Conditions: Orthostatic Hypotension
Allocation: NON_RANDOMIZED | Intervention model: PARALLEL
Enrollment: 13
Healthy volunteers: no

Brief summary:
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).

Detailed description:

Arms:
arm 1: Patients who are diagnosed with orthostatic hypotension at their first physical therapy session and have an SVV\<15 will be given oral midodrine, 10 mg, once. arm 2: Patients who are diagnosed with orthostatic hypotension at their first physical therapy session and have an SVV\>=15 will be given intravenous fluid bolus, 15 cc/kg, once. arm 3: Patients who are NOT diagnosed with orthostatic hypotension at their first physical therapy session will be given the interventions.

Interventions: intervention 1: Midodrine intervention 2: Intravenous fluid bolus
Intervention descriptions: intervention 1: 10 mg, p.o., once, on day of surgery after first physical therapy session intervention 2: 15 cc/kg, once, on day of surgery after first physical therapy session

Protocol document: