Evaluation of development of diabetes insipidus in the early phase following traumatic brain injury in critically ill patients

Introduction

The purpose of this study was to define the prevalence and outcome of diabetes insipidus (DI) in the early post-traumatic brain injury (TBI) period in ICU patients. Inadequate antidiuretic hormone secretion, which results in DI, is a well recognized complication of TBI, owing to post-traumatic posterior pituitary dysfunction.

Methods

This prospective study was performed in 73 ICU-TBI patients (with or without multisystem trauma) admitted to a general ICU at a tertiary center between December 2005 and November 2007. Patients had suffered severe TBI, according to the initial GCS score (≤ 8). DI was diagnosed if plasma sodium exceeded 145 mmol/l in the presence of inappropriate dilute urine with 24-hour urine volume >30 ml/kg body weight, urine specific gravity <1,005 or urine osmolality <300 mOsm/kg with a simultaneous plasma osmolality ≥ 300 mOsm/kg. The age, gender, GCS, Injury Severity Score (ISS), onset of DI, peak recorded plasma sodium and outcome were noted. Statistical analysis was computed by t test and Fischer exact test. P < 0.05 was considered statistically significant.

Results

Twenty-one ICU-TBI patients (28.7%) developed acute DI. Comparison was made between two groups of these patients: Group A, nine survivors and Group B, 12 nonsurvivors of TBI. There was no statistical significance between them with respect to age, gender (P > 0.05). Group B had a lower GCS (4.5 ± 1.5) as compared with Group A (7.8 ± 3, P = 0.003). The ISS was significant greater in Group B: 38 ± 8 versus 17 ± 7 in Group A, P < 0.001. Peak plasma sodium was significantly greater in Group B: 167 ± 4 mmol/l versus 156 ± 3 mmol/l in Group A, P < 0.05. The mean onset time of DI in Group B (1.7 ± 0.9 days) was shorter than in Group A (7.4 ± 3.3 days), P = 0.004. Overall mortality was 57.1%. The mortality rate for the development of DI within the first 3 days after TBI was 90% versus 27.2% if DI occurred later. Nonsurvivors died from brain death and not as a result of their associated injuries.

Conclusion

Our results demonstrate that DI is common, following severe TBI. ICU-TBI patients presenting with features of DI have an overall high mortality. This study shows that the development of DI within the first 3 days of TBI is associated with high mortality rate and impending brain death. On the contrary, ICU-TBI patients who develop DI later have a better prognosis.