The nonhypnotic therapeutic applications of propofol

Target-controlled propofol vs. sevoflurane: a double-blind, randomised comparison in day-case anaesthesia

We compared target-controlled propofol with sevoflurane in a randomised, double-blind study in 61 day-case patients. Anaesthesia was induced with a propofol target of 8 microgram.ml-1 or 8% sevoflurane, reduced to 4 microgram.ml-1 and 3%, respectively, after laryngeal mask insertion and subsequently titrated to clinical signs. Mean (SD) times to unconsciousness and laryngeal mask insertion were significantly shorter with propofol [50 (9) s and 116 (33) s, respectively] than with sevoflurane [73 (14) s and 146 (29) s; p < 0.0001 and p = 0.0003, respectively]; however, these differences were not apparent to the blinded observer. Propofol was associated with a higher incidence of intra-operative movement (55 vs. 10%; p = 0.0003), necessitating more adjustments to the delivered anaesthetic. Emergence was faster after sevoflurane [5.3 (2.2) min vs. 7.1 (3.7) min; p = 0.027], but the inhaled anaesthetic was associated with more nausea and vomiting (30 vs. 3%; p = 0.006), which delayed discharge [258 (102) min vs. 193 (68) min; p = 0.005]. Direct costs were lower with sevoflurane but nausea would have increased indirect costs. Patient satisfaction was high (>/= 90%) with both techniques. In conclusion, both techniques had advantages and disadvantages for day-case anaesthesia.

The short-acting anesthetic propofol produces biphasic effects-depression and withdrawal rebound overshoot-on some (but not all) limbic evoked potentials in the behaving rat

Propofol, the relatively new, short-acting general anesthetic, markedly enhances the action of GABA at the GABAA receptor. To evaluate its effects on field potentials evoked in the dentate gyrus (DG) during the anesthetic and recovery periods, propofol was administered intraperitoneally to behaving rats bearing stimulating electrodes in the dorsal perforant path (DPP), where medial perforant path fibers predominate, and in the anterior piriform cortex (PC; i.e., olfactory cortex), and recording electrodes in the DG. Input from the PC reaches the DG via the lateral perforant path. Population slow waves (SWs) were evoked by paired-pulse stimulation of the PC at a 32 ms interstimulus interval (ISI) to produce paired-pulse facilitation in the awake animal. We had previously demonstrated that amplitude of SW2 (produced by the second stimulus) was greatly decreased by GABAergic drugs and increased by antiGABAergic convulsant agents. After administration of propofol, mean amplitude of SW2 decreased immediately and remained low for 30-60 min during propofol-induced sleep (as expected), then unexpectedly increased to about 1.5- to 2-fold above pretreatment levels at 2-4 h before gradually returning to pretreatment levels. In addition, the DPP was stimulated to produce either paired-pulse inhibition (20 ms ISI) or facilitation (32 ms ISI) of DG population spikes (PSs) in the awake animal. PS2 was much more inhibited during propofol-induced sleep, than during the pretreatment period, consistent with an expected marked increase in recurrent inhibition. An overshoot in PS2 amplitude was observed only occasionally during recovery, suggesting that withdrawal overshoot in amplitudes is more characteristic of PC-evoked DG SW2 potentials. The overshoot in SW2 amplitude during recovery may have been related to propofol's 'rapid on-rapid off' actions on the GABAA receptor, perhaps resulting in a phenomenon like the 'GABA withdrawal syndrome'. Such an effect, if true, may help explain the rare occurrence of seizures, especially during recovery, associated with its use clinically.

Gastrointestinal motility and gastric tube feeding in mechanically ventilated patients

OBJECTIVE

To determine the fasted and fed gastrointestinal motility characteristics that are possibly responsible for gastric retention in mechanically ventilated patients.

DESIGN

Prospective, case series.

SETTING

Surgical intensive care unit of a university hospital.

PATIENTS

Seven patients who required mechanical ventilation for thoracic or combined thoracic-neurologic injuries and nine healthy volunteers.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Antroduodenal manometry was performed during fasting and gastric feeding with a polymeric diet in patients during mechanical ventilation, weaning, and after detubation. Gastric retention volumes were determined during gastric tube feeding. Motility data were compared with recordings from nine healthy volunteers. During the fasting state, under sedation and morphine, the migrating motor complex in patients was significantly (p < .001) shortened: median 32.0 vs. 101.0 mins in healthy volunteers. During gastric tube feeding, the motility pattern did not convert to a normal postprandial pattern until morphine was discontinued. An interdigestive or mixed interdigestive-postprandial pattern was seen during gastric tube feeding in most patients during morphine administration. Most (94%) of the activity fronts during gastric feeding started in the duodenum. Gastric retention percentages during gastric tube feeding were negatively correlated (r2=.44; p < .01) with antral motor activity.

CONCLUSIONS

These data suggest that morphine administration affects antroduodenal motility in mechanically ventilated patients. The gastrointestinal motor pattern involved in impaired gastric emptying in morphine-treated patients is characterized by antral hypomotility and persisting duodenal activity fronts during continuous intragastric feeding. The observed motility patterns suggest that early administration of enteral feeding might be more effective into the duodenum or jejunum than into the stomach of mechanically ventilated patients.

Intravenous fluid and postoperative nausea and vomiting after day-case termination of pregnancy

BACKGROUND

Deprivation of oral fluid before minor surgery has been alleged to cause postoperative nausea. We examined the effect of intraoperative fluid load on postoperative nausea and vomiting over 3 d after day-case termination of pregnancy.

METHODS

In a randomized study, 100 patients were allocated into one of two groups; receiving 1000 ml of compound sodium lactate solution during surgery or no intraoperative fluid. Propofol and alfentanil was used to induce and maintain anaesthesia with nitrous oxide (67%) and oxygen (33%). Visual analogue scores for nausea and pain, the time and frequency of emetic episodes, analgesic and antiemetic consumption were recorded for 3 d postoperatively.

RESULTS

The scores of nausea were significantly lower in the fluid group (P < 0.05) compared with the control group at 1, 2, 4 h and during 24-48 h following surgery. The incidence of emesis was lower (P < 0.01) after discharge, and the time to first oral fluid was shorter (P < 0.05) in the fluid group. There was no difference in pain score or analgesic consumption between the groups. Five patients (10%) in the control group requested antiemetic medication compared with none in the fluid group.

CONCLUSION

Intraoperative fluid administration may offer some benefit in decreasing the incidence of postoperative nausea and vomiting following day-case surgery.

Treatment of refractory status epilepticus with propofol: clinical and pharmacokinetic findings

PURPOSE

We compared propofol with high-dose barbiturates in the treatment of refractory status epilepticus (RSE) and propose a protocol for the administration of propofol in RSE in adults, correlating propofol's effect with plasma levels.

METHODS

Sixteen patients with RSE were included; 8 were treated primarily with high-dose barbiturates and 8 were treated primarily with propofol.

RESULTS

Both groups of patients had multiple medical problems and a subsequent high mortality. A smaller but not statistically significant fraction of patients had their seizures controlled with propofol (63%) than with high-dose barbiturate therapy (82%). The time from initiation of high-dose barbiturate therapy to attainment of control of RSE was longer (123 min) than the time to attainment of seizure control in the group receiving propofol (2.6 min, p = 0.002). Plasma concentrations of propofol associated with control of SE were 14 microM +/- 4 (2.5 microg/ml). Recurrent seizures were common when propofol infusions were suddenly discontinued but not when the infusions were gradually tapered.

CONCLUSIONS

If used appropriately, propofol infusions can effectively and quickly terminate many but not all episodes of RSE. Propofol is a promising agent for use in treating RSE, but more studies are required to determine its true value in comparison with other agents.

Successful use of propofol in refractory delirium tremens

Alcohol withdrawal is a common problem encountered by emergency physicians, with delirium tremens (DT) as the extreme manifestation. DT is a true medical emergency. Although benzodiazepines are the mainstay of therapy, some patients require massive amounts to control their symptoms. We report the successful use of propofol for DT refractory to benzodiazepines in a 42-year-old alcoholic man. We briefly discuss alcohol withdrawal, as well as the pharmacokinetics and adverse affects of propofol. The use of propofol in treating DT refractory to benzodiazepines has previously not been reported.

Anaesthetic considerations for children undergoing stereotactic radiosurgery

An anaesthetic case report of children undergoing stereotactic radiosurgery is presented, with a review of the inherent unique anaesthetic challenges. Twelve stereotactic radiosurgery procedures performed at The Prince of Wales Hospital, Sydney, were retrospectively reviewed. Despite differences in approach by individual anaesthetists to managing these children, an overall safe sequence may be evolved. The use of stereotactic radiosurgery for paediatric neuropathology is reviewed. The potential anaesthetic problems related to the paediatric patient and the peculiarities of the procedure are discussed and related to our series.

Propofol for sedation in the intensive care unit: essentials for the clinician

Propofol is a short-acting intravenous anesthetic commonly utilised in the intensive care unit (ICU) for sedation of mechanically ventilated patients. The rapid onset and termination of action make it an attractive drug for use in the ICU. The safety profile of propofol is well established. However, there are potential adverse reactions associated with the drug. This review discusses the pharmacology, administration and adverse effects associated with propofol with which clinicians who administer propofol should be familiar.

Anesthetic management of patients receiving calculus therapy with a third-generation extracorporeal lithotripsy machine

We reviewed the anesthetic requirements for satisfactory use of a third-generation electromagnetic-source design for extracorporeal shockwave lithotripsy (SWL). Medical records were reviewed for a period of 9 months on all patients receiving anesthesia care for SWL with and without other urologic procedures. The Modulith SL20 was used on 56 ASA Class I-III patients having 87 SWL treatments. Demographic and anesthetic variables were recorded. Complications documented included dysrhythmias, nausea necessitating treatment, and conversion from sedation to regional or general anesthesia. The majority of procedures (83%) were performed on an outpatient basis. Patients were classified as ASA physical status I (27%), II (63%), or III (10%). Monitored anesthesia care with intravenous sedation was utilized in 93% of cases. Of these cases, 78 involved a combination of intravenous propofol, fentanyl, and midazolam; the remaining 3 involved propofol, alfentanil, and/or midazolam. The mean treatment duration was 36 minutes. Patients were discharged within 1 hour after procedure completion in 77 cases (89%). Nausea necessitating treatment was rare (3%). The mean dose of propofol administered with SWL as the only procedure was 272 +/- 112 mg. When SWL was combined with other urologic procedures, the mean dose of propofol was 334 +/- 121 mg. Continuous intravenous propofol infusion provides excellent procedural conditions for SWL on the Modulith SL120, a third-generation lithotripter.

Propofol produces anticonflict action by inhibiting 5-HT release in rat dorsal hippocampus

We examined the effect of propofol, an injectable anesthetic agent on conflict behavior in a Vogel type conflict test and on release of serotonin (5-hydroxytryptamine, 5-HT) in the dorsal hippocampus using an in vivo microdialysis method in rats. Propofol (20 and 40 mg/kg, i.p.) dose-dependently suppressed elevated 5-HT release normally seen in a conflict situation and concomitantly attenuated conflict behavior. These findings suggest that propofol exerts an antianxiety action by inhibiting 5-HT neuronal activity in the dorsal hippocampus.

Acute tachyphylaxis to propofol sedation during ethanol withdrawal

We treated a patient with a 30-year history of ethanol and benzodiazepine abuse who, on emerging from general anesthesia, was combative and confused. Our working diagnosis was acute ethanol withdrawal, and the patient received intravenous (i.v.) propofol, and midazolam. Initially small doses (10 to 20 mg) of propofol, combined with a midazolam infusion (50 mg/hr), produced sedation. Later, however, the patient became increasingly combative, confused, hypertensive, and tachycardic despite an i.v. propofol infusion at doses up to 1,000 micrograms/kg/min (total propofol dose: 1,755 mg). Immediate sedation was produced by thiopental bolus (500 mg) and i.v. infusion (200 mg/hr). The implication of the patient's initial appropriate response to propofol, followed by the lack of effect when much higher doses were employed, is discussed. While tachyphylaxis has been reported after long-term propofol use, we believe this to be the first case of acute tachyphylaxis.

Nausea and vomiting following thyroid and parathyroid surgery

STUDY OBJECTIVES

To determine the incidence of postoperative nausea and vomiting (PONV) following thyroid and parathyroid surgery. To determine whether PONV is reduced when propofol is used for maintenance of anesthesia as compared to isoflurane and to evaluate the costs and resource consumption associated with these two anesthetic regimens.

DESIGN

Randomized, prospective study.

SETTING

University-affiliated hospital--a referral center for endocrinologic surgery.

PATIENTS

118 ASA physical status I and II patients, aged 18 years and older, undergoing elective thyroid or parathyroid surgery.

INTERVENTIONS

Patients received either isoflurane (0.5 to 1.3% end-tidal) or propofol (50 to 200 micrograms/kg/min) for maintenance of anesthesia. All patients received propofol for induction of anesthesia, succinylcholine or vecuronium, nitrous oxide, and fentanyl. Prophylactic antiemetics were not administered. Postoperative pain was treated with ketorolac, fentanyl, or acetaminophen.

MEASUREMENTS AND MAIN RESULTS

Signs and symptoms of nausea and vomiting were graded on a four point scale as 1 = no nausea; 2 = mild nausea; 3 = severe nausea; 4 = retching and/or vomiting. Grades 3 and 4 were grouped together as PONV. The combined incidence of PONV was 54% over the 24-hour postoperative evaluation period. PONV was significantly more common in patients receiving isoflurane than propofol for maintenance of anesthesia (64% vs. 44%). In women (n = 87), the incidence of PONV was significantly greater in those patients who received isoflurane than those who received propofol for maintenance (71% vs. 42%). However, in men (n = 31), there was no significant difference in PONV between anesthetic regimens (47% with isoflurane vs. 50% with propofol). There were no differences in the duration of stay in the postanesthesia care unit, time to discharge from the hospital, or local wound complications (hematomas) between groups. The use of propofol for maintenance of anesthesia was associated with an additional cost, relative to the isoflurane group, of $54.26 per patient.

CONCLUSION

Patients undergoing thyroid or parathyroid surgery are at high risk for the development of PONV. Propofol for maintenance of anesthesia, although more expensive than isoflurane, reduces the rate of PONV in women.

Propofol decreases ocular pressure in outpatients undergoing trabeculectomy

STUDY OBJECTIVE

To examine the effect of a continuous low-dose intravenous (i.v.) infusion of propofol on ocular pressure in outpatients undergoing trabeculectomy.

DESIGN

Randomized, prospective study.

SETTING

Teaching hospital.

PATIENTS

40 unpremedicated outpatients with history of primary open angle glaucoma undergoing trabeculectomy.

INTERVENTIONS

In the operating room, an infusion of 5% dextrose into a peripheral vein was started. The propofol group (n = 20) received 0.5 mg/kg i.v. propofol bolus followed immediately by a continuous 0.5 mg/kg/hr infusion. The control group (n = 20) received only the dextrose solution. A peribulbar block was performed with bupivacaine with added adrenaline, plus lidocaine. The ocular pressure (tonometer) on the eye undergoing trabeculectomy and the other eye, blood pressure (BP), and heart rate (HR) were measured at the following times: (1) preoperatively; (2) 2 minutes; (3) 5 minutes; (4) 10 minutes; (5) 15 minutes after propofol bolus administration for the propofol group (approximately 4 minutes after the peribulbar blockade on the eye undergoing surgery for the propofol and control groups).

MEASUREMENTS AND MAIN RESULTS

Ocular pressure decreased 2 minutes after propofol infusion (p < 0.0001) and remained significantly lower than in the control group throughout the study period. All patients remained awake and cooperative during all procedures. Mean BP and HR were kept constant throughout the study.

CONCLUSION

Low-dose propofol sedation resulted in a decrease in ocular pressure, was quick in onset, and was unrelated to BP and HR. The decrease in ocular pressure may be due to relaxation of extraocular muscles by propofol.

Isoflurane and propofol block neurotoxicity caused by MK-801 in the rat posterior cingulate/retrosplenial cortex

In acute brain injury syndromes, the potent N-methyl-D-aspartate (NMDA) antagonist, MK-801, can prevent neuronal degeneration, and the general anesthetics, isoflurane and propofol, may also provide neuroprotective benefits. An obstacle to the use of NMDA antagonists for neuroprotective purposes is that they can cause a neurotoxic vacuole reaction in cerebrocortical neurons. This study demonstrates the ability of isoflurane and propofol to prevent the neurotoxic vacuole reaction induced by MK-801. Low sedative doses of inhaled isoflurane (1%) or intravenous (i.v.) propofol (7.5 mg/kg/h) were as effective as higher general anesthetic doses. Thus, in the clinical management of acute brain injury conditions such as stroke and brain trauma, administration of one of these anesthetic agents together with an NMDA antagonist may be an excellent formula for obtaining optimal neuroprotection while eliminating serious side effects.

Small-dose propofol by continuous infusion does not prevent postoperative vomiting in females undergoing outpatient laparoscopy

This study was designed to test the hypothesis that there is a direct prophylactic antiemetic effect of small-dose propofol given by continuous infusion. Sixty female patients undergoing outpatient laparoscopy under general anesthesia were randomized to receive, in a double-blind fashion, either a bolus of 0.1 mg/kg followed by a constant infusion of 1 mg.kg-1.h-1 of propofol or an equivalent volume of 10% Intralipid (placebo) beginning 30 min before induction of anesthesia and continuing until discharge from Stage I postanesthesia care unit (PACU). Anesthesia was induced and maintained in a standard fashion in all patients. The number of emetic episodes before and after discharge from PACU, nausea scores (11-point numerical scale), and time to discharge were evaluated. No significant differences between Intralipid and propofol were found for any of the outcome variables tested. While small-dose propofol is an effective adjuvant in reducing chemotherapy-induced emesis, we were unable to demonstrate any beneficial effect of propofol in reducing postoperative nausea and vomiting when used as the sole prophylactic medication in this patient population. Propofol may have a synergistic effect when administered with other antiemetics, or the specific antiemetic effect of propofol, if it exists, may be dose-dependent and the dose used in this study was below the efficacy threshold.

The laryngeal mask airway for thyroid and parathyroid surgery

The rôle of the laryngeal mask airway for thyroid and parathyroid surgery was studied in 97 consecutive patients. In 50% the technique combined electrical stimulation of the recurrent laryngeal nerve with visualisation of vocal cord movement via a fibreoptic bronchoscope. Stimulation was required in 10% to assist in identifying recurrent laryngeal nerve position during difficult surgical dissection. In the remaining 40% stimulation was used to confirm nerve integrity and for teaching purposes. Tracheal intubation was required for seven patients but in only two of these was intubation unplanned. The incidence of postoperative recurrent laryngeal nerve dysfunction was zero. These data suggest that the technique offers a safe alternative in airway management and may provide advantages in terms of preservation of recurrent laryngeal nerve function.

A pharmacokinetically based propofol dosing strategy for sedation of the critically ill, mechanically ventilated pediatric patient

OBJECTIVE

To assess the pharmacokinetics and pharmacodynamics of propofol sedation of critically ill, mechanically ventilated infants and children.

DESIGN

A prospective clinical study.

SETTING

A pediatric intensive care unit (ICU) in a university hospital.

PATIENTS

Clinically stable, mechanically ventilated pediatric patients were enrolled into our study after residual sedative effects from previous sedative therapy dissipated and the need for continued sedation therapy was defined. Patients were generally enrolled just before extubation.

INTERVENTIONS

A stepwise propofol dose escalation scheme was used to determine the steady-state propofol dose necessary to achieve optimal sedation, as defined by the COMFORT scale, a validated scoring system which reliably and reproducibly quantifies a pediatric patient's level of distress. When in need of continued sedation, study patients received an initial propofol loading dose of 2.5 mg/kg and were immediately started on a continuous propofol infusion of 2.5 mg/kg/hr. The propofol infusion rate was adjusted and repeat loading doses were administered, if needed, using a coordinated dosing scheme to maintain optimal sedation for a 4-hr steady-state period. After 4 hrs of optimal sedation, the propofol infusion was discontinued and simultaneous blood sampling and COMFORT scores were obtained until the patient recovered. Additional blood samples were obtained up to 24 hrs after stopping the infusion and analyzed for propofol concentration by high-performance liquid chromatography.

MEASUREMENTS AND MAIN RESULTS

Twenty-nine patients were enrolled into this study. One patient was withdrawn from this study because of an acute decrease in blood pressure occurring with the first propofol loading dose; 28 patients completed the study. All patients were sedated immediately after the first 2.5-mg/kg propofol loading dose. Eight patients were adequately sedated with the starting propofol dose regimen, whereas five patients required downward dose adjustment and 11 patients required dosage increases to achieve optimal sedation. Four patients failed to achieve adequate sedation after five dose escalations and the drug was stopped. Recovery from sedation (COMFORT score of > or = 27) after stopping the propofol infusion was rapid, averaging 15.5 mins in 23 of 24 evaluable patients. In 13 patients who were extubated after stopping the propofol infusion, the time to extubation was also rapid, averaging 44.5 mins. Determination of the blood propofol concentration at the time of recovery from propofol sedation was possible in 15 patients. The blood propofol concentration was variable, ranging between 0.262 to 2.638 mg/L but < or = 1 mg/L in 13 of 15 patients. Similarly, tremendous variation was observed in propofol pharmacokinetics. Propofol disposition was best characterized by a three-compartment model with initial rapid distribution into a small central compartment, V1, and two larger compartments, V2 and V3, which are two-and 20-fold greater in volume, respectively, than V1. Redistribution from V2 and V3 into V1 was much slower than ingress, underscoring the importance of the propofol concentration in V1 as reflective of the drug's sedative effect. Propofol was well tolerated. Two patients experienced an acute decrease in blood pressure which resolved without treatment.

CONCLUSIONS

We conclude that a descending propofol dosing strategy, which maintains the propofol concentration constant in the central compartment (V1) while drug accumulates in V2 and V3 to intercompartmental steady-state, is necessary for effective propofol sedation in the pediatric ICU. Our proposed dosing scheme to achieve and maintain the blood propofol concentration of 1 mg/L would appear effective for sedation of most clinically stable, mechanically ventilated pediatric patients.

Inhibition of regulated neuropeptide secretion from mouse pituitary cells by propofol

Neuropeptides modulate neuronal responses to stimuli. Secretion of neuropeptides is a potential site for anesthetic action. This paper examines the hypothesis that propofol alters the secretion of beta-endorphin. Cultures of a mouse pituitary cell line (AtT-20) were exposed to propofol in vitro, then induced to secrete beta-endorphin. Secretion was measured by immunoassay. Propofol caused statistically significant inhibition of secretion. Secretion stimulated by phorbol ester was inhibited by propofol with a calculated 50% inhibitory concentration (IC50) value of 48 microM. The propofol IC50 values for secretion stimulated by other secretagogs were 47 microM (barium), 42 microM (Bay K 8644, a calcium channel agonist), and 28 microM (a cyclic adenosine monophosphate [cAMP] analog). AtT-20 cells recovered their ability to secrete beta-endorphin upon removal of the propofol, which demonstrated that they were not damaged permanently by propofol. The effect was relatively specific to neuropeptide secretion, as AtT-20 cells grew normally for 5 days in the presence of 10 or 80 microM propofol. The finding suggests that propofol inhibited a site in neuropeptide exocytosis common to the three studied pathways of secretion.

Remote controlled prolonged conscious sedation for gynaecological radiotherapy

Conscious sedation with subanaesthetic doses of propofol is an effective technique for the management of highly anxious patients in dentistry. Prolonged administration of propofol to achieve conscious sedation in spontaneously breathing patients without an airway adjunct has not been reported previously. We describe the management of target-controlled conscious sedation with propofol for 21 h in a patient undergoing gynaecological radiotherapy.

Infusions of subhypnotic doses of propofol for the prevention of postoperative nausea and vomiting

We studied the antiemetic effects of a low dose infusion of propofol for 24 h after major gynaecological surgery in a double-blind, randomised, controlled trial. Fifty women of ASA physical status 1 or 2 undergoing major gynaecological surgery received an infusion of 1% propofol or intralipid at 0.1 ml.kg-1.h-1 for 24 h after surgery. Pain was managed using morphine delivered by a patient-controlled analgesia pump. The degree of postoperative nausea and vomiting was assessed by the nurses using a four-point ordinal scale, by the patients using a visual analogue scale and by the amount of rescue antiemetic given by the nurses. There were no differences between the two groups in any of the measures of postoperative nausea and vomiting during the first 48 h after surgery. Postoperative nausea and vomiting in the control group was less on the second day compared with the first postoperative day, but not in the propofol group. There were no side effects from the propofol infusion.

Propofol in chemotherapy-associated nausea and vomiting

Propofol appears to possess antiemetic actions. Limited reports have shown benefit with its use as adjuvant therapy with highly emetogenic chemotherapy regimens and as monotherapy with moderately emetogenic chemotherapy. Adverse effects have been minimal. It should be noted that to date no Phase I dose ranging studies have been described; therefore, optimal dose and duration remain unknown. Results from well-designed, controlled clinical trials in large numbers of patients are needed to define the appropriate role of propofol in antiemetic therapy. Currently, propofol must be reserved for use in clinical trials or as adjuvant therapy for patients refractory to standard 5-HT3 antagonist and corticosteroid antiemetic prophylaxis.

Comparative review of the adverse effects of sedatives used in children undergoing outpatient procedures

Children often fear medical procedures and interventions. Sedative agents enhance the care of these children who undergo outpatient procedures by decreasing anxiety, increasing cooperativity, and providing amnesia. Although higher dosages and intravenous administration of sedatives often produce improved sedation, adverse effects and complications are more frequent. The goals of therapeutic efficacy and safety must be balanced in all patients. The presence or anticipation of anxiety and pain helps in deciding whether to use a sedative alone, or a regimen also providing analgesia. The patient's clinical cardiorespiratory or neurological status, other relative contraindications, the duration of the intended procedure, and the presence or absence of an intravenous line will help in choosing specific drugs. Drug complications are a common cause of adverse events in patients. The combination of a sedative and analgesic, especially a benzodiazepine and an opioid given intravenously, is associated with a higher risk of serious complications. The practitioner responsible for the administration of a sedative to a child must be competent in its use and have the ability to detect and manage complications. Patients who are deeply sedated should be continuously monitored and observed by an individual dedicated to this task. Vital signs and oxygen saturation should be documented at frequent intervals and the patient should be appropriately monitored until discharge criteria have been met. The risk of serious complications with these agents may be reduced with vigorous monitoring and a judicious choice of dosage.

Treatment of postoperative nausea and vomiting: comparison of propofol, droperidol and metoclopramide

PURPOSE

To compare the efficacy of propofol in a subhypnotic dose (10 mg iv), droperidol (1.25 mg iv), or metoclopramide (10 mg iv) in the treatment of PONV in the post anaesthesia care unit (PACU).

METHODS

In a prospective, randomized, double-blind protocol, over four months, all eligible inpatients and outpatients were asked to give their consent to be included in the study should they suffer PONV in the PACU. They received a standardized general anaesthetic without any prophylactic antiemetic drug. In the recovery room, patients complaining of persistent nausea (lasting more than ten minutes) and/or experiencing at least two episodes of retching or vomiting were given one of the three study drugs. Recurrence of retching or vomiting was recorded for 60 min after administration of the study drug and nausea severity was assessed on a visual analog scale. Patients still complaining of PONV 30 min after administration of the study drug received a rescue medication (dimenhydrinate).

RESULTS

Seventy-eight patients received one of the study drugs. The recurrence of retching or vomiting was higher with propofol (58%) than with droperidol (4%) or metoclopramide (24%) (P < 0.001). More patients who received propofol needed the rescue medication (54%) than those who received droperidol (15%) or metoclopramide (28%) (P < 0.02). No difference was observed in nausea severity.

CONCLUSION

A subhypnotic dose of propofol (10 mg iv) is less effective than the conventional antiemetic drugs droperidol and metoclopramide for the treatment of PONV in the PACU.

A comparison between total intravenous anaesthesia using a propofol/alfentanil mixture and an inhalational technique for laparoscopic gynaecological sterilization

Thirty patients undergoing laparoscopic gynaecological sterilization, as day-cases, were randomly allocated to receive either total intravenous anaesthesia (TIVA) with a propofol and alfentanil mixture or a standard inhalational technique. Immediate recovery, as measured by times to awakening, co-operation and orientation, and psychomotor recovery, as measured by 'P' deletion studies, were not significantly different between the two groups. TIVA produced a significant reduction in post-operative nausea at both 1 and 2 h post-operatively, as measured by a visual analogue scale (P < 0.01). No patient in the TIVA group vomited whereas two vomited in the inhalational group. There were no differences between the two groups with respect to suitability for discharge home and no incidences of awareness. We conclude that TIVA with a propofol and alfentanil mixture provides satisfactory anaesthesia for gynaecological sterilization, with good recovery characteristics and a low incidence of post-operative nausea and vomiting.

Neurological and psychiatric adverse effects of anaesthetics: epidemiology and treatment

The practice of anaesthesia has changed considerably over the past 20 to 30 years owing largely to technological advances in patient monitoring and an expanded and improved pharmacological repertoire. While patient safety in anaesthesia has greatly improved, the risk of neurological and psychiatric adverse effects of anaesthetics remains and is the focus of continued investigation. For example, a great deal of attention has recently been directed at intraoperative awareness. This adverse event can be caused by delivering an inappropriate amount or type of anaesthetic. Another risk of anaesthesia involves drug-induced unpleasant subjective states in patients. Those drugs most frequently associated with these states include ketamine, droperidol and scopolamine. This risk can often be attenuated by careful adjustment of drug dose and the use of adjunctive agents such as benzodiazepines which may produce amnesia of the unpleasant subjective state. While it is well established that modern anaesthetic drugs cause acute impairment of cognition and psychomotor functioning, there is little evidence that these drugs have long term impairing effects. Finally, a particular kind of surgery, cardiac surgery requiring cardiopulmonary bypass, can be associated with adverse neurological and psychiatric sequelae which, while not directly related to anaesthesia, are of intense interest to anaesthesiologists.

Propofol. An overview of its pharmacology and a review of its clinical efficacy in intensive care sedation

Propofol is a phenolic derivative that is structurally unrelated to other sedative hypnotic agents. It has been used extensively as an anaesthetic agent, particularly in procedures of short duration. More recently it has been investigated as a sedative in the intensive care unit (ICU) where it produces sedation and hypnosis in a dose-dependent manner. Propofol also provides control of stress responses and has anticonvulsant and amnesic properties. Importantly, its pharmacokinetic properties are characterised by a rapid onset and short duration of action. Noncomparative and comparative trials have evaluated the use of propofol for the sedation of mechanically ventilated patients in the ICU (postsurgical, general medical, trauma). Overall, propofol provides satisfactory sedation and is associated with good haemodynamic stability. It produces results similar to or better than those seen with midazolam or other comparator agents when the quality of sedation and/or the amount of time that patients were at adequate levels of sedation are measured. Patients sedated with propofol also tend to have a faster recovery (time to spontaneous ventilation or extubation) than patients sedated with midazolam. Although most studies did not measure time to discharge from the ICU, propofol tended to be superior to midazolam in this respect. In a few small trials in patients with head trauma or following neurosurgery, propofol was associated with adequate sedation and control of cerebral haemodynamics. The rapid recovery of patients after stopping propofol makes it an attractive option in the ICU, particularly for patients requiring only short term sedation. In short term sedation, propofol, despite its generally higher acquisition costs, has the potential to reduce overall medical costs if patients are able to be extubated and discharged from the ICU sooner. Because of the potential for hyperlipidaemia and the development of tolerance to its sedative effects, and because of the reduced need for rapid reversal of drug effects in long term sedation, the usefulness of propofol in long term situations is less well established. While experience with propofol for the sedation of patients in the ICU is extensive, there are still areas requiring further investigation. These include studies in children, trials examining cerebral and haemodynamic outcomes following long term administration and in patients with head trauma and, importantly, pharmacoeconomic investigations to determine those situations where propofol is cost effective. In the meantime, propofol is a well established treatment native to benzodiazepines and/or other hypnotics or analgesics when sedation of patients in the ICU is required. In particular, propofol possesses unique advantages over these agents in patients requiring only short term sedation.

Inhibition by propofol (2,6 di-isopropylphenol) of the N-methyl-D-aspartate subtype of glutamate receptor in cultured hippocampal neurones

1. The effects of propofol (2,6 di-isopropylphenol) on responses to the selective glutamate receptor agonists, N-methyl-D-aspartate (NMDA) and kainate, were investigated in cultured hippocampal neurones of the mouse. Whole cell and single channel currents were recorded by patch-clamp techniques. Drugs were applied with a multi-barrel perfusion system. 2. Propofol produced a reversible, dose-dependent inhibition of whole cell currents activated by NMDA. The concentration of propofol which induced 50% of the maximal inhibition (IC50) was approximately 160 microM. The maximal inhibition was incomplete leaving a residual current of about 33% of the control response. This inhibitory action of propofol was neither voltage- nor use-dependent. 3. Analysis of the dose-response relation for whole cell NMDA-activated currents indicated that propofol caused no significant change in the apparent affinity of the receptor for NMDA. 4. Outside-out patch recordings of single channel currents evoked by NMDA (10 microM) revealed that propofol (100 microM) reversibly decreased the probability of channel opening but did not influence the average duration of channel opening or single channel conductance. 5. Whole-cell currents evoked by kainate (50 microM) were insensitive to propofol (1 microM-1 mM). 6. These results indicate that propofol inhibits the NMDA subtype of glutamate receptor, possibly through an allosteric modulation of channel gating rather than by blocking the open channel. Depression of NMDA-mediated excitatory neurotransmission may contribute to the anaesthetic, amnesic and anti-convulsant properties of propofol.

Cost analysis of propofol versus thiopental induction anesthesia in outpatient laparoscopic gynecologic surgery

This study investigated the cost of propofol versus thiopental anesthesia in 243 patients who underwent outpatient laparoscopic gynecologic surgery. Patients records were analyzed for medication use, duration of surgery, anesthesia, recovery room stay, and associated costs. Despite the higher drug cost for propofol, the total mean cost was $273.00 less per patient for patients receiving propofol induction anesthesia. Extension of these data translates into cost savings of approximately $7900.00 if propofol had been used for all patients. Although the duration of surgery for the propofol group was shorter by nearly 12 minutes, the anesthesia duration and recovery room stay were both longer for the thiopental group, reflecting the longer duration of action of thiopental. Although the realized cost savings of drugs, surgery, anesthesia, and recovery time when propofol versus thiopental is used for outpatient laparoscopic gynecologic surgery are relatively small on an individual patient basis, cost savings may become more significant if larger patient populations are studied.

Cerebrospinal fluid 5-hydroxyindoleacetic acid and homovanillic acid in the pediatric opsoclonus-myoclonus syndrome

To study the purported role of central monoamine disturbances in the pathophysiology of the opsoclonus-myoclonus syndrome, the serotonin metabolite 5-hydroxyindoleacetic acid and the dopamine metabolite homovanillic acid were measured in cerebrospinal fluid samples from 27 affected children and 47 age- and gender-matched control subjects by high-pressure liquid chromatography with electrochemical detection. 5-Hydroxyindoleacetic acid and homovanillic acid concentrations in the cerebrospinal fluid were approximately 30 to 40% lower in opsoclonus-myoclonus patients compared to control subjects, and the normal inverse correlation between age and monoamine metabolite concentrations in the cerebrospinal fluid of control subjects was not found in opsoclonus-myoclonus patients. Patients with the lowest values were less than 4 years old, and a subgroup had extremely low levels, but differences in older children were not significant. Cerebrospinal fluid levels of 5-hydroxyindoleacetic acid and homovanillic acid were more positively correlated in control subjects than in opsoclonus-myoclonus patients. None of the patients exhibited high levels of monoamine metabolites. Homovanillic acid levels were slightly lower in the cerebrospinal fluid of patients receiving corticotropin or steroids at the time of lumbar puncture. Clinical variables that could be excluded were paraneoplastic etiology, anesthetic for lumbar puncture, syndrome duration, age at onset, gender, response to steroids, length of time until initiation of corticotropin or steroids, presence of seizures, opsoclonus, and functional impairment. These data suggest a disturbance and possible altered ontogeny of serotonin or dopamine neurotransmission in a subpopulation of children with opsoclonus-myoclonus with low cerebrospinal fluid levels of 5-hydroxyindoleacetic acid and homovanillic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Propofol and seizures

It is now clear that "seizure activity", excitatory phenomena, and/or a disorder of muscle tone are potential complications of the use of propofol. Whether this "seizure activity" is primarily, secondarily, or not at all a cerebral cortical event is still to be elucidated. Clearly propofol does have anticonvulsant activity, and also clearly it can produce an involuntary movement disorder, in certain patients, under certain conditions. Propofol is not the first anaesthetic drug to be implicated in the causation of seizures or abnormal movements nor indeed the first to appear to have anti-convulsant and proconvulsant activity (e.g. Althesin). While propofol has undoubtedly proved a very useful drug, the problem of convulsive phenomena creates a degree of background concern about its use. More needs to be known about the mechanism of this complication and any risk factors involved in determining who may have a seizure after propofol. In the clinical setting, the reporting of seizures possibly related to propofol should include--medical history, including personal or family history of epilepsy and movement disorders; a history of previous anaesthetics and whether propofol was used; regular medications; use of drugs or alcohol; history of chemical dependency; emotional state prior to induction; presence of hyperventilation or fever; a description of the alleged seizure, including rate of administration of propofol and amount given, time of onset of seizure in relation to time of drug administration, speed of onset of signs, quality of the abnormal movements, part of body involved, duration, any indication of a postictal state, any cardiovascular changes which may have accompanied the seizure, and any other possible triggers for the reaction such as other drugs used, including premedication; post seizure investigations including temperature, blood sugar, electrolytes, arterial gas analysis, neurological examination, EEG and CT scan. These actions and these investigations concerning propofol should not be delayed. It would appear appropriate to recommend to patients who experience apparent convulsive phenomena after propofol that they not be re-exposed to the drug.