Intravenous saline administration in patients with severe acquired brain injury and orthostatic intolerance for tilt-table mobilization

ABSTRACT

Primary objective: This study aimed to investigate the effect of intravenous saline administration on orthostatic hypotension (OH) during head up tilt (HUT) and the change in the renin–angiotensin–aldosterone system before and after HUT in patients with severe acquired brain injury (ABI).

Research design: The study is designed as an observational study.

Methods and procedures: Fourteen patients with ABI, low level of consciousness and OH were monitored before, during and after HUT with non-invasive beat-to-beat blood pressure measurement, and transcranial Doppler determination of middle cerebral artery blood flow velocity. Blood samples were collected before and after two HUT sessions separated by 1 hour and saline was administered in between.

Main outcomes and results: Patients’ ability to stand upright did not change after saline administration due to OH. The patients showed signs of reduced cerebral autoregulation at both HUT sessions. The patients had a significant lower level of renin and angiotensin II but not aldosterone.

Conclusions: Patients with severe ABI and OH demonstrate no improvement in standing time with reduced plasma renin and angiotensin II after two HUT sessions and 1 hour fluid administration. Research focusing on the ability to retain fluid after bed rest is warranted.

KEYWORDS:

• Cerebral autoregulation
• head up tilt
• rehabilitation
• renin–angiotensin–aldosterone system

Acknowledgments

We wish to acknowledge the staff at the Department of Neurorehabilitation/Traumatic Brain Injury, Rigshospitalet, Copenhagen, Denmark

Declaration of interest

The authors report no declarations of interest.

Funding

CGR received two grants for support in analysing data as well as drafting the manuscript. First grant from University hospital Glostrup, Denmark (www.glostruphospital.dk) and the second from the Danish Physical Therapy Association (www.fysio.dk). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.