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28 Fluids and Electrolyte Therapy in the Paediatric Surgical Patient
Postoperative Fluid Management Hyperkalaemia
In the neonate, postoperative hypothermia is frequently an issue that • Causes: bruising, haemolysis, renal failure, hypoglycaemia, tissue
will affect the recovery time as well as the ability to use fluids that hypoxia and poor peripheral perfusion, haemolysed blood sample,
are not warm because this may further decrease the body temperature. and inappropriate potassium supplementation.
A clinical note: The cold betadine that is used for surgical procedures
can prompt hypothermia because the patient can be soaking in the fluid • Exacerbating factors: hypocalcaemia, hyponatraimia, and acidosis.
left over from the initial prep during the length of the procedure. If this • Treatment required for serum potassium levels >7.0 mmol/l:
sterilisation agent is not removed from the skin of a newborn after the - 7.0–8.0 mmol/l without ECG changes: remove potassium
surgery, the patient can develop a chemical burn that can add to the source and give calcium resonium 0.5–1 g/kg in divided doses
patient’s perioperative morbidity. per rectum or orally.
Electrolytes, glucose, and haemoglobin levels, as well as the
documentation of good urine output should be determined within the - >8.0 mmol/l and/or ECG changes (depressed P waves,
first few hours after surgery. The normal urine output of >0.5 ml/kg/ peaked T waves, wide QRS complexes): emergency treatment
hr should be measured to help guide the fluid status; at times, a small required.
feeding tube placed in the bladder may be the only method available - Emergency treatment for hyperkalaemia:
to measure urine output accurately. The immaturity of the renal system 1. Remove source of potassium.
needs to be considered with the intraoperative fluid shifts, which may 2. 10% calcium gluconate: 1.0 ml/kg lV (dilute 50:50, give
not promote a diuresis, as expected in older patients. The use of radiant over at least 2 minutes). This has a transient effect on
warmers will help with the hypothermia but also add to insensible fluid electrocardiogram (ECG), not on K+ concentration.
losses; therefore, removal of these warmers will need to be considered
once the temperature returns to a more normal level. 3. Salbutamol: 4 μg/kg over 10 minutes.
Nausea and vomiting can be seen in the paediatric postoperative 4. NaHCO : can be tried, especially if acidotic. Dose is 2
3
patient, but usually this is not an issue in a newborn. Third spacing mmol/kg (= 4 ml/kg 4.2% NaHCO3) at 1–2 mmol per
from the surgical procedure (i.e., loss of fluid from an open abdomen minute.
during surgery) is an ongoing issue in the immediate postoperative 5. Glucose: 0.5 g/kg per dose: 5 ml/kg of 10% dextrose or 2
period, which may influence the overall fluid replacement in this ml/kg of 25% dextrose or 1 ml/kg of 50% dextrose, over
period. The opportunity for the newborn to resume breast milk intake 15–30 minutes.
will be dictated by the surgical procedure and the surgeon’s preference. 6. Insulin: 0.2 unit per gram of glucose, 1.0 unit/kg insulin
Successful surgery in the newborn period is one in which the patient is with 4ml/kg 25% dextrose over 30 minutes.
reunited with the parents so that normal bonding can resume and the
patient can quickly return to the family home or village. Hypokalaemia
Summary of Fluid and Electrolyte Balance • Serum potassium: <3.0 mmol/l.
Fluid Balance • Causes: inadequate intake, intestinal obstruction, vomiting, diarrhoea,
diuretics, polyuric renal failure, and alkalosis.
• Normal maintenance fluid: Ringer’s lactate at rates shown in Table 5.3.
• Presentation: cardiac arrythmias, paralytic ileus, urinary retention,
• Resuscitation fluid: 20–30ml/kg bolus using normal saline.
and respiratory distress.
• Preoperative dehydration caused by: vomiting, bowel obstruction, • Treatment: by supplementation.
overheating, acute burns, intestinal perforation, myelomeningocele
(open), open wounds, abdominal wall defects, and trauma. Acid–Base Balance
• Overhydration: may be iatrogenic. • Normal: pH is 7.4 and bicarbonate is 25 mmol/l.
• Fluid imbalance assessment: see Table 5.6. • Metabolic acidosis causes: asphyxia, tissue ischaemia, acute renal
failure, diarrhoea, dehydration, and stoma losses. Treat cause and
Sodium Balance bicarbonate infusion is rarely used.
• Normal sodium requirement: 2–4 mmol/kg per day.
• Metabolic alkalosis causes: vomiting, pyloric stenosis, and upper
• Normal serum sodium: 135–140 mmol/l. gastrointestinal obstruction. Correction by fluid, sodium, and potas-
sium replacement.
• Causes of hyponatraemia: iatrogenic with hypotonic solutions, labo-
ratory error, polyuric renal failure, diuretic treatment, congestive Glucose Balance
cardiac failure, Addison’s disease, and maternal hyponatraemia. • Normal serum levels: 2.5–7.0 mmol/l.
• Signs of hyponatraemia: failure to thrive, seizures, and cerebral oedema. • Hypoglycaemia: <2–2.5 mmol/l.
• Causes of hypernatraemia: iatrogenic infusion, laboratory error, • Hypoglycaemia presents with: apnoea, lethargy, seizures, and coma.
dehydration, and maternal hypernatraemia.
• Hypoglycaemia is caused by: poor intake, vomiting, hypother-
• Signs of hypernatraemia: dehydration and seizures. mia, sepsis, and Beckwith-Wiedemann syndrome associated
• Treatment of sodium imbalance: by appropriate usage and adjustment with exomphalos.
of fluid therapy. • Hypoglycaemia treatment includes: feeding or bolus of 10% dex-
Potassium Balance trose by intravenous infusion (IVI).
• An intracellular ion with a normal requirement of 1–3 mmol/kg per day. • Hyperglycaemia: >14mmol/l.
• Normal serum potassium: 3.5–5.5 mml/l. • Hyperglycaemia is caused by: excess infusion, and should be low-
ered with less concentrated dextrose solution (5%).