November 2020

Synopsis: Post-cardiotomy shock is a potentially fatal condition, affecting 0.5% to 1.5% of all adult patients undergoing cardiac surgery, and is characterized by failure to wean from cardiopulmonary bypass (CPB) or hemodynamic decompensation in the early post-operative period. Venoarterial (VA) ECMO has emerged as a rescue platform for patients with PCS, allowing time for myocardial recovery or serving as a bridge to more durable mechanical circulatory support platforms or transplant if needed. Two primary cannulation strategies exist for patients with PCS: “peripheral” VA ECMO with cannulation of the femoral artery and vein, and “central” VA ECMO with cannulation of the ascending aorta and right atrium. Each strategy has unique advantages and disadvantages, but both carry significant morbidity. As such, considerable debate exists about the “optimal” platform for PCS patients.

The Postcardiotomy Veno-arterial Extracorporeal Membrane Oxygenation study (PC-ECMO) is an observational, multicenter cohort study that enrolled patients undergoing VA-ECMO following adult cardiac surgery at 19 centers internationally from January 2010 to March 2018. Patients > 18 years who required VA-ECMO for PCS were included. Exclusion criteria included preoperative VA ECMO use, patients undergoing VAD implantation or heart transplant, and patients with open or hybrid repair of the descending thoracic aorta. The primary endpoint was in-hospital mortality. Secondary endpoints included death on VA-ECMO; reoperation for bleeding/tamponade; RBC transfusion; postoperative neurologic, renal, cardiac and gastrointestinal complications; vascular complications; sternal wound infection; and length of stay in the ICU. 

The PC-ECMO population consisted of 781 patients with a mean age of 63 years. Central and peripheral ECMO were performed in 31% and 69% of cases, respectively. In general, the central group was younger and had longer cardiopulmonary bypass times. Among this patient population, central VA ECMO was associated with significantly greater risk of in-hospital mortality (OR 1.54), reoperation for bleeding/tamponade (OR 1.96); and massive transfusion (OR 2.42). Peripheral ECMO was associated with longer length of stay (P=0.02), vascular access site infections (P=0.002), liver failure (P=0.02), and sepsis (P=0.05). No differences were observed with respect to peripheral vascular complications or other organ dysfunctions. There was no difference in outcomes when other important covariates, including patient demographics, were considered. The authors confirmed these findings with a subsequent meta analysis containing nearly 2500 patients. 

Key takeaways: In this cohort study, patients with PCS treated with peripheral ECMO had better in-hospital survival compared to those with central cannulation. Among those patients undergoing central cannulation, increased rates of major bleeding requiring reoperation and transfusion were important predictors of mortality. However, hemodynamic and physiologic benefits of central cannulation over peripheral cannulation remain. As such, further studies are needed to help define the optimal platform for PCS patients. 

Synopsis: The traditional standard of care for appendicitis is appendectomy. In recent years, there has been some investigation into the use of antibiotics alone for treatment, primarily in other countries, the largest of which (APPAC) used stringent inclusion criteria and specifically excluded those with an appendicolith. This group conducted the Comparison of Outcomes of Antibiotic Drugs and Appendectomy (CODA) trial, a randomized noninferiority trial over 25 US centers, to further investigate this question.

Exclusion criteria were fairly limited, including septic shock, peritonitis, and abscess. Those randomized to antibiotics received 24 hours of IV antibiotics followed by an oral regimen for a total of 10 days. Specific antibiotic choices were left to the discretion of the treating providers. The primary outcome was 30d health status, as measured by the European Quality of Life-5 Dimensions (EQ-5D) questionnaire; secondary outcomes included NSQIP-defined complications, antibiotic-related complications, and appendectomy in the antibiotics group. The primary analysis used linear regression to control for enrollment site and presence/absence of appendicolith, and rate of appendectomy in the antibiotics group (followed out to 90 days) was presented using a Kaplan-Meier curve. 

There was no difference in the primary outcome (EQ-5D) between groups, suggesting noninferiority of antibiotics. However, 29% of patients in the antibiotics groups underwent appendectomy by 90 days, the relative risk of an ED or urgent care visit within 90 days was 2.07 [95% CI 1.32, 3.25] in the antibiotics group, and the rate ratio for number of hospitalized days (over the same time period) following the initial treatment was 4.38 [2.49, 7.73] for the antibiotics group. Despite the fact that 47% of patients in the antibiotics group were discharged from the ED, while 95% of patients in the appendectomy group were admitted, the mean time from randomization to discharge from either the ED or hospital was the same in both groups (1.33 vs 1.30 days, rate ratio=1.00). Finally, the complication rate was higher in the antibiotics group (8.1 vs 3.5 per 100 patients, rate ratio 2.28 [1.30, 3.98]). The authors attribute this to the subgroup of patients with an appendicolith, as a stratified analysis revealed no difference in the no-appendicolith group.

While the authors found antibiotics alone to be noninferior on the basis of their primary outcome measure, the differences in secondary outcomes should give the reader some pause. This is far from definitive evidence that antibiotics alone are an acceptable treatment for acute appendicitis, at best suggesting that such a treatment might be acceptable in a well-informed patient without an appendicolith who adamantly wishes to avoid surgery. 

Synopsis:
BACKGROUND: The demand for heart transplantation has vastly outpaced the supply of hearts available from donation after brain death (DBD) donors. In the UK, less than half of waitlisted patients receive a heart transplant within 3 years. This is a study from the UK that examines the outcomes of transplanting hearts from after circulatory-determined death (DCD).

METHODS: This is single center’s experience with DCD hearts matched against DBD hearts. DCD hearts were procured with 2 protocols: 1) direct procurement and profusion (DPP) where a cannula is placed in the right atrium with cardioplegic solution after the 5 minutes of asystole time following withdrawal of life support, or 2) DCD heart retrieval using normothermic regional perfusion (NRP, a form of ECMO where there cerebral circulation was excluded). All hearts were maintained on machine perfusion during transportation. A retrospective cohort of DBD heart transplants, matched for donor and recipient characteristics, was used as a comparison group. The primary outcome measure of this study was 90-day survival.

RESULTS: There were 26 DCD heart transplants performed during the 25-month study period (12 NRP, 14 DPP). Survival at 90 days was not significantly different between DCD and matched DBD transplant recipients (DCD, 92%; DBD, 96%; p = 1.0). Hospital length of stay, treated rejection episodes, allograft function, and 1-year survival (DCD, 86%; DBD, 88%; p = 0.98) were comparable between groups. The method of retrieval (NRP or DPP) was not associated with a difference in outcome.

SUMMARY: This is a landmark proof of concept that we could consider transplanting DCD hearts in addition to DBD hearts. Some areas in the US have started to do this as well.