Outline the components required to measure blood pressure from an intra-arterial catheter. What information (other than blood pressure) may be gained from an arterial line trace?

Master answer

Process

• BP pulsations transmitted from arterial cannula up the tubing to transducer
• Woks by hydraulic coupling between blood and saline
• Transducer converts pressure waves to electrical signals (via strain gauge and wheatstone bridge)
• Signal amplified and displayed on monitor

Information which may be gained from an arterial line trace:

• Normal trace
  • Pulse rate and rhythm
  • Arrhythmias
  • Morphology:
    • Slow rising in AS
    • Steepness of ascending phase:
      • Increased: Inc Systemic vascular resistance, vasopressors, inc contractility
      • Decreased: Septic shock, vasodilators
    • Dicrotic ‘fall-off’ : changes with changes in SVR
  • Variation with insertion site: Further from aorta: taller systolic peak, delayed dicrotic notch, lower end diastolic pressure, later arrival of pulse
• Dampened trace
  • Kinks/bubbles/clots
  • Overly compliant tubing
• Hyperactive trace
  • Noncompliant tubing, reverberations, increased vascular resistance
• Arterial line swing
  • Reduction in venous return
  • Hyperexpansion of lungs
  • Pulse pressure variation (~fluid responsiveness)
  • Pulsus alternans in tamponade
• Adjuncts: Pulse contour analysis with PICCO / other devices

JC 2019

Answer by JC