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Pulse / Blood pressure

Blood pressure

MABP - Pv = HR x SV x TPR

Systolic pressure = Pressure from force of cardiac contraction
Diastolic pressure = Pressure from resistance arterioles when heart is relaxed
Pulse pressure = Systolic - Diastolic pressure
Mean arterial pressure = Diastolic +1/3Pulse pressure; Eg BP 120/80 - MABP = 93

 

  Systolic Diastolic Pulse pressure MABP
Exercise Increased Reduced Widened  
Shock Reduced Reduced Reduced/narrow  
Aortic regurgitation Increased Reduced Widened  

Korotkoff sounds

  1. First sound (Systolic pressure)
  2. Louder
  3. Softer
  4. Muffled (used in pregnancy when 5th sound may be "absent")
  5. Silence (Diastolic pressure)

 

Blood pressure monitoring

Dichrotic notch = momentary rise in arterial pressure on closure of aortic valve

  1. Non-invasive
    • Sphygmomanometer
  2. Invasive
    • Direct cannulation of peripheral artery (should perform Allen's test; competence of collateral ulna arterial circulation - positive if hand still blanched 15 seconds later)
    • Gives continous waveform trace after attachment to electrical transducer
    • Complications of art lines: haematoma, digital ischaemia, pseudoaneurysm, AVfistula, exsanguination

 

Pulse changes along arterial tree

  • Occur due to changes in wall stiffness along arterial tree
  • Radial: higher systolic, lower diastolic, higher PP, lower MAP 

 

Pulses

  1. Anacrotic pulse: slow rise and low amplitude in AS
  2. Waterhammer pulse: Rapid rise and decline in AR
  3. Pulsus Bisferiens: Mixed aortic vavle disease - "double peak"
  4. Pulsus Alternans: Random variation in amplitude of arterial pressure - LVF
  5. Pulsus Paradoxus
    • Exaggerated >10mmHg reduction in arterial pressure on inspiration
    • Inspiration - reduced intrathoracic pressure - increase venous return - increase right sided end-diastolic volume - leads to bulging into left ventricle reducing size (Bernheim effect)
    • Increased pooling of blood in expanded lungs - reduced return to left side of heart
    • Negative pressure transmitted to thoracic aorta
    • Effect is reduced pulse pressure
      Paradox is (1) audible heart sounds yet (2) no palpable pulse

      Causes of Pulsus Paradoxus

  6. Changes in intrathoracic pressure
    		 Increased pooling in lungs Reduced return to left side of heart
    • Bronchial asthma (lung hyperinflation)
    • Ventilated patients (waking off sedation)
    • Pulmonary embolus (+RV dysfunction)
    • Asthma
    • Tamponade
    • Constrictive pericarditis
    • Pneumothorax

 

 

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