There is little previously published data on the role of P-HEMS in paediatric drowning cases and their utility in this context has yet to be established. There was a very high intervention rate in severely injured (ISS > 15) drowning cases in this series treated by the P-HEMS. All of these patients were intubated with 45 % requiring adjuvant anaesthesia. Consensus guidelines on management of drowning [5] emphasise early restoration of ventilation and circulation. Activation of teams able to provide anaesthesia assisted intubation and direct transport to specialist paediatric centres is therefore consistent with current best practice. P-HEMS are ideally constituted to deliver both advanced airway interventions and direct transport [6]. Definitive evidence that these interventions improve outcome is however not yet available. A large multicenter trial would be required as individual EMS systems are highly unlikely to encounter adequate patient numbers to make such a study feasible.
The previous study of the paediatric trauma case identification system used in Sydney indicated that direct identification by the P-HEMS service significantly outperformed paramedic identification from a central control room, and had profound effects on the overall performance of the Sydney prehospital trauma system [6]. Similarly whilst the P-HEMS case identification system was in operation in this study, all paediatric drowning cases with an ISS > 15 were identified for P-HEMS response and were transported directly to a paediatric specialty centre. After the NSW Ambulance withdrew access by the P-HEMS to the CAD system only four of seven cases were identified. Two of the three non-identified cases were transported by road paramedics to adult trauma centres with delays of several hours before transfer to a paediatric specialist centre. This indicates that further investigation of the effects of cessation of the P-HEMS case identification system should be undertaken and reinstatement of the parallel identification model may be warranted. Beyond the case identification process the system worked well, with all severe drowning cases identified for P-HEMS response receiving intubation and direct transport to a paediatric specialist centre.
The P-HEMS was also very accurate in identifying high risk patients for respiratory complications in this small series. No child that was not intubated during the prehospital phase of care subsequently required intubation in the hospital.
All children with a GCS over 3 on arrival of the P-HEMS survived. Twenty five percent of children who suffered a cardiac arrest survived which is a relatively high survival rate for out of hospital cardiac arrest. For all causes of reported paediatric out of hospital cardiac arrest survival rates range from 6.4 % to 12 % [9–12] with neurologically intact survival in half of these patients [9, 12, 13]. Arrested drowning victims are reported to have better survival rates than the all-cause arrest group. In a pooled review of 41 studies drowning associated arrests had a 22.7 % survival [9]. This is similar to the current series and emphasises the need to aggressively resuscitate paediatric drowning victims who have suffered cardiorespiratory arrest in the pre hospital setting as individual outcomes cannot be predicted.
No child survived who did not have a return of spontaneous circulation before admission to the emergency department. In all causes of paediatric cardiac arrest in a series of over 200 children in Melbourne, Australia less than 1 % survived if spontaneous circulation remained absent on arrival at hospital [10]. In a large US study of 599 out of hospital paediatric cardiac arrests the longest duration of CPR in a survivor with a good neurological outcome was 42 min [14] and a series of children who drowned reports no children receiving more than 25 min CPR having a good outcome [15]. A recent nationwide study of paediatric drowning outcome in the Netherlands found that no child who received CPR for more than 30mins without return of spontaneous survived with a good neurological outcome [16]. Prehospital management is therefore critical and again would suggest a role for P-HEMS in this population.
The decision surrounding cessation of cardiopulmonary resuscitation after drowning has been complicated by case reports of survival after long periods of both submersion [15] and CPR [17, 18, 19] in hypothermic patients. It is likely that hypothermia is only protective if it occurs before irreversible hypoxic-ischaemic cerebral injury which is less likely to occur in Australian water conditions compared to cooler areas of Europe or North America.
The rates of bystander CPR in this series were high, suggesting community education programs are having effect. All but one child with a GCS less than 8 on arrival of the P-HEMS had received bystander CPR, and in all asystolic children CPR was underway. Bystander CPR is associated with improved neurological outcome in children admitted to ED after drowning [20]. In cases of cardiopulmonary arrest secondary to drowning, positive pressure ventilation via mouth or mask is required in addition to chest compressions for resuscitation to be effective. In all causes of paediatric out of hospital arrest rates of favorable outcome increase if breaths are added [13].
An initial GCS above 8 at the scene was associated with full recovery. However a GCS below 8 did not predict a poor outcome, seven out of eight children with initial GCS between four and seven had good neurological outcomes. This is in accordance with other studies which also show initial neurological parameters such as low GCS, lack of response to pain and lack of pupillary reaction do not necessarily predict poor neurological outcomes [21, 22].
One child in this series survived neurologically intact after a period of asystolic cardiopulmonary arrest. Normal survival after cardiopulmonary arrest due to drowning has been well described [23] and in a meta-analysis of 442 drowning associated arrests the intact survival rate was 6 %, putting it well above rates for all other causes of cardiopulmonary arrest [9].
Limitations of this study
The neurological outcomes reported are short term. None of the children in this series who had a GCS between three and eight and were classified as normal were followed for more than 18 months and none had started school. Long-term cognitive sequelae may come to light as the child becomes older [24]. In some less severe cases the children were only followed until hospital discharge. Due to the geography and limited distribution of specialist paediatric neurology and rehabilitation services in NSW it is likely that the children would return to one of the two children’s hospitals if they required these services and would then have come to our attention during follow up. We cannot exclude relocation of the patient’s families from the catchment area of the paediatric hospitals leading them to seek rehabilitation services elsewhere.
Our study includes patients treated by a single HEMS service operating within a comprehensive EMS system. It is possible that the patients selected for HEMS dispatch are not representative of all paediatric drownings in the catchment area of the service. As it is known from the previous dispatch system study [6] that all severe paediatric drowning cases occurring prior to March 2011 were identified we are confident that the present study includes all severe drowning cases occurring during the operational hours of the service up to that date although it is possible that less severe cases were missed. Four severe drowning cases occurred after March 2011 when P-HEMS access to the CAD system was withdrawn that are not reported in this study. It is possible that these patients were different than those reported or that the different prehospital treatment provided may have produced different outcomes than that observed in this series.
