1. Cardiac Output (CO): 4–8 L/min
- Volume of blood ejected by the heart per minute.
- Reflects overall cardiac function.
2. Cardiac Index (CI): 2.2–4.0 L/min/m²
- CO adjusted for body surface area.
- More precise than CO to assess cardiac function, especially in patients of varying sizes.
3. Central Venous Pressure (CVP): 2–8 mm Hg
- Measures right ventricular preload (pressure after filling).
- Indicates intravascular fluid status (hypovolemia vs fluid overload).
4. Pulmonary Artery Wedge Pressure (PAWP): 6–12 mm Hg
- Measures left ventricular preload.
- Helps assess left-sided heart function and pulmonary congestion.
5. Systemic Vascular Resistance (SVR): 800–1200 dynes/sec/cm⁻⁵
- Measures systemic vascular resistance.
- Helps differentiate between vasodilation (low SVR) vs vasoconstriction (high SVR).
6. Mean Arterial Pressure (MAP): 70–105 mm Hg
- Average pressure in the arteries throughout the cardiac cycle.
- Calculated as:
MAP = (SBP + 2 × DBP) ÷ 3 - MAP ≥60 mm Hg is needed to perfuse vital organs.
Optimal MAP: ≥70 mm Hg for adequate tissue perfusion. - MAP <60 mm Hg may lead to ischemia, organ damage, and death without prompt intervention.
Common Causes of Low MAP:
- Hypovolemia: hemorrhage, severe dehydration.
- Septic shock.
- Heart failure.
Interventions for Low MAP:
- Volume expanders: IV fluids, albumin, blood products.
- Vasopressors: norepinephrine, vasopressin → promote vasoconstriction.
- Inotropes: dobutamine → improve cardiac contractility.
Key Point for NCLEX:
MAP is the most reliable parameter for evaluating tissue perfusion. A MAP <60 mm Hg is a clinical emergency requiring immediate intervention to prevent irreversible organ damage.
References:
- Ignatavicius, D. D., & Workman, M. L. (2021). Medical-surgical nursing: Concepts for interprofessional collaborative care (10th ed.). Elsevier.
- Lewis, S. L., Bucher, L., Heitkemper, M. M., & Harding, M. M. (2020). Medical-surgical nursing: Assessment and management of clinical problems (11th ed.). Elsevier.
- UWorld NCLEX-RN. (2024). NCLEX-RN QBank and Rationales. Retrieved from https://www.uworld.com
- American Heart Association. (2020). Advanced Cardiovascular Life Support Provider Manual. AHA.
- LeMone, P., Burke, K. M., Bauldoff, G., & Gubrud, P. (2019). Medical-surgical nursing: Clinical reasoning in patient care (7th ed.). Pearson.