Urinary nitric oxide in healthy and septic newborn foals: preliminary results

Purpose of the work. In human medicine the nitric oxide (NO) has been extensively investigated since it is involved in several pathophysiological processes. The NO homeostasis is crucial for optimal health maintenance and disease prevention and shows positive or negative effects in relation to its concentration (Aranke et al, 2011). Increased NO urinary levels could be detected during several pathological conditions above all infections and systemic inflammatory response syndrome (SIRS), and in human babies the evaluation of this parameter in urines has been deeply investigated (Uzuner et al 1997; Ergenekon et al, 2000). Urine sampling, in fact, is widely used in human medicine for newborns and represents a valid alternative to blood samples since it is non-invasive, cheap and repeatable. In addition, collection of spot urine samples, standardized for urinary creatinine excretion (NO to creatinine ratio, NO/Cr), can be used rather then 24-hours collection (Tsukahara et al, 2007). To the authors’ knowledge, no studies have been performed on foals urinary NO. The aims of this study were to evaluate urinary NO and NO/Cr levels in healthy and septic newborn foals to investigate the possible use of this parameter as diagnostic/prognostic marker. Materials and used methods. The study was conduced during the 2013 breeding season. Twentythree newborn foals were enrolled: 10 healthy and 13 septic. All healthy foals should be born at term, by spontaneous delivery, with an APGAR score =8 within 10 minutes of birth and should be mature and viable. Septic foals were hospitalized within 3 days of age; at admission, after the clinical exam, blood samples were collected for hematological, biochemical analysis and blood culture. Foals were classified as septic if they fulfilled any or all of the following criteria: positive blood culture and a sepsis score =11. Urinary samples were collected from each of the healthy foals by spontaneous micturition at day 1, 2, 3 and 4 of age. Samples were centrifuged at 2000 rpm for 5 minutes and the supernatant frozen until analysis. Septic foals urinary samples were collected by spontaneous micturition or catheterization at hospitalization (T0) and 24 hours later (T1). Samples were processed as above. NO was determined by Griess Enzymatic colorimetric method, while creatinine by Jaffè kinetic modified method. One-way ANOVA test was performed to evaluate NO and NO/Cr profiles within healthy and septic groups and between the two groups. The comparison between sick surviving and non-surviving foals has been performed by t-test at T0 and T1. Outcomes. All healthy foals fulfilled the criteria of inclusion and no diseases were detected in any of these foals. Septic foals were admitted at a mean age of 34.2±23.6 hours. Sepsis was the only disease in 7/13 foals, while in 6/13 it represented the main disease. Among sick foals, 6/13 died. NO did not show significant differences within either healthy or sick group in relation to the age. These results are in agreement with data reported in human neonates in which no differences where found during the first week of life in healthy and septic babies (Uzuner et al, 1997). When healthy and sick foals were compared, NO showed significantly (p<0.01) higher values in septic foals at 2 days of age (4.20±2.58 mg/dL vs 2.21±1.33 mg/dL). This result is partially in disagreement with data reported by Dizick et al (2002) who found lower levels in infants affected by septic shock; Uzuner et al (1997) instead, found higher levels in infants affected by SIRS during the first 24 hours from symptoms appearance. Neither in healthy nor in sick foals statistical differences for NO/Cr were found in relation to age. This seems to be in disagreement with data reported for human newborns in which higher levels are detected in neonates compared to older children (Eli et al, 2005). When healthy and sick foals were compared, sick foals showed significantly higher NO/Cr values at day 1 (0.36±0.31 mg/dL vs 0.06±0.05 mg/dL) and 2 (0.26±0.18 mg/dL vs 0.13±0.12 mg/dL) of age. This result is in agreement with data reported for infants (Uzuner et al, 1997; Ergenekon et al, 2000). No differences for NO/Cr values in sick foals were found between surviving and non-surviving animals at admission and 24 hours later. Conclusions. Even if this is a preliminary study, NO/Cr seems to be a possible diagnostic marker of sepsis in newborn foals during the first 48 hours of age.