Assessment of hydration

Question 1

Assessment of hydration-Clinical (1)

Answer 1

• Clinical assessment and lab tests
• Skin turgor ( care with elasticity )
• Mucous membranes ( esp tongue )
• HR and BP changes from horizontal to upright
• Core-peripheral temperature gradient ( also an assessment of CO )
• Urine output
• ( Thirst )
• Trends more useful than a single reading (sometimes single reading all one has)

Question 2

Hydration-Clinical 2

Answer 2

• Fluid balance only a problem in those who cannot drink
• Distinguish thirst from a dry mouth ( O2 therapy )
• Thirst a response to hypovolaemia ( baroceptors ) and small changes in osmolarity
• ↓skin turgor indicates a deficit of 10%
• Hypotension may occur and imply significant deficits ( 20-30 % )
• A healthy subject may lose 15-20% of CV and show only a tachycardia
• Care in patients with autonomic dysfunction

Question 3

Hydration –clinical 3

Answer 3

• Cardiac , renal and hepatic function MUST be assessed
• Pitting oedema, ↑JVP, ↑urine output may be seen in circulatory overload in a normal patient
• Pulmonary oedema is a late sign of hypervolaemia in pts with a normal CVS
• Care in interpreting CVP-low values ( <5mmHg )
• Fluid challenge-assess compliance of circulation in response to a fluid load ( say 250ml ) by observing haemodynamic/clinical response

Question 4

Laboratory tests

Answer 4

Rising PCV
↑ing Na ( and ↑Urinary Na >20mmol/L
↑ing acidosis ( metabolic )
Changes in Urea and creatinine need careful interpretation ( renal function, age )

Question 5

The normal situation

Answer 5

• Pts who can drink are no problem
• Problems arise in those with hepatic, renal, cardio-respiratory disorders.
• Care in those with complications ( ileus, sepsis )
• Extra care in certain types of surgery ( neurosurgery )
• Normal adults require 2-3 litres fluid /day ( 35ml/kg/24hrs )
• Na+ 2 mmol/kg
• K + 1 mmol/kg

Question 6

The abnormal situation

Answer 6

• Pts are usually fluid depleted
• Vomiting or diarrhoea
• Burns, pyrexia
• Third space losses (ascites, effusions )
• Haemorrhage
• Care with the elderly, confusion
• Prolonged nil by mouth ( pre-op cancellations )

Question 7

How can hypovolaemia be assessed

Answer 7

• Invasive high-tech facilities not always needed-so in both diagnosis and response to treatment
• Check HR
• BP
• Capillary refill
• Core-peripheral temperature gradient
• Urine output
• O2 sats
• GCS

Question 8

What is the likely electrolyte status

Answer 8

• Review
• History ( what is the source of loss-vomiting, diarrhoea,fistula )
• Lab results
• Any fluid therapy charts ( all intake, output and think of insensible )
• Replacement should replace like with like
• Always give potassium even if K+ within normal range

Question 9

What might happen next

Answer 9

• Anticipate losses ( n/g tube, fistula, ileus )-fluid/electrolyte losses
• Third spaces losses
• Insensible losses
• Fluid intake-oral, drug infusions,
• CVP/arterial line flushing ( intraflo 3ml/hr )

Question 10

Indications for iv fluid therapy

Answer 10

• Patient unable to take fluid orally
• Major operations esp GI
• Severe diarrhoea and vomiting
• Resuscitation-hypovolaemia due to whatever cause
• Critical situations-cardiac arrest, poisoning, anaphylaxis
• Unconscious patient
• TPN