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Being able to assess the hydration status of a patient is an important skill that you’ll use regularly in clinical practice. It involves assessment of whether a patient is hypovolaemic (dehydrated), euvolaemic or hypervolaemic (fluid overloaded) to inform ongoing clinical management.

Hypovolaemia refers to an overall deficit of fluid in the body. Causes include poor fluid intake, excessive fluid loss (e.g. vomiting, diarrhoea, haemorrhage or excessive diuretic therapy) and third space loss of fluid (where fluid remains within the body but has shifted from the intravascular space to another compartment within the body).

Hypervolaemia refers to an excess of fluid in the body. Colloquially it is often referred to as fluid overload. Hypervolaemia is common in the elderly and those with renal or cardiac failure.  It can be caused by excessive fluid intake or inappropriate fluid retention (e.g. heart failure, renal failure).

The quest to euvolaemia can be a difficult road to tread.  Searching for the perfect fluid balance involves assessing an array of clinical symptoms, signs and biochemical indicators. No single parameter or ‘gold standard’ confirms a state of adequate hydration, and the clinician must contemplate a range of factors to fully appreciate whether the patient is hypovolaemic, euvolaemic or hypervolaemic.


Patient factors to consider that may alter fluid homeostasis

Patient’s age

Reasons for admission that can increase fluid requirements:

  • Trauma
  • Febrile illness and sepsis
  • Burns
  • Surgical patients may need additional volume secondary to:
    • Bleeding
    • Drainage
    • Third-space fluid losses
  • Gastrointestinal losses (vomiting, diarrhoea)
  • Polyuric patients

 

Medical conditions that can affect fluid balance (e.g. renal disease, congestive cardiac failure)

Medications (e.g. diuretics can increase fluid losses)

 

Pertinent details in the history:

  • Bleeding from any source
  • Vomiting: frequency, amount, blood
  • Stools: frequency, amount, blood
  • Fevers and diaphoresis
  • Urine output: colour and amount
  • Lightheaded at rest or on standing
  • Presence of thirst
  • Eating and drinking status: Is the patient nill by mouth and/or receiving IV fluid therapy?
  • Symptoms of fluid overload: shortness of breath, orthopnoea, paroxysmal nocturnal dyspnoea, leg swelling
  • Is the patient on a fluid restriction for another medical condition? (e.g. heart failure)

Introduction

  • Introduce yourself
  • Wash hands
  • Confirm patient details
  • Explain the examination
  • Gain consent
  • Check if the patient currently has any pain

General inspection

  • Age (elderly/very young more prone to dehydration and elderly generally more likely to have cardiac failure/chronic renal disease)
  • Shortness of breath (may indicate pulmonary oedema)
  • Scars/dressings indicating recent surgery
  • Visible oedema (indicating fluid overload)
  • Colour (pallor may indicate hypovolaemia secondary to blood loss)
  • Adjuncts which may provide clues as to fluid status (intravenous fluids, catheter, stoma bag, drains)

 

Bedside charts/data

Vital signs:

  • Tachycardia (associated with hypovolaemia)
  • Hypotension (associated with hypovolaemia)
  • Increased respiratory rate (may suggest pulmonary oedema secondary to fluid overload)

 

Fluid balance chart:

  • Input and output chart documenting all fluid volume in and out of the patient on a 24-hour basis
  • Assess the overall fluid balance (positive vs negative)
  • Note if the patient is on a fluid restriction (e.g. patients with heart failure/SIADH)

 

Daily weight chart:

  • Assess the overall trend to see if the patient is gaining or losing weight

 

Stool chart:

  • Note the frequency and type of bowel motions (e.g. frequent diarrhoea will result in significant fluid losses)

 

Medication chart:

  • Assess if the patient is on any medications that may alter fluid balance (e.g. furosemide will cause increased urine output)

 

Fluid prescription chart:

  • Note if the patient has received any intravenous fluids
  • If they have, take note of the volume and type of fluid administered

 

Surgical documentation (if the patient is post-op):

  • Estimated blood loss in the operating theatre
  • Blood transfusions intraoperatively
  • IV fluids administered intraoperatively

Hands

Hands out with palms facing down:

  • Looks at the hands – note any oedema or peripheral stigmata of relevant diseases (e.g. leukonychia may indicate hypoalbuminaemia)
  • Assess peripheral temperature – cool peripheries may indicate hypovolaemia
  • Palpate the radial pulse – tachycardia may indicate hypovolaemia
  • Check capillary refill time (normally less than 2 seconds) – prolonged in hypovolaemia

Arms

  • Measure blood pressure – hypotension may indicate hypovolaemia
  • Lying and standing blood pressure (drop of 20mmHg systolic on standing indicates postural hypotension) – associated with hypovolaemia
  • Assess skin turgor by gently pinching a fold of skin (this can be done on the back of the hand or neck), hold for a few seconds and then release the skin. Well hydrated skin should spring back to its previous position straight away, however, in dehydration, the skin will slowly return to normal and this is referred to as decreased skin turgor

Face

  • Mucous membranes – if dry may indicate dehydration (although not specific as can also be caused by drugs such as anticholinergics)
  • Sunken eyes are associated with dehydration
  • Conjunctival pallor (a sign of anaemia which could indicate underlying renal/cardiac disease or haemorrhage)

Neck

Jugular venous pressure (JVP):

  • Visualisation of the internal jugular vein at a 45-degree angle between the heads of the sternocleidomastoid
  • In healthy people, the filling level of the jugular vein should be less than 3 centimetres vertical height above the sternal angle
  • If JVP > 3cm you need to consider fluid overload

Chest

  • Note the respiratory rate (increased in pulmonary oedema)
  • If capillary refill is abnormal peripherally, repeat centrally on the sternum
  • Listen to the four valves and assess for any added heart sounds (S3 gallop rhythm may be heard in fluid overload)
  • Auscultate the lungs – bilateral coarse crackles may indicate pulmonary oedema
  • Assess for sacral oedema – associated with fluid overload

Abdomen

Assess for abdominal ascites:

  • A distended abdomen may indicate the presence of ascites
  • Assess for shifting dullness to help differentiate ascites from other causes of abdominal distension

Legs

  • Check for pedal oedema – associated with fluid overload
  • If pedal oedema is present, assess what level this extends to (e.g. knee)

Outputs

Urine output:

  • Assess volume (reduced in dehydration)
  • Assess colour (concentrated in dehydration/dilute in fluid overload)
  • Average urine output should be approximately 0.5mL/kg/hour

 

Drain output:

  • Quantity and type of output (e.g. blood/pus/bowel contents)

 

Wounds:

  • Assess for fluid losses from wounds
  • Note the type of fluid being lost (e.g. blood/pus)

To complete the examination

  • Thank patient
  • Wash hands
  • Summarise your findings

Further investigations

Bloods tests

FBC:

  • Sudden drop in haemoglobin may suggest haemorrhage
  • Haematocrit is often raised in dehydration

 

Urea/Creatinine:

  • Raised in dehydration (may have acute kidney injury)
  • Urea raised in upper gastrointestinal haemorrhage
  • Chronic renal failure

 

Sodium is elevated in dehydration and may be low in fluid overload (dilutional hyponatraemia)

Imaging

  • Chest X-ray to assess for pulmonary oedema
  • Echocardiogram to assess for heart failure
  • Bladder scan to assess for urinary retention
  • Abdominal ultrasound to assess renal tract and also rule out ascites

 

Other

  • Daily weights to help monitor fluid balance
  • Urine osmolality can be useful if considering SIADH and diabetes insipidus

References

Databases:

  • UpToDate: Maintenance and replacement fluid therapy in adults
  • UpToDate: Overview of postoperative fluid therapy in adults

 

Books:

  • Maril, P. Handbook of Evidence-Based Critical Care. Chapter 8 Fluid Resuscitation and Volume Assessment. Springer, 2010.
  • Advanced Trauma Life Support (ATLS) Student Course Manual (9th edition)
  • Donaghy, L., Remacz, J., Salvatore,D., Scemons, D., Thweatt, P. and Trujillo, L. (2010). Fluids and Electrolytes: an incredibly easy pocket guide. 2nd ed. Lippincott, Williams and Wilkins: Philadelphia.

 

Websites:


 

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