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Inflammatory Response After Injection of Aqueous Gel Into Subarachnoid Space in Piglets
  1. Tatjana Stopar Pintaric, MD, PhD*,
  2. Admir Hadzic, MD, PhD,
  3. Malan Strbenc, DVM, PhD,
  4. Ozbalt Podpecan, DVM, PhD§,
  5. Matej Podbregar, MD, PhD and
  6. Erika Cvetko, DMD, PhD#
  1. *Clinical Department of Anesthesiology and Intensive Therapy, University Medical Center Ljubljana, Ljubljana, Slovenia; †College of Physicians and Surgeons, Columbia University New York, NY; ‡Bia Ltd, Ljubljana; §Savinian Veterinary Polyclinic, Zalec; ∥Department of Intensive Internal Medicine, University Clinical Center Ljubljana; and #Institute of Anatomy, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
  1. Address correspondence to: Tatjana Stopar Pintaric, PhD, Clinical Department of Anesthesiology and Intensive Therapy, University Medical Center Ljubljana, Zaloska 7, 1000 Ljubljana, Slovenia (e-mail: tatjanas38{at}


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.

Conclusion Subarachnoid injection of ultrasound gel in piglets results in an inflammatory response within neuraxial space.

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  • The work is attributed to Clinical Department of Anesthesiology and Intensive Therapy, University Medical Center Ljubljana, Ljubljana, Slovenia.

    Financial support was provided by the Slovenian Research Agency (P3-0043-0381) and the tertiary funding of the Clinical Department of Anesthesia and Intensive Therapy, University Medical Center Ljubljana.

    Conflicts of Interest and Source of Funding: Tatjana Stopar Pintaric has received a grant (1256593) from hospital’s terciary fundings. For the remaining authors none were declared.