Page 23 - ANZCP Gazette November 2021

VV ECMO SUPPORT FOR RESPIRATORY FAILURE SECONDARY TO COVID PNEUMONITIS
Ray Miraziz, Chief Perfusionist, CCP FANZCP Westmead Hospital, NSW
In early 2020 Westmead Hospital was assigned to be the principal referral centre for the COVID-19 outbreak for Western Sydney. During this period, coronavirus case numbers remained low, and intensive care beds occupancy did not exceed their capacity. However, in March 2020, Westmead Hospital did treat a patient for respiratory failure secondary to COVID pneumonitis on veno-venous ECMO. This was the first patient to be supported on VV-ECMO in Australia following type-1 respiratory failure secondary to COVID-19 pneumonitis.
This patient’s treatment during prolonged hospitalisation was complicated by significant airway bleeding and the inability to mechanically ventilate, resulting in ECMO support and proning whilst on ECMO. Throughout her care we were challenged with PPE shortages, an oxygenator change-out, proning, and transfers to CT for scanning. She also developed acute renal failure and multi-organ failure requiring dialysis – and hypercalcaemia. Despite these challenges she was successfully decannulated after 42 days on ECMO and discharged from ICU after 81 days and left the hospital after 107 days. She had a total weight loss of 12 Kg after her diagnosis of COVID -19.
This patient was a 55-year-old, 151 cm, 61 Kg female, non- smoker, returning traveller from the Philippines with a past medical history of mild asthma, sleep apnoea and type 2 diabetes mellitus. She presented at Mount Druitt hospital in Sydney with increasing lethargy and fevers up to 42 0C. Her diabetic condition had been well controlled with prescribed oral hypoglycaemics. Otherwise, she was relatively healthy.
Nasopharyngeal swabs obtained at the time of hospital presentation were positive by PCR for SARS-Cov-2. She was transferred to Westmead for treatment. A Chest CT scan indicated bilateral patchy air space infiltrate with scattered ground glass density and subpleural confluent consolidation – consistent with a diagnosis of COVID-19.
On days 4–9 of hospitalisation, her respiratory status deteriorated, and she was transferred to ICU for intubation and lung protective ventilation. Her metabolic status continued to deteriorate despite a high PEEP ventilator setting. Proning was considered during this period but was ruled out due to her abdominal adiposity. She was then referred for ECMO.
On day 10 of her admission, ECMO cannulation was carried out via a femoro-femoral approach using a 23 French Maquet access and 21 French Maquet return cannulae. At the time of cannulation, transesophageal echocardiography (TOE) revealed a thrombus that had transitioned through the right atrium. This was treated with Clexane for venous thromboembolism (VTE) prophylaxis. There was an immediate improvement in patient’s haemodynamic and right ventricular function.
On days 11–14 on VV-ECMO, airway bleeding was leading to a complete proximal airway occlusion. The Heparin infusion was ceased and she was treated with nebulised Tranexamic acid (TXA). Thrombus removal was successful following bronchoscopy.
By days 17–18 on VV-ECMO, her airway bleed had stabilised, and prone ventilation was commenced aiming to facilitate ongoing lung recruitment. By the fifth cycle of proning, a chest X-ray demonstrated an improvement in the aeration of lung fields. Scheduled proning was a challenge due to staff availability. A total of eight staff members per prone were required. This was repeated twice a day for almost 10 days.
Full PPE is a requirement when attending to all COVID patients, Communication between team members while attending her care was also difficult in this gear. Around this period, our hospital experienced P2/N95 mask and PPE shortages due to mandatory mask fitting and correct practice of donning and doffing. Some staff resorted to making their own face shields by securing the plastic shields on sweat bands.
By day 23 on VV ECMO, our patient developed persistently high calcium levels. Blood parathyroid and thyroid hormones were tested, including Vitamin D concentrations which were all found to be normal. This unexplained elevated calcium levels were thought to be secondary to prolonged bed rest and immobilisation. Heparin induced osteoclasts bone resorption was also thought to be a probable cause. Hypercalcaemia was treated with Calcitonin and normalised after seven days.
On days 28–30 of VV ECMO, a haemolysis screen revealed signs of a failing membrane oxygenator due to elevated d-dimers, lactate dehydrogenase, bilirubin, plasma free Hb, along with falling fibrinogen levels. Despite adequate sweep gas requirements, normal transmembrane pressures, confirmed pre and post membrane blood gases, and minimal clots evident on the oxygenator – along with a prolonged ECMO support of 28 days (that was reaching the manufacturers recommendation of use during support), and with the uncertainty of remaining length of support during her treatment, the decision was made for a membrane change-out. This was conducted on 30th day uneventfully. This change-out was scheduled during reasonable hours due to maximum staffing availability.
By day 38 of VV-ECMO support, our patient returned a second negative for the COVID test and wean studies were commenced. The first wean study lasted one hour followed by a sudden cardiac arrest of unclear cause. Further wean studies continued for 11 days before the final trial of decreased ECMO sweep gas flow for 27 hours with stable gas exchange prior to decannulation.
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