Surfactant therapy to facilitate weaning in paediatric patients dependent on extacorporeal membrane oxygenation

Background

Extracorporeal membrane oxygenation (ECMO) is a treatment modality employed in patients with severe cardiopulmonary compromise refractory to conventional treatment. Venoarterial (VA) ECMO support allows the patient to receive minimal respiratory and haemodynamic support by bypassing the lungs and heart; thus, allowing time to heal. ECMO has been used with considerable success in management of acute respiratory distress syndrome (ARDS) of viral aetiology.1 Studies have shown that patients receiving ECMO support for longer duration ≥21 days have significantly lower survival rate and a higher rate of complications as compared with those on ECMO support for ≤14 days.2 It is widely known that ARDS and the associated ongoing pulmonary injury leads to altered surfactant composition as well as reduction in endogenous surfactant levels.3 4 Furthermore, there is also evidence that ECMO itself can cause decreased lung compliance consequent to reduced surfactant activity.5 Few studies demonstrated that surfactant administration improves pulmonary function in patients on ECMO.6 7 But this approach is still not considered for routine use in these patients. In addition, other studies reported increased incidence of adverse effects such as pulmonary haemorrhage after surfactant administration.8 9 However, a recent study has found that surfactant can be administered with relative safety in paediatric patients on ECMO.10 We report our experience with successful surfactant administration in two patients with severe adenoviral ARDS who were ECMO dependent; with no adverse effects noted related to its use.

Case 1

Treatment

He was started on conventional ventilation but due to increasing respiratory compromise, was stepped up to high frequency oscillatory ventilation (HFOV) with inhaled nitric oxide (iNO). Despite very high oscillator settings he continued to deteriorate. His oxygenation index was 40 and he was thus referred to our centre for initiation of ECMO. He was cannulated on to VA ECMO at the referring centre by our mobile ECMO team with cannulae in the right internal jugular vein (IJV) and right common carotid artery (CCA). Though there was no evidence of significant cardiac dysfunction, still VA ECMO was chosen. The reason for this is twofold—there was unavailability of Veno-venous (VV) dual cannulae, and it is common practice for our mobile ECMO cannulation service to perform VA cannulation as that can be done at the patient’s bedside, with confirmation of the position of the cannulae on X-ray. He required full ECMO support with flows of 1.0–1.2 L/min and sweep gas flow rates of 3.5–4.0 L/min. He continued to require full ECMO support for over 2 weeks. He was treated extensively for possible bacterial/viral/ fungal sepsis with meropenem, vancomycin, fluconazole, nystatin, weekly cidofovir and supportive therapy as indicated. During this time, we were able to achieve adequate urine output and negative fluid balance with intravenous diuretics and fluid restriction. He was also regularly moved to prone position. Despite this there was no improvement on the chest X-rays or pulmonary function, and it was impossible to reduce the ECMO support. At this point his viral load had come down to 1020 copies/mL. Due to a complete lack of response to the above interventions the decision was made to administer exogenous surfactant to try to facilitate weaning from ECMO. The patient was given three doses of porcine surfactant over 4 days (35 mg/kg/dose) and was successfully weaned from ECMO within 24 hours of the third dose. During and after administration of surfactant, we observed that his saturations went up from 88% to 99% and pulmonary compliance increased by 21% (0.46–0.56 mL/kg/cmH2O), which was also reflected in the compliance assessment performed by bagging the patient while attached to a manometer. His chest X-ray showed marked improvement (figure 1A,B) and his arterial oxygen tension/fractional inspired oxygen (PaO2/FiO2) ratio improved by 14% (17.65–20.00 kPa) (figure 2) . Surfactant administration was tolerated well without any adverse effect.

Outcome

The patient went on to make a complete recovery from ARDS and was discharged home with no sequelae 3 months after decannulation from ECMO.

Case 2

Treatment

Initially, the patient was started HFOV with iNO to which he showed poor response. He had a high oxygenation index of 37, and was referred to our centre for ECMO support. VA ECMO was initiated at the referring hospital by our mobile ECMO team with cannulation of right IJV and right CCA. There was no evidence of significant cardiac dysfunction. Again, VA ECMO was chosen because of unavailability of VV dual cannulae, and also because it is the common practice for our mobile ECMO cannulation service. He required full ECMO support with flow of 0.95–1.1 L/min and sweep gas flow rate of 3.5–4.0 L/min. Over the course of the next 2 weeks he was treated for sepsis with meropenem, vancomycin, fluconazole and weekly cidofovir. He was regularly moved to prone position. We achieved adequate urine output and negative fluid balance with fluid restriction and intravenous diuretics. His viral counts showed a steady decreasing trend and came down to 2600 copies/mL. Despite all this, he continued to need full ECMO support and neither his chest X-rays nor his lung function showed any improvement. Therefore, the decision was made to administer exogenous surfactant in order to try to reduce the ECMO support needed. He received two doses of porcine surfactant (48 mg/kg dose) on consecutive days. Following the second dose of surfactant, we observed that the X-ray significantly improved (figure 3A,B). The daily pulmonary compliance assessment performed by bagging the patient while attached to a manometer revealed a dramatic improvement in the pressure required to inflate the lungs, and his pulmonary compliance increased by 19% (0.48–0.57 mL/kg/cmH2O). His PaO2/FiO2 ratio improved by 20% (16.35–19.62 kPa) (figure 2). We were subsequently able to wean him from ECMO uneventfully. Surfactant administration was well tolerated without any adverse effects.

Outcome

Following successful weaning from ECMO, the patient was subsequently discharged from PICU. He is currently under long-term respiratory follow-up, four and a half months after coming off ECMO support.