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

SEDATION OF SIMULATED ICU PATIENTS USING REINFORCEMENT LEARNING BASED CONTROL

The Intensive Care Unit (ICU) is a challenging environment to both patient and caregiver. Continued shortages in staffing increase risk to patients. To evaluate the use of intelligent systems in the improvement of patient care, an intelligent agent was developed to regulate ICU patient sedation. A temporal differencing form of reinforcement learning was used to train the agent in the administration of intravenous propofol in simulated ICU patients. The agent utilized a well-studied pharmacokinetic model to calculate the distribution of drug within the patient. Pharmacodynamics were then estimated for the drug effect. A derivative of the electroencephalograms, the bispectral index, served as the system control variable. The agent demonstrated satisfactory control of the simulated patient's consciousness level in static and dynamic setpoint conditions. The agent demonstrated superior stability and responsiveness when compared to a well-tuned PID controller, the control method of choice in closed-loop sedation control literature.

Effects of propofol on P2X7 receptors and the secretion of tumor necrosis factor-α in cultured astrocytes

Upon CNS injury, adenosine-5'-triphosphate is released and acts on P2X7 receptors, which might influence many cytokines secretion from glial cells and, in turn, affects the survival of neurons. Propofol, an intravenous anesthetic, has been shown to provide neuroprotective effect. However, the effect of propofol on astrocyte-associated processes remains to be clarified. In this study, we investigated the effects of propofol on P2X7 activity in astrocytes and tumor necrosis factor-α (TNF-α) secretion from these cells and thereby to infer the possible role(s) of glial P2X7 receptors in propofol neural protective effects. Whole-cell patch clamp results showed that in clinically relevant concentrations (3.3, 10 or 33 μM), propofol increased the P2X7 current amplitudes significantly and propofol in 10 μM extended the inactivation times of P2X7 receptors. Enzyme-linked immunosorbent assay showed that propofol increased the secretion of TNF-α from astrocytes in high concentration (300 μM), while inhibited in clinically relevant concentration (10 μM). Both of these effects were not influenced by Brilliant blue G. These results suggest that in clinically relevant concentrations, propofol increases the activity of P2X7 receptors in activated astrocytes, but this does not contribute to the downregulation of the secretion of TNF-α.

Effects of orexin-A on propofol anesthesia in rats

PURPOSE

An active sleep homeostatic process is present during propofol anesthesia. Activation of the orexin system induces wakefulness, and inhibition of the orexin system causes narcolepsy. We hypothesized that orexin would affect propofol anesthesia.

METHODS

The effects of an intracerebroventricular (i.c.v.) injection of orexin-A (OXA) or an orexin-1 (OX-1) receptor antagonist, SB-334867, on the times to the loss and return of the righting reflex induced by propofol were examined in Wistar rats. The effects of propofol or OXA on norepinephrine (NE) and dopamine (DA) release from the prefrontal cortex (PFC) were examined using in vivo microdialysis.

RESULTS

An i.c.v. injection of OXA (1 nmol) decreased the time to emergence from propofol anesthesia mediated by the OX-1 receptor without changing anesthetic induction (n = 8). An i.c.v. injection of SB-334867 (5 and 50 nmol) increased the time to emergence from propofol anesthesia without changing anesthetic induction (n = 8). Intravenous infusion of propofol decreased NE (48 ± 8%; n = 8) and DA (61.2 ± 11%; n = 8) release from PFC mediated by the GABA(A) receptor. An i.c.v. injection of OXA reversed the decreases in NE and DA release induced by propofol mediated by the OX-1 receptor (n = 8).

CONCLUSION

These results indicate that the orexin system may accelerate the emergence from propofol anesthesia associated with increases in the central noradrenergic and dopaminergic activity.

Fospropofol

Fospropofol (fospropofol disodium), a sedative/hypnotic agent, is a water-soluble prodrug of propofol, metabolized in vivo to produce liberated propofol (producing the sedative effect), phosphate and formaldehyde. Intravenous fospropofol 6.5 mg/kg was significantly more effective than fospropofol 2.0 mg/kg (a placebo surrogate) as sedation in patients undergoing colonoscopy or flexible bronchoscopy, with regard to the primary endpoint of sedation success rate in randomized, double-blind, phase III trials. In patients undergoing colonoscopy, the sedation success rate was >3-fold higher among fospropofol 6.5 mg/kg (n = 158) than fospropofol 2.0 mg/kg recipients (n = 102). Similar results were observed in patients undergoing flexible bronchoscopy; the sedation success rate was >3-fold greater among fospropofol 6.5 mg/kg (n = 150) than among fospropofol 2.0 mg/kg recipients (n = 102). Fospropofol was generally well tolerated in clinical trials. Adverse events were mostly of mild to moderate severity, and were transient and self-limiting. Patients undergoing flexible bronchoscopy appeared to have a higher rate of sedation-related adverse events requiring airway assistance than did those undergoing colonoscopy or minor procedures.

Polymorphism of human cytochrome P450 enzymes and its clinical impact

Pharmacogenetics is the study of how interindividual variations in the DNA sequence of specific genes affect drug response. This article highlights current pharmacogenetic knowledge on important human drug-metabolizing cytochrome P450s (CYPs) to understand the large interindividual variability in drug clearance and responses in clinical practice. The human CYP superfamily contains 57 functional genes and 58 pseudogenes, with members of the 1, 2, and 3 families playing an important role in the metabolism of therapeutic drugs, other xenobiotics, and some endogenous compounds. Polymorphisms in the CYP family may have had the most impact on the fate of therapeutic drugs. CYP2D6, 2C19, and 2C9 polymorphisms account for the most frequent variations in phase I metabolism of drugs, since almost 80% of drugs in use today are metabolized by these enzymes. Approximately 5-14% of Caucasians, 0-5% Africans, and 0-1% of Asians lack CYP2D6 activity, and these individuals are known as poor metabolizers. CYP2C9 is another clinically significant enzyme that demonstrates multiple genetic variants with a potentially functional impact on the efficacy and adverse effects of drugs that are mainly eliminated by this enzyme. Studies into the CYP2C9 polymorphism have highlighted the importance of the CYP2C9*2 and *3 alleles. Extensive polymorphism also occurs in other CYP genes, such as CYP1A1, 2A6, 2A13, 2C8, 3A4, and 3A5. Since several of these CYPs (e.g., CYP1A1 and 1A2) play a role in the bioactivation of many procarcinogens, polymorphisms of these enzymes may contribute to the variable susceptibility to carcinogenesis. The distribution of the common variant alleles of CYP genes varies among different ethnic populations. Pharmacogenetics has the potential to achieve optimal quality use of medicines, and to improve the efficacy and safety of both prospective and currently available drugs. Further studies are warranted to explore the gene-dose, gene-concentration, and gene-response relationships for these important drug-metabolizing CYPs.

Propofol infusion syndrome: case report and literature review

PURPOSE

A case of propofol infusion syndrome in a patient with respiratory failure and sepsis is reported.

SUMMARY

A 36-year-old Hispanic woman was admitted to the medical intensive care unit for treatment of respiratory failure and sepsis, likely secondary to pneumonia. Her medical history included human immunodeficiency virus infection and chronic hepatitis C virus infection. She was intubated and placed on mechanical ventilation. Empirical i.v. antimicrobial therapy was initiated with vancomycin, moxifloxacin, piperacillin-tazobactam, trimethoprim-sulfamethoxazole, and micafungin, along with corticosteroids and vasopressors. Propofol 1.5 mg/kg per hour i.v. and midazolam i.v. were initiated for sedation, but the dosages of both propofol and midazolam needed to be increased due to persistent agitation. On hospital day 7, the patient developed a morbilliform rash on her neck, shoulders, and chest and multiple abnormal laboratory test values, including elevated levels of alanine transaminase, aspartate transaminase, amylase, lipase, creatine kinase, and triglycerides. Serial electrocardiograms revealed sinus tachycardia. Computed tomography of the abdomen showed hepatomegaly with fatty infiltration of the liver, no gallstones, and a normal pancreas. I.V. phenobarbital was added for sedation, and propofol was tapered and discontinued on the same day. The patient responded adequately to phenobarbital maintenance therapy and was eventually weaned off all other sedatives. The patient's laboratory test values returned to normal within 72 hours after discontinuation of the propofol infusion, and the rash and tachycardia resolved.

CONCLUSION

Propofol infusion syndrome developed in a patient with respiratory failure and sepsis after a prolonged infusion of high-dose propofol.

Evaluation of the efficacy and safety for use of two sedation and analgesia protocols to facilitate assisted ventilation of healthy dogs

OBJECTIVE

To determine the effectiveness and safety of 2 sedative-analgesic protocols to facilitate assisted ventilation in healthy dogs.

ANIMALS

12 healthy dogs.

PROCEDURES

Dogs were randomly assigned to 2 groups. Mean dosages for protocol 1 were diazepam (0.5 mg/kg/h [n = 3 dogs]) or midazolam (0.5 mg/kg/h [3]), morphine (0.6 mg/kg/h [6]), and medetomidine (1.0 microg/kg/h [6]). Mean dosages for protocol 2 were diazepam (0.5 mg/kg/h [n = 3]) or midazolam (0.5 mg/kg/h [3]), fentanyl (18 microg/kg/h [6]), and propofol (2.5 mg/kg/h [6]). Each dog received the drugs for 24 consecutive hours. All dogs were mechanically ventilated with adjustments in minute volume to maintain normocapnia and normoxemia. Cardiorespiratory variables were recorded. A numeric comfort score was assigned hourly to assess efficacy. Mouth care, position change, and physiotherapy were performed every 6 hours. Urine output was measured every 4 hours.

RESULTS

Use of both protocols maintained dogs within optimal comfort ranges > 85% of the time. The first dog in each group was excluded from the study. Significant decreases in heart rate, oxygen consumption, and oxygen extraction ratio were evident for protocol 1. Cardiac index values in ventilated dogs were lower than values reported for healthy unsedated dogs. Oxygen delivery, lactate concentration, and arterial base excess remained within reference ranges for both protocols.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of both protocols was effective for facilitating mechanical ventilation. A reduction in cardiac index was detected for both protocols as a result of bradycardia. However, oxygen delivery and global tissue perfusion were not negatively affected.

[Agents for sedation and analgesia in the intensive care unit]

Sedation-analgesia for critically ill patients is usually performed with the combination of a sedative agent and an opioid. Midazolam and propofol are the agents most commonly used for sedation in ICU. The quality of the sedation is quite comparable with both agents, but pharmacokinetic properties of propofol allow a more rapid weaning process from mechanical ventilation. However, implementation of algorithms to adjust drug dosages reduces ventilator days and limits the kinetic differences between propofol and midazolam. Among the adverse events associated with propofol, propofol infusion syndrome is a rare but lethal aspect of propofol therapy. Opioids are the mainstay of analgesic therapy. They interact synergistically with hypnotics. Sufentanil, fentanyl and morphine are the most frequently used opioids. Remifentanil is an ultrashort acting opiate that does not appear to accumulate with prolonged use. The advent of remifentanil has allowed the use of analgesia-based sedation.

Medication-related complications in the trauma patient

Trauma patients are twice as likely to have adverse reactions to medication as nontrauma patients. The need for medication in trauma patients is high. Surgery is often necessary, and immunosuppression and hypercoagulability may be present. Adverse drug events can be caused in part by altered pharmacokinetics, drug interactions, and polypharmacy. Medications may also have serious long-term adverse effects, which must be considered. It is not the purpose of this review article to discuss all adverse effects of all medications. This article will discuss the more common adverse effects of medications for trauma patients in the acute care setting, in the following categories: pain control, sedation, antibiotics, seizure prophylaxis in head trauma, atrial fibrillation, deep vein thrombosis and pulmonary embolism prophylaxis, hemodynamic support, adrenal insufficiency, factor VIIa.

Propofol-related infusion syndrome in intensive care patients

The Institute of Medicine has identified adverse drug events as factors that significantly contribute to increased patient morbidity and mortality. As critically ill patients receive numerous drugs to treat a multitude of complicated health problems, they are at high risk for adverse drug events. Sedation is often a key requirement for the optimal management of critical illness, and propofol, a common sedative, has many desirable characteristics that make it the ideal agent in numerous circumstances. However, over the last decade, increasing numbers of reports have described a potentially fatal adverse effect called propofol-related infusion syndrome. Whether this adverse drug event is preventable is unclear, but recommendations have been proposed to minimize the potential for development of this syndrome. Research is under way to collect data on the use of propofol in intensive care units and on its prevalence.

Neuroprotective effects of propofol in acute cerebral injury

Propofol (2,6-diisopropylphenol) is one of the most popular agents used for induction of anesthesia and long-term sedation, owing to its favorable pharmacokinetic profile, which ensures a rapid recovery even after prolonged administration. A neuroprotective effect, beyond that related to the decrease in cerebral metabolic rate for oxygen, has been shown to be present in many in vitro and in vivo established experimental models of mild/moderate acute cerebral ischemia. Experimental studies on traumatic brain injury are limited and less encouraging. Despite the experimental results and the positive effects on cerebral physiology (propofol reduces cerebral blood flow but maintains coupling with cerebral metabolic rate for oxygen and decreases intracranial pressure, allowing optimal intraoperative conditions during neurosurgical operations), no clinical study has yet indicated that propofol may be superior to other anesthetics in improving the neurological outcome following acute cerebral injury. Therefore, propofol cannot be indicated as an established clinical neuroprotectant per se, but it might play an important role in the so-called multimodal neuroprotection, a global strategy for the treatment of acute injury of the brain that includes preservation of cerebral perfusion, temperature control, prevention of infections, and tight glycemic control.

Comparison of propofol with pentobarbital/midazolam/fentanyl sedation for magnetic resonance imaging of the brain in children

OBJECTIVE

Propofol and pentobarbital, alone or combined with other agents, are frequently used to induce deep sedation in children for MRI. However, we are unaware of a previous comparison of these 2 agents as part of a randomized, controlled trial. We compared the recovery time of children after deep sedation with single-agent propofol with a pentobarbital-based regimen for MRI and considered additional variables of safety and efficacy.

METHODS

This prospective, randomized trial at a tertiary children's hospital enrolled 60 patients 1 to 17 years old who required intravenous sedation for elective cranial MRI. Patients were assigned randomly to receive a loading dose of propofol followed by continuous intravenous infusion of propofol or to receive sequential doses of midazolam, pentobarbital, and fentanyl until a modified Ramsay score of >4 was attained. A nurse who was blind to group assignment assessed discharge readiness (Aldrete score > 8) and administered a follow-up questionnaire. We compared recovery time, time to induction of sedation, total sedation time, quality of imaging, number of repeat-image sequences, adverse events, caregiver satisfaction, and time to return to presedation functional status.

RESULTS

The groups were similar in age, gender, race, American Society of Anesthesiology physical status class, and frequency of cognitive impairment. No sedation failure or significant adverse events were observed. Propofol offered significantly shorter sedation induction time, recovery time, total sedation time, and time to return to baseline functional status. Caregiver satisfaction scores were also significantly higher in the patients in the propofol group.

CONCLUSIONS

Propofol permits faster onset and recovery than, and comparable efficacy to, a pentobarbital/midazolam/fentanyl regimen for sedation of children for MRI.

Anesthetic practice in Japan: past, present, and future

Significant progress has been made over the past 20 years in the development of anesthetic agents and anesthetic monitors. Due to progress in the development of medical devices and the establishment of an effective medical system, advanced age alone is no longer a contraindication for surgery. However, despite approval of the volatile anesthetic sevoflurane, Japan is lagging behind other developed countries with regard to anesthetic agents. The ultrashort-acting opioid analgesic remifentanil has finally become available in Japan, and the fast-onset neuromuscular blocking agent rocuronium is expected to be approved soon. Patient recruitment for phase III clinical trials using sugammadex, a selective reversal agent for rocuronium and vecuronium, has been completed in all countries, including Japan. In this article, changes in anesthesia over the past two decades are described and possible future changes in anesthesia in Japan are discussed.

Emulsion of flurbiprofen axetil reduces propofol injection pain due to a decrease in free propofol concentration

PURPOSE

Flurbiprofen axetil emulsion (FA), a prodrug of nonsteroidal anti-inflammatory drugs (NSAIDs) that is widely used for perioperative pain relief in Japan, has been effective for reducing propofol injection pain, but the mechanism is unclear. The purpose of this study was to test the hypothesis that the reduction of propofol injection pain by FA may be attributed to a decrease in free propofol concentration.

METHODS

Diprivan (propofol emulsion; Dipri; AstraZeneca, Cheshire, UK) and Propofol-Lipuro (Lipuro; B. Braun, Melsungen, Germany) were used. A randomized double-blind study was performed to compare pain on injection with six kinds of propofol solution: plain Dipri, a 3 : 1 (v/v) mixture of Dipri and saline (Dipri-S), a 3 : 1 mixture of Dipri and FA (Dipri-FA), plain Lipuro, a 3 : 1 mixture of Lipuro and saline (Lipuro-S), and a 3 : 1 mixture of Lipuro and FA (Lipuro-FA). Three hundred patients (American Society of Anesthesiologists [ASA] physical status [PS] I-II) scheduled for elective surgery received one of these six propofol emulsions (n = 50, each group). Injection pain was evaluated every 10 s after the start of a 1-min infusion of up to 2 mg x kg(-1) propofol. We also measured the in vitro free propofol concentrations of the propofol preparations that we tested (n = 5, each).

RESULTS

The mixture of FA with propofol decreased the incidence of injection pain, compared with plain propofol, for Lipuro (P < 0.01) but not for Dipri. The free propofol concentration in each emulsion in vitro was also decreased by mixing the propofol with saline or FA. The incidence of pain was reduced in a free-propofol concentration-dependent manner (R(2) = 0.926).

CONCLUSION

The findings suggest that the reduction of propofol injection pain by FA may be explained, at least in part, by a reduction in the free propofol concentration.

Lethal self administration of propofol (Diprivan). A case report and review of the literature

The death of a female anaesthesiologist is reported. Although the situation at the scene indicated propofol overdose-related death, self-administration of such high doses of propofol was unlikely, given the pharmacological properties of this drug. The analysis of the situation at the scene and the toxicological analysis in which the blood and liver propofol concentrations were 2.40microg/ml and 0.56microg/g, respectively, supported the conclusion that the death was a consequence of propofol self-administration at therapeutic doses from a person who used the drug on chronic basis seeking to its euphoric effects. However, because the toxic concentrations of propofol in non-intubated patients may be different from those intubated and fully supported in the operating room or in the intensive care unit, a mere interpretation of the blood and tissue concentrations of propofol in the toxicological analysis can confirm the drug intake but it may be of limited diagnostic significance without taking into account this difference.

The Effect of Electroencephalogram-Targeted High- and Low-Dose Propofol Infusion on Histopathological Damage After Traumatic Brain Injury in the Rat

BACKGROUND

Propofol is commonly used to sedate patients after traumatic brain injury. However, the dose-dependent neuroprotective effects of propofol after head trauma are unknown. We compared histopathological damage after 6 h of electroencephalogram-targeted high- and low-dose propofol infusion in rats subjected to controlled cortical impact (CCI).

METHODS

Animals were randomly assigned to CCI/propofol with electroencephalogram burst-suppression-ratio 1%-5% (CCI/lowprop), CCI/propofol with burst-suppression-ratio 30%-40% (CCI/highprop), control group CCI/1.0 vol % halothane (CCI/halo), or sham group with halothane anesthesia (SHAM/halo). Brain slices were stained with kresyl violet (KV) and hematoxylin/eosin (HE) to evaluate lesion volume, number of eosinophilic cells, and activation of caspase-3 in the hippocampus.

RESULTS

Lesion volume (mm3) and number of eosinophilic cells in the hippocampus did not differ significantly [lesion volumes: CCI/lowprop 31.55 +/- 14.66 (KV) and 53.77 +/- 8.62 (HE); CCI/highprop 33.81 +/- 10.57 (KV) and 52.30 +/- 11.55 (HE); CCI/halo 36.42 +/- 17.06 (KV) and 57.95 +/- 8.49 (HE)]. Activation of caspase-3 occurred in the ipsilateral hippocampus in all CCI-groups.

CONCLUSION

Despite different levels of cortical neuronal function, there were no relevant differences in the short-term histopathological damage. These results challenge the view that the neuroprotective effect of propofol relates to the suppression of cerebral metabolic demand.

Therapy of intracranial hypertension in patients with fulminant hepatic failure

Severe intracranial hypertension (IH) in the setting of fulminant hepatic failure (FHF) carries a high mortality and is a challenging disease for the critical care provider. Despite considerable improvements in the understanding of the pathophysiology of cerebral edema during liver failure, therapeutic maneuvers that are currently available to treat this disease are limited. Orthotopic liver transplantation is currently the only definitive therapeutic strategy that improves outcomes in patients with FHF. However, many patients die prior to the availability of donor organs, often because of cerebral herniation. Currently, two important theories prevail in the understanding of the pathophysiology of IH during FHF. Ammonia and glutamine causes cytotoxic cerebral injury while cerebral vasodilation caused by loss of autoregulation increases intracranial pressure (ICP) and predisposes to herniation. Although ammonia-reducing strategies are limited in humans, modulation of cerebral blood flow seems promising, at least during the early stages of hepatic encephalopathy. ICP monitoring, transcranial Doppler, and jugular venous oximetry offer valuable information regarding intracranial dynamics. Induced hypothermia, hypertonic saline, propofol sedation, and indomethacin are some of the newer therapies that have been shown to improve survival in patients with severe IH. In this article, we review the pathophysiology of IH in patients with FHF and outline various therapeutic strategies currently available in managing these patients in the critical care setting.

Preventing pain during injection of propofol: effects of a new emulsion with lidocaine addition

BACKGROUND AND OBJECTIVE

Previous studies found that lidocaine addition to propofol long-chain triglyceride was associated with a lower incidence of injection pain than medium-chain triglyceride/long-chain triglyceride formulation, but the incidence was still high (31-40%). Our study investigated whether the incidence of injection pain could be further reduced by the addition of lidocaine (10 mg, 20:1) to propofol medium-chain triglyceride/long-chain triglyceride.

METHODS

In a randomized double-blind controlled trial 464 patients scheduled to undergo regional anaesthesia were assigned to receive one of the following four options: propofol medium-chain triglyceride/long-chain triglyceride + lidocaine, propofol long-chain triglyceride + lidocaine, propofol medium-chain triglyceride/long-chain triglyceride or propofol long-chain triglyceride. Propofol was injected to reach grade 3 of the Observer's Assessment of Alertness/Sedation scale.

RESULTS

Incidence of injection pain was 18% in the propofol medium-chain triglyceride/long-chain triglyceride + lidocaine group, 31% in the propofol long-chain triglyceride + lidocaine group, 47% in the propofol medium-chain triglyceride/long-chain triglyceride group and 60% in the long-chain triglyceride group. Propofol medium-chain triglyceride/long-chain triglyceride + lidocaine was associated with a statistically significant reduced incidence of injection pain compared with propofol long-chain triglyceride +lidocaine (P =0.0249, number needed to treat =7.7).

CONCLUSIONS

Premixing propofol medium-chain triglyceride/long-chain triglyceride with lidocaine is one of the most effective measures currently available to reduce the incidence of injection pain in sedated patients during regional anaesthesia.

Propofol for sedation in neuro-intensive care

Interventions in the intensive care unit often require that the patient be sedated. Propofol is a widely used, potent sedative agent that is popular in critical care and operating room settings. In addition to its sedative qualities, propofol has neurovascular, neuroprotective, and electroencephalographical effects that are salutory in the patient in neurocritical care. However, the 15-year experience with this agent has not been entirely unbesmirched by controversy: propofol also has important adverse effects that must be carefully considered. This article discusses and reviews the pharmacology of propofol, with specific emphasis on its use as a sedative in the neuro-intensive care unit. A detailed explanation of central nervous system and cardiovascular mechanisms is presented. Additionally, the article reviews the literature specifically pertaining to neurocritical care use of propofol.

Pharmacokinetic and Pharmacodynamic Characteristics of??Medications Used for Moderate Sedation

The ability to deliver safe and effective moderate sedation is crucial to the ability to perform invasive procedures. Sedative drugs should have a quick onset of action, provide rapid and clear-headed recovery, and be easy to administer and monitor. A number of drugs have been demonstrated to provide effective sedation for outpatient procedures but since each agent has its own limitations, a thorough knowledge of the available drugs is required to choose the appropriate drug, dose and/or combination regimen for individual patients. Midazolam, propofol, ketamine and sevoflurane are the most frequently used agents, and all have a quick onset of action and rapid recovery. The primary drawback of midazolam is the potential for accumulation of the drug, which can result in prolonged sedation and a hangover effect. The anaesthetics propofol and sevoflurane have recently been used for sedation in procedures of short duration. Although effective, these agents require monitored anaesthesia care. Ketamine is an effective agent, particularly in children, but there is concern regarding emergence reactions. AQUAVAN injection (fospropofol disodium), a phosphorylated prodrug of propofol, is an investigational agent possessing a unique and distinct pharmacokinetic and pharmacodynamic profile. Compared with propofol emulsion, AQUAVAN is associated with a slightly longer time to peak effect and a more prolonged pharmacodynamic effect. Advances in the delivery of sedation, including the development of new sedative agents, have the potential to further improve the provision of moderate sedation for a variety of invasive procedures.

AQUAVAN® Injection, a Water-soluble Prodrug of Propofol, as a Bolus Injection: A Phase I Dose-escalation Comparison with DIPRIVAN® (Part 2): Pharmacodynamics and Safety: Retracted

BACKGROUND

AQUAVAN Injection (AQ) (GPI 15715; Guilford Pharmaceuticals Inc., Baltimore, MD) is a water-soluble prodrug of propofol. The authors explored the pharmacodynamics and safety of AQ and compared it with propofol lipid emulsion (PropofolD).

METHODS

After institutional review board approval, 36 volunteers with American Society of Anesthesiologists physical status of I were randomly allocated into six cohorts (male/female: 3/3 per cohort) and given a single bolus of AQ (5, 10, 15, 20, 25, or 30 mg/kg). A Bispectral Index monitor (Aspect Medical Systems Inc., Newton, MA) measured the hypnotic effect. The lowest Bispectral Index level (BISpeak) was recorded. One week later, PropofolD was given to the same subjects at 50 mg/min to reach a similar BISpeak. Heart rate, oxygen saturation measured by pulse oximetry, blood pressure, and side effects were monitored. Incidence and duration of apnea and loss (LOCverbal) and return of response to verbal command were measured. A population compartmental pharmacokinetic-pharmacodynamic model was developed for AQ using NONMEM and evaluated using simulations, leverage, and bootstrap analyses.

RESULTS

In the higher dosages (cohorts 4-6), all subjects achieved LOCverbal. Similar times until LOCverbal were seen for AQ and PropofolD. A dose-related increase in duration of LOCverbal was longer for AQ than for PropofolD. AQ BISpeak occurred later than with PropofolD. Pain on injection was only present with PropofolD (12 of 36). With AQ, transient paresthesias and pruritus were seen. Hemodynamic profiles were similar for both drugs, except for an initial tachycardia after AQ administration. Dose-dependent apnea was more pronounced with PropofolD than with AQ. The AQ combined pharmacokinetic-pharmacodynamic profile was best described by a nonlinear, six-compartment pharmacokinetic model and an effect site compartment. A dependency of the ke0 value on the PropofolGPI plasma concentration was noted.

CONCLUSION

Bolus administration of AQ achieves LOCverbal at a similar time as an equipotent amount of PropofolD but shows a longer time to BISpeak and prolonged pharmacodynamics. For both drugs, excellent drug safety was achieved, although there was a tendency of fewer and shorter duration of apneas for AQ.

AQUAVAN® Injection, a Water-soluble Prodrug of Propofol, as a Bolus Injection: A Phase I Dose-escalation Comparison with DIPRIVAN® (Part 1): Pharmacokinetics: Retracted

BACKGROUND

AQUAVAN Injection (AQ) (GPI 15715; Guilford Pharmaceutical Inc., Baltimore, MD) is a water-soluble prodrug of propofol (PropofolGPI). This study aimed to explore the pharmacokinetics of AQ, PropofolGPI, and formate (a metabolite of AQ) and to compare them with the pharmacokinetics of propofol lipid emulsion (PropofolD).

METHODS

After ethics committee approval, 36 healthy volunteers were randomly allocated into six cohorts (male/female: 3/3) and given a single bolus of AQ (5, 10, 15, 20, 25, or 30 mg/kg). For comparison, an equipotent dose (as measured by the Bispectral Index) of PropofolD was given to the same subjects 1 week later. For both drugs, blood samples were collected (1-480 min) to analyze AQ, PropofolGPI, PropofolD, and formate concentrations. Noncompartmental pharmacokinetic analyses were performed for all analytes. A population compartmental model was developed for AQ and PropofolGPI using NONMEM. The models were evaluated using simulations and bootstraps.

RESULTS

The noncompartmental pharmacokinetic comparison revealed different dispositions of PropofolGPI and PropofolD. The maximum plasma concentration was lower for PropofolGPI than for PropofolD at equipotent doses, and apparent clearance and distribution volume were much higher for PropofolGPI than for PropofolD. Formate concentrations were similar when injecting both drugs and were not higher than baseline. Compartmental modeling revealed that the pharmacokinetic behavior of AQ and its liberated PropofolGPI was best described by a nonlinear, six-compartment model, composed of two three-compartment models connected to each other by hydrolysis of AQ to PropofolGPI.

CONCLUSIONS

PropofolGPI showed different noncompartmental pharmacokinetics from PropofolD, hereby revealing the influence of the formulation. The combined model for AQ and PropofolGPI was best modeled by a nonlinear, six-compartment model.

Propofol-Associated Hypertriglyceridemia and Pancreatitis in the Intensive Care Unit: An Analysis of Frequency and Risk Factors

STUDY OBJECTIVES

To characterize the frequency, severity, risk factors, and clinician response to propofol-associated hypertriglyceridemia and hypertriglyceridemia-associated pancreatitis.

DESIGN

Retrospective analysis.

SETTING

Medical and surgical intensive care units.

PATIENTS

One hundred fifty-nine adult intensive care patients administered propofol for 24 hours or longer and who had at least one serum triglyceride concentration.

MEASUREMENTS AND MAIN RESULTS

Patient records were reviewed to identify the frequency of hypertriglyceridemia (serum triglyceride concentration > or = 400 mg/dl) and pancreatitis (amylase concentration > or = 125 IU/L, lipase concentration > or = 60 IU/L, and abdominal computed tomography scan or clinical examination findings consistent with pancreatitis). Of the 159 patients, 29 (18%) developed hypertriglyceridemia; six (21%) of the 29 had a serum triglyceride concentration of 1000 mg/dl or greater. The median maximum serum triglyceride concentration was 696 mg/dl (range 403-1737 mg/dl). At the time when hypertriglyceridemia was detected, the median infusion rate of propofol was 50 microg/kg/minute (range 5-110 microg/kg/min). The median time from the start of propofol therapy to identification of hypertriglyceridemia was 54 hours (range 14-319 hrs). Propofol was discontinued within 24 hours of detecting the hypertriglyceridemia 84% of the time. Compared with those who did not develop hypertriglyceridemia, patients who developed hypertriglyceridemia were older, had a longer intensive care unit stay, and received propofol for a longer duration; they were also more likely to be admitted to the medical versus the surgical intensive care unit. Pancreatitis developed in three (10%) of the 29 patients with hypertriglyceridemia.

CONCLUSION

Hypertriglyceridemia and hypertriglyceridemia-associated pancreatitis are often seen in intensive care patients receiving propofol. Serum triglyceride concentrations should be routinely monitored in these patients. In addition, alternative sedation strategies should be considered when hypertriglyceridemia is detected.

Tolerance and Withdrawal Issues with Sedation

The stay in an ICU is a complex mixture of providing optimal care while keeping the patient safe. Means of reducing the anxiety associated with the ICU stay include frequent reorientation and maintenance of patient comfort with sedation supplemented by analgesia as needed. The most common agents used to provide sedation include benzodiazepines, propofol, and the newer dexmedetomidine. Others include barbiturate agents, neuroleptics, clonidine, etomidate, ketamine, and supplemental opioid analgesics for pain control. A common complication of sedation is tolerance, which can lead to withdrawal if the sedation is discontinued hastily. This article evaluates the occurrence of tolerance and withdrawal in the most commonly used sedatives in critically ill patients.

Comparative study between propofol in a long-chain triglyceride and propofol in a medium/long-chain triglyceride during sedation with target-controlled infusion

This study was performed to compare the pharmacological characteristics of propofol in an emulsion of both medium- and long-chain triglycerides (MCT/LCT) with those of propofol in an LCT emulsion, by measuring the sedative level and the plasma concentration of propofol during sedation using a target-controlled infusion (TCI) technique. Forty ASA 1 or 2 adult patients who required spinal anaesthesia for surgery were enrolled in this study. The patients were divided into two groups: a propofol LCT group (n = 20) and a propofol MCT/LCT group (n = 20). Propofol was injected intravenously at target blood concentrations of 2.0, 3.0 and 4.0 microg x ml(-1). The bispectral (BIS) index was recorded, and arterial blood was drawn to measure the actual plasma concentrations of propofol at each predicted concentration. Propofol was assayed by high-performance liquid chromatography. Propofol MCT/LCT was associated with significantly less pain than propofol LCT (P < 0.05). There were no significant differences between the two groups in BIS index or in plasma concentration of propofol at each predicted concentration. Computer-generated TCI of propofol MCT/LCT during sedation is comparable with that of propofol LCT with respect to pharmacokinetics and pharmacodynamics. The formulation of MCT/LCT has a beneficial effect with respect to less pain on injection.

Inhibition of Persistent Sodium Current Fraction and Voltage-gated L-type Calcium Current by Propofol in Cortical Neurons: Implications for Its Antiepileptic Activity

PURPOSE

Although it is widely used in clinical practice, the mechanisms of action of 2,6-di-isopropylphenol (propofol) are not completely understood. We examined the electrophysiologic effects of propofol on an in vitro model of epileptic activity obtained from a slice preparation.

METHODS

The effects of propofol were tested both on membrane properties and on epileptiform events consisting of long-lasting, paroxysmal depolarization shifts (PDSs) induced by reducing the magnesium concentration from the solution and by adding bicuculline and 4-aminopyridine. These results were integrated with a patch-clamp analysis of Na(+) and high-voltage activated (HVA) calcium (Ca(2+)) currents from isolated cortical neurons.

RESULTS

In bicuculline, to avoid any interference by gamma-aminobutyric acid (GABA)-A receptors, propofol (3-100 microM) did not cause significant changes in the current-evoked, sodium (Na(+))-dependent action-potential discharge. However, propofol reduced both the duration and the number of spikes of PDSs recorded from cortical neurons. Interestingly, relatively low concentrations of propofol [half-maximal inhibitory concentration (IC(50)), 3.9 microM) consistently inhibited the "persistent" fraction of Na(+) currents, whereas even high doses (< or =300 microM) had negligible effects on the "fast" component of Na(+) currents. HVA Ca(2+) currents were significantly reduced by propofol, and the pharmacologic analysis of this effect showed that propofol selectively reduced L-type HVA Ca(2+) currents, without affecting N or P/Q-type channels.

CONCLUSIONS

These results suggest that propofol modulates neuronal excitability by selectively suppressing persistent Na(+) currents and L-type HVA Ca(2+) conductances in cortical neurons. These effects might cooperate with the opening of GABA-A-gated chloride channels, to achieve depression of cortical activity during both anesthesia and status epilepticus.

Propofol 6% as sedative in children under 2 years of age following major craniofacial surgery

BACKGROUND

After alarming reports concerning deaths after sedation with propofol, infusion of this drug was contraindicated by the US Food and Drug Administration in children <18 yr receiving intensive care. We describe our experiences with propofol 6%, a new formula, during postoperative sedation in non-ventilated children following craniofacial surgery.

METHODS

In a prospective cohort study, children admitted to the paediatric surgical intensive care unit following major craniofacial surgery were randomly allocated to sedation with propofol 6% or midazolam, if judged necessary on the basis of a COMFORT behaviour score. Exclusion criteria were respiratory infection, allergy for proteins, propofol or midazolam, hypertriglyceridaemia, familial hypercholesterolaemia or epilepsy. We assessed the safety of propofol 6% with triglycerides (TG) and creatine phosphokinase (CPK) levels, blood gases and physiological parameters. Efficacy was assessed using the COMFORT behaviour scale, Visual Analogue Scale and Bispectral Index monitor.

RESULTS

Twenty-two children were treated with propofol 6%, 23 were treated with midazolam and 10 other children did not need sedation. The median age was 10 (IQR 3-17) months in all groups. Median duration of infusion was 11 (range 6-18) h for propofol 6% and 14 (range 5-17) h for midazolam. TG levels remained normal and no metabolic acidosis or adverse events were observed during propofol or midazolam infusion. Four patients had increased CPK levels.

CONCLUSION

We did not encounter any problems using propofol 6% as a sedative in children with a median age of 10 (IQR 3-17) months, with dosages <4 mg kg(-1) h(-1) during a median period of 11 (range 6-18) h.

Propofol: a new treatment strategy for refractory migraine headache

Migraine headache remains a treatment dilemma in headache clinics, pain clinics, and emergency departments throughout the country. In the late nineties, investigators reported that a standard hypnotic anesthetic, propofol (2,6 di-isopropylphenol), dramatically improved pain scores of patients suffering from refractory migraine headaches. Case reports over the last few years have appeared in the medical literature describing the use of propofol for migraine treatment. Dosing regimens are not clear, and mechanisms of action to terminate or markedly curtail ongoing intractable headaches are not described. This case report, of two hospitalized patients with refractory migraine, increases the existing literature on the use of propofol therapy in migraine headache. In the first case, three different scenarios and dosages are described in the same patient. In the second case, the use of different dosages of propofol is described. A self-reported scale was employed by the patients to determine the efficacy of propofol therapy. In the first case, the patient's self-reported migraine score was an average of 100/100 and decreased to 10/100. In the second case, the patient's self-reported migraine score improved from 92/100 to 40/100. We propose that the improvements in the self-reported migraine score in both patients after propofol therapy may be due to GABAA agonist effects and cerebral vasoconstriction.

Survey of routines for sedation of patients on controlled ventilation in Nordic intensive care units

BACKGROUND

Sedation strategies and practice for patients on controlled ventilation is variable from place to place as well as over time. Less sedation results in shorter ventilation time and new ventilatory modes permit more awake patients. Previous works estimated sedative and analgesic use in Nordic ICUs some years ago, but current practice is not known. We therefore designed this study to describe pharmacological and practical routines for sedation of patients on controlled ventilation.

MATERIAL AND METHODS

We used an electronic questionnaire about characteristics of the participating ICUs and the routines for sedation of ventilator-treated patients, and secondly, an Internet-based 5-day registration on the use of drugs for sedation and analgesia.

RESULTS

Eighty-eight of 220 ICUs (36%) responded to the questionnaire and 47 out of these 88 units (53%) used a sedation scale. Written guidelines for sedation were used in 41% of the units. Both daily interruption of sedation infusions and guidelines for weaning from the ventilator were used in 15% of the units. Data on 202 patients (633 patient days) from 55 ICUs were reported. Among analgesics, fentanyl predominated (240/633 days), followed by ketobemidon (160/633 days) and morphine (115/633 days). Propofol and midazolam were the most commonly used agents for sedation (345 and 238/633 days, respectively).

CONCLUSION

Most units used a sedation scale, although other strategies to reduce the sedation level had not yet been fully introduced. Differences in pharmacological strategies were found between the Nordic countries, and some favourite drugs could be identified.

Clinical management of cardiogenic shock associated with prolonged propofol infusion

This case report details the development of cardiogenic shock after craniotomy in a patient sedated with a propofol infusion. The patient survived with the assistance of extracorporeal membrane oxygenation. A literature review summarizes the syndrome of cardiogenic shock associated with prolonged propofol infusion. This is the first report of survival in this syndrome resuiting from mechanical circulatory support.

The Effects of Propofol on Hypothalamic Paraventricular Nucleus Neurons in the Rat

The mechanism of hypotension induced by anesthetics is not completely understood. Because no electrophysiologic examination of the effects of propofol on the central nervous system has shown its involvement in the control of sympathetic and cardiovascular functions, we investigated the actions of propofol on rat hypothalamic paraventricular nucleus (PVN) neurons using the whole-cell mode of the patch-clamp technique in rat hypothalamic PVN slice preparations. Propofol induced Cl(-) currents at concentrations of 10(-5) and 10(-4) M, which were sensitive to picrotoxin and, to a lesser extent, to strychnine. Propofol (10(-6) M) enhanced gamma-aminobutyric acid(A) (GABA(A); 10(-6) M)-induced current synergistically. Moreover, propofol (10(-5) and 10(-4) M) significantly increased the decay time of evoked-inhibitory postsynaptic currents, which suggests a postsynaptic modulation of GABA(A) receptors. In addition, propofol (10(-5), 10(-4), and 2 x 10(-4) M) reversibly inhibited voltage-gated Ca(2+) currents. Taken together, these results suggest that propofol enhancement of GABA(A)-receptor mediated currents and inhibition of voltage-gated Ca(2+) currents at the central level, which is involved in the control of cardiovascular and sympathetic functions may be, at least in part, involved in general anesthetic-induced cardiovascular and sympathetic depression.

IMPLICATIONS

We investigated the actions of propofol on the rat hypothalamic paraventricular nucleus neurons, which are involved in the control of cardiovascular and sympathetic functions. The results suggest that propofol enhancement of gamma-aminobutyric acid(A)-receptor mediated currents and inhibition of voltage-gated Ca(2+) currents at the central level may be, at least in part, involved in general anesthetic-induced cardiovascular and sympathetic depression.

Short-term propofol infusion as an adjunct to extubation in burned children

Children who require intubation as a component of their burn management generally need heavy sedation, usually with a combination of opiate and benzodiazepine infusions with a target sensorium of light sleep. When extubation approaches, the need for sedation to prevent uncontrolled extubation can conflict with the desire to lighten sedation enough to ensure that airway protective reflexes are strong. The several hours' half-life of these medications can make this period of weaning challenging. Therefore, the hours preceding extubation are among the most difficult in which to ensure safe adequate sedation. The pharmacokinetics of propofol allow for the rapid emergence of a patient from deep sedation. We have had success with an extubation strategy using short-term propofol infusions in critically ill children. In this work, children were maintained on morphine and midazolam infusions per our unit protocol, escalating doses as required to maintain comfort. Approximately 8 hours before planned extubation, these infusions were decreased by approximately half and propofol infusion added to maintain a state of light sleep. Extubation was planned approximately 8 hours later to allow ample time for the chronically infused opiates and benzodiazepines to be metabolized down to the new steady-state level. Thirty minutes before planned extubation, propofol was stopped while morphine and midazolam infusions were maintained at the reduced level. When the children awakened from the propofol-induced state of light sleep, they were extubated while the reduced infusions of morphine and midazolam were maintained. These were subsequently weaned slowly, depending on the child's need for ongoing pain and anxiety medication, per our unit protocol to minimize the incidence of withdrawal symptoms. Data are shown in the text as mean +/- standard deviation. These 11 children (eight boys and three girls) had an average age of 6.6 +/- 5.6 years (range, 1.2-13 years), average weight of 36.9 +/- 28.7 kg (range, 9.3-95 kg), and burn size of 43 +/- 21.4% (range, 10-85%). Three children had sustained scald burns and eight had flame injuries with associated inhalation injury. They had been intubated for an average of 12.7 +/- 10.9 (range, 2-33 days). Morphine infusions immediately before the initiation of propofol averaged 0.26 +/- 0.31 mg/kg/hour (range, 0.04-1.29 mg/kg/hr) and midazolam averaged 0.15 +/- 0.16 mg/kg/hr (range, 0.06-0.65 mg/kg/hr). Morphine infusions after beginning propofol and at extubation averaged 0.16 +/- 0.16 (range, 0.04-0.65 mg/kg/hr) and midazolam averaged 0.09 +/- 0.08 mg/kg/hr (range, 0.02-0.32 mg/kg/hr). Propofol doses after initial titration during the first hour of infusion averaged 3.6 +/- 2.9 mg/kg/hr (range, 0.4-8.1 mg/kg/hr). Nine of the 11 children (82%) were successfully extubated on the first attempt. Two required reintubation for postextubation stridor 2 to 6 hours after extubation but were successfully extubated the next day after a short course of steroids, again using the same propofol technique. All were awake at extubation and went on to survive. Morphine and midazolam infusions were gradually weaned, and there were no withdrawal symptoms noted. Although prolonged (days) infusions of propofol have been associated with adverse cardiovascular complications in critically ill young children and should probably be avoided, short-term (in hours) use of the drug can facilitate smooth extubation.

Long-term sedation with propofol 60 mg ml(-1) vs. propofol 10 mg(-1) ml in critically ill, mechanically ventilated patients

BACKGROUND

Hypertriglyceridaemia is the main cause of therapeutic failure during propofol use in long-term sedated mechanically ventilated patients. Propofol 60 mg ml(-1) has been developed to reduce fat and volume load for the critically ill patient. The purpose of the study was to compare the effectiveness of sedation, achievability of effective concentrations and the effects on serum lipid concentrations of propofol 60 mg ml(-1) vs. propofol 10 mg ml(-1) for long-term sedation in critically ill patients.

METHODS

In this randomized, open, prospective study, 20 critically ill, mechanically ventilated patients who required sedation for a minimum of 48 h received propofol 60 mg ml(-1) or propofol 10 mg ml(-1) in doses as required during 2-5 days.

RESULTS

No differences between propofol 60 mg ml(-1) and propofol 10 mg ml(-1) were observed in the effectiveness of sedation using the Ramsay Sedation score and the Subjective Sedation score, nor in relation to the propofol concentrations. Between the two groups, there were no significant differences in the daily propofol dose, number of daily infusion rate adjustments or need for additional sedatives. Mean serum triglyceride concentrations were higher in the propofol 10 mg ml(-1) group compared with the propofol 60 mg ml(-1) group [5.26 (3.19) vs. 3.22 (2.05) mmol l(-1), P > 0.05][mean (SD)]. Patients in the propofol 10 mg ml(-1) group received more fat from the propofol infusion than from the propofol 60 mg ml(-1) group [53.2 (29.6) vs. 10.0 (4.7) % compared with fat from nutrition, respectively]. A significant relationship was observed between the daily total fat dose and the serum triglyceride concentration (r2 = 0.32, P < 0.001), whereas there was no significant correlation between the daily propofol dose and the serum triglyceride concentration.

CONCLUSION

Propofol 60 mg ml(-1) is a useful alternative to propofol 10 mg ml(-1) for the long-term sedation of critically ill patients. Sedation with propofol 60 mg ml(-1) reduces fat and volume load by 83%, which reduces the risk of hypertriglyceridaemia.

The Pharmacodynamic Effects of a Lower-Lipid Emulsion of Propofol: A Comparison with the Standard Propofol Emulsion

Using a randomized, double-blind protocol design, we compared a new lower-lipid emulsion of propofol (Ampofol) containing propofol 1%, soybean oil 5%, and egg lecithin 0.6% with the most commonly used formulation of propofol (Diprivan) with respect to onset of action and recovery profiles, as well as intraoperative efficacy, when administered for induction and maintenance of general anesthesia as part of a "balanced" anesthetic technique in 63 healthy outpatients. Anesthesia was induced with sufentanil 0.1 microg/kg (or fentanyl 1 microg/kg) and propofol 2 mg/kg IV and maintained with a variable-rate propofol infusion, 120-200 microg x kg(-1) x min(-1). Onset times to loss of the eyelash reflex and dropping a syringe were recorded. Severity of pain on injection, speed of induction, intraoperative hemodynamic variables, and electroencephalographic bispectral index values were assessed. Recovery times to opening eyes and orientation were noted. The results demonstrated that there were no significant differences between Ampofol and Diprivan with respect to onset times, speed of induction, anesthetic dose requirements, bispectral index values, hemodynamic variables, recovery variables, or patient satisfaction. However, the incidence of pain on injection was more frequent in the Ampofol group (26% versus 6%, P < 0.05). We conclude that Ampofol is equipotent to Diprivan with respect to its anesthetic properties but was associated with a more frequent incidence of mild pain on injection.

IMPLICATIONS

The pharmacodynamic profile of a lower-lipid containing emulsion of propofol (Ampofol) was compared with Diprivan when administered for induction and maintenance of general anesthesia. This preliminary study demonstrated that the two formulations of propofol were equivalent with respect to their induction and maintenance properties. However, Ampofol was associated with a more frequent incidence of pain on injection.

Propofol sedation by emergency physicians for elective pediatric outpatient procedures

STUDY OBJECTIVE

We describe the efficacy of propofol sedation administered by pediatric emergency physicians to facilitate painful outpatient procedures.

METHODS

By using a protocol for patients receiving propofol sedation in an emergency department-affiliated short-stay unit, a prospective, consecutive case series was performed from January to September 2000. Patients were prescheduled, underwent a medical evaluation, and met fasting requirements. A sedation team was present throughout the procedure. All patients received supplemental oxygen. Sedation depth and vital signs were monitored while propofol was manually titrated to the desired level of sedation.

RESULTS

There were 291 separate sedation events in 87 patients. No patient had more than 1 sedation event per day. Median patient age was 6 years; 57% were male patients and 72% were oncology patients. Many children required more than 1 procedure per encounter. Most commonly performed procedures included lumbar puncture (43%), intrathecal chemotherapy administration (31%), bone marrow aspiration (19%), and bone biopsy (3%). Median total propofol dose was 3.5 mg/kg. Median systolic and diastolic blood pressures were lowered 22 mm Hg (range 0 to 65 mm Hg) and 21 mm Hg (range 0 to 62 mm Hg), respectively. Partial airway obstruction requiring brief jaw-thrust maneuver was noted for 4% of patient sedations, whereas transient apnea requiring bag-valve-mask ventilation occurred in 1% of patient sedations. All procedures were successfully completed. Median procedure duration was 13 minutes, median sedation duration was 22 minutes, and median total time in the short stay unit was 40 minutes.

CONCLUSION

Propofol sedation administered by emergency physicians safely facilitated short painful procedures in children under conditions studied, with rapid recovery.

Pharmacological characteristics and side effects of a new galenic formulation of propofol without soyabean oil*

We compared the pharmacokinetics, pharmacodynamics and safety profile of a new galenic formulation of propofol (AM149 1%), which does not contain soyabean oil, with a standard formulation of propofol (Disoprivan 1%). In a randomised, double-blind, cross-over study, 30 healthy volunteers received a single intravenous bolus injection of 2.5 mg.kg-1 propofol. Plasma propofol levels were measured for 48 h following drug administration and evaluated according to a three-compartment model. The pharmacodynamic parameters assessed included induction and emergence times, respiratory and cardiovascular effects, and pain on injection. Patients were monitored for side effects over 48 h. Owing to a high incidence of thrombophlebitis, the study was terminated prematurely and only the data of the two parallel treatment groups (15 patients in each group) were analysed. Plasma concentrations did not differ significantly between the two formulations. Anaesthesia induction and emergence times, respiratory and cardiovascular variables showed no significant differences between the two treatment groups. Pain on injection (80 vs. 20%, p < 0.01) and thrombophlebitis (93.3 vs. 6.6%, p < 0.001) occurred more frequently with AM149 than with Disoprivan. Although both formulations had similar pharmacokinetic and pharmacodynamic profiles the new formulation is not suitable for clinical use due to the high incidence of thrombophlebitis produced.

Propofol withdrawal syndrome in an adult patient with thermal injury

A 48-year-old man with a history of ethanol abuse and bipolar disease fell asleep while smoking in an intoxicated state. The patient received a 30% total body surface area burn involving his face and upper torso that resulted in an inhalation injury. Several attempts at weaning from mechanical ventilation failed due to his extreme agitation, which was unresponsive to benzodiazepines, opiates, and antipsychotic agents. Propofol therapy was begun in combination with valproic acid, fluoxetine, and risperidone to assist in the treatment of his severe agitation associated with the bipolar disease, inhibiting ventilatory weaning. Repeated attempts to discontinue propofol were associated with withdrawal symptoms such as severe agitation, tremors, tachycardia, tachypnea, and hyperpyrexia. His symptoms resolved only after each time the propofol infusion was restarted. The patient received propofol for 95 days for management of his agitation before dying from refractory septic shock and multiple organ failure.

Novel water soluble 2,6-dimethoxyphenyl ester derivatives with intravenous anaesthetic activity

A number of water soluble bis-amino-2,6-dimethoxyphenyl ester derivatives were found to exhibit improved anaesthetic activity in mice relative to propofol 1. Of the analogues disclosed, 44 was further profiled in rodents and found to be a superior agent to propofol for the induction and maintenance of anaesthesia.

Pharmacokinetics and pharmacodynamics of a single bolus of propofol 2% in healthy volunteers

This study was undertaken to assess the bioequivalence between a new formulation of propofol 2% and the commercially available product Diprivan. Secondary objectives were to compare the times to onset of and emergence from hypnosis, the hemodynamic effects, and the safety profiles. Twelve healthy male volunteers were included in a randomized crossover study. Subjects were administered a 2-mg/kg single bolus injection of each formulation separated by a 7- to 10-day washout period. Plasma propofol was determined by reversed-phase liquid chromatography with fluorescence detection. Eleven subjects completed the study, and both formulations were considered bioequivalent. There were no serious or severe adverse events. The concentration-time profiles of all the subjects could adequately be described using a three-compartment model. The mean times to cessation of counting out loud (17 vs. 18 s) and to eye opening (245 vs. 244 s) were not statistically different between treatment groups. Moreover, they seem to show some degree of pharmacodynamic bioequivalence, although a higher number of subjects are necessary to unequivocally demonstrate it.

Rett syndrome: investigation of nine patients, including PET scan

BACKGROUND

We describe nine females with Rett Syndrome (RS), aged 14 to 26 years. All had had developmental delay before the end of their first year and had subsequently regressed to profound dementia with apraxia, ataxia, irregular respirations and often also seizures.

METHODS

The Revised Gesell developmental assessment and Alpern-Boll Developmental Profile were used in modified form. Volumetric measurements of basal ganglia using MRI were compared with the findings in nine age-matched volunteer females. Positron emission scans with [18F]-6-fluorodopa and [11C]-raclopride were performed under light anesthesia with intravenous Propofol, and the findings were compared with those in healthy control girls. Bidirectional sequencing of the coding regions of the MECP2 gene was investigated in blood samples for mutational analyses.

RESULTS

The RS females functioned at a mental age level ranging from about 4 to 15 months. The scores correlated with height, weight and head circumference. Magnetic resonance scans of basal ganglia showed a significant reduction in the size of the caudate heads and thalami in the Rett cases. Positron emission scans demonstrated that the mean uptake of fluorodopa in RS was reduced by 13.1% in caudate and by 12.5% in putamen as compared to the controls, while dopamine D2 receptor binding was increased significantly by 9.7% in caudate and 9.6% in putamen. Mutations in the coding regions of the MECP2 gene were present in all nine patients. No significant correlation between type and location of mutation and volumetric changes or isotope uptake was demonstrable.

CONCLUSIONS

Our findings suggest a mild presynaptic deficit of nigrostriatal activity in Rett syndrome.