Orthostatic Hypotension (OH)

Confirm it at the bedside, don't take it from the chart - Blood pressure and heart rate supine after 5 minutes, then repeated at 1 and 3 minutes standing. A 20 mmHg systolic or 10 mmHg diastolic fall makes the diagnosis; in a patient with baseline hypertension use a 30 mmHg systolic drop instead. Repeating the measurement later in the day raises detection.

The heart rate response tells you the mechanism - A rise under 15 bpm alongside the drop points to a neurogenic cause; over 20 bpm points to volume depletion; over 30 bpm within 10 minutes with little or no pressure fall is POTS. Beta blockade makes this reading uninterpretable.

Neurogenic patients have no catch - There is no baroreflex vasoconstriction or tachycardia waiting to rescue them from induction, neuraxial sympathectomy, head-up positioning, or a sudden change in preload. Plan the pressure support before you need it rather than chasing it.

Reconcile the medication list first - Antihypertensives, diuretics, vasodilators, antidepressants, antipsychotics, dopaminergic drugs, opioids, and alcohol all precipitate it, and in the elderly the number of antihypertensives is a better predictor than any single class. Removing or dose-adjusting the offending agent is the highest-yield preoperative intervention.

Supine hypertension coexists - About half of patients with neurogenic orthostatic hypotension are also hypertensive supine. A normal or high pressure on the OR table does not mean they are volume replete, and it complicates how hard you can treat either problem.

Know the drugs they arrive on - Fludrocortisone (mineralocorticoid, expands intravascular volume), midodrine (alpha-1 agonist), droxidopa, and pyridostigmine (acetylcholinesterase inhibitor) all work by raising vascular tone or volume. Note them so you can interpret the baseline pressure and the response to your own vasopressors.

Diabetic autonomic neuropathy travels with gastroparesis - The same visceral autonomic fibers that fail to regulate blood pressure also produce gastroparesis. Treat these patients as a full stomach and plan the airway accordingly.

Come to the room volume replete - Dehydration, bowel prep losses, a hot environment, large meals, and alcohol all worsen it. Correct the deficit preoperatively rather than covering it with vasopressor after induction.

Positioning and emergence reproduce the drop - Sitting them up on the table, standing them for a block, and first ambulation in PACU are the same orthostatic stress that caused the diagnosis. Move in stages and check the pressure before they stand.

Postprandial hypotension is the same problem after a meal - A systolic fall of at least 20 mmHg within 75 minutes of eating, common in the elderly and in autonomic failure. It matters for when they eat postoperatively and when they first get up afterward.

The morbidity is falls and vascular events - Orthostatic hypotension is associated with increased mortality and with myocardial infarction, heart failure, stroke, and atrial fibrillation. Assisted first ambulation and fall precautions are part of the anesthetic plan, not just nursing's problem.

Standing shifts 300 to 800 mL of blood into the legs and splanchnic veins. Venous return, right atrial pressure, and stroke volume all fall, and arterial pressure follows. Normally the carotid sinus and aortic arch baroreceptors correct it within a beat — vagal tone drops, sympathetic outflow rises, and vasoconstriction plus a 10 to 15 bpm rise in heart rate hold the pressure up while renin-angiotensin-aldosterone and vasopressin defend volume.

Orthostatic hypotension is the failure of that reflex: a sustained fall of at least 20 mmHg systolic or 10 mmHg diastolic within three minutes of standing or 60-degree head-up tilt. The cause is volume depletion, medication, or autonomic failure from diabetic neuropathy, Parkinson disease, multiple system atrophy, or pure autonomic failure. Prevalence climbs with age — under 5% at 45 to 49 years, over 25% past 85. It flags a patient with no reserve against anything that drops preload or sympathetic tone.