Aortic aneurysms and anesthesia

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Aortic aneurysms and anesthesia

• Moderator Dr. Renu
• Presenters Dr. Dipal
• Dr. Mridu

www.anaesthesia.co.in anaesthesia.co.in_at_gmail.co
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• Sub acute aortic dissection
• Expanding aortic aneurysm

• Stable aortic aneurysm
• Coarctation of aorta
• Atherosclerotic disease

• Bioprosthetic valve
• Graft failure
• Progression
• Pseudo aneurysm

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Anatomy of aorta
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Aortic Aneurysm

• Definition
• Dilatation of aorta containing all the 3 layers
  of the vessel wall that has diameter of at least
  1.5 times that of the expected normal diameter of
  that given aortic segment.
• I 5.9/100000
• Age 65 yrs n above
• M gt F

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Pseudo aneurysms

• Localized dilatation
• Wall not all 3 layers, clots, connective
  tissue, surrounding tissue
• Cause
• contained rupture of aorta
• intimal disruptions
• penetrating atheromas
• partial dehiscence of suture line

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Risk factors

• Hypertension
• Hypercholesterolemia
• Prior tobacco use
• Collagen vascular disease
• Family history
• Smoking
• Diabetes mellitus
• Male
• Obesity

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Classification

• Etiology
• Atherosclerosis
• most common
• cystic medial necrosis
• descending distal to L Subclavian A, large and
  medium size vessels
• Theories Inflammation, CRP, IL-6, Aspirin,
  Statins, cholesterol, estrogen, antioxidants,

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Classification contd..

• Annuloaortic ectasia AR, younger age
• Syndromes Marfans, Ehler-Danlos, Turner
• Familial 19, younger
• Inflammatory giant cell arteritis, mycotic,
  takayasu, syphilis
• Aortic dissection
• Trauma deceleration, partial/ complete
  transection at isthmus, saccular, discrete

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Classification contd..

• Location
• Aortic root and Ascending aorta 60
• AR, bicuspid aortic valve
• Descending aorta 40
• endovascular
• Arch of aorta 10
• cerebral protection
• Thoracoabdominal 10,
• paraplegia, multiple segments

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Classification contd..

• Shape
• Fusiform common
• atherosclerosis/ CVD
• longer segment
• dilation of entire segment
• Saccular localized
• isolated segment
• localized out pouching
• Size physiologic effect,
  consequences

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Clinical manifestations

• Most asymptomatic
• Incidental x-ray, ct scan, echo
• AR
• CHF
• Mass effect trachea/ main stem bronchus,
  pulmonary veins, esophagus, rln, bone
• Pain due to dissection/rupture
• Pulsatile mass in epigastrium

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Diagnosis

• X-ray chest mediastinal widening, tracheal
  deviation
• CECT confirm, size, suprarenal
• CT angiography
• MR angiography aortic root
• Transthoracic ECHO aortic root, not mid/ distal
  ascending aorta, marfan
• Transesophageal ECHO
• USG screening AAA

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Screening

• Recommended
• all men 60-85 yrs
• all women 60-85 yrs with CVS risk factors
• both with family history and age gt50yrs

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Medical management

• Inform and warn
• Discontinue smoking
• Avoid heavy lifting/straining
• ß blockers
• Statins
• ACE inhibitors
• Antihypertensives 105-120 mmHg
• Familial screening
• Serial imaging 6mths, 1yr.

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Indications for repair

• Symptoms refractory to medical treatment
• Evidence of rupture
• Increase in diameter 1cm/yr
• Diameter ascending aorta5.5cm (5cm)
• descending aorta6.5cm (6cm)
• Severe aortic regurgitation

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Indications for repair contd..

• Aortoannular ectasia with dilated aortic root
• Congenital bicuspid aortic valve4cm
• Contained or impending rupture
• Earlier marfans, family history of dissection/
  aortic disease

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Pre existing medical illness

• Aortic valve disease
• Cardiac tamponade
• PVD embolus, ischemia, stroke
• CVD failure, ischemia, infarction, arrthymias,
  pulmonary edema
• Cardiomyopathy/ valvular disease
• Cerebrovascular disease

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Pre existing medical illness contd..

• Pulmonary disease postop failure, pneumonia
• Renal insufficiency fluid, drugs
• Esophageal disease TEE
• Coagulopathy ? bleeding, transfusion, hggic cx,
  epidural, CSF drainage
• Prior aortic operations

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Airway assessment

• Cervical spine TEE
• Large airways mass effect difficult intubation,
  OLV, airway compromise

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Perioperative morbidity

• Non fatal and fatal MI 4.9 and 2.3
• Long term MI 8.9 and 9.1
• Coronary artery revascularization and prophylaxis
  trial
• ACC/AHA guidelines

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Assessment of cardiovascular risk

• ECG
• Baseline
• Prior MI risk stratification
• Dysrhythmias other than sinus risk
• Lacks sensitivity

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Assessment of cardiovascular risk

• Exercise ECG
• 30-70 cannot reach target HR
• Poor functional capacity, ß blocker etc
• If 85 of predicted maximal HR achieved low risk
• Arm exercise fatigue precedes increase

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Assessment of cardiovascular risk

• Myocardial perfusion imaging
• DTI most common, non invasive, RR 4.6
• 2 images, steal phenomenon
• 3 outcomes normal, myocardium at risk, fixed
  perfusion defect
• Eagle et al and Litalien et al no additional
  stratification for pts classified as low or high
  risk. Classified 80 of intermediate risk into
  low or high risk.

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Assessment of cardiovascular risk

• Ambulatory ECG monitoring
• RR 2.7
• Detect dysrythmias
• Sensitivity in pts with high pretest probability
• 80-90 MI silent periop morbidity
• Low cost
• Not in LBBB, pacemaker dependency, LVH,
  significant strain or digitalis

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Assessment of cardiovascular risk

• Echocardiography
• With 5 or gt abnormal segments 4-6 fold ? risk of
  cardiac Cx
• Stress echocardiography
• TEE superior to transthoracic
• DSE sensitivity and specificity 80-90
• Stratifies pts only with risk factors
• Pericardiac events unlikely if result ve
• Best predictor RR 6.2

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Assessment of cardiovascular risk

• Radionuclide ventriculography
• LVF at rest or exercise
• RR 3.7
• Independent predictor of periop cardiac morbidity
• EF lt 35 75-85 MI risk
• gt35 19-20
• However limited use

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Assessment of cardiovascular risk

• Summary
• DTI, AECG, DSE high negative predictive value
• Low risk not 0 risk
• Negative result does not guarantee pt has no CAD
• None has high positive predictive value

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Assessment of pulmonary risk

• COPD, smoking, chronic bronchitis
• ABG baseline PACO2 gt 45 higher risk
• PFT FEV1lt1lit/ MBClt50
• Steroids short course helpful in copd/ asthma
• May benefit from epidural analgesia and
  anesthesia

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Assessment of renal function

• HTN, atherosclerosis, diabetic nephropathy, renal
  artery stenosis
• Pre and intraop dye loads nephrotoxic
• Aortic cross clamping? bld flow
• Embolic plaque
• Fluctuations in CO and intravascular vol
• ARF abt 7

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Assessment of renal function

• Preop ARF most imp predictor of postop ARF
• Pathogenesis ATN
• Clamp
• distal to Subclavian A 85-94? in bld flow
• Infrarenal gt30?
• S. Creat gt 2 mg high risk

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Pre-anesthetic assessment

• Urgency of operation
• Pathology and extent of disease
• Median sternotomy/ thoracotomy/ endovascular
  approach
• Mediastinal mass effect
• Airway compromise/ deviation

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Preoperative medications

• All cardiac, antihypertensive, pulmonary,
  antiseizure to continue
• OHA discont, metformin(48hrs prior)
• Insulin 1/3rd ½ usual dose
• Warfarin 3-7 days prior, INR
• Heparin infusion
• Aspirin, clopidogrel Ticlopidine
• Anxiolytics BDZ/opioids

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General Anesthetic management

• Haemodynamic monitoring
• Neurophysiologic monitoring
• OLV for thoracotomy
• Bleeding potential
• Antibiotic prophylaxis
• Temperature monitoring
• Blood sugar monitoring

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Haemodynamic monitoring

• ECG
• IBP proximal aortic pressure
• R radial- Innominate A, BP repair of arch/ prox
• L radial A ACP, B/L
• Femoral distal aortic pressure, avoided in PVD
• CVP RAP, vasoactive drugs
• PAC PAP, CO, mixed Svo2, (CPB, DHCA, partial
  LSHB, aortic-cross clamping)
• TEE ventricular ft

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Neurophysiologic monitoring

• To monitor for intraop spinal ischemia
• SSEP
• MEP
• EEG
• Jugular venous oxygen saturation
• Lumbar CSF pressure
• Body temperature

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SSEP

• Electrical stimuli to peripheral nerves and
  record evoked potential at peripheral nerves,
  spinal cord, brainstem, thalamus, cerebral cortex
• ?/ disappearance of amplitude in LL v/s UL
• Balanced anesthesia technique, MAC lt0.5
• Monitors only posterior column not motor

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MEP

• Paired stimuli to scalp and record evoked
  potential in anterior tibialis muscle
• ?/ disappearance of amplitude in LL v/s UL
• TIVA without N-M blockade

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Temperature monitoring

• Core
• Urinary catheter with temp probe
• PAC probe
• Nasopharyngeal probe
• Rectal probe

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OLV

• L thoracotomy or L thoracoabdominal approach of
  TAAA
• Adv improves surgical exposure
• ?lung contusion or torsion
• protects R lung in bleeding
• DLT/ BB
• Advantages and disadvantages of each
• If DLT- exchange at the end of Sx

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Bleeding potential

• Increased risk
• Intrinsic disease
• Vascular anastomosis
• Extracorporeal circulation
• Hypothermia

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Bleeding potential contd..

• Strategies
• Discontinue anticoagulants/antiplatelets
• Large bore i.v. access
• Immediate availability of blood products
• Fluid warming unit
• Urine output monitoring
• Precise control of BP
• Cell salvage
• Bio glue
• Antifibrinolytics e-aca, traxenamic acid
• Factor VII A

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Drugs

• Vasopressors and vasodilators
• Etomidate haemodynamic stability
• Narcotics, NMDR, inhalational
• Doses ? 30C, stopped18C, resumed at rewarming
• EEG/ SSEP barbiturates/ propofol avoided,
  inhalational 0.5 MAC
• MEP TIVA

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Ascending TAA

• Mortality 3-5
• Median sternotomy
• TEE valve sparing Sx, diameter, AR post repair
• CPB
• Wheat procedure AVR tube graft
• Bentall procedure AVR
• Ross procedure PV-gt AV
• Carbol technique coronary reimplantation

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Arch aneurysms

• Cerebral protection embolus, ischemia
• DHCA
• Trifurcated tube grafts
• Elephant trunk procedure

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Descending TAA

• Mortality 4
• Lateral thoracotomy/ thoracoabdominal incision
• Cross clamping/ partial L heart bypass/ DHCA
• Spinal cord, mesenteric, LL protection
• Endovascular stent grafts

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Staged repair

• Multiple segments
• Greater risk of rupture
• Placing of clamps
• Elephant trunk procedure

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Abdominal AA

• Mortality 4-6 (elective), 2 in low risk
• Elderly
• Atherosclerosis, coexisting illness
• Risk of rupture 3 times gt F, smokers, HTN, rapid
  rate of expansion
• Classification with and without dissection

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Crawford classification of TAAA
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Abdominal AA contd..

• Renal, Mesenteric, LL, Spinal Cord ischemia
• Monitoring
• Fluid management
• Epidural analgesia
• Cross clamping/ Gott shunt/ DHCA
• Endovascular stent grafts
• Infrarenal good survival

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Aortic clamping

• Mortality and paraplegia related to
• position and length of resected aorta
• condition of pt
• duration 30 min

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• AoX

Passive recoil distal to clamp
Catecholamines (and other vasoconstrictors)
Impedance to Ao flow
Active vasoconstriction proximal and distal to
clamp
R art
Preload
Coronary flow
Afterload
Contractility
If coronary flow and contractility do not increase
If coronary flow and contractility increase
CO
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Haemodynamic changes

• ?BP
• ? Segmental wall motion abnormalities
• ? Left ventricular wall tension
• ? Ejection fraction
• ? Cardiac output
• ? Renal blood flow
• ? Pulmonary occlusion pressure
• ? CVP
• ? Coronary blood flow

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Metabolic changes

• ? Total body oxygen consumption
• ? Total body CO2 production
• ?Mixed venous O2 saturation
• ? Total body oxygen extraction
• ? Epinephrine , nor epinephrine
• Respiratory alkalosis
• Metabolic acidosis

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change in CVS variables
Variable Supraceliac Suprarenal-infraceliac Infrarenal
Mean BP 54 5 2
PCWP 38 10 0
End Dia.Area 28 2 9
End Sys.Area 69 10 11
E.F. -38 -10 -3
Pt. with wall motion abn. 92 33 0
new MI 8 0 0
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Therapeutic interventions

• Afterload reduction
• SNP
• Inhaled anesthetics
• Amrinone
• Shunts and aorto-femoral bypass
• Preload reduction
• NTG
• Controlled phlebotomy
• Atrial to femoral bypass

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Therapeutic intervention

• Renal protection
• Fluid administration
• Distal aortic perfusion techniques
• Mannitol
• Drugs to augment renal perfusion
• Other changes
• Hypothermia
• ? Minute ventilation
• Sodium bicarbonate

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Aortic unclamping
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Haemodynamic changes

• ?Myocardial contractility
• ? BP
• ?PAP
• ? CVP
• ? Venous return
• ? CO

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Metabolic changes

• ?Total body oxygen consumption
• ? Lactate
• ? Mixed venous O2 saturation
• ? Prostaglandins
• ? Activated complement
• ? Myocardial depressant factors
• ? Temperature
• Metabolic acidosis

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Therapeutic interventions

• ? Inhaled anesthetics
• ? Vasodilators
• ?Fluid administration
• ? Vasoconstrictor drugs
• Reapply cross clamp for severe hypotension
• Consider mannitol
• Consider sodium bicarbonate

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Endovascular stent graft repair

• Fabric/ synthetic tube grafts reinforced by a
  wire frame
• Requires 1 cm long non-tapered region of aorta on
  either end of aneurysm for landing

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Endovascular stent graft repair

• Intraop angiography/ TEE
• Long term benefits to be determined
• Problems
• vessel injury
• intravascular migration
• strut
• postop paraplegia
• intravascular leaks

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Hypertension

• Moderate not independent risk factor
• Continue them prevent rebound increase in HR,
  BP, avoid withdrawal
• Clonidine ? anesthetic req, catecholamine
  levels, BP lability
• CCB MI not affected
• ACE inhibitors intraop hypotension, avoided
• Shorter acting drugs

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ß- blockers

• ? mortality and morbidity with silent MI, acute
  MI, CHF
• Prevention of catecholamine induced arrhythmia,
  plaque disruption
• Blunting neurohumoral and haemodynamic effects of
  sympathetic stimulation
• ACC/ AHA level I recommendation

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Pre-op CVS assessment

• ACC/AHA Guidelines for periop CVS evaluation for
  noncardiac surgery
• Functional activity
• Clinical predictors of risk
• Deg of surg. stress

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ACC-AHA Guidelines.

• Functional capacity
• Metabolic equivalent (MET)
• 1 MET- 02 (Vo2) consumption of a 70kg man in a
  resting state (3.5 ml/kg/min)
• MET- daily activities
• Excellent (gt10 METS)
• Good (7-10 METS)
• Moderate (4-7 METS)
• Poor (lt4 METS)

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Estimated Energy Requirements for Various
Activities
1 MET Can you take care of yourself? 4 METs Climb a flight of stairs or walk up a hill?
Eat, dress, or use the toilet? Walk on level ground at 4 mph or 6.4 km/hr?
Walk indoors around the house? Run a short distance?
Walk a block or two on level ground at 2-3 mph or 3.2-4.8 km/hr? Do heavy work around the house, such as scrubbing floors or lifting or moving heavy furniture?
4 METs Do light work around the house, such as dusting or washing dishes? Participate in moderate recreational activities such as playing golf, bowling, dancing, playing doubles tennis, or throwing a baseball or football?
10 METs Participate in strenuous sports such as swimming, singles tennis, football, basketball or skiing?
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Clinical Predictors of Increased Perioperative
Cardiovascular Risk

• Major
• Unstable Coronary Syndromes
• Recent myocardial infarction with evidence of
  important ischemic risk by clinical symptoms or
  non-invasive study
• Unstable or severe angina (Canadian class III or
  IV)
• Decompensated congestive heart failure
• Significant dysrhythmias
• High-grade atrioventricular block
• Symptomatic ventricular dysrhythmias in the
  presence of underlying heart disease
• Supraventricular dysrhythmias with uncontrolled
  ventricular rate
• Severe valvular disease

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Clinical Predictors of Increased Perioperative
Cardiovascular Risk (Contd.)

• Intermediate
• Mild angina pectoris (Canadian Class I or II)
• Prior myocardial infarction by history or
  pathologic Q waves
• Compensated or prior congestive heart failure
• Diabetes mellitus
• Renal insufficiency
• Minor
• Advanced age
• Abnormal ECG (left ventricular hypertrophy, left
  bundle-branch block, ST-T abnormalities)
• Rhythm other than sinus (e.g. atrial
  fibrillation)
• Low functional capacity (e.g., inability to climb
  one flight of stairs with a bag of groceries)
• History of stroke
• Uncontrolled systemic hypertension

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High Risk (Reported Cardiac Risk Often gt5) Emergent major operation, particularly in the elderly
High Risk (Reported Cardiac Risk Often gt5) Aortic and other major vascular procedures
High Risk (Reported Cardiac Risk Often gt5) Peripheral vascular surgery
High Risk (Reported Cardiac Risk Often gt5) Anticipated prolonged surgical procedures associated with large fluid shifts and/or blood loss
Intermediate (Reported Cardiac Risk Generally lt5) Carotid endarterectomy
Intermediate (Reported Cardiac Risk Generally lt5) Head and neck surgery
Intermediate (Reported Cardiac Risk Generally lt5) Intraperitoneal and intrathoracic procedures
Intermediate (Reported Cardiac Risk Generally lt5) Orthopedic surgery
Intermediate (Reported Cardiac Risk Generally lt5) Prostate Surgery
Low Risk (Reported Cardiac Risk Generally lt1) Endoscopic procedures
Low Risk (Reported Cardiac Risk Generally lt1) Superficial procedures
Low Risk (Reported Cardiac Risk Generally lt1) Cataract removal
Low Risk (Reported Cardiac Risk Generally lt1) Breast Surgery
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CNS

• h/o TIA or stroke Duplex imaging of Carotid A
  and angiography of Brachiocephalic and
  Intracranial A if gt80-90stenosis of one or
  both
• Consider Carotid Endarterectomy before elective
  operation.

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BP

• Proximal maintain 100mmHg
• Can upto 180-200 if no CI(intracranial hgge) and
  if acceptable operating conditions.
• Relative hypotension(lt20 of resting pressure)
  should be avoided unless shunts used to perfuse
  lower parts of body.
• Distal pressure maintain at 50mmHg