Metabolic, biochemical and haemodynamic effects of infusion of propofol for long-term sedation of children undergoing intensive care

Pediatric Neurocritical Care: Maximizing Neurodevelopmental Outcomes Through Specialty Care

The field of pediatric neurocritical care (PNCC) has expanded and evolved over the last three decades. As mortality from pediatric critical care illness has declined, morbidity from neurodevelopmental disorders has expanded. PNCC clinicians have adopted a multidisciplinary approach to rapidly identify neurological injury, implement neuroprotective therapies, minimize secondary neurological insults, and establish transitions of care, all with the goal of improving neurocognitive outcomes for their patients. Although there are many aspects of PNCC and adult neurocritical care (NCC) medicine that are similar, elemental difference between adult and pediatric medicine has contributed to a divergent evolution of the respective fields. The low incidence of pediatric critical care illness, the heterogeneity of neurological insults, and the limited availability of resources all shape the need for a PNCC clinical care model that is distinct from the established paradigm adopted by the adult neurocritical care community at large. Considerations of neurodevelopment are fundamental in pediatrics. When neurological injury occurs in a child, the neurodevelopmental stage at the time of insult alters the impact of the neurological disease. Developmental variables contribute to a range of outcomes for seemingly similar injuries. Despite the relative infancy of the field of PNCC, early reports have shown that implementation of a specialized PNCC service elevates the quality and safety of care, promotes education and communication, and improves outcomes for children with acute neurological injuries. The multidisciplinary approach of PNCC clinicians and researchers also promotes a culture that emphasizes the importance of quality improvement and education initiatives, as well as development of and adherence to evidence-based guidelines and family-focused care models.

Adherence to a Pediatric Continuous Infusion Propofol Policy for Sedation in Mechanically Ventilated Patients: Opportunities for Change and Improvement

OBJECTIVE

To evaluate adherence to an institutional continuous infusion propofol policy for sedation in mechanically ventilated patients, investigate the rate of propofol-related infusion syndrome (PRIS), and explore areas of improvement to enhance policy compliance and safety.

METHODS

This was a single center, retrospective chart review of patients admitted to a pediatric or cardiac intensive care unit within a large free-standing quaternary care pediatric hospital who received continuous propofol for non-procedural continuous sedation for at least 6 hours between 2014 and 2019. Propofol exposure (dose and duration), laboratory data, and hemodynamic outcomes of patients were evaluated.

RESULTS

A total of 104 patients (108 admissions and 133 treatment courses) met inclusion criteria. Policy adherence to propofol dosing and duration limitations were 70% (93/133 courses) and 68% (91/133 courses), respectively. Adherence to all elements of laboratory and hemodynamic monitoring was 23%. Hypotension and bradycardia were common among patients during propofol treatment courses. Except for hypertriglyceridemia, no significant difference in specific laboratory values were detected between patients exposed to greater than 66 mcg/kg/min (4 mg/kg/hr), compared with those exposed to less than 66 mcg/kg/min of propofol. Patients receiving therapy for longer than 48 hours had the highest rates of laboratory values associated with PRIS. No patient in the study cohort met full criteria for PRIS.

CONCLUSIONS

Adherence to elements of an institutional propofol policy was variable. Improvements in policy adherence may be enhanced by updating policy features, leveraging the electronic medical record order-set, and gaining consensus among key stakeholders.

2022 Society of Critical Care Medicine Clinical Practice Guidelines on Prevention and Management of Pain, Agitation, Neuromuscular Blockade, and Delirium in Critically Ill Pediatric Patients With Consideration of the ICU Environment and Early Mobility

RATIONALE

A guideline that both evaluates current practice and provides recommendations to address sedation, pain, and delirium management with regard for neuromuscular blockade and withdrawal is not currently available.

OBJECTIVE

To develop comprehensive clinical practice guidelines for critically ill infants and children, with specific attention to seven domains of care including pain, sedation/agitation, iatrogenic withdrawal, neuromuscular blockade, delirium, PICU environment, and early mobility.

DESIGN

The Society of Critical Care Medicine Pediatric Pain, Agitation, Neuromuscular Blockade, and Delirium in critically ill pediatric patients with consideration of the PICU Environment and Early Mobility Guideline Taskforce was comprised of 29 national experts who collaborated from 2009 to 2021 via teleconference and/or e-mail at least monthly for planning, literature review, and guideline development, revision, and approval. The full taskforce gathered annually in-person during the Society of Critical Care Medicine Congress for progress reports and further strategizing with the final face-to-face meeting occurring in February 2020. Throughout this process, the Society of Critical Care Medicine standard operating procedures Manual for Guidelines development was adhered to.

METHODS

Taskforce content experts separated into subgroups addressing pain/analgesia, sedation, tolerance/iatrogenic withdrawal, neuromuscular blockade, delirium, PICU environment (family presence and sleep hygiene), and early mobility. Subgroups created descriptive and actionable Population, Intervention, Comparison, and Outcome questions. An experienced medical information specialist developed search strategies to identify relevant literature between January 1990 and January 2020. Subgroups reviewed literature, determined quality of evidence, and formulated recommendations classified as "strong" with "we recommend" or "conditional" with "we suggest." Good practice statements were used when indirect evidence supported benefit with no or minimal risk. Evidence gaps were noted. Initial recommendations were reviewed by each subgroup and revised as deemed necessary prior to being disseminated for voting by the full taskforce. Individuals who had an overt or potential conflict of interest abstained from relevant votes. Expert opinion alone was not used in substitution for a lack of evidence.

RESULTS

The Pediatric Pain, Agitation, Neuromuscular Blockade, and Delirium in critically ill pediatric patients with consideration of the PICU Environment and Early Mobility taskforce issued 44 recommendations (14 strong and 30 conditional) and five good practice statements.

CONCLUSIONS

The current guidelines represent a comprehensive list of practical clinical recommendations for the assessment, prevention, and management of key aspects for the comprehensive critical care of infants and children. Main areas of focus included 1) need for the routine monitoring of pain, agitation, withdrawal, and delirium using validated tools, 2) enhanced use of protocolized sedation and analgesia, and 3) recognition of the importance of nonpharmacologic interventions for enhancing patient comfort and comprehensive care provision.

Effect of multimodal intervention on postoperative nausea and vomiting in patients undergoing gynecological laparoscopy

OBJECTIVE

Postoperative nausea and vomiting (PONV) is a common complication in patients undergoing gynecological laparoscopic surgery, and achieving good results is difficult with a single antiemetic method. This study investigated whether multimodal intervention can reduce PONV in patients undergoing gynecological laparoscopic surgery.

METHODS

A total of 153 patients who underwent gynecological laparoscopic surgery were randomized into the control group and multimodal group. Patients in the multimodal group received dexmedetomidine 1 µg/kg intravenously 15 minutes before induction of anesthesia. A bilateral transversus abdominis plane block was performed with 0.375% ropivacaine 30 mL after induction of anesthesia. Scores of postoperative nausea and vomiting, the visual analog scale, and the Bruggemann comfort scale (BCS) were assessed 24 hours postoperatively.

RESULTS

Nausea and vomiting scores were significantly lower at 2, 6, and 24 hours in the multimodal group compared with the control group. BCS scores were significantly higher at 0 to 24 hours in the multimodal group compared with the control group.

CONCLUSIONS

Multimodal intervention improves PONV and increases patients' comfort. The multimodal approach can also enhance recovery after gynecological laparoscopic surgery.

Effects of propofol in lipid-based emulsion and in microemulsion on the incidence of endothelial lesion in rabbits

PURPOSE

To compare the incidence of endothelial injury after single-dose or continuous propofol infusion in conventional lipid-based emulsion (LE) versus microemulsion (ME).

METHODS

Forty-two rabbits (2.5-4.5 Kg) were randomly allocated into seven groups of six animals each: SHAM- surgical treatment alone; Bolus Control Group - 3 mL-intravenous (IV) bolus of saline; Continuous Infusion Control Group - 3 mL- IV bolus of saline followed by a continuous infusion of 0.2 ml/kg/min for 60 min; Bolus LE Propofol Group - IV bolus of LE propofol (3 mg/kg); Bolus ME Propofol Group - IV ME propofol bolus (3 mg/kg); Continuous LE Propofol Group - IV LE propofol bolus (3 mg/kg) followed by a continuous infusion of 0.2 ml/kg/min for 60 min; Continuous ME Propofol Group - IV ME propofol bolus (3 mg/kg) followed by a continuous infusion of 0.2 ml/kg/min for 60 min.

RESULTS

There were no statistically significant differences between the studied groups in blood pressure, in central venous pressure and in the biochemical profile. No significant differences were found in inflammatory mediators and in tissue analysis between the two emulsions.

CONCLUSION

Microemulsion and lipid-based emulsion propofol had similar inflammatory, biochemical and microscopy profiles. Thus, microemulsion propofol can be used as an alternative to lipid-based emulsion propofol.

Use of propofol in pediatric intensive care units: a national survey in Germany

OBJECTIVE

Propofol is not licensed for sedation in pediatric intensive care medicine mainly due to the risk of propofol infusion syndrome. Nevertheless, it is applied by many pediatric intensive care units. The aim of this national survey was to asses the current use of propofol in pediatric intensive care units in Germany.

DESIGN

We performed a nationwide survey. The questionnaire assessed the intensive care unit type, patient numbers, dosing, duration, age and time limits, indications, side effects, and institutional protocols for propofol usage.

SETTING

Pediatric intensive care units in Germany.

SUBJECTS

Questionnaire about routine use of propofol sent to 214 pediatric departments.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

One hundred ninety-four questionnaires (90.7%) were returned, ten had to be censored. The final analysis comprised 184 questionnaires (134 pediatric/neonatal intensive care units, 28 pediatric intensive care units, 22 neonatal intensive care units). Seventy-nine percent of intensive care units (n = 145 of 184) used propofol in children under the age of 16 yrs. Of these, 98% were for bolus application (n = 142 of 145), 78% for infusion ≥3 hrs (n = 113 of 145), and 33% for infusion >3 hrs (n = 48 of 145). A lower age limit was applied by 52% (n = 75 of 145) and a dose limit by 51% (n = 74 of 145). The median dose limit was 4 mg/kg/hr; 48% (n = 70 of 145) used 3 mg/kg/hr or less. A time limit was applied by 98% (n = 46 of 47), 70% (n = 33 of 47) used it for ≤24 hrs, and 30% (n = 15 of 47) for >24 hrs. MAIN INDICATIONS FOR PROPOFOL APPLICATION WERE: difficult sedation (44%), postoperative ventilation (43%), and difficult extubation (30%). Seven cases of propofol infusion syndrome were reported by seven centers.

CONCLUSIONS

This study shows that propofol is used off-license by many pediatric intensive care units in Ge. The majority of users has adopted tightly controlled regimens for propofol sedation, and limits the dose to ≤3-4 mg/kg/hr and the maximum application time to 24-48 hrs.

Efficacy of sedation regimens to facilitate mechanical ventilation in the pediatric intensive care unit: a systematic review

OBJECTIVE

Children admitted to pediatric intensive care units (PICUs) often receive sedatives to facilitate mechanical ventilation. However, despite their widespread use, data supporting appropriate dosing, safety, and optimal regimens for sedation during mechanical ventilation are lacking. Therefore, we conducted a systematic review of published data regarding efficacy of sedation to facilitate mechanical ventilation in PICU patients. Our primary objective was to identify and evaluate the quality of evidence supporting sedatives used in PICUs for this purpose.

DATA SOURCES

We searched MEDLINE, EMBASE, and The Cochrane Registry of Clinical Trials from 1966 to June 2008 to identify published articles evaluating sedation regimens to facilitate mechanical ventilation in PICU patients.

STUDY SELECTION

We included only those studies of intubated PICU or pediatric cardiac intensive care unit patients receiving pharmacologic agents to facilitate mechanical ventilation that reported quality of sedation as an outcome.

DATA EXTRACTION

We analyzed studies separately for study type and by agents being studied. Studies were appraised using criteria of particular importance for reviews evaluating sedatives.

DATA SYNTHESIS

Our search strategy yielded 39 studies, including 3 randomized trials, 15 cohort studies, and 21 cases series or reports. The 39 studies evaluated a total of 39 different sedation regimens, with 21 different scoring systems, in a total of 901 PICU/cardiac intensive care unit patients ranging in age from 3 days to 19 years old. Most of the studies were small (<30 patients), and only four studies compared one or more agents to another. Few studies thoroughly evaluated drug safety, and only one study met all quality criteria.

CONCLUSIONS

Despite the widespread use of sedatives to facilitate mechanical ventilation in the PICU, we found that high-quality evidence to guide clinical practice is still limited. Pediatric randomized, controlled trials with reproducible methods and assessment of drug safety are needed.

Stewart's physicochemical approach in neurosurgical patients with hyperchloremic metabolic acidosis during propofol anesthesia

There is both in vitro and clinical evidence that high-dose propofol can inhibit mitochondrial respiration, resulting in metabolic acidosis. The purpose of this study was to evaluate the effects of propofol anesthesia on the acid-base status in neurosurgical patients with large amount of normal saline administration. Thirty patients undergoing clipping of cerebral aneurysm were randomly assigned to receive propofol (n=15) or isoflurane (n=15). Propofol dose (mean+/-standard error) infused for maintenance was 5.7+/-0.2 mg/kg/h in propofol group. Acid-base parameters such as PaCO2, pH, serum bicarbonate concentration, standard base excess, serum electrolyte concentration, total protein, albumin, lactate, and phosphate were measured before and 4 hours after the induction of anesthesia, and after surgery. The apparent strong ion difference (SIDa), the effective SID (SIDe), and the amount of weak plasma acid were calculated using the Stewart equation. There were no significant differences in pH, PaCO2, bicarbonate, and lactate between 2 groups throughout the whole investigation period. After surgery, standard base excess significantly decreased in both groups without intergroup difference. SIDa and SIDe significantly decreased in both groups, and lactate and strong ion gap significantly increased after surgery in propofol group, but there were no significant differences between 2 groups. Both propofol and isoflurane were associated with hyperchloremic metabolic acidosis in neurosurgical patients with large amount of normal saline administration. The acid-base balance between the 2 anesthetics was similar using Stewart's physicochemical approach.

Propofol infusion syndrome

In this article, we present the case of a previously well 31-year-old man who sustained a mild closed-head injury following a motor vehicle incident and was admitted to the intensive care unit of a major teaching hospital. The man was sedated using propofol combined with midazolam and morphine as the main sedating agent. The propofol was started and continued at high dose for 8 days, over which time the patient deteriorated with metabolic acidosis, rhabdomyolysis, renal impairment, and cardiovascular collapse and then died. A forensic autopsy was performed. The only positive autopsy finding was a cardiac perivascular and interstitial infiltrate of mononuclear cells. The clinical and pathological features in the case presented were consistent with propofol infusion syndrome. No other cause for the above features was found and the cause of death was given as death related to propofol infusion syndrome.Propofol infusion syndrome is characterized by metabolic acidosis, rhadbomyolysis, and myocardial failure, sometimes with renal failure and hyperkalemia occurring in the setting of high-dose propofol treatment. The syndrome has become increasingly recognized in recent years. The syndrome is of importance to forensic pathologists who may see cases referred to their practice because of the unexplained deterioration of a patient in the intensive care unit and the association with head-injured patients and the pediatric population. Death associated with propofol infusion has not been described in the forensic literature.

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-Infusionssyndrom

Propofol infusion syndrome has not only been observed in patients undergoing long-term sedation with propofol, but also during propofol anesthesia lasting 5 h. It has been assumed that the pathophysiologic cause is propofol's impairment of oxidation of fatty acid chains and inhibition of oxidative phosphorylation in the mitochondria, leading to lactate acidosis and muscular necrosis. It has been postulated that propofol might act as a trigger substrate in the presence of priming factors. Severe diseases in which the patient has been exposed to high catecholamine and cortisol levels have been identified as trigger substrates. Once the development of propofol infusion syndrome is suspected, propofol infusion has to be stopped immediately and specific therapeutic measures initiated, including cardiocirculatory stabilization and correction of metabolic acidosis. To increase elimination of propofol and its potential toxic metabolites, hemodialysis or hemofiltration are recommended. Due to its possible fatal side effects, the use of propofol for long-term sedation in critically ill patients should be reconsidered. In cases of unexplained lactate acidosis occurring during continuous propofol infusion, propofol infusion syndrome must be taken into consideration.

Accidental tenfold overdose of propofol in a 6-month old infant undergoing elective craniosynostosis repair

We report a 6-month-old male infant undergoing elective craniosynostosis repair who accidentally received a tenfold dose of propofol over a 4-h operative period. Myocardial dysfunction was observed after nearly 3 h of infusion; this could not solely be explained by the propofol overdose.

Major abdominal surgery of the neonate: anaesthetic considerations

The anaesthetic handling of neonates scheduled for major abdominal surgical procedures is one of the most demanding tasks that can confront an anaesthesiologist. This chapter will review the specific physiological characteristics of the newborn with relevance to anaesthesia and will also provide robust guidelines for the anaesthetic handling of the most frequent diagnoses that need major abdominal surgery during the neonatal period.

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.

Death after re-exposure to propofol in a 3-year-old child: a case report

This case report discusses the cause of death in a 3-year-old child who survived a high dose (20 mg x kg-1 x h-1) of propofol, infused over a period of 15 h, following which the patient developed a combined respiratory and metabolic acidosis, the oxygenation remaining normal. Bronchospasm was assumed to be the cause of hypercapnia. At this time the doctors in charge did not think of a possible side-effect of propofol. The administration of propofol was interrupted, the patient recovered within 13 h from the acidosis, woke up and required further sedation. A supposedly entirely safe infusion of 4 mg x kg-1 x h-1 propofol, as recommended in the literature for up to 48 h, was administered. After only 8 h intractable bradycardic dysrhythmias occurred. Although pharmacokinetic studies have pointed to a possible accumulation of propofol during continuous infusions, an interruption of an infusion for several hours has been considered sufficient for practically total clearance of the drug from the body. In this case re-exposure with a recommended dose of propofol was accompanied by bradycardia and dysrythmias that proved to be resistant to therapy and led to fatal cardiac insufficiency with a functioning artificial pacemaker in place. This case raises concerns about the safety of long-term infusions of propofol for sedation in children and possibly also in adults.

Toxicity of intravenous anaesthetics

Intravenous anaesthetic agents are generally remarkably safe. However, it is clear that propofol infusion syndrome is a real, albeit rare, entity. This often lethal syndrome of metabolic acidosis, acute cardiomyopathy and skeletal myopathy is strongly associated with infusions of propofol at rates of 5 mg/kg/hour and greater for more than 48 hours. There is evidence to support the hypothesis that the syndrome is caused by the failure of free fatty acid metabolism due to inhibition of free fatty acid entry into the mitochondria and also specific sites in the mitochondrial respiratory chain. The syndrome therefore mimics the mitochondrial myopathies. Midazolam causes seizure-like activity in very-low-birthweight premature infants requiring the drug prior to tracheal intubation or during prolonged positive pressure ventilation. This can be successfully reversed with the specific benzodiazepine antagonist flumazenil. Midazolam can also cause paradoxical reactions, including increased agitation, poor co-operation and aggressive or violent behaviour, which has been successfully managed with flumazenil.

Propofol anaesthesia and metabolic acidosis in children

BACKGROUND

We aimed to investigate the effect of propofol infusion anaesthesia on acid-base status and liver and myocardial enzyme levels of children during short-term anaesthesia.

METHODS

Thirty-six children, aged 3-12 years, were randomized into two groups. In group P (n = 18), induction and maintenance were performed with propofol, 3 mg x kg-1 and 20, 15 and 10 mg x kg-1 x h-1, respectively. In group H (n = 18) following induction with 5 mg x kg-1 thiopenthal, anaesthesia was maintained with 2-3% halothane. Blood samples were obtained following anaesthesia induction and 30, 60 and 120 min after discontinuation of anaesthesia.

RESULTS

There was no difference in lactate dehydrogenase, myocardial creatininephosphokinase, aspartate aminotransferase, alanine aminotransferase and cholesterol levels between and within the groups. All postoperative triglyceride levels were higher and pH levels were lower in group P than group H (P < 0.05) and there was no difference within the groups.

CONCLUSIONS

In these healthy patients, short-term use of propofol did not result in significant acidaemia, nor alterations in hepatic or myocardial enzyme levels.

Use of propofol infusion in Australian and New Zealand paediatric intensive care units

Despite the risk of propofol infusion syndrome, a rare but often fatal complication of propofol infusion in ventilated children and possibly adults, propofol infusion remains in use in paediatric intensive care units (PICU). This questionnaire study surveys the current pattern of use of this sedative infusion in Australian and New Zealand PICUs. Thirty-three of the 45 paediatric intensive care physicians surveyed (73%), from 12 of the 13 intensive care units, returned completed questionnaires. The majority of practitioners (82%) use propofol infusion in children in PICU, the main indication being for short-term sedation in children requiring procedures. 39% of respondents consider propofol infusion useful in ventilated children requiring longer-term sedation. 67% of paediatric intensivists use maximum infusion doses that may be considered dangerously high (> or = 10 mg/kg/h). Nineteen per cent use propofol infusion for prolonged periods (> 72 hours). A smaller proportion (15%) of respondents indicate that they may use both higher doses and prolonged periods of infusion, a practice likely to lead to a greater chance of serious adverse events. Knowledge of local protocols for the use of propofol infusion is associated with a significantly greater level of monitoring for possible adverse events. We suggest that national guidelines for the use of propofol infusion in children should be developed. These should include clear indications and contraindications to its use, a maximum dose rate and maximum period of infusion, with a ceiling placed on the cumulative dose given and clearly stated minimum monitoring requirements.

Pharmacokinetics and effects of propofol 6% for short-term sedation in paediatric patients following cardiac surgery

AIMS

This paper describes the pharmacokinetics and effects of propofol in short-term sedated paediatric patients.

METHODS

Six mechanically ventilated children aged 1-5 years received a 6 h continuous infusion of propofol 6% at the rate of 2 or 3 mg kg-1 h-1 for sedation following cardiac surgery. A total of seven arterial blood samples was collected at various time points during and after the infusion in each patient. Pharmacokinetic modelling was performed using NONMEM. Effects were assessed on the basis of the Ramsay sedation score as well as a subjective sedation scale.

RESULTS

The data were best described by a two-compartment pharmacokinetic model. In the model, body weight was a significant covariate for clearance. Pharmacokinetic parameters in the weight-proportional model were clearance (CL) = 35 ml kg-1 min-1, volume of central compartment (V1) = 12 l, intercompartmental clearance (Q) = 0.35 l min-1 and volume of peripheral compartment (V2) = 24 l. The interindividual variabilities for these parameters were 8%, < 1%, 11% and 35%, respectively. Compared with the population pharmacokinetics in adults following cardiac surgery and when normalized for body weight, statistically significant differences were observed the parameters CL and V1 (35 vs 29 ml kg-1 min-1 and 0.78 vs 0.26 l kg-1P < 0.05), whereas the values for Q and V2 were similar (23 vs 18 ml kg-1 min-1 and 1.6 vs 1.8 l kg-1, P > 0.05). In children, the percentage of adequately sedated patients was similar compared with adults (50% vs 67%) despite considerably higher propofol concentrations (1.3 +/- 0.10 vs 0.51 +/- 0.035 mg l-1, mean +/- s.e. mean), suggesting a lower pharmacodynamic sensitivity to propofol in children.

CONCLUSIONS

In children aged 1-5 years, a pharmacokinetic model for propofol was described using sparse data. In contrast to adults, body weight was a significant covariate for clearance in children. The model may serve as a useful basis to study the role of covariates in the pharmacokinetics and pharmacodynamics of propofol in paediatric patients of different ages.

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.

Treatment of pain in acutely burned children

The child with burns suffers severe pain at the time of the burn and during subsequent treatment and rehabilitation. Pain has adverse physiological and emotional effects, and research suggests that pain management is an important factor in better outcomes. There is increasing understanding of the private experience of pain, and how children benefit from honest preparation for procedures. Developmentally appropriate and culturally sensitive pain assessment, pain relief, and reevaluation have improved, becoming essential in treatment. Pharmacological treatment is primary, strengthened by new concepts from neurobiology, clinical science, and the introduction of more effective drugs with fewer adverse side effects and less toxicity. Empirical evaluation of various hypnotic, cognitive, behavioral, and sensory treatment methods is advancing. Multidisciplinary assessment helps to integrate psychological and pharmacological pain-relieving interventions to reduce emotional and mental stress, and family stress as well. Optimal care encourages burn teams to integrate pain guidelines into protocols and critical pathways for improved care.

Anaesthesia for procedures in the intensive care unit

Taking in charge severely ill patients in the intensive care environment to manage complex procedures is a performance requiring highly specific knowledge. Close collaboration between anaesthetists and intensive care specialists is likely to improve the safety and quality of medical care. Three forms of anaesthetic care should be considered in clinical practice: sedation and analgesia; monitored anaesthetic care; and general anaesthesia or conduction block anaesthesia. Even in the field of sedation and analgesia, the anaesthesiologist can offer expertise on new anaesthetic techniques like: the most recent concepts of balanced anaesthesia in terms of pharmacokinetics and dynamics, favouring the use of short-acting agents and of sedative-opioid combinations. New modes of administration and monitoring intravenous anaesthesia have been developed, with potential application in the intensive care unit. These include the use of target-controlled administration of intravenous drugs, and of electroencephalographic signals to monitor the level of sedation.

Early tracheal extubation after paediatric cardiac surgery: the use of propofol to supplement low-dose opioid anaesthesia

BACKGROUND

After institutional approval and parental consent, 103 children, aged 6 months to 18 years, who were undergoing repair of simple and complex congenital heart lesions using cardiopulmonary bypass (CPB) were studied and compared with a group of 135 children who had undergone similar surgery in our institution in the year before.

METHODS

Anaesthesia for study patients included fentanyl (< 20 microg.kg-1) and isoflurane. Infusions of propofol (median infusion rate 70 microg.kg-1.min-1) and morphine (median infusion rate 20 microg.kg-1.h-1) were started after weaning from CPB and continued postoperatively. Preestablished criteria were used in the intensive care unit (ICU) to assess readiness for tracheal extubation.

RESULTS

Median time from admission to ICU to tracheal extubation was 5 h. Fifty-six children were extubated within 6 h and 73 within 9 h of ICU admission. Mean ICU stay for study patients was 1.7 days [95% confidence interval (CI) 1.2-2.2] and 2.6 days (95% CI 2.3-2.9) in the comparison group (P<0.005).

CONCLUSIONS

We found the propofol regimen to be satisfactory with a shorted ICU stay for these patients.

Sedation-analgesia in the pediatric intensive care unit

The provision of sedation and analgesia is an integral aspect of the care of PICU patients. A careful systems approach to the provision of sedation and analgesia can minimize complications and maximize benefit to patients. Vigilance in monitoring and adherence to published guidelines are important for safety. Physicians must define the goals in clearly devising a plan and tailor the prescription to those goals rather than use a regimented protocol for all patients.

The influence of hypoxia and hyperoxia on the kinetics of propofol emulsion

PURPOSE

To study the effect of hypoxia and hyperoxia on the pharmacokinetics of propofol emulsion, hepatic blood flow and arterial ketone body ratio in the rabbit.

METHODS

Twenty four male rabbits were anesthetized with isoflurane (1.5-2%) in oxygen. After the surgical procedure, isoflurane administration was discontinued and intravenous propofol infusion (30 mg x kg(-1) x hr(-1)) was started. The infusion rate of propofol was maintained throughout the study. After an initial 90 min period of propofol infusion, rabbits were randomly allocated to one of three groups: hypoxia (F(I)O2 = 0.1), normoxia (F(I)O2 = 0.21), and hyperoxia (F(I)O2 = 1.0). Propofol infusion was continued under the allocated F(I)O2 for 60 min. Propofol concentrations in arterial blood, total body clearance of propofol, hepatic blood flow and arterial ketone body ratio were measured.

RESULTS

The mean arterial propofol concentration at the end of infusion was higher in the hypoxia group (15.2 +/- 2.8 microg x mL(-1), mean +/- SD) than in the normoxia (7.4 +/- 1.7) and hyperoxia (8.0 +/- 1.9) groups (P < 0.05). Total body clearance of propofol, hepatic blood flow and arterial ketone body ratio were all reduced in the hypoxia group (P < 0.05). Total ketone body concentration in arterial blood increased in the hyperoxia group (P < 0.01).

CONCLUSION

Hypoxia produced an accumulation of propofol in blood and reduced propofol clearance. These changes could result from decreased hepatic blood flow and low cellular energy charge in the liver. Hyperoxia, on the other hand, increased total ketone body in arterial blood.

Propofol infusion syndrome in children

The use of propofol infusions to sedate children in intensive care units has decreased after reports of deaths from myocardial failure. More recently it has been suggested that propofol might have been prematurely condemned. Information about 18 children who had received propofol infusions and suffered serious unwanted effects was used to define their common features. Three of the deaths occurred in one intensive care unit where propofol infusions had been used between 1987 and 1993. During this period 44 children with respiratory tract infections had been admitted to this unit and sedated for at least 48 h. Nine had received long-term (> 48 h), high-dose (> 4 mg.kg-1.h-1) propofol infusions and three had developed progressive myocardial failure and died. There was a significant association between receiving a long-term, high-dose propofol infusion and developing progressive myocardial failure (Fisher's Exact Test, two-tailed hypothesis, P = 0.0128) although a causative relationship could not be proved.