Acute respiratory distress syndrome in dogs and cats: a review of clinical findings and pathophysiology

Objective: To review the clinical and pathophysiologic aspects of acute respiratory distress syndrome (ARDS) in dogs and cats. Data sources: Data from human and veterinary literature were reviewed through Medline and CAB as well as manual search of references listed in articles pertaining to acute lung injury (ALI)/ARDS. Human data synthesis: Since the term ARDS was first coined in 1967, there has been a abundance of literature pertaining to this devastating syndrome in human medicine. More complete understanding of the complex interactions between inflammatory cells, soluble mediators (e.g., tumor necrosis factor, interleukin (IL)‐6, IL‐8, platelet activating factor) and the clinical patient has provided for timely recognition and mechanistically based protective strategies decreasing morbidity and mortality in human patients with ARDS. Veterinary data synthesis: Although little is known, ARDS is becoming a more commonly recognized sequela in small animals. Initial case reports and retrospective studies have provided basic clinical characterization of ARDS in dogs and cats. Additionally, information from experimental models has expanded our understanding of the inflammatory mechanisms involved. It appears that the inflammatory processes and pathologic changes associated with ARDS are similar in dogs, cats, and humans. Conclusions: Unfortunately, current mortality rates for ARDS in small animals are close to 100%. As our capability to treat patients with advanced life‐threatening disease increases, it is vital that we develop a familiarity with the pathogenesis of ARDS. Understanding the complex inflammatory interactions is essential for determining effective preventative and management strategies as well as designing novel therapies for veterinary patients.     

Neonatal respiratory distress and sepsis in the premature foal: Challenges with diagnosis and management

The presentation of a premature, neonatal foal affected with respiratory distress and seizures represents a difficult diagnostic and therapeutic challenge often best addressed by the provision of appropriate emergency care followed by prompt referral to a well‐equipped critical care facility. Veterinary management of the premature foal described in the accompanying report was complicated by the development of sepsis and pulmonary failure. The development of pulmonary emphysematous bullae was identified during the course of the foal's treatment and probably contributed to its clinical deterioration. Diagnostic imaging modalities that may be used for the diagnosis of respiratory distress in neonatal foals include thoracic radiography, ultrasonography, computed tomography (CT) and magnetic resonance imaging (MRI). Both CT and MRI require general anaesthesia. The likelihood of a successful outcome for the foal in this report might have been improved by the provision of urgent veterinary care and referral to the critical care facility earlier in the course of its management. Important early indicators of the need for urgent veterinary care in this case included the foal's prematurity, inability to stand, and the need to provide manual support to facilitate nursing from the mare's udder. Foals affected in this manner should warrant treatment with broad‐spectrum antimicrobials, circulating volume maintenance, immunoglobulin support, and the use of a nasogastric tube to facilitate nutritional support.     

Equine laryngeal dysplasia as a cause of acute respiratory distress in a neonatal foal

Equine laryngeal dysplasia (ELD) is a congenital disorder caused by hypoplasia or aplasia of the structures derived from the fourth and possibly sixth branchial arches. The severity of the clinical signs varies widely, and depends on which structures are involved and the extent of the defect. In most cases, affected horses present with abnormal respiratory noise during exercise and poor performance. Manifestation of the disease in foals is very rare. This case report describes an unusual presentation of ELD in a neonatal foal. The foal presented with severe respiratory distress and weakness. Equine laryngeal dysplasia was suspected on endoscopy and later confirmed on post mortem examination of the larynx. To the best of our knowledge, this is the first report describing ELD as a cause of respiratory distress in a neonatal foal.     

Retrospective Study: Cause and clinical characteristics of rib fractures in cats: 33 cases (2000–2009)

Objective – To characterize the clinical features and population differences among cats sustaining traumatic and nontraumatic rib fractures. Design – Retrospective clinical study. Setting – University small animal hospital. Animals – Thirty‐three cats with radiographic evidence of rib fractures. Interventions – None. Measurements and Main Results – Cats with rib fractures were identified by performing a computer search of the radiology database. Thirty‐three cats that sustained rib fractures were identified between January 2000 and September 2009. Seventeen cats had fractures due to trauma and 16 were deemed to occur from nontraumatic causes. A Mann‐Whitney rank‐sum test revealed statistically significant differences in the median ages between the 2 groups. Older cats were more likely to sustain rib fractures as a result of a presumed nontraumatic causes. A Chi‐square analysis showed that nontraumatic fractures occurred significantly more often in the midbody region and involved the 9th–13th ribs. The majority of cats with presumed nontraumatic rib fracture had respiratory disease; the remaining cats had chronic renal disease or neoplasia. Cats with traumatic rib fractures had external signs of trauma. Conclusion – Rib fractures in cats may be clearly associated with trauma, or may be an incidental finding in cats with comorbidities. Cats with diseases that cause prolonged respiratory effort or coughing, metabolic diseases, or certain neoplasms, are at increased risk of spontaneous nontraumatic rib fractures.     

A retrospective study of the clinical presentation of 140 dogs and 39 cats with bacteraemia

OBJECTIVES: To evaluate retrospective data from 140 dogs and 39 cats with positive blood cultures that were presented to the Clinic for Small Animal Medicine in Munich from 1995 to 2004. METHODS: The identity of bacteria isolated from blood cultures of dogs and cats with bacteraemia was determined, and clinical and laboratory findings and outcome of animals with Gram-negative versus Gram-positive bacteraemia were compared. RESULTS: Sepsis was diagnosed in 81.7 per cent of dogs and 59.5 per cent of cats with bacteraemia. Escherichia coli was isolated in one third of the animals. Dogs with bacteraemia more often showed monocytosis and increased alkaline phosphatase activity, while in cats, hyperglycaemia was found more commonly. Dogs with Gram-negative bacteraemia had hypoalbuminaemia significantly more often than dogs with Gram-positive bacteraemia, while among the remaining parameters, there were no statistically significant differences. CLINICAL SIGNIFICANCE: Not all dogs and cats with a positive blood culture met the criteria for sepsis. Bacteraemia caused by Gram-positive versus Gram-negative bacteria cannot be distinguished based on clinical or laboratory parameters, and bacterial culture and susceptibility testing have to be performed for the right choice of antibiotic treatment.     

Assessment of the diagnostic accuracy of circulating cardiac troponin I concentration to distinguish between cats with cardiac and non-cardiac causes of respiratory distress

Objective

To determine if serum cardiac troponin I (cTnI) concentrations can distinguish cardiac from non-cardiac causes of respiratory distress (RD) in cats.

Animals, materials and methods

53 cats. cTnI concentrations were measured in 30 cats with non-cardiac respiratory distress (RD-NC) and compared to 23 cats with RD due to congestive heart failure (RD + CHF).

Results

The RD + CHF group had higher median cTnI concentration (0.94 ng/ml interquartile range IQR 0.54-4.00, range <0.20 - 90.14) than the RD-NC group (<0.2 ng/ml IQR < 0.2-0.33, range <0.20-41.1, p < 0.001). The area under the curve (AUC) was 0.842 (95% CI 0.728-0.955) for the receiver operator curve (ROC) analysis of the accuracy of cTnI concentrations to discriminate RD + CHF from RD-NC cats. A cut-off of ≥ 0.81 ng/ml discriminated RD + CHF from RD-NC cats with a sensitivity and specificity of 65.2% and 90.0% respectively. However considerable overlap in cTnI concentrations between the 2 groups was identified.

Conclusions

Serum cTnI concentrations were different in RD + CHF compared to RD-NC cats. However the overlap in cTnI concentrations between the 2 groups reduced the clinical efficacy of the assay which therefore should not be used as a stand-alone test but in combination with other diagnostics such as echocardiography and radiography.     

Historical and physical parameters as predictors of severe hyperkalemia in male cats with urethral obstruction

Objective: To evaluate selected historical and physical parameters as predictors of hyperkalemia in male cats with urethral obstruction. Design: Retrospective study. Setting: Veterinary teaching hospital. Animals: Two hundred and twenty‐three male cats. Interventions: None. Measurements and main results: The metabolic derangements of 223 male cats that presented with urethral obstruction from 1997 through 1999 were reported in a companion article. Approximately 12% of the cats had multiple, life‐threatening metabolic derangements. In the present study, historical and physical parameters were evaluated as predictors of hyperkalemia (K⁺≥8.0 mmol/L) in cats with urethral obstruction. The 4 historical parameters significantly associated with hyperkalemia were: first time obstruction, outdoor status, anorexia, or vomiting. The 5 physical parameters significantly associated with hyperkalemia were: rectal temperature, heart rate, respiratory rate, pulse quality, and the presence of arrhythmia. Of the physical parameters, a rectal temperature below 95–96.6°F (35–35.9°C) or a heart rate below 120 b.p.m. were the most accurate predictors. When used in combination (i.e., evidence of bradycardia and hypothermia), the specificity for hyperkalemia was 98–100%. Conclusions: Rectal temperature and heart rate were the best parameters for predicting hyperkalemia in this population.     

A clinical evaluation of the 'mini parallel Lack' breathing system in cats and comparison with a modified Ayre's T-piece

OBJECTIVE: To evaluate the suitability of a 'mini parallel Lack' (MPL) breathing system for use in spontaneously breathing cats and to compare the fresh gas flow requirement with that of a modified Ayre's T-piece (MATP). ANIMALS: Twenty client-owned cats, ASA I and II, presented for elective procedures requiring anaesthesia. MATERIALS AND METHODS: Pre-anaesthetic medication and induction of anaesthesia were carried out using several techniques commonly used in our teaching hospital. Anaesthesia was maintained with halothane or isoflurane vaporized in either oxygen or with a mixture of oxygen and nitrous oxide. Both breathing systems were evaluated in each cat, with the order of use randomized. Initial fresh gas flows were 300 mL kg(-1) minute(-1) for the MPL and 500 mL kg(- 1) minute(-1) for the MATP. After a 20-minute stabilization period, fresh gas flow was reduced by 200 mL minute(-1) every 5 minutes until re-breathing--defined as an increase in the inspired partial pressure of carbon dioxide to 0.3 kPa (2 mm Hg)--was detected. The fresh gas flow was then increased in 100 mL minute(-1) increments until re-breathing was no longer detectable, and this value was recorded as the minimum fresh gas flow requirement for the breathing system in use. The procedure was then repeated for the second breathing system. Minimum fresh gas flow requirements were compared using a paired Students t-test. Cardiopulmonary variables were compared using anova. Valve opening pressure was measured in the MPL using a manometer. RESULTS: The mean (+/-SD) fresh gas flow that prevented re-breathing with the MPL (510 +/- 170 mL minute(-1); equivalent to 142 +/- 47 mL kg(-1) minute(-1)) was significantly lower than that required for the MATP (1430 +/- 560 mL minute(-1); equivalent to 397 +/-155 mL kg(-1) minute(-1)). There were no significant differences in cardiopulmonary variables attributable to the use of the two breathing systems. The MPL valve opening pressure was 1.1 cm H2O. CONCLUSIONS: The MPL breathing system used lower gas flows than the MATP without affecting cardiovascular or respiratory function. Clinical relevance In spontaneously breathing cats, the MPL offers the advantages of a reduction in cost and atmospheric pollution because less volatile agent is vaporized.     

Allogenic blood patch pleurodesis for management of pneumothorax in a Cavalier King Charles Spaniel puppy with multiple pulmonary blebs and bullae

A 9‐week‐old male intact Cavalier King Charles Spaniel was presented for evaluation of acute onset dyspnea caused by left‐sided pneumothorax. Thoracic computed tomography (CT) identified multiple pulmonary bullae and blebs in multiple lung lobes. Rupture of ≥1 pulmonary blebs or bullae, precipitated by low impact trauma, was the suspected cause of pneumothorax. A volume of 7.5 mL/kg of fresh whole blood was collected from a type‐matched donor dog and administered into the left pleural space using a thoracostomy tube. The pneumothorax was successfully resolved and no adverse effects of blood patch pleurodesis were noted. The dog was clinically normal 12 months later.     

Evaluation of postoperative respiratory function by serial blood gas analysis in dogs treated with transdermal fentanyl

Objective: To perform blood gas analysis of the respiratory response to transdermal fentanyl in dogs which have experienced an open‐chest surgical procedure. Design: Prospective trial. Setting: Veterinary Teaching Hospital Surgical Research and Student Laboratory. Intervention: Dogs were purchased for a surgical laboratory. Students performed a cranial abdominal exploratory and diaphragmatic hernia repair. Sixteen dogs were divided into 2 groups. Dogs received transdermal fentanyl (group F), using an average dose of 4.8 µg/kg/hr, applied to the caudal‐lateral abdomen 22 hours before surgery, or intravenous buprenorphine (group B; 0.02 mg/kg) given 1 hour prior to anesthetic induction and every 6 hours postoperatively. All dogs received intravenous acepromazine (0.05 mg/kg) preoperatively and every 6 hours postoperatively. Dogs were instrumented with carotid artery catheters. Measurements and main results: Arterial blood gas values were analyzed every 2 hours postoperatively. Plasma fentanyl levels were analyzed every 4 hours postoperatively. The mean carbon dioxide tension (PCO₂) did not exceed 45 mmHg in either group. The range in mean PCO₂ levels was 32.9 (± 3.4)?38.1 (± 3.9) in group B and 34.7 (± 3.25)?43.6 (± 5.5) in group F. At 2 time points, the mean PCO₂ was significantly lower in group B compared with normal levels in group F. Hypoxemia occurred in both the groups. The range in mean oxygen tension (PO₂) was 76.5 (± 18.3)?91.1 (± 16.3) in group B and 76.0 (± 10.8)?96.6 (± 7.6) in group F. There was no significant difference in PO₂ between groups. Levels of fentanyl considered to be analgesic were maintained for the postoperative period. Conclusions: The use of a relatively high dose of transdermal fentanyl did not induce postoperative hypoventilation as evidenced by serial arterial blood gas analysis in this model.     

Evaluation of renal biopsies in cats and dogs — histopathology in comparison with clinical data

Histopathological findings of renal biopsies in cats and dogs with diffuse nephropathies generally lead to an exact diagnosis and facilitate prognostic judgements. Complications following renal biopsy are usually slight, provided the biopsy is performed properly. Routine renal laboratory data have been compared with histopathological findings. High urine protein values are often the result of glomerular lesions, whereas high creatinine values are frequently related to tubulointerstitial lesions. In general, there is no relationship between different types of nephropathy and age; nevertheless animals with chronic tubulointerstitial nephritis were, on average, older than animals with glomerulopathies.     

Evaluation of porfimer sodium in dogs and cats with spontaneous tumors

The effect of photodynamic therapy is a function of several variables, including selective retention of the drug in tumor tissue with reduced drug concentration in surrounding normal tissue. A study was designed to determine the pharmacokinetic profile and variability of porfimer sodium in dogs and cats with spontaneous tumors and to thereby determine the optimal timing of its photoactivation in these species. The results of this study indicate that there is marked variability among species in the distribution of porfimer sodium between highly proliferating tissues, which requires careful attention in the design of human and veterinary application of photodynamic therapy with porfimer sodium, as determined in rodent models.     

Serum concentrations of cardiac troponin I and cardiac troponin T in dogs with class IV congestive heart failure due to mitral valve disease

Objective: The objective of this study was to evaluate the incidence of circulating detectable serum levels of cardiac troponin I (CTnI) and circulating detectable serum levels of cardiac troponin T (CTnT) in dogs with class IV congestive heart failure (CHF) due to mitral valve disease (MVD) at admission. An additional study aim was to determine if detectable troponin levels correlated with the magnitude of several clinical parameters. Design: Prospective clinical investigation. Setting: Small animal emergency and critical care referral hospital. Interventions: Blood was collected before emergency treatment from 15 dogs presenting in class IV CHF due to MVD. Measurements: Serum concentrations of CTnI, CTnT at presentation. Main results: Six dogs (40%) had a detectable CTnI (median 0.24, range 0.12–0.31 ng/mL), and the remainder were less than 0.1 ng/mL and deemed non‐detectable. The one dog (7%) that had a detectable CTnT (0.02 ng/mL) also had a detectable CTnI (0.23 ng/mL). There was no statistical difference in survival to discharge between dogs with non‐detectable troponin levels and those with detectable troponin levels; however, dogs with detectable troponin levels had shorter overall survival times. Dogs with a detectable level of CTnI had a median survival of 67.5 days (range 1–390 days), and dogs with a non‐detectable level of CTnI had a median survival time of 390 days (range 20–912 days) (P=0.02). Conclusion: This study suggests that CTnI can be detected at admission in the blood of 40% of dogs with class IV CHF due to MVD. Dogs with non‐detectable levels of cardiac troponins had a significantly longer overall survival time. The encouraging results of this small pilot study warrant further investigation.