Propofol-infusion syndrome in children

Optimizing Sedative Dose in Preterm Infants Undergoing Treatment for Respiratory Distress Syndrome

The Intubation-Surfactant-Extubation (INSURE) procedure is used worldwide to treat pre-term newborn infants suffering from respiratory distress syndrome, which is caused by an insufficient amount of the chemical surfactant in the lungs. With INSURE, the infant is intubated, surfactant is administered via the tube to the trachea, and at completion the infant is extubated. This improves the infant's ability to breathe and thus decreases the risk of long term neurological or motor disabilities. To perform the intubation safely, the newborn infant first must be sedated. Despite extensive experience with INSURE, there is no consensus on what sedative dose is best. This paper describes a Bayesian sequentially adaptive design for a multi-institution clinical trial to optimize the sedative dose given to pre-term infants undergoing the INSURE procedure. The design is based on three clinical outcomes, two efficacy and one adverse, using elicited numerical utilities of the eight possible elementary outcomes. A flexible Bayesian parametric trivariate dose-outcome model is assumed, with the prior derived from elicited mean outcome probabilities. Doses are chosen adaptively for successive cohorts of infants using posterior mean utilities, subject to safety and efficacy constraints. A computer simulation study of the design is presented.

The use of propofol sedation in a paediatric intensive care unit

BACKGROUND

The aim of this study was to prospectively evaluate and report the experience of the use of continuous intravenous propofol sedation in a paediatric intensive care unit (PICU).

METHODS

All children younger than 16 years who were admitted to the PICU at a University Hospital for slightly more than a year and received propofol infusion were included prospectively and data were recorded before and within 6 h after completion of the propofol infusion.

RESULTS

A total of 174 out of 955 children (18·2%) received propofol infusion for sedation. The median age was 2 years 10 months (range: 2 months to 16 years), duration of propofol infusion 13 h (range: 1·6-179 h) and dose of propofol 2·9 mg/kg/h (range: 0·3-6·5 mg/kg/h). No one developed signs of the propofol infusion syndrome (PRIS). Neither dose >3 mg/kg/h, duration of infusion >48 h nor both were found to be related to adverse metabolic derangements or circulatory failure. Eight children increased their lactate concentration ≥1·8 mmol/L during propofol infusion. All had a favourable outcome. One child who had received propofol infusion for 10 h died, but this occurred 14 h after the infusion ceased and was without doubt attributed to a multiple organ failure not related to the propofol infusion.

CONCLUSION

Propofol infusion was used in this population at low risk of PRIS with no metabolic or circulatory adverse effects. These findings indicate that the occurrence of adverse effects may not be directly related to dose or duration of infusion, but emphasizes the risk that sporadic factors may be involved, such as genetic mutations. Guidelines are presented.

Organ toxicity and mortality in propofol-sedated rabbits under prolonged mechanical ventilation

BACKGROUND

Prolonged administration of propofol at large doses has been implicated in propofol infusion syndrome in intensive care unit patients. In this study we investigated organ toxicity and mortality of propofol sedation at large doses in prolonged mechanically ventilated rabbits and determined the role of propofol's lipid vehicle.

METHODS

Eighteen healthy male rabbits were endotracheally intubated and sedated with propofol 2% (Group P), sevoflurane (Group S) or sevoflurane while receiving Intralipid 10% (Group SI). Sedation lasted 48 h or until death (Group P) or the maximum surviving period of Group P (Groups S and SI). The initial propofol infusion rate (20 mg x kg(-1) x h(-1)) or sevoflurane concentration (1.5%) was adjusted, if needed, to maintain a standard level of sedation. Blood biochemical analysis was performed in serial blood samples and histologic examination in the heart, lungs, liver, gallbladder, kidneys, urinary bladder, and quadriceps femoris muscle at autopsy.

RESULTS

The mortality rate was 100% (surviving period, 26-38 h) for Group P, whereas 0% for Groups S and SI. The initial propofol infusion rate had to be increased up to 65.7 +/- 4.6 mg x kg(-1) x h(-1) and sevoflurane concentration up to 4%. Serum liver function indices, lipids and creatine kinase were significantly increased (P < 0.05) in Groups P and SI and lactate was increased only in Group P, whereas amylase was increased in all groups. In Group P, histologic examination revealed myocarditis, pulmonary edema with interstitial pneumonia, hepatitis, steatosis, and focal liver necrosis, cholangitis, gallbladder necrosis, acute tubular necrosis of the kidneys, focal loss of the urinary bladder epithelium, and rhabdomyolysis of skeletal muscles; in Group S, low-grade bronchitis and incipient inflammation of the liver and the kidneys; and in Group SI, low-grade bronchitis, liver steatosis and hepatitis, and incipient inflammation of the gallbladder, kidneys, and urinary bladder.

CONCLUSIONS

Continuous infusion of 2% propofol at large doses for the sedation of rabbits undergoing prolonged mechanical ventilation induced fatal multiorgan dysfunction syndrome similar to the propofol infusion syndrome seen in humans. Our novel findings including lung, liver, gallbladder, and urinary bladder injury were also noted. The role of propofol's lipid vehicle in the manifestation of the syndrome was minor. Sevoflurane proved to be a safe alternative medication for prolonged sedation.

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.

The pathophysiology of propofol infusion syndrome: a simple name for a complex syndrome

Propofol infusion syndrome (PRIS) is a rare and often fatal syndrome described in critically ill children undergoing long-term propofol infusion at high doses. Recently several cases have been reported in adults, too. The main features of the syndrome consist of cardiac failure, rhabdomyolysis, severe metabolic acidosis and renal failure. To date 21 paediatric cases and 14 adult cases have been described. These latter were mostly patients with acute neurological illnesses or acute inflammatory diseases complicated by severe infections or even sepsis, and receiving catecholamines and/or steroids in addition to propofol. Central nervous system activation with production of catecholamines and glucocorticoids, and systemic inflammation with cytokine production are priming factors for cardiac and peripheral muscle dysfunction. High-dose propofol, but also supportive treatments with catecholamines and corticosteroids, act as triggering factors. At the subcellular level, propofol impairs free fatty acid utilisation and mitochondrial activity. Imbalance between energy demand and utilisation is a key pathogenetic mechanism, which may lead to cardiac and peripheral muscle necrosis. Propofol infusion syndrome is multifactorial, and propofol, particularly when combined with catecholamines and/or steroids, acts as a triggering factor. The syndrome can be lethal and we suggest caution when using prolonged (>48 h) propofol sedation at doses higher than 5 mg/kg per h, particularly in patients with acute neurological or inflammatory illnesses. In these cases, alternative sedative agents should be considered. If unsuitable, strict monitoring of signs of myocytolysis is advisable.

The propofol infusion syndrome in infants and children: can we predict the risk?

Propofol has been an immensely successful anaesthetic induction agent but there is an increasing number of reports of serious complications when it has been used as an infusion to provide sedation for prolonged periods. The first reports involved children who died from intractable myocardial failure preceded by a metabolic acidosis, lipaemic plasma, fatty infiltration of the liver and evidence of muscle damage. As more cases have been reported the association between propofol and the syndrome has become more certain. Recently adult cases have appeared and a metabolic explanation has been suggested. The syndrome has a high mortality and the only effective treatment appears to be dialysis.