A retrospective cohort study of a midodrine protocol for the prevention of post-operative hypotension for lower limb arthroplasty and emergency hip fracture surgery

Hypotension is a common post-operative complication that is associated with morbidity and mortality. There has been growing interest in the use of midodrine (oral alpha-1 adrenergic vasopressor agent) to increase systolic and mean arterial blood pressure in a variety of clinical applications. Our institution developed a 48-h midodrine protocol in 2020 for patients undergoing elective lower limb arthroplasty and emergency hip fracture fixation. The aim of this retrospective, single-centre metropolitan tertiary hospital cohort study was to evaluate the efficacy of the protocol in reducing the incidence and severity of perioperative hypotension (SBP <110 mmHg) within the first 24 h following surgery compared to the pre-protocol period (primary outcome). Secondary outcomes included frequency of hypotension 24–48 h post-operatively, bradycardia, incidence of MET calls and unplanned critical care admission. In total, 328 patients were identified for inclusion in the pre-protocol group and 298 in the protocol group. Introduction of the midodrine protocol was not associated with a significant difference in the incidence of the primary outcome. There was no statistically significant difference in the incidence of hypotension between groups post-operatively at 24 or 48 h. Of the secondary outcomes, patients receiving midodrine were more likely to be bradycardic in the post-anaesthesia care unit (43.8% vs 55.9%, p = 0.001) and at 24 h post-operatively (40.7% vs 53.8%, p = 0.003).