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Rationale

Introduction Advances in perioperative care, especially in analgesia and postoperative care has led to a push towards outpatient surgery, where the patients are discharged on the same day of surgery. The implementation of fast-track setting in total hip arthroplasty (THA) has made this a reality for a subset of patients (1,2). Outpatient surgery has been shown to be safe with proper discharge criteria and significantly reduces the cost of the procedure (1).

Early postoperative mobilization is essential for rapid functional recovery after surgery and subsequent discharge on the same day of surgery. However, transient inability to ambulate is highly prevalent after orthopedic surgery and remains a cause of prolonged postoperative hospital stay due to orthostatic hypotension (2) causing orthostatic intolerance (OI) (3). Patients undergoing fast-track total hip or knee arthroplasty are routinely planned to be mobilized on the day of surgery and are required to participate in physiotherapy sessions in the early postoperative period. However, OI may delay recovery and length of stay and could lead to potential serious complications such as falls with a risk of prosthesis dislocation or fracture (4). OI is the inability to maintain blood pressure in the upright position. This may be due to inability in increasing heart rate, cardiac contractility and - most importantly - systemic vascular resistance. It has been shown that daily repeated tilts restore orthostatic tolerance (OT) in syncope patients by increasing the degree of vasomotor reserve available for vasoconstriction (5). However, repeated mobilization aimed at counteracting postoperative OI has not been studied in fast-track orthopedic or other types of surgery but may have a positive clinical impact. In previous studies, we found OI to be present in more than 40% six hours after THA and still present in half of these at 24 hours. The OI was related to an attenuated cardiac output and vascular resistance response to standing and consequently to cerebral hypoperfusion. However, OI could not be explained by the degree of postoperative anemia or fluid administration in the early postoperative period (3,4).

We hypothesize that an enhanced mobilization protocol (postural training) might alleviate or shorten the duration of postoperative OI. The planned study's primary objective is to assess if repeated mobilization starting 4 hours after surgery can reduce symptoms or duration of OI. Secondary objectives are: 1) To describe blood pressure response to an enhanced mobilization protocol in a group of patients with OI and 2) to evaluate whether the enhanced mobilization procedure (outlined below) is feasible in normal clinical practice following elective THA.

Description of the cohort

This study is a multi-center single-arm exploratory and hypothesis generating study. Eligibility criteria:

Inclusion: • Age ≥ 18 • Scheduled to undergo elective THA at OUH Svendborg Sygehus or Lillebaelt Hospital - Vejle with either neuraxial or general anesthesia. • Sinus rhythm

Exclusion: • Diabetes Mellitus • Parkinson's disease • Known autonomic dysfunction o Postural hypotension o Postprandial hypotension o Movement disorders o Multiple system atrophy • Preoperative cardiac arrhythmias • Known atrial fibrillation • Pacemaker treatment • Malignancy

Data and biological material

Data gathered Data will only be gathered for the included patients, and will consist of the following:

• Demographics o Age o Sex o Height o Weight o ASA score

• Surgical o Duration of surgery o Blood loss during surgery o Mode of anesthesia o Intraoperative fluids o Intraoperative opioid use

• Postoperative o Continuous blood pressure

▪ Resting

▪ During mobilization procedure o Signs of OI during mobilization procedures

▪ OHSA questionnaire o Use of analgesics after surgery during study o Pain

▪ Immediately before mobilization

Collaborating researchers and departments

Department of Orthopedic Surgery, Vejle and Svnedborg

• Claus Varnum
• Martin Lindberg-Larsen