Dehydration

Question 1

Diagnosing dehydration can be complicated, laboratory features include:

Answer 1

• Hypernatraemia
• Rising haematocrit
• Metabolic acidosis
• Rising lactate
• Increased serum urea to creatinine ratio
• Urinary sodium <20 mmol/litre
• Urine osmolality approaching 1200mosmol/kg

Question 2

Pre operative fluid management?

Answer 2

• Fluid management has been described in the British Consensus guidelines on IV fluid therapy for Adult
• Surgical patients (GIFTASUP) and by NICE (CG174 December 2013)

Question 3

The Recommendations include?

Answer 3

• Use Ringer’s lactate or Hartmann’s when a crystalloid is needed for resuscitation or replacement of fluids. Avoid 0.9% N. Saline (due to risk of hyperchloraemic acidosis) unless patient vomiting or has gastric drainage.
• Use 4%/0.18% dextrose saline or 5% dextrose in maintenance fluids. It should not be used in resuscitation or as replacement fluids.
• Adult maintenance fluid requirements are: Na 50-100 mmol/day and K 40-80 mmol/day in 1.5-2.5L fluid per day.
• Patients for elective surgery should NOT be nil by mouth for >2 hours (unless has disorder of gastric emptying).

Question 4

The Recommendations include?

Answer 4

• Patients for elective surgery should be given carbohydrate rich drinks 2-3h before. Ideally this should form part of a normal pre op plan to facilitate recovery.
• Avoid mechanical bowel preparation.
• If bowel prep is used, simultaneous administration of Hartmann’s or Ringer’s lactate should be considered.
• Excessive fluid losses from vomiting should be treated with a crystalloid with potassium replacement. 0.9% N. Saline should be given if there is hypochloraemia.
• Otherwise Hartmann’s or Ringer lactate should be given for diarrhoea/ileostomy/ileus/obstruction. Hartmann’s should also be given in sodium losses secondary to diuretics.
• High risk patients should receive fluids and inotropes.

Question 5

The Recommendations include?

Answer 5

• An attempt should be made to detect pre or operative hypovolaemia using flow based measurements. If this is not available, then clinical evaluation is needed i.e. JVP, pulse volume etc.
• In Blood loss or infection causing hypovolaemia should be treated with a balanced crystalloid or colloid (or until blood available in blood loss).
• A critically ill patient is unable to excrete Na or H20 leading to a 5% risk of interstitial oedema. Therefore 5% dextrose as well as colloid should be given.
• If patients need IV fluid resuscitation, use crystalloids that contain sodium in the range 130-154 mmol/l, with a bolus of 500 ml over less than 15 minutes (NICE Guidance CG 174).