27. PAEDIATRIC ANAESTHETIC EQUIPMENT

Paediatric patients can deteriorate rapidly during anaesthesia. The anaesthetist must check and prepare all equipment and drugs before starting the anaesthetic. They should have a plan for the anaesthetic and be prepared for complications.

Paediatric Airway Equipment

Paediatric breathing equipment must have a small deadspace and low resistance to breathing.

Laryngeal masks are available in a number of sizes. They are useful in paediatric anaesthesia.

Low deadspace face masks are generally used (Rendell-Baker). A clear mask allows the anaesthetist to check the child’s colour during anaesthesia.

There are a number of different breathing systems suitable for use in paediatric anaesthesia. The Mapleson E (Ayres’ T piece) is valveless, low resistance, simple and lightweight. It has a small dead space. The volume of the expiratory limb should be greater than the patient’s tidal volume. It is very suitable for children less than 20 kg. Fresh gas flows of 2 to 3 times minute volume should be used to prevent re-breathing during spontaneous ventilation or a minimum of 6 litres/min. For controlled ventilation a flow rate of 1000 ml + 100 ml/kg should prevent re-breathing.

For children above 20 kg, adult breathing systems are suitable for both spontaneous and controlled ventilation. A circle breathing system can be used safely for controlled ventilation in children heavier than 10 kg if the deadspace is reduced by using smaller tubing, Y piece and connectors.

Many adult ventilators cannot be safely used for paediatric patients. They cannot reliably deliver the small tidal volumes and rapid respiratory rates required.

Laryngoscopes are available in a wide range of sizes. In babies a straight blade or one with only a slight curve at the tip may be easier to use.

Endotracheal tubes should be uncuffed. The size may be estimated by age/4 + 4. There should always be an endotracheal tube one size larger and smaller available.

Intravenous Cannula

The intravenous cannula may be easier to insert if they are first flushed with normal saline. This makes the “flash back” of blood more obvious. Intravenous cannula must be carefully taped. The anaesthetist may wish to immobilise the limb, by gently wrapping it to a board, to prevent the cannula from being removed.

The anaesthetist should use a paediatric intravenous line (60 drops/ml) if available. Lines should have a burette filled with only the amount of fluid the anaesthetist wishes to give. If a burette is not available the anaesthetist must take care not to give too much intravenous fluid.

Drugs

The correct dose of drugs should be calculated and only that dose should be drawn up. Having the full adult dose of a drug in a syringe could lead to a large overdose. All syringes must be labelled. If the anaesthetist wishes to have emergency drugs (e.g. suxamethonium, atropine) ready, these syringes should be carefully labelled and stored away from the other anaesthetic drugs. A different colour label (red) makes the emergency drugs easier to identify.

Monitoring

Standard monitoring includes close, continuous observation by the anaesthetist.

A precordial or oesophageal stethoscope can be used to assess breath sounds, heart rate, rhythm and the intensity of heart sounds. The precordial stethoscope should be firmly taped on the chest wall over the apex of the heart.

Accurate blood pressure measurement requires the correct size cuff. The cuff should cover at least two thirds of the upper arm and the inflatable bag should almost encircle the arm. If the cuff is too small, a reading that is falsely high may be obtained. If the cuff is too large the reading may be falsely low.

Temperature monitoring is very important in children. The operating theatre should be heated. The patient should be kept covered as much as possible. Children have a relatively larger head and will lose more heat from their head than adults.

Urine output should be at least 0.5 ml/kg/h.

More advanced monitors increase safety. These include pulse oximetry, end tidal carbon dioxide, ECG and intra-arterial and central venous pressure monitoring.

Acknowledgment

I would like to thank Dr. Robert MacDougall and Dr. Ken Brownhill from the Royal Children’s Hospital, Victoria, Australia for their advice and guidance on paediatric anaesthesia.