NON-CARDIAC THORACIC ULTRASOUND IN 75 FELINE AND CANINE PATIENTS

The purpose of this study was to describe the ultrasonographic appearance of non-cardiac diseases of the small animal thorax. Ultrasound images from a total of 75 animals (26 cats and 49 dogs) were compared to cytologic, histopathologic, and necropsy findings. Clinical diagnoses included neoplasia of the mediastinum, pleura, or lungs (43); idiopathic mediastinal cyst (3); diaphragmatic or peritoneopericardial hernia (4); lung lobe torsion (1); pulmonary eosinophilic infiltrates (1); and idiopathic, chylous, congestive heart failure, or lymphangiectasia associated pleural effusion (14). In the remaining 9 patients, a definitive diagnosis was not obtained. Ultrasound-guided fine needle aspirate was performed in 56 patients; 1 of these also had an ultrasound-guided tissue core biopsy. Of the fine needle aspirates, 51 (91%) were diagnostic. Ultrasound examination, particularly when accompanied by guided tissue sampling, can be a valuable tool in the diagnosis of non-cardiac intrathoracic lesions.     

Diagnosis of Congenital Cardiac Right-to-left Shunts with 99mTc-macroaggregated Albumin

Diagnosing right-to-left congenital cardiac shunts can be difficult. Cardiac catheterization and angiocardiography represent the traditional gold standard for diagnosis, but they are invasive. Nuclear scintigraphy using 99mTc-macroaggregated albumin (MAA) has been employed in humans as an alternate method of diagnosis. This study reviews eight dogs presented for evaluation of a suspect right-to-left cardiac shunt that were examined using 99mTc-MAA. In all, 2-4 mCi (74-148 MBq) of reduced particle 99mTc-MAA were injected IV in a cephalic vein and static images of the whole body, including right and left lateral, dorsal, and ventral views, were acquired for 60 s and stored into a 256 x 256 x 16 matrix. Shunt fractions were calculated. One dog with radiopharmaceutical distribution limited to the lungs did not have a shunt. Seven dogs had distribution of the radiopharmaceutical outside the pulmonary capillary bed, indicating bypassing of the pulmonary capillary circulation due to a right-to-left shunt. Four dogs had 99mTc-MAA within the brain. Three dogs that did not have brain uptake, but instead had a sharp cutoff of radioactivity at the level of the front limbs and neck, were diagnosed with reverse patent ductus arteriosus (PDA). The asymmetric distribution of the radiopharmaceutical is due to the location of the shunt, distal to the brachiocephalic trunk and left subclavian artery. Shunt fractions of dogs with extrapulmonary radioactivity ranged from 40% to 59%. Nuclear scintigraphy with 99mTc-MAA is a quick alternative method of diagnosing right-to-left cardiac shunts that permits quantification of shunt fraction. Distinguishing between reverse PDA and other right-to-left shunts may be possible based on the radiopharmaceutical distribution.     

A Comparison of Acute Pull-Out Strength Between Two-Way and One-Way Transfixation Pin Insertion for External Skeletal Fixation in Canine Bone

This study tested the hypothesis that two-way insertion of an external skeletal fixator trans-fixation pin would weaken the pin-bone interface. Smooth and partially threaded (end) trans-fixation pins were placed in tibiae of 32 cadavers by slow speed drilling or hand placement through a predrilled pilot hole. In one bone of each tibial pair, pins were inserted 2 cm beyond the distal cortex and retracted to a predetermined position (two-way). In the contralateral limb, the pins were inserted in one forward motion to the predetermined position (one-way). The peak force (Newtons) required to extract the pins (pull-out strength) axially at a rate of 1 mm/sec was determined by using a universal testing machine. A significant (p < .05) decrease in pull-out strength was found in pins placed by two-way insertion (674 +/- 410) as opposed to one-way insertion (766 +/- 432). The results of this in vitro study suggest that one-way insertion should be used clinically to decrease weakening of the pin-bone interface and prevent possible failure of external fixators. A significantly greater pull-out strength was found for threaded pins placed in the proximal diaphysis (1459 +/- 330 Newtons) compared to the distal metaphysis (873 +/- 297 Newtons).     

Parenteral Anticholinergics in Dogs With Normal and Elevated Intraocular Pressure

Dogs given parenteral anticholinergic drugs have been thought to be at risk for development or exacerbation of elevated intraocular pressure (IOP). In a randomized, blinded, placebo-controlled study, we evaluated the effect of intramuscular glycopyrrolate (0.01 mg/kg) on pupil diameter and IOP in unanesthetized normal dogs. Treatment with glycopyrrolate did not change pupil diameter or IOP from baseline, nor were there differences between glycopyrrolate and saline-treated (control) dogs. In addition, the authors retrospectively reviewed the medical records of 2,828 dogs undergoing general anesthesia between April 1987 and September 1990 to determine if there was an association between parenteral anticholinergic medication and postanesthetic elevation in IOP. The authors also determined the frequency of bradycardia requiring anticholinergic therapy during anesthesia in dogs with glaucoma. Of the 2,828 cases reviewed, the records of 46 dogs coded for glaucoma were examined in detail. The 46 dogs underwent 62 episodes of anesthesia, with 23 episodes including exposure to an anticholinergic drug. An increase in IOP from preanesthetic to postanesthetic measurement occurred in three dogs. One of these dogs received anticholinergic medication for bradycardia during anesthesia. The postanesthetic elevation in IOP in this dog was probably not drug related. Preanesthetic anticholinergic administration did not affect the incidence of anticholinergic administration for bradycardia during the anesthetic episode. Anticholinergic therapy during anesthesia was more frequent when the preanesthetic medication included an opiate drug. These studies do not indicate an association between parenteral anticholinergic administration and elevations in IOP.     

Application of Airway Pressure Therapy in Veterinary Critical Care: Part II: Airway Pressure Therapy

As the specialties of emergency medicine and critical care have grown and evolved in both human and veterinary medicine, so has the need for more advanced care of patients with primary lung disease. Treatment of acute respiratory failure has been the focus of several articles in the human medical literature of the past few years.^1,8 This paper deals with airway pressure therapy and its application in cases of acute respiratory failure in veterinary medicine. The reader is referred to part I of this paper for a reveiw of respiratory mechanics and hypoxemia as they apply to respiratory therapy.