Carbon Monoxide Toxicity in the Elderly

SOURCE: Muo IM, et al. Carbon monoxide poisoning: Safety tips for practitioners in the long-term care setting. Ann Long-Term Care 2015;23:35-38.

The signs of carbon monoxide toxicity (CMT) may be subtle and easily mistaken for other disorders, simply because clinicians may not think of it. Symptoms such as change in mental status, chest pain, dizziness, headache, nausea, seizure, and syncope do not necessarily bring CMT to front-of-mind status. Most episodes of CMT occur in colder climates during winter, but CMT can occur in any environment, at any time of year.

Typical presentations of CMT include sinus tachycardia, tachypnea, and focal neurologic deficits. Because pulse oximeters do not detect carboxyhemoglobin levels, pulse oximetry is usually normal. Because the affinity of carbon monoxide for hemoglobin is several hundred-fold greater than oxygen, once carbon monoxide has bound to hemoglobin, oxygen binding is markedly reduced and tissue hypoxia ensues. Acute MI, angina, and heart failure may all represent CMT. Chronic CMT can lead to neurologic damage, including Parkinsonism and frontal lobe dysfunction, sometimes presaged by admission for altered mental status.

Hyperbaric oxygen treatment is generally considered the optimum treatment resource for CMT, although a Cochrane review did not confirm the superiority of hyperbaric oxygen over treatment with normobaric oxygen. When clinicians encounter syndromes reflecting potential tissue ischemia, CMT should sometimes be among the differential diagnoses. Prompt intervention may prevent important neurologic sequelae.

Does Hypovitaminosis D Increase Risk of Atrial Fibrillation in Hypertensive Patients?

SOURCE: Ozcan OU, et al. Relation of vitamin D deficiency and new-onset atrial fibrillation among hypertensive patients. J Am Soc Hypertens 2015;9:307-312.

If you have been practicing medicine for 5 years or longer, you probably have already been assailed by literature from all compartments of medicine claiming that low levels of vitamin D are associated with almost anything bad that can happen to almost anyone. Just in case your dossier of hypovitaminosis D crimes is insufficiently full, you might consider adding “New Onset Atrial Fibrillation” to the rap sheet.

Ozcan et al evaluated 227 hypertensive patients, among whom 137 had new onset atrial fibrillation (AFIB). When they compared the levels of vitamin D in persons with new onset AFIB to controls (the hypertensive patients who didn’t have AFIB), they found that low vitamin D levels (< 20 ng/mL) were essentially twice as common in the AFIB group (67% vs 33%). The odds ratio for incurring AFIB was almost 70% greater for patients with low vitamin D levels than vitamin D-replete individuals.

Explanations for how vitamin D might be related to AFIB include the observation that activation of the renin-angiotensin-aldosterone system is heightened in vitamin D deficiency states. Whether vitamin D supplementation would result in reduced incidence of AFIB has not yet been determined.

Reflections on the Consequences of Morning BP Surge

SOURCE: McMullan CJ, et al. Racial impact of diurnal variations in blood pressure on cardiovascular events in chronic kidney disease. J Am Soc Hypertens 2015;9:299-306.

The circadian rhythm of blood pressure (BP) in healthy individuals, as well as most persons with hypertension, is characterized by a 10-20% decline in BP overnight, followed by an early (pre-awakening) rise maintained through much of the day. The change from lowest overnight BP to sustained morning BP is called the morning “surge,” remembering that timing of BP changes is actually relative to sleep cycle rather than time of day.

It has been noted that deviations from the “typical” circadian BP pattern of healthy individuals — for instance, failure to experience a dip in overnight BP (non-dipping) — is associated with increased risk of cardiovascular (CV) endpoints. Additionally, CV events tend to cluster with the morning surge in BP in the population at large, including those with hypertension.

McMullan examined diurnal variations in BP among patients with CKD to see whether ethnicity factors into outcomes. Their study population included Japanese (n = 197) and African-American (n = 197) men.

McMullan determined that the morning BP surge was associated with increase CV risk in Japanese, but not African-American, men. Whether BP treatment that specifically affects morning BP surge might provide specific risk reduction independent of overall BP control remains to be determined.