Blood pressure control with phenylephrine or dobutamine: a randomized controlled trial comparing effects on cerebral and paravertebral tissue oxygen saturation measured with near-infrared spectroscopy

Preserving haemodynamics is expected to positively affect tissue oxygen saturation. We hypothesized that maintaining mean arterial blood pressure (MAP) (using phenylephrine (PE) or dobutamine (Dobu)) would equally affect regional cerebral and paravertebral tissue saturation (rS_cO₂ and rS_pvO₂, respectively). Thirty-four patients were randomly assigned to receive either PE or Dobu, in order to keep MAP within 20% of the preoperative value. Their effect on haemodynamics, rS_cO₂ and rS_pvO₂ at thoracic level T₃-T₄, T₉-T₁₀ and lumbar level L₁-L₂ was calculated at different doses. Drug-induced haemodynamic effects differed between groups (∆MAP: -2%±21 and - 19%±17, ∆CI: -14.6%±14.6 and 24.1%±49.9, ∆HR: -21%±21 and 0%±16 for PE and Dobu, respectively). Both groups exhibited a significant decrease in rS_cO₂, with a more pronounced decline in the PE group (-14.1%±16.1) compared to the Dobu group (-5.9%±10.6). There were no significant changes at the paravertebral level in either group, but a slight but statistically significant difference was detected between the two groups at T₃-T₄ and L₁-L₂. Current guidelines advocate maintaining adequate systemic blood pressures to prevent spinal cord ischaemia in specific procedures. However, it is still unknown which circulatory supportive drug is more beneficial for maintaining spinal cord perfusion. Our data indicates that, when used for maintenance of blood pressure within a 20% range of preoperative values, neither phenylephrine nor dobutamine affect paravertebral tissue saturation.