An Open Label Trial to Decrease Signs and Symptoms of Orthostatic Hypotension Using Midodrine or Intravenous Fluid Bolus in Patients Following Total Hip Arthroplasty

Orthostatic hypotension following total hip arthroplasty is known to limit the ability of
patients to perform physical therapy (PT) and increase the length of hospital stay and
costs. Our goal is to prospectively study the effects of oral midodrine on the signs and
symptoms of orthostatic hypotension in 20 patients and the effects of intravenous fluid on
the signs of symptoms of orthostatic hypotension in 10 patients. Midodrine will be
administered to patients with suspected low SVV, and an intravenous fluid bolus will be
administered to patients with low CO. 120 patients will be consented with a view to studying
30 patients who meet the inclusion criteria for orthostatic hypotension. Patients who
receive midodrine or the fluid bolus will undergo hemodynamic measurements at 30 min, 1 hr,
2 hrs, 3 hrs, and 4 hrs post-intervention. All patients will undergo measurements for blood
pressure, arterial augmentation index, and heart rate at baseline (pre-op; holding area) and
the time of first PT attempt. Patients will be monitored up to post-operative day 3. The
working hypothesis is that midodrine or fluid therapy will significantly raise the mean
arterial blood pressure (MAP) by 5 mmHg+ and/or cause a significant change in the
Orthostatic Hypotension Questionnaire (characterized by a two-point improvement in symptom
score).