Anaesthetic management of Abdominal aortic aneurysms

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  • 1. Anesthesia management for Abdominal Aortic Aneurysms Dr. Abhijit Nair Consultant Anesthesiologist, Care Hospital, Hyderabad.
  • 2.
    • Popularly called AAA
    • Its a localized dilatation (ballooning)
    • of the abdominal aorta exceeding
    • the normal diameter by more than 50 %
    • 90% occur infrarenally
    • Can occur suprarenally, pararenally
  • 3. Causes:
    • Cigarette smoking
    • Genetic factors –
    • alpha1 antitrypsin deficiency ,
    • Marfans syndrome,
    • Ehler Danlos syndrome
    • Atherosclerosis
    • Others :
    • Infection, trauma,
    • arteritis, cystic medial necrosis
  • 4.
    • The prevalence of AAAs (aortic diameter 30 mm) in chronic smokers is > four times that in lifelong non-smokers
    • the average rate of aneurysm growth in
    • smokers is 2.8 mm per
    • year versus 2.5 mm per
    • year in non-smokers
  • 5. Pathogenesis
    • No unified concept
    • Genetic, biochemical,
    • metabolic, infectious,
    • mechanical & haemodynamic
    • factors
    • Adventitial elastin degradation
    • is the primary event leading to
    • connective tissue destruction
    • in the aortic wall
  • 6. Guidelines & recommendations
    • By Kaiser Permanente for AAA with USG in general population:
    • One-time screening for AAA by USG recommended in men aged 65 to 75 years
    • Routine screening for AAA in women is not recommended
    • It is an option to limit AAA screening to men aged 65 to 75 years who have never smoked
  • 7. ct:
    • With family history of AAA:
    • For men aged 50 and older with a known positive family history of aortic aneurysm in a first-degree relative, AAA screening is recommended
    • The guideline development team makes no recommendation for or against screening women with a positive family history of AAA
    • (Kaiser Permanente Care Management Institute.  Abdominal aortic aneurysm (AAA) screening clinical practice guideline . Oakland, California: Kaiser Permanente Care Management Institute; Apr 2009:37 p)
  • 8.
    • A clinical practice guidelines by the US Preventive Services Task Force recommends one-time screening for AAA by USG in men age 65 to 75 years who have ever smoked
    • This is a grade B recommendation
  • 9.
    • In US, effective January 1, 2007, provisions of
    • SAAAVE Act ( Screening Abdominal Aortic
    • Aneurysm Very Efficiently ) provides a free, one-
    • time, USG AAA screening benefit for qualified
    • seniors
    • Men who have smoked at least
    • 100 cigarettes during their life,
    • and men and women with a
    • family history of AAA qualify
    • for one-time USG screening
  • 10. History:
    • Antyllus, a Greek Surgeon in 2 nd century AD tried to treat AAA with proximal & distal ligature, central incision & removal of thrombotic material
    • Rudolf Matas performed the 1 st successful aortic ligation in humans
    • He also proposed the theory of endoaneurysmorraphy
  • 11.
    • Albert Einstein was operated
    • by Rudolf Nissen in 1949
    • The method :
    • wrapping of aorta with
    • polythene cellophane which
    • induced fibrosis and
    • restricted aneurysm growth
    • EVAR was performed in late 1980s
  • 12. Classification:
    • Crawford classification of thoraco-abdominal aneurysm :-
    • I. Starts below the subclavian artery origin and ends
    • above the renal artery
    • II. Entire descending thoracic aorta up to the
    • bifurcation
    • III. Starts at distal thoracic aorta and also involve the
    • abdominal aorta
    • IV. Confined to upper abdominal aorta
  • 13.  
  • 14. Management
    • Conservative:
    • High risk patients ,
    • repair carries a high risk of
    • mortality, in patients where
    • repair is unlikely to improve
    • life expectancy
    • Surveillance: with a view to eventual repair
    • Repair: if the aneurysm grows more than 1 cm per year or it is bigger than 5.5 cm , symptomatic AAA
    • Open
    • EVAR
  • 15. Medical management:
    • Aggressive BP control: Beta blockers!
    • Antiplatelets
    • Statins
    • 6 monthly USG
    • Cessation of smoking
  • 16. Evaluation of aneurysm
    • Symptoms of aneurysm
    • Site & size of aneurysm
    • Extent
  • 17. Pre-op considerations
    • • Aortic disease is indicative of other vascular disease
    • AAA surgery has high risk of periop myocardial ischemia..
    • » Coronary artery disease.
    • – MI
    • – Stable or unstable angina
    • – LV dysfunction/CHF
    • – Atrial fibrillation
    • – Arrhythmias;
    • Pacemakers in situ!
  • 18.
    • » Peripheral vascular disease
    • » Carotid artery disease:
    • always listen for carotid bruits & ask about TIA/CVA symptoms
  • 19. Other co morbidities:
    • » COPD
    • » HTN
    • » DM
    • perioperative insulin
    • » Renal dysfunction
    • Often exacerbated by
    • periop angiograms,
    • IV contrast
    • NAC may help
  • 20. Drug issues:
    • » To continue cardiac medications
    • up to & including day of surgery
    • » Continuation of ACE inhibitors
    • is controversial;
    • associated with severe hypotension
    • during GA
    • » Diuretics may be held on the
    • morning of surgery
    • » withhold morning insulin
  • 21.
    • » Patients are often taking anticoagulation or antiplatelet agents
    • Coumadin :
    • generally discontinued 7 days
    • prior to procedure; bridge therapy
    • with LMWH may be necessary depending
    • (eg, DVT, heart valve)
    • ASA:
    • discontinue 5 days prior to surgery
    • Clopidogrel :
    • discontinue 7 days prior to surgery
    • Ticlopidine :
    • discontinue 7 days prior to surgery
  • 22.
    • Physical findings :
    • Neck:
    • Carotid bruits,
    • Increased JVP
    • Pulmonary :
    • Wheezes
    • Rales
    • Rhonchi
    • Distant breath sounds
    • Barrel chest
  • 23.
    • Cardiovascular :
    • Check for regular vs irregular rhythm
    • Presence of S3 or S4
    • Murmurs
    • Displaced apical impulse
  • 24.
    • » Abdomen
    • Bruits
    • Pulsatile masses
    • Obesity
    • » Extremities
    • Diminished/absent lower
    • extremity pulses
    • Nonhealing ulcers
    • Distal embolic phenomena
  • 25. Work up:
    • Functional status/ exercise tolerance :
    • severity of cardiopulmonary status
    • ECG
    • TTE, TEE
    • DSE
    • Thallium scanning
    • CAG
  • 26.
    • Carotid USG
    • ( H/o stroke/ TIA )
    • PFT/ ABG :
    • in pts with moderate to
    • severe pulmonary disease
    • PFTs may help guide preop
    • medical therapy for optimal
    • pulmonary status & estimate risk
  • 27. LABS
    • CBC
    • BUN, creatinine
    • PT/PTT
    • Electrolytes for pts on diuretics, ACE inhibitors, or history of renal insufficiency or failure
    • HbAIc
  • 28.
    • Surgeon orders
    • CT scan with contrast or
    • MRA to evaluate :
    • the extent of the aortic disease,
    • position [infra- or suprarenal],
    • diameter,
    • involvement of mesenteric
    • vessels
  • 29. Intra op:
    • ECG : II, V5, V6 with ST analysis
    • ABP, CVP
    • Two large-bore peripheral IVs
    • (or central introducer sheath)
    • Additional monitors: TEE, PAC
    • Thromboelastography:
    • demonstrates both hypercoagulability and fibrinolysis, which are frequently
    • underestimated with conventional coagulation tests
  • 30. Intraop concerns:
    • Maintenance of hemodynamic stability:
    • » Close titration of IV
    • & inhalation agents :
    • emphasis on hemodynamic
    • stability, not speed of onset
    • » Thiopental, propofol, etomidate,
    • narcotics, benzodiazepines,
    • inhalationals used successfully
  • 31.
    • Esmolol & nitroglycerin may be useful for hemodynamic mgt of hypertension/tachycardia
    • Esmolol or opioids may be necessary to blunt the pt's response to tracheal intubation
    • Maintaining HR & MAP within 20% of baseline is generally appropriate; agents should be readily available
    • Muscle relaxation is necessary for surgical exposure/ conditions
  • 32.
    • Obtain baseline ABG & ACT
    • Keep blood products in the OR
    • in case of significant hemorrhage
    • Avoid hypothermia by
    • warming IV fluids &
    • using forced air warming
  • 33. Cross clamp!
    • Cross-clamping of the aorta : significant cardiac stress
    • » Acute left ventricular strain produces a major cardiovascular stress; magnitude is related to clamp position
    • MAP may increase only 2% with infrarenal
    • 5% with suprarenal
    • up to 54% with supraceliac placement
  • 34.
    • Preload & afterload may increase
    • Ejection fraction may decrease.
    • This may lead to myocardial ischemia in pts with significant CAD
  • 35.  
  • 36.  
  • 37.  
  • 38.
    • Mgt of hemodynamic changes with aortic cross-clamp :
    • » NTG, beta blockers and/or sodium nitroprusside
    • » Increasing anesthetic depth
    • » Anticipation of the increase in SVR is important
    • » Some vascular surgeons clamp the iliac arteries first to prevent distal embolization due to the aortic clamp
  • 39.
    • Other changes with aortic cross-clamp :
    • » Ischemia/ hypoperfusion of the kidneys, abdominal viscera, spinal cord, limb
    • » Accumulation of acid metabolites in tissues & vasculature below the level of the clamp
  • 40.
    • Anticipation of clamp removal is important.
    • » Prior to clamp removal, increase preload.
    • increasing the PCWP (if PAC used) by 3-4 mmHg above baseline
    • » Discontinue agents such as NTG, nitroprusside & esmolol
    • » Don’t decrease anesthetic depth
    • » Agents such as phenylephrine, ephedrine & epinephrine can be used
  • 41.
    • Raising BP 20-30% above baseline with such agents prior to clamp release is often necessary to avoid significant hypotension
    • Duration & location of the aortic clamp determine the degree of hypotension observed
    • A supraceliac clamp can result in significant bowel & liver ischemia; decrease in SVR & CO after release of such a clamp can be significant
  • 42.
    • • Upon unclamping, acidic metabolites from the ischemic tissues below the clamp are washed back into the circulation
    • » Make prophylactic ventilatory adjustments to accommodate this increased acid load
    • » Frequent ABGs
    • » buffer therapy withbicarbonate or THAM ( trome
    • Thiamine 0.3M)
    • » After unclamping, reverse heparin
    • Discuss timing of reversal with surgeon.
  • 43.  
  • 44. Post op:
    • ICU care, intubated & careful cardiac monitoring
    • Rewarming
    • Watch for bleeding
    • Urine output!
  • 45.
    • Aggressive pain management:
    • Epidural LA &/or narcotics,
    • IV Narcotics,
    • Avoid NSAIDs please!
    • PCA
  • 46.
    • * increased pain & anxiety  catecholamine release  increased myocardial oxygen demand & ischemia
    • With good pain relief, recovery of pulmonary function is improved
    • Epidural Analgesia Reduces Postoperative Myocardial Infarction: A Meta-Analysis
    • (Beattie WS et al., Anesthesia analgesia 2001, 93 (4)853-8)
  • 47. Renal insufficiency:
    • Incidence : 20-25%
    • Renal medulla more susceptible
    • The pathogenesis is multifactorial:
    • Preoperative renal function
    • The use of nephrotoxic drugs,
    • contrast medium
    • Embolic
  • 48.
    • Hypotension
    • Ligation of the left renal vein during the procedure
    • Temporary suprarenal aortic clamping 
    • renal ischemia,
    • if limb ischemia  muscle necrosis and myoglobinuria  acute tubular necrosis
  • 49. Renal protection
    • Maintain adequate intravascular volume
    • Maintain CO
    • Use endovascular technique
    • Avoid nephrotoxins
    • NSAIDs, aminoglycosides,
    • ACE inhibitors, ARBs
    • Cross clamp time <50 min
    • Other techniques
    • Mannitol, loop diuretics,
    • Fenoldopam,low dose dopamine!?
  • 50. Myocardial protection:
    • Preop use of β-Blocker
    • Preop statins
    • Endovascular vs open technique
    • Reduce blood pressure before X clamp
    • SNP to unload heart & reduce wall tension
  • 51. Ruptured AAA!
    • Very fatal
    • overall mortality rate : 65%
    • Mortality rate for patients
    • who survive to reach hospital
    • & undergo emergency surgery : 36%,
    • 6% for elective repair
  • 52.
    • Mortality if ruptured:
    • Before reaching the hospital : 27 – 50%
    • In hospital mortality before operation: 24 – 58%
    • Perioperative mortality : 42 – 80%
    • Overall mortality about 80%
  • 53.
    • The risk of spontaneous rupture depends on aneurysm size
    • <1% per annum for AAA <55 mm diameter
    • >17% per annum for aneurysms >60 mm diameter
  • 54. Distribution sites of AAA rupture:
    • Right lateral wall - 28%
    • Pelvic arteries - 22%
    • Posterior wall - 19%
    • Left lateral wall - 17%
    • Anterior wall - 10%
    • Suprarenal - 4%
    • (Stavropoulos SW, Charagundla SR. Imaging techniques for detection and management of endoleaks after endovascular aortic aneurysm repair.  Radiology . Jun 2007;243(3):641-55 )
  • 55. Estimated Annual rupture risk
  • 56.  
  • 57. Risk stratification:
    • Several scoring systems available
    • scoring systems have their limitations
    • should only be used to supplement clinical judgment
    • May be used to compare results from different centres
    • POSSUM ( P hysiological & O perative S everity S core for en U meration of M orbidity & M ortality )
    • APACHE II
    • Hardman Index
    • Glasgow Aneurysm score
  • 58. Hardman Index! Hardman index: 1 point is assigned for each preoperative variable present, so the possible score ranges from 0–5. A total score of 2 is consistent with a mortality rate of 80%. Points 1 Age> 76 1 Creat > 190 umol/L 1 Hb < 9gm% 1 MI on ECG 1 H/o LOC on hospital arrival
  • 59. Glasgow Aneurysm Score(GAS) Points Age of patient ( point= no. of yrs) 17 Shock 7 Myocardial disease 10 Cerebrovascular disease 14 Renal disease
  • 60.
    • Recent data suggest that the GAS is useful in predicting postoperative mortality in both elective and emergency AAA repair
    • postoperative mortality was 1.4% in patients with a GAS of 78.8 and 8.7% in those with a GAS of 78.8 following elective repair
    • (Biancari F, Leo E, Ylo¨nen K, Vaarala MH, Rainio P, Juvonen T. Value of the Glasgow Aneurysm Score in predicting the immediate and longterm outcome after elective open repair of infrarenal abdominal aortic aneurysm. Br J Surg 2003; 90: 838–44)
  • 61. Predictors of early mortality
    • Loss of consciousness in hospital,
    • Cardiac arrest,
    • Systolic BP < 80 mm hg
  • 62. Surgical complications
    • lumbar muscle rhabdomyolysis,
    • anastomotic bleeding,
    • coagulopathy,
    • renal dysfunction/failure,
    • visceral ischemia & infarction, ileus
    • lower extremity ischemia/emboli,
    • spinal cord ischemia/injury
  • 63.
    • The incidence of spinal cord injury is reported to be 0.15% in unruptured AAA repair
    • The artery of Adamkiewicz arises from above L3 in most people
    • clamping at or above this level increases the risk of spinal cord injury
  • 64. Spinal cord protection:
    • Paraplegia results from :
    • prolonged spinal cord ischemia,
    • disruption or embolization of
    • radicular blood supply during
    • aneurysm repair ( usually TAA/ TAAA)
    • Prevention:
    • Steroids, magnesium, intrathecal papaverine
    • injection,epidural cooling,
    • systemic hypothermia
  • 65. Most common :- LUMBAR DRAIN!
  • 66.
    • Patients are particularly prone to developing intra-abdominal hypertension (intra-abdominal pressure > 12 mmHg) and abdominal compartment syndrome (ACS, defined as IAP 20 mmHg)
  • 67. Factors causing ACS:
    • prolonged hypotension,
    • cardiopulmonary resuscitation,
    • hypothermia,
    • severe acidosis (base deficit < 14 mEq),
    • Aggressive fluid resuscitation
    • Prolonged ileus
  • 68.
    • Consider laparastoma or mesh closure of the abdominal wall with delayed secondary surgical closure after 2–3 days
    • Mesh closure : reduces the incidence of multiorgan failure when compared with patients who require a second operation for ACS in the postoperative period
    • Monitoring of IAP should be considered in all patients and consideration given to parenteral nutrition if ileus is prolonged
  • 69. Surgical concerns
    • • Aneurysm rupture prior to cross-clamp placement
    • Aneurysmal involvement of renal or mesenteric arteries
    • Duration of cross-clamping & consequent ischemia
    • Renal ischemia & consequent dysfunction
    • Spinal cord ischemia
  • 70.  
  • 71. Advantages & disadvantages of EVAR
  • 72. Anesthetic technique in EVAR:
    • LA,
    • GA ( LMA, ETT),
    • Regional ( SAB, Epidural, CSE )
    • There is no evidence to suggest that outcome is better/ worse with any of the type of anesthesia management
  • 73. Complication of EVAR: ( device related )
    • Graft migration,
    • Graft kinking,
    • Endoleak
    • STABLE PROXIMAL FIXATION :
    • key to prevent above complication
  • 74. Procedure relate EVAR complications:
    • Dissection,
    • malpositioning,
    • renal failure,
    • thromboembolizaton,
    • Ischemic colitis,
    • Groin hematoma,
    • wound infection
  • 75. Systemic complications of EVAR:
    • Myocardial infarction,
    • congestive heart failure,
    • arrhythmias,
    • respiratory failure,
    • renal failure
  • 76. Statistics
    • Conversion of EVAR to open: 1.9 - 4.8%
    • Periop mortality in EVAR: 1.2%
    • in open : 4.8%
    • Late mortality:
    • rupture with EVAR : 1.8%
    • in open : 0.5%
    • Laparotomy related complications:
    • in EVAR : 8.1%
    • in open : 14.2%
    (Endovascular vs open repair of AAAs in Medicare population. Schermerhan etal. N Engl J Med 2008; 358: 464-74.)
  • 77. Conclusion
    • As compared with open repair, EVAR of AAA is associated with lower short-term rates of death and complications
    • The survival advantage is more durable among older patients
    • Late reinterventions related to AAA are more common after endovascular repair
    • but are balanced by an increase in laparotomy-related reinterventions and hospitalizations after open surgery
  • 78.
    • THANK
    • YOU