Veno-venous ECMO with Bicaval Cannula for Refractory Hypoxemia in a Child

CASE HISTORY

A 2-year-old male child was admitted to the referring hospital with complaints of fever for 7 days, cough for 4 days, fast breathing, and abdominal pain for 2 days.¹ On presentation, the initial assessment suggested that the child was in an unstable and life-threatening physiological state as per the pediatric assessment triangle (PAT triangle) and was admitted to the Pediatric Intensive Care Unit (PICU).² The child was given oxygen via a mask, and empirical antibiotic therapy was started. A chest radiograph showed left-sided inhomogeneous opacity with an air bronchogram suggestive of consolidation, occupying the left mid and lower zones, and it rapidly involved left hemithorax in the subsequent radiographs (Fig. 1).

Serial arterial blood gas analysis revealed worsening hypoxia and hypercarbia. The child was intubated and initiated on mechanical ventilation. The child was started on pressure-regulated volume-controlled (PRVC) ventilation mode with positive end-expiratory pressure (PEEP) titrated at 10 cmH₂O, tidal volume of 6 mL/kg, FiO₂ 1.0, inspiratory time of 0.8 seconds, frequency 30/min, and a plateau pressure limit of 30 cmH₂O. After 3 hours of ventilation at such high pressures, the child developed bilateral pneumothoraces.

Bilateral intercostal drains were inserted and the child was then shifted to high-frequency oscillatory ventilator (HFOV) (Fig. 2). Initial investigations were unremarkable except for the presence of thrombocytopenia, persistent hypoxemia (pO₂ < 50 mm Hg), and hypercarbia (pCO₂ 80 mm Hg). Despite all efforts, refractory hypoxemia did not improve, and he was shifted to our facility for further care after 24 hours of admission at the initial hospital. During transit, the child was ventilated via Bain’s circuit with 100% oxygen.

On arrival, the child had tachycardia, maintaining mean arterial pressures above 50th centile for age, and was intubated with a 4.5 mm cuffed ET tube and ventilated via Bain circuit. The child was transported on midazolam at a dose of 1 microgram per kg per minute and intermittent doses of vecuronium. In our PICU, the child was initiated on conventional ventilation in the prone position.

An invasive arterial line was secured, and serial blood gases were taken. While the patient was on HFOV, blood gas parameters (pH 7.1, pO₂ 48 mm Hg, and pCO₂ 78 mm Hg) did not improve. A call was made to rescue the child on extracorporeal membranous oxygenation (ECMO).

A comprehensive echocardiographic evaluation was done to rule out cardiac dysfunction, and a decision was made to start the child on veno-venous (VV) configuration ECMO as the child was hemodynamically stable and required no inotropic escalation during (the course of) present and previous admission.

The child was cannulated with a 16 French bicaval double lumen catheter (Getinge Avalon Elite bicaval catheter) accessed via the right internal jugular vein and the position was confirmed by ECHO and chest radiograph (Fig. 3). The child’s weight was 12 kg and 99 cm in height with a body surface area of 0.57 m². Veno-venous ECMO was initiated with a flow rate of 1.3 L/min and a sweep gas flow of 2.0 L/min. Later, sweep gas flow was decreased to 1.5 L/min to target pCO₂ between 40 and 45 mm Hg. Immediate post-cannulation, flows dropped and chattering was noticed on the access line. Volume resuscitation was done with a crystalloid bolus of 10 mL per kg following which, chattering stopped ceased and flows stabilized. The child continued to receive pressure control mode (PCV) ventilation with PEEP of 10 cmH₂O, a rate of 10 per minute, and a driving pressure of 10 cmH₂O in accordance with the resting lung strategy to prevent atelectrauma.

Sedation was started with fentanyl (1 µg/kg/min) and vecuronium infusion (1 µg/kg/min) for the first 36 hours followed by intermittent bolus doses of 0.1 mg per kg. Strict input/output monitoring was done in order to maintain fluid balance. Enteral nutrition was started 6 hours after the cannulation and was optimized to achieve calorie targets of 1,200 kcal and 15 gms of protein per day. Neurological and somatic perfusion was monitored continuously by near-infrared spectroscopy (NIRS).

Anticoagulation was maintained using heparin infusion at 10 units/kg/hour, and monitoring was done using bedside activated clotting time (ACT) every second hour with a target of 180–200 seconds. Initially, blood gas analysis was done every 2 hours and gradually monitored at 6-hour intervals. Post cannulation, the child’s pO₂ improved to 106 mm Hg and pCO₂ to 36 mm Hg with a pH of 7.37.

Initial biochemistry revealed thrombocytopenia (platelet count 56,000/cumm) with elevated inflammatory markers (CRP 225 mg/dL and Procalcitonin 32.30 ng/mL). A multiplex PCR respiratory panel tested positive for Streptococcus pneumoniae. Blood and ET cultures sent on the first day of admission grew no organism.

A bedside flexible fiberoptic bronchoscopy was done on day 3 of ECMO with a 2.8 mm Olympus bronchoscope passed through a 4.5 mm ET tube, and bronchoalveolar lavage was taken. BAL culture grew no definitive organism. A repeat bronchoscopic toilet was given on day 5 of ECMO in view of given the progressively falling delivered tidal volumes. On day 6 of ECMO, child developed an increased frequency of loose stools and multiplex PCR of stool tested positive for Giardia and enteroaggregative Escherichia coli, although the culture grew nothing was negative. The child had worsening infiltrates on CXR and was given one more bronchoscopy toilet on day 9 of ECMO. On day 10 of admission, a second blood culture was sent in view because of rising white cell counts and inflammatory markers which isolated grew pan-resistant E. coli on blood culture, and antibiotics were accelerated and administered according to the antibiogram. Chest radiographs improved gradually, and inflammatory markers improved by day 10. Once the active infection was controlled and inflammatory markers were decreased with radiological clearing of the lung, with improvement in lung compliance and delivered tidal volume, weaning from ECMO was planned. Ventilator settings were optimized with a PEEP of 8 cmH₂O and tidal volume target of 6 mL/kg at which, the peak pressures were 20–22 mm Hg. Sweep gas flow was stopped and under strict blood gas monitoring. The child maintained pO₂ above 70 mm Hg at 0.21 FiO₂ and a PCO₂ of 38 mm Hg while the child was off VV ECMO for 12 hours. The child was successfully decannulated on day 11 of admission. The child remained on ventilator for a further 48 hours, wherein, sedation was weaned off further, and extubation readiness was assessed (Fig. 4). Another bronchoscopy toilet was done post-ECMO, and BAL samples were sterile. Child developed features of sedation withdrawal, and clonidine was added. After control of secretions and an acceptable level of sensorium, the child was extubated on day 13 of admission and was electively given HFNC, which was tapered and stopped over the next 36 hours.

The child continued to be monitored and repeat blood cultures were sent, which were sterile. Antibiotics were given for 14 days and then stopped. The child continued to be monitored for signs of withdrawal, which gradually improved over the course of the hospital stay. On the 21st day of admission, the child was hemodynamically stable, with no oxygen requirement, afebrile for over 1 week, accepting and tolerating feeds well, and had normal biochemistry and sterile cultures from all sites and hence, was discharged. In the initial 6 months of follow-up, the child had 2 episodes of wheezing and was given inhaled budesonide for 4 weeks each time and beta-agonists during the acute phase. There was no family history of asthma or allergic respiratory ailments. There have been no wheezing episodes for the last 6 months. The child was neurologically normal for his age at one year follow-up and had started attending school.

DISCUSSION

Refractory hypoxemia with an underlying reversible pathology is an indication for ECMO therapy in pediatric and neonatal subjects.^3,4 However, proning has been proven to provide mortality benefits in adult ARDS subjects.⁵ Despite adult trials demonstrating increased mortality with HFOV when compared to conventional ventilation, pediatric ICUs regularly use HFOV in ARDS as a rescue modality, with anecdotal evidence suggesting mortality benefit.⁶ PROSPECT trial is currently studying the same in pediatric subjects, and results are awaited.⁷ Extracorporeal membranous oxygenation can be employed in either a veno-arterial (VA) or a VV configuration. Extracorporeal life support organization recommends VV ECMO in a child with modest inotropic support and stable hemodynamics so as to avoid VA ECMO, as complications are more common with VA ECMO. Hemodynamics improve, and right heart dysfunction stabilizes with normalization of PaCO₂ and reduction of high ventilatory pressures on VV ECMO. Veno-venous ECMO can be instituted as a single or dual cannula access. Single-site access options include uni-caval or bi-caval catheters, which differ in the number of sites that drain the blood. Dual lumen catheters drain from SVC and returned return to RA towards the tricuspid valve. Bi-caval catheters have three ports: Two for blood drainage of blood from both SVC and IVC and one for return towards the tricuspid valve.⁴ Dual lumen catheter has the advantages of the usage of only one large lumen vein, facilitation of awake ECMO, which avoids avoiding deep sedation and its related complications, and minimal recirculation, if positioned correctly. Despite these advantages, dual-lumen catheters require greater expertise for insertion and have the risk of right atrial perforation in unskilled hands. A dual catheter also requires a skilled intensive care team trained in echo screening echo and point-of-care ultrasound, as the catheter can rotate about its long axis leading to a change in the direction of the return stream.⁸ The catheter used in our patient was an Avalon bi-caval dual lumen catheter. Although not regularly employed in pediatric subjects because of logistic and financial constraints, VV ECMO has been used as a rescue modality in our ICU but only after employing the conventional techniques of PEEP titration and recruitment maneuvers including HFOV.

The role of bedside flexible bronchoscopy has been discussed recently in pediatric patients on ECMO with no major complications during or after the procedure.^9,10 The common indications include clearance of retained secretions, microbiological diagnosis of primary or secondary infections, and checking for airway patency.⁹ There is a reported improvement in lung mechanics post-FFB.¹⁰ We performed FFB in the present case on multiple occasions for microbiological diagnosis and clearance of retained thick secretions. We had no major significant complications during or post-procedure except for thin blood-stained secretions on 2 occasions.

Although the literature recommends early ECMO to be prioritized over proning and other recruitment maneuvers in adults, a meta-analysis has revealed that the literature is riddled with systematic bias in reporting the mortality benefit of ECMO before recruitment maneuvers.¹¹ As a protocol, our unit employs recruitment maneuvers, i.e., a trial of proning and HFOV before ECMO as a rescue. Between January and June 2023, a total of 5 cases of pARDS were treated with VV ECMO with 100% survival. There is a need for more publications and experience sharing by pediatric ECMO providers in India.

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