Bladder tissue oxygen tension monitoring in pigs subjected to a range of cardiorespiratory and pharmacological challenges

A fall in tissue oxygen tension (tPO(2)) is an early indicator of organ hypoxia in both patients and animal models. We previously demonstrated the utility of bladder tPO(2) in various rodent shock models. As a prelude to clinical testing, we aimed to provide further validation of bladder tPO(2) monitoring in a large animal model undergoing a range of cardiorespiratory insults and vasoactive drug interventions. Anaesthetized, mechanically ventilated, instrumented female pigs (n = 8) were subjected to a range of short-term cardiorespiratory (changes in inspired oxygen concentration (FiO(2)), haemorrhage, positive end-expiratory pressure) and pharmacologic (inotrope, pressor) challenges. Global haemodynamics, arterial and pulmonary blood gases and bladder tPO(2) were measured before and after each challenge. Bladder tPO(2) values fell in line with increasing degrees of hypoxaemia and haemorrhage, and were restored during resuscitation. These changes often preceded those seen in global haemodynamics, arterial base excess and lactate. The rise in bladder tPO(2) with hyperoxia, performed as an oxygen challenge test, was incrementally blunted by progressive haemorrhage. Dobutamine and norepinephrine both increased cardiac output and global O-2 delivery, but had no effect on bladder tPO(2) or lactataemia in these healthy pigs. In this pig model bladder tPO(2) provides a sensitive indicator of organ hypoxia compared to traditional biochemical markers during various cardiorespiratory challenges. This technique offers a potentially useful tool for clinical monitoring.