Pediatric Respirology and Critical Care Medicine

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 3  |  Issue : 2  |  Page : 28--35

Clinical outcomes of critically ill infants requiring interhospital transport to a paediatric tertiary centre in Hong Kong


Karen Ka Yan Leung1, So Lun Lee1, Ming-Sum Rosanna Wong1, Wilfred Hing-Sang Wong1, Tak Cheung Yung2,  
1 Department of Paediatrics and Adolescent Medicine, Queen Mary Hospital, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pok Fu Lam, Hong Kong
2 Department of Paediatric Cardiology, Queen Mary Hospital, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pok Fu Lam, Hong Kong

Correspondence Address:
Karen Ka Yan Leung
Department of Paediatrics and Adolescent Medicine, Room 115, New Clinical Building, Queen Mary Hospital, 102 Pokfulam Road
Hong Kong

Abstract

Background: Specialised transport teams are associated with fewer complications during interhospital transport. Such teams are currently unavailable in Hong Kong. The aim of this study was to review the clinical outcomes of critically ill infants requiring interhospital transport in Hong Kong. Methods: We retrospectively reviewed the characteristics and clinical outcomes of all infants transported from the neonatal units of regional or private hospitals into the neonatal or cardiac intensive care unit (ICU) of Queen Mary Hospital, a tertiary-wide academic centre in Hong Kong from 1st August 2013 to 31st July 2016. Results: A total of 256 infants with a mean gestational age of 31.7 ± 5.5 weeks and birth weight of 1732 ± 1007 g were included in the study. While 143 (55.9%) patients were intubated during transport, there was no documentation of close monitoring of physiological parameters for 91.4% of the patients. Close to half of the patients (44.1%) had complications on admission and 23.4% required significant interventions immediately after the transfer. The median length of stay in the ICU was 3.3 (range: 0.5–342.6) days. Five patients died of non-transport-related causes within 7 days of admission. Multiple logistic regression analysis showed that intubated patient (P = 0.001) or patient requiring inotropic support during transport (P = 0.027) were more likely to develop complications. Higher birth weight (P = 0.022) and younger chronological age at transfer (P = 0.030) were also significant risk factors for complications. Conclusions: Complications and interventions are considerable during interhospital neonatal transport in Hong Kong. The complication rate was higher than medical infrastructures that provided a specialised team for this process. Documentation during transport was inadequate.



How to cite this article:
Yan Leung KK, Lee SL, Wong MSR, Wong WH, Yung TC. Clinical outcomes of critically ill infants requiring interhospital transport to a paediatric tertiary centre in Hong Kong.Pediatr Respirol Crit Care Med 2019;3:28-35


How to cite this URL:
Yan Leung KK, Lee SL, Wong MSR, Wong WH, Yung TC. Clinical outcomes of critically ill infants requiring interhospital transport to a paediatric tertiary centre in Hong Kong. Pediatr Respirol Crit Care Med [serial online] 2019 [cited 2019 Nov 14 ];3:28-35
Available from: http://www.prccm.org/text.asp?2019/3/2/28/264102


Full Text



 Introduction



Care of critically ill children during transport is important yet often overlooked. Based on international experiences and data, the involvement of a specialised paediatric transport team is strongly correlated with fewer adverse events,[1],[2],[3] and patients were less likely to deteriorate in clinical conditions during the transport.[2],[4] Conversely, mortality rates are higher among patients transported by non-specialised teams.[5] In most developed countries, the health-care infrastructure includes a dedicated specialised service to transport patients between points of care.

Hong Kong is one of the most densely populated places in the world, with a population of 7.24 million.[6] The public health-care system provides 90% of total hospital bed-days.[7] There are 13 paediatric departments in the public health-care system and interhospital transport of paediatric patients takes place on a daily basis. At present, patient care during transport usually rests with the referring hospital. Although there are local guidelines for interhospital transport of adult patients, there is currently no legislation, Paediatric College recommendations or Hospital Authority guidelines or recommendations on the training or qualifications of doctors responsible for the escort of critically ill children. In 1984, a local study showed that hypothermia, acidaemia, hypercapnia, hypoxaemia, central cyanosis and circulatory failure were common complications after transport of preterm infants.[8] In 1998, an audit of the transport of paediatric cardiac patients in Hong Kong showed that retrieval of such patients by a dedicated team can prevent significant acidosis and hypothermia for ventilated patients.[9]

To date, a dedicated paediatric transport team in Hong Kong is still under development. A specialised transport team equipped with proper training, equipment and accreditation may improve the standard of care and patient outcomes. The availability of the team might also expand treatment opportunities for critically ill patients requiring high-frequency ventilation, nitric oxide or extracorporeal membrane oxygenation support, who are currently deemed unsafe for transport under our current health-care system setting.

The primary objective of this study was to review the clinical outcomes of critically ill infants requiring interhospital transport without any specialised paediatric transport team in Hong Kong. The outcome variables and measures were complications, length of stay and early mortality. The secondary objective was to analyse the associated patient characteristics and potential factors that may affect these outcomes.

 Methods



Study design

This is a retrospective observational study of infants transported from regional or private hospital's neonatal unit to intensive care units (ICUs) at Queen Mary Hospital (QMH) over a 3-year period. This study was approved by the Institutional Review Board of the University of Hong Kong/Hospital Authority West Cluster (Reference number: UW 16-499).

Data collection and outcome measures

Records of infants transported into QMH from regional or private hospital's neonatal unit between 1st August 2013 and 31st July 2016 were captured by our hospital database (Clinical Data Analysis and Reporting System) and verified by handwritten admission records. Those transported into the ICU were included as study participants while those admitted into other paediatric wards were excluded. Relevant data were extracted and inputted into a standardised template for data analysis.

Patient characteristics included gender, birth weight, mode of delivery, Apgar scores at 5 min, gestational age at birth, chronological age and weight on the day of transport. Patients were marked as small for gestational age (SGA) if their birth weights were <10th percentile according to the reference ranges for Chinese newborns.[10] Patients were categorised as extreme preterm if they were born before 28 weeks of gestation, very preterm if they were born at 28 to <32 weeks of gestation, mild preterm if they were born at 32 to <37 weeks of gestation and term if they were born ≥37 weeks of gestation.[11],[12]

The names of the referring hospital, indications for transport, type of transport (emergency or elective) and mode of transport were collected. The duration of interhospital transport was calculated as the time between the discharge time from the referring hospital and the admission time at QMH as recorded in the Hospital Authority's computerised record system (clinical management system). Since similar data were not available from private hospitals, only transports between Hospital Authority hospitals were included in the analysis involving transport duration. The interhospital transport distance was the ground travel distances estimated from the Google Map application. The intensive care support that the patients received during transport (mode of respiratory support, inotropic support, prostaglandin infusion and sedation if any), the type of access (arterial access, central access) and details of patient monitoring and conditions during transport were also retrieved. The patient was considered to have documentation of close monitoring if the 'Hospital Authority Neonatal Emergency Transport Observation Chart' during transport or equivalent documentation was used with documentation of at least one set of vital signs. The standardisation of 'Hospital Authority Neonatal Emergency Transport Observation Chart' was implemented from 2015, but there are no guidelines on when to use the form and it is not mandatory to fill in all parameters or utilise the form. In general, it is used by the Hospital Authority Neonatal ICUs during the interhospital transfer of critically ill patients. There is no standardisation of transport documentation form among the private hospitals. The transport record was considered as equivalent if it was intended to document the patient demographics, details of interhospital transport and vital signs during transport. All the medical record was reviewed by the principal investigator based on the criteria defined. The types of surgical operation received by the patients after admission were also included.

Pre-transport and post-transport physiological parameters and significant interventions required during and within 1 h after transport were analysed. Pre-transport physiological parameters taken in the referring hospital closest to the time of transport was captured. Post-transport physiological parameters were extracted from the first set of recorded information within 1 h of admission to the ICU.

For the ease of reference, adverse events and interventions associated with interhospital transport are categorised and defined in [Table 1].{Table 1}

The length of stay in the ICU and total hospital stay (including the referring hospital) were also analysed. Early mortality was defined as death within 7 days of admission. The causes of death were reviewed.

Statistical analysis

Results are presented as frequencies, means or medians as appropriate. Fisher's exact test was used to compare categorical variables. All continuous variables were tested for normal distribution. Unpaired t-test and one-way analysis of variance were used to compare continuous variables with a normal distribution. Skewed data were transformed by log10 base before comparison and non-parametric methods. The Mann–Whitney U-test or Kruskal–Wallis test was used for analysis. Univariate statistical analysis was carried out to test for associations between the transport condition and complications. A probability value (P value) of <0.05 with two sides was considered statistically significant. Significant variables in the univariate analysis were included in a multiple logistic regression analysis to verify an independent association. These results were reported as odds ratio with 95% confidence intervals. Analyses were performed using the SPSS® version 24 (IBM Corp, IBM SPSS Statistics for Macintosh, Armonk, NY: USA).

 Results



During the study, 256 infants were transported from neonatal units of regional or private hospitals to QMH ICUs. Their characteristics are summarised in [Table 2]. There were slightly more male infants (n = 141) than female infants (n = 115). The mean birth weight was 1732 ± 1007 g. Forty-five infants were born small for the gestation of age. Patients were divided into four groups according to their gestational age. The two main groups of patients being transported were extreme preterm (n = 92, 35.9%) and term infants (n = 69, 27.0%). The group of extremely preterm infants were transported at an older chronological age with a median of 29.1 (range 0.8–150.6) days, whereas term infants were transported at a younger chronological age with a median of 2.5 (range 0.4–71.5) days (P< 0.001).{Table 2}

The indications for transport were for higher levels of cardiac (n = 117, 45.7%), surgical (n = 72, 28.1%) and respiratory (n = 41, 16.0%) care. The remaining reasons for transport were for ophthalmological assessment, severe sepsis, seizure, hypoglycaemia requiring central venous access, perinatal depression or those requiring therapeutic hypothermia and bed status issues. The majority of the cardiac surgery required was patent ductus arteriosus ligation (n = 97), followed by the management of cyanotic heart disease (n = 6) and extracorporeal membrane oxygenation (n = 3). The most common indications for non-cardiac surgery were necrotising enterocolitis (n = 21) and malrotation (n = 5).

Over half of cases (n = 145, 56.6%) were emergency transports. Most of the transports (n = 182, 71.1%) were from Hospital Authority Hospitals. The majority of transports (n = 248, 96.9%) were ground transport by ambulance, whereas the rest involved a combination of ambulance and ferry. The mean transport time was 47.2 ± 15.2 min, and the median transport distance was 10.7 (range 5.1–731.4) km.

Evidence of close monitoring of physiological parameters during transport were found in 22 (8.6%) transports. For the 142 transports that recorded details of the transport personnel involved, 126 (88.7%) were escorted by doctors. Nearly 70% (n = 179) of patients were critically ill during transport; 143 (55.9%) required invasive mechanical ventilation, 32 (12.5%) required non-invasive ventilation support, 37 (14.5%) required inotropic support, 26 (10.2%) were under sedation and 9 (3.5%) required continuous prostaglandin infusion. Other transport details are summarised in [Table 2].

A total of 154 complications were documented in 113 (44.1%) patients with 33 patients affected by >1 complication. The types and numbers of complications immediately after transport are shown in [Table 3]. The majority (n = 49) of complications involved the respiratory system, including desaturation (n = 27), hyperventilation (n = 12), severe hypoxia (n = 9) and endotracheal tube obstruction (n = 1). Other complications were hypothermia (n = 30), hypoglycaemia (n = 29) and acidosis (n = 17).{Table 3}

Fifty-nine patients (23%) required significant interventions during transport or within 1 h of admission. There was a total of 68 interventions, and 9/59 patients (15%) required two interventions. The majority (n = 41) were respiratory interventions, including manual bagging (n = 7), step up of respiratory support (n = 33) and change of endotracheal tube (n = 1). Other types and number of interventions are summarised in [Table 4].{Table 4}

Complete sets of all four physiological parameters (pulse oximetry [SpO2], (systolic blood pressure (SBP), heart rate and temperature) before and after transport were available for 47 patients. Individual physiological parameters before and after transport were available for another 85 patients for SpO2, 23 patients for temperature, 22 patients for SBP and 44 patients for heart rate. Using these available data sets, there were 24 significant changes in physiological parameters affecting 20 patients. The majority of changes involved the respiratory system (n = 15). Other significant changes were significant decrease in temperature (n = 4), significant decrease in blood pressure (n = 2), significant increase (n = 2) and significant decrease (n = 1) in heart rate.

Patients were more likely to develop complications if they have high birth weight (P = 0.020), transported at younger chronological age (P< 0.001), intubated during transport (P = 0.015) or required inotropic support during transport (P = 0.007). After adjustment using multiple logistic regression, all of these risk factors remained as signification risk factors for complications. There were no statistically significant associations between complications and gender, gestational age at birth, SGA, weight at transport, transport distance, type of referring hospital, type of transport, type of referral and if there were monitoring during transport. These details are summarised in [Table 5].{Table 5}

The median length of ICU stay was 3.3 (range: 0.5–342.6) days and total hospital stay was 87.0 (range 2.0–885.0) days. There were five non-transport-related deaths within 7 days of admission. The causes of death were post-operative arrest (n = 2) and withdrawal of care (n = 3).

 Discussion



In Hong Kong, interhospital transport of critically ill paediatric patients is common. A previous retrospective 7-year review of neonatal transport across Paediatric Departments under the Hospital Authority in Hong Kong showed that there was an average of 255 transports per year.[24] Our centre is a major tertiary academic referral centre for neurosurgery, paediatric surgery, burn, liver transplant, oncology and bone marrow transplant. It is also the only cardiology centre which can provide extracorporeal membrane oxygenation support and cardiothoracic surgery. We receive referrals from all public and private hospitals in Hong Kong, as well as from Macau and the Chinese Mainland near our locality. The result from this study may provide important information for future health-care planning and reference data for other countries where specialised paediatric transport services are lacking.

During the defined 3-year study, we received an average of 85 critically ill infants per year. The paediatric service model in Hong Kong is currently being reorganised and the tertiary paediatric services has commenced relocation to the Hong Kong Children's Hospital (HKCH). After the centralisation of tertiary paediatric services to the HKCH, interhospital transports are expected to be more frequent.

The median transport distance of 10.7 (range: 5.1–731.4) km from this study was relatively short compared to other health-care systems (22.2–47.8 km),[2],[4],[25] the mean transport duration was similar (47.2 ± 15.2 vs. 30–113 min).[2],[4],[5],[14],[26] The heavy traffic in urban Hong Kong is the most likely reason for the longer transport period. A majority (~70%) of the transported patients were critically ill, but there was no evidence of close monitoring of physiological parameters for 91.4% of the patients in this study. This could reflect that the importance of documentation was still underestimated or the escort team was not specialised in transport. Standardised record should be maintained so that events are available for review by the receiving hospital.

Complications occurred for close to half (44.1%) of the transports. Although this local complication rate seems much higher than transport carried out by specialised transport teams elsewhere in the world (1%–4%),[2],[3],[5] it was lower than the figure in transport conducted without a specialised team (61%–75%).[1],[2],[5],[8] It is difficult to draw comparison across studies to explain this lower rate of complication. Some explanations may include the possibilities that our cohort consisted of more stable patients or more experienced staff, even though they were not specialised in transport per se.

The majority (26.5%) of complications were related to the respiratory system. This rate appears to be comparable to the figures reported by non-specialised transport teams (18.4–53%),[5],[14],[27] but was much higher than the rate of 0.5%–1.8% observed by specialised transport teams.[5],[14] Most of the interventions required during or shortly after admission were also due to airway compromise. Multiple logistic regression analysis in our study revealed that intubation was a significant risk factor for complications. There were these possible contributing factors to respiratory complications. First, there was a lack of sophisticated monitoring of end-tidal volumes and serial blood gas during transport to provide feedback that may have indicated the need for ventilator adjustments. Second, humidification of the ventilator circuit may have been suboptimal. Finally, regular suctioning could have been difficult due to environmental factors during transport, for example, motion and noise, and limited space, workforce and equipment.

Acidosis was another common complication (22.1%). Although this was lower than the rate reported in the literature by non-specialised teams (24%–50%),[8],[27] our study might have underestimated the number of acidosis case as paired pre- and post-transport arterial blood gas results were only completed in 30% (77 patients) of the patient transported for analysis. Acidosis could be a result of haemodynamic or respiratory instability. Hypothermia was found in 11.7% of the patients, which appears to be comparable to the rates in the literature reported by non-specialised teams (3.8%–30%).[5],[8],[14],[27],[28] Again, it seems higher than that achieved by specialised transport teams (0%–1%).[5],[14] Hypothermia could be due to changes in ambient temperature during interhospital transport, insufficient insulation of the transport incubator and suboptimal humidification inside the transport incubator. Hypoglycaemia occurred in 11.3% of the patients, higher than that (7%) reported by non-specialised transport teams.[27] This could be caused by the lack of glucose monitoring before and during transport.

When comparing our results to historical data of the same hospital in 1984, improvements were noted in complication rates after transport. These improvements could be contributed by advancement in medical equipment (e.g., transport incubators and ventilators). However, the rates of hypothermia and respiratory complications were still considerably higher than that reported by studies with specialised transport teams [Table 6]. Our study suggests that, in our locality, the lack of specialised transport teams may be associated with higher rates of complication during interhospital transports. More studies will be needed to determine whether a specialised transport team will result in better outcomes and a significant reduction in adverse events for these patients.[29]{Table 6}

Limitations

There are four major limitations. First, this is a single-centre study limited to inbound transport of critically ill infants for tertiary/quaternary care. Therefore, the study might have included more critically ill infants than other series. Second, this was a retrospective study. Despite efforts made to locate the missing information from referring hospitals through our Hospital Authority's computerised record, some information, especially the pre-transport physiological parameters, were not found. There were also discrepancies in the methods of measuring physiological parameters across different referring hospitals, for example temperature (rectal, axillary, tympanic and skin), blood pressure (arterial blood pressure vs. non-invasive blood pressure monitoring), glucose reading (different brands of glucometer vs. blood gas machine) and arterial blood gas (i-STAT® vs. blood gas analyser). As a result, only 18.3% of the patients had complete sets of pre-transport and post-transport physiological parameters, and most patients' condition during transport could only be deduced by analysing the post-transport physiological parameters. Third, although indications for transport and patients' diagnoses might affect the complication and mortality rate, stratified analysis was not performed as there were not enough data to retrospectively categorise the patient's disease severity with a validated scoring system, for example, 'Paediatric Risk of Mortality' score. Finally, the retrospective nature of this study did not allow the inclusion of all confounding factors in the analyses. For example, referrals were received from 19 different hospitals, and experiences of the escort personnel, monitoring skills during transport and transport equipment varied across these hospitals.

 Conclusions



The study showed that complications and interventions are considerable during interhospital transport, particularly in intubated and patients requiring inotropic support. Higher birth weight and younger chronological age at transfer were also significant risk factors for complications. The complication rate was higher than medical infrastructures that provided a specialised team for this process. Documentation during transport was inadequate.

Acknowledgements

The authors sincerely thank all the doctors and nursing staff of the intensive care units of the Queen Mary Hospital, Hong Kong.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Barry PW, Ralston C. Adverse events occurring during interhospital transfer of the critically ill. Arch Dis Child 1994;71:8-11.
2Britto J, Nadel S, Maconochie I, Levin M, Habibi P. Morbidity and severity of illness during interhospital transfer: Impact of a specialised paediatric retrieval team. BMJ 1995;311:836-9.
3Roy RN, Langford S, Chabernaud JL, Petresen S, Peitersen N, Kollée L, et al. Newborn transport around the world. Semin Neonatol 1999;4:219-35.
4Edge WE, Kanter RK, Weigle CG, Walsh RF. Reduction of morbidity in interhospital transport by specialized pediatric staff. Crit Care Med 1994;22:1186-91.
5Orr RA, Felmet KA, Han Y, McCloskey KA, Dragotta MA, Bills DM, et al. Pediatric specialized transport teams are associated with improved outcomes. Pediatrics 2009;124:40-8.
6Information Service Department HKSARG: Hong Kong: The Facts; 2015. Available from: https://www.gov.hk/en/about/abouthk/factsheets/docs/population.pdf. [Last accessed on 2019 Jan 03].
7WHO and Department of Health HK: Health Service Delivery Profile Hong Kong (China) 2012. World Health Organization Western Pacific Region; 2012. Available from: http://www.wpro.who.int/health_services/service_delivery_profile_hong_kong_(china).pdf. [Last accessed on 2019 Jan 03].
8Fok TF, Lau SP. High risk infant transport in Hong Kong. Bull J Hong Kong Med Assoc 1984;36:39-45.
9Cheung YF, Leung MP, Chau KT, Hung KW, Cheung MH. Audit of paediatric cardiac patient transport. Hong Kong J Paediatr 1998;3:147-53.
10Fok TF, So HK, Wong E, Ng PC, Chang A, Lau J, et al. Updated gestational age specific birth weight, crown-heel length, and head circumference of Chinese newborns. Arch Dis Child Fetal Neonatal Ed 2003;88:F229-36.
11Lucas da Silva PS, Euzébio de Aguiar V, Reis ME. Assessing outcome in interhospital infant transport: The transport risk index of physiologic stability score at admission. Am J Perinatol 2012;29:509-14.
12Moutquin JM. Classification and heterogeneity of preterm birth. BJOG 2003;110 Suppl 20:30-3.
13Zubrow AB, Hulman S, Kushner H, Falkner B. Determinants of blood pressure in infants admitted to neonatal intensive care units: A prospective multicenter study. Philadelphia Neonatal Blood Pressure Study Group. J Perinatol 1995;15:470-9.
14Vos GD, Nissen AC, H M Nieman F, Meurs MM, van Waardenburg DA, Ramsay G, et al. Comparison of interhospital pediatric intensive care transport accompanied by a referring specialist or a specialist retrieval team. Intensive Care Med 2004;30:302-8.
15Rutter N. Temperature control and its disorders. In: Rennie JM, Roberton NR, editors. Textbook of Neonatology. Edinburgh, New York : Churchill Livingstone; 1999.
16Hellström-Westas L, Hanséus K, Jögi P, Lundström NR, Svenningsen N. Long-distance transports of newborn infants with congenital heart disease. Pediatr Cardiol 2001;22:380-4.
17Lee SK, Zupancic JA, Pendray M, Thiessen P, Schmidt B, Whyte R, et al. Transport risk index of physiologic stability: A practical system for assessing infant transport care. J Pediatr 2001;139:220-6.
18Weiner G, Zaichkin J. Textbook of Neonatal Resuscitation. 7th ed. Elk Grove Village: American Academy of Pediatrics; 2016.
19Pollack MM, Patel KM, Ruttimann UE. PRISM III: An updated pediatric risk of mortality score. Crit Care Med 1996;24:743-52.
20Prater S, Shah M. Neonatal and pediatric transport. In: Tintinalli J, editor. Tintinalli's Emergency Medicine: A Comprehensive Study Guide. North Carolina: McGraw-Hill Global Education Holdings, LLC; 2016.
21Goldsmith J, Karotkin E. Ventilation strategies. In: Assisted Ventilation of the Neonate. Philadelphia: Elsevier; 2011. p. 265-76.
22Koh TH, Aynsley-Green A, Tarbit M, Eyre JA. Neural dysfunction during hypoglycaemia. Arch Dis Child 1988;63:1353-8.
23Abbott Diabetes Care Inc. Evaluation of the FreeStyle Optium Neo Blood Glucose and Ketone Monitoring System. Abbott; 2013.
24Wan C. Report on Neonatal Transport among Various HA Hospitals with Paediatric Departments 2008-2014. Hong Kong; 2015.
25Ramnarayan P, Thiru K, Parslow RC, Harrison DA, Draper ES, Rowan KM. Effect of specialist retrieval teams on outcomes in children admitted to paediatric intensive care units in England and Wales: A retrospective cohort study. Lancet 2010;376:698-704.
26Berge SD, Berg-Utby C, Skogvoll E. Helicopter transport of sick neonates: A 14-year population-based study. Acta Anaesthesiol Scand 2005;49:999-1003.
27Sabzehei MK, Basiri B, Shoukohi M, Torabian S, Razavi Z. Factors affecting the complications of interhospital transfer of neonates referred to the Neonatal Intensive Care Unit of Besat Hospital in 2012–2013. J Clin Neonatol 2016;5:238-42.
28Rathod D, Adhisivam B, Bhat BV. Transport of sick neonates to a tertiary care hospital, South India: Condition at arrival and outcome. Trop Doct 2015;45:96-9.
29Ligtenberg JJ, Arnold LG, Stienstra Y, van der Werf TS, Meertens JH, Tulleken JE, et al. Quality of interhospital transport of critically ill patients: A prospective audit. Crit Care 2005;9:R446-51.