Acute right heart syndrome: Rescue treatment with inhaled nitric oxide
A 39-year-old female, diagnosed case of chronic kidney disease on maintenance hemodialysis (HD) for the past 9 years with severe PAH secondary to chronic pulmonary thromboembolism (PTE) presented with the complaints of progressive breathlessness and abdominal distension for the past 1 week. Her history was suggestive of Grade III dyspnea with orthopnea. There was no history of fever or cough; blood pressure [BP] 92/46 mmHg, pulse rate [PR] 96/min, respiratory rate [RR] 36/min). Her recent records showed recurrent hypotension during her last few HD sessions.\nConsidering her non-tolerance to HD, it was planned to start her on peritoneal dialysis (PD). During the first cycle of PD, she developed severe hypotension and altered sensorium (after inflow phase). She was then shifted to intensive care unit (ICU) for further management.\nAt presentation to the ICU, she was drowsy, sluggishly responding to verbal commands. Her neck veins were distended. She had respiratory distress, with active accessory muscles of respiration. She had a loud P2, pan systolic murmur. Her abdomen was soft, mildly distended with evidence of free fluid and palpable liver (BP: 70/40 mmHg, PR: 102/min, RR: 30/min, SpO2: 99% on high flow O2 via non-rebreathing mask) Her labs were: Hemoglobin 12.3 g/dl, total leucocyte count 8600/μL, serum sodium 138 mEq/L, serum potassium 6 mEq/L, blood urea nitrogen 63 mg/dl, creatinine 6.0 mg/dl. Arterial blood gas (ABG) revealed hypoxia and hypercarbia with mixed acidosis (pH: 7.189, PaCO2: 60.3 mmHg, pO2: 52.7 mmHg, HCO3: 22.5 mmol/L, BE: 6.54 mmol/L, serum lactate 1.92 mmol/L). D-dimer and fibrin degradation product were high. An echocardiogram revealed markedly dilated right ventricle (RV)/right atrial/inferior vena cava (IVC); moderate tricuspid regurgitation (TR), severe pulmonary arterial hypertension (PAH) with (pulmonary artery systolic pressure [PASP] = 93 mmHg paradoxical septal motion; decreased right ventricular (RV) function and reduced left ventricular (LV) compliance. Work-up for sepsis and acute myocardial ischemia was carried out and was ruled out. Considering her critically ill state, she was not subjected to any radiological investigation to rule out acute pulmonary embolus.\nOn Day 1 of ICU admission, she was managed with high dose inotropes and vasopressors: Infusion nor-adrenaline (1 mcg/kg/min) and infusion dopamine (20 mcg/kg/min), empiric broad spectrum antibiotics, low molecular weight heparin and sustained low efficiency dialysis. By Day 2, her vasopressor requirement increased and infusion vasopressin (0.04 units/min) was added. In view of her poor sensorium, hemodynamic instability and acidosis she was electively intubated and ventilated. Her pre-intubation ABG was pH: 7.18, PaCO2: 60 mmHg, PO2: 66.6 mmHg, HCO3: 21.9 mmol/L, BE: 7.1 mmol/L while post-intubation ABG was pH: 7.29, PaCO2: 36.7 mmHg, PO2: 80.4 mmHg, HCO3: 17.3 mmol/L, BE: 8.3 mmol/L. On Day 3, echocardiography revealed findings similar to Day 1 echocardiography (PASP 95 mmHg). In view of her refractory pulmonary hypertension iNO was started (Day 3) through nitric oxide blender (NOxBOX, Ben font Scientific Ltd. Kent, England) at 5 ppm and then increased to 10 ppm. Her hemodynamic parameters showed a progressively improving trend after initiation of iNO. By 12 h (ICU Day 4) of iNO, vasopressors were tapered down. PD was restarted on Day 5 with cumulative negative balance of 2 L (approx). Blood gasses on Day 5 revealed pH: 7.45, PaCO2: 28.4 mmHg, PO2: 136.2 mmHg, HCO3: 20 mmol/L, BE: 5.3 mmol/L and lactates 1.61 mmol/L. Her follow-up echocardiography showed a significant reduction in PA pressures with PASP measuring 73 mmHg at 48 h and 63 mmHg at 72 h of iNO initiation []. Gradually, her vasopressor were weaned off completely and NO was withdrawn after 72 h (Day 6). She was extubated the next day and subsequently was maintained on non-invasive ventilation with inspiratory positive airway pressure of 12 mmHg, expiratory positive airway pressure of 4 mmHg. She was shifted out of ICU on Day 10. Throughout the ICU stay the methemoglobin levels were < 1%, as measured by the co-oximetry test.