Low respiratory quotient correlates with high mortality in patients undergoing mechanical ventilation.

OBJECTIVE: Oxygen consumption (VO2), carbon dioxide generation (VCO2), and respiratory quotient (RQ), which is the ratio of VO2 to VCO2, are critical indicators of human metabolism. To seek a link between the patient's metabolism and pathophysiology of critical illness, we investigated the correlation of these values with mortality in critical care patients. METHODS: This was a prospective, observational study conducted at a suburban, quaternary care teaching hospital. Age 18 years or older healthy volunteers and patients who underwent mechanical ventilation were enrolled. A high-fidelity automation device, which accuracy is equivalent to the gold standard Douglas Bag technique, was used to measure VO2, VCO2, and RQ at a wide range of fraction of inspired oxygen (FIO2). RESULTS: We included a total of 21 subjects including 8 post-cardiothoracic surgery patients, 7 intensive care patients, 3 patients from the emergency room, and 3 healthy volunteers. This study included 10 critical care patients, whose metabolic measurements were performed in the ER and ICU, and 6 died. VO2, VCO2, and RQ of survivors were 282 +/- 95 mL/min, 202 +/- 81 mL/min, and 0.70 +/- 0.10, and those of non-survivors were 240 +/- 87 mL/min, 140 +/- 66 mL/min, and 0.57 +/- 0.08 (p = 0.34, p = 0.10, and p < 0.01), respectively. The difference of RQ was statistically significant (p < 0.01) and it remained significant when the subjects with FIO2 < 0.5 were excluded (p < 0.05). CONCLUSIONS: Low RQ correlated with high mortality, which may potentially indicate a decompensation of the oxygen metabolism in critically ill patients.

Continuous and repeat metabolic measurements compared between post-cardiothoracic surgery and critical care patients.

OBJECTIVE: Using a system, which accuracy is equivalent to the gold standard Douglas Bag (DB) technique for measuring oxygen consumption (VO2), carbon dioxide generation (VCO2), and respiratory quotient (RQ), we aimed to continuously measure these metabolic indicators and compare the values between post-cardiothoracic surgery and critical care patients. METHODS: This was a prospective, observational study conducted at a suburban, quaternary care teaching hospital. Age 18 years or older patients who underwent mechanical ventilation were enrolled. RESULTS: We included 4 post-surgery and 6 critical care patients. Of those, 3 critical care patients died. The longest measurement reached to 12 h and 15 min and 50 cycles of repeat measurements were performed. VO2 of the post-surgery patients were 234 ± 14, 262 ± 27, 212 ± 16, and 192 ± 20 mL/min, and those of critical care patients were 122 ± 20, 189 ± 9, 191 ± 7, 191 ± 24, 212 ± 12, and 135 ± 21 mL/min, respectively. The value of VO2 was more variable in the post-surgery patients and the range of each patient was 44, 126, 71, and 67, respectively. SOFA scores were higher in non-survivors and there were negative correlations of RQ with SOFA. CONCLUSIONS: We developed an accurate system that enables continuous and repeat measurements of VO2, VCO2, and RQ. Critical care patients may have less activity in metabolism represented by less variable values of VO2 and VCO2 over time as compared to those of post-cardiothoracic surgery patients. Additionally, an alteration of these values may mean a systemic distinction of the metabolism of critically ill patients.

An Automation System Equivalent to the Douglas Bag Technique Enables Continuous and Repeat Metabolic Measurements in Patients Undergoing Mechanical Ventilation.

PURPOSE: To develop a system that is equivalent to the gold standard Douglas Bag (DB) technique for measuring oxygen consumption (V̇o2), carbon dioxide generation (V̇co2), and respiratory quotient (RQ) and to validate its use in clinical settings. METHODS: This was a prospective, observational study conducted at a suburban, quaternary care teaching hospital. Healthy volunteers and patients 18 years or older who received mechanical ventilation were enrolled. FINDINGS: Data from 3 healthy volunteers and 7 patients were analyzed in this study. The interrater reliability between the automation device and DB methods were 0.999, 0.993, and 0.993 for V̇o2, V̇co2, and RQ, respectively. In healthy volunteers, mean (SD) V̇o2, V̇co2, and RQ measured by DB were 411 (100) mL/min, 288 (79) mL/min, and 0.70 (0.03) at high fraction of inspired oxygen (Fio2) and 323 (46) mL/min, 280 (45) mL/min, and 0.85 (0.05) at normal Fio2, respectively. V̇o2 was significantly higher (P < 0.05) and RQ was lower (P < 0.01) in the high Fio2 group as compared to those in the normal Fio2 group. Values measured by the automation system were 227 (31) mL/min, 141 (18) mL/min, and 0.62 (0.04) at high Fio2 and 209 (25) mL/min, 147 (18) mL/min, and 0.70 (0.06) at normal Fio2, respectively. RQ was significantly lower (P < 0.05) in the high Fio2 group as compared to the normal Fio2 group. We also successfully performed continuous and repeat measurements by using the device. The longest measurement reached 12 hours 15 minutes, including 50 cycles of repeat measurements that are equivalent to the DB technique as described above. IMPLICATIONS: We developed an automation system that enables repeat measurements of V̇o2, V̇co2, and RQ, and the accuracy was equivalent to the DB technique. High Fio2 may decrease RQ because of an increase in V̇o2.

Should high risk patients with concomitant severe aortic stenosis and mitral valve disease undergo double valve surgery in the TAVR era?

BACKGROUND: Significant mitral regurgitation in patients undergoing transcatheter aortic valve replacement (TAVR) is associated with increased mortality. The aim of this study is to determine if surgical correction of both aortic and mitral valves in high risk patients with concomitant valvular disease would offer patients better outcomes than TAVR alone. METHODS: A retrospective analysis of 43 high-risk patients who underwent concomitant surgical aortic valve replacement and mitral valve surgery from 2008 to 2012 was performed. Immediate and long term survival were assessed. RESULTS: There were 43 high-risk patients with severe aortic stenosis undergoing concomitant surgical aortic valve replacement and mitral valve surgery. The average age was 80 ± 6 years old. Nineteen (44%) patients had prior cardiac surgery, 15 (34.9%) patients had chronic obstructive lung disease, and 39 (91%) patients were in congestive heart failure. The mean Society of Thoracic Surgeons Predicted Risk of Mortality for isolated surgical aortic valve replacement for the cohort was 10.1% ± 6.4%. Five patients (11.6%) died during the index admission and/or within thirty days of surgery. Mortality rate was 25% at six months, 35% at 1 year and 45% at 2 years. There was no correlation between individual preoperative risk factors and mortality. CONCLUSIONS: High-risk patients with severe aortic stenosis and mitral valve disease undergoing concomitant surgical aortic valve replacement and mitral valve surgery may have similar long term survival as that described for such patients undergoing TAVR. Surgical correction of double valvular disease in this patient population may not confer mortality benefit compared to TAVR alone.

Impact of Postoperative Hypothermia on Outcomes in Coronary Artery Bypass Surgery Patients.

OBJECTIVES: To determine the impact of postoperative hypothermia on outcomes in coronary artery bypass graft surgery (CABG) patients. DESIGN: A retrospective study was performed on patients who underwent isolated CABG between 2011 and 2014. SETTING: Single-center study at a university hospital. PARTICIPANTS: All patients who underwent isolated CABG with cardiopulmonary bypass between 2011 and 2014. INTERVENTIONS: Patients underwent isolated CABG on cardiopulmonary bypass. MEASUREMENTS AND MAIN RESULTS: Patients were propensity-score matched based on the likelihood of being hypothermic (<36ºC) or normothermic (≥36ºC) on arrival to the cardiac surgery intensive care unit (ICU) from the operating room. Total transfusion requirements, composite in-hospital morbidity and/or mortality endpoint, total hours in the ICU, and length of hospital stay were compared between the 2 groups. Of the 1,030 patients undergoing isolated CABG, 529 (51.3%) were hypothermic on arrival to the ICU. The hypothermic cohort were older, had more females, had lower body mass indices, had lower starting hematocrit values, were cooled to lower temperatures while on cardiopulmonary bypass, and had longer cardiopulmonary bypass runs compared with the normothermic group. Of the 748 patients who were propensity matched, there were no differences in blood and blood product transfusion requirements, mortality and complication rates, time on the ventilator, length of ICU stay, and length of hospital stay between hypothermic and normothermic patients. CONCLUSIONS: Hypothermia at ICU admission after CABG was not associated with increased adverse outcomes, possibly suggesting that complete rewarming before separation from cardiopulmonary bypass may not be essential in all patients.

Outcomes of Patients With Prolonged Intensive Care Unit Length of Stay After Cardiac Surgery.

OBJECTIVE: To determine in-hospital and post-discharge long-term survival in patients with prolonged intensive care unit (ICU) stays after cardiac surgery. DESIGN: Retrospective, cohort study of cardiac surgery patients from May 2007 to June 2012. SETTING: Single-center cardiac surgery ICU. PARTICIPANTS: Patients were grouped according to length of ICU stay: between 1 and 2 weeks, between 2 and 4 weeks, and>4 weeks. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Of 4,963 patients, 3.3%, 1.6%, and 2.9% of patients stayed 1 to 2 weeks, 2 to 4 weeks, and>4 weeks in the ICU, respectively. In-hospital mortality was 11.1%, 26.6%, and 31.0% for patients with 1 to 2 weeks, 2 to 4 weeks, and>4 weeks ICU stay, respectively. Patients with ICU stays between 1 and 2 weeks had 6 months, 1 year, and 2 year survival rates of 84.4%, 80.0%, and 75.3% after discharge, respectively. Patients with ICU stay between 2 and 4 weeks had similar 6 months, 1 year, and 2 year survival rates of 84.7%, 79.9%, and 74.1%, respectively. In contrast, patients with>4 week ICU stays had significantly lower postdischarge survival rates of 63.3%, 56.4%, and 41.1% at 6 months, 1 year, and 2 years, respectively. Postoperative stroke conferred the greatest risk of death within 1 year after discharge (odds ratio 7.6, p = 0.0140). CONCLUSIONS: In-hospital mortality rates post-cardiac surgery correlate with length of ICU stay but appear to plateau after 4 weeks. However, a>4 week ICU length of stay confers a worse long-term outcome post-hospital discharge, especially in patients with postoperative stroke.

Utility of Established Risk Models to Predict Surgical Mortality in Acute Type-A Aortic Dissection.

OBJECTIVE: The objective of this study was to determine the predictive value of 2 established risk models for surgical mortality in a contemporary cohort of patients undergoing repair of acute type-A aortic dissection. DESIGN: Retrospective analysis. SETTING: Single tertiary care hospital. PARTICIPANTS: Seventy-nine consecutive patients undergoing emergent repair of acute type-A aortic dissection between 2008 and 2013. INTERVENTION: All patients underwent emergent repair of acute type-A aortic dissection. MEASUREMENTS AND MAIN RESULTS: The receiver operating characteristic curve was compared for each scoring system. Of the 79 patients undergoing emergent repair of acute type-A aortic dissection, 23 (29.1%) were above the age of 70. Seventeen (21.5%) patients presented with hypotension, 25 (31.6%) presented with limb ischemia, and 10 (12.7%) presented with evidence of visceral ischemia. Overall operative mortality was 16.5%. Increasing age was the only preoperative variable associated with increased operative mortality. The areas under the receiver operating characteristic curve for operative mortality was 0.62 and 0.66 for the scoring systems developed by Rampoldi et al and Centofanti et al, respectively. The area under the receiver operating characteristic curve for operative mortality for age was 0.67. The areas under the receiver operating characteristic curve for operative mortality between the 2 scoring systems and for age were not statistically different. CONCLUSIONS: Existing predictive risk models for acute type-A aortic dissection provide moderate discriminatory power for operative mortality. Age as a single variable may provide equivalent discriminatory power for operative mortality as the established risk models.

Myocardial Infarction Classification on Outcomes in Nonemergent Coronary Artery Bypass Grafting.

BACKGROUND: Although patients with ST elevation myocardial infarctions (STEMIs) are known to have worse outcomes than patients with non-ST elevation myocardial infarctions (NSTEMIs), such differences are not well described in the subset of patients undergoing coronary artery bypass grafting. The purpose of this study is to compare postoperative outcomes of patients undergoing nonemergent coronary artery bypass grafting within 1 week after an STEMI versus NSTEMI. METHODS: A retrospective study was performed on patients undergoing isolated coronary artery bypass grafting between 1 and 7 days from an MI from 2008 to 2012. Postoperative outcomes, including mortality and composite postoperative morbidity for patients with STEMI versus NSTEMI, were compared within each group. RESULTS: Of the 446 patients undergoing nonemergent isolated coronary artery bypass grafting between 1 and 7 days after an MI, 122 patients (27.3%) had an STEMI. The STEMI cohort was younger with less incidence of hypertension than the NSTEMI cohort. However, aside from having a lower incidence of congestive heart failure, STEMI patients had an overall poorer cardiac status than NSTEMI patients. No differences were found in mortality, rates of major complication, length of intensive care unit stay, and length of hospital stay between STEMI and NSTEMI patients. CONCLUSION: Despite differences in preoperative characteristics and pathophysiology of patients undergoing coronary artery bypass grafting between 1 and 7 days after NSTEMI versus STEMI, no difference was found in early surgical outcome. The classification of MI should therefore not influence surgical decision making in such patients.

Impact of Preoperative Prealbumin on Outcomes After Cardiac Surgery.

BACKGROUND: Preoperative malnutrition is increasingly prevalent in patients undergoing cardiac surgery. Although prealbumin is a widely used indicator of nutrition status, its use in the preoperative assessment of patients undergoing cardiac surgery is not well defined. The purpose of this study is to determine the impact of preoperative prealbumin levels on outcomes after cardiac surgery. MATERIALS AND METHODS: Data were prospectively gathered from February 2013 to July 2013 on 69 patients undergoing cardiac surgery. Prealbumin levels were obtained within 24 hours of surgery. Patients were divided into 2 groups based on a prealbumin cutoff value of 20 mg/dL. RESULTS: Of the 69 patients, 32 (46.4%) had a preoperative prealbumin ≤ 20 mg/dL. There was no correlation between prealbumin levels and body mass index (r = -0.13, P = .28). Likewise, there was no correlation between preoperative albumin and prealbumin levels (r = 0.09, P = .44). Nine of 32 (28.1%) patients with low preoperative prealbumin levels had postoperative infections compared with 2 of 37 (5.4%) patients with high prealbumin levels (P = .010). Patients with low prealbumin levels also had increased risk of postoperative intubation for > 12 hours (P = .010). CONCLUSIONS: Patients undergoing cardiac surgery with preoperative prealbumin levels of ≤ 20 mg/dL have an increased risk for postoperative infections and the need for longer mechanical ventilation. If feasible, nutrition optimization of such patients may be considered prior to cardiac surgery.

Propensity-matched analysis of the effect of preoperative intraaortic balloon pump in coronary artery bypass grafting after recent acute myocardial infarction on postoperative outcomes.

INTRODUCTION: There is substantial variability in the preoperative use of intraaortic balloon pumps (IABPs) in patients undergoing coronary artery bypass grafting post myocardial infarction. The objective of this study is to determine the effect of preoperative IABPs on postsurgical outcomes in this subset of patients. METHODS: From 2007 to 2012, 877 patients underwent isolated coronary artery bypass post myocardial infarction. Four hundred and six patients were propensity-score matched based on the likelihood of receiving a preoperative balloon pump. Total blood transfusion requirements, composite in-hospital morbidity and/or mortality end point, total hours in the intensive care unit, and length of hospital stay were compared between the two groups. RESULTS: No significant differences in demographics, preoperative risk factors, intraoperative variables or length of hospital stay were found between patients with and without balloon pumps after propensity score matching. Compared to patients without balloon pumps, a higher percentage of patients with preoperative IABPs required transfusions. Patients with preoperative balloon pumps were more likely to have the composite end point of in-hospital morbidity (24.1% versus 12.8%, P <0.004), and increased hours in the intensive care unit (median hours: 69.0 versus 46.0, P <0.013) as compared to patients without balloon pumps. CONCLUSIONS: The use of preoperative IABPs in patients undergoing isolated coronary artery bypass grafting after myocardial infarction is associated with increased transfusion requirements, increased in-hospital morbidity and longer postoperative intensive care unit stay as compared to patients without IABPs.

Dose-dependent effects of intraoperative low volume red blood cell transfusions on postoperative outcomes in cardiac surgery patients.

OBJECTIVE: To determine the incremental risk associated with each intraoperative red blood cell transfusion in cardiac surgery patients. DESIGN: Retrospective analysis on prospectively collected data. SETTING: Single tertiary care hospital. PARTICIPANTS: Seven hundred forty-five patients undergoing on-pump cardiac surgery between January 2010 and June 2012 who received between 1 and 3 units of red blood cell transfusion intraoperatively. INTERVENTIONS: All patients received between 1 and 3 units of red blood cell transfusions. All transfusions were with leukoreduced blood that had been stored for < 14 days. MEASUREMENTS AND MAIN RESULTS: Postoperative complications and length of intubation were associated with the number of red blood cell units transfused. Transfusion of each additional unit of red blood cells was associated with incrementally worse outcomes. Median length of intubation was 11 hours, 12 hours, and 13 hours in patients receiving 1, 2, and 3 units of red blood cell transfusions, respectively (p < 0.005). Similarly, each additional unit of red blood cell transfusion was associated with increasing postoperative septicemia (0% v 0.35% v 2.29%, p < 0.006) and postoperative pneumonia (0% v 0.70% v 2.29%, p < 0.013). CONCLUSIONS: There is a step-wise increase in length of postoperative intubation with each red blood cell transfusion in patients undergoing cardiac surgery. Each additional unit of intraoperative RBC transfusion also may increase postoperative infectious complications. Thus, even single-unit reductions in red blood cell transfusions may have significant impact on outcomes.

Metastatic meningioma extending into the left atrium through the pulmonary vein.

Left atrial extension of pulmonary tumors through the pulmonary vein is most often associated with primary malignancies and is rarely associated with metastatic disease. We present the first, to our knowledge, reported case of a patient with a history of intracranial meningioma resections presenting with metastatic meningioma to the right lower lobe with extension into the left atrium through the pulmonary vein.

P2Y12 platelet function assay for assessment of bleeding risk in coronary artery bypass grafting.

BACKGROUND: The use of platelet function testing has been advocated to individualize the time needed between discontinuation of P2Y12 inhibitors and coronary artery bypass grafting (CABG). However, the use of specific point-of-care assays to predict bleeding risk in patients on P2Y12 inhibitors prior to CABG has not been fully validated. METHODS: From September 2012 to May 2013, 81 patients on P2Y12 inhibitors underwent isolated CABG. Preoperative level of P2Y12 receptor blockade was measured using the VerifyNow P2Y12 assay. Packed red blood cell (pRBC) and platelet transfusions and postoperative chest tube output were correlated with preoperative P2Y12 reaction units (PRUs). RESULTS: Patients who stopped P2Y12 inhibitors for ≤3 days received significantly more platelet transfusions as compared to those whose inhibitors were stopped for longer (0.71 ± 1.05 units vs. 0.20 ± 0.71 units, p = 0.01). They also had increased postoperative chest tube output (552.5 ± 325.5 mL vs. 399.8 ± 146.5 mL, p = 0.03). There was no significant difference in platelet transfusions and chest tube output between patients whose preoperative PRU value was <250 compared to those whose values were ≥250. pRBC requirements were correlated with preoperative hematocrit and age but not with timing of discontinuation of P2Y12 inhibitors or with PRU levels. CONCLUSIONS: In patients on P2Y12 inhibitors undergoing CABG surgery, discontinuation of P2Y12 inhibitors three days prior to surgery rather than VerifyNow PRU values predicts postoperative bleeding and the need for platelet transfusions. Sole reliance on platelet function testing to determine the timing of surgery for patients on P2Y12 inhibitors should therefore be done with caution.

Acute intramural hematoma of the aorta complicated by spinal cord ischemia.

We present an unusual case of spinal cord ischemia from an acute type B intramural hematoma that was successfully treated with blood pressure elevation and drainage of cerebral spinal fluid.