DEPARTMENT OF PAEDIATRIC ANAESTHESIA
WOMEN’S AND CHILDREN’S HOSPITAL

GUIDELINE FOR ANAESTHESIA FOR SCOLIOSIS SURGERY

1 Definition:

Surgery for the treatment of scoliosis

2 types:

• idiopathic

• secondary

  • Commonly associated with muscular dystrophy (Duchenne’s) spina bifida and Marfan’s syndrome

  • Less commonly, other congenital or acquired spinal lesions

2 Anaesthetic problems:

• Prolonged anaesthesia
• Prone patient
• Spinal cord monitoring
• Wake-up test is not routinely performed here
• Major blood loss and transfusion
• Pain management
• Associated congenital/acquired malformations e.g. restrictive lung disease

3 Assessment of patient:

• Check for problems associated with congenital/acquired lesions
• Availability of blood - autologous vs homologous. Autologous arranged by surgeons. Patients receive erythropoietin and iron if donating blood pre-op
• Discussion of wake-up test if planned
• PFTs/ ECG +/- cardiology report only if clinically indicated e.g. muscular dystrophy, Marfan's syndrome
• Hb usually estimated with last autologous blood donation
• Consider autologous blood collection at induction of anaesthesia (if Hb > 100g/l on testing within 1 week pre-op)
• Discuss post-op pain relief including PCA

4 Preparation of patient:

Premedication: benzodiazepine +/- topical local anaesthetic to hands

5 Preparation of theatre:

Increase ambient theatre temperature
Additional equipment according to protocol
Hot air warmer from time of induction

6 Induction of Anaesthesia:

Standard induction, usually intravenous but can be gaseous if patient prefers

Paralyse with vecuronium 0.1mg/kg
Oral intubation with age-specific tube

Eye care: taped shut plus eye pads 

Cannulae 16-18g cannula right forearm
20-22g arterial line right radial artery
20g Arrow central venous line via Right Internal Jugular vein

Collect 1 or 2 units of blood from arterial line for acute normovolaemic haemodilution if indicated (see below)

Urinary catheter

Positioning Prone on specific frame with surgical assistance, head on foam head block. Head usually towards patient's right side. Hot air warmer blanket over patient's legs and taped over buttocks.

Transducers adjacent to patient's right arm (therefore aim for right radial cannula). Spinal cord monitoring machine will be adjacent to patient's left arm. Keep anaesthesia pumps and transducers away from this monitor.

7 Maintenance:

IPPV with AIR/O2 /isoflurane to max ETiso 0.6 combined with a high dose remifentanil infusion.

No more muscle relaxants (motor spinal cord monitoring during procedure). Muscle relaxants may be necessary for anterior approach but will preclude motor monitoring. If no spinal monitoring is planned, higher concentrations of volatile may be used.

Analgesia:

• Fentanyl 2mcg/kg at induction.

• Remifentanil infusion, typically about 0.5 micrograms/kg/min but sometimes higher (turn off at end of surgery).

• Intrathecal morphine 100 -150 mcg administered by surgeon prior to wound closure.

• Ketamine loading dose 0.3-0.5 mg/kg followed by infusion about 0.1 mg/kg/hr (usually 200mg in 50 mls run at 1mL/hr).

• Intravenous morphine increments before waking up, usually about 0.1 milligrams/kg but often further morphine required on arrival in PICU.

• Paracetamol IV 20mg/kg about 1 hour before the end of surgery.

Anti-emesis prophylaxis: dexamethasone 0.15mg/kg at start of surgery plus tropisetron 0.1 mg/kg (max 2mg) near end of surgery

Antibiotic cover: cephazolin 25mg/kg i.v.

Monitoring ECG, arterial BP, CVP, pulse oximetry, capnography, FIO2, Anaesthetic agent, oesophageal stethoscope and temperature probe.

Special techniques:

• Controlled hypotension to mean BP 55-60mmHg induced with remifentanil infusion (GTN infusion may rarely be necessary).

• Acute normovolaemic haemodilution. Aim to take 10-15 ml/kg depending on pre-op haemoglobin. Blood usually taken from the arterial line and replaced via peripheral line with Hartmann's solution. Blood taken to be transfused back into patient within four hours and always before leaving theatre.

• Spinal Cord monitoring (+/- wake-up test). A good summary of spinal cord monitoring can be found on the Neurology Intranet site.

• Haemacue monitoring for estimating blood loss/haemodilution. Surgical swabs and packs are weighed to assist in estimating blood loss.

• Antifibrinolytics. For all patients having posterior approach with more than 8 levels and patients with other disorders likely to increase bleeding (eg muscular dystrophy) and with no contraindications. Tranexamic acid 100mg/kg over 15 minutes and then an infusion of 10 mg/kg/hr for the duration of surgery. This agent's use is restricted to the regular scoliosis surgery anaesthetic consultants and patient consent for its use obtained.

8 Homeostasis:

Intravenous fluids

Hartmann’s solution initially via 16g cannula.

N saline via 22g cannula to flush drugs.

Blood transfusion as indicated by Hb (transfuse trigger is known Hb < 80gm/L) and  to maintain CVP at baseline established once patient turned prone. Blood taken for normovolaemic haemodilution alwys returned regardless of Hb level.

Temperature maintenance: blood warmer, humidvent or humidifier as indicated  hot air blower (placed between blankets) over legs from start of induction.

9 Emergence:

Aim to extubate in theatre.

10 Recovery:

Direct transfer to Paediatric Intensive Care for overnight monitoring. Some more minor corrections may go to the surgical ward post-op and these patients will spend time in Recovery Ward in the normal way.

11 Post-operative management:

Oxygen until awake and stable.

Intravenous fluids/blood transfusion as indicated by monitoring and Hb levels.

Usually determined by PICU staff.

Analgesia

Regular paracetamol QID intravenously for at least the first 24 hours, change to oral when tolerated.

Morphine PCA. No background for first 15 to 20 if intrathecal morphine has been given in theatre. Morphine infusion with nurse initiated boluses if PCA unsuitable.

Ketamine infusion 0.1-0.2 mg/kg/hr continued until PCA ceased (no boluses).

Transition to oral opioids. Wide individual variation but generally commence slow release MS Contin on day 2 but keep PCA as bolus only until Day 3. Commence breakthrough oral opioid (usually oxycodone) when ceasing PCA.

Tramadol and/or clonidine may be added at any stage post-operatively if pain is difficult to control or if opioid side effects are a problem.

Discharged home on MS Contin and prn oxycodone with weaning schedule individualised by Acute Pain Team.

Regular aperients.

Regular tropisetron for first 48 hours then PRN.

Droperidol PRN as second line anti-emetic .

Last Update: Scoliosis Surgery Anaesthetists, May 2007