Download Abdominal Aortic Aneurysm

Anesthesia for Vascular Procedures, UCH practice guide
Gregory Myers, MD and Ferenc Puskas, MD
Abdominal Aortic Aneurysm
Perioperative risks
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Depends on patient condition – High incidence of co-existing disease (HTN, CAD, Carotid
disease, atherosclerosis of major vessels)
Perioperative mortality of infrarenal aneurysms from the national database is 5.6-8.4% with the
mortality rate of ruptured AAA over the last 4 decades remaining at 50%. If all ruptured AAA,
including patients that died before reaching the hospital, were included the mortality very well
could be >90%.
Nonlethal MI 4-15%
Respiratory complications 5-10%
Renal insufficiency 2-5% (infrarenal), 17% (suprarenal)
Bowel complications (Intestinal ischemia)
Paraplegia: Anterior spinal syndrome - loss of motor and pinprick sensation but preservation of
vibration and proprioception. The patient has increased risk of neurological complication if the
aorta is clamped above the Major Anterior Segmental Medullary Artery (Artery of Adamkiewicz)
which has variable origin: T5-8 15%, T9-12 60%, L1-2 25%.
Perioperative Considerations
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Preoperative - Appropriate labs drawn, assess co-existing morbidities, consider postoperative
pain control (epidural vs. IVPCA), cell saver and CSF drain (See indications below), type and
cross
Monitoring – Invasive monitoring - arterial line, central line (CVP, +/- PAC); +/- TEE, +/- CSF
drain, neuromonitoring (MEP’s/SSEP’s)
OR checklist:
Emergent AAA:
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Room warmed
OR flat bed in room (for fluoroscopy)
C-arm notified – check with OR nurse
Belmont and Level I - Primed
Colloid (albumin + Hextend)
Consider Cell saver
Double/Triple transducer connected
Surgeons will access femoral artery for aortic balloon occlusion – If combined IR
procedure
For Interventional: Do not induce anesthesia until aorta is occluded by the balloon, if
possible
Access:
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Arterial line – preinduction if possible
Large bore IV’S (connected to Belmont and Level I)
Central line – can be placed later unless peripheral access not adequate
Elective AAA:
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Arterial line
Central line
Large bore IV’s
Epidural – traumatic/bloody tap of epidural or CSF drain may require cancellation of
case
CSF drain: placed in high risk patients for treatment/prevention of spinal cord ischemia
 redo-AAA/extensive aortic repair
 involves thoracic aorta
 If combined stent procedure
Drugs: Similar to cardiac setup: heart box, fast track box, syringes (nitroglycerine-20mcg/ml,
epinephrine-10mcg/ml, phenylephrine 100mcg/ml, and ephedrine 5-10mg/ml); Infusions: 1st tier:
epinephrine, fenoldopam, nicardipine 2nd tier: nitroglycerin, dopamine, vasopressin; mannitol (12.5 - 25
grams), heparin (50 - 100 units/kg), before cross-clamp upon surgeon’s request.
Infusions:
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NS carrier, octopus
Fenoldopam (keep low dose 0.01-0.1 mcg/kg/min for renal perfusion – more data needed)
Nicardipine: 1 - 4 mcg/kg/min
Epinephrine: Start 0.01 mcg/kg/min
Vasopressin: Start 0.04 units/min
Intraoperative:
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Before Cross-clamp
o Consider renal protection – Mannitol, loop diuretic and dopamine are widely given
despite studies demonstrating little or no benefit. Fenoldopam infusion (a selective
dopamine type 1 agonist) may be beneficial in dilating renal and splanchnic vasculature
but more data needed.
o Heparin needs to be available five minutes before aortic cross clamping, check ACT
baseline, 3minutes after heparin given and every 30 minutes thereafter while crossclamped.
During/After Cross-clamp
o Cross clamp: Sudden increase in afterload. Decrease afterload with vasoactive drugs
(fenoldopam, nicardipine) to decrease LV wall tension. However maintain a CVP > 10
mmHg
o However when aneurysm is opened, back-bleeding may lead to sudden hypovolemia
(maintain CVP, get ready for bleeding)
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Organs distal from clamp will be hypoperfused and ischemic – turn off lower body
warmer.
 Infrarenal: this avoids most major organs and has the least hemodynamic effect and
post clamp complications. Patients still have decreased renal blood flow, increased
renal resistance and therefore renal protection should be considered.
 Suprarenal: renal, spinal and lower extremity ischemia possible
 Supraceliac: hemodynamic changes can be drastic and likely require dilators to decrease
afterload. The kidneys, intestines and liver are ischemic thus coagulopathy, acidosis
and renal dysfunction are likely.
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Needs ABGs Q10 minutes during clamp
FIO2 100%
Correct acidosis (H2CO3/THAM)
Stablize electrolytes
Volume, calcium and consider H2CO3/THAM before clamp
release
Keep CVP above 15 mmHg before clamp release
Have pressors ready and in line during unclamping
Coags, TEG, CBC after clamp release
 Post Clamp: Response to unclamping will depend on clamp time and location of clamp.
It is important to communicate during unclamping with surgery to optimize cardiac
output. During unclamping large swings hymodynamically can occur and vasoactive
medications need to be readily available. Partial or complete reclamping may be
needed, to optimize hemodynamic state, if patient does not tolerate initial
unclamping.
Aneurysm involving thoracic aorta, redo or extensive AAA repair, thoracic stent
Spinal cord ischemia, thus paraplegia is a major concern.
Consider CSF drain preoperatively (check coags, if bloody tap, consider cancellation of case). Consider
intraoperative neuromonitoring with SSEP’s/MEP’s.
Spinal Cord Perfusion pressure= MAP – ICP (spinal fluid pressure)
 To increase spinal cord perfusion pressure:
o Increase MAP
o Decrease spinal cord fluid pressure (drain CSF)
CSF drain:
 Initial pressure goal 10-12 mmHg
 Zero spinal pressure monitor to right atrium
 If SSEP/MEP’s signals decrease - drain 10ml
 Try to keep spinal pressure <10 mmHg
 Do not drain more than 20 ml/hr – risk of subdural or subarachnoid hematoma or brain stem herniation
 If CSF turns bloody - turn off drain and do not use it
 ICU:
o On wakeup: paraplegia: MRI spine to r/o hematoma
o New onset weakness: drain as above
 Do not leave drain open. Monitor pressure,
drain (3-way stop)
 Optimize MAP
o If legs are okay: Cap CSF drain. Do not monitor. D/C CSF
drain 24 hours after cap.
o New onset weakness after drain is out. Rule out
hematoma and other causes. Optimize MAP. Replace
spinal drain if indicated.
Postoperative Considerations:
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BP and HR control
Extubation depends on OR course and fluid shifts/ presser quirements
Analgesia: IVPCA vs. epidural
Neurological deficit – see CSF drain above
Key References: Miller’s Anesthesia 6th Edition. RD Miller; Essence of Anesthesia Practice 2nd Edition, Michael F. Roizen, Lee A.
Fleisher pg 377; Department of Anesthesia, Neurology and Surgery, University of Pennsylvania, Strategies to Manage
Paraplegia Risk After Endovascular Stent Repair of Descending Thoracic Aortic Aneurysm 2005.; New England Society for
Vascular Surgery, Establishing a Protocol for Endovascular Treatment of Ruptured Abdominal Aortic Aneurysm, 2004.
OR AAA summary checklist:
Preoperative: consent, H&P, labs, epidural?, CSF drain?, awake a-line?, large PIV
OR: Room warm, OR flatbed, Belmont/level one wet down, double transducer (a-line, central
line), central line set up (ultrasound, gown, gloves), a-line set up, IV set up
Drugs: Induction drugs, cardiac box, mannitol, heparin, syringes (epinephrine, phenylephrine,
ephedrine, nitroglycerin, esmolol),
Drips on octopus: NS carrier, epinephrine, vasopressin, fenoldopam, nicardipine.
Induction: HD stable
Intraoperative:
Before cross-clamp: start fenoldopam, consider mannitol, lasix, dopamine for renal
protection. Check baseline ACT before giving Heparin 5 min before cross-clamp.
Recheck ACT 3 minutes after giving heparin and then q30min.
During cross-clamp: determine cross-clamp level. If supraceliac, the kidneys, intestines
and liver will be ischemic: coagulopathy, acidosis, renal dysfunction likely: check ABG
q10min, fIO2 100%, correct acidosis (tham/H2CO3), stable electrolytes, keep CVP
approx 15mmHg, maintain pressure
If CSF drain in place: initial goal 10-12 mmHg, zero at atrium, if SSEP/MEP’s
decrease. Drain 10ml – no more than 20ml/hr, optimize BP
Post clamp: depends on clamp location – have drips ready and treat BP aggressively
with fluid/pressors
Carotid Endarterectomy
Indications:
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Asymptomatic patients with >60-70% stenosis are candidates if low perioperative risk of
morbidity/mortality (<3%).
Patients who have experienced Reversible Ischemic neurological deficit, TIA or stroke
Risk Factors:
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Smoking , DM, Hypertension, hypercholesterolemia, hypertriglyceridemia, obesity, family
History
Male>Female
Perioperative risks
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Mortality 0-2.6%
Permanent neurological deficit 0-6.3%
Perioperative MI 0-4%
Stroke risk 1-2% per year in asymptomatic patient vs. 6-10% if patient has TIA’s: stroke risk
increases significantly in asymptomatic patient if stenosis is >75%
High incidence of CAD
Perioperative Management
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Preoperative –Appropriate labs drawn, assess co-existing morbidities, patient should continue
blood pressure medications (hold lisinopril) and ASA perioperatively. Determine if awake or
general anesthesia will be used
o Regional - peripheral block: superficial and deep cervical plexus block C2-C4
dermatomes
Advantages:
 Continuous neurologic assessment –most sensitive method for
cerebral perfusion
 Avoidance of expensive cerebral neuromonitoring
 Reduced need to shunt
 Better BP control and decreased use of vasopressors
 92% patient satisfaction
Disadvantages:
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Patient cooperation
Unable to use cerebral protection with anesthesia which may
increase neurological injury if ischemia occurs
Seizure or loss of consciousness with clamping and need for
immediate airway
Need to convert to general anesthesia 2-6% of the time
Local anesthetic toxicity/phrenic nerve paralysis
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Difficult anatomy – short neck and high bifurcation
Increased catecholamines – increased HR/BP
Most reports show that no differences in perioperative stroke or death rate based on anesthetic
technique - Regional vs. General
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Monitoring- Arterial line (consider preoperative), +/- neuromonitoring, central line usually not
indicated but if needed subclavian or femoral line are most practical secondary to surgical site.
OR Checklist:
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General anesthesia- regular OR bed
Single transducer - Arterial line (glucose and BP)
Infusion pump
2 large bore IVs
Lido Tube, Lidocaine ointment, LTA – prevent postoperative coughing
Consider bilateral BIS or Sedline
Drugs: Regular narcotic bag; syringes: nitroglycerine 20mcg/ml, epinephrine 10mcg/cc, phenylephrine
100mcg/ml, ephedrine 5-10mg/ml, glycopyrrolate, atropine, esmolol
Infusions: Infusions on a separate IV line from volume IV
 NS carrier, three way octopus
 1st tier:
o Nicardipine: 1-4 mcg/kg/min
o Vasopressin: Start 0.04 units/min
 2nd tier
o Phenylephrine: 0.15-0.75 mcg/kg/min
o Nitroprusside: 0.1-10mcg/kg/min
Induction:
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Place arterial line before induction if indicated
Maintain MAP and heart rate
Intraoperative: Hemodynamic fluctuations are frequent during manipulation of the carotid area. BP
and heart rate should be maintained keeping in mind that cerebral autoregulation is shifted with chronic
hypertension. Short acting BP meds should be used secondary to these frequent shifts. Other
important considerations are:
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Maintain patients normal BP, CO2 levels
If patient does not have adequate collateral flow - BP may need to be maintained at 10-20%
higher than normal.
If BIS/Sedline/EEG changes occur unilaterally – notify surgeon and optimize BP
Slow HR - be prepared for bradycardia upon carotid bulb dissection (titrate glycopyrolate)
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If bradycardia continues surgeon may inject Lidocaine which should blunt this
response effectively intraoperatively. Postoperatively after carotid bulb injection it is
unpredictable if the patient would become hypertensive or hypotensive.
Blood loss usually <200 ml
Consider opioid infusion (remifentanil/sufentanil) to blunt catecholamine response
CNS protection
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Shunt (surgeon preference) or maintain stump pressure
Avoid exogenous glucose
Goal for glucose control <160 mg/dl
Maintain normocarbia, BP
Consider transcranial Doppler/ EEG
Emergence:
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Make environment calming – radio off, overhead lights off
Avoid bucking – Decrease risk of hematoma, hypertension and tachycardia. Lidocaine tube,
lidocaine ointment, IV lidocaine or LTA (depending on length of surgery) on intubation can blunt
this response.
Slow opioid wakeup (titrate fentanyl to effect) to decrease chance of bucking and sympathetic
response vs. quick wakeup for neurological exam.
Postoperative Considerations
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HTN: exclude – hypercarbia, bladder distention and pain, adjust vasodilator infusion
Hypotension (hyperactive carotid sinus) is as common as HTN – rule out MI and cerebral
ischemia. Then treat with volume and vasopressors – likely will resolve in 12-24 hours
Hematoma formation – immediate bedside evacuation of hematoma if compromising airway
Airway edema secondary to venous and lymphatic congestion
Nerve damage – Evaluate hypoglossal (motor tongue), recurrent/superior laryngeal (dysphonia)
and marginal mandibular (facial expression)
Hyperperfusion/Reperfusion syndrome: Causes post-operative neurological dysfunction,
characterized by ipsilateral headache, focal seizure activity, focal neurological deficit and
ipsilateral intracerebral hemorrhage or edema can occur.
CNS (emboli, ischemia, thrombosis, etc)
Residual effects of Carotid bulb Lidocaine injection are unpredictable and can result in
hypotension or hypertension.
MI – most asymptomatic
Regional – phrenic nerve paralysis
Key References: Miller’s Anesthesia 6th Edition. RD Miller; Essence of Anesthesia Practice 2nd Edition, Michael F. Roizen, Lee A.
Fleisher pg 377;Executive Committee for the Asymptomatic Carotid Atherosclerosis Study. Endarterectomy for asymptomatic carotid
artery stenosis. JAMA. 1995;273:1421–1428.
OR Carotid Endarterectomy Check list:
Preoperative: consent, H&P, labs, awake a-line?, PIV, regional vs. general
OR: Room warm, regular OR bed, transducer (a-line), a-line set up, IV set up
Drugs: Induction drugs, cardiac box, heparin, syringes (epinephrine, phenylephrine, ephedrine,
nitroglycerin)
Drips on octopus: NS carrier, vasopressin, nicardipine, opioid infusion
Induction: HD stable, lidocaine on tube - prevent bucking
Intraoperative: Can have wide swings in BP, If poor collateral flow – may need BP 10-20%
higher than normal. Carotid bulb manipulation can cause bradycardia – if continues surgeon
may inject lidocaine to blunt response. Turn off body warmers below clamp site. Blood loss
usually <200ml. CNS protection: avoid exogenous glucose, keep glucose <160mg/dl, maintain
normocarbia/BP, transcranial Doppler, EEG
Wake up: environment calming, avoid bucking