Although the exact pathophysiology of hepatic encephalopathy (HE) is not fully understood, for more than a century ammonia has been thought to play a critical role. However, the interpretation and utility of ammonia levels in patients with chronic liver disease (CLD) presenting with HE has been a long-standing source of confusion. It is a common belief in the emergency department and on the wards that a single elevated ammonia level in a patient with CLD can confirm the diagnosis of HE, and a normal level essentially rules it out. This confusion stems from the fact that early studies showed a correlation between degree of encephalopathy and the ammonia level, but numerous subsequent studies have shown that severely encephalopathic patients often have normal ammonia levels. This paper reviews the published literature on ammonia levels in patients with CLD in an attempt to clarify its value as a clinical decision-making tool in patients with suspected HE.

Wolff–Parkinson–White (WPW) syndrome with atrial fibrillation (AF) is a potentially life-threatening problem requiring rapid conversion to sinus rhythm. The most recent American Heart Association guidelines for the treatment of patients with WPW, published in conjunction with the 2000 Advanced Cardiac Life Support (ACLS) guidelines, suggests that intravenous amiodarone is a first-line therapy for AF–WPW; however the evidence suggests this is a potentially dangerous myth.

There has been much debate as to whether magnesium, a well-tolerated, readily available and cheap therapy, should be used to treat patients with suspected myocardial infarction. Despite promising results from animal studies and small clinical trials conducted in the 1980s, two large recent trials have concluded that the once phenomenal treatment is ineffective. The story of magnesium for acute myocardial infarction is a lesson in medical humility.

Reliance on the accuracy of the pelvic examination is upheld in many medical textbooks, but review of the literature does not support the accuracy or reproducibility of this examination. That this “test” is useful for ruling out serious disease will be exposed for the myth that it is.