Monday, March 02, 2015

Systematic review on treatment of calcium blocker overdose

Free full text here.

Academic Life in Emergency Medicine summarizes the review:

A few findings from the systematic review:

The majority of literature on calcium channel blocker overdose management is heterogenous, biased, and low-quality evidence.

Interventions with the strongest evidence are high-dose insulin and extracorporeal life support.

Interventions with less evidence, but still possibly beneficial, include calcium, dopamine, norepinephrine, 4-aminopyridine (where available), and lipid emulsion therapy.

Stay tuned for the international guideline coming out soon. One treatment recommendation from the new guideline, reported at the 8th European Congress on Emergency Medicine September 2014, is not to use glucagon.

Sunday, March 01, 2015

Beta blockers in heart failure with preserved ejection fraction

From a recent paper in JAMA:

Objective To test the hypothesis that β-blockers are associated with reduced all-cause mortality in HFPEF.

Design Propensity score–matched cohort study using the Swedish Heart Failure Registry. Propensity scores for β-blocker use were derived from 52 baseline clinical and socioeconomic variables.

Setting Nationwide registry of 67 hospitals with inpatient and outpatient units and 95 outpatient primary care clinics in Sweden...

Participants From a consecutive sample of 41 976 patients, 19 083 patients with HFPEF (mean [SD] age, 76 [12] years; 46% women). Of these, 8244 were matched 2:1 based on age and propensity score for β-blocker use, yielding 5496 treated and 2748 untreated patients with HFPEF. Also we conducted a positive-control consistency analysis involving 22 893 patients with HFREF, of whom 6081 were matched yielding 4054 treated and 2027 untreated patients.

Exposures β-Blockers prescribed at discharge from the hospital or during an outpatient visit...

In the matched HFPEF cohort, 1-year survival was 80% vs 79% for treated vs untreated patients, and 5-year survival was 45% vs 42%, with 2279 (41%) vs 1244 (45%) total deaths and 177 vs 191 deaths per 1000 patient-years (hazard ratio [HR], 0.93; 95% CI, 0.86-0.996; P = .04). β-Blockers were not associated with reduced combined mortality or heart failure hospitalizations: 3368 (61%) vs 1753 (64%) total for first events, with 371 vs 378 first events per 1000 patient-years (HR, 0.98; 95% CI, 0.92-1.04; P = .46)...

Conclusions and Relevance In patients with HFPEF, use of β-blockers was associated with lower all-cause mortality but not with combined all-cause mortality or heart failure hospitalization. β-Blockers in HFPEF should be examined in a large randomized clinical trial.

Friday, February 27, 2015

Is “atypical coverage” really important in community acquired pneumonia?

In this study the inclusion of atypical coverage was not associated with reduced mortality but did result in shortened time to clinical stability.

Thursday, February 26, 2015

Occult bacteremia

These are the people who get sent home from the ER then have to be called back because their blood cultures turn positive. In this study from a single institution it appeared to be a benign entity:

This is a retrospective cohort study (September 2010 to September 2012), in adult patients discharged from the ED in whom blood cultures turned positive. Patients were evaluated according to a preestablished protocol.

We recorded 4025 cases of significant BSI in the ED and 113 patients with adult occult BSI. In other words, the incidence of occult BSI in the ED was 2.8 per 100 episodes. The predominant microorganisms were gram-negative bacteria (57%); Escherichia coli was the most common (41%), followed by gram-positive bacteria (29%), anaerobes (6.9%), polymicrobial (6.1%), and yeasts (0.8%). The most frequent suspected origin was urinary tract infection (53%), and most infections were community acquired (63.7%). Of the 105 patients that we were able to trace, 54 (42.5%) were asymptomatic and were receiving adequate antibiotic treatment at the time of the call, and 65 (51.2%) had persistent fever or were not receiving adequate antibiotic treatment.

Occult BSI is relatively common in patients in the adult ED. Despite the need for readmission of a fairly high proportion of patients, occult BSI behaves as a relatively benign entity.

Tuesday, February 24, 2015

When is permanent pacing indicated for AV block?

I'm working through MKSAP 16's section on cardiovascular disease. As much as I hate to be immodest, it's a content area I think I know just a little something about, particularly in the area of electrophysiology. I was drawn to their statement on permanent pacing after acute MI (AMI). Sprinkled throughout MKSAP are sets of high value care recommendations for various specialties, apparently their own version of Choosing Wisely.

The pacing recommendation, which is to wait several days after the occurrence of AV block (AVB) before inserting a permanent pacemaker (PPM) in order to see if the block persisted, struck me as awfully simplistic. Pacing recommendations for AVB have strong underpinnings in physiology which have withstood evidence based scrutiny. The relevant electrophysiology, far more often than not, can be assessed at the bedside via simple electrocardiography. Well, maybe I should qualify that by saying it's true provided adequate skill in interpretation of the ECG is brought to the bedside.

Things have changed through the years. Clinical skills in this area have deteriorated, in part because AVB complicating AMI is much less common in today's reperfusion era than it once was. The question of what to do with AVB after AMI seldom comes up anymore. Before the reperfusion era it was routine. The guiding principle back then was that, at least in acute anterior MI, when the block was subjunctional, that is true type II block, permanent pacing was indicated no matter how transient the block. (Caveat: the atypical situation of block arising in the common bundle of His is a nuanced topic, beyond the scope of this post).

So what about the current guidelines? The STEMI guidelines refer this topic to the device therapy guidelines which say in part:

1. Permanent ventricular pacing is indicated for persistent second-degree AV block in the His-Purkinje system with alternating bundle-branch block or third-degree AV block within or below the His Purkinje system after ST-segment elevation MI. (Level of Evidence: B) (79,126 –129,131)

2. Permanent ventricular pacing is indicated for transient advanced second- or third-degree infranodal AV block and associated bundle-branch block. If the site of block is uncertain, an electrophysiological study may be necessary. (Level of Evidence: B) (126,127) 

For patients in general with acquired AVB the guidelines include the following, listed under the class IIa category:

4. Permanent pacemaker implantation is reasonable for asymptomatic type II second-degree AV block with a narrow QRS.

When type II second-degree AV block occurs with a wide QRS, including isolated right bundle-branch block, pacing becomes a Class I recommendation. (See Section 2.1.3, “Chronic Bifascicular Block.”) (Level of Evidence: B) (70,76,80,85)

The recommendation summary is much more extensive but this small sample illustrates the complexity of decision making and the reliance on assessment of the anatomic site of block via electrocardiography (bedside electrophysiology). When it comes to pacing decisions post MI there's considerably more to it than the MKSAP recommendations would indicate.