ANAESTHESIA_FOR_SUPRA_DIAPHRAGMATIC__AORTIC_ANEURYSM[1].pptx

Anaesthesia for thoracic aneurysms

1. SPEAKERS: dr MD HAMED ALI dr SUPRAJA MODERATOR: Dr K. DILIP KUMAR ANAESTHETIC MANAGEMENT OF SURGERY FOR AORTIC ANEURYSMS

2. INTRODUCTION : Largest artery of body Thoracic and Abdominal part Aortic root Ascending aorta Aortic arch Descending aorta Supra-renal part Infra-renal part isthmus CIA

3. layers of the aortic wall Three layered: thin intima, thick media and thin adventitia Media comprises 80% aortic thickness , arranged spirally with intertwining layers of elastic tissue Adventitia contains collagen and vasa vasorum which nourishes aortic wall Vasa- vasorum is absent infra renal- --- frequency of infrarenal aortic aneurysm is high.

4. AORTIC ANEURYSMS: The term ANEURYSM is derived from the Greek word ANEURYSMA meaning “ a widening”. An aneurysm is a permanent dilatation of all three layers of an artery , which appears ballooned in a certain region like aorta . Second most frequent disease of aorta after atherosclerosis 50% increase in diameter compared with normal or >3 cm in diameter . Normal arterial diameter is dependent on age, gender, body size and other factors. Most common cause of death is rupture of aneurysm.

5. CLASSIFICATION : True aneurysm- contains all layers of arterial wall. Dilatation covered by thick fibrinous capsule. Injury to wall of vessel allows blood to escape from vessel into adjacent tissue . Extravasated blood coagulates and becomes a mass along side the vessel. True aneurysm False/Pseudoaneurysm

6. BASED ON MORPHOLOGY: Circumferential enlargement involving all layers of the artery wall. Affecting only part of the arterial circumference FUSIFORM ANEURYSM SACCULAR ANEURYSM : BERRY ANEURYSM : Weakness in the wall of cerebral arteries. DISSECTING : Tear in the wall of aorta and blood deposits in between them.

7. Based on location: ABDOMINAL AORTA 65% THORACIC AORTA 19% ABDOMINAL AORTA + ILIAC 13% THORACOABDOMINAL 2% ISOLATED ILIAC 1% POPLITEAL 70% FEMORAL together make up to 90% CAROTID 4 % SUBCLAVIAN 2% CEREBRAL 2% SPLENIC 1% MESENTRIC 0.5% RENAL 0.5%

8. Crawford classification Extent I: from the left subclavian artery to below the diaphragm Extent II: from the left subclavian artery to the aortic bifurcation Extent III: from the lower half of the descending thoracic aorta extending to the aortic bifurcation Extent IV: disease confined to the abdominal aorta

9. MODIFIED TAA classification: Extent I: from the left subclavian artery to below the diaphragm Extent II: from the left subclavian artery to the aortic bifurcation Extent III: from the lower half of the descending thoracic aorta extending to the aortic bifurcation Extent IV: disease confined to the abdominal aorta Extent V : from 6 th intercostal space to above the renal arteries. Most difficult to repair

10. THORACIC ARTERY ANEURSYMS Incidence – 5-10 per 100,000 Aortic root and ascending aorta – 60% Descending aorta – 35% Thoracoabdominal aorta -10% Aortic arch -<10%

11. Risk Factors: Atherosclerosis (90%) . Familial History- 20% of patients with AAA have 1 st Degree relative . Gender - Males > Females . Connective tissue disorders. Infections : Non infectious aortitis : giant cell arteritis, IGg4 disease, Marfans syndrome Loeys -Dietz syndrome Ehler danlos syndrome Diabetes . Hypertension Emphysema Smoking . Hyperlipidemia Older Age . Syphilis Turners syndrome Bicuspid aortic valve Bacterial and mycotic aortitis

12. PATHOGENESIS AORTIC WALL INFLAMMATION INFILTRATION OF MEDIA WITH LEUKOCYTES,MAST CELLS INCREASED LOCAL RELEASE OF PROTEASES IMBALANCE BETWEEN DEGENERATION AND REGENERATION PROCESS MECHANICAL FAILURE OF MEDIAL ELASTIN AND ADVENTITIAL COLLAGEN ANEURYSMAL DILATATION AND RUPTURE

13. Signs and symptoms: Mostly asymptomatic . Hoarseness ( stretching of left recurrent laryngeal nerve ) Stridor ( compression of trachea ) Dysphagia ( compression of esophagus ) Dyspnoea ( compression of lungs ) Plethora & edema ( compression of superior vena cava ) Aortic regurgitation & C.C.F Rupture . Infection . Persistent chest or backpain .

14. Diagnosis: CHEST X RAY 2 D ECHO {TEE>TTE} C.T ANGIOGRAM M.R.I

15. DISSECTION: A dissection is disruption of intima with bleeding within the wall . Often associated with an increase physical activity or stress, leading to acute hypertension Intimal tear occurs in weakened aortic wall The usual cause of death is rupture of false lumen and fatal haemorrhage

16. CLASSIFICATION:

17. Table Applying Class of Recommendation and Level of Evidence to Clinical Strategies, Interventions, Treatments, or Diagnostic Testing in Patient Care CLASS (STRENGTH) OF RECOMMENDATION CLASS 1 (STRONG) Benefit >>> Risk Suggested phrases for writing recommendations: Is recommended Is indicated/useful/effective/beneficial Should be performed/administered/other Comparative-Effectiveness Phrases†: Treatment/strategy A is recommended/indicated in preference to treatment B Treatment A should be chosen over treatment B CLASS 2a (MODERATE) Benefit >> Risk Suggested phrases for writing recommendations: Is reasonable Can be useful/effective/beneficial Comparative-Effectiveness Phrases†: Treatment/strategy A is probably recommended/indicated in preference to treatment B It is reasonable to choose treatment A over treatment B CLASS 2b (Weak) Benefit ≥ Risk Suggested phrases for writing recommendations: May/might be reasonable May/might be considered Usefulness/effectiveness is unknown/unclear/uncertain or not well-established CLASS 3: No Benefit (MODERATE) Benefit = Risk Suggested phrases for writing recommendations: Is not recommended Is not indicated/useful/effective/beneficial Should not be performed/administered/other CLASS 3: Harm (STRONG) Risk > Benefit Suggested phrases for writing recommendations: Potentially harmful Causes harm Associated with excess morbidity/mortality Should not be performed/administered/other 18

18. Recommendations for Surgery for Sporadic Aneurysms of the Aortic Root and Ascending Aorta Symptomatic Asymptomatic Proceed to surgical repair (Class 1) Aneurysms of the aortic root or ascending aorta Diameter ≥ 5.5 cm Diameter <5.5 cm Maximum diameter of ≥5.0 cm Pt. height >1 SD above or below the mean and max. cross-sectional aortic area/height ratio of ≥10 cm2/m Aortic size index of ≥3.08 cm/m2 or aortic height index of ≥3.21 cm/m Confirmed rapid growth rate ( ≥0.3 cm/y over 2y OR ≥0.5 cm in 1y) Surgery is reasonable by experienced surgeons in a MAT (Class 2a) Surgery may be reasonable when performed by experienced surgeons in a MAT (Class 2b) Pt. undergoing repair or replacement of tricuspid AV with a concomitant aneurysm of the ascending aorta with max. diameter of ≥4.5 cm Ascending aortic replacement is reasonable by experienced surgeons in MAT (Class 2a) Pt. undergoing cardiac surgery for other than AV repair or replacement with aneurysm of the aortic root or ascending aorta and max. diameter of ≥5.0 cm Ascending aortic replacement may be reasonable (Class 2b) Abbreviations: AV indicates aortic valve; cm, centimeter; CT, computed tomography; y, year; MAT, multidisciplinary aortic team; max, maximal; pt , patient; SD, standard deviation; and y, year. 19

19. ANAESTHETIC MANAGEMENT OF THORACIC ANEURYSMS

20. PRE-OPERATIVE EVALUATION : Patients are generally elderly and may have co-morbidities which should be identified and optimised appropriately Assessment of functional capacity and reserve of each organ system for risk stratification and prediction of postoperative complications. Any history of previous cardiac, respiratory, renal, hepatic or neurological disease should be elucidated; Examination for evidence of compression of adjacent structures. Baseline neurological examination and recording of any existing neurological deficit C.B.C , COAGULATION PROFILE, R.F.T , L.F.T . Presence of pre-operative renal insufficiency and development of post-operative renal failure is associated with increased morbidity, mortality & neurological deficit . Liver dysfunction is associated with bleeding problems and increased mortality.

21. Pre-op C.T , M.R.I are used to know the extent and to plan the operative strategy. Assessment for coronary artery disease that may need to be dealt with simultaneously should be performed via coronary catheterisation or CT angiography Pulmonary function tests and room-air A.B.G are performed to evaluate respiratory reserve as one lung ventilation (OLV) is necessary for surgical exposure. Patients should stop smoking for at least 2 weeks before surgery and bronchodilator therapy maximized. Transesophageal echocardiography is used to evaluate ventricular function and concomitant valvular abnormalities .

22. Intraoperative management: Anaesthetic management of these patients is extremely challenging and requires skill and expertise in Haemodynamic monitoring; (ii) Patient positioning; (iii) OLV; (iv) Proximal and distal aortic perfusion management; (v) End-organ (renal, mesenteric and spinal cord) function monitoring and prevention of dysfunction; (vi) Massive blood loss and coagulopathy.

23. HAEMODYNAMIC MONITORING : Basic standard monitors are applied . Right radial or brachial artery catheter is required to assess B.P proximal to the aneurysm (the left subclavian artery may be compromised by the proximal cross-clamp.) The right femoral arterial pressure is monitored for distal perfusion. The left femoral vessels are needed for femoral bypass. Ventricular function can be monitored using a pulmonary artery catheter (PAC) and TOE. TEE dynamically monitors left ventricular (LV) function, confirms the diagnosis of any associated dissection, confirms correct position right atrial cannula, defines the quality of repair and assesses the adequacy of retrograde perfusion via femoro –femoral bypass. The left internal jugular vein is preferred for easy access under the drapes in the left lateral position.

24. Temperature monitoring : Lower extremeties should not be warmed as they have high metabolic rate during aortic cross clamp . Upper body warming blanket should be placed (avoid surgical site ). Temperature probes are placed in nasopharynx and rectum/bladder

25. Induction and maintainence Induction of anaesthesia and intubation must minimise undesirable increase in S.B.P as it may exacerbate an aortic dissection and rupture an aneurysm . Use of DLT permits collapse of the left lung and facilitate surgical exposure during resection of thoracic aneurysms Maintainence can be done with volatile anaesthetics and / opiods . It may cause reduction in cerebral metabolic rate which is desirable The choice of NMB agents depends on renal clearance . Patients undergoing thoracoabdominal aneurysm repair usually experience significant blood and fluid losses hence adequate fluid replacement should be done Urine output is monitored continuously .

26. Patient positioning: The left lateral decubitus position is used with a slight tilt to the left to access the femoral vessels for femoral–femoral bypass. After induction of anaesthesia and placement of invasive lines , the left femoral vessels are surgically exposed. The patient is then turned to the right and the arms, shoulder and knees are padded.

27. ONE LUNG VENTILATION Surgical access is best achieved via a left thoracotomy. Repair is greatly facilitated by using a double lumen tube (DLT). The right lung is isolated and protected in the event of an intrapulmonary bleed or rupture of the aneurysm into the left main bronchus. The ability to have the left lung collapsed improves visualization of the surgical field. This decreases the cross-clamp time, thereby reducing the likelihood of spinal cord, renal and visceral ischaemic injury It also reduces left lung retraction and trauma.

28. An aneurysm can distort the left main stem bronchus, which can make the usual left-sided tube positioning difficult; right-sided DLT placement may be required. Performing a fibreoptic bronchoscopy before insertion of the DLT can confirm distortion of the left main bronchus. Other methods for lung isolation like univent tubes and bronchial blockers can be used . At the end of surgery, provided there is no facial swelling, airway oedema or evidence of bleeding, the DLT should be changed for a single lumen tube. Leaving the DLT for 12–24 h is beneficial only if there is any possibility of re-exploration

29. SURGICAL TECHNIQUE: Exposure of the DTA is accomplished via a left thoracotomy usually between the 4th and the 5th ribs. For a full thoracoabdominal exposure, the incision begins above the symphysis pubis, goes midline to the umbilicus, and curves across the costal cartilage to the bed of the 6th rib. The surgical technique involves cross-clamps insertion above and below the lesion, opening of the aneurysm and replacing the aneurysm with a graft. Diaphragmatic preservation, defined as division of only the muscular portion with preservation of the tendinous portion of diaphragm, leads to early ventilator weaning

30. AORTIC CROSS CLAMP: Applying cross clamp on aorta leads to interruption of blood supply and is often a key step to allow a bloodless surgery. It leads to ischemia to parts of body distal to the clamp site . Upon release ,the blood flow is restored triggering an ischemic-reperfusion response.

31. Pathophysiology:

32. VISCERAL ISCHEMIA ↑ CELL MEMBRANE DISRUPTION BACTERIAL TRANSLOCATION/ RELEASE OF ENDOTOXIN ↑ SYSTEMIC INFLAMMATION HEMODYNAMIC INSTABILITY CARDIAC ARREST

33. TISSUE DISTAL TISSUE ISCHEMIA ↑ CELL MEMBRANE PERMEABILITY ↑ INFLAMMATORY MOLECULES ↑ R.O.S ACTIVATION OF CLOTTING PATHWAYS ↑ CATHECHOLAMINES CELL SWELLING IMPAIRED ANEROBIC METABOLISM ↑ PULMONARY RESISTANCE ↑ SYSTEMIC VASCULAR RESISTANCE MYOCARDIAL DYSFUNCTION V/Q MISMATCH PULMONARY HYPERTENSION

34. CROSS CLAMPING OF D.T.A produces proximal hypertension and distal hypotension . Cardiac filling pressures myocardial wall stress ,O2 consumption increases Cardiac output and ejection fraction decreases. The degree of hypertension depends on site of clamp, degree of collaterals, pre-occlusion aortic flow . A 40% rise in M.A.P is seen above the cross clamp & may increase I.C.P . To limit this there is reflex bradycardia, decreased contractility, peripheral vasodilation . Below the cross clamp there is 85% decrease in M.A.P , Decreased O2 consumption and conversion to anaerobic metabolism Renal and liver hypoperfusion leads to accumulation of lactic acid and may lead to metabolic acidosis and decreased urine output There is also increase in wall motion abnormalities (33%)

35. UNCLAMPING VOLUME SHIFT DISTAL TO AORTIC CLAMP CENTRAL HYPOVOLEMIA ↓ PRELOAD ↓ ARTERIAL PRESSURE ↓ CARDIAC OUTPUT ↓ AORTIC IMPEDENCE ↓ AFTERLOAD

36. REPERFUSION PLATELET AGGREGATION PMN ACTIVATION ↑ FREE RADICALS ↑R.O.S MICROVASCULAR DYSFUNCTION ↑PROTEOLYTIC ENZYMES COMPLEMENT ACTIVATION LIPID PEROXIDATION ENDOTHELIAL INJURY β ADRENERGIC SIGNAL IMPAIRMENT ↓ A.T.P ENZYME ACTIVATION ACTIVATION OF APOPTOSIS CELL/MITOCHONDRIAL SWELLING ↑VASCULAR PERMEABILITY INTERSTIAL EDEMA TISSUE HYPOXIA CELL MEMBRANE DAMAGE ↑CYTOKINES

37. MANAGEMENT: Before clamping: Deepen plane of anaesthesia (ISOFLURANE) Use of vasodilators (just before cross clamping ) Before clamping keep the patient in a slight hypovolaemic state . During clamping: Intravascular volume should be maintained and replaced to increase P.C.W.P . Esmolol infusion can be given . Fenoldopam can be used to improve renal blood flow Mannitol and furosemide can be used to stimulate urine output N.T.G can be used to decrease arterial B.P

38. Unclamping : Decrease the concentration of volatile anaesthetic agent . Stop all vasodilators . Volume loading . Infusion of vasoactive substances . Keep drugs like epinephrine , phenylephrine, calcium chloride , sodium bicarbonate ready . Treatment of metabolic abnormalities (↑ ventilation , sodium bicarbonate to counteract increased acid ) Gradual release of aortic clamp . Reapply clamp if severe and resistant hypotension. Look out of for any coagulation abnormalities .

39. Management of proximal and distal aortic perfusion: Simple aortic cross clamping Passive shunts Atriofemoral centrifugal bypass Partial cardiopulmonary bypass Deep hypothermic cardiac arrest

40. SIMPLE AORTIC CLAMPING : Clamping of D.T.A proximal and distal to aneurysm Shunt or pump is not used Advantage: Lower morbidity and mortality  surgery is expeditious Disadvantage: Distal organ ischemia  prolonged clamp times (>30 minutes)

41. PASSIVE SHUNTS: Divert blood from proximal to distal aorta GOTT shunt is the most commonly used heparin coated shunt . Proximal end of shunt is placed in ascending aorta (proximal DTA & aortic arch can also be used ) Advantages: Control proximal hypertension by decreasing afterload Maintain perfusion distal to clamp

42. Disadvantages: Technical difficulty. Bleeding . Dislodgement . Embolic stroke. Death. * Subclavian vein should be avoided as it may cause subclavian steal phenomenon *

43. ATRIOFEMORAL CENTRIFUGAL BYPASS / LEFT HEART BYPASS : M ost commonly used in TAA surgery. The bypass is established from the left atrium to the left common femoral artery with an interposed centrifugal pump. Centrifugal pumps are non-occlusive and non-traumatic to blood cells  require minimal or no heparin, provided that the flow is >800 ml/ min. The ACT should be maintained between 150 and 200 s. Advantages: decreases LV preload, CO, proximal aortic pressure and left ventricular stroke work.

44. Because about 50% of total CO is distributed to organs below the diaphragm  pump flow set @2-3L/min Bypass flow rates of 25-40ml/kg/min  to maintain a distal mean aortic pressure of 60–70 mm Hg. It may be useful in patients with Poor L.V function CAD Pre existing renal disease A nticipated pr olonged aortic cross clamp time .

45. PARTIAL CBP: (Femoral vein / right atrial – femoral artery bypass) It uses oxygenators and requires full heparinization . It is used in patients who require a long duration of aortic cross clamping Advantages: reduction of venous returns and C.O which helps in controlling hypertension . The arterial cannula in femoral artery provides distal perfusion to lower extremities , spinal cord , splanchnic viscera Disadvantages: Increased blood loss due to heparinization CPB related coagulopathy and haemorrhage from cannulation sites .

46. DEEP HYPOTHERMIC CIRCULATORY ARREST: It is used when there is difficulty in application of proximal aortic clamp The CMRO2 will decrease at lower temperature improving tolerance of ischemia . The use of DHCA to 15degree C can decrease spinal cord injury and renal failure compared with simple cross-clamping . The period of cerebral circulatory arrest should still be limited to 30–40 min to minimize the risk of cerebral injury.

47. Advantages: Minimal aortic dissection. Avoidance of cross clamping . Bloodless surgical field . Increased tolerable ischaemic time D isadvantage : Coagulopathy  increase in blood loss and transfusion requirements

48. End organ assessment and protection: Renal: The incidence of acute renal failure is 5–13% Acute tubular necrosis Risk factors: Increased cross-clamp time (>30 min) decreased renal blood flow reperfusion injury. Advanced age and preoperative renal dysfunction sustained perioperative hypotension and low CO failure to use atriofemoral bypass

49. Renal protective measures : Minimal cross-clamp times M aintenance of adequate intravascular volumes, CO and perfusion pressures. distal perfusion and hypothermia (both selective renal and systemic ) Methods to increase urine output using low dose dopamine (1–3 mc g/ kg/ min), furosemide and mannitol may limit renal dysfunction. Current available data doesn’t support the use of these drugs.

50. Spinal cord : Ischemic neurological injury usually presents as paraplegia - Distal hypoperfusion - increases the CSF pressure (CSFP)  the spinal cord perfusion pressure (SCPP) is decreased (MAP - CSFP ) [ Redistribution of blood volume proximal to the clamp  intracranial hypervolemia shift of CSF into spinal space] Risk factors: prolonged ischemia (cross-clamp time > 30–45 min) resection of the artery of Adamkiewcz . presence of aortic dissection extent of the aneurysm whether intercostal arteries were implanted and age. Distal aortic hypoperfusion , perioperative hypotension and hypoxaemia are risk factors for developing postoperative delayed paraplegia .

51. Protective measures: 1. D ecreasing aortic cross-clamp time 2. CSF drainage using spinal drains  decrease CSFP  improves SCPP. CSFP @ 10 cm H2O  continued in the immediate postoperative period for at least 48–72 h After surgery, MAP should be maintained between 80 and 100 mm Hg. Delayed neurological deficit can occur. The signs include unstable arterial B.P , post extubation hypoxaemia and CSF pressure >10 mm Hg. CSF drainage is discontinued usually after the second postoperative day. If delayed neurological deficit occurs, the CSF drainage catheter should be reinserted and CSF drained for another 3 days .

52. 3 . Distal aortic perfusion: It protects the spinal cord only if the artery of Adamkiewcz originates beyond the distal clamp. 4. Hypothermia: It increases ischemic tolerance because neural oxygen consumption decreases by 5% for every degree centigrade reduction in body temperature. Mild to moderate hypothermia, DHCA and regional spinal cord cooling have shown to be spinal cord protective. Regional spinal cord cooling  infusion of iced saline ( 4degC ) through an epidural catheter or perfusion of the aortic area between the cross-clamps with iced solutions.

53. 5 . surgical implantation of critical intercostal arteries, 6. intrathecal papaverine 7. drugs such as steroids , barbiturates etc 8. Neuro -monitoring: -Somatosensory evoked potentials (SSEP )  monitors the posterior column(sensory function) - M otor evoked potentials(MEP)  monitor anterior horn cells have shown some success; however , this requires partial neuromuscular block

54. mesentery DTA cross-clamping results in ischaemia and reperfusion injury to the mesenteric circulation. rapid reimplantation of the celiac trunk and superior mesenteric artery is required D epletion of coagulation factors and bleeding abnormalities can occur after supracoeliac cross-clamping (severity correlates with prolonged clamp times) ABG levels should be monitored at regular intervals,. Maintenance of perfusion of the gut, liver and kidneys with the use of distal perfusion techniques reduces the severity of these complications. The use of mesenteric shunts to perfuse the viscera can significantly reduce visceral ischaemic time.

55. MASSIVE BLOOD LOSS AND COAGULOPATHY: Intraoperative haemorrhage is a major cause of early mortality Risk factors: hypothermia and acidosis heparinization and DIC after hypoperfusion. Hepatic hypoperfusion leads to citrate accumulation and hypocalcemia . Massive blood transfusion  dilutional thrombocytopenia and factor deficiencies.

56. Techniques for monitoring coagulation: TEG, platelet function analyser (PFA), and prothrombin time(PT) and activated partial thromboplastin time( aPTT ) Blood , platelets, fresh frozen plasma and cryoprecipitate should be readily available in addition to a cell saver. Depending on the preoperative hemoglobin , up to 2 units (350 ml per unit) of blood can be removed before heparinization and stored at room temperature with frequent agitation. The autologous blood is a good source of platelets and is retransfused after heparin reversal with protamine.

57. MANAGEMENT FOR ASCENDING AORTA AND AORTIC ROOT SURGERY A clamp can be applied proximal to innominate artery similar to aortic valve surgery involving a median sternotomy and routine cardiac anaesthesia

58. SURGERY INVOLVING AORTIC ARCH Repair of aortic arch involves interruption to cerebral blood supply necessitating use of CPB and deep hypothermic cardiac arrest . Cerebral perfusion can be maintained 1) Antegrade through cannulation of arteries As they branch from aortic arch (or) Arterial line into right axillary ,subclavian , innominate artery 2) Retrograde through cannulation of internal jugular vein Hypothermia is an effective technique for protection of C.N.S and other viscera during reduced or absent blood flow . The lower temperature reduces tissue metabolic activity and attenuates inflammatory response to reperfusion .

59. Deep hypothermia (14.1 -20 o ) allows 20-30 minutes of safe circulatory arrest time when compared to moderate hypothermia (20.1 -28 o ) which allows 10-20 minutes . Profound cooling contributes to morbidity through development of coagulopathy and development of inflammatory response MONITORING : Standard monitoring Invasive arterial B.P (rt radial artery ) Temperature measurement ( probe in nasopharynx reflect accurate cerebral temperature ) Jugular bulb venous o2 saturation and EEG monitoring for cerebral metabolism Cerebral oxygenation monitoring using near infrared spectroscopy (NIRS).

60. Inadequate perfusion should prompt - Assessment of cannulation sites . Increased flow rate within C.P.B circuit . Optimise haemoglobin concentration . Increase hypothermia and PCO2 to promote vasodilation if necessary .

61. Surgery involving descending aorta The use of partial left heart bypass is used is preferable , as inflammatory response and coagulopathy is less when compared to C.P.B and hypothermia . Other techniques like GOTT shunt can be used Patient is positioned in a left helical or semi lateral position with torso and shoulders rotated approximately 60 o and hips 30 o A standard induction is performed using short acting NDMR One lung ventilation with a left sided DLT is preferred . Standard monitors are attached Invasive arterial B.P (rt radial & femoral artery) A central venous catheter is inserted in left I.J.V Hypothermia is used & temperature probes placed in Nasopharynx and rectum/bladder .

62. Avoid renal, visceral ,spinal cord ischemia . Neurophysiological monitoring with the use of motor evoked potential M.E.P and somatosensory evoked potential can be used A decrease in M.E.P amplitude >50% should prompt re-insertion of intercostal arteries into graft along with measures to improve spinal cord perfusion Haemostasis should be achieved

63. Postoperative management : Surgical incisions; major muscles are transected and ribs are removed. In addition, chest tube insertion sites can be very painful. Amelioration of pain is essential to ensure patient comfort and facilitate coughing and maneuvers designed to prevent atelectasis Pain relief is commonly provided by neuraxial opioids and/or local anesthetics Sedation : minimal sedation with intermittent holds should be used to allow assessment of neurological functions . Neurophysiological monitoring , I.C.P monitoring , CSF drainage continue for 72 hrs Look for delayed paraplegia (regular assessment of lower limb power ) In case of neurological impairment  CSF drain status, optimise O2 delivery ,patient status in terms of MAP,SCPP, cognitive status

64. COMPLICATIONS : Hypothermia, Coagulopathy , Delirium , CVS instability , Respiratory failure Metabolic disturbance Renal failure Spinal cord ischemia Stroke

65. TEVAR Endovascular placement of intraluminal stented grafts to treat patients with descending thoracic aneurysms The prosthesis bridges the aneurysmal sac  exclude it from high pressure aortic flow

66. INDICATIONS: Elderly patients Co existing diseases (hypertension , COPD , renal insufficiency ) Patients with aneurysms larger than 6 cm Symptomatic aneurysms Aneurysms associated with a rapid growth rate of greater than 1 cm per year are considered to be at increased risk for rupture It is also used in Traumatic aortic transection Management of type b dissection Penetrating aortic ulcer Intramural thrombus

67. Advantages less invasive technique obviates the need for extensive and prolonged aortic occlusion decreases blood loss avoids significant fluid shifts lowering the risk of significant periop hemodynamic changes requiring less anesthesia Basic structural design: Metal stent ( nitinol , stainless steel ) Fabric (polyester or polytetrafluroethylene )

68. Challenges: 1. Hemodynamic forces : more severe, more mechanical demand on the endo graft  migration, kinking, late structural failure 2. Greater flexibility of device 3. Larger devices 4. Paraplegia 5. Renal and visceral ischemia( celiac axis occluded)

69. CONTRAINDICATIONS Unfavorable anatomy is the main contraindication to TEVAR, inadequate proximal or distal seal zones, tortuosity lack of vascular access extremes of aortic diameter. 2. Placement into infected fields should also be avoided

70. complications Stroke Paraplegia Visceral ischemia ( if it occludes coeliac artery) Post implantation syndrome (fever & leucocytosis ) Assess complication Device migration , kinking and structural failure . Endoleaks Vascular injury during graft deployment. Inadequate fixation & sealing of graft .

71. References: Stoelting’s anaesthesia and co-existing disease. Miller’s anaesthesia Descending thoracic aortic Aneurysms Madhusudan Rao Puchakayala , doi:10.1093/ bjaceaccp /mkl002 Perioperative management of thoracic and thoracoabdominal aneurysms S. Agarwal, J. Kendall and C. Quarterman . doi: 10.1016/j.bjae.2019.01.004 Clinical update- 2022 ACC/AHA Guidelines for the Diagnosis and Management of Aortic Disease

72. Previous year questions Physiological changes during aortic cross clamping and unclamping {2011,2015,2016} Describe renal protective measures during aortic clamping .