Mean Induction Dose Research Articles

The effect of dexmedetomidine infusion on propofol requirement for maintenance of optimum depth of anaesthesia during elective spine surgery

Background:Maintenance of adequate depth of anaesthesia in spine surgery is vital to prevent awareness, to reduce stress response and possible autonomic instability frequently associated with spine surgery. Dexmedetomidine, a α2-adrenoceptor agonist with analgesic and sedative adjuvant property has been found to reduce dose requirement of multiple anaesthetic agents both for induction and during the maintenance of anaesthesia.Aim:The aim of this study is to observe the effect of dexmedetomidine, on the requirement of propofol for induction and maintenance of adequate depth of anaesthesia during spine surgery.Methods:It was a prospective, randomised, double-blinded, parallel group, placebo controlled and open-lebel study in tertiary care hospital. A total of 70 patients aged 20-60 years, American Society of Anaesthesiologists GradeI and II, scheduled for elective spine surgery were randomly allocated into two groups. Each patient of Group D (n=35) received an initial loading dose of dexmedetomidine at 1 μg/kg over 10 min, started 15 min before induction of anaesthesia followed by an infusion at a rate of 0.2 μg/kg/h. Patients of Group P (n=35) received the same volume of 0.9% normal saline solution as placebo. Requirement of propofol at induction and during maintenance was calculated maintaining bispectral index between 40 and 60. P<0.05 was considered to be statistically significant.Results:Mean requirement of propofol was found to be lessened by 48.08% and 61.87% for induction and maintenance of anaesthesia respectively while using dexmedetomidine.Conclusion:Administration of dexmedetomidine significantly reduces the requirement of propofol while maintaining desired depth of anaesthesia without any significant complication.

Nonanesthesiologist-Administered Propofol Versus Midazolam and Propofol, Titrated to Moderate Sedation, for Colonoscopy: A Randomized Controlled Trial

Nonanesthesiologist-administered propofol (NAAP) is controversial due to deep sedation concerns. The purpose of this study was to evaluate the feasibility of moderate sedation with two different NAAP regimens for colonoscopy. This was a double-blinded, randomised, placebo-controlled trial allocating 135 consecutive outpatients to placebo (group P) or midazolam 2 mg (group M+P) before NAAP targeted to moderate sedation. Depth of sedation every 2 min throughout the procedure, propofol doses, recovery times, complications and patient and endoscopist satisfaction were measured. A total of 84 % of assessments of the depth of sedation were moderate. Mean induction (76 [40-150] vs. 53 [30-90]) and total propofol doses (mg) (136 [60-270] vs. 104 [50-190]) were significantly higher for group P (p < 0.001). However, deep sedation was significantly more prevalent in group M+P in minutes 4 (16 vs. 1 %, p = 0.05), 6 (20 vs. 3.5 %, p = 0.046) and 8 (17 vs. 1.8 %, p = 0.06) of the procedure, coinciding with midazolam peak action. From minute 8 on, moderate sedation was significantly deeper for M+P (p = 0.002). Early recovery time (6.8 min vs. 5.2, p = 0.007), but not discharge time (10.4 min vs. 9.8, p = 0.5), was longer for M+P. Pain perception (P 1.03 vs. M+P 0.3, p = 0.009) and patient satisfaction scores (P 9.4 vs. M+P 9.8, p = 0.047) were better for M+P. No major complications occurred. Moderate sedation was feasible with both NAAP regimens. Drug synergy in the midazolam plus propofol sedation regimen promotes a deeper and longer moderate sedation, improving patient satisfaction rates but prolonging early recovery time (Clinical Trials gov NCT01428882).

Induction Dose of Propofol for Pediatric Patients Undergoing Procedural Sedation in the Emergency Department

This study aimed to determine if patient age is an independent predictor of the propofol dose required for the induction of sedation in pediatric patients for procedures performed in the emergency department (ED). This is a retrospective study conducted in an academic, tertiary ED between May 2005 and October 2009. Medical records of patients younger than 18 years who received propofol for procedural sedation were evaluated. Data collected included patient demographics, procedure type, propofol doses administered, time to sedation induction, pain scores before procedure, opioid administration, and adverse effects. Factors predictive of propofol induction dose were analyzed using linear regression analyses. Eighty-eight patients were included in the final analyses. The mean age was 11 years (range, 1-17 years), and 75% were male. The mean induction dose required was 2.1 ± 1.3 mg/kg using a median of 3 boluses (interquartile range, 2-4). The mean time to induction was 3.9 ± 4.2 minutes. In the linear regression analyses (R = 0.07), patient age was inversely predictive of the induction dose (in milligram per kilogram) of propofol (coefficient = -0.074; P = 0.013). Sex, race, procedure type, pain score before procedure, and opioid administration were not predictive of induction dose. Transient respiratory depression occurred in 13.6% and hypotension occurred in 8% of patients, without further complications. In pediatric patients undergoing procedural sedation in the ED, age is an independent predictor of the dose of propofol required for induction of sedation. Therefore, younger patients may require higher doses by body weight (in milligram per kilogram).

Induction of anaesthesia with alfaxalone or propofol before isoflurane maintenance in cats

Thirty-nine healthy cats that were presented for ovariohysterectomy received intramuscular acepromazine (0.05 mg/kg) and subcutaneous meloxicam (0.3 mg/kg) as preanaesthetic medication. They were then randomly assigned to receive either propofol...

Dexmedetomidine for Procedural Sedation in Children With Autism and Other Behavior Disorders

Dexmedetomidine has been increasingly in use for pediatric noninvasive procedural sedation. This retrospective study examined experience in children with autism and other neurobehavioral disorders, populations often difficult to sedate. Records of children with autism or neurobehavioral disorders sedated with dexmedetomidine at Chris Evert Children's Hospital and Kosair Children's Hospital were reviewed. Demographic and sedation-related data were collected, including sedative doses, time to sedation, efficacy, and complications. Comparisons of sedative doses, efficacy between autism and neurobehavioral patients, and analysis of age-related factors were performed. In all, 315 patients were sedated, most commonly for magnetic resonance imaging. Mean induction and total dexmedetomidine doses were 1.4 +/- 0.6 and 2.6 +/- 1.6 microg/kg, respectively, with no differences between autism and neurobehavior patients. Most patients (90%) patients received concomitant midazolam. There was an age-related decrease in dexmedetomidine dose, independent of midazolam use. Seven patients required intervention for hypotension, bradycardia, or both, and only one adverse respiratory event (obstruction requiring nasopharyngeal airway placement) occurred. There were two episodes of overt recovery-related agitation. All but four procedures were successfully completed (4/315, or 98.7%). Dexmedetomidine with or without midazolam was an effective sedative in this population. The regimen appeared to be well tolerated with few adverse events, including recovery-related agitation, and appears to be an attractive option for this population.

Pediatric Procedural Sedation by a Dedicated Nonanesthesiology Pediatric Sedation Service Using Propofol

To evaluate the success and dosing requirements of propofol in children for prolonged procedural sedation by a nonanesthesiology-based sedation service. The pediatric sedation service at this institution uses propofol as its preferred sedative, and the local guideline suggests using 3 mg/kg for induction and 5 mg kg(-1) h(-1) for maintenance sedation. Doses can be adjusted as needed to individualize successful sedation. A retrospective analysis of patients sedated for 30 minutes or longer was conducted. Patients were stratified into 4 cohorts based on age (<1 year [n = 16], 1-2 years [n = 85], 3-7 years [n = 54], and >7 years [n = 55]) and dosing patterns, success, and adverse effects were investigated. Two hundred forty-nine patients met the inclusion criteria. Mean age was 4.8 years (SD, 4.1). The mean induction dose was 3.2 mg/kg (range, 0.9-9.7), and the mean maintenance infusion was 5.2 mg kg(-1) h(-1) (range, 0.14-21.3). No differences were seen in the induction doses in the different age cohorts, yet the SD was largest in the youngest cohort compared to any other. Although no differences were seen in maintenance rates by age, the greatest SD for dosing was seen in the oldest cohort. For all ages, all sedations were successful (100%) and unanticipated adverse effects rare (<1%). Although it seems that the mean dosing of propofol does not vary significantly with age, there is greater variability in induction dosage for those younger than 1 year and in maintenance dosing for those 7 years or older. The results and general dosing parameters may assist pediatric subspecialists in using propofol for prolonged procedural sedation.

Propofol anesthesia in spontaneously breathing children undergoing magnetic resonance imaging: comparison of two propofol emulsions

This study evaluated a propofol-based anesthesia regimen with spontaneous breathing in pediatric patients scheduled for magnetic resonance imaging (MRI). In this prospective, randomized, double-blind study propofol formulated with long-chain triglycerides (LCT) and mixed medium-chain/long-chain triglycerides (MCT/LCT) were used. Ninety patients aged 2.4 months to 7.3 years were premedicated with intravenous midazolam. Lidocaine was injected prior to propofol to reduce injection pain. Anesthesia was induced and maintained by propofol. Glycopyrronium bromide was administered for saliva reduction. Hemodynamics, blood oxygen saturation and endtidal capnography were continuously monitored. All patients received additional oxygen. The aggregated propofol dose for induction and maintenance of anesthesia was analyzed for therapeutic equivalence. Incidence of injection pain, laboratory safety values, vital signs, and the adverse event profile were analyzed to compare tolerability and safety. Propofol anesthesia was safe and successful in all children. Both propofol formulations were equivalent regarding dose requirements (mean induction and maintenance doses for anesthesia 2.0-4.0 mg.kg(-1) and 6.0-8.8 mg.kg(-1).h(-1) respectively; aggregated doses 8-13.26 mg.kg(-1)). There were no differences in drug safety such as hemodynamics, spontaneous breathing, injection pain, and laboratory values. Duration of induction and of recovery from anesthesia were short and all examinations were completed with minimal interruption. Propofol-based short-term anesthesia was well suited for anesthesia during MRI procedures in the studied pediatric patients. There were no clinically relevant differences between the two propofol formulations.

The safe and effective use of propofol sedation in children undergoing diagnostic and therapeutic procedures: experience in a pediatric ICU and a review of the literature.

To describe our experience using propofol sedation to facilitate elective diagnostic and therapeutic procedures, and to document the safety profile of propofol in this setting. Retrospective consecutive case series and review of the literature. Pediatric intensive care unit of a United States Navy tertiary care medical center. Children receiving propofol for procedural sedation over an 18-month period. Descriptive features of sedation including adverse events. During the study period, 91 children received propofol to facilitate the performance of 110 medical procedures. The mean induction dose was 2.41 mg/kg, the mean infusion rate was 179.3 microg/kg/min, and the mean total dose of propofol administered was 4.23 mg/kg. In all cases, sedation was successfully achieved. The average length of stay in the PICU was 108.4 minutes. Three children (3.3%) had transient episodes of oxygen desaturation that improved with repositioning of the airway. No child required placement of an endotracheal tube. Three (3.3%) children experienced hypotension requiring a decrease in the infusion rate of propofol and a 10-mL/kg bolus infusion of normal saline. No cardiac arrhythmias or adverse neurologic effects secondary to propofol infusion were identified. Pediatric intensivists can safely and effectively administer propofol to facilitate the performance of diagnostic and therapeutic procedures outside the operating room setting.

Propofol in an Emulsion of Long- and Medium-Chain Triglycerides: The Effect on Pain

Propofol in an Emulsion of Long- and Medium-Chain Triglycerides: The Effect on Pain

Titration of propofol infusion using processed electroencephalogram during combined general and spinal anesthesia.

To determine the necessary mean infusion rate of propofol during combined nitrous oxide (N2O) and propofol spinal anesthesia by using the processed electroencephalogram (pEEG). Twelve elective gynecological patients were monitored by a Dräger pEEG monitor under N2O and propofol spinal anesthesia. To make it easier to detect an inadequate depth of anesthesia, muscle relaxants were not given and the patients breathed spontaneously through a laryngeal mask airway. Manual step-down infusion of propofol was employed to provide intraoperative hypnosis. Propofol infusion was titrated to maintain cardiorespiratory parameters within 20% of baseline and the 90th percentile of the spectral edge frequency (SEF 90) of the pEEG between 10 and 13.5 Hz. The mean (SD) induction dose of propofol was 2.9 (0.4) mg·kg-1. The mean (SD) maintenance infusion rate was 4.2 (0.5) mg·kg-1·h-1. The mean (SD) time from the end of propofol infusion to the opening of the patient's eyes was 5.4 (2.0) min. No gross movements or intraoperative awareness was recognized. The mean (SD) SEF 90 during the maintenance of anesthesia was 12.2 (1.5) Hz, which increased significantly to 16.2 (1.9) Hz at 1 min before the patients opened their eyes in reponse to verbal commands. Titration of propofol infusion using SEF during combined general and spinal anesthesia provided a rapid recovery without any clinical signs of inadequate anesthesia.

Perioperative Sympatholysis

Perioperative Sympatholysis

Induction characteristics of two brands of propofol in children

Propofol, a novel intravenous agent used to induce and maintain anesthesia, commonly causes pain at the injection site on administration. This parallel-group, randomized, double-masked study was designed to compare the induction characteristics of two commercially available brands of propofol in children, with attention paid to pain on injection. Fifty consecutive American Society of Anesthesiologists class I or II children aged 4 to 11 years who were scheduled for minor surgery were randomly divided into two equal groups to receive Recofol ® (Leiras, Turku, Finland, n = 25) or Diprivan ® (Zeneca, Cheshire, United Kingdom, n = 25). Propofol 1.5 mg/kg was injected at a rate of 0.5 mL/s, and injection pain was then assessed. After the assessment, supplemental propofol was administered until eyelid reflex disappeared. Anesthesia was maintained with fentanyl and propofol isoflurane or sevoflurane in nitrous oxide and oxygen. Muscle relaxation was induced and maintained with vecuronium when clinically indicated. Mean induction dose (2.27 ± 0.33 mg/kg and 2.42 ± 0.41 mg/kg) and mean induction time (42 ± 14 seconds and 43 ± 15 seconds) were similar for Recofol and Diprivan, respectively. Two patients in each group reported no pain during injection. Maximum pain (on a five-grade visual analog scale [VAS]) was experienced by 30% of patients (6 of 20) receiving Recofol and by 41% (9 of 22) receiving Diprivan, this difference was not statistically significant. Both groups had a similar incidence of postoperative nausea and vomiting (12% in patients receiving Recofol and 20% in patients receiving Diprivan; this difference was not statistically significant). Our findings suggest that both brands of propofol have similar induction characteristics and similar adverse effects in children.

A Comparative Evaluation of Propofol and Midazolam as Sedative Agents in Fiberoptic Bronchoscopy

Propofol, a new intravenous sedative agent, was investigated in 41 asthmatic patients undergoing day-case (outpatient) fiberoptic bronchoscopy. The study design was a randomized comparison between propofol and midazolam, which is a well-established intravenous sedative agent. The age, weight, and American Society of Anesthesiologists physical status and lung function of the two groups were not significantly different. Mean (SD) induction dose of propofol was 104.7 (30.1) mg with a maintenance dose of 121.9 (38.5) mg. Corresponding values of midazolam were 9.3 (3.1) mg and 3.7 (2.3) mg. The required level of sedation was achieved significantly faster with propofol, mean (SD) 125.4 (39.8) s, compared with midazolam, 179.4 (55.2) s (p < 0.001). Significantly faster recovery was noted with propofol compared with midazolam in terms of time to recall name and date of birth 2.3 (1.7) min vs 6.3 (8.6) min, (p < 0.045). Alertness scored with the digital symbol substitution test (DSST) returned to prebronchoscopy values in the propofol group at 30 min, DSST score = 35.9 (18.2) vs 13.4 (9.1), in the midazolam group (p < .0001) and was still significantly higher at 90 min-39.4 (17.9) and 23.1 (13.8) (p < 0.01). We conclude that propofol is a useful sedating agent in fiberoptic bronchoscopy with similar efficacy to midazolam but with a faster onset of action and a more rapid recovery. These represent significant advantages for day-case procedures.

Alfentanil sedation for cardiac catheterization of children with Fontan shunts.

After Fontan operation, prolonged invasive cardiac assessment is often needed. This study is a clinical evaluation of the effectiveness of flunitrazepam premedication, EMLA cream, and alfentanil continuous infusion for management of children undergoing such catheterization. Fourteen consecutive subjects aged 5-20 yr with Fontan shunts (right atrium to pulmonary artery) undergoing elective haemodynamic and electrophysiological catheterization were sedated with an individually titrated alfentanil infusion. After oral premedication with flunitrazepam 2 mg, the mean induction dose and mean maintenance requirement of alfentanil were 4.4 +/- 2.7 micrograms.kg-1 and 10.3 +/- 8.6 micrograms.kg-1 x hr-1, respectively. Mean oxygen consumption during haemodynamic catheterization was 4.1 +/- 0.4 ml.kg-1 x min-1 with an average individual variation of 10%. For every patient, tranquil and stable conditions during catheterization could be produced. It is concluded that alfentanil infusion is a method of sedation of children and adolescents with Fontan shunts during haemodynamic and electrophysiologic catheterization. However, continuous monitoring of ventilation and an understanding of the slow circulation time after Fontan operation are essential with such sedation in these patients.

The effect of premedication on the induction dose of propofol in dogs and cats

The effect of premedication on the induction dose of propofol was determined in 15 cats and 25 dogs undergoing elective surgical procedures. The induction dose of propofol in dogs younger than 8 years old was 6.9 +/- 0.9 mg kg-1 (n = 4) without premedication and 4.3 +/- 1.4 mg kg-1 (n = 12) with premedication with acetylpromazine maleate. The induction dose in cats younger than 3 years old was 7.8 +/- 1.1 mg kg-1 (n = 8) with atropine alone and 7.1 +/- 0.9 mg kg-1 (n = 7) with the inclusion of acetylpromazine maleate. The reduction in the induction dose of propofol was statistically significant in dogs, but not in cats. When atropine was used together with a fentanyl-droperidol combination or pethidine and acetylpromazine maleate in dogs, the mean induction dose of propofol was reduced to 2.1 +/- 0.1 mg kg-1 (n = 4) and 2.4 +/- 0.3 mg kg-1 (n = 5), respectively. Propofol was also evaluated as an induction agent in patients undergoing non-elective surgical procedures.

Clinical evaluation of propofol as an intravenous anaesthetic agent in cats and dogs

The clinical efficacy and safety of an emulsion containing 10 mg/ml of the intravenous anaesthetic propofol were evaluated in cats and dogs by veterinary surgeons in eight practices in the United Kingdom. A total of 290 dogs and 207 cats were anaesthetised with propofol either as a single injection for procedures of short duration, or as an induction agent with maintenance provided by further incremental injections or as an induction agent with maintenance by gaseous agents. The mean induction doses of propofol for unpremedicated dogs and cats were respectively 6.55 mg/kg and 8.03 mg/kg. The mean induction doses after premedication with a tranquilliser were 4.5 mg/kg and 5.97 mg/kg for dogs and cats, respectively. Mean recovery times ranged, depending on the method of anaesthesia, from 23 to 40 minutes in dogs and from 27 to 38 minutes in cats; recovery was defined as the time at which the animals were alert and able to stand. Adverse side effects were infrequent, apnoea during induction being the commonest. Acepromazine and atropine were most often used as premedicants although in a few cases diazepam, xylazine and other agents were employed. No clinical incompatibility was observed between propofol and any of the other agents administered during the study. The rapid and usually excitement-free recovery of the animals was a valuable feature of anaesthesia with propofol.

Use of Emetics and Anesthesia for Dietary Assessment of Weddell Seals

One female and 19 male Weddell seals, Leptonychotes weddellii, were injected with the emetic apomorphine hydrochloride. Fourteen of these were immobilised with combinations of ketamine hydrochloride and diazepam before the emetic was injected. One seal was administered the emetic tincture of ipecac while immobilised. The mean induction dose of ketamine hydrochloride was 7.99 � 1.99 mg kg-1 (mean�SD) and that of diazepam was 0.05 � 0.01 mg kg-1. The mean induction time was 23.07 � 17.63 min and the mean duration of immobilisation was 127.00 � 20.72 min. Six of the 22 seals apomorphine hydrochloride vomited and the seal given tincture of ipecac did not vomit. The mean dose of apomorphine hydrochloride that produced vomiting in immobilised animals was 0.18 � 0.10 mg kg-1 and the mean dose of apomorphine hydrochloride that produced vomiting in non-immobilised animals was 0.22 � 0.15 mg kg-1. Three seals died after drug administration during the study. Post-mortem examinations were conducted on these animals and nothing abnormal was found. Seals were weighed on 15 occasions (weight range, 137-402 kg) and the relationship between standard length (L, in centimetres) and body weight (W, in kilograms) was found to be: W=3.66L- 489.30. Food comprising five species of fish, two cephalopods and one gastropod were identified. Nematodes and gastroliths were present in most vomit samples. Centrally acting emetics and dissociative anaesthesia were both found to have limitations for use in Weddell seals.

Prolonged and multiple immobilizations of the southern elephant seal using ketamine hydrochloride-xylazine hydrochloride or ketamine hydrochloride-diazepam combinations.

Thirty seven southern elephant seals (Mirounga leonina) were singularly or repeatedly immobilized with combinations of ketamine hydrochloride (HCl) and xylazine HCl or ketamine HCl and diazepam. Atropine sulphate was included in the drug combinations. To permit experimental procedures the seals were immobilized for periods of 30-330 min. The mean induction dose of ketamine HCl was 8.71 +/- 0.25 mg/kg (mean +/- SE). The mean induction time was 16.02 +/- 2.62 min. For the elephant seals immobilized for periods in excess of 180 min, the mean dose of ketamine HCl used per hr was 3.31 +/- 0.13 mg/kg/hr and the mean dose of ketamine HCl used per hr postinduction was 1.31 +/- 0.15 mg/kg/hr. The mean dose of diazepam used was 0.09 +/- 0.01 mg/kg and the mean dose of xylazine HCl was 0.41 +/- 0.01 mg/kg. Elephant seals were weighed on 20 occasions (weight range: 897-1,932 kg) and the relationship between standard length and weight was found to be: Weight = 9.98 length - 2,317.63 (r2 = 0.724). Adverse reactions to seals immobilized only once or twice were not observed. Two seals immobilized on three occasions developed abscesses at the site of injection.

Propofol as an intravenous anaesthetic agent in dogs.

Studies in dogs with an emulsion formulation of the intravenous anaesthetic, propofol, showed that induction of anaesthesia was smooth and it was possible to maintain anaesthesia by intermittent injection. The mean dose for induction of anaesthesia in unpremedicated dogs was 5.95 mg/kg body-weight. When no premedication was administered anaesthesia was maintained by a total dose of approximately 0.806 mg/kg/minute. Premedication with between 0.02 and 0.04 mg/kg of acepromazine reduced the mean induction dose by about 30 per cent and the maintenance dose by more than 50 per cent. In 68 unpremedicated dogs given one dose, recovery was complete in a mean time of 18 minutes and after maintenance of anaesthesia by intermittent injection in 65 dogs the mean recovery time was 22 minutes from administration of the last dose. Premedication with acepromazine did not produce statistically significant increases in these recovery times. The quiet, rapid and complete recovery proved to be most valuable in cases where the animal had to be returned to the owners' care with the minimum of delay.

AN ASSESSMENT OF ALTHESIN FOR THE INDUCTION OF ANAESTHESIA IN CARDIAC SURGICAL PATIENTS: A COMPARISON WITH THIOPENTONE

In 42 patients about to undergo cardiac surgery, anaesthesia was induced with either Althesin or thiopentone. Arterial pressure, central venous pressure, pulse rate and the electrocardiogram were monitored in all patients. Cardiac output was measured in 16 patients. Althesin produced a smooth induction of anaesthesia and was indistinguishable clinically from thiopentone in this respect. The cardiovascular effects of the two drugs were similar, a reduction of both arterial pressure and cardiac output being noted, associated with decreases in stroke volume. The heart rate and calculated systemic vascular resistance were unchanged. Laryngoscopy and endotracheal intubation caused an increase in both heart rate and arterial pressure. The mean induction dose of Althesin was 27.7 μ1/kg, compared with 2.5 mg/kg of thiopentone.