Trevor W.R. Lee

Comprehensive Canadian Review of the Off-Label Use of Recombinant Activated Factor VII in Cardiac Surgery

Background— This observational study sought to identify the off-label use pattern of recombinant activated factor VII (rFVIIa) in cardiac surgery and to identify predictors of its effectiveness and risk. Methods and Results— At 18 Canadian centers, 522 nonhemophiliac cardiac surgical patients received rFVIIa during the period 2003 through 2006; data were available, and retrospectively collected, on 503 patients. The median (quartile 1, quartile 3) units of red blood cells transfused from surgery to therapy and in the 24 hours after therapy were 8 (5, 12) and 2 (1, 5), respectively (P<0.0001). Mortality rate was 32%, and mortality or major morbidity rate was 44%. These rates were within expected ranges (mortality, 27% to 35%; mortality or morbidity, 39% to 48%), which were calculated with a separate cohort of cardiac surgical patients who did not receive rFVIIa used as reference. Independent predictors of complications included instability before therapy (multiple inotropes or intra-aortic balloon pump) and increasing red blood cell units transfused before and after therapy. Variables independently associated with nonresponse included abnormal coagulation parameters and >15 red blood cell units transfused before therapy. Conclusions— In Canada, rFVIIa is used primarily when standard interventions have failed to control bleeding. In this setting, rFVIIa is associated with reduced blood product transfusions and, after risk adjustment, does not appear to be associated with increased or decreased complication rates. The effectiveness of the drug may be enhanced if it is given early in the course of refractory blood loss in the setting of adequate amounts of circulating coagulation factors.

High spinal anesthesia for cardiac surgery: Effects on β-adrenergic receptor function, stress response, and hemodynamics

Background This double-blind, randomized, controlled trial examined the effect of high-dose intrathecal bupivacaine in combination with general anesthesia on atrial &bgr;-adrenergic receptor function, the stress response, and hemodynamics during coronary artery bypass graft surgery. Methods Thirty-eight patients were randomized to either control (n = 19) or intrathecal bupivacaine (ITB) groups (n = 19). Patients in the ITB group received 37.5 mg intrathecal hyperbaric bupivacaine before induction of general anesthesia. Control patients received an injection of local anesthetic into the skin and subcutaneous tissues (sham spinal). Comparisons were made between groups with respect to atrial receptor desensitization and down-regulation, in addition to circulating catecholamines and hemodynamics. Results In patients with cardiopulmonary bypass (CPB) times in excess of 1 h, the ITB group had significantly less atrial &bgr;-receptor dysfunction, as measured by maximal isproteronol, 50% maximal isoproterenol, sodium fluoride-stimulated activity, and zinterol stimulation assays of adenylyl cyclase activity (P ≤ 0.02) and &bgr;-adrenergic receptor density (P = 0.02). Serum epinephrine, norepinephrine, and cortisol concentrations were significantly lower in the ITB group, independent of CPB times (P < 0.0001, P < 0.001, and P < 0.05, respectively). ITB patients had a higher cardiac index and a lower pulmonary vascular resistance index in the post-CPB time period (P < 0.01 and P < 0.05, respectively). In the pre-CPB period, mean arterial pressure and systemic vascular resistance index were significantly lower in the ITB group. Conclusions High-dose intrathecal bupivacaine, when combined with general anesthesia, resulted in less &bgr;-receptor dysfunction and a lower stress response during coronary artery bypass graft surgery.

A cardioprotective preservation strategy employing ex vivo heart perfusion facilitates successful transplant of donor hearts after cardiocirculatory death

BACKGROUND Ex vivo heart perfusion (EVHP) has been proposed as a means to facilitate the resuscitation of donor hearts after cardiocirculatory death (DCD) and increase the donor pool. However, the current approach to clinical EVHP may exacerbate myocardial injury and impair function after transplant. Therefore, we sought to determine if a cardioprotective EVHP strategy that eliminates myocardial exposure to hypothermic hyperkalemia cardioplegia and minimizes cold ischemia could facilitate successful DCD heart transplantation. METHODS Anesthetized pigs sustained a hypoxic cardiac arrest and a 15-minute warm ischemic standoff period. Strategy 1 hearts (S1, n = 9) underwent initial reperfusion with a cold hyperkalemic cardioplegia, normothermic EVHP, and transplantation after a cold hyperkalemic cardioplegic arrest (current EVHP strategy). Strategy 2 hearts (S2, n = 8) underwent initial reperfusion with a tepid adenosine-lidocaine cardioplegia, normothermic EVHP, and transplantation with continuous myocardial perfusion (cardioprotective EVHP strategy). RESULTS At completion of EVHP, S2 hearts exhibited less weight gain (9.7 ± 6.7 [S2] vs 21.2 ± 6.7 [S1] g/hour, p = 0.008) and less troponin-I release into the coronary sinus effluent (4.2 ± 1.3 [S2] vs 6.3 ± 1.5 [S1] ng/ml; p = 0.014). Mass spectrometry analysis of oxidized pleural in post-transplant myocardium revealed less oxidative stress in S2 hearts. At 30 minutes after wean from cardiopulmonary bypass, post-transplant systolic (pre-load recruitable stroke work: 33.5 ± 1.3 [S2] vs 19.7 ± 10.9 [S1], p = 0.043) and diastolic (isovolumic relaxation constant: 42.9 ± 6.7 [S2] vs 65.2 ± 21.1 [S1], p = 0.020) function were superior in S2 hearts. CONCLUSION In this experimental model of DCD, an EVHP strategy using initial reperfusion with a tepid adenosine-lidocaine cardioplegia and continuous myocardial perfusion minimizes myocardial injury and improves short-term post-transplant function compared with the current EVHP strategy using cold hyperkalemic cardioplegia before organ procurement and transplantation.

Hearts From DCD Donors Display Acceptable Biventricular Function After Heart Transplantation in Pigs

Cardiac transplantation is in decline, in contrast to other solid organs where the number of solid organ transplants from donors after circulatory death (DCD) is increasing. Hearts from DCD donors are not currently utilized due to concerns that they may suffer irreversible cardiac injury with resultant poor graft function. Using a large animal model, we tested the hypothesis that hearts from DCD donors would be suitable for transplantation. Donor pigs were subjected to hypoxic cardiac arrest (DCD) followed by 15 min of warm ischemia and resuscitation on cardiopulmonary bypass, or brainstem death (BSD) via intracerebral balloon inflation. Cardiac function was assessed through load‐independent measures and magnetic resonance imaging and spectroscopy. After resuscitation, DCD hearts had near normal contractility, although stroke volume was reduced, comparable to BSD hearts. DCD hearts had a significant decline in phosphocreatine and increase in inorganic phosphate during the hypoxic period, with a return to baseline levels after reperfusion. After transplantation, cardiac function was comparable between BSD and DCD groups. Therefore, in a large animal model, the DCD heart maintains viability and recovers function similar to that of the BSD heart and may be suitable for clinical transplantation. Further study is warranted on optimal reperfusion strategies.

A whole blood–based perfusate provides superior preservation of myocardial function during ex vivo heart perfusion

BACKGROUND Ex vivo heart perfusion (EVHP) provides the opportunity to resuscitate unused donor organs and facilitates assessments of myocardial function that are required to demonstrate organ viability before transplantation. We sought to evaluate the effect of different oxygen carriers on the preservation of myocardial function during EVHP. METHODS Twenty-seven pig hearts were perfused ex vivo in a normothermic beating state for 6 hours and transitioned into working mode for assessments after 1 (T1), 3 (T3), and 5 (T5) hours. Hearts were allocated to 4 groups according to the perfusate composition. Red blood cell concentrate (RBC, n = 6), whole blood (RBC+Plasma, n = 6), an acellular hemoglobin-based oxygen carrier (HBOC, n = 8), or HBOC plus plasma (HBOC+Plasma, n = 7) were added to STEEN Solution (XVIVO Perfusion, Goteborg, Sweden) to achieve a perfusate hemoglobin concentration of 40 g/liter. RESULTS The perfusate composition affected the preservation of systolic (T5 dP/dtmax: RBC+Plasma = 903 ± 99, RBC = 771 ± 77, HBOC+Plasma = 691 ± 82, HBOC = 563 ± 52 mm Hg/sec; p = 0.047) and diastolic (T5 dP/dtmin: RBC+Plasma = -574 ± 48, RBC = -492 ± 63, HBOC+Plasma = -326 ± 32, HBOC = -268 ± 22 mm Hg/sec; p < 0.001) function, and the development of myocardial edema (weight gain: RBC+Plasma = 6.6 ± 0.9, RBC = 6.6 ± 1.2, HBOC+Plasma = 9.8 ± 1.7, HBOC = 16.3 ± 1.9 g/hour; p < 0.001) during EVHP. RBC+Plasma hearts exhibited less histologic evidence of myocyte damage (injury score: RBC+Plasma = 0.0 ± 0.0, RBC = 0.8 ± 0.3, HBOC+Plasma = 2.6 ± 0.2, HBOC = 1.75 ± 0.4; p < 0.001) and less troponin-I release (troponin-I fold-change T1-T5: RBC+Plasma = 7.0 ± 1.7, RBC = 13.1 ± 1.6, HBOC+Plasma = 20.5 ± 1.1, HBOC = 16.7 ± 5.8; p < 0.001). Oxidative stress was minimized by the addition of plasma to RBC and HBOC hearts (oxidized phosphatidylcholine compound fold-change T1-T5: RBC+Plasma = 1.83 ± 0.20 vs RBC = 2.31 ± 0.20, p < 0.001; HBOC+Plasma = 1.23 ± 0.17 vs HBOC = 2.80 ± 0.28, p < 0.001). CONCLUSIONS A whole blood-based perfusate (RBC+Plasma) minimizes injury and provides superior preservation of myocardial function during EVHP. The beneficial effect of plasma on the preservation of myocardial function requires further investigation.

Physiologic Changes in the Heart Following Cessation of Mechanical Ventilation in a Porcine Model of Donation After Circulatory Death: Implications for Cardiac Transplantation.

Hearts donated following circulatory death (DCD) may represent an additional source of organs for transplantation; however, the impact of donor extubation on the DCD heart has not been well characterized. We sought to describe the physiologic changes that occur following withdrawal of life‐sustaining therapy (WLST) in a porcine model of DCD. Physiologic changes were monitored continuously for 20 min following WLST. Ventricular pressure, volume, and function were recorded using a conductance catheter placed into the right (N = 8) and left (N = 8) ventricles, and using magnetic resonance imaging (MRI, N = 3). Hypoxic pulmonary vasoconstriction occurred following WLST, and was associated with distension of the right ventricle (RV) and reduced cardiac output. A 120‐fold increase in epinephrine was subsequently observed that produced a transient hyperdynamic phase; however, progressive RV distension developed during this time. Circulatory arrest occurred 7.6±0.3 min following WLST, at which time MRI demonstrated an 18±7% increase in RV volume and a 12±9% decrease in left ventricular volume compared to baseline. We conclude that hypoxic pulmonary vasoconstriction and a profound catecholamine surge occur following WLST that result in distension of the RV. These changes have important implications on the resuscitation, preservation, and evaluation of DCD hearts prior to transplantation.

Avoidance of Profound Hypothermia During Initial Reperfusion Improves the Functional Recovery of Hearts Donated After Circulatory Death

The resuscitation of hearts donated after circulatory death (DCD) is gaining widespread interest; however, the method of initial reperfusion (IR) that optimizes functional recovery has not been elucidated. We sought to determine the impact of IR temperature on the recovery of myocardial function during ex vivo heart perfusion (EVHP). Eighteen pigs were anesthetized, mechanical ventilation was discontinued, and cardiac arrest ensued. A 15‐min standoff period was observed and then hearts were reperfused for 3 min at three different temperatures (5°C; N = 6, 25°C; N = 5, and 35°C; N = 7) with a normokalemic adenosine–lidocaine crystalloid cardioplegia. Hearts then underwent normothermic EVHP for 6 h during which time myocardial function was assessed in a working mode. We found that IR coronary blood flow differed among treatment groups (5°C = 483 ± 53, 25°C = 722 ± 60, 35°C = 906 ± 36 mL/min, p < 0.01). During subsequent EVHP, less myocardial injury (troponin I: 5°C = 91 ± 6, 25°C = 64 ± 16, 35°C = 57 ± 7 pg/mL/g, p = 0.04) and greater preservation of endothelial cell integrity (electron microscopy injury score: 5°C = 3.2 ± 0.5, 25°C = 1.8 ± 0.2, 35°C = 1.7 ± 0.3, p = 0.01) were evident in hearts initially reperfused at warmer temperatures. IR under profoundly hypothermic conditions impaired the recovery of myocardial function (cardiac index: 5°C = 3.9 ± 0.8, 25°C = 6.2 ± 0.4, 35°C = 6.5 ± 0.6 mL/minute/g, p = 0.03) during EVHP. We conclude that the avoidance of profound hypothermia during IR minimizes injury and improves the functional recovery of DCD hearts.

Quantitative assessment of cardiac output and left ventricular function by noninvasive phase-contrast and cine MRI: Validation study with invasive pressure-volume loop analysis in a swine model

To validate noninvasive cardiac output measurements of phase‐contrast magnetic resonance imaging (PC‐MRI) and cine MRI using an invasive pressure‐volume (PV) loop technique on a swine model.

High Spinal Anesthesia Enhances Anti-Inflammatory Responses in Patients Undergoing Coronary Artery Bypass Graft Surgery and Aortic Valve Replacement: Randomized Pilot Study

Background Cardiac surgery induces many physiologic changes including major inflammatory and sympathetic nervous system responses. Here, we conducted a single-centre pilot study to generate hypotheses on the potential immune impact of adding high spinal anaesthesia to general anaesthesia during cardiac surgery in adults. We hypothesized that this strategy, previously shown to blunt the sympathetic response and improve pain management, could reduce the undesirable systemic inflammatory responses caused by cardiac surgery. Methods This prospective randomized unblinded pilot study was conducted on 14 patients undergoing cardiac surgery for coronary artery bypass grafting and/or aortic valve replacement secondary to severe aortic stenosis. The primary outcome measures examined longitudinally were serum pro-inflammatory (IL-6, IL-1b, CCL2), anti-inflammatory (IL-10, TNF-RII, IL-1Ra), acute phase protein (CRP, PTX3) and cardiovascular risk (sST2) biomarkers. Results The kinetics of pro- and anti-inflammatory biomarker was determined following surgery. All pro-inflammatory and acute phase reactant biomarker responses induced by surgical stress were indistinguishable in intensity and duration between control groups and those who also received high spinal anaesthesia. Conversely, IL-10 levels were markedly elevated in both intensity and duration in the group receiving high spinal anesthesia (p = 0.005). Conclusions This hypothesis generating pilot study suggests that high spinal anesthesia can alter the net inflammatory response that results from cardiac surgery. In appropriately selected populations, this may add incremental benefit by dampening the net systemic inflammatory response during the week following surgery. Larger population studies, powered to assess immune, physiologic and clinical outcomes in both acute and longer term settings, will be required to better assess potential benefits of incorporating high spinal anesthesia. Trial Registration ClinicalTrials.gov NCT00348920

Assessment of donor heart viability during ex vivo heart perfusion1

Ex vivo heart perfusion (EVHP) may facilitate resuscitation of discarded donor hearts and expand the donor pool; however, a reliable means of demonstrating organ viability prior to transplantation is required. Therefore, we sought to identify metabolic and functional parameters that predict myocardial performance during EVHP. To evaluate the parameters over a broad spectrum of organ function, we obtained hearts from 9 normal pigs and 37 donation after circulatory death pigs and perfused them ex vivo. Functional parameters obtained from a left ventricular conductance catheter, oxygen consumption, coronary vascular resistance, and lactate concentration were measured, and linear regression analyses were performed to identify which parameters best correlated with myocardial performance (cardiac index: mL·min(-1)·g(-1)). Functional parameters exhibited excellent correlation with myocardial performance and demonstrated high sensitivity and specificity for identifying hearts at risk of poor post-transplant function (ejection fraction: R(2) = 0.80, sensitivity = 1.00, specificity = 0.85; stroke work: R(2) = 0.76, sensitivity = 1.00, specificity = 0.77; minimum dP/dt: R(2) = 0.74, sensitivity = 1.00, specificity = 0.54; tau: R(2) = 0.51, sensitivity = 1.00, specificity = 0.92), whereas metabolic parameters were limited in their ability to predict myocardial performance (oxygen consumption: R(2) = 0.28; coronary vascular resistance: R(2) = 0.20; lactate concentration: R(2) = 0.02). We concluded that evaluation of functional parameters provides the best assessment of myocardial performance during EVHP, which highlights the need for an EVHP device capable of assessing the donor heart in a physiologic working mode.