Does intraoperative low arterial partial pressure of oxygen increase the risk of surgical site infection following emergency exploratory laparotomy in horses? Cristina Costa-Farré a,⇑ , Marta Prades a , Thaïs Ribera a , Oliver Valero b , Pilar Taurà c a Departament de Medicina i Cirurgia Animal, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain b Servei d’estadística aplicada, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain c Departament d’Anestesiologia, Hospital Clínic de Barcelona, Universitat de Barcelona, 08036 Barcelona, Spain article info Article history: Accepted 31 January 2014 Keywords: Surgical site infection Hypoxaemia Anaesthesia Horses abstract Decreased tissue oxygenation is a critical factor in the development of wound infection as neutrophil mediated oxidative killing is an essential mechanism against surgical pathogens. The objective of this prospective case series was to assess the impact of intraoperative arterial partial pressure of oxygen (PaO 2 ) on surgical site infection (SSI) in horses undergoing emergency exploratory laparotomy for acute gastrointestinal disease. The anaesthetic and antibiotic protocol was standardised. Demographic data, surgical potential risk factors and PaO 2 , obtained 1 h after induction of anaesthesia were recorded. Sur- gical wounds were assessed daily for infection during hospitalisation and follow up information was obtained after discharge. A total of 84 adult horses were included. SSI developed in 34 (40.4%) horses. Multivariate logistic regression showed that PaO 2 , anaesthetic time and subcutaneous suture material were predictors of SSI (AUC = 0.76, sensitivity = 71%, specificity = 65%). The use of polyglycolic acid sutures increased the risk and horses with a PaO 2 value <80 mmHg [10.6 kPa] and anaesthetic time >2 h had the highest risk of developing SSI (OR = 9.01; 95% CI 2.28–35.64). The results of this study confirm the hypothesis that low intraoperative PaO 2 contributes to the development of SSI following colic surgery. Ó 2014 Elsevier Ltd. All rights reserved. Introduction Decreased tissue oxygenation is a critical factor in the develop- ment of wound infection due to the fact that neutrophil mediated oxidative killing is an essential mechanism against surgical patho- gens (Allen et al., 1997). Human patients who develop decreased tissue oxygenation in the perioperative period are at risk of wound infection (Moller et al., 2002; Kabon et al., 2005; Koutsoumbelis et al., 2011) and several clinical investigations support the use of high perioperative inspiratory oxygen concentrations to reduce the risk of surgical site infection (SSI) in people (Belda et al., 2005; Barili, 2007; Maragakis, 2009). Arterial hypoxaemia commonly develops in horses in dorsal recumbency anaesthetised for exploratory laparotomy despite delivery of 100% oxygen and use of mechanical ventilation (Day et al., 1995; Whitehair and Willits, 1999). Impaired pulmonary gas exchange mainly results from ventilation–perfusion mismatch and intrapulmonary shunting due to atelectasis in dependent lung lobes (Nyman and Hedenstierna, 1989; Nyman et al., 1990). Although some studies mention the potential influence of intraop- erative and anaesthetic recovery complications on the risk of developing SSI in horses (Baxter, 1992; Wilson et al., 1995), few reports have included these risk factors within their data analysis (Gibson et al., 1989; Torfs et al., 2010). SSI is a serious complication after colic surgery, occurring with a frequency of around 25%, and has been reported in several prospective studies (Honnas and Cohen, 1997; Smith et al., 2007; Bischofberger et al., 2010). SSI prolongs hospitalisation and predis- poses to hernia formation (Gibson et al., 1989; French et al., 2002) and so identifying new risk factors and interventions to decrease the infection rate may contribute to reduce recovery periods and medical costs. The main objective of this prospective study was to test the hypothesis that low PaO 2 during the intraoperative period increases the incidence of SSI after exploratory laparotomy in horses. http://dx.doi.org/10.1016/j.tvjl.2014.01.029 1090-0233/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +34 93 5811387. E-mail address: cristina.costa@uab.cat (C. Costa-Farré). The Veterinary Journal 200 (2014) 175–180 Contents lists available at ScienceDirect The Veterinary Journal journal homepage: www.elsevier.com/locate/tvjl