Adverse Effects of Subcutaneous vs Intravenous Hydration on Older Acutely Admitted Patients: An Assessor-blinded, Non-inferiority RCT

Adequate hydration is essential to humans, and is tightly regulated in the healthy adult by in- and output (i.e. thirst and urine production). This regulation is often hampered in the geriatric patient due to a decreased sensation of thirst and impaired kidney function. The risk of dehydration increases rapidly in the acutely ill geriatric patient with the growing fluid demand of fever and reduced ability to self-hydrate due to fatigue. Dehydration will often aggravate an acute illness creating a vicious circle. External rehydration is essential to stop or even prevent this downward spiral. Adequate hydration can be maintained or achieved by two different routes: oral intake or parenteral infusion. When oral hydration is insufficient, intravenous (IV) fluid infusion is the commonly used route. However, subcutaneous (SC) infusion of fluid, also known as hypodermoclysis, is an alternative route.

Several studies have compared SC hydration to IV hydration with the main outcome being laboratory test of hydration or subjective assessment scores. They all found similar effects on laboratory markers of hydration, which align with the theory of mass conservation. They also found a similar incidence of side effects between IV and SC hydration as secondary outcomes. The main drawback of these studies is methodological shortcomings. The lack of blinding introduces a large risk of bias on subjective outcome such as assessment scores and grading of side effects. Furthermore, the largest of the studies had a third of their patients switch groups diluting the result. A recent Cochrane review on achieving parenteral hydration found that the quality of included trials was low and future trials should prospectively register, have secure allocation concealment, adequate sample sizes and should be reported according to established standard.

This study will examine if subcutaneous (SC) hydration is a safe alternative to intravenous (IV) hydration in the geriatric patient in the Emergency Department, Acute Assessment Unit or Orthopedic Ward of Aalborg University Hospital. This will be achived by preforming an assessor-blinded, non-inferior, randomized controlled trial.

Relevant participants (see Eligibility Criteria) arriving at Aalborg University Hospital will be enrolled after informed consent. Baseline measurements will be obtained, and the participants will be randomized (1:1) to either intravenous or subcutaneous hydration. A sham setup will be use so both an intravenous access and a subcutaneous access will be visible on the patient, but only one of them will be active. For the next 24 hours the participants will regularly be evaluated by a nurse blinded to infusion for the presence of adverse effects.