Black Hawk (9-17-07)
AAEP ROUNDS CASE 9.17.07
by Anna (Thompson) Kelley and Andrea Nieman
On Sept. 14th, a 17 year American Quarter Horse presented to the Large Animal Teaching Hospital for a foul odor and mucopurulent nasal discharge coming from his left side. Approximately a week ago, Black Hawk had his first maxillary molars extracted bilaterally because the tooth roots were loose in the dental exam. They thought this might be the cause of his chronic epistaxis. The holes were then packed with methylmethacrylate to keep any contaminants from making their way into the maxillary sinus. This loosening of the teeth is commonly seen in older horses. When he was younger, the first molars took up more space in the maxillary sinus. Now as he has aged, the residual root hasdecreased and the cavity has enlarged.
His owners stated he was refusing hay and grain so he was slightly anorexic. His physical exam revealed him to be slightly depressed, but his temperature, pulse, and respiration were within normal limits and his weight was 499 kg (1100 lbs). There were no other significant findings besides the odor and discharge. A CBC (Complete Blood Count) and Chemistry Profile were performed. Black Hawk showed mild anemia, possibly due to chronic epistaxis or inflammation, neutrophilia, and his fibrinogen was increased (700 mg/dl). No bands were present and globulins were increased. These results are all compatible with an inflammatory process occurring in Black Hawk.
A possible sinus infection was suspected so radiographs of the skull were taken revealing a fluid line in the left rostral and caudal maxillary sinus compartments. Endoscopy of the nasal passages and upper pharynx confirmed the discharge coming from the sinus and showed no other significant findings. The oral exam of the previously extracted molars showed the packing was still in place. A Trephination procedure was performed on the left frontal sinus of Black Hawk and a Foley catheter was inserted to incorporate a lavage system. To trephine is to drill a hole into a paranasal cavity. It is commonly done to extract teeth. In this case, 5 L of Normasol solution was flushed into the frontal sinus which will then flow through the frontomaxillary opening (this allows communication between the frontal and maxillary sinuses) and into the caudal maxillary sinus. This is also a natural nasal drainage route for the horse. The Normasol flush started out at 5 L daily and was tapered to 2.5 L daily over several days. Black Hawk was immediately put on a common upper respiratory antibiotic, TMS (Trimethoprim-sulfonamide), at 13 tablets PO BID.
Over the next several days, an intermittent cough was noticed, but still no abnormal lung sounds were heard when Black Hawk was rebreathed. He did begin to eat a little. Because of his age, he was walked throughout the day to reduce stiffness from any arthritis. On Sept. 19th, more mucus was flushed from the sinus and since the discharge was continuing, a Transtracheal Wash was performed. This recovered large amounts of mucopurulent material from the lower airways. An anaerobic and aerobic culture and cytology were submitted. In order for a specific organism to be diagnosed as the pathogen, it has to be very high in numbers, phagocytized by phagocytic cells of the immune response, and show presence of degenerative neutrophils. An ultrasound was also performed on Black Hawk’s thoracic region. This diagnostic test revealed comet tail artifacts which are due to fluid replacing air (probably mucus in this case) and small circular lesions that appear to be abscesses. Lung radiographs showed small circular intercavitary nodules with gaseous, necrotic centers. The multiple cavitating pulmonary abscesses suggest this horse has a chronic pulmonary infection in his lower airways, likely bacterial pneumonia.
At this point, Black Hawk's treatments have changed. He was placed on Metronidazole (10, 000 mg) PO QID until the culture and sensitivity returns. On Sept. 20th, the TMS was discontinued, the Foley catheter was removed, and an intravenous (IV) catheter was placed. He was then administered KPen (Potassium Penicillin G) 22mL IV QID, Enrofloxacin 38 mL IV QID, and Banamine(Flunixin meglumine) 5 mL IV BID. Metronidazole, Kpen, and Enrofloxacin are all common antimicrobials used in horses to treat respiratory disease. Once the cultures are received, the specific antimicrobial can be selected to fight off the appropriate bacteria present. Banamine is commonly given with gram negative infections and potential endotoxemia to block arachidonic acid metabolism because it's known as an NSAID (Non Steroidal Anti- Inflammatory Drug) therefore it inhibits inflammatory mediators. By reducing the inflammation in the respiratory system, they hope to increase ease of breathing and comfort of the horse.
POSSIBLE QUESTIONS YOU COULD ASK AT THE NEXT AAEP ROUND CONCERNING THIS HORSE:
1. Is the pneumonia related to the cause of the sinusitis or visa versa?
2. Could the pneumonia be the previous cause for the chronic epistaxis mentioned before?
3. Could molar extraction somehow lead to pneumonia?
4. Have the cultures and cytology from the TTW and sinus shown any significant findings?
Abbreviations:
QID: ONCE A DAY
BID: TWICE A DAY
TTW: Transtracheal wash
PO: Administrated drugs ORAL ROUTE
IV: Administrated drugs INTRAVENOUS ROUTE
Bacteria that may eventually cause pleuropneumonia that are commonly found in the oropharyngeal cavities of the horse:
Streptococcus, Pasteurella, Actinobacillus, Escherichia coli, Enterobacter, Bacteroides, Peptostreptococcus, Fusobacterium, Clostridium.
References:
Case Information taken from Dr. Caldwell 9/17/07 AAEP ROUNDS
and from Case Binder Records
Equine Internal Medicine, by Saunders, Reed, Bayly, Sellon, 2nd Ed. 2004.
