Comparison of non-invasive to invasive oxygenation ratios for diagnosing acute respiratory distress syndrome following coronary artery bypass graft surgery: a prospective derivation-validation cohort study

Objective: To determine if non-invasive oxygenation indices, namely peripheral capillary oxygen saturation (SpO2)/ fraction of inspired oxygen (Fi O2) and partial pressure of alveolar oxygen (PAO2)/Fi O2 may be used as effective surrogates for the partial pressure of arterial oxygen (PaO2)/Fi O2. Also, to determine the SpO2/Fi O2 and PAO2/Fi O2 values that correspond to PaO2/Fi O2 thresholds for identifying acute respiratory distress syndrome (ARDS) in patients following coronary artery bypass graft (CABG) surgery. Methods: A prospective derivation-validation cohort study in the Open-Heart ICU of an academic teaching hospital. Recorded variables included patient demographics, ventilator settings, chest radiograph results, and SPO2, PaO2, PAO2, SaO2, and Fi O2. Linear regression modeling was used to quantify the relationship between indices. Receiver operating characteristic (ROC) curves were used to determine the sensitivity and specificity of the threshold values. Results: One-hundred seventy-five patients were enrolled in the derivation cohort, and 358 in the validation cohort. The SPO2/Fi O2 and PAO2/Fi O2 ratios could be predicted well from PaO2/Fi O2, described by the linear regression models SPO2/Fi O2 = 71.149 + 0.8PF and PAO2/Fi O2 = 38.098 + 2.312PF, respectively. According to the linear regression equation, a PaO2/Fi O2 ratio of 300 equaled an SPO2/Fi O2 ratio of 311 (R2 0.857, F 1035.742, < 0.0001) and a PAO2/Fi O2 ratio of 732 (R2 0.576, F 234.887, < 0.0001). The SPO2/Fi O2 threshold of 311 had 90% sensitivity, 80% specificity, LR+ 4.50, LR- 0.13, PPV 98, and NPV 42.1 for the diagnosis of mild ARDS. The PAO2/Fi O2 threshold of 732 had 86% sensitivity, 90% specificity, LR+ 8.45, LR- 0.16, PPV 98.9, and NPV 36 for the diagnosis of mild ARDS. SPO2/ Fi O2 had excellent discrimination ability for mild ARDS (AUC ± SE = 0.92 ± 0.017; 95% CI 0.889 to 0.947) as did PAO2/ Fi O2 (AUC ± SE = 0.915 ± 0.018; 95% CI 0.881 to0.942). Conclusions: PaO2 and SaO2 correlated in the diagnosis of ARDS, with a PaO2/Fi O2 of 300 correlating to an SPO2/ Fi O2 of 311 (Sensitivity 90%, Specificity 80%). The SPO2/ Fi O2 ratio may allow for early real-time rapid identification of ARDS, while decreasing the cost, phlebotomy, blood loss, pain, skin breaks, and vascular punctures associated with serial arterial blood gas measurements

Dehiscence and embolization of CorMatrix tricuspid valve replacement in the setting of infective endocarditis: a case report

Background:Due to increased morbidity and mortality, prosthetic valve infective endocarditis (IE) with dehiscence requires urgent intervention. Early identification and therapy may prevent embolization.Case summary:A 27-year-old Caucasian woman with a history of hepatitis C, intravenous drug abuse, and tricuspid valve (TV) replacement was admitted for recurrent IE. She was found to have bacteraemia and fungaemia, and empiric antibiotics were initiated. Transthoracic echocardiogram (TTE) revealed a mobile -˜mass" on the TV and dehiscence. The patient developed cardiogenic shock and repeat TTE showed a ruptured TV and absence of the -˜mass", suspicious of embolization. She underwent emergent surgery with TV replacement using a Biocor valve and retrieval of the old CorMatrix valve found in the right mid pulmonary artery (PA). The patient was successfully weaned off inotropic agents and completed a prolonged course of antibiotics and anti-fungals.Discussion:The multi-disciplinary decision on timing of surgical intervention was challenging, especially due to ongoing mycobacterial infection that increased operative risk. With clinical deterioration, urgent surgery was performed revealing an embolized prosthetic valve in the PA. New surgical options for TV replacement in IE with extracellular-based material have shown promising outcomes with little reported data of long term complications. This case demonstrates a rare occurrence of embolized CorMatrix TV and highlights the challenge in timing of appropriate surgical intervention in a septic patient with thrombocytopenia