Ultrasonography was used in a relatively new procedure on cetaceans to diagnose the presence of excessive fluid in the right pleural cavity of an adult stranded Tursiops truncatus being treated at Mote Marine Laboratory, Sarasota, Florida. Ultrasound imaging was invaluable both during the procedure and to document progress over the course of therapy aided by the ultrasound, the chest was successfully tapped six times over the one month course of treatment to remove a total of 13 liters of fluid.
Thoracentesis is best accomplished by first using the ultrasound to locate the proper site for the procedure. This is done by scanning for the maximal fluid accumulation on the ventral chest, measuring the skin-to-fluid distance, and locating the anterior margin of the nearest rib. Guided by this information the skin is surgically prepped a 14-16 g x 2 1/4" catheter with stylet is then directed into the thorax perpendicular, and immediately adjacent to the anterior edge of the rib. With the stylet removed, one end of thoracentesis tubing set is attached to the needle hub, and the other end inserted into a one liter evacuated bottle. No more than 3 liters per day should be removed to avoid a possible "rebound effect" resulting in pulmonary edema of the affected lung.
Once the catheter is in place the animal is returned to the water. Minor adjustments of the catheter are possible by moving the tubing, but once flowing freely it's best to not disturb the catheter. Following aspiration of the pleural fluid, antibiotics and/or diuretics can be administered intra thoracically via the catheter before its removed. Ultrasound examination can then be repeated to measure any remaining fluid, and to document progress over the following days.
Our ability to successfully diagnose and treat sick or injured marine mammals has grown dramatically in recent years. Greater medical and scientific knowledge gained from display/research animals, the newest in human and animal drug therapies, and more sophisticated diagnostic technologies have all contributed to recent successful rehabilitation efforts. Diagnostic ultrasound imaging has become one such invaluable tool in the diagnosis and medical management of marine mammal medicine, particularly for cetaceans. Not only can ultrasonography be used to diagnose; it can also aid in treatment and the follow-up of disease conditions to document progress.
On 7 June, 1993 a stranded 254 cm adult male bottlenose dolphin (Tursiops truncatus) was rescued from a tidal marsh along the central west Florida coast by stranding team personnel from Mote Marine Laboratory, Sarasota, Florida. The dolphin presented with an inability to surface on his own, a strong right-sided list, shallow rapid breathing, tachycardia, inappetence, and shark bite wounds on his right peduncle which revealed a tooth from a bull shark embedded in the lateral process of one vertebra. Laboratory findings included a slightly elevated WBC, anemia, moderately elevated liver function values, a decreased RP, and an elevated ESR. Initial treatment was begun with ciprofloxacin, penicillin UK, cimetidine, oral fluids, and physical support.
On 9 June, to determine the cause of the right-sided list, an ultrasonographic examination of the right and left thorax was conducted using a Corometrics Medical Systems, Rloka model I 18 console with a 3.5 MHz mechanical sector scanner. The video images from the ultrasound console were split to both a Sony model UP-850 thermal printer and also an 8mm video camera (Sony Handy camcorder CCD-SP7) to provide still images and video/audio recordings simultaneously.
Viewing the echo patterns directly through the video camera increases the mobility of the sonographer. These examinations are typically performed outdoors where sunlight makes it very difficult to view the console monitor. With one eye viewing the camcorder image, and the other eye to observe the location of the scanner probe, the sonographer can easily perform a complete examination.
Recording a running narrative including frequent comments on surface anatomic location, orientation of the probe, direction of the sonographic beam, and pertinent findings onto the audio/video tape is very important for the purpose of reviewing the findings or when sending the tape out for evaluation. In order to record audio onto the 8mm tape, it was necessary to run the signal through a small external microphone wired to the camcorder via a tape recorder (set on "pause") and a small pre-amp.
The thoracentesis itself was accomplished using a 14-16g x 2 1/4" nylon iv catheter with stylet (Cathlon IV #4452), a 30" thoracentesis tubing set (Abbott Laboratories #4653), and 1,000 ml empty evacuated containers (Abbott Laboratories #1614-05).
Visualization of the right thorax revealed a 3-4 cm fluid-filled space separating the lung pleura from the chest wall. No such lesion was noted in the left thorax, although ventral consolidation of both lungs allowed good visualization of the heart. Hided by the ultrasound images the thoracentesis was performed.
The dolphin was gently lifted from the water in order to place the chest drain. The ultrasound examination was utilized to locate the largest fluid accumulation in a ventral location, measure the distance from the skin surface to the fluid space, and to note the anterior margin of the nearest rib. Once a suitable location was found, the area was surgically prepped. Next, using aseptic technique, the catheter (with stylet in place) was directed perpendicular to the body wall and introduced immediately anterior to the rib, avoiding the posterior rib margin with its associated vascular components. Once advanced to the proper depth, the stylet was removed, and the tubing was connected and inserted into the evacuated bottle. With the catheter in place, the dolphin was returned to the water and held at the surface for the duration of the procedure which lasted approximately thirty minutes.
Initially the catheter was secured by hand at the insertion site, but inadvertent movement predisposed the catheter to crimping. It was discovered that the fluid evacuation from the chest was enhanced if the catheter was not held directly, but rather the veterinarian or technician supported the evacuated bottle and the thoracentesis tubing to maintain the catheter at approximately 90 degrees to the body wall.
It was decided to remove a maximum of three liters per day until the condition resolved to avoid the possibility of a "rebound effect" of pulmonary edema. During one treatment, the obtained fluid presented bloody versus the previous serosanguinous drainage. However, a STAT hematocrit confirmed that the catheter placement had not penetrated any major thoracic vasculature.
Initially this procedure was repeated daily for three days. A decrease in the angle of body listing was noted, the rate and character of respirations improved dramatically, and the heart rate had returned to normal. On day 4 the dolphin began eating on his own, and on day 7, although still very weak, he was capable of very ME'$ periods of unaided swimming. Within three more days the dolphin was swimming continuously on his own.
Pleural effusions in humans are reportedly often slow to resolve, and this was the case with this animal. A total of six chest taps were performed over the month of June, removing a total of 13 liters of fluid. Even though glucose and protein levels in addition to repeated bacterial, viral, and fungal cultures were performed on the chest fluid, the exact etiology of the pleural effusion could not be determined. The shark bite wounds, anemia, mild infection, liver, and gastrointestinal problems were being treated concomitantly.
By day 46 (approximately one month after the last chest tap) the amount of pleural fluid (<1 cm) was considered within normal limits. Repeat examinations revealed that the amount of fluid continued to gradually be re absorbed such that there was approximately 0.25 cm on day 104. Finally, after a total of 107 days, the dolphin was ready for release back to the wild having for three weeks: 1) been off all medication, shown good weight gain, and 3) demonstrated stable, acceptable blood values.
Performing a thoracentesis in a cetacean when guided by ultrasonography has been shown to be a safe, effective procedure. However, due to the nature of the condition, it may require several weeks of treatment to resolve.
Ultrasound is but one of the newer medical technologies available to large and small facilities working with marine mammals through outright purchase, loans or donations. This case was successfully treated utilizing a donated ultrasound console from Corometrics Medical Systems to first diagnose the condition, then to aid in chest drain placement, and thirdly to document progress on subsequent examinations. Our rehabilitation efforts dramatically benefited from having such capabilities.