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Biomedical subjects

R J Fragen

Publications and source records attributed to R J Fragen.

At least 19 recordsLinked to original sources
PubMed2006

A comparison of the SNAP II and BIS XP indices during sevoflurane and nitrous oxide anaesthesia at 1 and 1.5 MAC and at awakening.

BACKGROUND: Monitoring level of consciousness during anaesthesia, with the ability to predict the intentional or unintentional return to consciousness, is desirable. The purpose of this study was to compare two processed electroencephalographic depth of anaesthesia monitors (SNAP II and BIS XP) during sevoflurane and sevoflurane/nitrous oxide anaesthesia. METHODS: In total, 42 subjects received an interscalene block, followed by general anaesthesia with sevoflurane or sevoflurane/nitrous oxide. The indices were recorded at baseline, at 1.5 and 1.0 minimum alveolar concentration (MAC) equivalents, and during emergence. RESULTS: The SNAP and BIS indices decreased from baseline at 1.5 and 1.0 MAC equivalents, but there was no difference within groups between subjects who received nitrous oxide and those who did not. The SNAP index returned to baseline by 1 min before awakening and was higher than baseline at eye opening, but the BIS index remained below baseline at awakening. There was a bias of -1 (95% CI: -3 to 1) between the SNAP and BIS at baseline; this increased to 21 (95% CI: 19-23) during maintenance of anaesthesia and was 6 (95% CI: 4-8) at awakening. CONCLUSIONS: The SNAP index tracks loss of consciousness and emergence from sevoflurane and sevoflurane/nitrous oxide anaesthesia. There is significant bias between the SNAP and BIS indices and therefore, the indices are not interchangeable. The SNAP index returns to baseline before awakening, whereas the BIS index remains below baseline at awakening, suggesting that the SNAP index may be more sensitive to unintentional awareness.

Adolescent↗
PubMed2001

Impact of the initial doses of rocuronium and pancuronium on subsequent maintenance for neuromuscular block.

PURPOSE: To determine the impact of the neuromuscular blocking agent given for intubation on the duration of effect of multiple maintenance doses of pancuronium and rocuronium. METHODS: Seventy-eight subjects were randomly assigned to receive one of four dosing combinations for intubation and neuromuscular maintenance: rocuronium for intubation and maintenance, rocuronium for intubation and pancuronium for maintenance, pancuronium for intubation and rocuronium for maintenance, or pancuronium for both. Each time that the first twitch response returned to 25% of the baseline value, the duration of the dose was determined and another maintenance dose was administered. The duration of action of the maintenance doses was compared between the groups. RESULTS: Twitch suppression from the first maintenance dose was shorter for subjects who received rocuronium for both doses (Group RR) compared with that for subjects that received pancuronium (Groups PR & PP) as their intubation dose (17.6 vs 34 & 59.8 min, respectively, P < 0.05). Subjects who received rocuronium followed by pancuronium (Group RP) showed a shorter duration of twitch suppression after the first maintenance dose than the group that received pancuronium for both doses (Group PP) (21.3 vs 59.8 min, P < 0.05). By the third maintenance dose, the influence of the intubating dose on the maintenance dose duration had essentially diminished. CONCLUSIONS: For combinations of rocuronium and pancuronium, the duration of twitch suppression after a maintenance dose is only dependent on the first agent given for the first two maintenance doses administered.

Adolescent↗
PubMed2001

The pharmacokinetics of dexmedetomidine in volunteers with severe renal impairment.

UNLABELLED: Dexmedetomidine, an alpha2-adrenergic agonist with sedative and analgesic properties, is mainly cleared by hepatic metabolism. Because the pharmacokinetics of dexmedetomidine have not been determined in humans with impaired renal function, we studied them in volunteers with severe renal disease and in control volunteers. Six volunteers with severe renal disease and six matched volunteers with normal renal function received dexmedetomidine, 0.6 microg/kg, over 10 min. Venous blood samples for the measurement of plasma dexmedetomidine concentrations were drawn before, during, and up to 12 h after the infusion. Two-compartmental pharmacokinetic models were fit to the drug concentration versus time data. We also determined its hemodynamic, respiratory, and sedative effects. There was no difference between Renal Disease and Control groups in either volume of distribution at steady state (1.81 +/- 0.55 and 1.54 +/- 0.08 L/kg, respectively; mean +/- SD) or elimination clearance (12.5 +/- 4.6 and 8.9 +/- 0.7 mL x min(-1) x kg(-1), respectively). However, elimination half-life was shortened in the Renal Disease group (113.4 +/- 11.3 vs 136.5 +/- 13.0 min; P < 0.05). A mild reduction in blood pressure occurred in most volunteers. Although most volunteers were sedated by dexmedetomidine, renal disease volunteers were sedated for a longer period of time. IMPLICATIONS: The pharmacokinetics of dexmedetomidine in volunteers with severe renal impairment differed little from those in volunteers with normal renal function. In addition, there were no clinically significant differences in the hemodynamic responses to dexmedetomidine. However, dexmedetomidine resulted in more prolonged sedation in subjects with renal disease.

Adrenergic alpha-2 Receptor Agonists↗
PubMed2000

Is an infusion pump necessary to safely administer remifentanil?

UNLABELLED: We sought to determine if remifentanil could be administered as safely and effectively from an IV drip as from a calculator pump, because not all anesthesiologists have access to a calculator pump. Forty healthy adults undergoing outpatient knee arthroscopy were premedicated with midazolam, 2 mg. Total IV anesthesia was induced with propofol by bolus (2 mg/kg) and maintained by a continuous infusion of propofol and remifentanil. On a randomized, double-blinded basis, they received, IV, either remifentanil (50 microg/mL) by syringe from an infusion pump or from a bag of saline containing remifentanil 20 microg/mL through a minidrip set. The remifentanil infusion syringe pump rate was 0.4 microg. kg(-1). min(-1) until skin incision and then 0.2 microg. kg(-1). min(-1), whereas that from the bag/minidrip set was set to approximate the delivery rate from the pump. Both a syringe pump and bag/minidrip set infusion were administered to each patient but only one contained remifentanil, that one being determined in a randomized, double-blinded manner. There were no differences in demographic data, time to recovery of open eyes, response to command, ability to speak (approximately 7 min), total dose and time of administration of propofol and remifentanil, the incidence of intraoperative hypotension and bradycardia, and postoperative shivering. We demonstrated that remifentanil can be administered as safely and effectively from a bag with a minidrip set as from a syringe in a calculator infusion pump, provided the anesthesiologist is paying attention to the drip rate from the bag. IMPLICATIONS: Because remifentanil is rapidly degraded in the body, it can be safely and effectively administered from a bag through a minidrip set. We showed that there was no difference with this less expensive method of administration than from the more precise method of a calculator infusion pump.

Adolescent↗
PubMed1999

Comparison of renal function following anesthesia with low-flow sevoflurane and isoflurane.

STUDY OBJECTIVE: To evaluate postoperative renal function after patients were administered sevoflurane under conditions designed to generate high concentrations of compound A. STUDY DESIGN AND SETTING: A multicenter (11 sites), multinational, open-label, randomized, comparative study of perioperative renal function in patients who have received low-flow (< or = 1 L/min) sevoflurane or isoflurane. PATIENTS: 254 ASA physical status I, II and III patients requiring endotracheal intubation for elective surgery lasting more than 2 hours. INTERVENTIONS: After induction, low-flow anesthesia was initiated at a flow rate < or = 1 L/min. Blood and urine samples were studied to assess postoperative renal function. MEASUREMENTS AND MAIN RESULTS: Measurements of serum BUN and creatinine, and urine glucose, protein, pH, and specific gravity were used to assess renal function preoperatively and up to 3 days postoperatively. Serum inorganic fluoride ion concentration was measured at preinduction, emergence, and 2, 24 and 72 hours postoperatively. Compound A concentrations were measured at two sites for those patients receiving sevoflurane. Adverse experience data were analyzed. One hundred eighty-eight patients were considered evaluable (98 sevoflurane and 90 isoflurane). Peak serum fluoride concentrations were significantly higher after sevoflurane (40 +/- 16 microM) than after isoflurane (3 +/- 2 microM). Serum creatinine and BUN decreased in both groups postoperatively; glucosuria and proteinuria occurred in 15% to 25% of patients. There were no clinically significant differences in BUN, creatinine, glucosuria, and proteinuria between the low-flow sevoflurane and low-flow isoflurane patients. CONCLUSIONS: There were no statistically significant differences in the renal effects of sevoflurane or isoflurane in surgical patients undergoing low-flow anesthesia for up to 8 hours. Low-flow sevoflurane anesthesia under clinical conditions expected to produce high levels of compound A appears as safe as low-flow isoflurane anesthesia.

Anesthetics, Combined↗
PubMed1999

Effect of dexmedetomidine on the minimum alveolar concentration (MAC) of sevoflurane in adults age 55 to 70 years.

STUDY OBJECTIVE: To determine the effect of two target dexmedetomidine infusions (0.3 ng/ml and 0.6 ng/ml) on the minimal alveolar concentration (MAC) of sevoflurane in adults age 55 to 70 years. DESIGN: Prospective, randomized, placebo-controlled study. SETTING: University-affiliated hospital. PATIENTS: 45 ASA physical status I and II adults, age 55 to 70 years, undergoing elective surgery with at least a 3 inch skin incision. INTERVENTIONS: Patients were given a dexmedetomidine or placebo infusion for at least 15 minutes before anesthetic induction with sevoflurane in oxygen by face mask. After tracheal intubation, a target sevoflurane concentration was maintained for 15 minutes while the dexmedetomidine or placebo infusion continued to run. MEASUREMENTS AND MAIN RESULTS: At the time of skin incision, two observers independently determined movement or nonmovement to the incision. Blood samples for dexmedetomidine were taken before the infusion and at the time of skin incision. The dexmedetomidine plasma concentrations were 0 before infusion with all treatment groups. At the time of incision, they were 0 in the placebo group, 0.39 +/- 0.13 ng/ml in the 0.3 ng/ml target group, and 0.7 +/- 0.13 ng/ml in the 0.6 ng/ml target group. The MAC of sevoflurane was 1.83% in the placebo group, 1.78% in the 0.3 ng/ml target dexmedetomidine group, and 1.51% in the 0.6 ng/ml target dexmedetomidine group. CONCLUSIONS: Dexmedetomidine 0.7 ng/ml decreased the MAC of sevoflurane by 17%, whereas there was no difference between the placebo and the dexmedetomidine 0.39 ng/ml group.

Adrenergic alpha-Agonists↗
PubMed1999

The effect of remifentanil on biliary tract drainage into the duodenum.

UNLABELLED: Opioids cause spasm of the sphincter of Oddi. Remifentanil is metabolized enzymatically throughout the body. Its context-sensitive half-time is 3-4 min. The effect of remifentanil on the sphincter of Oddi, is unknown. We studied, in six healthy adult volunteers, the effect of remifentanil on the flow of dye from the gall bladder into the duodenum. Control hepatobiliary imaging with 5 mCi of technetium-labeled derivatives of iminodiacetic acid was performed on each volunteer. The time from IV dye (radiopharmaceutical) injection until its appearance in the duodenum was determined by continuous scanning. Two weeks later, each volunteer received remifentanil, 0.1 microg x kg(-1) x min(-1) infused for 30 min IV before the same dose of technetium-labeled derivatives of iminodiacetic acid was injected, and for the time of their control scan plus 10 min after the injection. When the dye appeared in the duodenum, the total time from injection was compared with the control value. The time from stopping the infusion until the dye appeared in the duodenum was the "recovery time." Control scan time was 20.5+/-9.9 min (mean +/- SD; range 10-33 min). Total scan time during and after the remifentanil infusion was 50.3+/-17.3 min (range 30-81 min) (P < 0002). The recovery time was 19.8+/-12.4 min (range 5-40 min). We conclude that remifentanil delays the drainage of dye from the gall bladder into the duodenum, but the delay is shorter than that reported after other studied opioids. IMPLICATIONS: Radioactive dye was injected IV into healthy volunteers to determine the time it took for the dye to appear in the duodenum. This was repeated under the influence of a short-acting narcotic analgesic, remifentanil. Remifentanil caused a much shorter delay than previously reported after morphine or meperidine.

Adult↗
PubMed1999

Factors affecting the pharmacokinetic characteristics of rapacuronium.

BACKGROUND: Rapacuronium is a new nondepolarizing muscle relaxant with rapid onset and offset. As part of a study to determine its neuromuscular effects, the authors sampled plasma sparsely to determine the influence of age, gender, and other covariates on its pharmacokinetic characteristics. METHODS: Of 181 patients receiving a single bolus dose of 0.5-2.5 mg/kg rapacuronium, 43 (aged 24-83 yr) had plasma sampled 3 or 4 times to determine plasma concentrations of rapacuronium and its metabolite, ORG9488. Pharmacokinetic analysis was performed using a population approach (mixed-effects modeling) to determine the influence of demographic characteristics and preoperative laboratory values on the pharmacokinetic parameters. RESULTS: Rapacuronium's weight-normalized plasma clearance was 7.03 x (1 - 0.0507 x (HgB - 13)) ml x kg(-1) x min(-1), where HgB is the patient's preoperative value for hemoglobin (g/100 ml); however, rapacuronium's blood clearance (11.4+/-1.4 ml x kg(-1) x min(-1), mean +/- SD) did not vary with hemoglobin. Rapacuronium's weight-normalized pharmacokinetic parameters were not influenced by age, gender, or other covariates examined. Plasma concentrations of ORG9488 were typically less than 14% those of rapacuronium during the initial 30 min after rapacuronium administration. CONCLUSIONS: In this patient population, neither age nor gender influence elimination of rapacuronium. This finding contrasts to an age-related decrease in plasma clearance observed in a study of 10 healthy volunteers and in a pooled analysis of the pharmacokinetic data from 206 adults in multiple clinical studies. Even if ORG9488 has a potency similar to that of rapacuronium, its plasma concentrations after a single bolus dose of rapacuronium are sufficiently small to contribute minimally to neuromuscular blockade.

Adult↗
PubMed1997

Dose-ranging study in younger adult and elderly patients of ORG 9487, a new, rapid-onset, short-duration muscle relaxant.

The purpose of this multicenter, randomized, assessorblind placebo-controlled study was to determine which of five doses of the new, rapid-onset neuromuscular relaxant, ORG 9487, provided both good to excellent tracheal intubating conditions 60 s after administration and a clinical duration of action < 20 min in 120 younger (aged 18-64 yr) and 61 elderly (aged 65-85 yr) adult patients. Anesthesia was induced with fentanyl (2-5 micrograms/kg) and thiopental (3-6 mg/kg) and maintained with N2O/O2 and a propofol infusion (50-300 micrograms.kg-1.min-1). Neuromuscular train-of-four (TOF) monitoring by electromyography (Datex Relaxograph) commenced immediately after anesthetic induction and was followed, within 30 s, by one of five doses of ORG 9487 (0.5, 1.0, 1.5, 2.0, 2.5 mg/kg) or a placebo. Tracheal intubation was attempted at 60 s and again, in the case of failure, at 90 s. Conditions were assessed with a 4-point scale. Maximum block, clinical duration (time to 25% T1 recovery), and recovery (TOF > or = 0.7) were measured. Dose-dependent changes were observed in tracheal intubating conditions and neuromuscular block. Good to excellent intubating conditions at 60 s were present in most younger adult (52 of 60) and elderly (26 of 31) patients administered doses > or = 1.5 mg/kg. Mean clinical durations < 20 min were observed in adult patients at doses up to 2.0 mg/kg and in geriatric patients up to 1.5 mg/kg. Thus, doses of 1.5-2.0 mg/kg ORG 9487 enabled both rapid tracheal intubation and a short clinical duration of action in adult and elderly patients.

Adolescent↗
PubMed1997

A comparison of oral ketorolac and hydrocodone-acetaminophen for analgesia after ambulatory surgery: arthroscopy versus laparoscopic tubal ligation.

This multicenter study compared the analgesic efficacy and side effects of ketorolac and hydrocodone-acetaminophen when administered orally after ambulatory arthroscopic or laparoscopic tubal ligation procedures. After awakening from general anesthesia, 252 patients experiencing moderate or severe postoperative pain were randomly assigned to receive one of three analgesic treatments according to a placebo-controlled, double-blind protocol. Group 1 (n = 83) received oral ketorolac 10 mg every 6 h for up to 3 days, Group 2 (n = 82) received hydrocodone 7.5 mg plus acetaminophen 750 mg every 6 h for up to 3 days, and Group 3 (n = 87) received placebo capsules followed by ketorolac 10 mg every 6 h for up to 3 days. Severity of pain was recorded using a 4-point categorical score and visual analog scale (VAS) at 0.5 h and subsequently at hourly intervals for 6 h, as well as daily for up to 3 days. Pain relief was recorded using a 5-point categorical scale at the same time points. In the patients undergoing arthroscopic surgery, both ketorolac and hydromorphone-acetaminophen provided superior pain relief compared with the placebo. Although the categorical summed pain intensity difference (SPID), VAS SPID, and total pain relief scores were higher in the ketorolac group compared with the hydrocodone-acetaminophen group, the differences were not statistically significant. In the patients undergoing laparoscopic tubal ligation surgery, the three treatment groups displayed similar responses to the study medications. However, the ketorolac group scored higher in terms of overall tolerability than the hydrocodone-acetaminophen group. In conclusion, there was no difference in the efficacy between oral ketorolac and hydrocodone-acetaminophen combination in controlling pain after outpatient arthroscopic surgery procedures. Neither oral analgesic proved to be very effective after laparoscopic tubal ligation.

Acetaminophen↗
PubMed1996

The minimum alveolar concentration (MAC) of sevoflurane with and without nitrous oxide in elderly versus young adults.

STUDY OBJECTIVE: To determine the minimum alveolar concentration (MAC) of sevoflurane with and without 65% nitrous oxide (N2O) in non-Asian patients at least 70 years of age, and in patients aged 18 to 35 years. DESIGN: Randomized open-study design. The Dixon up-down method determined the target sevoflurane concentration for each patient. SETTING: Operating rooms of a large university hospital. PATIENTS: 27 ASA status I and II patients aged 18 to 35 years and 26 patients at least 70 years of age, who were free of any conditions or diseases that would interfere with MAC determination. INTERVENTIONS: Unpremedicated patients breathed sevoflurane until the predetermined target end-tidal sevoflurane concentration was reached for at least 15 minutes before skin incision. Up-down sevoflurane increments were 0.25% after an initial target concentration of 2%. This continued until there were at least three crossover pairs in each of the four groups. MEASUREMENTS AND MAIN RESULTS: Patients were observed for purposeful movement in response to a skin incision. End-tidal sevoflurane, N2O and oxygen (O2) concentrations were measured by a calibrated infrared analyzer. MAC was determined by logistic regression analysis. The MAC of sevoflurane in O2/air for the mean age in each group was 2.6% in the younger group (age = 25 yr) and 1.45% in the elderly group (age = 76 yr). Nitrous oxide 65% decreased MAC about 50% in each group at any age studied. CONCLUSIONS: The MAC of sevoflurane determined in this study is similar to that determined in previous studies, including the MAC determined in an elderly Asian population. Increasing age and N2O decrease sevoflurane MAC similarly to that determined with other volatile anesthetics.

Adolescent↗
PubMed1995

Initial clinical experience with remifentanil, a new opioid metabolized by esterases.

Remifentanil is a new, esterase-metabolized opioid for anesthesia. Nonspecific esterases terminate the drug effect, with a context-sensitive half-time which plateaus at 3-4 min. This dose-ranging pilot study was designed to estimate the dose requirement of remifentanil for abolition of the responses to skin incision and intraoperative stimuli, and to determine the speed of recovery. Fifty-one unpremedicated patients took part at two centers. Anesthesia was induced with propofol, 67% nitrous oxide, and vecuronium. Remifentanil was then given (1 microgram/kg, plus an infusion of 0.0125-1.0 micrograms.kg-1.min-1). Responses were defined as: > 15% increase in systolic blood pressure or > 20% increase in heart rate, tearing, sweating, movement, or coughing. Responses to incision or surgery were treated with 0.5 micrograms/kg remifentanil boluses and a 50% increase in infusion rate, which could be done twice. Subsequent responses were treated with propofol or isoflurane. Remifentanil and nitrous oxide administration were terminated after the incision was closed. ED50 for response to skin incision varied between the two study sites (0.020 and 0.087 microgram.kg-1.min-1). ED50 for response to all surgical stimuli was 0.52 microgram.kg-1.min-1. At 0.3 microgram.kg-1.min-1 or more, only 3 of 21 patients required isoflurane. Recovery was not longer in patients receiving larger doses to spontaneous ventilation (2.5-4.6 min), tracheal extubation (4.2-7.0 min), and response to verbal command (3.0-4.6 min). Postoperative pain was reported in most patients (92%) at a median time of 21 min. We conclude that remifentanil was effective and well tolerated as a component of nitrous oxide-opioid-relaxant anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Effect of ketorolac tromethamine on bleeding and on requirements for analgesia after total knee arthroplasty.

The effect of ketorolac tromethamine, a non-steroidal anti-inflammatory drug, on postoperative blood loss and on the requirement for morphine was assessed after total knee arthroplasty, an operation in which blood loss is mainly measured rather than estimated. The purpose of this prospective, randomized, double-blind clinical trial was to determine whether administration of ketorolac in the perioperative period would increase bleeding related to the operation. Fifty-nine patients who had a total knee arthroplasty received either thirty milligrams of ketorolac or a placebo consisting of saline solution, intravenously, every six hours, in four doses. The first dose was administered about an hour before the end of the operation. Blood loss and use of morphine for pain control were measured for the first twenty-four hours postoperatively. The per cent change in the hematocrit and the amount of transfused blood were also recorded. The patients who received ketorolac used 27 per cent less morphine than those who received the placebo (40.0 +/- 23.4 milligrams compared with 55.1 +/- 23.5 milligrams [mean and standard deviation]); this difference was significant (p < 0.05). On the first day after the operation, the hematocrit decreased from 0.364 +/- 0.043 preoperatively to 0.278 +/- 0.032 in the patients who received ketorolac and from 0.363 +/- 0.046 to 0.298 +/- 0.030 in the patients who received the placebo. The 6 per cent greater decrease in the group that received ketorolac was significant (p < 0.05) but not clinically important.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

A randomized, double-blind evaluation of ketorolac tromethamine for postoperative analgesia in ambulatory surgery patients.

BACKGROUND: Given the trend toward early discharge of patients after surgery and the inherent adverse effects of opioid analgesics, we compared a new nonsteroidal antiinflammatory drug, ketorolac tromethamine, given intravenously (iv) and then orally, with two commonly prescribed opioid analgesics in ambulatory patients for up to 1 week after surgery. METHODS: In this study incorporating a double-blind, multi-dose design, 221 patients who had moderate or severe pain after surgery were randomized to one of three treatment groups: group K30 received 30 mg iv ketorolac twice, then 10 mg iv every 30 min as required to control pain, up to six doses, followed by 10 mg oral ketorolac every 4-6 h; group F50 received 50 micrograms iv fentanyl at the same time intervals as in group K30, followed by 60 mg codeine plus 600 mg acetaminophen (C+A) orally every 4-6 h; and group F10 received the same combination as did group F50, but only 10 micrograms fentanyl per dose. RESULTS: Compared with 50 micrograms fentanyl iv, 30 mg iv ketorolac provided delayed but otherwise equivalent analgesic effects and was associated with similar side effects. Compared with C+A, 10 mg oral ketorolac was associated with a lower incidence of nausea and somnolence and earlier return of bowel function but not better pain relief, drug tolerability, quality of life, or psychologic well-being. CONCLUSIONS: Ketorolac, when used in an iv and then oral sequence, is a safe and effective analgesic in the ambulatory surgery setting. It has a slower onset than fentanyl, but causes fewer side effects than C+A.

Administration, Oral↗
PubMed1993

Continuous intravenous infusion of rocuronium (ORG 9426) in patients receiving balanced, enflurane, or isoflurane anesthesia.

BACKGROUND: Rocuronium (ORG 9426) is a new nondepolarizing neuromuscular blocking agent with a rapid onset and an intermediate duration of action. This study obtains the infusion requirements of rocuronium in 30 patients in whom anesthesia was maintained with barbiturate-nitrous oxide-opioid, nitrous oxide and enflurane, or nitrous oxide and isoflurane. METHODS: For all 30 patients, anesthesia was induced with intravenous thiopental and fentanyl, followed by 0.45 mg/kg rocuronium. Patients were randomly allocated to receive either: 1) nitrous oxide in 40% oxygen supplemented with fentanyl, thiopental, and droperidol (balanced anesthesia), 2) 1.25 MAC enflurane-nitrous oxide, or 3) 1.25 MAC isoflurane-nitrous oxide. Once blockade had recovered to 95% depression of twitch height, muscle relaxation was maintained by continuous infusion of rocuronium, adjusted to maintain mechanical twitch response at 95% depression. RESULTS: At 90 and 120 min, the enflurane and isoflurane groups had lower infusion requirements than those receiving barbiturate-nitrous oxide-opioid anesthesia (P < 0.02), but these did not differ significantly between the two volatile agents. Final infusion requirements (mean +/- SD) were 9.8 +/- 3.7, 5.9 +/- 3.1, and 6.1 +/- 2.7 micrograms.kg-1.min-1 for the groups receiving barbiturate-nitrous oxide-opioid, enflurane, and isoflurane anesthesia, respectively. Spontaneous recovery began soon after termination of the infusion; in all patients, twitch tension equaled 10% of control within 5 min. CONCLUSIONS: The infusion requirements to maintain 95% twitch depression approximated 10 micrograms.kg-1.min-1 during barbiturate-nitrous oxide-opioid anesthesia. These requirements were reduced by 40% during anesthesia involving enflurane or isoflurane.

Adult↗
PubMed1993

Determinants of thiopental induction dose requirements.

Dose requirements for thiopental anesthetic induction have significant age- and gender-related variability. We studied the association of the patient characteristics age, gender, weight, lean body mass, and cardiac output with thiopental requirements. Doses of thiopental, infused at 150 mg/min, required to reach both a clinical end-point and an electroencephalographic (EEG) end-point were determined in 30 males and 30 females, aged 18-83 yr. Univariate least squares linear regression analysis revealed outliers in the relationships of age, weight, lean body mass, and cardiac output to thiopental dose at clinical and EEG endpoints. Differential weighting of data points minimized the effect of outliers in the construction of a robust multiple linear regression model of the relationship between several selected independent variables and the dependent variables thiopental dose at clinical and EEG endpoints. The multiple linear regression model for thiopental dose at the clinical end-point selecting the regressor variables age, weight, and gender (R2 = 0.76) was similar to that for age, lean body mass, and gender (R2 = 0.75). Thiopental dose at the EEG endpoint was better described by models selecting the variables age, weight, and cardiac output (R2 = 0.88) or age, lean body mass, and cardiac output (R2 = 0.87). Although cardiac output varied with age, age always remained a selected variable. Because weight and lean body mass differed with gender, their selection as variables in the model eliminated gender as a selected variable or minimized its importance.

Adult↗
PubMed1991

Dose-finding study of intramuscular midazolam preanesthetic medication in the elderly.

Intramuscular midazolam frequently results in excessive sedation in elderly patients. The effects of preanesthetic medication with intramuscular midazolam were examined in 100 elderly patients, aged 60-86 yr, given 1, 2, or 3 mg midazolam or placebo using a randomized, double-blind study design. Level of sedation and anxiety were assessed every 15 min for 1 h. Picture cards were presented at the same times in order to assess recall of these cards 24 h later. All three doses of midazolam produced rapid onset of sedation, anxiolysis, and anterograde amnesia. These effects decreased in intensity by 60 min after drug injection. The intensity and extent of these effects were comparable with those reported with higher doses in younger patients, although with the 1-mg midazolam dose the effects were shorter-lived, and a difference from placebo was not consistently seen. Three patients (3%), all older than 70 yr, became unresponsive to vocal and tactile stimuli. This level of drowsiness was unrelated to body weight, age, or ASA physical status. We conclude that in adults between 60-69 yr old, midazolam 2 or 3 mg intramuscularly can be effective as preanesthetic medication without causing excessive drowsiness. However, intramuscular midazolam should be used cautiously, under continuous observation, in patients aged 70 yr and older because excessive drowsiness may occur.

Aged↗