Incidence of orthostatic intolerance and orthostatic hypotension after intravenous administration of morphine in patients prior to hip or knee arthroplasty.

Early postoperative mobilization is crucial for recovery of patients undergoing surgery in the multimodal fast-track approach to perioperative care, since physical immobilization is highly associated with increased risk of postoperative complications and prolonged hospital length of stay. Postoperative mobilization is often delayed due to patients experiencing orthostatic hypotension (OH), defined as a drop in systolic blood pressure > 20 mmHg or diastolic blood pressure > 10 mmHg, or orthostatic intolerance (OI), characterized by dizziness, blurred vision, nausea, vomiting, sensation of heat or syncope.

Previous studies have found a high incidence of postoperative OI (> 40 %) among patients undergoing total hip arthroplasty.

A possible causative factor to the high occurrence of OH and OI after surgery could be postoperative pain management by administration of morphine. Morphine is known to have many side-effects including nausea, vomiting, dizziness and orthostatic hypotension.

The object of this study is to isolate and estimate the effect of intravenous morphine on the incidence of OH and OI.

Inclusion Criteria:

• Patients undergoing primary unilateral total hip arthroplasty (THA), total knee arthroplasty (TKA) or unicompartmental knee arthroplasty (UKA)
• Patients > 18
• Patients that understand and speak Danish
• Patients that have provided written informed consent

Exclusion Criteria:

• Alcohol or substance abuse
• Habitual use of opioids
• Habitual use of anxiolytic, antidepressant and/or antipsychotic drugs
• History of previous orthostatic intolerance or hypotension
• Cognitive dysfunction
• Glomerular filtration rate (GFR) < 30 ml/min
• Cardiac arrhythmia

Patients undergoing primary unilateral total hip arthroplasty, total knee arthroplasty or unicompartmental knee arthroplasty