Alexander Wahba

Position article for the use of extracorporeal life support in adult patients

Extracorporeal life support (ECLS) is one of the recent fields in cardiac surgery which has improved significantly the quality of patient care in acute or chronic end-stage heart disease. The safe use of this new technology requires many different prerequisites which are summarized in this position article. It includes the necessary personnel and their qualifications, the structural assumptions, the required equipment, and the parameters which have to be monitored for the safe usage of these devices. In addition, indications and contraindications for ECLS, the management and control of a wide range of parameters related to the extracorporeal circulation, as well as the necessary equipment are described. Quality assurance and education are also described in this position article.

Prediction of mortality in adult patients with severe acute lung failure receiving veno-venous extracorporeal membrane oxygenation: a prospective observational study

IntroductionVeno-venous extracorporeal membrane oxygenation (vvECMO) can be a life-saving therapy in patients with severe acute lung failure refractory to conventional therapy. Nevertheless, vvECMO is a procedure associated with high costs and resource utilization. The aim of this study was to assess published models for prediction of mortality following vvECMO and optimize an alternative model.MethodsEstablished mortality risk scores were validated to assess their usefulness in 304 adult patients undergoing vvECMO for refractory lung failure at the University Medical Center Regensburg from 2008 to 2013. A parsimonious prediction model was developed based on variables available before ECMO initiation using logistic regression modelling. We then assessed whether addition of variables available one day after ECMO implementation enhanced mortality prediction. Models were internally validated and calibrated by bootstrapping (400 runs). Predictive ability, goodness-of-fit and model discrimination were compared across the different models.ResultsIn the present study population, existing mortality prediction tools for vvECMO patients showed suboptimal performance. Evaluated before vvECMO initiation, a logistic prediction model comprising age, immunocompromised state, artificial minute ventilation, pre-ECMO serum lactate and hemoglobin concentrations showed best mortality prediction in our patients (area under curve, AUC: 0.75). Additional information about norepinephrine dosage, fraction of inspired oxygen, C-reactive protein and fibrinogen concentrations the first day following ECMO initiation further improved discrimination (AUC: 0.79, P = 0.03) and predictive ability (likelihood ratio test, P < 0.001). When classifying patients as lower (<40%) or higher (>80%) risk based on their predicted mortality, the pre-ECMO and day1-on-ECMO models had negative/positive predictive values of 76%/82% and 82%/81%, respectively.ConclusionsWhile pre-ECMO mortality prediction remains a challenge due to large patient heterogeneity, evaluation one day after ECMO initiation may improve the ability to separate lower- and higher-risk patients. Our findings support the clinical perception that chronic health condition, high comorbidity and reduced functional reserves are strongly related to survival during and following ECMO support. Renewed evaluation the first day after ECMO initiation may provide enhanced guidance for further handling of ECMO patients. Despite the usefulness of prediction models, thorough clinical evaluation should always represent the cornerstone in decision for ECMO.

Remote Ischemic Preconditioning Preserves Mitochondrial Function and Influences Myocardial MicroRNA Expression in Atrial Myocardium During Coronary Bypass Surgery

Rationale: Remote ischemic preconditioning (RIPC) has been suggested to induce cardioprotection during cardiac surgery. Maintaining proper atrial function is imperative in preventing arrhythmia and thrombus formation. Mitochondria have been proposed as key targets in conveying RIPC mechanisms and effects. MicroRNA (miR) is emerging as an important regulator of mitochondrial function, arrhythmia, and protection from ischemia and reperfusion. Objective: This study aimed to evaluate the effect of RIPC on mitochondrial respiration and miR expression in human atrial tissue. Methods and Results: Sixty patients undergoing coronary artery bypass graft surgery were randomized to RIPC (n=30) or control (n=30). RIPC was performed preoperatively by inflating a blood pressure cuff on the upper arm to 200 mm Hg for 3×5 minutes, with 5 minutes reperfusion intervals. Biopsies were obtained from the right atrial appendage before and after aortic cross-clamping. Mitochondrial respiration was measured in situ and miR assessed by commercial miR array and quantitative reverse transcription polymerase chain reaction. Postoperative atrial fibrillation occurrence was monitored by biotelemetry. Maximal mitochondrial respiration was preserved throughout surgery after RIPC but significantly reduced (−28%; P<0.05) after aortic cross-clamping in control. Incidence of postoperative atrial fibrillation was lower after RIPC versus control (14% versus 50%; P<0.01). Myocardial expression of miR-133a and miR-133b increased after aortic cross-clamping in both RIPC and control, whereas miR-1 was upregulated in control only. MiR-338-3p expression was higher in RIPC versus control after aortic cross-clamping. Conclusions: RIPC preserves mitochondrial respiration and prevents upregulation of miR-1 in the right atrium during coronary artery bypass graft. Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01308138

Chronic pain after cardiac surgery: a prospective study

Background: Chronic pain is a complication of several surgical procedures. The prevalence of chronic pain reported after cardiac surgery varies from 18% to 61%. However, most studies are retrospective, do not use validated instruments for pain measurement or include only pain at the sternum site. The aim of the present study was to assess chronic pain and health‐related quality of life (HRQOL) after cardiac surgery.

Prophylactic treatment with desmopressin does not reduce postoperative bleeding after coronary surgery in patients treated with aspirin before surgery

The synthetic vasopressin analog desmopressin has hemostatic properties and may reduce postoperative bleeding after coronary artery bypass grafting (CABG). A study on the effects of recent aspirin ingestion on platelet function in cardiac surgery showed a greater impairment of platelet function in patients treated with aspirin <2 days before the operation. We evaluated the effects of desmopressin on postoperative bleeding in CABG patients who were treated with aspirin 75 or 160 mg until the day before surgery. The study was a prospective, randomized, double-blinded, placebo-controlled, parallel group trial. One-hundred patients were included and divided into two groups. One group received desmopressin 0.3 &mgr;g/kg and the other received placebo (0.9% NaCl) after the neutralization of heparin with protamine sulfate. Postoperative blood loss was recorded for 16 h. The mean (sd) bleeding was 606 (237) mL in the desmopressin group and 601 (301) mL in the placebo group (P = 0.93), representing no significant difference (95% confidence interval, −107 to 117 mL). We conclude that desmopressin does not reduce postoperative bleeding in CABG patients treated with aspirin until the day before surgery.

Cardiopulmonary bypass leads to a preferential loss of activated platelets. A flow cytometric assay of platelet surface antigens.

OBJECTIVE In a prospective study surface antigens associated with platelet activation, aggregation, and adhesion and the platelet volume were measured to investigate the mechanism of the platelet function defect of cardiopulmonary bypass (CPB). METHODS Blood samples were obtained during cardiac surgery before and after heparinization, as well as during and following extracorporeal circulation. The expression of the platelet surface glycoproteins (GP) IIb-IIIa, Ib, 53, and the granule membrane protein (GMP) 140 were measured using flow cytometry in platelet-rich plasma (PRP) before and after in vitro stimulation with adenosine diphosphate. A full blood count including mean platelet volume (MPV) was taken. RESULTS Heparinization resulted in a significant increase of GP 53 and GMP 140 and a significant decrease of GP Ib expression. During and following CPB, GP IIb-IIIa and Ib were significantly decreased. Similarly, the expression of the activation markers was reduced significantly. The mean platelet volume decreased significantly from 8.6 +/- 0.7 fl at baseline to 7.9 +/- 0.8 fl at the end of the study period. CONCLUSION Our data suggest that heparinization induces platelet activation. We assume that a loss of larger and more activated platelets from the circulation contributes substantially to the platelet function defect of CPB.

Guiding Surgical Cannulation of the Inferior Vena Cava with Transesophageal Echocardiography

We studied 150 adult cardiac surgery patients to assess visualization of the venous cannula and the venous system by intraoperative transesophageal echocardiography and to register the incidence of cannulation of hepatic veins. The quality of images, the dimensions of the venous system, the position of the venous cannula, and the adequacy of venous return were registered. Acceptable image quality of the inferior vena cava and the right hepatic vein (RHV) was obtained in 95% and 87% of cases, respectively. Considerable individual variations were found in the dimensions of the venous system. The cannula position could be determined in 99% of the cases. Ten percent of venous cannulae were primarily placed in the RHV. A short distance between the eustachian valve and the RHV possibly predisposes to cannulation of the RHV. No other patient-related factors were associated with cannula position. Placement of the cannula deep in the inferior vena cava was associated with reduced venous return and may be a more important cause of reduced return than a cannula positioned in a hepatic vein.

Effect of clopidogrel on midterm graft patency following off-pump coronary revascularization surgery.

OBJECTIVE The aim of the study was to evaluate the effect of clopidogrel on midterm graft patency following off-pump coronary revascularization surgery. DESIGN Ninety-four consecutive patients who underwent off-pump coronary artery bypass grafting between 1997 and 2002 were studied (58 men, 36 women; 61.7 +/- 9.8 years). The initial 36 patients (control group) received 75 to 160 mg acetyl salicylic acid (ASA) as an antiplatelet agent, whereas the consecutive 58 patients (clopidogrel group) received 75 mg clopidogrel postoperatively in addition to ASA. Intraoperatively, graft flow was assessed with transit-time flowmetry in all patients and the peripheral anastomoses were assessed with epicardial ultrasound in 28 patients. Sixty-two patients underwent angiography after a mean of 185 +/- 92 days. A total of 82 grafts were evaluated angiographically. Grafts with TIMI flow 2 and 3 were assessed as patent. RESULTS At angiographic follow-up, the overall graft patency rate was 84% (31/37) in the control group and 93% (42/45) in the clopidogrel group (P value was not significant [ns]). Graft patency rates for left internal mammary artery (LIMA) grafts were 92% (23/25) versus 96% (28/29) (ns), and for saphenous vein grafts were 66% (7/11) versus 87% (14/16) (ns), respectively. CONCLUSION The observed trend toward higher patency rates in patients treated with clopidogrel did not reach statistical significance. Further larger studies are necessary to confirm these preliminary results.

Rectal lactate levels in endoluminal microdialysate during routine coronary surgery

The aim of this prospective study was to determine the feasibility of intestinal endoluminal microdialysis as a new method for clinical monitoring of the adequacy of splanchnic perfusion in the large bowel. A microdialysis catheter for continuous lactate, glycerol, glucose and pyruvate measurements attached to a tonometric catheter was placed into the lumen of the recto‐sigmoid junction prior to surgery in 13 patients undergoing elective cardiac surgery with cardiopulmonary bypass (CPB). Lactate was also measured in blood and muscle. CPB was associated with a 10‐fold increase in luminal lactate from 0.16 (0.01) to 1.67 (0.38) mmol.l−1 (p < 0.001). Muscular lactate increased from baseline levels 1.20 (0.21) to 1.77 (0.36) mmol.l−1 during CPB (p = 0.01), but the muscular lactate–pyruvate ratio remained unchanged. Arterial lactate increased only slightly from 0.9 (0.05) to 1.1 (0.06) mmol.l−1 (p = 0.027) during CPB. Increased lactate concentrations in the large bowel during CPB are suggestive of local lactate production consistent with impaired oxygen delivery. Intestinal endoluminal microdialysis is a potential clinically applicable method for monitoring intestinal metabolism. Combined with tonometry, microdialysis provides the opportunity to monitor both circulation and metabolism in the rectal mucosa.

Health-related quality of life three years after coronary surgery: A comparison with the general population

Objectives. To assess health-related quality of life (HRQOL) in patients three years after coronary artery bypass grafting (CABG) compared to the general Norwegian population, with emphasis on age and gender-differences. Design. A cross-sectional postal survey of patients who underwent CABG in 2000. HRQOL was assessed using the Short Form 36 (SF-36). Subgroup analyses were performed according to age (<70 versus ≥70 years) and gender. Results. Of 233 eligible patients 203 responded (mean age 67.6 years, 17% females). Patients reported better scores on bodily pain than the general population (p = 0.008), but did not differ on other subscales of SF-36. Younger patients tended to score lower, older patients higher than the general population on HRQOL. Female patients reported lower HRQOL than the general female population and reported significantly lower scores than male patients on 3 of 8 subscales. Conclusions. Three years after CABG the HRQOL is comparable to the general Norwegian population even in older patients. The older patients reported less pain than the general population.