio ventilation and extracorporeal CO2 removal for adult respiratory distress syndrome

The impact of a new therapy that includes pressure-controlled inverse ratio ventilation followed by extracorporeal CO2 removal on the survival of patients with severe ARDS was evaluated in a randomized controlled clinical trial. Computerized protocols generated around-the-clock instructions for management of arterial oxygenation to assure equivalent intensity of care for patients randomized to the new therapy limb and those randomized to the control, mechanical ventilation limb. We randomized 40 patients with severe ARDS who met the ECMO entry criteria. The main outcome measure was survival at 30 days after randomization. Survival was not significantly different in the 19 mechanical ventilation (42%) and 21 new therapy (extracorporeal) (33%) patients (p = 0.8). All deaths occurred within 30 days of randomization. Overall patient survival was 38% (15 of 40) and was about four times that expected from historical data (p = 0.0002). Extracorporeal treatment group survival was not significantly different from other published survival rates after extracorporeal CO2 removal. Mechanical ventilation patient group survival was significantly higher than the 12% derived from published data (p = 0.0001). Protocols controlled care 86% of the time. Average PaO2 was 59 mm Hg in both treatment groups. Intensity of care required to maintain arterial oxygenation was similar in both groups (2.6 and 2.6 PEEP changes/day; 4.3 and 5.0 FIO2 changes/day). We conclude that there was no significant difference in survival between the mechanical ventilation and the extracorporeal CO2 removal groups. We do not recommend extracorporeal support as a therapy for ARDS. Extracorporeal support for ARDS should be restricted to controlled clinical trials.

Dose-response pharmacology of intrathecal morphine in human volunteers

BACKGROUND

Intrathecal morphine sulfate (ITMS) administration was introduced into clinical practice in 1979. Inadequate information exists delineating ITMS respiratory effects in the dosage range most frequently employed today. This study evaluated 0.2, 0.4, and 0.6 mg ITMS in male volunteers.

METHODS

Twenty healthy, young, adult male volunteers received 0.0, 0.2, 0.4, or 0.6 mg preservative-free ITMS in an isobaric solution administered at the L3-L4 interspace in a double-blind randomized fashion. Respiratory function was assessed by finger pulse oximetry (SpO2), respiratory rate, and arterial blood gas analysis via an indwelling arterial catheter and the slope of the ventilatory response to carbon dioxide (VE/CO2). Analgesia was assessed by the effect of ITMS on moderate pain produced by pressure algometry at the tibia. The need for supplemental oxygen, 2 L/min via nasal cannulae, was determined by the failure of verbal and tactile prompts to maintain subjects' SpO2 > or = 85% on more than two occasions. Heart rate, arterial blood pressure, sedation level, pupil size, and the incidence of adverse effects also were documented. All the above measurements were made before and 30 min after ITMS, hourly for 11 h, and then every 2 h for 12 more h.

RESULTS

ITMS produced significant dose-related decreases in SpO2. Mild desaturations (SpO2 > or = 85 and < 90%) occurred in 2 of 5, 3 of 5, and 4 of 5 subjects receiving 0.2, 0.4, and 0.6 mg ITMS, respectively. Moderate to severe desaturations (SpO2 < 85%) occurred in 0 of 5, 2 of 5, and 4 of 5 subjects receiving 0.2, 0.4, and 0.6 mg ITMS, respectively. The need for supplemental oxygen also was significantly related to ITMS dose, with 0 of 5, 1 of 5, and 4 of 5 subjects requiring oxygen after 0.2, 0.4, and 0.6 mg ITMS, respectively. Nasal oxygen administration consistently alleviated hypoxemia. Increases in arterial carbon dioxide tension (PaCO2) and decreases in pH were significantly related to ITMS dose. Peak mean PaCO2s were 42.4, 44.9, and 50.7 mmHg in the 0.2-, 0.4-, and 0.6-mg groups, respectively. These peaks occurred 6.5-7.5 h after ITMS injection. ITMS produced significant dose-related depression of VE/CO2. Maximum mean depressions of VE/CO2 were to 61%, 63%, and 32% of baseline in the 0.2-, 0.4-, and 0.6-mg groups, respectively. These nadirs occurred 3.5-7.5 h after ITMS injection. Some subjects receiving 0.6 mg ITMS experienced profound (< 20% of baseline) and prolonged (< 50% of baseline for up to 20 h) VE/CO2 depression. Magnitude and duration of analgesia after ITMS were dose-related. Changes in heart rate, systolic blood pressure, and respiratory rate were not significantly related to ITMS dose. Hypoxemia was not related to respiratory rate. Although ITMS produced statistically significant dose-related increases in sedation and decreases in pupil size, these changes were small and did not coincide with hypoxemia. ITMS caused dose-related increases in emesis, but the severity of pruritus and urinary retention was unrelated to dose.

CONCLUSION

ITMS produced dose-related analgesia and respiratory depression in nonsurgical healthy, young, adult male volunteers. Respiratory depression was significant after 0.2 or 0.4 mg and profound and prolonged after 0.6 mg. No clinical signs or symptoms, including respiratory rate, reliably indicated hypoxemia. Pulse oximetry reliably detected hypoxemia after ITMS, and supplemental nasal oxygen (2 L/min) effectively corrected this hypoxemia.

Oral transmucosal fentanyl citrate (OTFC) for the treatment of postoperative pain

Oral transmucosal fentanyl citrate (OTFC) has been used in a variety of clinical situations. This study was designed to determine if OTFC could provide analgesia to patients with acute pain after major surgery. Following written informed consent, 38 ASA Physical Status I-III patients undergoing either a total hip replacement or total knee arthroplasty were studied prospectively. The patients were randomly allocated to receive either OTFC (7-10 micrograms/kg) or a placebo identical in appearance to an OTFC unit. General anesthesia was administered for surgery, and patient-controlled analgesia (PCA) with morphine was initiated in all patients. The PCA interval dose was adjusted to provide adequate analgesia as determined by the patient and physician; the PCA lock-out time was not changed. On the morning after surgery, the most recent 12 h of PCA data (milligrams per hour of morphine and PCA attempts per hour) were recorded. OTFC or placebo units were administered at times 0, 4, and 8 h during a 12-h study, resulting in three identical units being completely consumed. PCA data, as well as incidence and severity of any adverse side effects, were recorded during the study and for the next 12 h. Treatment groups were compared for similarity, and study variables were analyzed. Twenty-eight patients completed the study, 13 in the control group and 15 in the OTFC group. There were no significant differences between the study groups as to patients' age, gender, ASA classification, or surgical procedure. In addition, there were no differences between the groups in the number of PCA attempts or delivered dose of morphine during the prestudy or poststudy periods.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthetic techniques during surgical repair of femoral neck fractures. A meta-analysis

Fracture of the hip typically occurs in older women. These patients usually have serious accompanying chronic illnesses. There is a difference of opinion as to the choice of regional versus general anesthesia for surgery in these patients. This meta-analysis compared survival of patients with traumatic femoral neck fractures undergoing operative repair during regional or general anesthesia. The data sources were articles comparing regional and general anesthesia from peer reviewed journals. Thirteen randomized controlled trials were found. Besides 1-month mortality, variables used were estimated operative blood loss and the incidence of deep venous thrombosis. For dichotomous outcomes, two effect measures were calculated: the difference in probabilities and the odds ratio. For blood loss, a continuous variable, the effect measure was the mean difference in blood loss. A random-effects Bayesian meta-analysis was used to combine study data, estimate parameters and create 95% confidence intervals. Only the incidence of deep venous thrombosis was clearly greater for patients receiving general anesthesia, being 31 percentage points higher than for patients receiving regional anesthesia. By the odds ratio, deep venous thrombosis was almost four times more likely following general anesthesia. There was no difference in estimated operative blood loss. By probability difference, mortality was a non-significant 2.7 percentage points less following regional anesthesia. By odds ratio effect measure, death was 1.5 times more likely following general anesthesia, but the lower bound of the 95% confidence interval was close to 1. Meta-analysis does not allow a conclusion that important differences in mortality exist between regional and general anesthesia for traumatic hip fracture surgery.

Fentanyl and sufentanil increase intracranial pressure in head trauma patients

Although opioids frequently are administered to patients with severe head trauma, the effects of such drugs on intracranial pressure are controversial. Nine patients with severe head trauma were studied for the effects of fentanyl and sufentanil on intracranial pressure (ICP). In all patients, ICP monitoring was instituted before the study. Full neuromuscular blockade was achieved with vecuronium bromide before the administration of either fentanyl (3 micrograms.kg-1) or sufentanil (0.6 microgram.kg-1) as an intravenous bolus over a 1-min period in a masked and random fashion. Patients received the other opioid in the same fashion 24 h later. Arterial blood pressure, heart rate, and ICP were recorded continuously for the 1 h after drug administration. Fentanyl was associated with an average ICP increase of 8 +/- 2 mmHg, and sufentanil with an increase of 6 +/- 1 mmHg. These increases were statistically significant. Both drugs produced clinically mild decreases in mean arterial blood pressure (fentanyl, 11 +/- 6 mmHg; sufentanil, 10 +/- 5 mmHg) that nevertheless were statistically significant. No significant changes in heart rate occurred. These results indicate that modest doses of potent opioids can significantly increase ICP in patients with severe head trauma.