Hemodynamic Monitoring in ICU

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Hemodynamic Basics - Vitals Vigilance

  • Goal: Maintain organ perfusion & oxygenation.
  • Core Vitals: HR, BP (SBP, DBP, MAP, PP), SpO2.
  • Mean Arterial Pressure (MAP):
    • Formula: $MAP = DBP + \frac{1}{3}(SBP - DBP)$
    • Normal: 70-100 mmHg.
    • Target in shock: $\geq \textbf{65}$ mmHg.
  • Pulse Pressure (PP):
    • Formula: $PP = SBP - DBP$
    • Normal: 30-50 mmHg.
    • Narrow PP (<25 mmHg or <25% SBP) suggests $\downarrow$ stroke volume.
  • Shock Index (SI):
    • Formula: $SI = \frac{HR}{SBP}$
    • Normal: 0.5-0.7.
    • SI > 0.9 indicates shock. 📌 "Heart over Pressure". MAP and Pulse Pressure Calculation

⭐ A MAP < 60 mmHg compromises vital organ perfusion, especially coronary, cerebral, and renal flow.

Arterial Monitoring - Arterial Line Lowdown

  • Indications: Continuous BP (vasoactive drugs), frequent ABGs, advanced hemodynamics (PPV/SVV).
  • Sites:
    • Radial (Allen's test pre-cannulation).
    • Femoral (larger bore; ↑ risk infection/thrombosis).
    • Others: Brachial, axillary, dorsalis pedis.
  • Waveform: Systolic upstroke, peak, dicrotic notch (aortic valve closure), diastolic.
    • MAP $\approx DBP + \frac{1}{3} (SBP - DBP)$. Arterial line waveforms: Underdamped, normal, overdamped
  • Complications: Ischemia, thrombosis, hemorrhage, infection, nerve injury. ⚠️ Accidental drug injection.
  • Troubleshooting:
    • Damped: ↓SBP, ↑DBP (air, clot, kink).
    • Resonant: ↑SBP, ↓DBP (stiff/long tubing).

⭐ MAP is generally preserved in damping/resonance.

Central Venous Pressure - Central Clues

  • Measures right atrial pressure (RAP); estimates RV preload. Normal: 2-8 mmHg.
  • Measured via Central Venous Catheter (CVC).
  • Sites: Internal Jugular (preferred), Subclavian, Femoral.
  • Waveform:
    • a: Atrial contraction.
    • c: Ventricular contraction (tricuspid bulge).
    • x: Atrial relaxation.
    • v: Venous filling.
    • y: Ventricular filling.
  • Uses: Volume status, drug admin, TPN.
  • Complications: Pneumothorax, infection, thrombosis. CVP waveform components and relation to ECG

⭐ Cannon 'a' waves on CVP trace suggest atrial contraction against a closed tricuspid valve (e.g., junctional rhythm, complete heart block).

Pulmonary Artery Catheter - Swan's Song Stats

  • A balloon-tipped, flow-directed catheter providing key hemodynamic data.
  • Measures: Central Venous Pressure (CVP), Pulmonary Artery Pressure (PAP), Pulmonary Capillary Wedge Pressure (PCWP), Cardiac Output (CO), Mixed Venous Oxygen Saturation (SvO2).
  • Indications: Differentiating shock types, guiding therapy in severe cardiac/pulmonary dysfunction (e.g., ARDS, cardiogenic shock), major surgeries.
  • Risks: Arrhythmias (most common), PA rupture, infection, thromboembolism, valvular damage.
ParameterNormal Value
CVP2-6 mmHg
PAP (sys/dia)15-30 / 8-15 mmHg
PCWP6-12 mmHg
CO4-8 L/min
SvO260-80%

⭐ PCWP is an indirect measure of Left Atrial Pressure (LAP) and Left Ventricular End-Diastolic Pressure (LVEDP), reflecting LV preload. A PCWP >18 mmHg often suggests cardiogenic pulmonary edema.

Functional Hemodynamics - Dynamic Flow View

Dynamic assessment of fluid responsiveness and cardiac output.

  • Key Dynamic Indices (Mech. Vent. Pts):
    • Stroke Volume Variation (SVV): If > 10-15%, suggests fluid responsiveness.
    • Pulse Pressure Variation (PPV): If > 10-13%, suggests fluid responsiveness.
  • Bedside Echo: IVC variability, LVOT VTI changes.
  • Other CO: PiCCO, LiDCO.

Arterial, airway pressure, and plethysmography waveforms

⭐ Dynamic indices (SVV, PPV) are superior to static CVP/PAOP for predicting fluid responsiveness in ventilated patients.

High‑Yield Points - ⚡ Biggest Takeaways

  • Arterial lines: continuous BP monitoring, frequent ABGs.
  • CVP (2-6 mmHg): reflects RV preload; guides fluid status.
  • PAC: measures PCWP (6-12 mmHg) for LV preload, CO, SvO2.
  • Low SvO2 (<60%): signals impaired tissue oxygen delivery or ↑consumption.
  • Elevated lactate: key marker of tissue hypoperfusion & anaerobic metabolism.
  • Dynamic indices (PPV, SVV): best predict fluid responsiveness in ventilated patients.
  • Use parameters for goal-directed therapy in shock to improve outcomes.

Practice Questions: Hemodynamic Monitoring in ICU

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Flashcards: Hemodynamic Monitoring in ICU

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Only clinical indicators of perfusion of the gastrointestinal tract and muscular beds are the global measures of _____ and the mixed venous oxygen saturation

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Only clinical indicators of perfusion of the gastrointestinal tract and muscular beds are the global measures of _____ and the mixed venous oxygen saturation

lactic acidosis

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