Anaerobic Lactate Production Is Associated With Decreased Microcirculatory Blood Flow and Decreased Mitochondrial Respiration Following Cardiovascular Surgery With Cardiopulmonary Bypass.

OBJECTIVES: Quantify the relationship between perioperative anaerobic lactate production, microcirculatory blood flow, and mitochondrial respiration in patients after cardiovascular surgery with cardiopulmonary bypass. DESIGN: Serial measurements of lactate-pyruvate ratio (LPR), microcirculatory blood flow, plasma tricarboxylic acid cycle cycle intermediates, and mitochondrial respiration were compared between patients with a normal peak lactate (≤ 2 mmol/L) and a high peak lactate (≥ 4 mmol/L) in the first 6 hours after surgery. Regression analysis was performed to quantify the relationship between clinically relevant hemodynamic variables, lactate, LPR, and microcirculatory blood flow. SETTING: This was a single-center, prospective observational study conducted in an academic cardiovascular ICU. PATIENTS: One hundred thirty-two patients undergoing elective cardiovascular surgery with cardiopulmonary bypass. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients with a high postoperative lactate were found to have a higher LPR compared with patients with a normal postoperative lactate (14.4 ± 2.5 vs. 11.7 ± 3.4; p = 0.005). Linear regression analysis found a significant, negative relationship between LPR and microcirculatory flow index (r = -0.225; ß = -0.037; p = 0.001 and proportion of perfused vessels: r = -0.17; ß = -0.468; p = 0.009). There was not a significant relationship between absolute plasma lactate and microcirculation variables. Last, mitochondrial complex I and complex II oxidative phosphorylation were reduced in patients with high postoperative lactate levels compared with patients with normal lactate (22.6 ± 6.2 vs. 14.5 ± 7.4 pmol O2/s/106 cells; p = 0.002). CONCLUSIONS: Increased anaerobic lactate production, estimated by LPR, has a negative relationship with microcirculatory blood flow after cardiovascular surgery. This relationship does not persist when measuring lactate alone. In addition, decreased mitochondrial respiration is associated with increased lactate after cardiovascular surgery. These findings suggest that high lactate levels after cardiovascular surgery, even in the setting of normal hemodynamics, are not simply a type B phenomenon as previously suggested.

Percutaneous Venopulmonary Extracorporeal Membrane Oxygenation as Bridge to Lung Transplantation.

Mechanical circulatory support (MCS) as a bridge to lung transplant is an infrequent but accepted pathway in patients who have refractory end-stage pulmonary failure. The American Association of Thoracic Surgeons Expert Consensus Guidelines, published in 2023, recommends venovenous (VV) extracorporeal membrane oxygenation (ECMO) as the initial configuration for those patients who have failed conventional medical therapy, including mechanical ventilation, while waiting for lung transplantation and needing MCS. Alternatively, venoarterial (VA) ECMO can be used in patients with acute right ventricular failure, hemodynamic instability, or refractory respiratory failure. With the advancement in percutaneous venopulmonary (VP) ECMO cannulation techniques, this option is becoming an attractive configuration as bridge to lung transplantation. This configuration enhances stability of the right ventricle, prevents recirculation with direct introduction of pulmonary artery oxygenation, and promotes hemodynamic stability during mobility, rehabilitation, and sedation-weaning trials before lung transplantation. Here, we present a case series of eight percutaneous VP ECMO as bridge to lung transplant with all patients mobilized, awake, and successfully transplanted with survival to hospital discharge.

Lung transplant outcomes after acute respiratory distress syndrome requiring extracorporeal life support: Lessons from the COVID-19 pandemic.

OBJECTIVE: Lung transplant for acute respiratory distress syndrome in patients supported with extracorporeal membrane oxygenation was rare before 2020, but was rapidly adopted to rescue patients with COVID-19 with lung failure. This study aims to compare the outcomes of patients who underwent lung transplant for COVID-associated acute respiratory distress syndrome and non-COVID acute respiratory distress syndrome, and to assess the impact of type and duration of extracorporeal membrane oxygenation support on survival. METHODS: Using the United Network for Organ Sharing database, we identified 311 patients with acute respiratory distress syndrome who underwent lung transplant from 2007 to 2022 and performed a retrospective analysis of the patients who required extracorporeal membrane oxygenation preoperatively, stratified by COVID-associated acute respiratory distress syndrome and non-COVID acute respiratory distress syndrome listing diagnoses. The primary outcome was 1-year survival. Secondary outcomes included the effect of type and duration of extracorporeal membrane oxygenation on survival. RESULTS: During the study period, 236 patients with acute respiratory distress syndrome and preoperative extracorporeal membrane oxygenation underwent lung transplant; 181 patients had a listing diagnosis of COVID-associated acute respiratory distress syndrome (77%), and 55 patients had a listing diagnosis of non-COVID acute respiratory distress syndrome (23%). Patients with COVID-associated acute respiratory distress syndrome were older, were more likely to be female, had higher body mass index, and spent longer on the waitlist (all P < .02) than patients with non-COVID acute respiratory distress syndrome. The 2 groups had similar 1-year survival (85.8% vs 81.1%, P = .2) with no differences in postoperative complications. Patients with COVID-associated acute respiratory distress syndrome required longer times on extracorporeal membrane oxygenation pretransplant (P = .02), but duration of extracorporeal membrane oxygenation support was not a predictor of 1-year survival (P = .2). CONCLUSIONS: Despite prolonged periods of pretransplant extracorporeal membrane oxygenation support, selected patients with acute respiratory distress syndrome can undergo lung transplant safely with acceptable short-term outcomes. Appropriate selection criteria and long-term implications require further analysis.

Extracorporeal Carbon Dioxide Removal to De-escalate Venovenous Extracorporeal Membrane Oxygenation in Severe COVID-19 Acute Respiratory Distress Syndrome.

OBJECTIVES: In a subset of patients with COVID-19 acute respiratory distress syndrome (ARDS), there is a need for extracorporeal membrane oxygenation (ECMO) for pulmonary support. The primary extracorporeal support tool for severe COVID-19 ARDS is venovenous (VV) ECMO; however, after hypoxemic respiratory failure resolves, many patients experience refractory residual hypercarbic respiratory failure. Extracorporeal carbon dioxide removal (ECCO2R) for isolated hypercarbic type II respiratory failure can be used in select cases to deescalate patients from VV ECMO while the lung recovers the ability to exchange CO2. The objective of this study was to describe the authors' experience in using ECCO2R as a bridge from VV ECMO. DESIGN: Hemolung Respiratory Assist System (RAS) is a commercially available (ECCO2R) device, and the United States Food and Drug Administration accelerated its use under its Emergency Use Authorization for the treatment of refractory hypercarbic respiratory failure in COVID-19-induced ARDS. This created an environment in which selected and targeted mechanical circulatory support therapy for refractory hypercarbic respiratory failure could be addressed. This retrospective study describes the application of Hemolung RAS as a VV ECMO deescalation platform to treat refractory hypercarbic respiratory failure after the resolution of hypoxemic COVID-19 ARDS. SETTING: A quaternary-care academic medical center, single institution. PARTICIPANTS: Patients with refractory hypercarbic respiratory failure after COVID-19 ARDS who were previously supported with VV ECMO. MEASUREMENTS AND MAIN RESULTS: Twenty-one patients were placed on ECCO2R after VV ECMO for COVID-19 ARDS. Seventeen patients successfully were transitioned to ECCO2R and then decannulated; 3 patients required reescalation to VV ECMO secondary to hypercapnic respiratory failure, and 1 patient died while on ECCO2R. Five (23.8%) of the 21 patients were transitioned off of VV ECMO to ECCO2R, with a compliance of <20 (mL/cmH2O). Of these patients, 3 with low compliance were reescalated to VV ECMO. CONCLUSIONS: Extracorporeal carbon dioxide removal can be used to continue supportive methods for patients with refractory type 2 hypercarbic respiratory failure after COVID-19 ARDS for patients previously on VV ECMO. Patients with low compliance have a higher rate of reescalation to VV ECMO.

Transaortic TAVR and Mitral Repair Under Deep Hypothermic Circulatory Arrest in a Porcelain Aorta Patient.

Vascular and valvular calcifications, commonly seen in renal patients, increase operative mortality and can preclude conventional valvular management. We show a novel approach to treat aortic stenosis and degenerative mitral regurgitation under hypothermic circulatory arrest in a hemodialysis patient with aortic, mitral disease and porcelain aorta with surgical and transcatheter contraindications.

Placement of Temporary Left Ventricular Assist Device Using Monitored Anesthesia Care and Regional Anesthesia.

Patients with advanced cardiogenic shock requiring mechanical circulatory support are uniquely susceptible to clinical deterioration. Limiting physiologic perturbations via avoidance of general anesthesia and endotracheal intubation by awake Impella 5.5 placement is safe and may represent a novel strategy in mechanical circulatory support initiation among patients in cardiogenic shock. (Level of Difficulty: Intermediate.).

A different approach to teaching pre-clerkship students physical diagnosis: standardized patient instructor-senior medical student teaching teams.

BACKGROUND: Faculty have traditionally taught the physical examination (PE) to novice medical students (pre-clerkship students.), despite recruiting and cost issues and problems standardizing their approach. ACTIVITY: We present a model using standardized patient instructor (SPI)-fourth year medical student (MS4) teams to teach PE to pre-clerkship students, leveraging the benefits of co-teaching and peer-assisted learning. RESULTS: Surveys of pre-clerkship students, MS4s and SPIs indicate positive perceptions of the program, including MS4s reporting significant growth in their professional identities as educators. Pre-clerkship students' performance on the spring clinical skills exams was equivalent to or better than their peer performance pre-program implementation. IMPLICATIONS: SPI-MS4 teams can effectively teach novice students the mechanics and clinical context of the beginners' physical exam.

Low postoperative perfused vessel density is associated with increased soluble endothelial cell adhesion molecules during circulatory shock after cardiac surgery.

INTRODUCTION: Microcirculatory dysfunction after cardiovascular surgery is associated with significant morbidity and worse clinical outcomes. Abnormal capillary blood flow can occur from multiple causes, including cytokine-mediated vascular endothelial injury, microthrombosis, and an inadequate balance between vasoconstriction and vasodilation. In response to proinflammatory cytokines, endothelial cells produce cellular adhesion molecules (CAMs) which regulate leukocyte adhesion, vascular permeability, and thus can mediate tissue injury. The relationship between changes in microcirculatory flow during circulatory shock and circulating adhesion molecules is unclear. The objective of this study was to compare changes in plasma soluble endothelial cell adhesion molecules (VCAM-1, ICAM-1, and E-Selectin) in patients with functional derangements in microcirculatory blood flow after cardiovascular surgery. METHODS: Adult patients undergoing elective cardiac surgery requiring cardiopulmonary bypass who exhibited postoperative shock were enrolled in the study. Sublingual microcirculation imaging was performed prior to surgery and within 2 h of ICU admission. Blood samples were taken at the time of microcirculation imaging for biomarker analysis. Plasma soluble VCAM-1, ICAM-1, and E-selectin in addition to plasma cytokines (IL-6, IL-8, and IL-10) were measured by commercially available enzyme-linked immunoassay. RESULTS: Of 83 patients with postoperative shock who were evaluated, 40 patients with clinical shock had a postoperative perfused vessel density (PVD) >1 SD above (High PVD group = 28.5 ± 2.3 mm/mm2, n = 20) or below (Low PVD = 15.5 ± 2.0 mm/mm2, n = 20) the mean postoperative PVD and were included in the final analysis. Patient groups were well matched for comorbidities, surgical, and postoperative details. Overall, there was an increase in postoperative plasma VCAM-1 and E-Selectin compared to preoperative levels, but there was no difference between circulating ICAM-1. When grouped by postoperative microcirculation, patients with poor microcirculation were found to have increased circulating VCAM-1 (2413 ± 1144 vs. 844 ± 786 ng/mL; p < 0.0001) and E-Selectin (242 ± 119 vs. 87 ± 86 ng/mL; p < 0.0001) compared to patients with increased microcirculatory blood flow. Microcirculatory flow was not associated with a difference in plasma soluble ICAM-1 (394 ± 190 vs. 441 ± 256; p = 0.52). CONCLUSIONS: Poor postoperative microcirculatory blood flow in patients with circulatory shock after cardiac surgery is associated with increased plasma soluble VCAM-1 and E-Selectin, indicating increased endothelial injury and activation compared to patients with a high postoperative microcirculatory blood flow. Circulating endothelial cell adhesion molecules may be a useful plasma biomarker to identify abnormal microcirculatory blood flow in patients with shock.

Technical considerations for percutaneous pulmonary artery cannulation for mechanical circulatory support.

Objectives: Percutaneous pulmonary artery cannulas, used as inflow for left ventricular venting or as outflow for right ventricular mechanical circulatory support, are easily and rapidly deployable with transesophageal and fluoroscopic guidance. Methods: We chose to review our institutional and technical experience with all right atrium to pulmonary artery cannulations. Results: Based on the review, we describe 6 right atrium to pulmonary artery cannulation strategies. They are divided into total right ventricular assist support, partial right ventricular assist support, and left ventricular venting. A single limb cannula or a dual lumen cannula can be used for right ventricular support. Conclusions: In the right ventricular assist device configuration, percutaneous cannulation may prove beneficial in cases of isolated right ventricular failure. Conversely, pulmonary artery cannulation can be used for left ventricular venting as drainage to a cardiopulmonary bypass or extracorporeal membrane oxygenation circuit. This article can be used as a reference for the technical aspects of cannulation, decision-making in patient selection, and management of patients in these clinical scenarios.

Oxygenated right ventricular assist device as part of veno-venopulmonary extracorporeal membrane oxygenation to support the right ventricle and pulmonary vasculature.

COVID-19 infection can lead to severe acute respiratory distress syndrome (ARDS), right ventricular (RV) failure and pulmonary hypertension. Venovenous extracorporeal membrane oxygenation (V-V ECMO) has been used for patients with refractory hypoxemia. More recently dual-lumen right atrium to pulmonary artery oxygenated right ventricular assist devices (Oxy-RVAD) have been utilized in the severe medical refractory COVID ARDS setting. Historically, animal data has demonstrated that high continuous non-pulsatile RVAD flows, leading to unregulated and unprotected circulation through the pulmonary vessels is associated with an increased risk of pulmonary hemorrhage and increased amount of extravascular lung water. These risks are heightened in the setting of ARDS with fragile capillaries, left ventricular (LV) diastolic failure, COVID cardiomyopathy, and anticoagulation. Concurrently, due to infection, tachycardia, and refractory hypoxemia, high V-V ECMO flows to match high cardiac output are often necessary to maintain systemic oxygenation. Increase in cardiac output without a concurrent increase in VV ECMO flow will result in a higher fraction of deoxygenated blood returning to the right heart and therefore resulting in hypoxemia. Several groups have suggested using a RVAD only strategy in COVID ARDS; however, this exposes the patients to the risk of pulmonary hemorrhage. We present one of the first known cases using an RV mechanical support, partial flow pulmonary circulation, oxygenated Veno-venopulmonary (V-VP) strategy resulting in RV recovery, total renal recovery, awake rehabilitation, and recovery.

Intracannula Thrombus Formation Associated With Dual Lumen ProtekDuo Cannula in Extracorporeal Membrane Oxygenation (ECMO).

Extracorporeal membrane oxygenation (ECMO) is used in cases of severe respiratory failure refractory to medical management. Use of ECMO is increasing, along with new cannulation strategies including oxygenated right ventricular assist devices (oxy-RVADs). Multiple dual lumen cannulas are now available, which increase the potential for patient mobility and decrease the number of vascular access sites. However, dual lumen, single cannula flow can be limited by adequate inflow, requiring the need for an additional inflow cannula to meet patient demands. This cannula configuration may result in differential flows in the inflow and outflow limbs and altered flow dynamics, increasing the risk of intracannula thrombus. We describe a series of four patients treated with oxy-RVAD for COVID-19-associated respiratory failure complicated by dual lumen ProtekDuo intracannula thrombus.

Topical nitroglycerin to detect reversible microcirculatory dysfunction in patients with circulatory shock after cardiovascular surgery: an observational study.

Persistent abnormalities in microcirculatory function are associated with poor clinical outcomes in patients with circulatory shock. We sought to identify patients with acutely reversible microcirculatory dysfunction using a low-dose topical nitroglycerin solution and handheld videomicroscopy during circulatory shock after cardiac surgery. Forty subjects were enrolled for the study, including 20 preoperative control and 20 post-operative patients with shock. To test whether microcirculatory dysfunction is acutely reversible during shock, the sublingual microcirculation was imaged with incident dark field microscopy before and after the application of 0.1 mL of a 1% nitroglycerin solution (1 mg/mL). Compared to the control group, patients with shock had a higher microcirculation heterogeneity index (MHI 0.33 vs. 0.12, p < 0.001) and a lower microvascular flow index (MFI 2.57 vs. 2.91, p < 0.001), total vessel density (TVD 22.47 vs. 25.90 mm/mm2, p = 0.005), proportion of perfused vessels (PPV 90.76 vs. 95.89%, p < 0.001) and perfused vessel density (PVD 20.44 vs. 24.81 mm/mm2, p < 0.001). After the nitroglycerin challenge, patients with shock had an increase in MFI (2.57 vs. 2.97, p < 0.001), TVD (22.47 vs. 27.51 mm/mm2, p < 0.009), PPV (90.76 vs. 95.91%, p < 0.001), PVD (20.44 vs. 26.41 mm/mm2, p < 0.001), venular RBC velocity (402.2 vs. 693.9 µm/s, p < 0.0004), and a decrease in MHI (0.33 vs. 0.04, p < 0.001. Thirteen of 20 patients showed a pharmacodynamic response, defined as an increase in PVD > 1.8 SD from shock baseline. Hemodynamics and vasoactive doses did not change during the 30-min study period. Our findings suggest a topical nitroglycerin challenge with handheld videomicroscopy can safely assess for localized recruitment of the microcirculatory blood flow in patients with circulatory shock and may be a useful test to identify nitroglycerin responsiveness.

Protocol for the MicroRESUS study: The impact of circulatory shock and resuscitation on microcirculatory function and mitochondrial respiration after cardiovascular surgery.

BACKGROUND: Despite current resuscitation strategies, circulatory shock and organ injury after cardiac surgery occur in 25-40% of patients. Goal-directed resuscitation after cardiac surgery has generated significant interest, but clinical practice to normalize hemodynamic variables including mean arterial pressure, cardiac filling pressures, and cardiac output may not reverse microcirculation abnormalities and do not address cellular dysoxia. Recent advances in technology have made it possible to measure critical components of oxygen delivery and oxygen utilization systems in live human tissues and blood cells. The MicroRESUS study will be the first study to measure microcirculatory and mitochondrial function in patients with circulatory shock and link these findings with clinical outcomes. METHODS AND ANALYSIS: This will be a prospective, observational study that includes patients undergoing elective cardiovascular surgery with cardiopulmonary bypass (CPB). Microcirculation will be quantified with sublingual incident dark field videomicroscopy. Mitochondrial respiration will be measured by performing a substrate-uncoupler-inhibitor titration protocol with high resolution respirometry on peripheral blood mononuclear cells at baseline and serial timepoints during resuscitation and at recovery as a possible liquid biomarker. Plasma samples will be preserved for future analysis to examine endothelial injury and other mechanisms of microcirculatory dysfunction. Thirty-day ventilator and vasopressor-free days (VVFDs) will be measured as a primary outcome, along with sequential organ failure assessment scores, and other clinical parameters to determine if changes in microcirculation and mitochondrial respiration are more strongly associated with clinical outcomes compared to traditional resuscitation targets. DISCUSSION: This will be the first prospective study to examine both microcirculatory and mitochondrial function in human patients with circulatory shock undergoing cardiac bypass and address a key mechanistic knowledge gap in the cardiovascular literature. The results of this study will direct future research efforts and therapeutic development for patients with shock.

First-in-man successful use of the SPECTRUM percutaneous dual-stage right ventricle and right atrium to pulmonary artery ventricular assist device.

BACKGROUND: Over the past decade, several minimally invasive mechanical support devices have been introduced into clinical practice to support the right ventricle (RV). Percutaneous cannulas are easy to insert, minimally invasive, and treat acute RV failure rapidly. In December 2021, the Food and Drug Administration approved a new 31 French dual lumen single cannula for use as a right ventricular assist device. AIMS: Descirbe the use of the new dual lumen percutaneous right ventricular assist device (RVAD) cannula. MATERIAL AND METHODS: Deployment of the RVAD can be done surgically or percutaneously. This cannula, manufactured by Spectrum, is dual staged. It has inflow ports positioned both in the right atrium (RA) as well as the RV for maximal drainage of the right heart. The distal end of the cannula which includes the outflow port is positioned in the pulmonary artery (PA). RESULTS: Deployment of the Spectrum RVAD can be done percutaneously with transesophageal and flouroscopy guidence. Cannulation requires requisite wire skills in order to navigate into the main pulmonary artery. Utilization of this cannula can be done in acute RV failure secondary to ischemia, post cardiotomy shock, acute respiratory failure or other causes of isolated RV failure. DISCUSSION: The dual stage drainage design optimizes venous drainage as well as limits suck-down events. Theoretically, direct RV decompression also decreases RV dilation and wall tension, and facilitates improved transmural pressure gradient to reduce RV strain. CONCLUSION: Here we describe the first-in-man successful use of the dual-stage RA and RV to PA Spectrum cannula in a patient with severe COVID acute respiratory distress syndrome and acute right ventricular failure, bridged to recovery.

Comprehensive Monitoring in Patients With Dual Lumen Right Atrium to Pulmonary Artery Right Ventricular Assist Device.

Right ventricular assist devices (RVADs) can be used in patients with acute right heart failure. A novel device that has recently been deployed is the right atrium to pulmonary artery (RA-PA) dual lumen single cannula (DLSC). One of the limitations is that it occupies a large proportion of the right ventricular outflow tract and PA; therefore, standard continuous hemodynamic monitoring with a pulmonary artery catheter is commonly not used. Serial echocardiography is pivotal for device deployment, monitoring device position, assessing RV readiness for decannulation, and surveilling for short-term complications. We performed a retrospective case series of 24 patients with RA-PA DLSC RVAD assessing echocardiographic RV progression and vasoactive infusion requirements. The overall survival was 66.6%. The average vasoactive infusion score at the time of cannulation was 24.9 ± 43.9, at decannulation in survivors 4.6 ± 4.9 vs . 25.4 ± 21.5 in nonsurvivors, and 2.7 ± 4.9 at 48 hours post decannulation. On echocardiography, the average visual estimate of RV systolic function encoded (0 = none and 5 = severe) in survivors was 3.9 ± 1.2, 2.8 ± 1.6, 2.5 ± 1.7, and 2.8 ± 1.9, respectively, and in nonsurvivors 3.8 ± 1.6 and 3.4 ± 1.8, respectively. This demonstrated an RV systolic function improvement over time in survivors as opposed to nonsurvivors. This was also demonstrated in RV size visual estimate, respectively. Quantitatively, at the predefined four timepoints, the RV:LV, tricuspid annular plane systolic excursion, and fractional area change all improve over time and there is statistically significant difference in survivors versus nonsurvivors. In this study, we describe a cohort of patients treated with RA-PA DLSC RVAD. We illustrate the critical nature of echocardiographic measures to rate the progression of RV function, improvement in vasoactive infusion requirements, and ventilator parameters with the RA-PA DLSC.

Clinical and Echocardiographic Results of Aortic Valve Replacement in the Failing Ventricle: Do Aortic Stenosis and Aortic Regurgitation Differ?

BACKGROUND: We hypothesized that long-term clinical and echocardiographic recovery of the impaired ventricle from pressure (aortic stenosis [AS]) and volume (aortic regurgitation [AR]) overload would be different after aortic valve replacement (AVR). METHODS: We compared the results of AVR in patients with a preoperative ejection fraction (EF) of 0.35 or less due to AS, AR, or mixed disease. We constructed a mixed-effects model of EF and left ventricular (LV) end-diastolic diameter (LVEDD) to understand ventricular recovery over the short- (in-hospital), intermediate- (3-6 months), and longer- (>24 months) terms. We sought to identify factors associated with clinical and echocardiographic recovery using multivariable analysis. RESULTS: Between July 2011 and 2017, 136 patients with a preoperative EF of 0.35 or less and severe AS (n = 83), severe AR (n = 18), or mixed AS and AR (n = 35) underwent AVR. There were 2 (1.5%) early deaths in the AS group. Survival at 1, 2, and 5 years did not differ between groups. Baseline EF did not differ between the groups but improved with markedly different trajectory and time course in the AS, AR, and mixed groups over time. LVEDD regressed in all patient cohorts, following a different pattern for AS and AR. Baseline EF and LVEDD predicted the long-term fate of the LV but did not determine survival. We identify factors associated with long-term survival. CONCLUSIONS: The pattern of LV recovery appears to be early in AS and delayed in AR. Baseline clinical factors, rather than echocardiographic status of the LV, appear to determine late survival.

Low Microcirculatory Perfused Vessel Density and High Heterogeneity are Associated With Increased Intensity and Duration of Lactic Acidosis After Cardiac Surgery with Cardiopulmonary Bypass.

INTRODUCTION: Lactic acidosis after cardiac surgery with cardiopulmonary bypass is common and associated with an increase in postoperative morbidity and mortality. A number of potential causes for an elevated lactate after cardiopulmonary bypass include cellular hypoxia, impaired tissue perfusion, ischemic-reperfusion injury, aerobic glycolysis, catecholamine infusions, and systemic inflammatory response after exposure to the artificial cardiopulmonary bypass circuit. Our goal was to examine the relationship between early abnormalities in microcirculatory convective blood flow and diffusive capacity and lactate kinetics during early resuscitation in the intensive care unit. We hypothesized that patients with impaired microcirculation after cardiac surgery would have a more severe postoperative hyperlactatemia, represented by the lactate time-integral of an arterial blood lactate concentration greater than 2.0 mmol/L. METHODS: We measured sublingual microcirculation using incident darkfield video microscopy in 50 subjects on intensive care unit admission after cardiac surgery. Serial measurements of systemic hemodynamics, blood gas, lactate, and catecholamine infusions were recorded each hour for the first 6 h after surgery. Lactate area under the curve (AUC) was calculated over the first 6 h. The lactate AUC was compared between subjects with normal and low perfused vessel density (PVD < 18 mm/mm2), high microcirculatory heterogeneity index (MHI > 0.4), and low vessel-by-vessel microvascular flow index (MFIv < 2.6). RESULTS: Thirteen (26%) patients had a low postoperative PVD, 20 patients (40%) had a high MHI, and 26 (52%) patients had a low MFIv. Patients with low perfused vessel density had higher lactate AUC compared with subjects with a normal PVD (22.3 [9.4-31.0] vs. 2.6 [0-8.8]; P < 0.0001). Patients with high microcirculatory heterogeneity had a higher lactate AUC compared with those with a normal MHI (2.5 [0.1-8.2] vs. 13.1 [3.7-31.1]; P < 0.001). We did not find a difference in lactate AUC when comparing high and low MFIv. CONCLUSION: Low perfused vessel density and high microcirculatory heterogeneity are associated with an increased intensity and duration of lactic acidosis after cardiac surgery with cardiopulmonary bypass.