Dehydration and acute kidney injury

The Cochrane review found that several commonly used signs should not be relied on individually to diagnose or exclude dehydration in older people: fluid intake records, urine colour, urine specific gravity, urine volume, heart rate, dry mouth and feeling thirsty ²³. Only a few signs, such as missing drinks between meals and expressing fatigue, showed any promise, and none was consistently useful across studies ²³. The review used a blood test, serum osmolality, as its reference standard ²³.

Acute kidney injury is a sudden fall in kidney function. “Sick day” guidance suggests pausing some medicines during an illness with poor intake, including diuretics, ACE inhibitors, angiotensin receptor blockers, anti-inflammatories, metformin and sulfonylureas ²⁴.

The evidence for this practice is thin. A 2017 systematic review found six studies, all in hospital, around coronary angiography or cardiac surgery. It found no studies of stopping medicines during an intercurrent illness in the community ²⁴. A decision to pause or restart a medicine belongs with the prescriber, who weighs it against the reason the medicine was started.

In the Canadian trial of treating chest infections in the nursing home, rehydration in the facility was part of the pathway that reduced hospital admissions without a difference in deaths ²¹. Whether fluids can be given under the skin or into a vein in a particular facility depends on its staffing, equipment and the treating doctor.