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Biomedical subjects

T J Gan

Publications and source records attributed to T J Gan.

At least 37 records · Page 2Linked to original sources
PubMed1999

Women emerge from general anesthesia with propofol/alfentanil/nitrous oxide faster than men.

BACKGROUND: Recovery from general anesthesia is governed by pharmacodynamic and pharmacokinetic factors. Gender has not previously been recognized as a factor influencing the time to emergence from general anesthesia. METHODS: This multicenter study was originally designed to measure the effects of the bispectral index on intraoperative anesthetic management and patient recovery. We compared the wake-up and recovery times of 274 adults after propofol/alfentanil/nitrous oxide anesthesia. Patients were randomly assigned to have the titration of propofol performed with or without the use of bispectral index monitoring. Specific guidelines were given for the titration of drugs. The aim in all cases was to provide a safe anesthetic with the fastest possible recovery. RESULTS: There was a significant reduction in propofol dose, time to eye opening, and response to verbal command when the anesthetic was titrated using the bispectral index. Unexpectedly, gender proved to be a highly significant independent predictor for recovery time. Women woke significantly faster than men: the time from end of anesthesia to eye opening was 7.05 versus 11.22 min, P < 0.05, and response to verbal command was 8.12 versus 11.67 min, P < 0.05. These differences were significant at all four study sites and in each treatment group. Men consistently had prolonged recovery times compared to women, P < 0.001. There was no difference in the dose of anesthetic used between gender. CONCLUSIONS: Gender appears to be an important variable in recovery from general anesthesia. These findings may explain the increased reported incidence of awareness in women (three times more frequent) and support the need to include gender as a variable in pharmacokinetic and pharmacodynamic studies of anesthetic drugs.

Adolescent↗
PubMed1999

Patient-controlled antiemesis: a randomized, double-blind comparison of two doses of propofol versus placebo.

BACKGROUND: The role of propofol for the management of postoperative nausea and vomiting (PONV) is not well established. This study determines the efficacy of small doses of propofol administered by patient-controlled device for the treatment of PONV. METHODS: Patients presenting for ambulatory surgery received a standardized general anesthetic. Those who experienced significant nausea or emesis within 1 h of arrival in the recovery room were randomized to receive repeated doses of propofol 20 mg (P-20), propofol 40 mg (P-40), or intralipid (placebo) on demand. Study medications (in equal volumes) were administered with a patient-controlled delivery device for 2 h. A lockout interval of 5 min between doses was used. The following parameters were assessed: nausea, vomiting, rescue antiemetic use, recovery profile, study drug administration history, and satisfaction with treatment. RESULTS: Sixty-nine patients participated in the study. Patient demographics were similar. The average nausea score for a patient in the P-20 and P-40 groups was 25% and 29% less, respectively, compared with placebo during the study period (P < 0.05). This difference was apparent 15 min after initiation of therapy. More placebo patients vomited (P-20, 12%; P-40, 23%; placebo, 56%; P = 0.003) and needed rescue antiemetics (P-20, 17%; P-40, 23%; placebo, 70%; P = 0.001) compared with treatment groups. Sedation scores were similar between groups. Propofol-treated patients had shorter stays in the post-anesthesia care unit (PACU; P-20, 131+/-35 min [mean +/- SD]; P-40, 141+/-34 min; placebo, 191+/-92 min; P = 0.005) and higher satisfaction with their control of PONV than placebo (P < 0.01). CONCLUSIONS: Propofol is effective in managing PONV with shorter PACU stay and great degree of patient satisfaction. There were two episodes of oversedation in the P-40 group. Hence, propofol at a demand dose of 20 mg seems more appropriate.

Adult↗
PubMed1999

Comparison of the intubation conditions provided by rapacuronium (ORG 9487) or succinylcholine in humans during anesthesia with fentanyl and propofol.

BACKGROUND: Currently, the only approved muscle relaxant with a rapid onset and short duration of action is succinylcholine, a drug with some undesirable effects. Rapacuronium is an investigational nondepolarizing relaxant that also has a rapid onset and short duration and consequently should be compared with succinylcholine in its ability to facilitate rapid tracheal intubation. METHODS: This prospective, randomized clinical trial involved 336 patients. Anesthesia was induced with fentanyl and propofol and either 1.5 mg/kg rapacuronium or 1.0 mg/kg succinylcholine. The goal was to accomplish tracheal intubation by 60 s after administration of the neuromuscular blocking drug. Endotracheal intubation was performed, and conditions were graded by a blinded investigator. Recovery of neuromuscular function was assessed by electromyography. RESULTS: Intubation conditions were evaluated in 236 patients. Intubation by 60 s after drug administration occurred in 100% of patients with rapacuronium and in 98% with succinylcholine. Intubation conditions were excellent or good in 87% of patients with rapacuronium and in 95% with succinylcholine (P < 0.05). The time (median and range) to the first recovery of the train-of-four response was 8.0 (2.8-20.0) min with rapacuronium and 5.7 (1.8-17.7) min with succinylcholine (P < 0.05). The overall incidence of adverse effects was similar with both drugs. CONCLUSIONS: A 1.5-mg/kg dose of rapacuronium effectively facilitates rapid tracheal intubation. It can be considered a valid alternative to 1.0 mg/kg succinylcholine for this purpose.

Adolescent↗
PubMed1998

Venovenous bypass in adult orthotopic liver transplantation: routine or selective use?

BACKGROUND: The role of venovenous bypass (VVB) during orthotopic liver transplantation (OLT) remains controversial. The aims of this study were to evaluate the current role of VVB at all major centers in North America, to examine the results of OLT and complications of VVB between two periods with a strict policy for routine versus selective use of VVB, and to review the literature. STUDY DESIGN: A survey of 50 major liver transplant centers was conducted using mailed questionnaires. A retrospective chart review was performed for 547 OLT patients having transplantation during two distinct periods with a strict policy for routine versus selective use of VVB at the University of Toronto, Canada, and at Duke University Medical Center, Durham, North Carolina. The literature was reviewed with a focus on the benefits and indications for routine versus selective use of VVB. RESULTS: Thirty-eight (76%) of 50 centers responded. Sixteen (42%) of them used VVB routinely, with a reported complication rate of 10-30%. Lymphocele and hematoma were the most common complications, but patients having major vascular injury, air embolism, and death were reported. A recent change to selective use of VVB was reported in 30% of the centers (11 of 38). In the Duke-Toronto series, the complication rates were similar between the two periods, at 13.4% and 18.8%, respectively. The outcome of OLT was not influenced by the policy of routine or selective use of VVB. CONCLUSIONS: There is a trend away from the routine use of VVB during OLT. Intraoperative hemodynamic instability during the hepatectomy and a failed trial of hepatic venous occlusion were the most important criteria for using VVB. We conclude that VVB should be used selectively to avoid associated complications and to decrease operative time and costs.

Adult↗
PubMed1998

A comparison of the efficacy, safety, and patient satisfaction of ondansetron versus droperidol as antiemetics for elective outpatient surgical procedures. S3A-409 and S3A-410 Study Groups.

UNLABELLED: Two identical, randomized, double-blind, placebo-controlled studies enrolled 2061 adult surgical outpatients at high risk of postoperative nausea and vomiting (PONV) to compare i.v. ondansetron 4 mg with droperidol 0.625 mg and droperidol 1.25 mg for the prevention of PONV. The antiemetic drugs or placebo were administered i.v. 20 min before the induction of anesthesia with a barbiturate compound, followed by maintenance with N2O/isoflurane/enflurane. Nausea, emetic episodes, adverse events, and patient satisfaction were analyzed for the 0 to 2 h and 0 to 24 h postoperative periods. In the 0 to 2 h postoperative period, there was a complete response (no emesis or rescue antiemetic) in 46% of subjects given placebo (P < 0.05 versus antiemetic groups), in 62% given ondansetron, in 63% given droperidol 0.625 mg, and in 69% given droperidol 1.25 mg (P < 0.05 versus ondansetron). In the 0 to 24-h postoperative period, there were no significant differences in complete response between the ondansetron and droperidol 0.625 or 1.25 mg groups; all groups remained superior to placebo. The proportion of patients without nausea during the 0 to 24 h postoperative period was greater in the antiemetic groups compared with the placebo group; however, droperidol 1.25 mg was more effective than ondansetron 4 mg or droperidol 0.625 mg (43% vs 29% or 29%, respectively). Headache incidence was higher in the ondansetron group compared with either droperidol group. Patient satisfaction scores did not differ significantly among antiemetic treatment groups, although all were superior to placebo. In conclusion, all antiemetic treatment regimens were superior to placebo for the prevention of PONV in the immediate postoperative period; however, droperidol 1.25 mg was more efficacious than ondansetron during the early recovery period (0-2 h). There were no significant differences between ondansetron and either droperidol dose for emesis prevention during the 0 to 24 h postoperative period. IMPLICATIONS: More than 2000 patients at high risk of postoperative nausea and vomiting were given either placebo, ondansetron 4 mg, or droperidol 0.625 mg or 1.25 mg i.v. before the administration of general anesthesia. After surgery, the incidence of nausea, vomiting, medication side effects, and patient satisfaction were evaluated for 24 h. Droperidol 0.625 or 1.25 mg i.v. compared favorably with ondansetron 4 mg i.v. for the prevention of postoperative nausea and vomiting after ambulatory surgery.

Adolescent↗
PubMed1998

The effect of the interaction of propofol and alfentanil on recall, loss of consciousness, and the Bispectral Index.

UNLABELLED: The Bispectral Index (BIS) correlates well with the level of consciousness with single anesthetic drugs. We studied the effect of the interaction of propofol with alfentanil on propofol concentration and BIS associated with 50% probability of loss of consciousness and lack of recall (Cp50 and BIS50, respectively). We studied 40 consenting volunteers at two institutions who were randomly assigned to receive stepped increases of propofol (10 subjects at each site), propofol plus alfentanil 50 ng/mL (10 subjects at Emory site), or propofol plus alfentanil 100 ng/mL (10 subjects at Duke site) by using a target-controlled infusion device. Measures of sedation, BIS, deltaBIS (absolute change of BIS after a painful stimulus), memory, and drug concentration were obtained at each target drug concentration. The relation among BIS, measured drug concentration, sedation score, and presence or absence of recall was determined by linear and logistic regression for different drug regimens, and the prediction probability (Pk) was calculated. The addition of alfentanil in increasing doses did not significantly affect the BIS50 and propofol Cp50 values for loss of consciousness and lack of recall. DeltaBIS was significantly decreased by both an increase in the concentration of propofol and the presence of alfentanil. The Pk for BIS was >0.93 with all drug regimens, better than those of the target and measured propofol concentrations. We conclude that BIS correlated well with the hypnotic component of anesthesia independent of the presence of an opioid. Moreover, the level of consciousness, and, therefore, the BIS index, is affected by a painful stimulus, and this response is ablated either by opioids or increasing propofol concentration. IMPLICATIONS: In volunteers, the sedation and changes in memory function produced by propofol correlated well with changes in the Bispectral Index. This relationship was not altered by the addition of an analgesic (alfentanil). However, in moderately sedated patients who received a painful stimulus, the Bispectral Index increased, but this response was blocked by the analgesic or increasing propofol concentrations.

Adult↗
PubMed1997

Drug interactions: volatile anesthetics and opioids.

Multiple drugs are used to provide anesthesia. Volatile anesthetics are commonly combined with opioids. Several studies have demonstrated that small doses of opioid (i.e., within the analgesic range) result in a marked reduction in minimum alveolar concentration (MAC) of the volatile anesthetic that will prevent purposeful movement in 50% of patients at skin incision). Further increases in opioid dose provide only a further small reduction in MAC. Thus, a ceiling effect of the opioid is observed at a MAC value of the volatile anesthetic equal to its MAC awake. Recovery from anesthesia when an opioid is combined with a volatile anesthetic is dependent on the rate of decrease of both drugs to their respective concentrations that are associated with adequate spontaneous ventilation and awakening. Through an understanding of the pharmacodynamic interaction of volatile anesthetics with opioids and the pharmacokinetic processes responsible for the recovery from drug effect, optimal dosing schemes can thus be developed. A review of these pharmacodynamic and pharmacokinetic principles that will allow clinicians to administer drugs to provide a more optimal anesthetic is provided.

Alfentanil↗
PubMed1997

The successful implementation of pharmaceutical practice guidelines. Analysis of associated outcomes and cost savings. SWiPE Group. Systematic Withdrawal of Perioperative Expenses.

BACKGROUND: Although approximately 2,000 medical practice guidelines have been proposed, few have been successfully implemented and sustained. We hypothesized that we could develop and institute practice guidelines to promote more appropriate use of costly anesthetics, to generate and sustain widespread compliance from a large physician group, and to decrease costs without adversely affecting clinical outcomes. METHODS: A prospective before and after comparison study was performed at a tertiary care medical center. Clinical outcomes data and times indicative of perioperative patient flow were collected on the first of two sets of patients 1 month before discussion of practice guidelines. Practice guidelines were developed by the physicians and their associated care team for the intraoperative use of anesthetic drugs. A drug distribution process was developed to aid compliance. Clinical outcomes data and times indicative of perioperative patient flow were collected on the second set of patients 1 month after institution of practice guidelines. Hospital drug costs and adherence to guidelines were noted throughout the study period and for each of the following 9 months by querying the database of an automated anesthesia record keeper. RESULTS: A total of 1,744 patients were studied. Drug costs decreased from 56 dollars per case to 32 dollars per case as a result of adherence to practice guidelines. Perioperative patient flow was minimally affected. Time (mean +/- SD) from end of surgery to arrival in the post-anesthesia care unit (PACU) increased from 11 +/- 7 min before the authors instituted practice guidelines to 14 +/- 8 min after practice guidelines (P < 0.0001). Admission of inpatients to the PACU receiving monitored anesthesia care increased from 6.5 to 12.9% (P < 0.02). Perioperative patient flow and clinical outcomes were not otherwise adversely affected. Compliance and cost savings have been sustained. CONCLUSIONS: This study is an example of a successful physician-directed program to promote more appropriate utilization of health care resources. Cost savings were obtained without any substantial changes in clinical outcomes. Institution of similar practice guidelines should result in pharmaceutical savings in the range of 50% at tertiary care centers around the country, with a slightly smaller degree of savings expected at institutions with more ambulatory surgery.

Anesthesiology↗
PubMed1997

Determination of plasma concentrations of propofol associated with 50% reduction in postoperative nausea.

BACKGROUND: Subhypnotic doses of propofol possess direct antiemetic properties. The authors sought to determine the plasma concentration of propofol needed to effectively manage postoperative nausea and vomiting. METHODS: Patients aged 18-70 yr who were classified as American Society of Anesthesiologists physical status 1 or 2 and had surgery during general anesthesia were approached for the study. Only patients who had nausea (verbal rating score > 5 on a 0- to 10-point scale), retching, or vomiting in the postanesthetic care unit participated. Propofol was administered to these patients to achieve target plasma concentrations of 100, 200, 400, and 800 ng/ml using a computer-assisted continuous infusion device. Target concentrations were increased every 15 min until patients described at least a 50% reduction in symptoms on the verbal rating score. An arterial blood sample was obtained at each step. The measured plasma propofol concentrations were used to analyze data. Blood pressure, heart and respiratory rates, arterial blood saturation, sedation score, and overall satisfaction with treatment were recorded. RESULTS: Of the 89 patients who consented to the study, 15 patients met entry criteria and were enrolled. Five of these patients also had retching or vomiting when they entered the study. Fourteen patients responded successfully to treatment. One patient did not achieve the required response at plasma concentrations of 830 ng/ml. Hence the success rate for the treatment of postoperative nausea and vomiting was 93%. Among patients who responded, the median plasma concentration associated with an antiemetic response was 343 ng/ml. There was no difference in sedation scores from baseline and no episodes of desaturation. Hemodynamic parameters were stable during the study. CONCLUSIONS: Propofol is generally efficacious in treating postoperative nausea and vomiting at plasma concentrations that do not produce increased sedation. Simulations indicate that to achieve antiemetic plasma propofol concentrations of 343 ng/ml, a bolus dose of 10 mg followed by an infusion of approximately 10 microg x kg(-1) x min(-1) are necessary.

Adolescent↗
PubMed1997

Bispectral index monitoring allows faster emergence and improved recovery from propofol, alfentanil, and nitrous oxide anesthesia. BIS Utility Study Group.

BACKGROUND: The bispectral index (BIS), a parameter derived from the electroencephalograph (EEG), has been shown to correlate with increasing sedation and loss of consciousness. This study determined whether addition of BIS monitoring to standard anesthetic practice results in improvements in the conduct of anesthesia or in patient outcomes. METHODS: Three hundred two patients receiving a propofol-alfentanil-nitrous oxide anesthetic were studied at four institutions. Thirty-four patients were initially enrolled to determine preexisting anesthetic practice and patient outcomes at each institution. Subsequent patients were randomized to either standard clinical practice (SP group), or standard practice plus BIS monitoring (BIS group). In all patients, the anesthesiologist attempted to provide a stable anesthetic with the fastest possible recovery. BIS was recorded for all patients, but viewed only in the BIS group. In the BIS group, propofol infusions were adjusted to achieve a target BIS between 45-60, increasing to 60-75 during the final 15 min of the case. In the SP group, propofol dose adjustments were made based only on standard clinical signs. Drug use, intraoperative responses, and patient recovery parameters were recorded. RESULTS: Demographics were similar between groups. Compared with the SP group, patients in the BIS group required lower normalized propofol infusion rates (134 vs. 116 microg x kg[-1] x min[-1]; P < 0.001), were extubated sooner (11.22 vs. 7.25 min; P < 0.003), had a higher percentage of patients oriented on arrival to PACU (43% vs. 23%; P < 0.02), had better postanesthesia care unit (PACU) nursing assessments (P < 0.001), and became eligible for discharge sooner (37.77 vs. 31.70 min; P <0.04). There was no significant difference in the incidence of intraoperative responses between the groups. CONCLUSIONS: Titrating propofol with BIS monitoring during balanced anesthesia decreased propofol use and significantly improved recovery. Intraoperative course was not changed. These findings indicate that the use of BIS may be valuable in guiding the administration of propofol intraoperatively.

Adolescent↗
PubMed1997

Opioid-sparing effects of a low-dose infusion of naloxone in patient-administered morphine sulfate.

BACKGROUND: A naloxone infusion is effective in reducing epidural and intrathecal opioid-related side effects. The use of naloxone infusion concomitant with intravenous morphine patient-controlled analgesia (PCA) has not been evaluated, probably because of an expected direct antagonism of the systemic opioid effect. The authors compared the incidence of morphine-related side effects and the quality of analgesia from two small doses of naloxone infusion. METHODS: Sixty patients classified as American Society of Anesthesiologists physical status 1, 2, or 3 who were scheduled for total abdominal hysterectomies were enrolled in the study. Patients received a standardized general anesthetic. In the postanesthetic care unit, patients received morphine as a PCA. They were randomized to receive either 0.25 microg x kg(-1) x h(-1) naloxone (low dose), 1 microg x kg(-1) x h(-1) (high dose), or saline (placebo) as a continuous infusion. Verbal rating scores for pain, nausea, vomiting, and pruritus; sedation scores; requests for antiemetic; and morphine use were recorded for 24 h. Blood pressure, respiratory rate, and oxyhemoglobin saturation were also monitored. RESULTS: Sixty patients completed the study. Both naloxone doses were equally effective in reducing the incidence of nausea, vomiting, and pruritus compared with placebo (P < 0.05 by the chi-squared test). There was no difference in the verbal rating scores for pain between the groups. The cumulative morphine use was the lowest in the low-dose group (42.3 +/- 24.1 mg; means +/- SD) compared with the placebo (59.1 +/- 27.4 mg) and high-dose groups (64.7 +/- 33.0 mg) at 24 h (P < 0.05 by analysis of variance). There was no incidence of respiratory depression (<8 breaths/min) and no difference in sedation scores, antiemetic use, respiratory rate, and hemodynamic parameters among the groups. CONCLUSIONS: Naloxone is effective in preventing PCA opioid-related side effects. Naloxone infusion at 0.25 microg x kg(-1) x h(-1) not only attenuates these side effects but appears to reduce postoperative (beyond 4-8 h) opioid requirements. This dosing regimen can be prepared with 400 microg naloxone in 1,000 ml crystalloid given in 24 h to a patient weighing 70 kg.

Adult↗
PubMed1997

How to manage drug interactions.

Multiple drugs are used to provide anaesthesia. On average, four to six drugs are used during anaesthesia and, therefore, drug interactions are common. These interactions are primarily either pharmacokinetic or pharmacodynamic. Due to the relatively short duration of drug administration for anaesthesia, pharmacokinetic drug interactions resulting from alterations in drug metabolism do not generally produce clinically significant effects. Pharmacodynamic-drug interactions between anaesthetic drugs, however, are potentially serious. This may reflect that anaesthesia is not a single entity, but a process provided by a combination of drugs; i.e. loss of consciousness, analgesia and neuromuscular blockade. An understanding of each drug's pharmacokinetics, pharmacodynamics and drug interactions will allow clinicians to administer drugs to provide a more optimal anaesthetic.

Anesthesia↗