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