Matthew S. Mellema

Thoracic radiography, bronchoalveolar lavage cytopathology, and pulmonary parenchymal histopathology: A comparison of diagnostic results in 11 cats

The purpose of this study was to compare the diagnostic results and value of thoracic radiography, bronchoalveolar lavage (BAL) fluid cytopathology, and lung histopathology in 11 cats with spontaneous respiratory disease in which radiography and cytopathology were inadequate in establishing a definitive diagnosis. In these cats, radiographic patterns were characterized as bronchial (n=6), interstitial (n=3), and alveolar (n=2); other features included hyperinflation (n=3), bronchiectasis (n=2), pleural fissure lines (n=2), pulmonary nodules (n=2), atelectasis (n=1), and a tracheal mass (n=1). Bronchoalveolar lavage fluid was unremarkable in two cats. Abnormal BAL fluid showed inflammation (n=5), hemorrhage (n=2), epithelial hyperplasia (n=1), or was suspicious for neoplasia (n=1). Histopathological evaluation revealed inflammation (n=8), neoplasia (n=2), and vascular congestion (n=1). The predominant radiographic location of disease correlated with the same histopathological location in seven cats, and the cytopathological class of BAL fluid was consistent with the histopathological class of disease in seven cats. There was poor correlation between the types of cells found in the BAL fluid and the pathologists prediction of the types of cells likely to be found in the BAL fluid based on the amount and type of airway cellularity seen on histopathological examination. The results of this study suggest that in some cats, BAL fluid cytopathology does not always correlate with the type of pulmonary disease identified on histopathology. In respiratory diseases where radiography and cytopathology fail to provide a definitive diagnosis, histopathological examination of the lung may be necessary.

Airway microbial culture and susceptibility patterns in dogs and cats with respiratory disease of varying severity

OBJECTIVE To compare airway microbiological culture and susceptibility results in 2 groups of dogs and cats: 1 with respiratory failure requiring positive pressure ventilation (PPV) and 1 with respiratory disease. DESIGN Retrospective study. SETTING University teaching hospital. ANIMALS Fifty-two dogs and cats requiring PPV that had an airway microbiologic culture submitted from October 1, 2003 to October 31, 2008 were included. One hundred and four airway microbiologic cultures from dogs and cats with respiratory disease not requiring PPV were randomly sampled for comparison. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS Patients with respiratory failure were more likely to have a gram-negative enteric isolate identified (P<0.001), while patients with respiratory disease were more likely to have a gram-negative nonenteric isolate (P<0.001) or anaerobic isolate (P<0.001) identified. Aerobic bacterial isolates from patients with respiratory failure were less likely to be susceptible to ampicillin (P=0.006), amoxicillin/clavulonate (P<0.001), chloramphenicol (P=0.004), enrofloxacin (P<0.001), ticarcillin/clavulonate (P=0.004), and the combination of ampicillin with enrofloxacin (P<0.001) than were aerobic bacterial isolates from patients with respiratory disease. CONCLUSIONS Canine and feline patients with respiratory failure severe enough to require PPV exhibit a different pattern of bacterial isolates cultured from their airways when compared with isolates from patients with respiratory disease that has not resulted in ventilator dependence. These isolates are more likely to be resistant to commonly used antimicrobials/antimicrobial combinations than patients in the respiratory disease group. These findings suggest that in canine and feline patients with infectious lower respiratory tract disease, consideration of the severity of the pulmonary insult may allow for better prediction of likely isolates and their antimicrobial susceptibilities. Further prospective studies with a standardized collection technique are warranted.

Comparison of regular insulin infusion doses in critically ill diabetic cats: 29 cases (1999-2007).

OBJECTIVE To compare biochemical parameters, neurologic changes, length of hospital stay, and clinical improvement in 3 groups of cats with diabetic ketosis/diabetic ketoacidosis (DK/DKA) prescribed varied doses of regular insulin as a continuous rate of infusion (CRI). DESIGN Retrospective study. SETTING University teaching hospital. ANIMALS Twenty-nine client-owned cats with DK/DKA prescribed a regular insulin CRI. INTERVENTIONS Cats were grouped as follows: 7 cats each in Group 1 and 2, (prescribed 1.1 and 2.2 U/kg/d, respectively), and 15 cats in Group 3 (prescribed increasing doses as needed). MEASUREMENTS AND MAIN RESULTS None of the groups received the total prescribed dose of insulin. The mean actual dose administered/kg/d ranged from 0.30 (0.21) to 0.87 (0.32) U/kg/d in Groups 1, 2, and 3. There was no difference in mean minimum blood glucose (BG) per 4 hours or change in BG from baseline per 4 hours between Groups 1 and 2 (P=0.63, 0.50). There was no difference between groups regarding the time required to reach a BG ≤ 13.9 mmol/L (250 mg/dL), serum phosphorus or potassium concentrations relative to baseline values (P=0.53, 0.90), length of time until urine or serum ketones were no longer detected (P=0.73), the animal commenced eating (P=0.24), or length of hospital stay (P=0.63). Four of the cats had declining mentation during hospitalization; there were no relationships between osmolality at presentation, either prescribed or administered insulin dose, and mentation changes. Three of the 4 cats with declining mentation survived. Twenty-seven of the 29 cats (93%) survived to discharge. CONCLUSIONS In this study, prescribing the published canine dose (2.2 U/kg/d) of regular insulin to cats with DK/DKA does not appear to increase the frequency of adverse neurologic or biochemical sequelae compared with cats that are prescribed the published cat dose (1.1 U/kg/d). The use of a sliding scale for determination of infusion rates significantly reduces the amount of insulin cats receive in this setting. Determination of whether adverse sequelae would occur more frequently if cats with DK/DKA received the full insulin prescribed doses of 1.1, 2.2, or >2.2 U/kg/d is warranted. Further controlled studies are necessary to determine if higher doses of insulin are associated with beneficial effects on morbidity or mortality.

Evaluation of acid–base disorders in dogs and cats presenting to an emergency room. Part 1: Comparison of three methods of acid–base analysis

OBJECTIVE To compare the diagnostic performance of the traditional approach to acid-base analysis with the Stewart approach and a semiquantitative approach. DESIGN Prospective cohort study. SETTING University teaching hospital. ANIMALS A total number of 84 dogs and 14 cats presenting to a university teaching hospital emergency room. PROCEDURES All dogs and cats in which venous blood samples for acid-base, lactate, and serum biochemical analysis were all collected within 60 minutes of each other, over a 5-month enrollment period. Acid-base analysis was performed using the traditional approach, Stewart approach, and a semiquantitative approach. RESULTS Traditional acid-base analysis identified respiratory acid-base abnormalities in 14/98 animals and metabolic acid-base abnormalities in 67/98. A mixed disorder of metabolic acidosis and respiratory alkalosis was most common occurring in 29/98 patients. The Stewart approach identified metabolic abnormalities in 82/98 patients; strong ion difference abnormalities were evident in 68/98 cases; an increased strong ion gap acidosis was identified in 49/98 cases; and changes in the quantity of weak acids in 25/98 cases. The semiquantitative approach identified abnormalities in all cases evaluated. Of the 14 patients with a primary respiratory acid-base abnormality, the Stewart approach identified metabolic abnormalities in 9 and the semiquantitative approach found abnormalities in all animals. CONCLUSIONS AND CLINICAL RELEVANCE The physicochemical approaches diagnosed more acid-base abnormalities in this population than the traditional approach although many of the abnormalities identified were small and of unknown clinical relevance. The physicochemical approaches may provide greater insight as to the underlying etiology of abnormalities, which maybe of particular relevance to cases with changes in albumin and/or phosphorus concentration.

Comparative accuracy of several published formulae for the estimation of serum osmolality in cats

OBJECTIVE To determine the osmole gap utilizing 18 previously published formulae for the estimation of serum osmolality in cats. PROCEDURES Serum samples were frozen at -80°C after routine biochemical analysis. An Advanced Micro Osmometer 3300 was used to measure serum osmolality. Eighteen previously reported formulae were used to calculate osmolality from biochemical analysis results. The calculated osmolality was subtracted from the measured osmolality to determine the osmole gap. Osmole gaps for azotaemic and hyperglycaemic cats were compared to those from cats without azotaemia or hyperglycaemia using each formula. RESULTS The osmole gaps varied dependent on the formula used and the presence or absence of hyperglycaemia or azotaemia. Eleven formulae led to calculated osmolality and osmole gaps that were not statistically different when hyperglycaemia, azotaemia or both were present. Four of these 11 formulae resulted in osmole gaps near zero. For each formula used, the osmole gap increased with increasing osmolality. CLINICAL SIGNIFICANCE Multiple formulae to calculate serum osmolality can be used, but they result in significantly different osmole gaps. Clinicians should be aware of the specific reference interval for the formula being used. The formula [2(Na(+) ) + glucose + BUN] is recommended as it is easy to use and reliable even in the presence of hyperglycaemia and/or azotaemia.

A comparison of the clinical utility of several published formulae for estimated osmolality of canine serum

OBJECTIVE To determine the normal osmole gap for 18 previously published formulae used to estimate serum osmolality in dogs. DESIGN Prospective study. SETTING University veterinary medical teaching hospital. ANIMALS Two hundred and fifty client-owned dogs. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS Serum samples were saved and frozen at -80°C after routine biochemical analysis as ordered by attending clinicians. An Advanced Micro Osmometer 3300 was used to measure serum osmolality. Eighteen distinct formulae previously reported in the medical literature were used to calculate the osmolality from the biochemical analysis results. The calculated osmolality was then subtracted from the measured osmolality to determine the osmole gap. Osmole gaps for azotemic and hyperglycemic dogs were compared to those of dogs without azotemia or hyperglycemia using each formula. The median measured osmolality for all dogs in the study was 302 mOsm/kg (interquartile range 297-307). The osmole gaps varied widely depending on the formula used to calculate osmolality and the presence or absence of hyperglycemia or azotemia. Eleven formulae led to calculated osmolality and osmole gaps that were not statistically different when hyperglycemia or azotemia was present. Four out of these 11 formulae resulted in osmole gaps near zero. CONCLUSIONS AND CLINICAL RELEVANCE Multiple formulae reported to calculate serum osmolality can be used in the clinical setting, but they result in significantly different normal osmole gaps. Clinicians should be aware of the specific reference interval for the formula being used. The authors recommend the formula 2(Na(+) ) + [glucose/18] + [BUN/2.8] because it is easy to use and is reliable even when hyperglycemia or azotemia are present.

Evaluation of acid-base disorders in dogs and cats presenting to an emergency room. Part 2: Comparison of anion gap, strong ion gap, and semiquantitative analysis

OBJECTIVE To compare the diagnostic performance of the anion gap (AG) with 2 physicochemical approaches to identify unmeasured anions. DESIGN Prospective cohort study. SETTING University teaching hospital. ANIMALS Eighty-four dogs and 14 cats presenting to a university teaching hospital emergency room. INTERVENTIONS All dogs and cats in which venous blood samples for acid-base, lactate, and serum biochemical analysis were all collected within 60 minutes of each other, over a 5-month enrollment period. Unmeasured anions were quantified using each of three approaches: the anion gap (AG), strong ion gap (SIG), and a semiquantitative approach (XA). MEASUREMENTS AND MAIN RESULTS An increased AG metabolic acidosis was evident in 34/98 of cases. The Stewart approach identified an increased SIG acidosis in 49/98 of cases. There was a strong correlation between SIG and AG (r = 0.89; P < 0.001). The semiquantitative approach identified increased unmeasured anions in 68/98 of cases. There was a moderate correlation between AG and XA (r = 0.68; P < 0.001) and a slightly stronger correlation between SIG and XA (r = 0.75; P < 0.001). Plasma lactate concentrations and AG were poorly correlated (r = 0.22; P = 0.029) and there was no correlation between lactate concentrations and BE (r = 0.19; P = 0.069). CONCLUSIONS Unmeasured anions occurred commonly in this sample of small animal emergency room patients and physiochemical approaches identified more animals with unmeasured anions than the traditional AG calculation. Further studies are needed to determine if the results of the physicochemical approach improves clinical management and warrants the associated increases in cost and complexity.

In vitro evaluation of the efficacy of a veterinary dry heat fluid warmer

OBJECTIVES To evaluate the efficacy of a veterinary dry heat fluid warmer on ambient and prewarmed crystalloid fluids and refrigerated packed red blood cells (pRBC). DESIGN Prospective in vitro study. SETTING University teaching hospital. ANIMALS None. INTERVENTIONS Ambient and prewarmed crystalloid fluids and refrigerated pRBC were delivered via a standard fluid administration set at various rates. A thermistor continuously monitored fluid outflow temperature with and without a dry heat veterinary fluid warmer (study device). RESULTS The outflow temperature was significantly higher with the study device as compared to control conditions for all fluids and rates tested. The maximum outflow temperature of approximately 35°C (95°F) occurred when the study device was applied to either ambient or prewarmed crystalloid fluids at 50 mL/h. In the study device trials, the outflow temperature of ambient crystalloid fluids ranged from 35.1° to 27.3°C (95.2° to 81.1°F) as the fluid rate increased from 50 to 999 mL/h. Control trials of prewarmed crystalloids produced outflow temperatures that rapidly approached ambient temperature. Addition of the study device to prewarmed crystalloids resulted in outflow temperatures that were similar to that of the corresponding ambient crystalloid trials. Control trials of refrigerated pRBC achieved ambient temperature at rates from 10 to 500 mL/h. With the study device, pRBC were maximally warmed to an outflow temperature of 35.8°C (96.4°F) at 100 mL/h. CONCLUSION Although the study device generated statistically significant increases in outflow temperature of crystalloid fluids and pRBC, the ability of the device to decrease the metabolic cost of fluid administration is limited to specific clinical scenarios. The use of prewarmed crystalloid fluids with or without the study device offers minimal benefit over ambient temperature crystalloids. Substantial warming of pRBC occurs during administration, even without use of the study device.

The effect of hetastarch 670/0.75 administered in vivo as a constant rate infusion on platelet closure time in the dog.

OBJECTIVE To evaluate the effects of hetastarch 670/0.75 on canine platelet function and clinical bleeding following its administration as a constant rate infusion (CRI) at 1 mL/kg/h and 2 mL/kg/h for 24 hours. DESIGN In vivo, prospective, open-label, crossover study. SETTING Research laboratory at a university veterinary facility. ANIMALS Eight healthy, adult male research dogs. INTERVENTIONS Each dog received 1 mL/kg/h hetastarch for 24 hours then 2 mL/kg/h with a washout period of 10 weeks between each experiment. Platelet closure time (CT) was measured using a platelet function analyzer with collagen adenosine diphosphate (ADP) cartridges. CT measurements were performed at baseline and 6, 12, and 24 hours following initiation of hetastarch infusion. MEASUREMENTS AND MAIN RESULTS At 1 mL/kg/h, mean CT was significantly increased at the 12- and 24-hour time point relative to the baseline value, although mean CT never rose to a value above the reference interval during the 24-hour infusion. At 2 mL/kg/h, median CT was also significantly increased at the 12- and 24-hour time point relative to the baseline value. Administration of 2 mL/kg/h did progressively prolong the median CT value though only exceeded the reference interval at the 24-hour time point. Despite the prolongation of median CT, there was no clinical evidence of spontaneous bleeding in any dog during the 24-hour infusion at either CRI rate. CONCLUSIONS Hetastarch 670/0.75 when used as a 24-hour CRI at 1 and 2 mL/kg/h prolongs CT in healthy dogs at 6, 12, and 24 hours. Median CT only exceeded the reference interval at 24 hours at 2 mL/kg/h.

Pro-coagulant thromboelastographic features in the bulldog.

OBJECTIVES To determine if bulldogs develop a hypercoagulable state comparable to that observed in human patients with sleep apnoea hypopnoea syndrome. MATERIALS AND METHODS Thromboelastography was performed in 15 clinically healthy bulldogs and 24 healthy control dogs of other breeds or mixed breed lineage. RESULTS Bulldogs had significantly shorter R and K times relative to control dogs. The alpha angle, maximum amplitude and overall clot strength was significantly greater in bulldogs than in controls. The largest differences between the groups were found in the maximal amplitude and overall clot strength parameters. CLINICAL SIGNIFICANCE These findings support the concept that brachycephalic syndrome promotes a hypercoagulable phenotype similar to that observed with sleep apnoea hypopnoea syndrome in humans. The large increases in maximal amplitude observed suggest platelet hyperreactivity may play an important role.