Association Between Serum Sodium Abnormalities and Clinico-radiologic Parameters in Severe Traumatic Brain Injury

Philip Mwachaka1,2, Angela Amayo3, Nimrod Mwang’ombe1, Peter Kitunguu1
1Department of Surgery, Neurosurgery Unit, University of Nairobi, Nairobi, Kenya.
2Department of Human Anatomy, University of Nairobi, Kenya.
3Department of Pathology, University of Nairobi, Nairobi, Kenya.

Correspondence to: Dr. Philip Mwachaka; Email: pmaseghe@gmail.com

Received: 16 June 2020; Revised: 13 October 2020; Accepted: 9th January 2021; Available online: 3rd March 2021

Abstract

Background: Secondary brain insults after traumatic brain injury such as electrolyte dysfunctions are associated with poor outcomes. This study aimed at determining the incidence of serum sodium ion abnormalities and their association with clinico-radiological parameters. Methods: A prospective cross-sectional study of one hundred and seventeen patients with severe head injury. Data collected included patient demographics, prehospital interventions, clinical examination findings, computed tomography (CT) scan head findings, serum sodium ion levels (at admission and 48 h later), and outcome (30 days). Results: At admission, 93(79.5%) patients had normal serum sodium ion levels. However, 48 h post-admission, hypernatremia was prevalent in 56(63.6%) patients (p < 0.001). Hypernatremia was significantly associated with the use of mannitol (p = 0.036), lower Glasgow Coma Score (p = 0.047), higher Injury Severity Score (p = 0.015), presence of subdural hematoma (p = 0.044), midline shift >5 mm (p = 0.048), compressed/absent basal cistern (p = 0.010), and higher Rotterdam CT Score (p = 0.003). Hypernatremia reported 48 h post-admission was associated with a high 30-day mortality rate [odds ratio (OR) 3.55, p = 0.0095]. Risk of mortality associated with hyponatremia and hypernatremia at admission was not statistically significant. Conclusion: While both hyponatremia and hypernatremia can occur in serious TBI patients, hypernatremia predominates 48 hours post-admission and is associated with statistically significant increased risk of death.

Keywords: Traumatic brain injury, hyponatremia, hypernatremia, outcomes, clinico-radiologic parameters

Ann Afr Surg. 2021 ; 18(3): 155-162

DOI: http://dx.doi.org/10.4314/aas.v18i3.6

Funding: None

© 2021 Author. This work is licensed under the Creative Commons Attribution 4.0 International License.

Introduction

Serum sodium abnormalities are common in traumatic brain injury (TBI), and are usually associated with the primary brain injury or interventions such as hyperosmolar therapies used in the management of raised intracranial pressure (1, 2). Hypernatremia, defined as serum sodium ion concentration >145 mmol/L, can result from a primary brain injury resulting in central diabetes insipidus or as a result of hyperosmolar therapies such as the use of hypertonic saline (3, 4). Hypernatremia is associated with increased mortality, longer hospitalization and greater hospital costs (3–5). Hyponatremia, serum sodium ion concentrations <135 mmol/L, may also occur after TBI and contributes to secondary brain insults by causing cerebral edema, seizures, and depression of consciousness (6). Hyponatremia in TBI is usually caused by cerebral salt wasting syndrome and syndrome of inappropriate secretion of antidiuretic hormone (7).

Severe TBI, defined as Glasgow Coma Scale (GCS) ≤8, is a major cause of death and incapacity worldwide and is associated with huge direct and indirect costs to the public (8–10). In addition, the World Health Organization projected that by 2020, TBI would be the main cause of death and disability (11). TBI is more prevalent in developing nations because of the increasing number of road traffic accidents (12, 13). In our setup, most hospital-based studies have revealed that severe head injury is associated with mortality of >50% and poor functional outcomes (14–16). These bad outcomes may be associated with secondary brain insults such as electrolyte abnormalities that arise from inflammatory and biochemical cascades initiated by the primary injury insult to the brain (9, 17, 18). This study aimed at determining the incidence of serum sodium ion abnormalities in severe TBI patients, and their association with specific clinical and radiological parameters.

 

Materials and methods

Study design and site

An analytic cross-sectional study carried out over 4 months (1st November 2019 to 28th February 2020). The study site was the Kenyatta National Hospital Accident and Emergency Unit and Intensive Care Unit. Kenyatta National Hospital is located in Nairobi, Kenya and is the largest hospital and the main referral center for neurotrauma cases countrywide. The hospital serves patients from different regions and socioeconomic backgrounds.

 

Study population

All consecutive patients presenting with severe head injury defined by GCS ≤ 8 and whose next of kin had given informed consent were recruited into the study. Patients with known pre-existing chronic illness were excluded from the study.

 

Study variables

Data collected included patient demographics, mechanisms of injury, prehospital interventions, clinical examination findings, computed tomography (CT) scan head findings, serum sodium levels (at admission and 48 h later), and outcome (30 days). The Injury Severity Score (ISS) was used to quantify the severity of injury to the patient (19). The serum sodium tests were done using Biolis 50i Superior Chemistry Analyzer (Boeki Medisys, Tokyo, Japan). Daily internal quality control checks were done to ensure that the results were valid. In addition, external quality control checks were done through the Randox International Quality Assessment Scheme (RIQAS). The reference range for serum sodium from our laboratory is 135–145mmol/L.

 

Statistical analysis

Data gathered was entered into Statistical Package for Social Sciences (SPSS) version 20.0 (IBM Corp; New York, United States of America) for analysis. Metric data are shown as means and standard deviation, nominal data as frequency and valid percent. Variables were tested for normal distribution using the Kolmogorov–Smirnov test in addition to histograms. If the assumption of normality was violated, Mann–Whitney U and Kruskal–Wallis tests were performed to test for differences between groups, instead of Student's t-test and analysis of variance (ANOVA) tests, respectively. Admission and 48-h post-admission variables were compared using the paired t-test. Categorical data was analyzed by Pearson’s chi-square test. The correlation between the serum sodium and the study variables (clinical and radiol