Orthostatic Hypotension Syndromes

A patient with Parkinson disease may become light-headed on standing while the pulse rises only a few beats per minute. A patient with diarrhoea may report the same symptom but develop marked tachycardia. Both may meet the blood-pressure definition of orthostatic hypotension, yet the heart-rate response points toward different mechanisms and different treatment priorities. Orthostatic hypotension is therefore more than a low reading. It is inadequate circulatory compensation when upright posture reduces venous return and cerebral perfusion. The clinical task is to confirm the timing and magnitude of the pressure fall, identify whether autonomic failure, volume loss, medication, cardiac disease, or another illness is responsible, and reduce symptoms without creating dangerous supine hypertension. The terminology matters. Classic, initial, and delayed orthostatic hypotension are defined by when the fall occurs. Postural orthostatic tachycardia syndrome produces orthostatic symptoms and tachycardia without orthostatic hypotension, so it is not interchangeable with OH. In Canadian NP practice, medication decisions must also respect provincial prescribing authority, local formulary requirements, and the fact that droxidopa is not authorised for routine sale in Canada.