anesthesia for spinal cord injury and scoliosis030
TRANSCRIPT
Anesthesia for Spinal cord injury and scoliosisAtef Kamel MD
Background Anatomy & PhysiologyPathophysiologyPharmacologyAnesthetic Technique & ManagementManagement of ComplicationsCase Study
Anatomy & Physiology
Anatomy and physiol
Blood Flow to the Spinal Cord
Anterior Spinal Artery (1) Anterior 2/3 of spinal cord
Posterior Spinal Arteries (2) posterior 1/3 of spinal cord
These 3 arteries depend on a network of collateral vessels to provide adequate blood supply to the spinal cord.
Artery of Adamkiewicz arteria radicularis magna
Largest most consistent radicular artery
Located in the thoracolumbar region (T5-L3)
Supplies blood to the ASA (anterior 2/3 of cord)
Responsible for most of the spinal cord blood flow beneath its point of entry
If obstructed Anterior Artery Syndrome
Spinal Cord Blood Flow
Autoregulation determines the amount of blood flow to the sp cd.
Limits: 50-150 mmHg. Outside these limits pressure dependant.
Spinal cord blood flow increases when CO2 levels are high and decreases when CO2 levels are low. (similar to cerebral blood flow)
Injury to the spinal cord alters both autoregulation and CO2 responsiveness.
Pathophysiology
Spinal Cord Injury
Trauma Partial or Complete transection of the cord
Transections above C 3-5 = Diaphragmatic innervention
(ventilator required for survival)
Transections above T 1 = Quadraplegia
Transections above L4 = Paraplegia
Most Common C 5-7 & T 12 - L 1
(least protected / most mobile)
Acute Spinal Cord Injury
Spinal shock may begin within an hour after injury and last from several minutes to several months, after which reflex activity gradually returns:
Flacid paralysisComplete loss of reflex and sensory activity below
level of lesion.Loss of vasomotor tone, CV instability,
Hypotension, Bradycardia, Venous pooling. Paralytic ileus with distensionHypothermia
Scoliosis
Lateral curvature of the spine, usually accompanied by rotation.
Cobb angle is a method used to measure the curvature.
The greater the angle, the greater the progression and severity of complications.
Causes of Scoliosis
Neuromuscular Scoliosis - the result of muscle imbalance and lack of trunk control. (i.e. cerebral palsy, muscular dystrophy, or leg length discrepancy)
Congenital Scoliosis - the result of asymmetry of the vertebrae secondary to congenital anomalies. (i.e. hemivertebrae, failure of segmentation)
Idiopathic Scoliosis - no definite etiology. Diagnosis of exclusion. Most common type accounting for 80-85% of cases
Effects of scoliosis
Increased curvature =
narrowing of thoracic
cage, which leads to
abnormal CV and Pulm
function.
Increased curvature
causes increased co-
morbidities
Restrictive lung disease,
dyspnea on exertion,
pulmonary hypertension,
cor pulmonale and
alveolar hypoventilation.
Respiratory Abnormalities
Lung volumes reduced
Compliance decreased
Restrictive pattern
Abnormal V/Q
Shallow, rapid breathing
Alveolar hypoventilation
Hypoxemia
PROGRESSION OF RESPIRATORY DISEASE WITH INCREASING DEGREE OF SCOLIOSIS
< 10 normal
> 25 increased PA pressures
> 40 surgery considered
> 65 restrictive lung disease
> 100 exertional dyspnoea
> 120 alveolar hypoventilation
NEUROMUSCULAR SCOLIOSIS – severe respiratory dysfunction
weak resp musclesineffective cough, unable to clear secretionsincoordinate swallowing, impaired airway
defencesimpaired central resp driveexaggerated resp depressant effect of drugsimmobile, retain secretionsrecurrent chest infections
CARDIOVASCULAR ABNORMALITIES
Pulmonary Hypertension
Chronic hypoxia
Reduced flow through compressed
lung
Impaired development of pulm vasc
bed
Cor Pulmonale
Cardiac Failure
Other Cardiovascular Associations
Idiopathic scoliosis - mitral valve prolapse
Muscular dystrophy - cardiomyopathy,
arrhythmiasMyotonia - dysrhythmias,
conduction abnormalities, mvp
Pharmacology
Spinal Cord Injury & Succinylcholine
Succinylcholine- Induced Hyperkalemia. Safe to administer Succs within first 48 hours after
spinal cord injury. Avoid Succs in all spinal cord injuries after 48 hours
Epidural Steroid Injections
Methylprednisone 80 mg (smaller amounts in diabetics who may be at increased risk for formation of epidural abscess) is injected into epidural space close to the nerve root.
The addition of 3-4 mL of local anesthetic (lidocaine) to the injected solution produces analgesia, confirming proper drug placement
Epidural Steroid Injection
Epidural Steroid Injection (cont.)
Few pts get relief from repeated injections if first one was unsuccessful.
Relief can last from weeks to months - injections are repeated every 3-4 months.
Little risk of serious complications ; Aseptic meningitis and bacterial meningitis
Adrenal Suppression may occur but recovers in 1-3 months.
High Dose Steroid Therapy (methylprednisone)
Acute Spinal Cord Injury Severe spine disease undergoing major spinal surgery.
Recommendation = bolus dose of 30 mg/kg over 15 minutes, then 5.4 mg/kg/hr for 23 hrs, within 8 hours of injury.
If therapy is started 8 hours after injury, the duration of the methylprednisone therapy should be continued for 48 hours
Pitfalls = Immunosuppression,wound infections & GI bleeds.
Tricyclic Antidepressants
•Useful for chronic pain, producing
analgesic effect via inhibition of reuptake
of serotonin and norepinephrine.
•Other benefits include: normalization of
sleep patterns, reduction in anxiety and
depression.
Anticonvulsants
May have some efficacy in treatment of chronic pain syndromes
Chronic anticonvulsants lead to an increased resistance to non-depolarizing neuromuscular relaxants
Anesthetic Technique & Management
Management of Spinal Cord Injuries
Immediate management is critical.Improper handling can cause further
damage and loss of functioningAlways assume there is a spinal cord
injury until it is ruled outImmobilizePrevent flexion, rotation or extension
of neckAvoid twisting patient
Management cont’d
•Management is aimed at preventing
further injury and observing for
progression of neuro deficits
•Consists of emergency treatment
following an A-B-C-D-E sequence.
Airway Management
First priority.
Open airway with jaw-thrust maneuver.
Use bag-valve-mask device initially, if
necessary intubate.
High conc. of 02 will prevent bradycardia
or asystole for patients exhibiting signs
of neurogenic shock.
Breathing
Lesions above C5 level will cause partial to
complete diaphragmatic paralysis (diaphragm is
innervated at C3-5 levels).
Lesions at C5 and below will allow full
diaphragmatic movement, but intercostal muscles
(innervated at T1) and abdominal muscles
(innervated at T12) are affected.
Circulation
Cardiac output is affected by external
or internal hemorrhage and
neurogenic shock.
IV fluids
Blood transfusion
Vasopressors
Disability
Neurological Examination
Lateral C-Spine X-ray
CT scan
Search for other injuries: abdominal,
chest, …
Anesthesia Implications for Acute Spinal Cord Transection
In-line stabilization of neck. Consider fiberoptic
intubation, especially if cervical spine injury is
suspected.
Prepare for CV instability, position changes, mild
blood loss, ..
Guard against hypothermia.
Succinylcholine may be administered within the first
24 hrs of acute injury
Blood flow (maintain perfusion pressure, normal
CO2)
SSEP, MEP, wake up test
Anesthesia Implications for Chronic Spinal Cord Transection
Monitor for autonomic hyperreflexia. Have rapid-acting vasodilators available.
Bradycardia / absence of compensatory tachycardia (cardioaccelerators T1-4).
Use nondepolarizing muscle relaxants only.
Guard against hypothermia.
Position carefully (osteoporosis).
Autonomic Hyperreflexia
Sympathetic system reflex response below the level of a spinal cord transection.
At T5 or above.
After the resolution of spinal shock.
Triggers : stimulation below the level of injury.
Autonomic hyperreflexia
S/S = HTN, reflex bradycardia, seizure, SAH, PE, VD/ flushing above transection & VC/ pallor below transection.
Treatment: Remove noxious stimulus, Raise head of bed, Administer rapid-acting vasodilator drugs.
Anesthesia for scoliosis
Pre-operative Evaluation
History & examination - type of scoliosis, assoc.
problems ( neuromuscular, airway, GIT, MH, latex
allergy), resp and cardiac
CXR , ECG, Blood tests
Spine Xray – severity & location
Echo
Lung Function Testing (if severe deformity)
Lung volumes (>40% reduction ~ post-op complics)
Flow volume loop
ABG
Preoperative preparation
Clear chest infection .
Wake up test explaining.
Posibility of post operative mechanical
ventilation
Premedication: atropine?
Heavy sedation should be avoided in
severe scoliosis.?
Anesthetic Problems associated with Scoliosis Surgery
Problems related to the patient:
Respiratory , cardiovascular
neuromuscular abnormalities or
syndromes.
Problems related to the surgery
Prone positionBlood loss and third space loss:
solution?Lengthy operationPreservation and monitoring of
spinal cord function.Heat loss.??Postoperative visual loss.
Monitoring
Routine monitors: oximeter, ECG, capnography, esophageal stethoscope and core body temp
Arterial catheter to monitor beat to beat changes.
CVPUrinary catheter Blood loss and replacement are
monitored.Patient’s position
Induction of anesthesia
Two large IV lines
Suxamethonium. is avoided in paralyzed
patients or neuromuscular etiology.
Intermediate non depolarizing ms.
relaxent like Atracurium or Rcuronium
is used for intubation and maintenance
of relaxation.
Prone position
Prone position
Maintain alignment of head / neck, support head in neutral position w/ pillow or head holding device.
Avoid hyperextension of arms by tucking them against the body or extending them <90 degrees alongside the head on armboards
Compression stockings to avoid the pooling of blood.
Frequently examine eyes, ears, chin, nose, shoulders, breasts, and genitalia for areas of pressure.
Spinal Cord Protection
Methylprednisolone
Reestablish normotension, normooxia and normocarbia to avoid
secondary insult.
Instruct surgeon to decrease traction on spinal cord.
Monitoring of the spinal cord: wake up test, SSEP and MEPs
Post Op Visual Loss -POVL
Unkown Cause, may hypoperfusion +edema +stretching of the optic nerve.
Long prone casesLarge amounts of IV
fluid.
Risk Factors: Hypotension Anemia Glaucoma Preventative measures: Keep IV fluid to reasonable
level HCT > 27 MAP >70 mmHg Avoid pressure on globe
SPINAL CORD MONITORING
The Wake Up Test: 2 assisstants Monitors motor function, simple to
perform
Problems - extubation/lines/hardware, air embolism, awareness, false neg.
Containdications – paresis, uncoop.Modified for use in small children
(withdrawal to tetanic stimulus)
SOMATOSENSORY EVOKED POTENTIALS
ContinuousSensory tractsLatency (> 0.2msecs)Amplitude (> 50%
decrease)Cortical or Spinal
MOTOR EVOKED POTENTIALS
MEP is basically an EMG potential
recorded over muscles in the hand or foot
in response to depolarization of the
motor cortex using transcranial stimulus.
MEP profoundly affected by anesthetic
agents, recordable only during TIVA
MEP cannot be recorded in the presence
of complete neuromuscular blockade.
Extubation of the patient
Extubation may be performed
immediately
Extubation in the ICU
Indications for postoperative mechanical ventilation :
VC was < 30% of predicted.Severe gas exchange abnormality
(↑PaCO2).Duchenne muscular dystrophy.Severe CP.Patient with congenital heart. Severe face edema.PaO2 on mask ↓70 mmHgRespiratory rate > 35 breath /min.
Post operative care
Pulmonary care.
Fluid management.
Pain control. How?
Laboratory studies.
Case Study
29 ys male pt. 110 kg. 9 days s/p MVA SCI. hx = asthma, donated one kidney.
Planned surgery is a C1-3 Cervical fusion. dx: occipitoatlantal instability?
Pre Op
Monitors
Induction
Maintenance
Emergence
Post Op
Question All of the following are potential risk
factors for POVL except for 2 of the following.
•A. Obesity•B. Long Prone Cases•C. Anemia•D. Pressure on the globe•E. Hypotension•F. Glaucoma•G. Cataracts
Question •Paraplegia is the result of which of the
following injuries?
•A. Occlusion of the artery of adamkiewicz•B. Spinal cord transection at C7•C. Spinal cord transection at L2•D. A & C are both correct•E. All of the above are correct