This episode of Think Like a Nurse breaks down the critical hemodynamic concepts that every ICU nurse and nursing student needs to know for NCLEX success. We explore cardiac output (CO), cardiac index (CI), stroke volume (SV), and the three main determinants: preload, afterload, and contractility. With a focus on understanding how these concepts affect tissue perfusion and oxygen delivery, we emphasize how ICU nurses use dynamic assessments and interventions to stabilize patients and prevent complications. Mastering these concepts not only prepares you for NCLEX but also equips you to provide life-saving care at the bedside.
Hemodynamics is the key to understanding tissue perfusion and oxygen delivery.
Cardiac output (CO) = Stroke volume (SV) × Heart rate (HR). Normal range: 4-8 L/min.
Cardiac index (CI) normal range: 2.5-3.5 L/min/m². CI adjusts CO for body surface area (BSA).
Stroke volume (SV) normal range: 60-100 mL/beat, influenced by preload, afterload, and contractility.
Preload: Volume of blood in the ventricle before contraction; assessed with central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP).
Afterload: The resistance the heart must overcome to eject blood; influenced by systemic vascular resistance (SVR).
Contractility: The strength of the heart muscle contraction; assessed through cardiac index (CI) and ejection fraction (EF).
Key interventions: Fluid boluses for low preload, diuretics for high preload, vasopressors for low afterload, and inotropes for low contractility.
Dynamic assessments like passive leg raise (PLR) help determine fluid responsiveness, reducing over-resuscitation.