Understanding Hemodynamic Assessment: Preload, Afterload, and Contractility, Slides of Pediatrics

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Hemodynamic

Assessment and

Invasive Monitoring

Overview

• Introduction
• Hemodynamic Determinants & Assessment
• Monitoring Considerations - A Cautionary Tale - Monitoring indications - “Normal Values” - Complications - Hemodynamic scenarios

Eminence Based Medicine

• Experience is worth any amount of

evidence

• “making the same mistakes with

increasing confidence over an

impressive number of years”

Introduction

• Purpose of repeated hemodynamic

assessment and continuous monitoring

• Gain an understanding of the patient’s physiologic status
• Make timely interventions
• Assess effectiveness of therapies
• Provide warning of hemodynamic changes that may be dangerous

Hemodynamic

Determinants

Preload

Afterload

Contractility

Heart Rate

Rhythm

Hemodynamic Determinants

• Ohm’s Law (V= I X R)
  • BP = CO X SVR
• Important Physiologic principle
  • manipulation of variables can alter hemodynamics
  • Ex. BP can be normal in the face of low CO when….

DO 2

CaO 2

CO

Sat %

PaO 2

Hg

HR

SV

Preload

Contractility

Afterload

Starling’s Law

Preload

1

2

3

Hemodynamic

Assessment

Cardiac output I

• Pulse quality
• Central vs. Peripheral pulses
• Differential Temperatures
  • Dipstick of SVR and indirectly CO
  • Capillary refill time (CRT)

Hemodynamic Assessment

• Stroke volume - pulse quality
• Preload - Liver size, CXR - heart size
  • Relative liver size may be better than CVP for initial assessment of preload
• SVR - CRT, Pulse pressure,

differential temperatures

Inadequate Hemodynamics

• Common features
  • Elevated HR - attempt to  CO
  • Elevated RR - beware Resp. alkalosis
  • Decreased pulses -  CO
  • Depressed LOC -  CO
  • Acidosis -  CO
  • Falling UOP -  CO

Monitoring Considerations

• Minimal risk to patient
• Noninvasive and painless if possible
• Data should be reproducible, relevant

and understandable

• Provide easy visual or auditory queues

A Cautionary Tale

• Virginia PICU 1989 to 1993,
  • Two separate groups of Intensivists
  • 78 Infants with RSV disease
    • Group 1 - (n=38) invasive monitoring
    • Group 2 - (n=40) less monitoring
      • Groups comparable re: age, gender, disease severity, and medical Hx. D. Wilson, (J.Pediatr 1996:128:357-62)