Contemporary diagnostic and therapeutic equipment and methodologies are becoming increasingly available to the marine mammal clinical veterinarian. It is prudent strategy to maximize use of modem assets and to formulate aggressive diagnostic and treatment plans. Standardized approaches need to be developed for advanced diagnostic and treatment techniques.

This case report describes the intensive care of a mature male Atlantic Bottlenose dolphin and includes illustrations of diagnostic sonography, thoracocentesis, and intravenous fluid therapy. The systematic abdominal and thoracic sonographic survey with normal and abnormal anatomy will be presented. The placement and maintenance of indwelling venous sinus catheters, and the successful thoracocentesis and aspiration of 4.0 liters of pleural effusion will also be presented.

A 19 year old, 256 cm, intact, male Atlantic Bottlenose dolphin Tursiops truncatus had a history of a moderate mature neutrophilia present since June of 1989. The neutrophilia was refractory to prolonged courses of quinolone and cephalosporin treatment. In spite of the neutrophilia, the dolphin remained clinically normal with good appetite, attitude, and performance of learned behaviors. From September of 1992 through December of 1994 the dolphin participated in a clinical trial of a GnRH analog, receiving monthly i.m. injections of 15 mg leuprolide acetate from April through November of 1994. The dolphin responded as expected; developing an initial serum testosterone rise followed by a decrease to less than baseline levels. The testes size as followed by sonography also decreased and the testes became indistinguishable from surrounding viscera. After discontinuation of the leuprolide acetate injections the testes returned to normal sonographic size, shape, and appearance.

On 26 January, 1996 a reduced appetite and episode of vomiting was observed. This was unusual for this dolphin; however, the animal remained bright, alert, responsive, and apparently interested in surrounding dolphins. Endoscopy of the esophagus and forestomach was normal that date. Sonographic evaluation revealed enlarged, asymmetric testes and reduced intestinal motility; thoracic scans were considered normal. A tachycardia was noted. CBC and chemistries from that date were normal, including a normal total WBC count (reduced for this animal). The anorexia persisted for the following two days when repeat hematology revealed a neutrophilia with a left shift, and an elevated ESR. The dolphin was force fed fish, oral fluids were administered, and oral cephalosporin initiated. The dolphin's condition continued to deteriorate with persistent anorexia, unusual vertical posturing, elevated enzyme activities, azotemia, hyperbilirubinemia, persistent tachycardia, and marked degenerative left shift developing.

As the case progressed the dolphin developed some difficulty with buoyancy and became tachypneic. On 31 January the animal was supported in an artificial fleece lined ICU stretcher at the water surface and intravenous fluids, steroids, flunixine meglumine, and gentamicin added to the regime. A 14 gauge x 5 1/2 inch teflon intravenous catheter (Abbocath) was placed into the venous sinus at a caudal intervertebral space. The catheter was placed by palpation of lateral processes of the caudal vertebrae and identification of the intervertebral space. The insertion point was located approximately 5 cm off midline. An 18 gauge x l 1/2 inch needle was inserted to the hub at the insertion point and 1 % lidocaine infused as the needle was withdrawn slowly. Following a surgical prep, the 14 gauge needle was aseptically inserted at the insertion point and into the venous sinus by triangulation to midline. Venous blood flowed freely from the catheter hub when the sinus was successfully entered. A standard 10 drop/ml fluid administration set attached to a 6.0 liter bag of LRS provided a flow rate of approximately 540 ml/hr. Neomycin-Polymyxin-Bacitracin ointment was applied around the catheter at the insertion site. The administration line was routed through an insulated container of warmed water to approximate core body temperature.

Repeat sonography was performed while the dolphin received fluid therapy, on 1 February, and revealed a massive pleural effusion of the right hemi-thorax and persistent tachycardia (HR - 120 bpm). 3.5 MHz 17 cm linear array transducer was used to scan the abdomen and thorax with the animal suspended in the ICU stretcher. The transducer was positioned so that cranial appeared to the right during frontal or sagittal scans and dorsal was to the right on transverse scans. Frontal scans over the right hemi-thorax revealed a relatively hypoechoic fluid accumulation in the pleural space. The maximum horizontal dimension of the fluid accumulation was greater than 4.0 cm.

An ultrasound guided thoracocentesis of the right hemi-thorax was performed with the dolphin in the ICU stretcher. The skin surface at the intercostal space overlying the area of maximal horizontal dimension of fluid accumulation was surgically prepared. An 18 gauge x l 1/2 inch needle was inserted to the parietal pleura at the caudal extent of the intercostal space and 1 % lidocaine infused as the needle was withdrawn. A partial thickness stab incision was made through the blubber with a No. 15 blade. Finally, a 14 gauge x 120 mm pneumoperitoneum needle with stopcock (Surgi needle) was introduced into the right pleural space and connected with suction tubing to a portable surgical suction unit. Active suction yielded straw colored, cloudy fluid. After aspiration of approximately 3400 cc of fluid the horizontal dimension of the hypoechoic pleural space was measured at the point of thoracocentesis needle insertion as 1.4 cm. An additional 600 cc of fluid was recovered and the insertion site again scanned; the pleural space was measured at less than 4 mm. Fluid analysis yielded an exudate and an unidentified suspect protozoan or amoebae was reported. An ECG signal was continuously monitored with an MDE Escort- portable patient monitor. The tachycardia and tachypnea resolved following the centesis; HR returned to 66-90 bpm and RR went from 23 to 1 1 per five minutes.

The dolphin was returned to the water and died seven hours later. Gross lesions at necropsy included; an intense generalized polyserositis, a chronic appearing ulcerative lesion involving the entire pyloric stomach, myocardial scarring, and a generalized lymphadenopathy. Ameboid organisms seen in the centesis fluid were also visualized histologically within a layer of granulation tissue overlying the visceral pleura. Aseptically collected tissues have been forwarded to CDC for amoebae isolation and identification attempts. To date the organism is growing successfully in culture but is unidentified.

The fluid administration rate achieved with the configuration in this case was less than optimal for correction of fluid losses or shock treatment. Configurations using larger bore catheters and the simultaneous placement of multiple catheters should be investigated.

It is interesting to note the effusion in the case of this report was right-sided as was that in a stranded male Tursiops truncatus of simular length which was successfully resolved by ultrasound guided thoracocentesis as reported by Rhinehart et al. It is further interesting that histopathology of the right lung revealed interstitial edema after the aspiration of 4.0 liters of fluid. Rhienhart et al suggested a maximum of 3.0 liters be removed at one time to avoid possible "rebound edema". Although in this case a concurrent significant cellular infiltrate and the presence of the ameboid organisms raises questions as to the etiology of the observed edema. Finally, it is also interesting to note the resolution of the tachypnea and tachycardia following thoracocentesis in both cases.

Thoracic sonograms in this case were obtained by systematic grid pattern as described by Stone. Our experience is in concurrence with hers regarding the limitations of abdominal radiology. There are also frequent occasions in marine mammal medicine when bringing radiology equipment to the patient location is not possible or when transport of the patient to the equipment is contraindicated as in this case. We further agree with Dr. Stone that development of normal values for marine mammal cardiac parameters, fetal biophysical scoring standards, and monographic descriptions of normal and pathologic abdominal organs should be aggressively pursued. A logical first step in this process is the development of systematic transducer orientation and comparison of echogenic patterns between imaged organs.

References

1.  Rhinehart, H., Townsend, F., Gorzelany, J. and Broecker, S. (I 994) Ultrasound-Aided Thoracocentesis of a Bottlenose Dolphin International Association for Aquatic Animal Medicine 25th Annual Conference Proceedings. pp. 175-179.

2.  Stone, L. (1990) Diagnostic Ultrasound in Marine Mammals In: Handbook of Marine al Medicine: Health, Disease and Rehabilitation, L. Dierauf Ed., CRC Press, Boca Raton, FL. pp. 235-264.