title: Inflammatory response after injection of aqueous gel into subarachnoid space in piglets.
abstract: BACKGROUND
  Ultrasound-guided neuraxial anesthesia requires the application of ultrasound gel between the transducer and the skin to avoid signal drop-off. As the needle is inserted, the gel may be introduced intrathecally. The purpose of this study was to examine the evidence of an inflammatory response in the subarachnoid space after intrathecal gel introduction.
  
  
  METHODS
  Twelve piglets were sedated with azaperone 0.5 mg/kg intramuscularly and anesthetized via face mask (2%-4% isoflurane in 50% air-oxygen mixture). After collection of cerebrospinal fluid by lumbar puncture with a 22-gauge needle (baseline), 0.2 mL of ultrasound gel mixed with 1 mL of saline was injected intrathecally into 9 piglets (gel group). In 3 piglets (control group), 1 mL of saline was administered. Behavioral and neurologic assessments were recorded on a 4-grade scale. Following the preinjection and postinjection cerebrospinal fluid collection, the piglets were killed, and samples of spinal cord with meninges were excised. Five cross sections (1 mm apart) were processed using immunohistochemistry.
  
  
  RESULTS
  After anesthesia, all piglets displayed short-lived mild (grade 1) motor and behavioral deficits. Mean ± SD protein concentrations in the gel and baseline samples were 14.1 ± 3.0 and 1.3 ± 0.5 g/L, respectively (P = 0.001). No differences were found in protein concentration between baseline (1.8 ± 0.7 g/L) and control samples (2.8 ± 0.8 g/L) (P = 0.4). In the gel group, numerous immunopositive cells were found in the pia, arachnoid, and inner layer of dura.
  
  
  CONCLUSIONS
  Subarachnoid injection of ultrasound gel in piglets results in an inflammatory response within neuraxial space.
authors: Clinical Department of Anesthesiology and Intensive Therapy, University Medical Center Ljubljana, Ljubljana, Slovenia. tatjanas38@gmail.com
authors: Tatjana Stopar
authors: TS
authors: Pintaric
authors: Admir
authors: A
authors: Hadzic
authors: Malan
authors: M
authors: Strbenc
authors: Ozbalt
authors: O
authors: Podpecan
authors: Matej
authors: M
authors: Podbregar
authors: Erika
authors: E
authors: Cvetko
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal / Q000187:drug effects; D015415:Biomarkers / Q000134:cerebrospinal fluid; D002556:Cerebrospinal Fluid Proteins / Q000378:metabolism; D005782:Gels / Q000008:administration & dosage / Q000633:toxicity*; D007150:Immunohistochemistry; D007249:Inflammation / Q000134:cerebrospinal fluid / Q000139:chemically induced* / Q000276:immunology; D007278:Injections, Spinal; D008297:Male; D008578:Meninges / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D009043:Motor Activity / Q000187:drug effects; D013116:Spinal Cord / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D013346:Subarachnoid Space; D034421:Sus scrofa; D018084:Ultrasonography, Interventional / Q000009:adverse effects* / Q000379:methods
chemical_list: D015415:Biomarkers; D002556:Cerebrospinal Fluid Proteins; D005782:Gels