Weekly blog: The Harms of Oxygen Therapy

From my slides presented at this week's adverse events and deaths rounds:

* Too much oxygen can be dangerous
* This danger is preventable
* Shortness of breath DOES NOT equal need for oxygen

* Hypoxia (Sa02 below 90-92% in normal lungs and 88% in COPD/hypercapnic lungs) means that oxygen is likely required

Examples: Cornet et al, 2012 Jama Internal Medicine
http://archinte.jamanetwork.com/article.aspx?articleid=1108704

Acute MI (DOI: 10.1002/14651858.CD007160.pub3)
* RR mortality 2

CHF
* No RCT; increases afterload, increases LVEDP and decreases cardiac output

Post cardiac arrest
* OR 1.8 death

Ischemic stroke
* In RCT 40% death in O2 group vs 17% no O2 (p<0.01)

COPD* Mortality with TITRATED O2 (88-92) vs. usual care RR 0.2

What about in palliative care? (Campbell ML J symptom pain management 2013)

* The majority of patients who were receiving oxygen at baseline experienced no change in respiratory comfort when oxygen was withdrawn, 

* Oxygen provides little benefit in non-hypoxemic patients. 

* Oxygen may be an unnecessary intervention near death 

* Potential to add to discomfort through nasal dryness and decreased mobility

Other harms:

* Length of stay likely increased with failure to wean

* Decreased mobility as patient attached to tank

* Financial harm -- costs of oxygen (it isnt free!)

Weekly blog - Coumadin in Dialysis Patients with Atrial Fibrillation

Great discussion today -- very nuanced and the blog may not do it justice:

The CCS guidelines 2012 focused update:

We suggest that such patients not routinely receive either OAC (Conditional Recommendation, Low-Quality Evidence) or ASA for stroke prevention in AF (Conditional Recommendation, Low-Quality Evidence). Values and preferences. This recommendation places a relatively higher weight on observational data linking warfarin and ASA use with mortality in patients on dialysis, and relatively lower weight on the potential for these agents to prevent ischemic stroke. Therapy with OACs or antiplatelet drugs may be appropriate for some patients with eGFR < 15 mL per minute (on dialysis) in whom there is a stronger preference for avoiding ischemic stroke."

A recent observational study (well done, large study, and one of many to show this association) done here @ McGill shows that there is no decrease in the rate of stroke with a significant increase in bleeding in patients on dialysis with or without coumadin

The associated editorial (here) calls for a randomized controlled trial.  I like this quote from that editorial which is also worth reading:

"It is ironic that we are routinely treating many patients with renal disease and atrial fibrillation every day with great uncertainty as to benefit or harm without their consent, and at the same time, major regulatory and ethical barriers exist that prevent efficient enrollment of patients into clinical trials that are needed to answer this (and other) important questions."

I searched CLINICALTRIALS.GOV and as of now there are no studies looking at coumadin in the dialysis population.  So experimental evidence is long from publication.

Clearly we need to think before getting out the pen (or throwing away the prescription pad) and have discussions with our patients that are transparent and evidence based.

Weekly blog - Goal setting in hypertension

There was a fun argument about goal setting in hypertension targets:

I am a believer that you must always balance expected benefits (reductions in stroke, myocardial infarction, renal failure, CHF) against the potential harms (serious adverse drug effects).  Strict enforcement of arbitrary targets can lead to patient harm.  There is some evidence that the lower you treat the blood pressure, the lower certain events (i.e. stroke) with an increased risk of certain harms (i.e. renal failure, falls in the elderly).

Data on potential harm of over-treatment:

Hip fractures in the elderly:
http://www.ncbi.nlm.nih.gov/pubmed/23165923

"Hypertensive elderly persons who began receiving an antihypertensive drug had a 43% increased risk of having a hip fracture during the first 45 days following treatment initiation relative to the control periods (incidence rate ratio, 1.43; 95% CI, 1.19-1.72)."

Outcomes may be dependent on the diastolic blood pressure:
http://www.ncbi.nlm.nih.gov/pubmed/24026256

"The optimal BP in patients with CKD seems to be 130 to 159/70 to 89 mm Hg. It may not be advantageous to achieve ideal SBP at the expense of lower-than-ideal DBP in adults with CKD."

Why dual ACE/ARB combination really should not continue (there are several similar studies):
http://www.ncbi.nlm.nih.gov/pubmed/24206457

" There was no benefit with respect to mortality (hazard ratio for death, 1.04; 95% CI, 0.73 to 1.49; P=0.75) or cardiovascular events. Combination therapy increased the risk of hyperkalemia (6.3 events per 100 person-years, vs. 2.6 events per 100 person-years with monotherapy; P<0.001) and acute kidney injury (12.2 vs. 6.7 events per 100 person-years, P<0.001)."

Editorial here

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The JNC8 guidelines have abandoned the distinction between diabetics/renal failure patients and others with complicated hypertension:

"There is strong evidence to support treating hypertensive persons aged 60 years or older to a BP goal of less than 150/90 mm Hg and hypertensive persons 30 through 59 years of age to a diastolic goal of less than 90 mm Hg; however, there is insufficient evidence in hypertensive persons younger than 60 years for a systolic goal, or in those younger than 30 years for a diastolic goal, so the panel recommends a BP of less than 140/90 mm Hg for those groups based on expert opinion. The same thresholds and goals are recommended for hypertensive adults with diabetes or nondiabetic chronic kidney disease (CKD) as for the general hypertensive population younger than 60 years. "

The CHEP guidelines (2013) continue to make a distinction but use an even higher threshold for treatment in the general population.

1. Antihypertensive therapy should be prescribed for average diastolic blood pressures of 100 mmHg or higher (Grade A), or average systolic blood pressures of 160 mmHg or higher (Grade A) in patients without macrovascular target organ damage or other cardiovascular risk factors.
2. Antihypertensive therapy should be strongly considered if diastolic blood pressure readings average 90 mmHg or higher in the presence of macrovascular target organ damage or other independent cardiovascular risk factors (Grade A).
3. Antihypertensive therapy should be strongly considered if systolic blood pressure readings average 140 mmHg or higher in the presence of macrovascular target organ damage (Grade C for 140 mmHg to 160 mmHg; Grade A for higher than 160 mmHg).
4. Antihypertensive therapy should be considered in all patients meeting the above indications regardless of age (Grade B).  Caution should be exercised in elderly patients who are frail.

1. For patients with non-diabetic chronic kidney disease, target blood pressure is < 140/90 mmHg (Grade B).
2. Persons with diabetes mellitus should be treated to attain systolic blood pressures of less than 130 mmHg (Grade C) and diastolic blood pressures of less than 80 mmHg (Grade A). (These target blood pressure levels are the same as the blood pressure treatment thresholds.) 

Caution should be exercised in patients in whom a substantial fall in blood pressure is more likely or poorly tolerated (e.g. elderly patients and patients with autonomic neuropathy).