Nutrition and metabolic
disorders
1 Acid-base imbalance
1.1 Metabolic acidosis
ALKALISING DRUGS
Trometamol
(Tris(hydroxymethyl)aminomethane, THAM)
lINDICATIONS AND DOSE
Metabolic acidosis
▶BY INTRAVENOUS INFUSION
▶Child:To be administered at an amount appropriate to
the body base deficitlUNLICENSED USEUnlicensed preparation.
lCONTRA-INDICATIONSAnuria.chronic respiratory acidosis
lCAUTIONSExtravasation can cause severe tissue damage
lSIDE-EFFECTSHepatic necrosis (following administration
via umbilical vein, in neonates).hyperkalaemia (in renal
impairment).hypoglycaemia.respiratory depression
SIDE-EFFECTS, FURTHER INFORMATIONRespiratory support
may be required because trometamol induces respiratory
depression.
lPREGNANCYLimited information available,
hypoglycaemia may harm fetus.
lBREAST FEEDINGNo information available.
lRENAL IMPAIRMENTUse with caution, may cause
hyperkalaemia.
lMEDICINAL FORMS
There can be variation in the licensing of different medicines
containing the same drug. Forms available from special-order
manufacturers include: solution for infusion
Solution for infusion
▶Trometamol (Non-proprietary)
Trometamol 363.4 mg per 1 mlTris 36. 34 % solution for infusion
20 ml ampoules| 10 ampoulePs
2 Fluid and electrolyte
imbalances
Fluids and electrolytes
Electrolyte replacement therapy
The electrolyte concentrations (intravenousfluid) table and
the electrolyte content (gastro-inestinal secretions) table
may be helpful in planning replacement electrolyte therapy;
faeces, vomit, or aspiration should be saved and analysed
where possible if abnormal losses are suspected.
Oral preparations for fluid and electrolyte
imbalance
Sodium and potassium salts, may be given by mouth to
prevent deficiencies or to treat established deficiencies of
mild or moderate degree.
Oral potassium
Compensation for potassium loss is especially necessary:
.in children in whom secondary hyperaldosteronism
occurs, e.g. renal artery stenosis, renal tubule disorder, the
nephrotic syndrome, and severe heart failure;
.in children with excessive losses of potassium in the
faeces, e.g. chronic diarrhoea associated with intestinal
malabsorption or laxative abuse;
.in those taking digoxin or anti-arrhythmic drugs, where
potassium depletion may induce arrhythmias.
Measures to compensate for potassium loss may be required
during long-term administration of drugs known to induce
potassium loss (e.g. corticosteroids). Potassium supplements
areseldom requiredwith the small doses of diuretics given
to treat hypertension;potassium-sparing diuretics(rather
than potassium supplements) are recommended for
prevention of hypokalaemia due to diuretics such as
furosemide or the thiazides when these are given to
eliminate oedema.
If potassium salts are used for theprevention of
hypokalaemia, then doses of potassium chloride p. 601 daily
by mouth are suitable in patients taking a normal diet.
Smaller doses must be used if there is renal insufficiency to
reduce the risk ofhyperkalaemia.
Potassium salts cause nausea and vomiting and poor
compliance is a major limitation to their effectiveness (small
divided doses may minimise gastric irritation); when
appropriate, potassium-sparing diuretics are preferable.
When there isestablished potassium depletionlarger doses
may be necessary, the quantity depending on the severity of
any continuing potassium loss (monitoring of plasma-
potassium concentration and specialist advice would be
required). Potassium depletion is frequently associated with
chloride depletion and with metabolic alkalosis, and these
disorders require correction.
Management of hyperkalaemia
Acute severe hyperkalaemiacalls for urgent treatment with
intravenous infusion ofsoluble insulin
( 0. 3 – 0. 6 units/kg/hour in neonates and
0. 05 – 0. 2 units/kg/hour in children over 1 month) with
glucose 0. 5 – 1 g/kg/hour ( 5 – 10 mL/kg of glucose 10 %;
2. 5 – 5 mL/kg of glucose 20 % via a central venous catheter
may also be considered). If insulin cannot be used,
salbutamol p. 156 can be given by intravenous injection, but
it has a slower onset of action and may be less effective for
reducing plasma-potassium concentration.
Calcium gluconate p. 594 is given by slow intravenous
injection to manage cardiac excitability caused by
hyperkalaemia.
The correction of causal or compounding acidosis with
sodium bicarbonate infusion p. 586 should be considered
(important: preparations of sodium bicarbonate and
calcium salts should not be administered in the same line—
risk of precipitation). Intravenous furosemide can also be
given but is less effective in children with renal impairment.
Drugs exacerbating hyperkalaemia should be reviewed and
stopped as appropriate; dialysis may occasionally be
required.
Ion-exchange resinsmay be used to remove excess
potassium inmild hyperkalaemiaor inmoderate
hyperkalaemiawhen there are no ECG changes. Calcium
polystyrene sulfonate is preferred unless plasma-calcium
concentrations are high.Oral sodium and water
Sodium chloride p. 589 is indicated in states of sodium
depletion. In preterm neonates in thefirst few weeks of life
and in chronic conditions associated with mild or moderate
degrees of sodium depletion, e.g. in salt-losing bowel or
renal disease, oral supplements of sodium chloride may be
sufficient. Sodium chloride solutions suitable for use by
mouth in neonates are available from‘special-order’
manufacturers or specialist importing companies, they
should be used with care because they are hypertonic.
Supplementation with sodium chloride may be required toBNFC 2018 – 2019 Fluid and electrolyte imbalances 583
Blood and nutrition9