A randomised trial to assess the impact of midodrine on early mobilisation after elective primary hip replacement surgery.

Early mobilisation following elective total hip arthroplasty (THA) facilitates quicker rehabilitation, and reduces complications and hospital length of stay. Reasons for delayed mobilisation are multifactorial, but the most common cause is orthostatic intolerance. Midodrine, an oral alpha-1 agonist, is used off-label for perioperative hypotension. However, there are few randomised trials assessing its use in the perioperative setting to improve patient outcomes. The aim of the study was to determine whether midodrine improves early mobilisation following primary THA, and whether this relates to reduced orthostatic intolerance. This prospective, triple-blinded, multicentre study involved 42 patients randomised to either placebo or 20 mg midodrine, 2 h before physiotherapy, on Day 1 postoperatively. The inclusion criteria were adults undergoing elective unilateral THA under spinal anaesthesia. The primary endpoint was the ability to walk 5 m with physiotherapists. Secondary endpoints included the incidence of orthostatic intolerance and hypotension. A preplanned interim analysis showed no statistical difference in ability to mobilise 5 m (78.26% vs 78.95%, P = 1.0). There was no statistically significant difference in the incidence of orthostatic intolerance between the groups 17.4% vs 31.6% (P = 0.45). Pre-emptive use of midodrine did not improve patient mobilisation the morning after elective primary THA and had no significant effect on the incidence of orthostatic hypotension.