Characteristics of ventricular function in severe hemorrhagic shock

Area of Science:

• Cardiovascular Physiology
• Hemorrhagic Shock Research
• Cardiac Mechanics

Background:

• Left ventricular (LV) function is altered in severe hemorrhagic shock (HS), but the underlying mechanisms remain unclear.
• Distinguishing between systolic and diastolic dysfunction is crucial for understanding HS-induced cardiac alterations.
• Emax, a rate and load-independent index of contractility, offers a novel method to assess systolic performance.

Purpose of the Study:

• To investigate the mechanisms of left ventricular (LV) dysfunction following severe hemorrhagic shock (HS).
• To differentiate between systolic and diastolic functional changes using Emax and LV diastolic pressure-strain relationship.
• To assess the impact of HS and reinfusion on cardiac contractility and compliance.

Main Methods:

• Measurements of Emax and LV diastolic pressure-strain relationship in 15 instrumented dogs.
• Induction of HS (mean aortic pressure 40 mm Hg) for 2 hours, followed by reinfusion.
• Utilized sonomicrometric and micromanometric techniques for data acquisition.

Main Results:

• Immediately post-reinfusion, Emax was unchanged, but LV compliance significantly decreased in all dogs.
• Survivors showed progressive recovery of LV compliance over 4 days, with stable Emax.
• Non-survivors exhibited progressive loss of LV compliance and a significant decrease in Emax prior to death.

Conclusions:

• Cardiac contractility (Emax) may be initially preserved or improved after HS, but diastolic dysfunction (decreased compliance) is a consistent early finding.
• Recovery of diastolic function is observed in survivors, while progressive diastolic and systolic dysfunction characterize non-survivors.
• Diastolic dysfunction plays a critical role in the cardiac response to and outcome from severe hemorrhagic shock.