A condition where losses of bodily fluids from whatever cause has led to significant disturbance in the normal fluid and electrolyte levels needed to maintain physiological functions
Water and electrolyte exchange
• Fluid consumption is 2-2.5L in 24 hours (1.5L by mouth and 0.5-1L in solid food)
• Daily fluid loss is through:
- urine (800-1,500mL)
- stool (250mL)
- insensible loss through skin and lungs (600mL) which is affected by hyperventilation, fever and high environmental temperatures
• Daily sodium intake is 100-200mmol
• Daily potassium intake is 50-100mmol
• There will be a deficiency of salts if:
- there are increased losses, eg. excess sweating, urinary losses or GIT losses through diarrhoea and vomiting
- there is reduced intake, eg. post-operative patients
Disorders of fluid and electrolytes
Disorders may occur in the volume, concentration and distribution of fluid and electrolytes. The main disorders likely to cause such problems are:
• Diarrhoea
• Vomiting
• Burns
• Haemorrhage
• Intestinal obstruction
• Peritonitis
• Diabetes
• Nasogastric drainage
• Paralytic ileus
• Fistula drainage (especially if high output)
• Sequestration after muscle trauma
• Major organ failure (eg. renal, hepatic, cardiac)
Caution
Over-infusion of IV fluids may also cause fluid and electrolyte imbalance
Mild to moderate fluid loss will lead to varying degrees of dehydration
Severe fluid loss will lead to shock
IV fluid and electrolyte therapy
HC2
This has three main objectives:
• To replace lost body fluids
• To correct electrolyte and acid-base disturbances
• To maintain daily fluid requirements
Always use an IV drip in patients who are seriously ill* and may need IV drugs or surgery. If the fluid is not needed urgently, run it slowly to keep the IV line open.
(*except patients in congestive heart failure – for these use only an indwelling needle) |
Administer daily fluid and electrolyte requirements to any patient not able to feed
The basic 24-hour requirement for a 60kg adult is 3L and for children is 150mL/kg
One third of these daily fluids (1L in an adult) should be (isotonic) sodium chloride 0.9% infusion
The other two thirds (2L in an adult) should be: glucose 5% infusion
or half-strength Darrow’s solution in glucose 2.5% infusion or compound sodium lactate infusion (Ringer-Lactate solution)
As well as the daily requirements replace increased fluid lost due to the particular condition according to the assessed degree of dehydration (see p332)
Caution
Closely monitor all IV drips to ensure that the rate is adjusted as required and that the drip is not allowed to run dry as this will introduce air bubbles into the circulation with the potentially fatal risk of air embolus
If the drip has been neglected and allowed to run dry, remove it and set up a new drip at another site
Clinical features of severe dehydration - see also p332 and p336
• Inelastic skin (loss of skin turgor)
• Sunken eyes & fontanelle
• Rapid, thready pulse
• Low BP
Clinical features of hypovolaemia
• Tachycardia (rapid pulse, often thready, small volume)
• Low BP
• Postural change (eg. supine to sitting/standing - change in heart rate and BP)
In diarrhoea and vomiting with severe dehydration, paralytic ileus, etc:
Replace fluid losses with isotonic solutions containing potassium, eg. compound sodium lactate infusion (Ringer-Lactate solution) or half-strength Darrow’s solution in 2.5% glucose infusion (see also Dehydration, p332)
If there is blood loss and the patient is not in shock:
Use sodium chloride 0.9% infusion for blood volume replacement giving 0.5-1L in the 1st hour and not more than 2-3L in 4 hours
If there is blood loss >1L:
Give 1-2 units of blood to replace volume and concentration (see also p144)
In severe burns:
See p125 for calculation of IV fluid requirements and details of rehydration regimes
In patients undergoing aspiration of fluid in the non-functioning compartments: eg. in ascites, pleural effusion and chronically distended urinary bladder
• intravascular fluid redistribution will lead to a fall in BP
Give isotonic solutions to correct this: eg. sodium chloride 0.9% infusion or compound sodium lactate infusion (Ringer-Lactate solution)
In patients with shock:
Give compound sodium lactate infusion (Ringer-Lactate solution) or sodium chloride 0.9% infusion 20mL/kg IV over 60 mins for initial volume resuscitation
- start rapidly, closely monitor BP
- reduce the rate according to BP response
In patients with severe shock and significant haemorrhage:
Give a blood transfusion (see p144)
