Abstract

Vascular access in all species is important for diagnostics and fluid/medication administration. With their unique appendicular anatomy and thick body wall, pinnipeds can present a challenge to clinicians wishing to obtain vascular access. Through dissection of necropsy specimens, study of anatomical diagrams, comparison to domestic species, diligent ultrasound, and the availability of specialized catheter systems, vascular access in pinnipeds has advanced. Lingual veins are visible and accessible in most pinniped species. Though small in size, lingual vessels are useful for blood gas analysis and emergency administration of medications in the moribund or anesthetized patient. Like most species, pinnipeds have large jugular veins and carotid arteries in the neck. California sea lions have been shown to have equally large internal and external jugular veins. The jugular vein (especially the external jugular vein) is useful for venipuncture and catheterization. In small otariids, the external jugular vein is visible/palpable with the animal positioned in dorsal recumbancy and/or when pressure is applied to the thoracic inlet. In large otariids, ultrasound visualization is helpful for jugular access. Long-term jugular catheters have been maintained in several otariid species and are useful during anesthesia, anesthesia recovery, and in critically ill patients. The carotid artery may be entered, but poses risk and is not recommended. The large subclavian/brachiocephalic vein (also called the precaval vein) is located in the angle between the manubrium sternum and first rib in most pinniped species, and can be entered blindly (by anatomical land marks) or with ultrasound guidance. These vessels are mostly used for emergency vascular access. The forelimbs provide access to several different vessels in otariids. The superficial palmar vein (sometimes referred to as the brachial vein) is often visible/palpable and has been used for venipuncture and catheterization. The median artery can sometimes be palpated on the medial surface of the forelimb and is readily imaged via ultrasound in California sea lions. Catheterization of this artery is useful during anesthesia for direct blood pressure measurement and arterial blood gas evaluation. The caudal gluteal vein in otariids can be sampled via anatomical landmarks, and is a common site for venipuncture. However, it is a difficult structure to catheterize. The dorsal digital veins in the flippers of otariids and phocids, and the epidural vertebral vein (also known as the extradural intervertebral vein, vertebral sinus, etc.) in phocids are useful for venipuncture and catheterization. Long-term catheters in the epidural vertebral vein have been maintained during anesthesia, anesthesia recovery, and in critically ill seals (harbor seal, gray seal, and Hawaiian monk seal). Some pinnipeds have large vessels in the tarsal region, namely the saphenous (which becomes the medial plantar distally) artery and vein. The saphenous artery has been successfully catheterized in an African fur seal and in Pacific harbor seals during anesthesia, and is useful for direct blood pressure determination and arterial blood gas analysis in both species. The saphenous vein has been catheterized in a Hawaiian monk seal under anesthesia. The vessel is readily imaged via ultrasound and has also been demonstrated in Pacific harbor seals. The intraosseous space is also useful for vascular access. A power driven, screw-in type, self-tapping bone marrow needle has been placed in the tibia and radius of California sea lions during anesthetic procedures. Vascular access is important. With continued practice and investigation, vascular access in pinnipeds will continue to advance.

* Presenting author