Clinical Assessment​​​​

• Evidence of hypovolaemia​

  • Thirst

  • Tachycardia​

  • Hypotension

    • Hypotension on its own is not necessarily an indicator of hypovolaemia​

    • The hypotensive patient should be assessed for all causes of shock

  • Postural hypotension

  • Oliguria (< 0.5 ml/kg/hr persistently)

  • Cold peripheries, poor peripheral perfusion

  • Delayed capillary refill

  • Dry mucous membranes

  • Increased skin turgor

  • Low JVP

• Evidence of Hypervolaemia

  • Bilateral dependent crepitations​

  • Dependent oedema

    • Usually pitting oedema​

  • Engorged venous system

  • Elevated JVP

    • > 3 - 4 cm above the sternal notch at 45 degrees​

    • May be identified as a double pulsation lying lateral to sternocleidomastoid

    • A number of limitations exist (see CVP below)

​

Additional Assessment

• Central venous pressure (CVP)

  • Invasive measure of venous pressure via central venous catheter

    • Objective measure of JVP​

  • Affected by many factors​ other than venous blood volume

    • Eg. patient position, CVC position, venous compliance, respiration, cardiac function, valvular function​

  • An individual CVC measurement correlates poorly with fluid status

    • A trend, in conjunction with other assessment markers, may be more helpful

• Fluid balance chart

  • Notoriously unreliable

  • Various assumptions:

    • Patient is euvolaemic on admission

    • We accurately measure all output (We don't!)

      • Faecal water loss​

      • Respiratory water loss

        • Increased loss in the patient who is tachypnoeic or breathing dry wall gas​

      • Sweating

        • Increased evaporative water loss in the febrile patient​

• Daily weights

  • Day to day weight variation can provide a trend of water balance​

  • Limitations

    • Prone to measurement errors (eg. different scales, etc.)​

    • Difficult to perform accurately in critically unwell patients

​

Investigations

• Pathology

  • Haematocrit​

    • Ratio of cellular component to plasma component of intravascular fluid sample​

    • Increased haematocrit is seen with hypovolaemia

  • Haemoglobin

    • Similar to haematocrit; Decreased intracellular fluid --> increased Hb concentration​

  • Sodium

    • Generally, provides an idea of total body water​

      • ie. Elevated total body water causes hyponatraemia and vice versa​

      • MUST be interpreted within context of clinical assessment as various other factors may also alter sodium levels

  • Renal function

    • Creatinine is an indirect marker of renal function rather than fluid balance​

    • A rise in urea, out of proportion to creatinine, may be a marker of acute hypovolaemia

• Imaging

  • Chest XR​

  • TTE

    • Requires a skilled operator​​​​