title: Hypothermia decreases cerebrospinal fluid asymmetric dimethylarginine levels in children with traumatic brain injury.
abstract: OBJECTIVE
  Pathological increases in asymmetric dimethylarginine, an endogenous nitric oxide synthase inhibitor, have been implicated in endothelial dysfunction and vascular diseases. Reduced nitric oxide early after traumatic brain injury may contribute to hypoperfusion. Currently, methods to quantify asymmetric dimethylarginine in the cerebrospinal fluid have not been fully explored. We aimed to develop and validate a method to determine asymmetric dimethylarginine in the cerebrospinal fluid of a pediatric traumatic brain injury population and to use this method to assess the effects of 1) traumatic brain injury and 2) therapeutic hypothermia on this mediator.
  
  
  METHODS
  An ancillary study to a prospective, phase II randomized clinical trial of early hypothermia in a tertiary care pediatric intensive care unit for children with Traumatic brain injury admitted to Children's Hospital of Pittsburgh.
  
  
  METHODS
  None.
  
  
  RESULTS
  A UPLC-MS/MS method was developed and validated to quantitate asymmetric dimethylarginine. A total of 56 samples collected over 3 days with injury onset were analyzed from the cerebrospinal fluid of consented therapeutic hypothermia (n = 9) and normothermia (n = 10) children. Children undergoing diagnostic lumbar puncture (n = 5) were enrolled as controls. Asymmetric dimethylarginine was present at a quantifiable level in all samples. Mean asymmetric dimethylarginine levels were significantly increased in normothermic Traumatic brain injury children compared with that in control (0.19 ± 0.08 µmol/L and 0.11 ± 0.02 µmol/L, respectively, p = 0.01), and hypothermic children had significantly reduced mean asymmetric dimethylarginine levels (0.11 ± 0.05 µmol/L) vs. normothermic (p = 0.03) measured on day 3. Patient demographics including age, gender, and nitric oxide levels (measured as nitrite and nitrate using liquid chromatography coupled with Griess reaction) did not significantly differ between normothermia and hypothermia groups. Also, nitric oxide levels did not correlate with asymmetric dimethylarginine concentrations.
  
  
  CONCLUSIONS
  Asymmetric dimethylarginine levels were significantly increased in the cerebrospinal fluid of traumatic brain injury children. Early hypothermia attenuated this increase. The implications of attenuated asymmetric dimethylarginine on nitric oxide synthases activity and regional cerebral blood flow after traumatic brain injury by therapeutic hypothermia deserve future study.
authors: Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, USA.
authors: Bhavani P
authors: BP
authors: Thampatty
authors: Megan M
authors: MM
authors: Klamerus
authors: Patrick J
authors: PJ
authors: Oberly
authors: Kerri L
authors: KL
authors: Feldman
authors: Michael J
authors: MJ
authors: Bell
authors: Elizabeth C
authors: EC
authors: Tyler-Kabara
authors: P David
authors: PD
authors: Adelson
authors: Robert S B
authors: RS
authors: Clark
authors: Patrick M
authors: PM
authors: Kochanek
authors: Samuel M
authors: SM
authors: Poloyac
mesh_terms: D000293:Adolescent; D001120:Arginine / Q000031:analogs & derivatives* / Q000134:cerebrospinal fluid; D001930:Brain Injuries / Q000134:cerebrospinal fluid* / Q000628:therapy*; D016022:Case-Control Studies; D002555:Cerebrospinal Fluid / Q000737:chemistry; D002648:Child; D002675:Child, Preschool; D002853:Chromatography, Liquid; D005260:Female; D006801:Humans; D007036:Hypothermia, Induced; D007223:Infant; D008297:Male; D009566:Nitrates / Q000134:cerebrospinal fluid; D009573:Nitrites / Q000134:cerebrospinal fluid; D053719:Tandem Mass Spectrometry
chemical_list: D009566:Nitrates; D009573:Nitrites; C018524:N,N-dimethylarginine; D001120:Arginine