Posterior Spinal Fusion Protocol
(Scoliosis Surgery)

James Flowerdew, January 2009


PATIENT POPULATION
PRE-OP
INDUCTION
& MONITORING
INTR
A-OP MANAGEMENT
EMERGENCE
& TRANSPORT
PATIENT POPULATION:  The majority of these patients tend to be relatively healthy ASA I-II adolescents (mostly female).  However, we are starting to see an increase in the number of more complicated patients such as spastic cerebral palsy with or without other congenital conditions.  The operative course as well as the post-operative management tends to differ between these two groups and perioperative planning needs to take into consideration these differences.  Historically, we have done 20 pediatric cases per year, but the surgeons have expressed interest in increasing their volume.

 

PRE-OP:  Most of these patients are seen day of surgery.  At 70o curvature patients start to manifest objective restrictive pulmonary disease during function testing, however, they are usually asymptomatic.  When curvature approaches 110o patients can have significant restrictive function and start to become symptomatic.  Acute pulmonary problems such as asthma exacerbations or respiratory tract infection warrant postponement of surgery (regardless of overall health and deformity). 
The need for intraoperative wake-up test should be discussed with surgeon prior to start of case.  If a wake-up test is to be done, the patient (and family) should be informed about such test and the very unlikely chance of recall during this time.  The patient will probably require reassurance that the wake up is very brief, they will be comfortable, and they will quickly be put back to sleep.

  • Labs — CBC, Coags, Type and Cross (2 units of PRBC should be available), any disease specific testing as required.
  • Testing — PFTs if curvature > 70o, cardiac evaluation if known CHD, metabolic disorders, or muscular dystrophies.
  • Pre-medication — Per anesthesia provider

INDUCTION:  Induction agents and route per individual provider.  OR should be warmed prior to entering.  Antibiotics per surgeon.

  • Monitoring — Standard ASA monitoring including temperature and urine output.  Somatosensory evoked potentials (SSEP) and Motor evoked potentials (MEP) are becoming standard of care at many centers and are being used on most cases at MMC.
  • IV access — Minimum 2 peripheral IVs, one large bore (18g min, preferably 16g)
  • Lines — Arterial line is required.  Central venous line is not required on healthy adolescents with good access.  If difficult IV access or the patient has significant developmental or behavioral issues, central venous line is recommended (helps with post operative management).  Direct visualization using ultrasound is strongly recommended when placing central lines (we have had several difficult line placements recently).  There is a SiteRite ultrasound machine and sterile sleeves/ultrasound gel available from the equipment room outside of OR room 4.  A Bair Hugger should be used during line placement — an upper body Bair blanket can be used as a full body blanket for line placement and then reused as an upper body blanket for the case.
  • Positioning — Jackson table with arms abducted/flexed above head is the usual positioning.  ProneView head rest and mirror recommended (if appropriate fit) with careful attention to pressure points, particularly eyes.  Great care should be taken to examine any pressure points (ECG leads, cables, IV connectors, etc.) and padded appropriately.

 

INTRA-OP MANAGEMENT:  These cases take 6-10 hours depending on complexity and number of levels covered.  Blood loss can be extensive (greater than 1 blood volume) and actual loss difficult to calculate.  Cell saver is routinely used.  Blood product transfusions are common.  An intraoperative wake-up test is frequently requested even when SSEP and MEP are used.  The surgeons will normally give adequate warning (30 min) as to when they desire the wake-up test.  Wake-up tests are not usually requested on kids who are unlikely to be able to easily follow commands. 

  • Maintenance — Multiple strategies and techniques may be used to maintain general anesthesia.  Aside from providing adequate depth of anesthesia, conditions should be such that SSEP and MEP monitoring is optimal and a wake-up test easily accommodated if requested.  After intubation muscle relaxation should be avoided.  N2O should also be avoided as it completely wipes out MEP.  Inhalations agents (Isoflurane and Sevoflurane) have a progressive deleterious effect on SSEP and MEP as concentrations rise above 0.5 MAC.  Narcotics, midazolam, and propofol have little effect on SSEP and MEP monitoring.  Recommended maintenance anesthesia (unless contraindicated):
    • Remifentanil gtt — 0.1-0.4 mcg/kg/min
    • Propofol gtt — 90-150 mcg/kg/min
    • Isoflurane — 0.3-0.4%

The above anesthetic generally provides a very smooth and stable hemodynamic course with a mild degree of induced hypotension (MAP 60-65mmHg).  In order to facilitate the wake-up test, the propofol and isoflurane are turned off approximately 10 minutes prior to test.  Remifentanil can be reduced to 0.05-0.03 mcg/kg/min approximately 5 minutes prior to test and result in adequate conditions for wake up test.

  • Bleeding/Coagulopathy — Blood volume should be calculated for each patient.  Blood gases are recommended every 2 hours, more frequently if clinical concerns warrant such.  When blood loss approaches 50% of blood volume a STAT cardiac coagulation panel should be sent.  If surgical field conditions demonstrate any evidence of impaired coagulation, the cardiac coagulation panel should be sent earlier.  Patients with spastic cerebral palsy or other congenital disorders may display a higher propensity to develop coagulopathies as will patients who are hypothermic.  The use of cell saver is effective at partially restoring red blood loss, however, factors and platelets are not restored with the cell saver transfusion.  In the setting of heavy cell saver transfusion (i.e. blood loss) the patient is at risk for developing a coagulopathic state from depletion of factors and platelets compounded by a volume resuscitation dilutional effects. 
    Several ongoing studies are looking at the use of tranexamic acid (not available at MMC at present) or aminocaproic acid (Amicar) to help reduce blood loss.  Rainbow Babies and Childrens Hospital has been using Amicar for the past 10 years and has published 5 studies that demonstrate decreased blood loss and transfusion rates for idiopathic scoliosis repairs without any complications related to Amicar.  Unless contraindicated (active DIC, thrombosis, PE, bradycardia) we should plan on using Amicar for these cases.  Dose as follows:
    • Epsilon aminocaproic acid (Amicar) 100mg/kg (5g max) loading dose over 15 min, followed by 10mg/kg/hr infusion (page CVAT for assistance).

 

EMERGENCE:  Most of these patients should be able to be extubated in OR.  All pediatric scoliosis cases are booked with post-operative SCU beds regardless of airway status.  Consideration should be given to the potential for significant facial and upper airway edema. 

  • Antiemetics — All these patients should receive dexamethasone and zofran unless contraindicated.
  • Pain Management
    • EPIDURAL - The surgeons typically will place an epidural catheter intraop. Several studies have shown that placing 2 epidural catheters (thoracic and lumbar) provides better relief when compared to a single catheter and has significantly less side effects when compared to narcotic based techniques.  We have used 2 catheters at MMC on extensive repairs with good results. 
      • SINGLE CATHETER - Bolus with bupivacaine 0.25% (0.3mg/kg up to max 15mg) prior to emergence and follow with infusion of bupivacaine 0.125% (0.4mg/kg/hr up to max of 15mg/hr).   
      • DOUBLE CATHETER — Total bupivacaine bolus dose (bupivacaine 0.25% 0.3mg/kg up to max of 15mg) and infusion rates (bupivacaine 0.125% at 0.4mg/kg/hr up to max of 15mg/hr) are the same as single catheter, but divided , half in the thoracic catheter and half in the lumbar catheter. 
    • Narcotics - If Remifentanil is used there is an increased risk of hyperalgesia.  Giving morphine 100mcg/kg over the last 30 minutes of the case helps decrease the incidence.  Patients may require an additional 100mcg/kg in 5-10 minutes after the Remifentanil has been turned off.  Morphine PCA combined with an epideral is usually effective at controlling pain postoperatively.  In the kids who are unable to use a PCA, morphine infusions 20-30mcg/kg/hr with nursing administered morphine boluses 50mcg/kg q2-3hrs is often effective.  Postoperative pain control needs to be coordinated with the accepting SCU team.
  • Transport — Transport to SCU with usual monitors and supplemental oxygen.