Abstract

Vascular catheterization is important during general anesthesia; however, gaining reliable access in pinnipeds can be challenging. Venous catheterization allows for rapid delivery of various medications, fluids, and for monitoring blood parameters during anesthesia. Venous catheters can remain in place during recovery and can be useful for long term post-operative intravenous treatment. Arterial access is also useful for monitoring blood parameters (especially blood gases) and can be used for measurement of direct blood pressure.

Two specialized catheter systems (epidural and peel-away) have proved useful for catheterization of pinniped blood vessels. Epidural catheters consist of a long needle with a right angled port (Tuohy needle) that allows 'through the needle' catheter passage at an acute angle. Peel-away catheter kits consist of an introducer catheter that is used to enter the vessel and then peeled away after a long term catheter is passed through.

California sea lions (Zalophus californianus) have vessels in their flippers that are sometimes used for venous access. These vessels can be difficult to catheterize, especially with peripheral vasoconstriction that accompanies general anesthesia. Cephalic and saphenous vessels can also be used, but can be difficult to locate. The caudal gluteal vein, also commonly used for venipuncture, is small, deep, and difficult to catheterize, even with the aid of ultrasound imaging. Sublingual veins can be catheterized, but they are typically small and fragile and can be difficult to maintain. The jugular vein is visible sonographically and ultrasound guided placement of epidural and peel away catheters can be readily accomplished. The carotid artery, also imaged with ultrasound, can be catheterized similarly. (Extreme caution is advised when attempting to catheterize a major artery, to minimize trauma, hemorrhage, and clot formation).

Pacific harbor seals (Phoca vitulina) have peripheral vessels that pose the same challenges for catheterization during general anesthesia as those of sea lions. Seals also have a large epidural sinus (vertebral vein) that is commonly used for blood collection. Complete catheterization of this sinus is nearly impossible with conventional catheters, due to the depth and (required) near perpendicular placement of the needle. For this reason, epidural catheters, designed for perpendicular placement, are very effective. The jugular vein and carotid artery are visible with ultrasound and ultrasound guided placement of both the epidural or peel-away catheters can be performed, as in the California sea lion.

With practice, pinniped blood vessels can be consistently catheterized. Routine vascular catheterization is a useful addition to most anesthetic procedures.