Factors Independently Related to Survival at 28 Days in Cats After Emergency Admission--Rico Multicentrc Study
R.C. Rabelo; C. Fragío; S.C. Alsua; M.A. Dazza; N. Paixão; E. Pacheco; M.C.C.D. Lima; V.M. Ribeiro; M.M. Pimenta
Compared to diagnostic medicine, the prognostic and survival studies are still seen as art better than a science. The fact that human patients and moreover pet owners have the right to participate in all medical decisions that will affect themselves, obligate the medical team to know how to generate and provide prognostic information. This work was designed to determine which clinical or laboratorial parameters are related to survival in cats, 28 days after an emergency approach.
Material and Methods
This is a multicentric, prospective and cohort study, that analyzed multiple feline parameters registered during the emergency approach. A total population of 101 cats were consecutively attended in five veterinary hospitals in Spain, Portugal and Brazil, between September, 2005 and January, 2007. All patients were referred as true emergencies and needed hospitalization (Rabelo 2005). The study was based in analyzing complete medical history, physiologic and laboratorial parameters at the emergency room, identifying which of them were independently related to survival at 28 days. All data was checked immediately after patient arriving (T0) and 24 hours after this first moment (T24), and were all condensed in individual files and analyzed by statistical software SPSS 14.0 (SPSS 2001). Parametric data were analyzed by Levene's and Student's T Test and non parametric by Pearson's chi-square and McNemar Bowker's Test. In all cases, we consider that all results are significant if p < 0.05.
The following parameters were significantly independently associated with survival 28 days after the emergency approach (variables labeled 24h were determined 24h after admission): Total Protein (p = 0.043); Creatinine (p = 0.014); BUN (p = 0.004); PvO2 (p = 0.02); Respiratory Rate 24h (p = 0.012); Creatinine 24h (p = 0.032); BUN 24h (p = 0.009); Potassium 24h (p = 0.018) and Total Number of Diseases (p = 0.023). Survival at 28 days was also significantly related with gender (p = 0.032) and the presence of renal failure (p = 0.027).
Discussion and Conclusions
Besides all the parameters cited in the "results" section (significantly related--p < 0.05, as independent factors), it's important to discuss the tendency of other parameters clinically related to survival too. Animals older than 74,8 months had a clear tendency towards less survival compared with animals younger than 55,8 months, which may be relevant from a clinical perspective. The influence of age on survival rates is understandable, since older animals suffer more frequently of chronic diseases which may worsen outcome. Gender is also an important factor related to survival al 28 days: males have a higher survival index than females (76.4% versus 55.3%), with an equivalent ratio of male to female in the overall population included in the study. This may indicate that females are more sensitive than males to diseases inducing emergency admission in cats. We do not have any clear explanation for this finding; in humans results are controversial, with some studies showing higher mortality in females and others in males (Herrera-Gutiérrez et al. 2006, Sales et al. 2005, Villacorta et al. 1998, Villacorta et al. 1999). Probability of survival at 28 days is higher in animals admitted because of trauma than in admissions due to organic diseases. Patients suffering trauma are probably younger and healthy animals, whereas those admitted because of organic disease may be older and suffering of chronic diseases (RF and neoplasia for example), which is associated with a negative outcome. This has also been described in human patients (Marchio et al. 2006, Martinez et al. 2004). A previous diagnosis of renal failure (RF) is individually associated with survival at 28 days (p = 0.032), with almost a 25% difference in survival between patients presenting RF and patients without RF. The only physical parameter significantly related to survival at 28 days, was respiratory rate (RR) 24h after admission (p = 0.012); however, the difference between RR means in survivors (36 rpm) and non-survivors (28 rpm) is low, which may indicate that this finding may not be clinically significant. Although not statistically related with survival, our results show that heart rates in T0 were always higher than traditional reference values for healthy cats; this tachycardia probably reflects a stress situation in a cardiovascular stable patient. Results were not statistically significant, but we have found a clear tendency towards higher mortality in patients with the lower heart and respiratory rates. Concerning blood pressure, the mean value in survivors was 125 mmHg vs. 112 mmHg in non-survivors; mean value for systolic blood pressure was 144 mmHg vs. 126 mmHg and for diastolic pressure, 112 mmHg vs. 102 mmHg. These results are similar to those obtained by other authors (Simpson et al, 2007), who concluded that systolic blood pressure = 124 mmHg was predictive of survival in cats admitted to ICU's. The fact that survivors present higher blood pressure values (although not statistically significant in our study) indicates that cats with a poor sympathetic response have a negative outcome (Backman et al. 1999, Ohshita et al. 2004, Peterson et al. 1971, Ribeiro et al. 2000, Tilley & Owens, 1987). However, a high vagal tone may also have a protective effect on the myocardium during reperfusion injury in cats (Recordati et al. 1971, Zuanetti et al. 1987). Concerning laboratory data, the strongest relation with survival at 28 days was found with urea in T0, total proteins in T0, creatinine in T0 and T24 and potassium in T24. Survivors showed mean total protein values of 6,8 g/dl; while non-survivors showed means higher than 8 g/dl, well over the normal range. This finding is not explained by hemoconcentration (dehydration), because hematocrit values do not follow the same tendency; thus, the explanation is probably that non-survivors suffer from some kind of inflammatory disease. Lactate values higher than 4,5 mmol/L in T0 or higher than 3 mmoL/L in T24 are associated to less survival at 28 days, which is similar to results published by others (Sarmento et al. 2006, Silva et al. 2001). This shows that low perfusion sates that are not stabilized quickly, have a bad outcome. The presence of comorbidities is also an important factor for survival at 28 days: patients with more than two diseases have a lower survival rate, which is coincident with human studies (Cullen et al. 1974, Hoffman et al. 1992, Iezzoni et al. 2000, Löwel et al. 2002). On the other hand, the type of therapy given upon admission (medical vs. surgical) as well the organic system affected, were not related with survival at 28 days. Overall, survival rates after 24 hours were quite high (almost 100%), but the number of survivors decreased significantly at 7 and 28 days. This is probably related with the high incidence of genito-urinary diseases as the cause of the emergency admission in our population (32% and 33% respectively); these kind of patients are usually easy to stabilize in the first hours (urethral obstruction, azotemic patients, etc.) but can have serious complications later due to renal involvement, which has been also described in humans (Herrera-Gutiérrez et al. 2006). Patients with mixed disturbances (affecting more than one organic system) showed the lowest survival rates, followed by patients suffering from genito-urinary and gastroenteric diseases. We concluded that several physical and laboratorial findings are statistically related with survival at 28 days after the initial emergency approach in feline patients, and could thus potentially be considered as prognostic factors for predicting survival probability in emergency patients.
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