Transcript Lecture 3: Anesthesia care for Radiology

Anesthesia care
for Radiology
© 2016 Mark S Weiss, MD
Department of Anesthesiology and Critical Care
Clinical Scenarios
 Neuro- Interventional radiology
 Body Interventional radiology
 Diagnostic imaging (MRI, CT) in patients unable to remain still
• Pediatrics
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REMOTE Anesthesia2
 Anesthesiologists are truly “removed” when providing care
for Radiologic procedures
• Remote Anesthesia locations
• Remote proximity from patient’s airway
– May view patient from afar in a control room
 Extreme importance of airway security, organization of
lines/monitors, providing effective and safe anesthetic,
communication with radiologists, technologists
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Preoperative Considerations
 Common patient dependent factors influencing anesthesia
care
• Mental status/psychology (anxiety, claustrophobia, age, pain
tolerance)
• Ability to tolerate supine positioning (CHF, severe pain)
• Acuity of illness
 Common procedural factors influencing anesthesia care
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Complexity of study/procedure
Need for a quiet procedural field
Length
Proximity of airway
 Anesthetic need and plan occurs on a case by case basis
• There is no “default” anesthetic plan for most radiology proceduresparticularly more off-site diagnostic radiology areas
• COMMUNICATION is ESSENTIAL
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Radiology Safety Overview
 Safety considerations must be given to providers and patients
 Must recognize the safety hazards of imaging technology
• X-ray- radiation, MRI- magnetic field
 Risks of positioning a patient for entering a hollow and narrow
imaging device
 Contrast Administration
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X-ray Basics
 CT, X-ray and fluoroscopy machines emit ionized radiation for
image construction
 Radiation exposure comes from three sources:
• directly from the imaging beam
• radiation from the source
• scatter from the patient
– greatest exposure for anesthesiologists.
 The organs that suffer the most damage from ionizing
radiation include the eye/cornea, thyroid and gonads
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Radiation Exposure
 The maximal radiation dose:
• 50 millisieverts (mSV) annually
• a lifetime cumulative dose of 10 mSV x age or
• monthly exposure of 0.5mSv for pregnant women*
 This should be measured by dosimeters
*The 2007 Recommendations of the International Commission on Radiological
Protection. ICRP publication 103. Annals of the ICRP 2007;37:1-332.
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MRI Basics
 Magnetic Resonance Imaging (MRI) applies a strong static
magnetic field (typically 1.5 – 3 Tesla) and a second magnetic
field is created by pulsed radiofrequency (RF) to a target
tissue area.
 A subsequent RF signal is emitted from tissue and detected
by a RF coil which allows the reconstruction of an image.
 pulsed RF signal creates a loud sound:
• May impair providers ability to listen to pulse-ox/communicate with
staff
• May cause hearing loss- patients NEED ear plugs
 May require long scanning times, (sometime > 1 hour)
• Must be accounted for in the anesthetic planning
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MRI Risks to patient
 Little evidence that MRI technology poses
direct tissue injury
 Severe patient harm and even death has
been documented by ferromagnetic objects
projected when entering a strong magnetic
field
• Ex: O2 cylinders, stretchers, IV poles, keys
 Risk for thermal burns from various
equipment/monitors/implanted patient
devices
• Ex: ECG electrodes and pulmonary artery
catheters, wires, ICDs/pacemakers, VP shunts
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FDA Labeling for MRI Compatibility
MRI Safe: approved for
use (green square icon)
MRI Conditional:
approved for certain
magnetic fields (yellow
triangle)
MRI unsafe: known
ferromagnetic material
(red circle)
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Implantable Electronic Devices in MRI
 The ASA Task Force for MRI standards believes that cardiac
pacemakers and implantable cardioverter-defibrillators (ICD)
are generally contraindicated for MRI.
• may be life-threatening within the 5 gauss line
 Other implanted electronic devices and associated wiring may
transfer energy during the MRI scan, causing tissue damage,
malfunction of the device, image artifacts, and device
displacement
• All responsible physicians must ensure MR safe/compatibility of
specific device in patient
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MRI Care Issues
 Loud environment, anesthesiologist removed from patient
• Ensure line of site
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Emergency MRI Scenarios
 Cardiac Arrest in the MRI
• Remove patient from imaging room so resuscitation personnel and
equipment may be more readily available
 Requirement to quench magnet
• uses cryogenic gases to dissipate the magnetic field
• This can create a hypoxic environment if the patient is not retrieved
from the room in a timely manner.
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Patient Positioning
 Careful attention must paid to extremity positioning
• Avoid stopcocks pressed into patient’s body
 Slack must be given to IV lines (taped securely), monitors
• If GA- use tube extensions to ensure slack and tight connections
 Trial run should be performed to ensure lines reach full extent
of table movement
• If a rotating imaging arm is used, a trial run should ensure no lines are
caught
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Contrast Administration Complications
 Patients undergoing are often administered intravenous
iodinated contrast that absorb x-rays and have significant, but
rare side effects.
 Severe Side effects:
• Airway: glottic edema, bronchospasm, pulmonary edema
• Cardiac: Arrhythmias, cardiac arrest
• Other: Seizures, Anaphylaxis
 Mild side effects:
• Allergic: urticaria, pruritus, erythema and upper respiratory effects such
as nasal congestion, scratchy throat or sneezing.
• Contrast nephropathy
– anesthetic techniques may reduce risk by isotonic crystalloid
volume expansion and avoiding other nephrotoxic drugs
○ some limited evidence that isotonic sodium bicarbonate may provide
more risk reduction in patients with mild pre-existing renal dysfunction
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Neuro-Interventional Radiology
 Fast growing field offering
various treatments for
cerebrovascular and other
neurologic complications
• Routine use of anesthesia care
 patients have pathology that
alters mental status so
anesthesia requirements may
be different
 Emergency care- ICP
management- need familiarity
with CSF drains, NeuroCritical Care management
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Anesthesia for Common Neuro IR Procedures
 Diagnostic vascular imaging
 MAC- minimal to moderate sedation (must follow commands: “hold
your breath,” avoid disinhibition)
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Usually standard monitors
May progress to intervention so discuss with radiologist what the procedural
plan is
 Vasospasm
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Often after SAH- patient may be obtunded/disinhibited and will need a GA,
otherwise MAC
Nicardipine infusion can cause profound (albeit short lived) hypotension; be
prepared with rescue drugs
 Embolization for intracranial bleeds (AVM, tumors)
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Can be MAC or GA depending on patient and need for lack of movement
A-line for monitoring, need tight BP control
 Aneurysm coiling
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GA (patient must be completely still)
A-line, will need large bore IV access
Be prepared to move emergently to the OR if the aneurysm ruptures
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Digital Subtraction Angiography (DSA)
 Fluoroscopic imaging technique to optimize
vascular signal in an area encased in bone
(skull) and soft tissue (brain)
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Initial “Digital mask” is acquired
Live image acquired with IV contrast administration
Subtraction of two images allow enhancement of
cerebral vasculature
 DSA requires immobility to allow for alignment
between digital mask and live image to
decrease motion artifacts
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Patient and procedural factors must be considered
for anesthetic plan
– MAC- patient must follow commands to remain
still (not too sedated), consider GA if patient not
compliant
Digital Mask Live Image
DSA Image
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Acute Intra-Procedural Neuro IR Complications
 Intracranial hypertension
 Pulmonary edema leading to hypoxia, ventillatory difficulties
 Hemorrhage (intracranial aneurysm rupture, vascular
dissection, retroperitoneal bleed)
 Displacement/fracture of coil
 Cerebral vasospasm
 Contrast reactions
 Sedation related problems
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IR Procedures
 Most cases performed with light sedation and local infiltration.
There is a wide variety of procedures
 Complex, Higher Risk cases that require anesthesia care:
• Ablation of venous and arteriovenous malformations
• aortic endoleak repair
• complex vascular stenting procedures
 Emergency Procedures, Unstable Patients:
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embolization for upper or lower gastrointestinal bleeding
Hemoptysis
Trauma
Postpartum hemorrhage
percutaneous drainage for urosepsis and biliary sepsis
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IR Anesthesia Care
 Approach is dependent on patient and procedural classes
 Patient factors
• Anxiety, low pain threshold, inability to lie flat
• Acuity/Complexity of medical condition (s)
 Procedural factors
• Work near airway, critical vasculature
• Length of time
 Sedation level: moderate vs. deep vs. GA varies case by case
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Diagnostic Imaging
 For select patients undergoing MRI/ CT scan, anesthesia may
be requested
 Oftentimes, this is a staff coverage challenge (particularly
when ORs are busy)
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GA for Diagnostic Radiology
 Rooms rarely setup to accommodate general anesthesia
• It is CRUCIAL to perform rigorous room check (MSMAIDS!), double
check supplemental O2 delivery
• Induction may be performed in a designated area to better meet the
needs of airway management
– Common in pediatric hospitals
• Ventilators may be specific to radiology rooms- different than
anesthesia machine
– May need to manage ventilator with respiratory therapist
– May not be able to accommodate inhalational agents- TIVA
 If plan to extubate- imaging time must be considered if NMBD
to be used
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Be Prepared
 Identify ahead of time reinforcement back up
• Telephone communication
• Access to Emergency medications
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