Dr. Adham A.monem Saleh

M.D. Anesthesia, Intensive care,

and Pain management.

Ain Shams University

COMMON NEURORADIOLOGICAL

PROCEDURES

PATIENTS REQUIRING SEDATION OR GENERAL

ANESTHESIA FOR NEURORADIOLOGY, WHY?

Anxiety and panic disorders. Claustrophobia. Developmental delay and learning difficulties. Cerebral palsy. Seizure disorders. Movement disorders. Severe pain. Acute trauma with unstable cardiovascular,

respiratory, or neurologic function. Significant comorbidity. Pediatric age group.

SPECIAL CONSIDERATIONS FOR ANESTHESIA IN REMOTE AREAS

Senior anesthesiologist is prefered, not a

trainee.

Anesthesia equipment and the imaging

equipment compete for the already narrow

space of the radiology unit.

The anesthesia workstation and the monitors

are usually the oldest in the facility.

Lack of communication between the

anesthesiologist and the radiology staff.

Inadequate preoperative patient preparation.

Considerations for day case anesthesia

(patient selection, anesthetic techniques,

recovery and discharge).

ASA GUIDELINES FOR ANESTHESIA OUTSIDE

OPERATING ROOM Reliable Oxygen source (pipelines – cylinders). Adequate Suction.

Scavenging system (if inhalational agents are used).

Anesthesia machine with equivalent standards to that in OR and maintained to same standards.

Adequate monitoring equipments to allow adherence to ASA standards for basic monitoring.

Electrical outlets : Sufficient for anesthesia machine and monitors.

Adequate illumination :Battery operated backups.

Sufficient space :- For personnel and equipments. - Easy access to patient, anesthesia machine, and the monitor.

Resuscitation equipment immediately available : - CPR equipments.- Emergency drugs.- Defibrillator.

MONITORING

Universal standards :Standard I : requires a qualified anesthesia personnel to be present in the room throughout the conduct of anesthesia.

Standard II : continous evaluation of the patient's oxygenation, ventilation, circulation, and temperature ( ECG - pulse oximetry - capnography - NIBP ).

ANESTHETIC TECHNIQUES

Techniques vary from no anesthesia / minimal or deep sedation (i.e. MAC) / up to general anesthesia.

It depends on : patient’s medical condition. desired level of anesthesia. procedure to be performed. duration of procedure.

DEFINITION OF GA AND LEVELS OF SEDATION

Minimal sedation

( anxiolysis )

Moderate sedation

( previously called conscious sedation )

Deep sedation General anesthesia

Responsiveness Normal response to verbal stimulation

Purposeful response to verbal or tactile stimulations

Purposeful response following repeated or painful stimulation

Unarousable even with painful stimulation

Airway Unaffected No intervention required

Intervention may be required

Intervention required

Spontaneous ventilation

Unaffected Adequate May be inadequate

Frequently inadequate

Cardiovascular function

Unaffected Usually maintained

Usually maintained

May be impaired

MONITORED ANESTHESIA CARE (MAC)

Administration of drugs with anxiolytic, hypnotic, analgesic, and amnestic properties either alone or in combination with local or regional anesthesia.

Preoperative assessment : Detailed history & examination of the patient

(similar to that done before GA). +

Evaluation of ability of the patient to remain motionless & if necessary actively cooperate throughout the procedure.

+ Fasting status.

The following drugs are used in MAC ( SAFE drugs ):

Propofol Sedative / hypnotic. Short half life. Extra-hepatic clearance. Rapid & clear headed recovery. less incidence of post procedural sedation,

drowsiness. Has anti emetic properties (Subhynotic dose of

10 mg is said to be effective ).

Benzodiazepines

Anxiolytic, amnestic, and hypnotic properties.

Midazolam : Commonly used for moderate to deep sedation. Short elimination half life (1 to 4hrs). Dose : 0.02-0.03 up to 0.1 mg/kg IV.

Diazepam : Longer elimination half life ( > 20 hrs). active metabolites (desmethyl diazepam, oxazepam).

Opioids Provide analgesia component in balanced

anesthesia technique. Disadvantage: do not provide amnesia.Adverse effects Respiratory depression. muscle rigidity . nausea / vomiting. Urinary retention (esp. old age).

Sedation / anesthetic drug interaction :

Opioids + benzodiazepines : synergism in hypnotic / analgesic / amnestic properties.

TYPICAL ADULT INTRAVENOUS RANGES

Drug Typical adult IV dose range

Benzodiazepines

Midazolam 1-2 mg (0.02 to 0.1 mg/kg) Diazepam 2.5-10 mgOpioid analgesics

Alfentanil 5-20 µg/kg bolus 2 min. prior to stimulus Fentanyl 0.5-2.0 µg/kg bolus 2-4 min. prior to stimulus Remifentanil Infusion 0.1 µg/kg/min. 5 min prior to stimulus

Wean to 0.05 µg/kg/min as toleratedAdjust up or down in increments of 0.025 µg/kg/min Dose accordingly when co-administered with midazolam or propofolAvoid boluses

Hyponotics

Propofol 250-500 µg/kg boluses25-75 µg/kg/min infusion

Dexmedetomidine Loading dose: 0.1-1 µg/kg over 10-20 min.Maintenance infusion: 0.2-0.7 up to 1 µg/kg/h

Recommended doses of drugs for sedation in pediatric patients :

Chloral hydrate : 50 to 100 mg/kg PO. used in healthy infants & children. Can produce mild to moderate hypoxia.

Diazepam : 0.1 mg/kg. Midazolam :

0.05mg/kg IV. 0.5 mg/kg PO.

Morphine : 0.05-0.1mg/kg IV.

Ketamine : 0.25- 0.5 mg/kg IV , 2-3 mg/kg IM , 5 mg/kg PO.

GENERAL ANESTHESIA TECHNIQUE

Endotracheal intubation & IPPV, or LMA with

spontaneous breathing / IPPV.

Induction of general anesthesia : Propofol /

Thiopentone.

Maintenance of anesthesia : volatile anesthetics /

TIVA.

At the end of procedure patient is transported to

recovery area where further care is provided by

trained anesthesia personnel.

RADIOLOGY SUITE SHOWING NECESSITY FOR ANESTHESIA EQUIPMENT AND ANESTHESIOLOGIST TO BE REMOTE FROM THE PATIENT'S HEAD

SPECIFIC RADIOLOGIC PROCEDURES

COMPUTED TOMOGRAPHY CT is a medical imaging method in which an

image of the inside of an object is generated from a large series of 2D images taken around a single axis of rotation.

Used for diagnostic or therapeutic purposes.

Hypodense (dark) areas denote infarction.

Hyperdense (bright) areas denote calcification or hemorrhage.

Problems faced by anesthesiologist :

• Inaccessibility to patients.

• Interference with monitoring.

• In an intubated patient, care should be taken

that sides of scanning tunnel do not dislodge

the circuit.

• Adverse effects of contrast media.

• Exposure to ionizing radiation.

Patient monitoring : Basic monitoring standards. Monitors should be easily viewed.

Anesthetic considerations

Elective Emergency

• Preanesthetic visit on day of the procedure.

• Head injury patients with ongoing blood loss or raised ICP.

• Considered full stomach patients.

• Either scanned awake or intubated following rapid sequence induction.

Contrast media :

Contrast media are often used in CT scan.

Types :

Iodinated : hyperosmolar & toxic.

Non iodinated : low osmolarity & fewer side effects.

Adverse effects :

Nephrotoxicity.

idiosyncratic reactions.

anaphylactic/ anaphylactoid reactions.

Contrast related adverse reactions

Adverse reactions High-osmolarity

contrast media (%)

Low-osmolarity contrast media (%)

Nausea and vomiting 6.0 1.0

Urticaria 6.0 0.5

Hoarseness, sneezing, cough, dyspnea, facial edema

2.6 0.5

Hypotension 0.1 0.01

Treatment: usually supportive ttt

O2

Bronchodilators

Corticosteroids

Epinephrine

Patients with past history of reaction to contrast media Prednisolone 50 mg IV, 12 h. & 2 h. prior to the

procedure.

Antihistaminics immediately before the procedure.

Contrast induced nephropathy :

Acquired ARF.

Incidence is higher with hyperosmolar agents,

especially in dehydrated patients.

For prevention, maintain proper hydration

before, during, and after the procedure.

Usually self limiting & resolves within 2 weeks.

Acetyl Cysteine / Ascorbic acid can be used.

Acetyl cysteine 600 – 1200 mg orally twice daily for 2 days before procedure & 2 days after procedure.

Ascorbic acid 3 gm PO, 2 h before procedure / and 2 gm twice daily, the day after procedure.

Radiation exposure :

More with CT scan than any other radiological procedure.

Radiation toxicity :

Somatic effects.

Genetic injury.

Dosimeters: to monitor exposure.

Ionizing Radiation follows Inverse square law.

Radiation exposure decreases proportional to

square of distance from the source.

Radiation exposure is limited by :

lead aprons.

thyroid shields.

using movable leaded glass screens. Anesthesiologist

can stand across the screen & monitor the patient.

MAGNETIC RESONANCE IMAGING

Can differentiate areas of dissimilar anatomy.

Noninvasive.

No ionizing radiation used.

Provides excellent soft tissue contrast.

Can obtain image in any plane.

Differentiates between white & grey matter, permits resolution of CSF flow.

Disadvantages: Time consuming, patient movement can produce artifact, Noise > 90db.

CATEGORIES OF PATIENT REQUIRING ANESTHESIA OR SEDATION IN MRI

Patient Category Requirement

Pediatric Sedation / anesthesia

Developmental delay or psychiatric illness

Education, sedation or anesthesia

Intensive care Intubation & IPPV

Raised intracranial pressure Beware of CO2 retention with sedation

CONCERNS IN ANESTHETIC MANAGEMENT

FOR MRI

Patient accessibility & visibility.

Absolute need to exclude ferromagnetic objects.

Interference / malfunction of equipments caused by

changing magnetic fields.

Potential degradation of images caused by

radiofrequency currents from monitoring equipments.

Possibility of heat generation within monitoring

wires as a result of electromagnetic conduction.

Recommendations to prevent thermal injury

Inspection of monitor wires before every use.

Avoid loop formation of monitoring wires,

keeping them straight.

Avoid conductors touching the patient at more

than one location.

To avoid above listed problems , anesthesiologist

must be involved in planning & construction of MRI

suites.

MRI COMPATIBLE MONITORING EQUIPMENT

ECG: liquid crystal screens, high impedance graphite electrodes & leads.

Blood pressure: oscillometer with nonferrous guage.

Respiratory gas: side stream sampling with long sampling line.

Temperature: skin temperature sensing strips (burns reported with probes).

Pulse oximeter: non-ferromagnetic model

MRI COMPATIBLE ANESTHETIC EQUIPMENT

Laryngoscope: plastic scopes with paper or aluminium covered lithium cells.

Stylet: copper model available. Endotracheal tube: spring within cuff valve

may distort images; nonmagnetic version is available, avoid metal reinforced tubes & metal connectors.

Laryngeal mask airway: spring within cuff valve may distort images; nonmagnetic version is available.

Ventilators: compatible versions are available.

Anesthetic machine: nonmagnetic machine,

aluminium cylinders required ( e.g. Aestiva-5 MRI

workstation from Datex Ohmeda).

Infusion pumps: extensions are needed.

Self inflating bags: valveless with no magnetic parts.

Suction: wall mounted with a 10 m tubing.

Defibrillators: resuscitation usually carried out

outside magnetic field (We don’t perform CPR on

MRI table).

Implanted devices or objects representing a

contraindication to MRI :

Cardiac pacemaker.

Some artificial cardiac valves.

Metal eye splinter.

Vascular clips.

Interventional radiology device.

Orthopedic device (prosthetic joint , wires , plates ,

screws).

ANESTHESIA FOR INTERVENTIONAL

NEURORADIOLOGICAL PROCEDURES

Most commonly :

Occlusive procedures:

Embolization of cerebral & dural AVM.

Coiling of cerebral aneurysms.

Opening procedures:

Thrombolysis of thromboembolic stroke.

Ballon dilatation of vessels.

Vascular access:

Femoral / carotid / brachial artery.

ANESTHETIC GOALS

Maintenance of patient’s immobility.Physiologic stability. Manipulation of regional & systemic

blood flow.Evaluation of coagulation profile. Treating complications that can occur

during the procedure. Rapid transition between sedation &

awake responsive state.Providing brain protecting measures.

ANESTHETIC MANAGEMENT Pre-procedural anesthetic evaluation, careful

neurologic examination (preexisting deficits & Glasgow Coma Score).

Airway examination (better to secure airway early in patients with risk of airway compromise).

Adequate intravenous access established. Standard anesthesia monitoring established. Invasive arterial blood pressure monitoring

Deliberate hypotension During embolization of AVM - coiling of aneurysm. Drugs used as esmolol - SNP - labetolol.

Deliberate hypertension

To increase collateral flow to ischemic areas.

Drugs used are phenylephrine - vasopressin.

Urinary catheter: use of large amounts of radiologic

contrast media & osmotic diuretic agents.

Sedation: combination of BZD & opioids.

GA: accomplished by volatile agents or TIVA (considering

desirability of fast emergence for neurologic evaluation).

Padding of pressure points.

Antiemetic can be given.

Heparin is used in some procedures: 70 units/Kg, to

achieve ACT 2-3 times the normal range.

Protamine can be used to reverse heparin effect at

the end of the procedure.

Complications of Liquid embolic agents:

e.g. Cyanoacrylate glue (rapidly polymerizing)

The polymerization process results in heat liberation

into the surrounding tissues during embolization.

Systemic absorption leading to acute hemorrhage

and pulmonary embolism.

COMPLICATIONS OF INTERVENTIONAL NEURORADIOLOGICAL PROCEDURES

CNS : Hemorrhagic a) aneurysm perforation.b) intracranial vessel injury. Occlusive a) thromboembolic phenomenon.b) displacement of coil.c) vasospasm.OTHERS :- Contrast reaction.- Contrast nephropathy.- Hemorrhage at puncture site - groin hematoma.

MANAGEMENT OF COMPLICATIONS

Initial resuscitation.

Communicate with radiologist.

Call for help.

Secure the airway & ventilate with 100% O2.

Determine whether problem is hemorrhagic or occlusive :

If hemorrhagic: immediate heparin reversal, deliberate

hypotension.

If occlusive: delibrate hypertension.

Consider Mannitol , dexamethasone , anticonvulsants.

GAMMA KNIFE RADIOSURGERY

Definition :Gamma knife radiosurgery is a type of radiation therapy used to treat tumors and other abnormalities in the brain (e.g. AVM , Trigeminal neualgia).

In Gamma knife radiosurgery, specialized equipment focuses as many as 200 tiny beams of radiation on a tumor or other target. Although each beam has very little effect on the brain tissue it passes through, a strong dose of radiation is delivered to the site where all the beams meet.

The accuracy of Gamma knife radiosurgery results

in minimal damage to healthy tissues surrounding

the target and, in some cases, a lower risk of side

effects compared with other types of radiation

therapy. Also, gamma-knife radiosurgery is often a

safer option than traditional brain surgery.

Gamma knife radiosurgery is usually a one session

therapy completed in a single day.

REFERENCES Miller’s Anaesthesia, 7th ed.

Wylie and Churchill Davidson’s. 7th ed.

Morgan. Clinical Anaesthesiology, 4th ed.

Barash .Clinical Anaesthesia , 6th ed.

Varma M.K , Price .K , Kessell.G , Manickam.B .Anaesthetic considerations for interventional neuroradiology .Br J Anaesth 2007;99:75-85

Pannu N,Wiebe N , Tonelli M.prophlaxis strategies for contrast induced nephropathy. JAMA,June 21, 2006- Vol295,No.23

Practice advisory on anaesthetic care for magnetic resonance imaging .Anaesthesiology 2009; 110:459 – 79