Hyperoxia post-cardiac arrest increases mortality.

Theheart.org . June 1, 2010 | Reed Miller

Camden, NJ – Hyperoxia in patients recovering in the intensive care unit (ICU) after cardiac arrest increases the risk of in-hospital death, a study from the Project IMPACT database shows.
Dr J Hope Kilgannon (Cooper University Hospital, Camden, NJ) and colleagues analyzed the outcomes of patients in ICUs following cardiopulmonary resuscitation after cardiac arrest at 120 centers.
Results of the study, supported by the National Institutes of Health and the Emergency Medicine Foundation, appear in the June 2, 2010 issue of the Journal of the American Medical Association. It is the first large multicenter study documenting the association between postresuscitation hyperoxia and poor clinical outcome, according to the authors.

Of the 6326 patients in the study, 1156 were hyperoxic—defined as arterial blood pressure (PaO2) >300 mm Hg within 24 hours after arriving in the ICU; 3999 were hypoxic (PaO2 <60 mm Hg); and 1171 were normoxic.

In-hospital mortality was 63% in the hyperoxic group, significantly higher than the 57% mortality in the hypoxic group and 45% mortality in the normoxic group (p<0.001). Hyperoxia was also associated with a lower likelihood of independent functional status at hospital discharge.

Kilgannon created a statistical model controlling for potential cofounders such as age, preadmission functional status, comorbid conditions, vital signs, and other factors and found that hyperoxia was associated with almost twice the risk of in-hospital mortality as normoxia (odds ratio 1.8; 95% CI 1.5-2.2).

“Reperfusion after an ischemic insult is associated with a surge of reactive oxygen species, which may overwhelm host natural antioxidant defenses,” the Kilgannon et al suggest. “The oxidative stress from the reactive oxygen species formed after reperfusion may lead to increased cellular death by diminishing mitochondrial oxidative metabolism, disrupting normal enzymatic activities, and damaging membrane lipids through peroxidation.”

In an accompanying editorial, Drs Patrick Kochanek and Hulya Bayir (University of Pittsburgh, PA) point out that the study also found a link between hypoxia and mortality after cardiopulmonary arrest. “This complicates the ability to make sweeping recommendations against the use of 100% oxygen early in resuscitation.” They suggest that measuring brain oxygen pressure may help optimize oxygen levels in postresuscitation patients but note that this approach is untested.

(Fuente: Theheart.org)

Tags: hiperoxigenación, parada cardiaca

Both CABG, CRT indicated? Same-session surgery, implantation best, study finds
The Heart.org  EuroHF 2010. | Steve Stiles

Berlin, Germany – If a patient with systolic heart failure and signs of ventricular dyssynchrony is undergoing CABG, that’s probably also the best time to implant a cardiac resynchronization therapy (CRT) pacemaker, a small randomized study confirmed.

That way, epicardial leads—which often get better results than transvenous leads—can be positioned during the open-chest procedure. But more important, there’s little to be gained and perhaps much to lose clinically by taking a “wait-and-see” approach to CRT after revascularization, according to investigators here at the Heart Failure Congress 2010 sessions of the Heart Failure Association of the European Society of Cardiology.

“In the majority of cases, CABG neither eliminates dyssynchrony nor improves left ventricular systolic function,” observed Dr Alexander Romanov (Novosibirsk State Research Institute of Circulation Pathology, Russia) when presenting the study, which randomized 178 patients with drug-refractory NYHA class 3-4 heart failure, an LVEF<35%, standard indications for CABG, and evidence of ventricular dyssynchrony by any of several methods to be given or not given a CRT device with epicardial lead placement at the time of surgical revascularization.

Those who got the devices with the CABG showed significant improvements in ventricular function, NYHA status and six-minute-walk distance, and quality of life over a mean follow-up of about 18 months, with gains in many cases becoming significant after the first three months, compared with the patients who received CABG only. And their mortality, the study’s primary end point, was significantly reduced (p=0.006), Romanov reported.

Prof John GF Cleland (University of Hull, Kingston-upon-Hull, UK), who wasn’t involved in the study, went to Romanov right after his presentation and said, “Nice. We’re going to be telling our surgeons straightaway.”

Prof John GF Cleland observed that some of the earliest clinical studies of ventricular dyssynchrony were conducted by surgeons who performed CABG with the goal of correcting or improving it, “so many surgeons believe that the dyssynchrony will be fixed by revascularization, and you won’t need to pace.” Even many cardiologists, he added, would tend to favor revascularization first, to see if it improves heart function, before considering CRT. The current study suggests that CRT shouldn’t wait.

The 91 patients who underwent CABG with pacing-only CRT (CRT-P) implantation and the 87 who received CABG alone were similar at baseline with respect to QRS duration, echocardiographic features—including severity of dyssynchrony—and NYHA class, functional capacity, and quality of life. Ventricular dyssynchrony was defined according to QRS duration >120 ms, per guidelines, or by any of several echocardiographic or tissue-Doppler-imaging methods.

The CABG-only patients didn’t show much change in functional or quality-of-life measures throughout the follow-up, whereas the CABG+CRT group showed marked improvement within three months and then continued improvement (compared with CABG-only patients) in NYHA class (p=0.026), six-minute-walk distance (p=0.001), LVEF (p=0.001), and scores on the Minnesota Living with Heart Failure Questionnaire (p=0.001) throughout the rest of the follow-up.
Changes in dyssynchrony, as measured by tissue-tracking imaging and by tissue-resynchronization imaging, followed a similar pattern: little change in the CABG-only group but pronounced and significant improvement in the CABG+CRT group at the three-month follow-up (p=0.0001 for both imaging methods), which continued for the rest of the trial.

Mortality reached 26.4% in the CABG-only group and only 9.9% in CABG+CRT group (p=0.006). In multivariate analysis, significant mortality predictors did not include age, sex, diabetic status, NYHA functional class, baseline LVEF or QRS duration, or baseline end-diastolic or end-systolic volumes. However, LV dyssynchrony persisting after CABG showed a mortality hazard ratio of 2.634 (95% CI 1.20-5.75; p=0.015).

Cleland noted that epicardial lead placement could well be another advantage to CRT implantation at the time of CABG. There are limited options for positioning transvenous leads, and “the cardiologist very often has a problem finding the best spot for resynchronizing the ventricle. Surgeons can choose any spot they want,” he said. “I think there’s still a role for epicardial-lead pacemakers—if I needed resynchronization [therapy] and a bypass, then I’d want the surgeon to do that.”

(Fuente: The Heart.org)

Tags: resincronización, revascularización