https://www.pulmccm.org/p/icu-physiology-in-1000-words-phenylephrine-pushes-stroke-volume?s=09

Effects of Phenylephrine on Hemodynamics and Cardiac Function: A Review of Studies

• Phenylephrine and its Hemodynamic Effects:
  • Phenylephrine, an alpha1 agonist, has complex and noteworthy hemodynamic effects.
  • It can increase afterload and decrease stroke volume (SV) in some cases.
  • SV reduction may be due to increased afterload or decreased preload.
• The Influence of Preload Reserve:
  • Studies have shown that SV response to phenylephrine depends on preload reserve.
  • In a preload-dependent state, phenylephrine boluses increase SV by recruiting venous blood.
  • In a preload-independent state, phenylephrine boluses decrease SV, possibly due to afterload impairment.
• Debunking the Pulmonary Vasoconstriction Hypothesis:
  • Reduced SV in a preload-independent state is not solely due to pulmonary vasoconstriction.
  • Observations show that SV reduction is consistent with increased afterload rather than decreased preload.
• Human Studies and SV Response:
  • Human studies have also demonstrated the influence of preload dependency on SV response.
  • Preload-independent patients show decreased SV, while preload-dependent patients show increased SV.
  • Baseline preload dependency and functional state of the heart play a role in SV response to phenylephrine.
• Conclusion:
  • The effect of phenylephrine bolus on SV depends on the functional state of the heart.
  • In preload-independent patients, SV tends to decrease due to afterload augmentation.
  • In preload-dependent patients, venous blood recruitment by phenylephrine can increase SV.
• Central hemodynamic effects of phenylephrine:
  • A study in Anesthesia & Analgesia showed the assessment of central hemodynamic effects of phenylephrine in animals.
  • The study found that phenylephrine had central hemodynamic effects.
• Effect of phenylephrine on cerebral oxygenation:
  • A study in the British Journal of Anaesthesia examined the effect of phenylephrine bolus treatment on cerebral oxygenation in anaesthetized patients.
  • The study concluded that phenylephrine had an effect on cerebral oxygenation.
• Phenylephrine's effect on cardiac output:
  • Studies have shown that the effects of phenylephrine on cardiac output depend on the position of the heart on the Frank-Starling relationship.
  • Another study found that phenylephrine bolus administration affected global left ventricular function in patients with coronary artery disease and valvular aortic stenosis.
  • Phenylephrine bolus administration also had an effect on left ventricular function during isoflurane-induced hypotension.