Risk factors

Osmolarity formulae can predict risk in DKA


Hyperosmolarity in people with diabetes ketoacidosis appears to be an independent predictor of mortality and other adverse outcomes.

A retrospective study from the Australian and New Zealand Intensive Care Society (ANZICS) Adult Patients Database, comprised data from more than 17,000 patients with diabetes ketoacidosis admitted to ICUs over a 15-year period.

Serum osmolarity was calculated using the formulae = 2× sodium + glucose + urea (all values in mmol/l) and hyperosmolarity was defined as ≥320 mOsm/L.

The study found people with hyperosmolarity were older (median 51 years v 33 years), had a higher average APACHE 11 score (20 v 12), and had more comorbidities (1.9 v 1.4 respiratory; 3.8 v 2.1 cardiovascular; 0.9 v 0.5 liver and 4.4 v 1.8 renal) than those with normal osmolarity.

They also demonstrated worse values on multiple indexes of illness severity including degree of acidosis and renal function.

Importantly, those with hyperosmolarity had significantly increased mortality with adjusted odds ratios of 4.98 for patients in the range 320-349 mOsm/L and 9.69 for patients ≥350 mOsm/L.

Patients with hyperosmolarity also had a higher incidence of adverse outcomes such as renal failure and need for mechanical ventilation, prolonged length of ICU and hospital stays, and were more likely to be discharged to a nursing home compared with patients with normal osmolarity.

“The effect of osmolarity remained highly significant even after controlling for multiple potential confounders, and could be observed regardless of the severity of acidosis,” the study said.

“This suggests that osmolarity may provide benefit for risk stratification in addition to the factors currently utilized in clinical guidelines.”

The researchers noted hyperosmolarity was a simpler indicator of risk than APACHE which was “too complex to be readily used as admission screening tools”.

However their findings could probably not be extrapolated to people with lower acuity disease managed in the ward.

They said more research was required to optimise risk stratification and identify which interventions would lead to improved outcomes in those found to be at increased risk.

“In particular, the ideal fluid resuscitation strategy and rate of correction in ketoacidosis with hyperosmolarity needs to be determined and incorporated into clinical guidelines.”

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