Monitoring in Critical Care

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Monitoring in Critical Care
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General Guidelines

• Monitoring ensures rapid detection of changes in
  the clinical status
• Allows for accurate assessment of progress and
  response to therapy
• When clinical signs and monitored parameters
  disagree, assume that clinical assessment is
  correct
• Trends are generally more important than a single
  reading
• Use non-invasive techniques when possible
• Alarms are crucial for patient safety

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Hemodynamic Monitoring

• Blood Pressure
• Can be measured intermittently with a cuff or
  continuously with an arterial line
• BP does not reflect CO BP can be high with a
  low CO if vasoconstriction occurs and vice versa
• Central Venous Pressure (CVP)
• Measured in internal jugular vein or subclavian
  vein, reflecting right atrial pressure
• May be used to assess volume

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Hemodynamic Monitoring, cont

• Pulmonary Artery Wedge Pressure (PAWP)
• Reflects left atrial pressure
• Normal is 6-12 mm Hg
• Cardiac Output (CO)
• Usually measured by thermodilution PA catheter
• Can also be measured by dye dilution,
  transesophageal Doppler, echo, or impedence
  plethysmography
• EKG
• Monitors rate and rhythm of heart

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Respiratory Monitoring

• ABG
• Monitors acid-base balance, PaO2, and PaCO2
• Oxygen Saturation
• SpO2, using a finger or other probe, measures the
  proportion of saturated to desaturated hemoglobin
• Requires adequate perfusion for accuracy
• Oxygenatio is OK if SpO2 gt90

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Respiratory Monitoring, cont

• Mixed venous O2 saturation (SvO2)
• Measured with PA catheter
• Normal is 65-75
• Low SvO2 may indicate inadequate tissue O2
  delivery (even if arterial O2 is OK)
• Lung Function
• Aa gradient and PaO2/FiO2 ratio measure the
  adequacy of gas exchange
• Arterial to end-tidal CO2 gradients indicate the
  adequacy of ventilation
• PF, FEV1, and FVC help assess patients with lung
  dx
• MIP/NIF is used to determine readiness for
  extubation

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Respiratory Monitoring, cont

• Respiratory compliance
• Vt/PIP-PEEP
• A measure of the ease of inflation
• High airway pressures during mechanical
  ventilation may be caused by low compliance
• Capnography
• End-tidal CO2 concentration is close to artrial
  PaCO2 levels
• Indicates the adequacy of alveolar ventilation

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Organ and Tissue Oxygenation

• Global measures
• Reflect the adequacy of total tissue perfusion
  but could be normal with local perfusion
  abnormalities
• Increased lactate concentration and metabolic
  acidosis suggests anaerobic metabolism and
  inadequate tissue oxygenationlactate also
  increases with liver failure and sepsis, though
• SvO2 lt55 indicates global tissue hypoxia

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Organ and Tissue oxygenation

• Organ-specific Measures
• Urine flow
• A sensitive indicator of renal perfusion provided
  the kidneys arent damaged
• Normal is 1ml/kg
• Core-peripheral temperature
• The gradient between peripheral (skin) temp and
  core (rectal) is often used as an index of
  peripheral perfusion
• The less perfusion, the colder the periphery

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Organ and Tissue Oxygenation

• Organ-specific Measures
• Gastric tonometry
• Used to detect shock-induced splanchnic ischemia
  by measure gastric luminal PCO2 and deriving the
  mucosal pH
• Neurological monitoring
• Utilizes GCS, ICP measurement, and jugular venous
  bulb saturation