Cynthia M. Otto

Use of thromboelastography in dogs with immune‐mediated hemolytic anemia: 39 cases (2000–2008)

OBJECTIVE To analyze thromboelastograms (TEGs) of naturally occurring cases of immune-mediated hemolytic anemia (IMHA) in order to identify whether a hypercoagulable state was present and whether its presence was associated with differences in survival. DESIGN Retrospective study spanning January 2000 to June 2008. Medical records of dogs were evaluated. Endpoints were considered death or discharge from the hospital. SETTING Academic teaching hospital. ANIMALS Thirty-nine dogs with a diagnosis of IMHA and at least one TEG performed during hospitalization were included. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS Four values were evaluated from the TEG: the R time (R), K time (K), alpha angle (alpha), and maximum amplitude. From these values, a coagulation index (CI) was calculated to classify patients as normocoagulable, hypercoagulable, or hypocoagulable. Thirty-three of 39 patients were hypercoagulable based on the CI. The 6 remaining dogs were normocoagulable. The patients with a normocoagulable CI had an increased mortality rate (100%) when compared with the hypercoagulable patients using Fishers exact test (P=0.02). Additionally, prolongation of partial thromboplastin time did not preclude hypercoagulable TEG values. CONCLUSIONS The majority of dogs with IMHA were hypercoagulable as measured by TEG. A normal CI was associated with a worse outcome in this patient population. TEG may provide additional and complementary information to prothrombin time and partial thromboplastin time relating to coagulation status in dogs with IMHA and may help predict prognosis and potentially guide clinical decisions to utilize anticoagulant drugs.

Severe blunt trauma in dogs: 235 cases (1997–2003)

Objective – To evaluate population characteristics, injuries, emergency diagnostic testing, and outcome of dogs with blunt trauma requiring intensive care in an urban hospital. Design – Retrospective study 1997–2003. Setting – All data obtained from the University of Pennsylvania – Matthew J. Ryan Veterinary Hospital. Animals – Dogs admitted to the intensive care unit for treatment following blunt trauma. Interventions – None. Measurements and Main results – Of the 235 dogs that met inclusion criteria, 206 (88%) survived and 29 (12%) did not survive. Blunt vehicular trauma accounted for 91.1% of cases. Mild hyperglycemia and hyperlactatemia was common in both survivors and nonsurvivors. The chest was the most common region traumatized and the prevalence of polytrauma was 72.3%. Initial weight, vital signs, PCV, total plasma protein, BUN, glucose, lactate, acid-base status, and electrolytes did not differ between survivors and nonsurvivors. Nonsurvivors were significantly more likely to have had head trauma (P=0.008), cranium fractures (P<0.001), recumbency at admission (P<0.001), development of hematochezia (P<0.001), clinical suspicion of acute respiratory distress syndrome (P<0.001), disseminated intravascular coagulation (P<0.001), multiorgan dysfunction syndrome (P<0.001), development of pneumonia (P<0.001), positive-pressure ventilation (P<0.001), vasopressor use (P<0.001), and cardiopulmonary arrest (P<0.001). Conclusions – Outcome of severe blunt trauma in dogs treated with intensive care is very good. Despite the high survival rate, several features associated with poor outcome were identified. Neither admission lactate nor glucose was able to predict outcome.OBJECTIVE To evaluate population characteristics, injuries, emergency diagnostic testing, and outcome of dogs with blunt trauma requiring intensive care in an urban hospital. DESIGN Retrospective study 1997-2003. SETTING All data obtained from the University of Pennsylvania - Matthew J. Ryan Veterinary Hospital. ANIMALS Dogs admitted to the intensive care unit for treatment following blunt trauma. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS Of the 235 dogs that met inclusion criteria, 206 (88%) survived and 29 (12%) did not survive. Blunt vehicular trauma accounted for 91.1% of cases. Mild hyperglycemia and hyperlactatemia was common in both survivors and nonsurvivors. The chest was the most common region traumatized and the prevalence of polytrauma was 72.3%. Initial weight, vital signs, PCV, total plasma protein, BUN, glucose, lactate, acid-base status, and electrolytes did not differ between survivors and nonsurvivors. Nonsurvivors were significantly more likely to have had head trauma (P=0.008), cranium fractures (P<0.001), recumbency at admission (P<0.001), development of hematochezia (P<0.001), clinical suspicion of acute respiratory distress syndrome (P<0.001), disseminated intravascular coagulation (P<0.001), multiorgan dysfunction syndrome (P<0.001), development of pneumonia (P<0.001), positive-pressure ventilation (P<0.001), vasopressor use (P<0.001), and cardiopulmonary arrest (P<0.001). CONCLUSIONS Outcome of severe blunt trauma in dogs treated with intensive care is very good. Despite the high survival rate, several features associated with poor outcome were identified. Neither admission lactate nor glucose was able to predict outcome.

Spatial and temporal heterogeneity of ventilator-associated lung injury after surfactant depletion

Volutrauma and atelectrauma have been proposed as mechanisms of ventilator-associated lung injury, but few studies have compared their relative importance in mediating lung injury. The objective of our study was to compare the injury produced by stretch (volutrauma) vs. cyclical recruitment (atelectrauma) after surfactant depletion. In saline-lavaged rabbits, we used high tidal volume, low respiratory rate, and low positive end-expiratory pressure to produce stretch injury in nondependent lung regions and cyclical recruitment in dependent lung regions. Tidal changes in shunt fraction were assessed by measuring arterial Po(2) oscillations. After ventilating for times ranging from 0 to 6 h, lungs were excised, sectioned gravitationally, and assessed for regional injury by evaluation of edema formation, chemokine expression, upregulation of inflammatory enzyme activity, and alveolar neutrophil accumulation. Edema formation, lung tissue interleukin-8 expression, and alveolar neutrophil accumulation progressed more rapidly in dependent lung regions, whereas macrophage chemotactic protein-1 expression progressed more rapidly in nondependent lung regions. Temporal and regional heterogeneity of lung injury were substantial. In this surfactant depletion model of acute lung injury, cyclical recruitment produced more injury than stretch.

Oxygen-dependent regulation of nitric oxide production by inducible nitric oxide synthase

Inducible nitric oxide synthase (iNOS) catalyzes the reaction that converts the substrates O(2) and l-arginine to the products nitric oxide (NO) and l-citrulline. Macrophages, and many other cell types, upregulate and express iNOS primarily in response to inflammatory stimuli. Physiological and pathophysiological oxygen tension can regulate NO production by iNOS at multiple levels, including transcriptional, translational, posttranslational, enzyme dimerization, cofactor availability, and substrate dependence. Cell culture techniques that emphasize control of cellular PO(2), and measurement of NO or its stable products, have been used by several investigators for in vitro study of the O(2) dependence of NO production at one or more of these levels. In most cell types, prior or concurrent exposure to cytokines or other inflammatory stimuli is required for the upregulation of iNOS mRNA and protein by hypoxia. Important transcription factors that target the iNOS promoter in hypoxia include hypoxia-inducible factor 1 and/or nuclear factor κB. In contrast to the upregulation of iNOS by hypoxia, in most cell types NO production is reduced by hypoxia. Recent work suggests a prominent role for O(2) substrate dependence in the short-term regulation of iNOS-mediated NO production.

Examination of hemostatic parameters to detect hypercoagulability in dogs with severe protein‐losing nephropathy

Objective – To identify hemostatic abnormalities in dogs with protein-losing nephropathies (PLN) that represent risk factors for pathologic thrombosis. Design – Cross-sectional observational study of client-owned dogs with PLN, nonprotein losing renal failure (RF), and systemic illness (SI) exclusive of primary renal disease. Setting – Urban University Referral Center. Animals – A total of 29 dogs (n=11 PLN, n=7 RF, n=11 SI) were enrolled between January 2001 and July 2002. Samples were also collected from 20 clinically normal dogs to serve as hemostasis assay controls. Interventions – None. Hemostasis Testing – Citrate anticoagulated blood was collected for point-of-care testing with a viscoelastic monitor (thromboelastograph [TEG]) and citrate plasma was prepared for coagulation screening tests and specific assay of the following hemostatic proteins: antiplasmin, antithrombin, D-dimer, Factor VIII, fibrinogen, plasminogen, protein C, and von Willebrand factor. Results – Dogs with PLN and RF demonstrated TEG abnormalities consistent with hypercoagulability (eg, short clotting time, high clot amplitude) and both groups had significantly lower antithrombin than the SI group. The PLN dogs had significantly higher protein C than either the RF or SI group. Hyperfibrinogenemia was a consistent finding among all 3 disease groups, and the coagulation index a measure of hypercoagulability derived from TEG parameters, directly correlated with fibrinogen values of all study dogs. Conclusions – Hemostatic abnormalities consistent with systemic hypercoagulability are common in dogs with RF and PLN, however, no prothrombotic factors unique to PLN were identified in our study. The thrombotic tendency of PLN may therefore involve parameters we did not directly assess such as platelet reactivity, fibrinolysis, perturbations in blood flow, and/or endothelial dysfunction. High protein C is a novel finding in PLN dogs of unknown clinical relevance.OBJECTIVE To identify hemostatic abnormalities in dogs with protein-losing nephropathies (PLN) that represent risk factors for pathologic thrombosis. DESIGN Cross-sectional observational study of client-owned dogs with PLN, nonprotein losing renal failure (RF), and systemic illness (SI) exclusive of primary renal disease. SETTING Urban University Referral Center. ANIMALS A total of 29 dogs (n=11 PLN, n=7 RF, n=11 SI) were enrolled between January 2001 and July 2002. Samples were also collected from 20 clinically normal dogs to serve as hemostasis assay controls. INTERVENTIONS None. HEMOSTASIS TESTING: Citrate anticoagulated blood was collected for point-of-care testing with a viscoelastic monitor (thromboelastograph [TEG]) and citrate plasma was prepared for coagulation screening tests and specific assay of the following hemostatic proteins: antiplasmin, antithrombin, D-dimer, Factor VIII, fibrinogen, plasminogen, protein C, and von Willebrand factor. RESULTS Dogs with PLN and RF demonstrated TEG abnormalities consistent with hypercoagulability (eg, short clotting time, high clot amplitude) and both groups had significantly lower antithrombin than the SI group. The PLN dogs had significantly higher protein C than either the RF or SI group. Hyperfibrinogenemia was a consistent finding among all 3 disease groups, and the coagulation index a measure of hypercoagulability derived from TEG parameters, directly correlated with fibrinogen values of all study dogs. CONCLUSIONS Hemostatic abnormalities consistent with systemic hypercoagulability are common in dogs with RF and PLN, however, no prothrombotic factors unique to PLN were identified in our study. The thrombotic tendency of PLN may therefore involve parameters we did not directly assess such as platelet reactivity, fibrinolysis, perturbations in blood flow, and/or endothelial dysfunction. High protein C is a novel finding in PLN dogs of unknown clinical relevance.

In vitro intermittent hypoxia: challenges for creating hypoxia in cell culture

Intermittent hypoxia has been implicated in morbidities associated with sleep apnea, and may be a novel cellular signal for inflammation [J. Appl. Physiol. 90 (2001) 1986]. Standard cell culture has two major limitations for studying the effects of steady-state P(O(2)) and intermittent hypoxia. First, convective mixing in the culture media can be variable, making precise control of cellular P(O(2)) difficult. Second, diffusion of oxygen through the culture media slows changes in cellular P(O(2)) after rapid changes in the gas phase P(O(2)). Our estimates of diffusional transients for standard cell culture suggest significant restrictions in the ability to cycle P(O(2)) at frequencies relevant to intermittent hypoxia. We present a novel system for forced convection cell culture with adherent cells inside capillary tubing. Steady state cellular P(O(2)) is regulated to an accuracy of approximately 1 Torr. The response time for cycling of P(O(2)) is less than 1.6 sec. This system is ideally suited for studies of intermittent hypoxia in adherent cells.

Physiological and hypoxic O2 tensions rapidly regulate NO production by stimulated macrophages

Nitric oxide (NO) production by inducible NO synthase (iNOS) is dependent on O(2) availability. The duration and degree of hypoxia that limit NO production are poorly defined in cultured cells. To investigate short-term O(2)-mediated regulation of NO production, we used a novel forced convection cell culture system to rapidly (response time of 1.6 s) and accurately (+/-1 Torr) deliver specific O(2) tensions (from <1 to 157 Torr) directly to a monolayer of LPS- and IFNgamma-stimulated RAW 264.7 cells while simultaneously measuring NO production via an electrochemical probe. Decreased O(2) availability rapidly (<or=30 s) and reversibly decreased NO production with an apparent K(m)O(2) of 22 (SD 6) Torr (31 microM) and a V(max) of 4.9 (SD 0.4) nmol min(-1) 10(-6) cells. To explore potential mechanisms of decreased NO production during hypoxia, we investigated O(2)-dependent changes in iNOS protein concentration, iNOS dimerization, and cellular NO consumption. iNOS protein concentration was not affected (P = 0.895). iNOS dimerization appeared to be biphasic [6 Torr (P = 0.008) and 157 Torr (P = 0.258) >36 Torr], but it did not predict NO production. NO consumption was minimal at high O(2) and NO tensions and negligible at low O(2) and NO tensions. These results are consistent with O(2) substrate limitation as a regulatory mechanism during brief hypoxic exposure. The rapid and reversible effects of physiological and pathophysiological O(2) tensions suggest that O(2) tension has the potential to regulate NO production in vivo.

The Implications of Arterial Po2 Oscillations for Conventional Arterial Blood Gas Analysis

In a surfactant-depletion model of lung injury, tidal recruitment of atelectasis and changes in shunt fraction lead to large Pao2 oscillations. We investigated the effect of these oscillations on conventional arterial blood gas (ABG) results using different sampling techniques in ventilated rabbits. In each rabbit, 5 different ventilator settings were studied, 2 before saline lavage injury and 3 after lavage injury. Ventilator settings were altered according to 5 different goals for the amplitude and mean value of brachiocephalic Pao2 oscillations, as guided by a fast responding intraarterial probe. ABG collection was timed to obtain the sample at the peak or trough of the Pao2 oscillations, or over several respiratory cycles. Before lung injury, oscillations were small and sample timing did not influence Pao2. After saline lavage, when Po2 fluctuations measured by the indwelling arterial Po2 probe confirmed tidal recruitment, Pao2 by ABG was significantly higher at peak (295 ± 130 mm Hg) compared with trough (74 ± 15 mm Hg) or mean (125 ± 75 mm Hg). In early, mild lung injury after saline lavage, Pao2 can vary markedly during the respiratory cycle. When atelectasis is recruited with each breath, interpretation of changes in shunt fraction, based on conventional ABG analysis, should account for potentially large respiratory variations in arterial Po2.

Tumor necrosis factor production in cats in response to lipopolysaccharide: an in vivo and in vitro study

Supernatants from feline peritoneal exudate cells (PECs) exposed to lipopolysaccharde (LPS) produced significantly (P < 0.05) more tumor necrosis factor (TNF) activity than supernatants from cells exposed to media. An in vitro LPS response was obtained following incubation of whole blood with 10 micrograms ml-1 LPS for 2 h. Intravenous infusion of LPS (750 micrograms kg-1 rapidly increased plasma TNF activity to a maximum at 60 min after initiation of LPS infusion. By 180 min, TNF activity returned to baseline. Cats produce TNF in response to LPS in a manner similar to other species. Measurement of TNF activity in plasma or in LPS-stimulated whole blood are methods to further characterize the inflammatory response in feline diseases.

Small animal cardiopulmonary resuscitation requires a continuum of care: proposal for a chain of survival for veterinary patients

JAVMA, Vol 240, No. 5, March 1, 2012 C efforts have been made to advance methods of CPR since its introduction 50 years ago. As the understanding of CPR has evolved, so has the definition of its major components that contribute to survival. Twenty years ago, the AHA introduced the so-called chain of survival, which serves as a metaphor for the importance of approaching CPA in a timely, sequential, and comprehensive manner. As originally described, the components, or links, in this chain of survival included early access to help, early initiation of CPR, early defibrillation, and early advanced cardiac life support. A number of recent developments in CPR research have encouraged the focused optimization of individual links in the chain of survival, with the goal of optimizing the overall CPR process. The AHA published new guidelines for CPR in humans in October 2010. These guidelines, which are revised every 5 years, are based on an evidence evaluation process that serves as the foundation for consensus treatment recommendations. In essence, the AHA aims to identify elements that could further optimize each link of the chain of survival. The first major opportunity for improvement lies in the fact that laypersons and health professionals often do not perform CPR according to published guidelines and that this noncompliance is associated with reduced survival. Focused efforts are being made to allocate resources that will improve compliance with these guidelines through novel educational and technical tools, and the AHA 2010 CPR guidelines include a new section dedicated to education and implementation.Additionally, recent studies have found clear evidence of the neuroprotective effects of mild therapeutic hypothermia for human patients after CPA, even if administered hours after ROSC. This and the fact that 60% to 70% of humans that have CPA and achieve ROSC subsequently die of post–cardiac arrest syndrome led to the inclusion of a dedicated section on post–cardiac arrest care in the newest AHA CPR Small animal cardiopulmonary resuscitation requires a continuum of care: proposal for a chain of survival for veterinary patients