brain) and displays a number (rSO2 ) that varies with local oxygen delivery and extraction A decrease in NIRS rSO2 has been correlated with a fall in local tissue perfusion in animal models of shock, decreased cardiac output in infants following cardiac surgery, and predicted fluid responsiveness in dehydrated children FLUID-REFRACTORY AND CATECHOLAMINE-RESISTANT SHOCK Fluid-refractory, catecholamine-resistant shock is the persistence of insufficient tissue perfusion despite at least 60 mL/kg of fluid resuscitation and epinephrine or norepinephrine ≥1 μg/kg/min Such patients are at risk for worse outcomes than those who respond to fluid and/or low-dose vasoactive support The European Society of Paediatric and Neonatal Intensive Care validated a modified definition of refractory septic shock as high vasoactive support, myocardial dysfunction, and arterial lactate >8 mmol/L, which portended a mortality of 60.3% compared to only 2.2% without these features Principles of management for children with refractory shock include treatment of reversible etiologies, combination vasoactive drug therapy, reducing metabolic demand through mechanical ventilation, stress-dose corticosteroid therapy for patients with absolute adrenal insufficiency, and extracorporeal membrane oxygenation (ECMO) support In addition, there is increasing interest in the potential of adjunctive metabolic therapies, such as thiamine and vitamin C, to treat refractory shock, although at this point, these remain investigational therapies Reversible Etiologies Treatment of reversible etiologies includes relieving causes of obstructive shock (tamponade, pneumothorax), prostaglandins for a closing ductus arteriosus, controlling hemorrhage (often requires surgical intervention), relieving intra-abdominal hypertension through drainage of ascites or surgery, and specific therapy for anaphylaxis Identification and removal of an infectious source (e.g., infected catheter, empyema, abdominal abscess) may also enhance resuscitative efforts in septic shock Mechanical Ventilation Sedation and endotracheal intubation reduce the work of breathing which can divert cardiac output away from the muscles of respiration and improve perfusion to other organs Of the sedative agents available for intubation, ketamine is generally preferred due to its favorable hemodynamic effects that typically augment cardiac output and blood pressure As several studies have reported adverse outcomes following intubation with etomidate, pediatric septic shock guidelines now recommend against using etomidate in these patients