Surgical Technique for Lumbar Spinal Catheter Insertion in Pigs Enabling Continuous Access to the Thecal Sac in a Terminal Setup

Summary

We present a technique for inserting a lumbar spinal catheter at the L4-L5 level in a 3-month-old Danish Landrace pig as part of a terminal research protocol, enabling continuous infusion or CSF sampling from the thecal sac.

Abstract

Pigs are increasingly used as a large animal model for pharmacologic CNS research due to the anatomical and physiological similarities between the porcine and human central nervous systems (CNS). However, accessing the cerebrospinal fluid (CSF) in larger pig breeds by conventional lumbar puncture techniques can be challenging due to an oblique orientation of the spinal spinous processes and a limited interlaminar space. Accordingly, an open surgical procedure for inserting a lumbar spinal catheter for continuous CSF sampling at the L4/L5 level in pigs is thoroughly described in this work. After positioning the pig and identifying the anatomical landmarks, a dorsal midline surgical incision is made to expose the spinous processes. By advancing the introducer needle, the spinal catheter is inserted inside the thecal sac of the spinal canal while leaving the bone structures of the spine intact. This method allows continuous infusion into or sampling from the porcine thecal sac with minimal bleeding or CSF leakage. The procedure is simple, time-efficient, and reproducible across different experimental setups, offering significant potential for various pre-clinical studies, including pharmacokinetic research, surgical training, and spinal cord injury models.

Introduction

Animal models are essential when ethical or practical limitations prevent the use of human subjects to investigate diseases or test surgical methods. While rodents are commonly used due to their low cost, their translational relevance is limited by significant differences from humans¹. Pigs, however, offer several advantages compared to rodents, including anatomical and physiological similarities to humans - especially in the context of CNS research^1,2. Canine models have historically served as experimental models for CNS research, but ethical considerations have constrained the use of ....

Protocol

Subjects were housed in compliance with local regulations under the approval of the Danish Animal Experiments Inspectorate (license no. 2020-15-0201-00401). Subject information: Domestic swine, female, approximately 40 kg, 3 months of age.

1. Subject housing and preoperative fasting

1. House subjects in groups at 12 h light/dark cycles in approved housing pens for at least 14 days prior to the procedure to ensure proper acclimatization and reduce stress¹⁷.
2. Ensure that subjects have been on a food withdrawal regime for 12 h prior to the planned anesthesia to reduce the risk of regur....

Discussion

The demonstrated procedure for lumbar catheter insertion for continuous CSF sampling in pigs involves several crucial steps. Firstly, the correct vertebral level must be exposed to ensure optimal conditions for successful catheterization. The porcine spinal cord extends further caudally compared to humans, reaching the S2-S3 level¹⁵, in contrast to the human conus medullaris, which terminates at the L1-L2 level²⁰. Consequently, accessing the lumbar cistern for CSF sampling .......

Materials

Name	Company	Catalog Number	Comments
Adjustable operating table	N/A	N/A
Bair Hugger heater	3M	B5005241003
Bair Hugger heating blanket	3M	B5005241003
Endotracheal tube size 6.5	DVMed	DVM-107860	Cuffed endotracheal tube
Euthasol Vet	Dechra Veterinary Products A/S	380019	phentobarbital for euthanazia, 400mg/mL
Foley Catheter 12F	Becton, Dickinson and Company	D175812E	Catheter with in-built thermosensor
Intravenous peripheral catheter	Avantor	BDAM381344	Size G18
Intravenous sheath	Coris Avanti		Avanti Cordis Femoral Sheath 6F
Monopolar, ForceTriad System	Medtronic
Plastic Syringe, 2 mL	Becton, Dickinson and Company	300928
Primus respirator	Dräger		Respirator with in-built vaporiser for supplementary Sevofluran anesthisa
Self-retaining retractor	World Precission Instruments	501722	Weitlander retractor, self-retaining, 14 cm blunt
Silicone Lumbar Catheter incl. Introducer	Integra	NL8508330
Sterile Saline	Fresnius Kabi	805541	1000 mL
Sterile surgical swaps
Surgical scalpel no 24	Swann Morton	5.03396E+12	Swann Morton Sterile Disposable Scalpel No. 24
Zoletil Vet	Virbac		Medical mixture for induction of anesthesia