A case of convulsion after propofol anaesthesia

Tolerance and Withdrawal Issues with Sedatives in the Intensive Care Unit

Prolonged use of sedative medications continues to be a concern for critical care practitioners, with potential adverse effects including tolerance and withdrawal. The amount of sedatives required in critically ill patients can be lessened and tolerance delayed with the use of pain and/or sedation scales to reach the desired effect. The current recommendation for prolonged sedation is to wean patients from the medications over several days to reduce the risk of drug withdrawal. It is important to identify patients at risk for iatrogenic withdrawal and create a treatment strategy.

Propofol in the treatment of refractory status epilepticus

OBJECTIVES

To study prospectively the effects of propofol anesthesia on seizure control, hemodynamics and course of intensive care in patients with refractory status epilepticus.

DESIGN AND SETTING

Prospective observational study in the general intensive care unit in a tertiary university hospital.

PATIENTS

Ten patients with refractory status epilepticus.

INTERVENTIONS

Patients received propofol anesthesia aiming to burst suppression EEG pattern for 12 h.

MEASUREMENTS AND RESULTS

Dose of propofol, quality of burst suppression EEG, hemodynamics and the course of intensive care were recorded. Clinical and electrophysiological seizures terminated quickly, but maintaining burst suppression EEG pattern required incremental doses of propofol. Despite high doses of propofol, recovery from anesthesia was fast.

CONCLUSIONS

High doses of propofol are needed in the treatment of refractory status epilepticus. The maintenance of continuous-burst suppression is difficult, and vigilant titrating of dosage of propofol is necessary under continuous EEG monitoring.

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.

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.

Activation of interictal spiking in mesiotemporal lobe epilepsy by propofol-induced sleep

The objective of this study was to test whether low-dose propofol increases the number of interictal spikes in patients with mesiotemporal lobe epilepsy, and to determine whether this is the result of intrinsic properties and is restricted to the primary epileptogenic focus. Controlled infusion of propofol in step-up/-down target concentrations of 0, 0.3, 0.6, and 0.8 mg/L was administered to 10 patients during a 3.5-hour daytime EEG registration. The number of spikes were counted and related to propofol concentration and sleep level. Results were compared with a spontaneous, nocturnal first sleep cycle in 9 of 10 patients. All patients entered nonrapid eye movement 1 sleep during propofol administration, and 8 reached nonrapid eye movement 2 sleep. In 7 patients who showed spikes, spikes were related to sleep (P < 0.05) and not to increasing (P = 0.1) or decreasing (P = 0.5) propofol concentration. Six of nine patients showed more spikes during spontaneous (nocturnal) sleep than during propofol-induced sleep. Contralateral spiking was not suppressed selectively. Low-dose propofol is a safe means of increasing spiking in these patients because it induces sleep. There were no signs of an intrinsic epileptogenicity of propofol or a selective effect on ipsilateral spikes. Controlled sleep induction will increase the yield of interictal spikes during short interictal recordings such as in magnetoencephalography.

Propofol sedation produces dose-dependent suppression of lidocaine-induced seizures in rats

The association of propofol with excitatory motor activity, such as myoclonic jerking and opisthotonus, in humans and in animals suggests that it may aggravate clinical seizure activity in some circumstances, although evidence suggests that under other circumstances, propofol inhibits seizure activity. In the current study, we assessed the effect of sedating doses of propofol on lidocaine-induced seizure activity in spontaneously breathing rats receiving no other anesthetics. Adult Sprague-Dawley male rats, 300-400 g, were divided into a control group and three experimental groups representing three graded levels of propofol sedation. The control rats then received a lidocaine infusion at the rate of 150 mg x kg(-1) x h(-1), resulting in a slow, progressive increase in systemic lidocaine concentrations. At the onset of electroencephalographic (EEG) seizure activity, arterial lidocaine concentrations were obtained. The treated rats received propofol according to three different dose schedules: Dose 1 = 10 mg x kg(-1) x h(-1) after a 2.5-mg/kg bolus; Dose 2 = 20 mg x kg(-1) x h(-1) after a 5-mg/kg bolus; Dose 3 = 40 mg x kg(-1) x h(-1) after a 10-mg/kg bolus. After 30 min, a steady level of sedation, dependent on the dose of propofol, was achieved. The lidocaine infusion was then started, and systemic lidocaine levels were obtained at the onset of EEG seizure activity. The lidocaine was continued until the onset of death by cardiac arrest. Plasma lidocaine was measured by gas chromatography. Analysis of variance and Dunnett's t-test were used for comparisons with the control values. Continuous propofol sedation increased the seizure dose of lidocaine from 37.7 +/- 3.5 mg/kg (mean +/- SEM) to 52.5 +/- 2.6 mg/kg (Dose 1, P < 0.05) and 67.9 +/- 8.6 mg/kg (Dose 2, P < 0.05), and completely abolished lidocaine seizures at Dose 3. The lethal dose of lidocaine, 89.4 +/- 10.5 mg/kg control versus 108.7 +/- 10.3 mg/kg (Dose 1), 98.3 +/- 10.1 mg/kg (Dose 2), and 93.5 +/- 10.4 mg/kg (Dose 3) did not differ among groups. The lidocaine levels at seizure threshold were increased in the propofol-treated rats: 16.9 +/- 0.5 microg/mL control versus 19.2 +/- 0.7 microg/mL (Dose 1, P = not significant) and 23.7 +/- 1.8 microg/mL (Dose 2, P < 0.05). Continuous propofol sedation in spontaneously breathing rats receiving no other anesthetics exerts a protective effect against lidocaine-induced seizures in a monotonic, dose-dependent fashion. The cardiac arrest dose of lidocaine is unaffected by propofol under these conditions.

IMPLICATIONS

The i.v. anesthetic drug propofol, given to rats to produce sedation, was found to suppress seizure activity caused by overdosage of the local anesthetic lidocaine.

Propofol: pro- or anticonvulsant?

The pro- or anticonvulsant properties of propofol remain a matter of controversy. Although numerous case reports describe the appearance of abnormal movements, posturing and seizure-like activity related to the use of propofol, systematic studies in both humans and animals strongly suggest that it possesses antiepileptic properties. Propofol consistently reduces the seizure duration during electroconvulsive therapy, its use has been successful in controlling refractory status epilepticus and in animals it offers a strong protection against lignocaine- or pentylene-tetrazol-induced epilepsy. The beneficial effects of propofol may be related to its uniform depressant action on the central nervous system, to a potentialization of GABA-mediated pre- and postsynaptic inhibition, and by decreasing the release of excitatory transmitters, glutamate and aspartate.

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.

Comparison of total intravenous, balanced inhalational and combined intravenous-inhalational anaesthesia for tympanoplasty, septorhinoplasty and adenotonsillectomy

Two hundred and thirty-five consecutive Saudi patients aged between two and fifty-three years undergoing elective tympanoplasty (n = 32), septorhinoplasty (n = 68) or adenotonsillectomy (n = 135) were studied. They were randomized to receive either a total intravenous anaesthetic (10 ears, 23 noses, 44 throats) consisting of propofol for induction of anaesthesia followed by a propofol infusion, a combined intravenous-inhalational anaesthetic (11 ears, 22 noses, 46 throats) consisting of the above with isoflurane in oxygen-enriched air, or a balanced inhalational anaesthetic (11 ears, 23 noses, 45 throats) consisting of thiopentone for induction of anaesthesia and oxygen in nitrous oxide with isoflurane for maintenance. During tympanoplasty, all three anaesthetic techniques produced stable heart rates and arterial pressures. During septorhinoplasty, blood pressure rose in patients who received total intravenous anaesthesia, while combined and balanced techniques produced haemodynamic stability. During adenotonsillectomy, total intravenous anaesthesia produced a rise in both heart rate and blood pressure, the combined technique produced a rise in heart rate alone while balanced anaesthesia produced haemodynamic stability. Postoperatively, vomiting, pain scores and analgesic requirements were similar following all three types of anaesthetic within each surgical site subgroup. Our findings support the choice of balanced inhalational anaesthesia for all three types of ENT surgery and, where cost and facilities permit, total intravenous anaesthesia for tympanoplasty and combined intravenous-inhalational anaesthesia for septorhinoplasty.

Effects of propofol and thiopentone on picrotoxin convulsive threshold in the rabbit

The purpose of the present study was to examine the effect of intravenous administration of propofol and thiopentone on picrotoxin-induced seizures using the picrotoxin convulsive threshold test in the rabbit. Neither propofol nor thiopentone at a dose of 1.25 mg/kg had any significant effect on picrotoxin seizure threshold. However, at higher doses (2.5, 5, 10 mg/kg) both propofol and thiopentone produced a significant and dose-dependent increase in the picrotoxin convulsive threshold. These findings suggest that propofol is an effective anticonvulsant against picrotoxin-induced seizures in the rabbit.

Comparison of the effects of propofol and thiopental on the pattern of maximal electroshock seizures in the rat

The anticonvulsant effects of propofol and thiopental (thiopentone) were determined by measuring the durations of the various phases of maximal electroshock seizures in the rat. Five min. after intraperitoneal administration of subanaesthetic (6.25, 12.5 and 25 mg/kg) and 50 mg/kg doses of propofol, the 2 highest doses abolished both tonic hindlimb extensor phases (full and partial extension) in all rats and decreased the duration of the total tonic phases of the seizure. Although the lowest dose produced no effect, the 12.5 mg/kg dose decreased the duration of both the full and partial tonic extensor phases and increased the duration of tonic flexion, showing that even this low dose had anticonvulsant activity. Subanesthetic doses of thiopental (5, 10 and 20 mg/kg) produced similar changes in the maximal electroshock seizures except that even the lowest dose also significantly decreased the duration of total extension and total tonus. Postseizure depression was prolonged only by the highest dose of propofol. Thus, even low doses of either propofol or thiopental, that produced only minimal behavioural effects, had marked anticonvulsant effects against electrically induced convulsions in the rat. No evidence of enhanced convulsant maximal electroshock seizures patterns was observed at any dose.

Drug interactions with intravenous and local anaesthetics

Relatively few clinically significant drug interactions with anaesthetics have been documented in the literature. The following should be stressed since these interactions are not readily predictable or are potentially fatal. Pethidine should never be administered to patients who have received monamine oxidase inhibiting drugs within the last fortnight, since a fatal hyperpyrexia and/or hypertension may result. Thiopentone induction seems to make the heart more susceptible to arrhythmias caused by adrenergic drugs, and may cause severe arterial hypotension in patients treated with diazoxide. Midazolam orally should possibly be avoided as premedication in patients treated with erythromycin since anaesthetic concentrations of midazolam may result. Patients for whom bupivacaine analgesia is planned could preferentially be premedicated with other drugs than diazepam, which causes the serum level of bupivacaine to increase. Bradycardia and hypotension not attributable to sympathetic blockade have been reported following bupivacaine extradurally in verapamil-treated patients. Sulfonamides and the ester group of local anaesthetics, such as prilocaine in combination, may result in severe methaemoglobinaemia in infants. Epinephrine added to local anaesthetics may cause local vasodilation if administered to patients concurrently being treated with cyclic antidepressants, and the combination imposes the risk of severe hypertension and arrhythmias.

Convulsive thresholds in mice during the recovery phase from anaesthesia induced by propofol, thiopentone, methohexitone and etomidate

1. Convulsive thresholds were measured with intravenous pentylenetetrazol in mice during the recovery phase after intravenous anaesthetic doses of propofol (10 and 20 mg kg-1), thiopentone (30 mg kg-1), methohexitone (10 mg kg-1), and etomidate 3 mg kg-1). 2. The convulsive threshold rose after each agent, indicating an anticonvulsant action for all the drugs tested; this declined to control values with initial half times of: 1.56 min (propofol 10 mg kg-1); 1.03 min (propofol 20 mg kg-1): 1.02 min (methohexitone); 3.35 min (etomidate); 13.7 min (thiopentone). 3. At no time during the recovery phase of any agent did the convulsive threshold fall below control values, which might indicate an epileptogenic effect of the drug. 4. The threshold was depressed below control values by intravenous administration of Ro 15-4513, a partial inverse agonist at the benzodiazepine receptor, thus indicating the ability of this pentylenetetrazol test to demonstrate a proconvulsant effect. 5. We conclude that the abnormal movements or convulsions associated with recovery from anaesthesia with short-acting intravenous anaesthetics may not be the result of an intrinsic proconvulsant action of the drugs.

Comparison of propofol and thiopentone as anaesthetic agents for electroconvulsive therapy

Propofol and thiopentone were compared as anaesthetic agents for electroconvulsive therapy in 31 patients on four occasions in a repeated measure crossover study. Discomfort on injection was significantly more common with propofol (51.6% of anaesthetics) compared to thiopentone (1.6% of anaesthetics). The duration of seizure was shorter with propofol in both treatments but there was significant drug-time interaction. Propofol gave a milder tonus and clonus during seizure when both treatments were considered together. The increase in systolic and diastolic arterial pressures and heart rate after treatment were significantly higher with thiopentone. Apnoea was significantly longer with propofol. The times to sitting up unaided and opening the eyes on command were the same for both drugs. The ability to walk 10 m 20 minutes after anaesthesia was significantly better with propofol (p less than 0.0001).

Opisthotonus and other unusual neurological sequelae after outpatient anaesthesia

Four patients who developed unusual neurological sequelae after outpatient anaesthesia are described. Propofol is strongly implicated as the cause. All four patients were female with no previous history of psychiatric disorder or neurological disease, unpremedicated, and had procedures of duration less than 20 minutes. Hyperreflexia and hypertonicity were present postoperatively and the reactions appeared to be triggered by an external stimulus. Three patients were examined by a neurologist and had a normal electroencephalograph. Two patients were on the same operating list; quality control was carried out on the anaesthetic agents used, and blood samples sent for toxicology showed no abnormalities. Mechanisms underlying these reactions are discussed.