I2i / 23B18: Compare and contrast the pharmacology of Hartmann’s solution and 0.9% saline?

23B18: Exam Report

Compare and contrast the pharmacology of Hartmann’s solution and 0.9% saline?

17% of candidates passed this question.

This question asked for a comprehensive description of the components and chemical properties of each solution (including pH and calculated and measured osmolarity).

A mechanistic description of the different acid base effects was expected. Marks were also allocated for the advantages and disadvantages of each fluid (for example the calcium in Hartmann’s risks causing precipitation when mixed with certain drugs and blood products).

Lastly, it was expected that answers would provide situations where one fluid might be preferred over the other (for example saline to treat dehydration and metabolic alkalosis secondary to gastric losses – as in a pyloric obstruction). Descriptions of the physiological handling of each fluid after bolus or infusion was not required.

I2i / 23B18: Compare and contrast the pharmacology of Hartmann’s solution and 0.9% saline?

Hartmann’s solution

0.9% Saline

Type of fluid

Hartmann’s solution

Balanced crystalloid

0.9% Saline

Isotonic crystalloid

Storage

Hartmann’s solution

At or below 25°C

0.9% Saline

At or below 25°C

Shelf life

Hartmann’s solution

3 years

0.9% Saline

2 years

Constituents (mmol/L)

Hartmann’s solution

0.9% Saline

Na2+

Hartmann’s solution

131

0.9% Saline

154

Cl-

Hartmann’s solution

111

0.9% Saline

154

K+

Hartmann’s solution

5.4

0.9% Saline

–

Ca2+

Hartmann’s solution

2.0

0.9% Saline

–

Lactate

Hartmann’s solution

29

0.9% Saline

–

Hartmann’s solution

0.9% Saline

pH

Hartmann’s solution

7.0

0.9% Saline

5.5

Calculated osmolarity (mOsmol/L)

Hartmann’s solution

280

0.9% Saline

308

Measured osmolarity (mOsmol/L)

Hartmann’s solution

254

0.9% Saline

286

Acid-base effects

Hartmann’s solution

  • Buffered salt solution – chloride replaced with other anions to reduce Chloride load
  • Lactate is metabolised via the citric acid cycle
    • Utilises an H+ ion and produces CO2 (which is liberated via lungs)
    • Reduces whole body pH
  • PVC packaging can lead to formation of HCl

0.9% Saline

  • CO2 solubility is slightly less in saline than in water
  • The presence of electrolytes in solution favours dissociation of carbonic acid
  • PVC packaging can lead to formation of HCl
  • Dilutional effects – HCO3 buffering in vivo is dilated by infusion, but the acid (CO2) remains constant and unaffected by dilution – this causes dilutional acidaemia

Advantages

Hartmann’s solution

  • Chemical composition close to ECF
  • Isotonic
  • Balanced

0.9% Saline

  • Cheap
  • Readily available
  • Familiar

Disadvantages

Hartmann’s solution

  • Contains lactate (should be able to be metabolised by most)
  • Some drugs are not compatible with Hartmann’s
    • Calcium can cause precipitation with blood products/some drugs (e.g. ceftriaxone)
  • Contraindicated in concomitant administration of ceftriaxone in neonates (<28 days)
  • Can cause hyperkalaemia or hypercalcaemia to vulnerable patients (renal failure, granulomatous disease, sarcoidosis)

0.9% Saline

  • Dose dependent hyperchloraemic metabolic acidosis
  • High Cl- load associated w/ AKI
    • Induces afferent arteriole vasoconstriction
  • Hypotension
  • Coagulopathy
  • Can cause large Na shifts (esp if hyponatraemic) – risk of ODS, worsening ascites in hepatic failure, worsening oedema in renal/cardiac failure

Preferred uses

Hartmann’s solution

  • General resuscitation fluid
  • General maintenance fluid

0.9% Saline

  • Fluid of choice in TBI
  • First line resuscitation fluid in patient who are hypovolaemic 2o to UGI fluid losses resulting in hypochloraemic metabolic alkalosis
  • Traditional fluid of choice for DKA fluid resuscitation
  • May be used for slow sodium correction of hypovolaemic hyponatraemia
  • Carrier for many drugs utilised in ICU

Author: Erin Maylin