Effect of extracorporeal carbon dioxide removal on respiratory quotient measured by indirect calorimetry: Unravelling the mystery.

NEW FINDINGS: What is the main observation in this case? Several studies have reported progressive hypoxaemia once extracorporeal carbon dioxide removal is started in patients with hypercapnic respiratory failure, possibly attributable to an altered respiratory quotient. What insights does it reveal? In this quality control report, we show that the respiratory quotient exhibits only minimal alteration when extracorporeal carbon dioxide removal is started and assume that the progressive hypoxaemia is attributable to an increase in intrapulmonary shunt. ABSTRACT: The use of extracorporeal carbon dioxide removal (ECCO2 R) has been proposed in patients with acute respiratory distress syndrome to achieve lung-protective ventilation and in patients with selective hypercapnic respiratory failure. However, several studies have reported progressive hypoxaemia, as expressed by a need to increase the inspired oxygen fraction (Fi O2 ) to maintain adequate oxygenation or by a decrease in the ratio of arterial oxygen tension (Pa O2 ) to Fi O2 once ECCO2 R is started. We present the case of a patient who was admitted to the intensive care unit for a coronavirus disease 2019 pneumonia and who was intubated because of hypercapnic respiratory insufficiency. Extracorporeal carbon dioxide removal was started, and the patient subsequently developed progressive hypoxaemia. To test whether the hypoxaemia was attributable to the ECCO2 R, blood samples were taken in different settings: (1) 'no ECCO2 R', blood flow 150 ml/min with a ECCO2 R gas flow of 0 L/min; and (2) 'with ECCO2 R', blood flow 400 ml/min with gas flow 12 L/min. We measured Pa O2 , alveolar oxygen tension, Pa O2 /Fi O2 , alveolar-arterial oxygen tension difference, arterial carbon dioxide tension and the respiratory quotient (RQ) by indirect calorimetry in each setting. The RQ was 0.60 without ECCO2 R and 0.57 with ECCO2 R. The alveolar oxygen tension was 220.4 mmHg without ECCO2 R and increased to 240.3 mmHg with ECCO2 R, whereas Pa O2 /Fi O2 decreased from 177 to 171. Our study showed only a minimal change in RQ when ECCO2 R was started. We were the first to measure the RQ directly, before and after the initiation of ECCO2 R, in a patient with hypercapnic respiratory failure.

Risk stratification in patients undergoing nonoperating room anesthesia.

PURPOSE OF REVIEW: A growing numerical and complexity of patients requiring nonoperating room anesthesia (NORA) necessitates a multidisciplinary approach of a highly experienced team in a highly technological setting of the cathlab or radiology suite. These requirements are even more magnified in the context of the coronavirus disease 2019 (COVID-19) pandemic. RECENT FINDINGS: This review describes the aspects of risk stratification both in adults and children with respect to patient morphology, airway management, cardiorespiratory function and finally future developments, which could beneficially interfere with imminent management in NORA. Moreover, some particular features related to COVID-19 are also discussed. SUMMARY: Apart from a thorough preoperative assessment, preventive strategies and well-chosen monitoring should be implemented to preclude inadvertent events in sometimes high-risk patients. Timely preventive measures and early recognition of complications could only be achieved by a multidisciplinary cooperating team. In addition, the implementation of safety measurements due to the infectious transmission to both the patients and care givers is crucial.