Dalia A. Banks

Cardiac Output Determination From Endotracheally Measured Impedance Cardiography: Clinical Evaluation of Endotracheal Cardiac Output Monitor

OBJECTIVES To evaluate the accuracy, precision, and trending of a new endotracheally sourced impedance cardiography-based cardiac output (CO) monitor (ECOM; ConMed Corp, Irvine, CA). SETTING Two university hospitals. PARTICIPANTS Thirty patients scheduled for elective coronary artery bypass graft (CABG) surgery. INTERVENTIONS All patients received a pulmonary artery catheter (PAC), arterial catheter, endotracheal CO monitor (ECOM), endotracheal intubation, and transesophageal echocardiographic monitoring. ECOM CO was compared with CO measured with pulmonary artery thermodilution, and left ventricular CO measured with transesophageal echocardiography. MEASUREMENTS One hundred forty-five pairs of triplicate CO measurements using intermittent bolus pulmonary artery thermodilution (TD) and ECOM were compared at 5 distinct time points: postinduction, postinduction passive leg raise, poststernotomy, post-CABG completion, and post-chest closure. Eighty-seven pairs of triplicate CO measurements using transesophageal echocardiography were obtained at 3 time points: postinduction, post-CABG completion, and post-chest closure and compared with ECOM- and PA-derived CO measurements. The measurements at each time point were compared by using Bland-Altman and polar plot analyses. RESULTS The mean CO ranged from 2.16 to 9.41 L/min. ECOM CO, compared with TD CO, revealed a bias of 0.02 L/min, 95% limits of agreement of -2.26 to 2.30 L/min, and a percent error of 50%. ECOM CO showed trending with TD CO with 91% and 99% of values within 0.5L/min and 1 L/min limits of agreement, respectively. ECOM CO, compared with TEE CO, revealed a bias of -0.25 L/min, 95% limits of agreement of -2.41 to 1.92 L/min, and a percent error of 48%. ECOM CO showed trending with TEE CO with 83% and 95% of values within 0.5L/min and 1 L/min limits of agreement, respectively. CONCLUSION ECOM CO shows an acceptable bias with wide limits of agreement and a large percent error when compared with TD CO or TEE CO; however, it shows acceptable trending of CO to both modalities in patients undergoing cardiac surgery. Further studies are required to evaluate ECOM in other patient populations and clinical situations.

Pulmonary Endarterectomy Part II. Operation, Anesthetic Management, and Postoperative Care

Chronic thromboembolic pulmonary hypertension (CTEPH) results from recurrent or incomplete resolution of pulmonary embolism. CTEPH is much more common than generally appreciated. Although pulmonary embolism (PE) affects a large number of Americans, chronic pulmonary thromboembolic hypertension remains underdiagnosed. It is imperative that all patients with pulmonary hypertension (PH) be screened for the presence of CTEPH since this form of PH is potentially curable with pulmonary endarterectomy (PEA) surgery. The success of this procedure depends greatly on the collaboration of a multidisciplinary team approach that includes pulmonary medicine, cardiothoracic surgery, and cardiac anesthesiology. This review, based on the experience of more than 3000 pulmonary endarterectomy surgeries, is divided into 2 parts. Part I focuses on the clinical history and pathophysiology, diagnostic workup, and intraoperative echocardiography. Part II focuses on the surgical approach, anesthetic management, postoperative care, and complications.

Pulmonary Endarterectomy Part I. Pathophysiology, Clinical Manifestations, and Diagnostic Evaluation of Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) results from recurrent or incomplete resolution of pulmonary embolism. CTEPH is much more common than generally appreciated. Although pulmonary embolism (PE) affects a large number of Americans, chronic pulmonary hypertension (PH) remains underdiagnosed. It is imperative that all patients with PH be screened for the presence of CTEPH since this form of PH is potentially curable with pulmonary thromboendarterectomy (PTE) surgery. The success of this procedure depends greatly on the collaboration of a multidisciplinary team approach that includes pulmonary medicine, cardiothoracic surgery, and cardiac anesthesiology. This review, based on the experience of more than 3000 pulmonary endarterectomy surgeries, is divided into 2 parts. Part I focuses on the clinical history and pathophysiology, diagnostic workup, and intraoperative echocardiography. Part II focuses on the surgical approach, anesthetic management, postoperative care, and complications.

Case 13--2014: Management of pulmonary hemorrhage after pulmonary endarterectomy with venovenous extracorporeal membrane oxygenation without systemic anticoagulation.

From the *University of California, San Diego, Thornton Hospital, †University of Chicago, Chicago, IL, ‡University of Pittsburgh, Pittsburgh, PA; and §Duke University Medical Center, Durham, NC. Address reprint requests to Brett Cronin, MD, Dept. of Anesthesiology, University of California, San Diego, Thornton Hospital, 9300 Campus Point Drive #7770, La Jolla, CA 92037. E-mail: bcronin@ ucsd.edu

CASE 1--2015: left ventricular assist device insertion in a patient with heparin-induced thrombocytopenia and renal failure.

From the *University of California, San Diego, Sulpizio Cardiovascular Center, LaJolla, CA, †Heart and Diabetes Centre NRW, Ruhr-University Bochum, Bad Oeynhausen, Germany; and ‡Department of Anesthesiology, Queen Fabiola Children’s University Hospital, Brussels, Belgium. Address reprint requests to Sonia Nhieu, MD, University of California, San Diego, Department of Anesthesiology, Thornton Hospital, 9300 Campus Point Drive #7770, LaJolla, CA 92023-7770. E-mail: snhieu@ucsd.edu Cardiac Anesthesia Fellow. UNFRACTIONATED HEPARIN (UFH) is the most widely used intravenous drug in the United States with as many as 60% of hospitalized patients receiving this agent. The incidence of heparin-induced thrombocytopenia (HIT) is approximately 2% of patients who receive UFH. HIT syndrome type II (HIT-II) is an immune-mediated reaction in which serum antibodies against heparin-platelet factor 4 (HPF4) complexes are produced in patients who receive heparin therapy. The reaction typically develops 5 to 10 days after exposure and leads to a decrease in platelet count of 50% or more and a paradoxical hypercoagulable state. No ideal method of anticoagulation exists for patients with HIT. In non-surgical patients requiring anticoagulation and medical management of HIT, approved therapies in the United States are limited to argatroban and lepirudin. Recommendations for anticoagulation for patients with HIT requiring cardiac surgery include delaying surgery until HIT antibodies are negative, administering platelet inhibitors in addition to heparin, or using an alternative anticoagulation strategy. Unfortunately, many patients, especially those requiring cardiac surgery, cannot delay the operation, and an alternative to heparin for intraoperative anticoagulation must be used. The use of cardiopulmonary bypass (CPB) further complicates the situation because of the higher levels of anticoagulation required. Use of bivalirudin for anticoagulation in patients with HIT undergoing cardiac surgery has increased and, in a few small studies, has demonstrated a similar safety and efficacy profile compared to UFH. Bivalirudin is a synthetic, direct thrombin inhibitor made up of twenty amino acids and is approved for patients undergoing percutaneous coronary intervention. Its elimination is predominantly dependent on thrombin active site-mediated proteolytic cleavage, resulting in a short half-life of 25 minutes. Approximately 20% of the drug is excreted unchanged by the kidney, leading to a doubling of the half-life in patients with severe renal impairment. The drug’s safety profile appears unchanged, even with respect to hemorrhagic complications, in patients with moderate impairment of renal function. However, in dialysis-dependent patients, the half-life increases markedly to approximately 3 to 5 hours. While the

CASE 1—2011: The Challenges Posed by a Complicated Pulmonary Thromboendarterectomy

HEN DISCUSSING heart failure, the left ventricle normally takes center stage, and the right ventricle (RV) can become an afterthought. However, in patients diagnosed with chronic thromboembolic pulmonary hypertension (CTEPH), the RV takes the lead role. These patients can present with increased right ventricular oxygen consumption with a concomitant decrease in right ventricular oxygen supply, placing them at high risk for right ventricular ischemia and failure. Fortunately, after a pulmonary thromboendarterectomy (PTE), rightheart hemodynamics greatly improve in most CTEPH patients, and right ventricular perfusion is no longer an issue. The authors, however, present a case discussing the management of a patient with severe pulmonary hypertension (PH) undergoing a PTE with residual severe PH even after their PTE.

Efficacy of a Low–Tidal Volume Ventilation Strategy to Prevent Reperfusion Lung Injury after Pulmonary Thromboendarterectomy

RATIONALE Reperfusion lung injury is a postoperative complication of pulmonary thromboendarterectomy that can significantly affect morbidity and mortality. Studies in other postoperative patient populations have demonstrated a reduction in acute lung injury with the use of a low-tidal volume (Vt) ventilation strategy. Whether this approach benefits patients undergoing thromboendarterectomy is unknown. OBJECTIVES We sought to determine if low-Vt ventilation reduces reperfusion lung injury in patients with chronic thromboembolic pulmonary hypertension undergoing thromboendarterectomy. METHODS Patients undergoing thromboendarterectomy at one center were randomized to receive either low (6 ml/kg predicted body weight) or usual care Vts (10 ml/kg) from the initiation of mechanical ventilation in the operating room through Postoperative Day 3. The primary endpoint was the onset of reperfusion lung injury. Secondary outcomes included severity of hypoxemia, days on mechanical ventilation, and intensive care unit and hospital lengths of stay. MEASUREMENTS AND MAIN RESULTS A total of 128 patients were enrolled and included in the analysis; 63 were randomized to the low-Vt group and 65 were randomized to the usual care group. There was no statistically significant difference in the incidence of reperfusion lung injury between groups (32%, n=20 in the low-Vt group vs. 23%, n=15 in the usual care group; P=0.367). Although differences were noted in plateau pressures (17.9 cm H2O vs. 20.1 cm H2O, P<0.001) and peak inspiratory pressures (20.4 cm H2O vs. 23.0 cm H2O, P<0.001) between the low-Vt and usual care groups, respectively, mean airway pressures, PaO2/FiO2, days on mechanical ventilation, and ICU and hospital lengths of stay were all similar between groups. CONCLUSIONS In patients with chronic thromboembolic pulmonary hypertension undergoing pulmonary thromboendarterectomy, intra- and postoperative ventilation using low Vts (6 mg/kg) compared with usual care Vts (10 mg/kg) does not reduce the incidence of reperfusion lung injury or improve clinical outcomes. Clinical trial registered with www.clinicaltrials.gov (NCT00747045).

Intraoperative Three Dimensional Echocardiography Derived Right Ventricular Volumetric Analysis in Chronic Thromboembolic Pulmonary Hypertension Patients Before and After Pulmonary Thromboendarterectomy

OBJECTIVES To assess the change in 3-dimensional (3D) echocardiography-derived right ventricular volumes before and after pulmonary thromboendarterectomy (PTE) and to evaluate the correlation of these variables with right heart catheterization-calculated pulmonary vascular resistance (PVR). SETTING Single university hospitals. PARTICIPANTS Patients undergoing elective PTE surgery between November 2016 and February 2018. METHODS All patients received a pulmonary artery catheter and arterial line, and transesophageal echocardiographic monitoring was performed. Transesophageal echocardiographic monitoring before surgery (pre-PTE) and postsurgery (post-PTE) included comprehensive 2D examinations and 3D right ventricular data set acquisition for offline volumetric analysis. Right ventricular fractional area of change (RVFAC) was measured from a right ventricular-focused midesophageal 4-chamber view. TomTec-Arena 4D RV-Function 2.0 offline software (TomTec Imaging Systems GmbH, Unterschlessheim, Germany) was used to measure right ventricular end diastolic volume (RVEDV), right ventricular end systolic volume (RVESV), and right ventricular ejection fraction (RVEF). Paired t tests were used to evaluate for differences before and after surgery, and echocardiographic variables versus PVR were analyzed with linear regression. RESULTS Forty patients were scheduled for elective PTE surgery; 35 patients had complete hemodynamic profiles and echocardiographic data sets and were included in the evaluation. Mean pulmonary artery pressure decreased from 40 ± 11 to 28 ± 7 mmHg, and PVR decreased from 708 ± 432 to 285 ± 136 dynes*s/cm5 after PTE. RVEDV decreased from 106 ± 43 to 79 ± 35 cm3 (p < 0.001), and RVESV decreased from 77 ± 36 to 59 ± 31 cm3 (p < 0.001). A statistically significant change was not identified in RVEF or RVFAC post-PTE compared with pre-PTE values. All volumetric analyses and RVFAC correlated poorly with PVR (pre-PTE RVEDV correlation to PVR [R2 = 0.004]; post-PTE RVEDV correlation to PVR [R2 = 0.024]). CONCLUSION Even though RVEDV and RVESV displayed a statistically significant change after PTE, this study did not identify a correlation between those variables and PVR. In addition, markers of right ventricular systolic function (eg, RVFAC and RVEF) did not correlate with PVR. Therefore, the authors conclude that even though these echocardiographic measurements quantified a statistically significant change after PVR reduction, they cannot be reliably used as a surrogate marker of success immediately after PTE.

Measures of Blood Hemoglobin and Hematocrit During Cardiac Surgery: Comparison of Three Point-of-Care Devices

OBJECTIVE The primary objective was to compare I-Stat, HemoCue, and RapidLab in measurements of the hemoglobin concentration during cardiac surgeries using cardiopulmonary bypass. DESIGN Prospective analysis. SETTING Single-center, academic, tertiary care cardiovascular center. PARTICIPANTS Thirty-four consecutive patients undergoing cardiac surgery requiring cardiopulmonary bypass. INTERVENTIONS Blood samples have been collected intraoperatively, and the hemoglobin concentration in each sample was measured, or calculated, simultaneously by the 3 point-of-care devices, HemoCue, RapidLab, and I-Stat. MEASUREMENTS AND MAIN RESULTS Correlation coefficients from the regression analysis for HemoCue versus I-Stat, RapidLab versus HemoCue, and RapidLab versus I-Stat were 0.89, 0.96, and 0.88, respectively. Results of the Bland-Altman analysis of the hemoglobin concentration measurements for each device against one another (Fig 1) were as follows: RapidLab versus I-Stat (bias 0.42; 95% confidence interval [CI], -1.05 to 1.89), I-Stat versus HemoCue (bias 0.23; 95% CI, -1.14 to 1.59), and RapidLab versus HemoCue (bias 0.65; 95% CI, -0.17 to 1.47). It appears that I-Stat slightly underestimated the concentration of hemoglobin when compared with both RapidLab and HemoCue. The results of Bland-Altman analysis of each device to a mean Z value (Fig 2) were as follows: RapidLab versus Z (bias 0.36; 95% CI, -0.29 to 1.01), I-Stat versus Z (bias -0.07; CI -0.97 to 0.84), and HemoCue versus Z (bias -0.29; 95% CI, -0.86 to 0.28). Based on the 174 paired samples used for the Pearson moment analysis, the R2 values for I-Stat versus HemoCue, I-Stat versus RapidLab, and RapidLab versus HemoCue were 0.79, 0.80, and 0.87, respectively CONCLUSIONS: These data support the interchangeability of these 3 devices for the intermittent intraoperative point-of-care assessment of hemoglobin concentrations in cardiac surgery patients. It is important, however, to consider the possible pitfalls associated with each device when making a clinical decision to transfuse.

Anesthetic management of the patient undergoing heart transplantation

Cardiac transplantation is the treatment of choice for patients with end-stage heart failure. Over the years, significant advances in patient selection, donor optimization and selection, and optimization of immunosuppression strategies have markedly improved outcomes. In this review, we highlight patient selection, donor management and procurement, heart transplantation procedure, and intraoperative and postoperative management of heart transplants.