Current controversies in paediatric intensive care

Current Controversies in Paediatric Intensive Care

N. S. Morton

There is controversy about how intensive care for children should be organised. It is clear that paediatric intensive care training and service provision in the United Kingdom are not organised properly. There are too many small units and many children are managed in adult units. Concentration of the service in larger centres is beneficial both in terms of improved outcome and costs. Centralisation of paediatric intensive care

means that the transport of critically ill children should be undertaken by expert teams based upon each large centre. Training for medical and nursing staff in paediatric intensive care and in paediatric resuscitation should be based upon the large units which should be inspected and, if suitable, be recognised by the Colleges as being capable of training future consultants. Whether such units should be funded supraregionally or by funds moving with the patient is controversial. One worry is that the latter method may discourage referrals. However, unnecessary referrals may be minimised with district

units having to define more carefully their criteria for referral. In this regard, a formal assessment of illness severity and prognosis could be used to help with decision making. Controversial aspects of clinical management of children in intensive care include: sedation techniques; steroid therapy; topical antiviral therapy; alternatives to conventional respiratory and circulatory support; the underuse of analgesia for painful procedures; measures to conserve blood and use of invasive monitoring. A scientific

approach to these interventions needs to be adopted if paediatric intensive care is to progress as a specialty.

Provision of paediatric intensive care Organisation

A recent editorial highlighted the problems in the United Kingdom where paediatric intensive care is fragmented into too many small units and where many children are still looked after in adult intensive care units. ’

N. S. Morton MBChB FRCA, Consultant in Paediatric Anaesthe- sia and Intensive Care, Royal Hospital for Sick Children, Glasgow

G3 SSJ, Scotland.

There is compelling evidence from a carefully conducted American study that the outcome for the sickest children is better if they are transferred to and managed in large tertiary paediatric referral centres.’ Units caring for large numbers of critically ill children gain and maintain expertise which is otherwise dissi- pated.2.“*4 Centralisation of intensive care provision is accepted for adults5.” and for neonates7.8*9 so why not for infants and children? Many children are still looked after in adult ICUs, a situation which was

196 CURRENT ANAESTHESIA AND CRITICAL CARE

rejected in Australia ten years ago. “’ Many clinicians are not prepared to accept that their results with ill children are not as good as the large centres and are reluctant to recruit help. The recent National Health Service reforms bring a financial factor into the decision which may encourage reluctance to refer. Shann’s suggestion of central funding for a dozen large PICUs in the UK’ is timely and carries with it powerful messages. Interspecialty cooperation must be improved and the concept of shared care and responsibility must be accepted between referring clinicians, paediatricians and intensive care staff. The staffing, management, arrangements for referral and transfer of critically ill children have to be decided upon. Training programmes for medical and nursing staff have to be established if the standards drawn up by the Paediatric Intensive Care Society are to be met and maintained. ’ ’

Stafing

Adequate staffing of paediatric intensive care units is costly and requires a minimum of 15 designated sessions shared among 3 to 5 consultants to provide 24 hour, 7 day per week cover.6”’ Relatively senior intermediate medical staff and a suitable skill mix of nursing staff who are trained in paediatric intensive care are required. Consultant medical staff may be drawn from the disciplines of paediatric anaesthesia, paediatric medicine or paediatric surgery provided they have received adequate training in paediatric intensive care. Trainees may also come from these specialties and should be attached to the PICU for a minimum of 6 months. Trainees in accident and emergency medicine and adult intensive care may also benefit from attachment to the PICU. Although some feel that full time intensivists are needed’ there are advantages for consultants and trainees in main- taining contact with their base specialty.6 This can help to maintain skills in, for example, airway and vascular access. Advances in the base specialty can be brought into paediatric intensive care practice. Some also argue that contact with adult medicine is of great mutual benefit in fostering new ideas and links between the Intensive Care Society and the Paedia- tric Intensive Care Society in the UK are to be encouraged.

Training

At present in the United Kingdom, there is no formal training structure for the emerging specialty of paediatric intensive care. In Canada, the United States, Australia and some parts of Europe, training programmes are well established. An interdisciplinary working party with representation from the specialties of paediatrics, anaesthesia and surgery is trying to address this issue at present. The Colleges are responsible for training and an intercollegiate board will need to agree what constitutes suitable

training. The implementation of the Calman report will give trainees the opportunity to specialise during their training programme and it will become increas- ingly important that training centres for paediatric intensive care are identified. Traditionally, trainees have gone abroad to gain experience in such centres as Toronto or Melbourne. Although no single unit in the United Kingdom has the caseload of these centres, adequate training could be provided in units admitting at least 350 patients per year, provided a suitable case mix was available. The large centres would also be the logical bases for teaching paediatric intensive care nursing and paediatric resuscitation.

Funding

The NHS reforms may encourage smaller units to try to cope with critically ill children to avoid the expense of referring such patients. A recent documentary’2 has drawn public attention to this dilemma. Indeed it is probably the case that at present, many children who require intensive care are not receiving it.’ This assertion was based on a calculation of the total number of children managed annually in PICUs and adult ICUs in Britain which was half that expected in Australia and the USA.’ Supraregional funding, with health authorities only allowing intensive care of children in recognised PICUs, is a possible solution. An overall increase in resources is required in addition to the redistribution of resources currently used in managing a few children per year on multiple sites. Criteria for PICU referral will have to be clarified to encourage early transfer of children who need intensive care.

Severity scoring and outcome prediction

Scoring systems in paediatric intensive care can be used to measure illness severity, to assess the need for and efficacy of therapy, to determine prognosis and to predict outcome. Such information may be used to select patients for intensive care or, more contentiou- sly, in making decisions to withhold or withdraw intensive care. Efficiency, quality assurance and the performance of institutions can be assessed. The Paediatric Risk of Mortality (PRISM) score13 is now used widely and, although developed in the USA, has recently been validated in the United Kingdom.‘4*‘5 Sensitivity (correct prediction of death) and speci- ficity (correct prediction of survival) were compar- able with the original American validation data. However, deaths after cardiac surgery, early deaths (<24h in PICU) and late deaths (>4 days in PICU) were not predicted reliably. Survival in infants tends to be underestimated. Interestingly, a simplified score based on just five variables (systolic blood pressure, Glasgow coma scale, carbon dioxide tension, serum bicarbonate and serum calcium) per- formed as well as the full score. I4 PRISM score data has been used to argue the case for centralisation of

CURRENT CONTROVERSIES IN PAEDIATRIC INTENSIVE CARE 197

PICU services* and as part of cost containment’” and efficiencyI programmes. In the latter study, daily PRISM scoring was used to determine PICU discharge criteria. The main problem with PRISM scoring is the time and effort required to collect the data reliably15 and simpler prognostic scoring systems may be more useful in specific diseases. For example, in meningococcal disease the PRISM score performs well’s but scores based on readily accessible clinical findings’9*20 and haematological datals2’ may be simpler to apply, particularly for district hospitals to help them decide whom to refer for intensive care.

Transport of critically ill children

Centralisation of paediatric intensive care means that more critically ill children will need to be transported. The principles of assessment, stabilisation and moni- tored transfer are well established in adult intensive care practice but are not always adhered to in paediatrics. The availability of suitably qualified accompanying personnel is often a problem but this can be solved if a team travels out from the paediatric intensive care centre taking portable equipment and using the quickest available mode of transport.22,23 The response time of such teams depends on geogra- phy, weather and the availability of staff so the team cannot act as a primary resuscitation service. This responsibility must rest with the referring hospital who must ensure that their staff are trained in paediatric resuscitation. Courses are now being run in the United Kingdom to train personnel in basic and advanced paediatric life support.24 Correctly managed transfer does not result in a deterioration in the patient’s condition. 22 Outcome for the sickest children is better if they are transported to and treated in tertiary centres.2

Sedation in paediatric intensive care

The recent controversy surrounding the use of propofol for sedation in paediatric intensive care has highlighted the need for research in this field.25 The pharmaceutical industry is reluctant to support trials and very few sedatives have product licences covering their use for intensive care sedation of children. The pharmacokinetics and dynamics of many sedatives have not been studied in critically ill children.2h Whatever sedative regimen is used, it should be titrated to achieve the desired level of sedation which should be regularly assessed and recorded.27 Use of single agents can be problematic in children who often require large and increasing doses because of differences in kinetics and the development of acute tolerance. Disinhibition, agitation, involuntary movements, neurological sequelae and withdrawal syndromes may occur when single agents are used particularly if drugs without analgesic properties are used to sedate children in pain. This may lead, for example, to misinterpretation of involuntary

movements as ‘lightness’ and inapproporiate increase in dosage. The use of combinations of analgesics, sedatives and muscle relaxants in a balanced and complementary fashion is preferable to gain the benefits of each while minimising adverse effects. This can be illustrated for propofol, where concurrent administration of an infusion of morphine in children after cardiac surgery allowed a much lower infusion rate of propofol to be used (l-6 mg.kg-‘.h-‘) than that reported in the fatal cases (up to 13.6 mg.kg-‘.h-‘).28

Steroid therapy

The rationale for steroid therapy in critically ill children is still controversial. For some disorders, however, recent trials have clarified the role of steroids.

Bacterial meningitis

Steroid therapy has been used in children with bacterial meningitis to decrease the general inflammatory response, treat possible adrenal insufficiency (e.g. the Waterhouse Friderichsen syndrome in meningococcal disease), reduce cerebral oedema and reduce postmeningitic hearing loss. No improvement in mortality was found with steroid therapy in adults with septic shock or in children with meningitis, Cortisol levels are usually raised in meningococcal disease and adrenal insufficiency is very rare, even in those with adrenal haemorrhage documented by imaging. Dexamethasone has been shown to be better than methylprednisolone in reducing cytokine- induced increases in brain water content and intracranial pressure in experimental meningitis. It also reduces postmeningitic hearing loss in haemo- philus influenzae and streptococcus pneumoniae meningitis and is recommended for these indications by the American Academy of Pediatrics. The case has not been proven for meningococcal meningitis and at present steroids are not recommended for use routinely in meningococcal disease.29

Bronchopulmonary dysplasia (BPD)

BPD3” is a chronic disease which develops during the neonatal period in premature infants whose lungs have been damaged by a period of ventilator-induced barotrauma, oxygen toxicity and/or lower respiratory tract infection. Steroid therapy has been used with the aim of ameliorating or preventing severe BPD. Dexamethasone (0.5 mg.kgg’.day-’ for 7 days) has proven to be effective in improving pulmonary func- tion, decreasing the intensity and duration of ventilatory support and reducing indices of pulmonary inflammation. These beneficial effects may be medi- ated by effects on the pulmonary surfactant system. A reduction in mortality has not been demonstrated and


systemic steroids can have adverse effects. A nebu- liser system has been developed which may help to reduce systemic toxicity.

Prevention of postintubation tracheal oedema and postextubation stridor

Dexamethasone is often used empirically in paediatric practice to prevent tracheal oedema after airway instrumentation and prior to extubation to prevent postextubation stridor. This is particularly relevant after difficult or traumatic intubation, bronchoscopy or laryngeal or tracheal surgery. In children in intensive care who are intubated for a few days, use of dexamethasone need not be a routine but is often used for 6-12h prior to extubation. Some units use this approach only in those who have failed to extubate successfully at the first attempt. In a recent study3’ no difference was found in the incidence of postextubation stridor between dexamethasone and placebo treated children intubated for 3-4 days.

Croup

Croup is usually caused by a viral infection with respiratory syncytial virus, parainfluenza A or adeno- virus. Steroids have been advocated for this condition but many of the trials have not been well conducted. A single dose of dexamethasone given early may be beneficial in reducing the severity of retractions, stridor and need for nebulised adrenaline inha- lation3*

Ribavirin therapy for bronchiolitis due to RSV

Respiratory syncytial virus (RSV) is the most important respiratory pathogen in infants and children. About 10% of children who are hospitalised with this infection require intensive care and 10% of these severely affected children die. The risks are greatest for those under 6 weeks of age and for those with underlying lung disease, congenital heart disease or immune deficiency. Ribavirin has a structure very similar to the nucleoside guanosine and is active in preventing replication of a wide range of viruses by complex mechanisms. It is noteworthy that most viral multiplication has occurred by the time the clinical symptoms of RSV infection become apparent. Thus, if ribavirin is to be effective, it should be given as early as possible in the course of the disease.33 The American Academy of Pediatrics recommend ribavirin for the high risk groups noted above and those severely ill with impending respiratory failure. A group in Stanford developed a delivery system for use in intubated children with the aim of preventing precipitation of aerosolised particles in the ventilator circuitry with subsequent failure of the equipments4 They used this in a trial of ribavirin in ventilated infants and claimed to show significant decreases in the duration of mechanical ventilation, oxygen

therapy and hospital stay with a resultant cost sav- ing. 35 The main criticism of this study was that the placebo used was water, which is known to induce bronchospasm in some infants and may have biased the results. However, the authors did define objective endpoints which could be used in studies of this expensive agent in non-intubated children and in those children at greatest risk of morbidity and mortality.

Alternatives to conventional ventilatory support

A variety of strategies have been tried in neonatology and paediatrics to reduce the adverse effects of conventional ventilatory support with particular emphasis on prevention of barotrauma, oxygen toxicity and chronic lung disease. Gentle ventilation with permissive hypercapnia, high frequency oscillation, high frequency jet ventilation, negative pressure ventilation and extracorporeal life support all have their advocates but the indications for and advantages of each of these techniques are not clear. Home ventilation is still somewhat controversial, with ethi- cal overtones in some cases. However, it is becoming a more accepted norm for a variety of paediatric disorders.

Gentle ventilation strategies

By limiting peak inspiratory pressure and by accep- ting tidal volumes as low as 5 ml. kg- ’ , carbon dioxide tension will rise. Provided intracranial pressure is not a concern, oxygenation and cardiac output are adequate, and metabolic acidosis is corrected, hypercapnia per se is not harmful. Oxygen delivery is adequate, while barotrauma and residual chronic lung disease are minimised. This approach has been used successfully in neonates,3” adults”’ and children.“s

High frequency oscillation (HFO)

With the availability of reliable oscillators, interest in this subject has blossomed. The early strategies aimed at minimising ventilation pressures and lung inflation proved ineffective in comparison with conventional ventilation. More recently, a strategy aimed at recruitment of atelectatic lung units has been used experimentally and clinically with remark- able success particularly in diffuse, bilateral pulmonary diseases. 39 Airleak syndromes can be managed by oscillation which limits the peaks and troughs of pressure around the prescribed mean airway pressure allowing the lung to heal. Pulmonary haemorrhage can be managed using a high mean airway pressure to tamponade the bleeding sites while recruiting lung units. As high frequency oscillators generate a sinusoidal pressure waveform with an active expira- tory phase, carbon dioxide elimination is very effi- cient and some argue that this is very beneficial in the


management of pulmonary hypertension and persistent foetal circulation. A number of centres now use HFO successfully in babies who would previously have been candidates for extracorporeal life support4”

High frequency jet ventilation

There is evidence of a beneficial effect of high frequency jet ventilation in neonates with pulmonary interstitial emphysema. 4’ There are worries however about the difficulties of humidification and detecting gas trapping and barotrauma when this technique is used.

Negative pressure ventilation

Improvements in the design of negative extrathoracic pressure ventilators has resulted in renewed interest in their use in conditions where positive intrathoracic pressure has potentially adverse effects, e.g. after repairs involving connection of the systemic venous system to the pulmonary arterial system; in chronic ventilatory failure or in central hypoventilation syndromes.42

Extracorporeal life support (ECLS)

Initial enthusiasm in adults for ECLS waned after poor results, but ECLS has become established in neonatology for treatment of severe respiratory failure due to meconium aspiration syndrome, hya- line membrane disease, persistent pulmonary hypertension of the newborn, congenital diaphragmatic hernia and sepsis. In older children, bacterial and viral pneumonia, aspiration pneumonitis, pulmonary contusion and barotrauma are the commonest ‘pulmonary’ indications for ECLS.40 Technological advances mean that risks associated with venoarterial perfusion via jugular and carotid vessels will be reduced. Venovenous perfusion, heparin bonding of circuit components, improved pumps, hollow fibre oxygenators etc., should lessen morbidity. Results with ECLS are improving all the time for both neonates and older children. However, improvements in ‘conventional’ therapy are also occurring, e.g. high frequency oscillation, gentle ventilation, surfactant therapy and nitric oxide therapy. This makes it very difficult to judge the risk-benefit ratio for a given patient. One major problem is that outcome prediction for different diagnostic subgroups is not very precise and it is likely that a staged approach will emerge with ECLS as the backstop.40,4” ECLS enthusiasts disagree with this approach, arguing that earlier institution of ECLS improves outcome .@

Alternatives to conventional circulatory support

With advances in ECLS for respiratory failure, the extension of the technology to children with myocardial failure was inevitable.45,4”*47 Venoarterial perfusion supports the failing myocardium and has been used in congenital heart disease, as a bridge to transplantation, as therapy of myocarditis and as therapy of cardiotoxicity due to tricyclic antidepress- ants.48 Non-pulsatile ventricular assist devices also show promise.4v,s” Concern has been expressed about the ad hoc way in which these techniques have been used and there is a need for controlled prospective evaluation. Outcome figures are much less impressive than after ECLS for respiratory failure but are improving. In a recent study, 22 of 39 cases survived, 9 of whom were completely normal.5’

Underuse of analgesia for painful procedures

A recent audit has drawn attention to the underuse of analgesia for painful procedures in a busy paediatric intensive care unit. ” Although this unit may not be typical the authors noted that half of all recorded procedures were accompanied by an adverse response indicating pain even when analgesics or sedatives had been given. Many painful procedures were not preceded by analgesia or sedation. Auditing invasive procedures and pre-empting pain by use of appropriate and adequate analgesia, sedation or anaesthesia are obvious solutions.

Blood conservation

Anaemia due to blood sampling is a significant problem in paediatric intensive care with up to 10% of children enduring cumulative blood losses of up to 90 ml.kg- . I 53 The amount of blood sampled corre- lated positively with PICU stay and PRISM score and negatively with age. This iatrogenic anaemia can be minimised by using microsamples, in-line blood res- ervoirs,54 erythropoietin, and intraarterial optode catheters which continuously display arterial pH and blood gases. 55

Invasive monitoring

With the trend towards non-invasive monitoring, there is an understandable reluctance to use invasive haemodynamic monitoring because of technical diffi- culty, potential adverse effects and doubts about the usefulness of the data. However, in paediatric septic shock, for example, optimising oxygen delivery is feasible and beneficial.56*57 Ultrasound guided pulmonary artery lines can be sited in neonates and may give most useful data on the efficacy of attempts to control pulmonary hypertension.58


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Current controversies in paediatric intensive care