[Verse 1]
The cardiac cycle opens like a door —
diastole fills the chamber, preload builds the store,
end-diastolic volume stretches every fiber wide,
Frank-Starling says the harder that you stretch, the stronger is the stride.
Isovolumetric contraction, pressure climbing steep,
aortic valve cracks open when the ventricle won't sleep,
ejection, then relaxation, pressures fall again —
trace the pressure-volume loop and watch it close and then begin.
[Chorus]
Preload, afterload, contractility —
the three levers of cardiac ability.
Stroke volume times the rate gives output clean,
SVR times CO equals pressure in between.
Baroreceptors in the carotid sinus sing,
Bainbridge fires when the venous pressures ring —
autonomic arms race, vagal versus SNS,
anesthetics blunt it all — expect hemodynamic stress.
[Verse 2]
Coronary flow occurs mostly in diastole,
when diastole gets shortened, the myocardium pays the toll.
Oxygen supply is flow times oxygen content,
demand is wall stress, rate, and contractile extent.
The subendocardium sits most vulnerable there,
perfusion pressure — diastolic minus LVEDP — beware.
ST depression creeping on your monitor screen —
intraoperative ischemia, the silent guillotine.
[Chorus]
Preload, afterload, contractility —
the three levers of cardiac ability.
Stroke volume times the rate gives output clean,
SVR times CO equals pressure in between.
Baroreceptors in the carotid sinus sing,
Bainbridge fires when the venous pressures ring —
autonomic arms race, vagal versus SNS,
anesthetics blunt it all — expect hemodynamic stress.
[Bridge]
Positive pressure ventilation — venous return collapses,
the right ventricle struggles when the pulmonary vascular bed expands and lapses.
Hypoxic vasoconstriction guards the pulmonary gate,
RV is thin-walled, hates resistance, preload-sensitive fate.
Cerebral flow tracks CO₂ with exquisite fidelity,
the kidney guards its GFR through autoregulatory agility —
that word, agility, means self-correcting grace,
hepatic and splanchnic flows surrender last when shunting takes their place.
Uteroplacental — no autoregulation there,
maternal pressure drops, the fetal circuit lays bare.
[Verse 3]
Shock is the organ-level debt you cannot quickly pay —
distributive, cardiogenic, obstructive, hypovolemic array.
Distributive drops the SVR while output climbs up warm,
cardiogenic chokes the CO, pressors weather every norm.
Obstructive — tamponade, pneumothorax, embolus impedes —
fix the cause before the vasopressor briefly supersedes.
The ECG reads rhythm, axis, intervals, and ischemia's art —
Q-waves mark the necrosis written deep in scarred myocardial chart.