Hyponatremia In The Acute Stage After Traumatic Cervical Spinal Cord Injury And Discussion On Mechanism Of Hyponatremia

Objective: With the development of society, the incidence of traumaticcervical spinal cord injury increase dramatically.The mortality of patients withcervical spinal cord injury always is high during acute stage.Thecomplications of spinal injury threaten to patients with cervical spinalinjury,such as hyponatremia, respiratory depression etc. Hyponatremia iscommom in the early stage post-SCI.The clinician all the time try to avoidhyponatremia and research mechanism of which thteaten topatients.Consecutive individuals with cervical spinal trauma were included inour cohort of patients, who we have retrospective study on and discussion onrelationship between degree of spinal injury and hyponatremia. The purposeof our study is to explore mechanism of hyponatremia.Methods:1、Case collection We selected52patients with acute isolated cervicalspine trauma for the retrospective cohort study who were admitted in ourhospital emergency room during2009-01~2011-02.There are38spinal cordinjured individuals(14women and24men; ages16-82years with a mean of45.5year)and14control cases(5women and9men; ages18-70years with amean of42.3years).We excluded patients with polytrauma, individuals withhistory of previous systemic or renal diseases, individuals who had diarrhea orileus that required “nil per os,” and patients who often received medicationwith potential effects on electrolyte levels (e.g., carbamazepine, enemas,laxatives, diuretics, and angiotensin converting enzyme inhibitors)during thefirst2weeks after spine trauma. Neurologic classification of the severity ofSCI through assessment of motor and sensory impairments followed theAmerican Spinal Injury Association Impairment Scale(AIS),as described inTable1. All selected cases were divided into a SCI group(individuals with acute cervical SCI)and a control group(individuals with spine trauma and anormal neurologic evaluation at admission).We also divided these cases intoseven groups(1-7) on basis of the level of cervical SCI.2、Specimen collection In the morning,we collected serum samplefrom patients with an empty belly since adimitted in the hospital24hours andthen we make repeated trials using the same ways in the nine days thatfollowed. These samples were analyzed for change of electrolyte and the dataof blood pressure were recorded twice a day.Also we recoreded intake andoutput volumes on patients with spine trauma without motor or sensoryimpairment and spinal cord injured individuals.3、Test for serum sample and standard Serum sample is tested in thehospital laboratory. Hyponatremia is defined as a serum sodium concentrationbelow135mmol/L in2consecutive blood samples. Patient charts arereviewed with particular interest in demographics (age and gender),causes ofSCI, neurologic assessment (severity and level of SCI), serum sodiumconcentrations during the first10days posttrauma, medications, and anyinformations on preexisting medical conditions.Meanwhile the blood pressureof patients measured by traditional method are recorded in the chart. Meanarterial pressure is estimated for each day post-SCI acoording to the followingequation: MAP=([2*diastolic pressure]+systolic pressure)/3.Result: Hyponatremia occurred in85.7%after SCI, which issignificantly more frequent than the control group.Patients have either motorcomplete(16/38)or motor incomplete(22/38)tetraplegia. The majority of spinalcord injure dindividuals(46/52,or88.5%)underwent surgical procedures fordecompression and/or stabilization of spine.However, there was no significantassociation between hyponatremia and surgical treatment(P=1).The SCI groupshowed a significantly lower nadir of serum sodium concentration incomparison with the control group(134.7±6.1vs140.1±1.8mmol/L.P<0.05).Hyponatremia is closely related with degree of SCI. Hyponatremia gets worseas degree of SCI developed which is not closed related with level of SCI.Among spinal cord injured individuals, hyponatremic patients showed lower mean MAP than normonatremics during the first10days posttrauma(P<0.05).Although there was no significant difference between control and SCI groupsin terms of overall fluid balance（360±117.38vs310±110.05ml；P=0.63）,spinal cord injured individuals had significantly greater intake and outputvolumes（5810±493.18ml vs5450±497.21ml）in comparison with patientswith spine trauma without motor or sensory impairment (2890±255.82ml vs2580±214.99ml).Conclusion: Hyponatremia is a common electrolyte abnormality withinthe first10days after traumatic cervical SCI.Our results suggest thathyponatremia is associated with degree of SCI. Hyponatremia gets worse asdegree of SCI developed according to AIS. Additionally,hyponatremicindividuals with SCI showed greater evidence of neurogenic hypotension thannormonatremic individuals with SCI in our study. Our results also suggest thathyponatremia is associated with the integrity of descending renal sympatheticcircuits which mediate the renin-angiotensin response to neural injury,in thesetting of neurogenic hypotension with cardiovascular dysfunction.Wepostulate that the factors contributing to hyponatremia in the early stage aftertraumatic cervical SCI include neural and hormonal effects in the setting ofneurogenic hypotension with cardiovascular dysfunction.