Abstract
Indwelling catheters are commonly used for fluid administration and drug therapy. They also provide intralesional access, drainage and drug administration. This use of catheters has been a mainstay in human and terrestrial animal medicine but has significant limitations when applied to the care of dolphins. While catheters used in humans are traditionally secured via adhesives and bandages, the aquatic environment and rapid epithelial turnover exhibited in the dolphin render these methods ineffective in this species.2 Additionally, the catheter incision site provides a pathway for secondary infections when animals are returned to the water. In an attempt to address these specific issues of securing and protecting indwelling catheters in dolphins, veterinarians have employed various custom solutions including adhesives, sutures and belts or straps that encompass the entire dolphin body. However, these strategies have several shortcomings including the restriction of dolphin mobility, incomplete isolation of incision site from the aquatic environment, and unreliability of device attachment in durations over 24 hours. Suction-based devices were also explored, but their unreliable attachment time reduces their effectiveness.1 These shortfalls in existing techniques demonstrated a need for a method of effectively securing a catheter to a dolphin and isolating the catheter site from the aquatic environment for several days. To address this need a catheter isolation unit (CIU) was designed with several functional requirements serving as a guide. These requirements were: to secure the catheter to the dolphin for a minimum of 72 hours, to isolate the catheter entry site from the environment, to allow for repeated catheter access, to be compatible with standard catheters, and to provide animal comfort and safety. The CIU isolates and protects the catheter by using a soft silicone gasket (Ecoflex® GEL) as a waterproof seal between the CIU and the skin of the dolphin. The seal is compressed against the body of the dolphin with an array of two co-radial, alternating sets of angled acupuncture needles. The compliancy of the gasket maintains a seal under the expected dynamic changes of surface curvature due to dolphin movement. Finally, the device is surrounded by a clear hydrodynamic cover, which reduces drag, isolates the incision site from the aquatic environment, and allows repeated access to a catheter without removal of the entire device. The transparency of the cover allows the incision site to be non-invasively observed. A variety of preliminary tests have shown that the dolphins display little to no behavioral response to the application of needles and the tissue trauma appears insignificant. The CIU is compliant to a variety of surface topologies and dynamically changing radii of curvature ranging from 100 to 1000 mm while maintaining isolation of the incision site from the aquatic environment. The CIU is also robust under moderate hydrodynamic forces.
Acknowledgments
The authors would like to thank Professor Alexander Slocum, Dr. Nevan Hanumara, Nikolai Begg, Folkers Rojas, and Dave Custer of the Massachusetts Institute of Technology Department of Mechanical engineering, and also the entire veterinary staff of the Navy Marine Mammal Program for their assistance in conducting prototype testing and for their expert input.
* Presenting author
Literature Cited
1. Baird R. 1998. Studying diving behavior of whales and dolphins using suction-cup attached tags. Whalewatcher 31:1:3–7.
2. Hicks B, Aubin D. 1985. Epidermal growth in the bottlenose dolphin, Tursiops truncates. Journal of Investigative Dermatology 85:1:60–63.