GNG Anaesthesia for vascular surgeries 1.pptx

Anaesthesia for vascular surgeries

1. ANAESTHESIA FOR VASCULAR SURGERIES MODERATOR : DR.B.SYAMA SUNDARA RAO PROF, DEPT . OF ANAESTHESIOLOGY,CAIMS PRESENTER : DR.G.NAGARAJ PG Ist YEAR

2. VASCULAR SURGERIES- INDICATIONS Occlusive disease : . Atherosclerosis . thromboembolism Aneurysms Dissection

3. ATHEROSCLEROSIS Atherosclerosis is a progressive systemic inflammatory disease that compromises the arterial blood supply to any or all of the vital organs or the extremities most commonly- CAD, CVA and PAD. Risk factors includes age, male gender, family h/o premature cardiovascular ds. High LDL cholesterol, low HDL)cholesterol, diabetes, obesity, hypertension, smoking , homocysteinemia and hyperfibrinogenemia . No early warning signs, prevention is difficult and risk modification is often delayed until the patient has progressed to an advanced stage of disease. The lesions of atherosclerosis occur primarily in large- and medium-sized arteries and may be present throughout one's lifetime.

4. Progression of atherosclerosis occurs in three general stages . Fatty streak, starts in early childhood and forms beneath the normal endothelium. consist of lipid-laden macrophages (i.e., foam cells), smooth muscle cells, and elastic and collagen fibers. Fibrous plaque consisting of degenerated foam cells covered by a layer of proliferated smooth muscle cells. Progression of the fibrous plaque, with an expanded lipid-rich core, accumulation of calcium, and disruption of endothelial integrity. Physical disruption of the plaque's protective cap permits contact between flowing blood and the highly thrombogenic material located in the lesion's lipid core (e.g., tissue factor), which results in thrombus formation (i.e., atherothrombosis ). Thrombosis may lead to complete occlusion and clinically important complications (e.g., acute myocardial infarction [MI]) or, in the case of intraplaque hemorrhage, to plaque progression.

5. VASCULAR SURGERIES- INTRODUCTION The major categories of vascular surgical procedures are : aortic surgeries : - abdominal - thoracoabdominal - endovascular . lower extremity vascular surgery, carotid surgery .

6. PREOPERATIVE EVALUATION It includes : Evaluation and Rx of coexisting ds. Risk assessment and Preoperative Medications

7. COEXISTING DISEASES Vascular disease is a “whole-body” phenomenon. ■ Cardiac : CAD → CHF, MI,HTN, angina, arrhythmias, valvular heart ds. ■ Pulmonary : Smoking history → COPD or underlying malignancy. ■ Renal : HTN, diabetes, arteriosclerosis, and volume depletion may → renal insufficiency. ■ CNS : Presence of carotid bruits, history of CVA ,TIAs , amaurosis fugax or syncope ■ Endocrine : Diabetes and its end-organ complications are a concern. Tight glucose control should be achieved.

8. CARDIAC RISK ASSESSMENT Previous Coronary Artery Bypass Surgery Previous coronary revascularization may not provide the same level of protection against MI and death after major vascular surgery. According to the current ACC/AHA guidelines on perioperative management and CABG, preoperative revascularization is reserved for patients with unstable cardiac conditions or advanced coronary disease, for whom a survival benefit with CABG has been proved.

9. ASSESSMENT OF PULMONARY FUNCTION Postoperative pulmonary complications are potentially serious in patients undergoing vascular surgery, most commonly with open aortic procedures . The most important pulmonary complications are atelectasis , pneumonia, respiratory failure, and exacerbation of underlying chronic disease. cigarette smoking l/t COPD and chronic bronchitis increases risk for postoperative pulmonary complications. Pre- op pulmonary function tests may be useful in evaluating and optimizing respiratory function Preoperative ABG- Baseline hypercapnia (Pa CO2 >45 mm Hg) - higher risk for postoperative morbidity.

10. Bronchodilator therapy may be indicated on the basis of PFTs, although the risk of β-agonist–induced arrhythmia or myocardial ischemia must also be considered. patients with significant COPD or asthma - short course of glucocorticoids (prednisone, 40 mg/day for 2 days). Pulmonary infection - Appropriate antibiotics. patients with significant pulmonary disease may benefit from epidural techniques that are maintained into the postoperative period because the use of local anesthetics helps avoid respiratory depression from systemic opiates. Incentive spirometry and CPAP – post- op period.

11. ASSESSMENT OF RENAL FUNCTION Chronic renal disease is common in vascular surgery patients and is associated with an increased risk for death and cardiovascular disease . Serum creatinine and creatinine clearance are commonly used to assess renal function A preoperative serum creatinine >2 mg/ dL is an independent risk factor for cardiac complications after major noncardiac surgery. Preoperative creatinine clearance <60 mL/min is an independent predictor of both short- and long-term mortality after elective vascular surgery.

12. Atherosclerotic disease in the abdominal aorta or renal arteries may compromise renal blood flow and renal function. Conversely, renal artery stenosis causes hypertension through renin - and angiotensin -induced vasoconstriction. Hypertension itself may cause renal insufficiency or failure. Diabetic nephropathy is also common. The preoperatively and intraoperatively administered angiographic dyes are directly nephrotoxic . Renal ischemia occurs with interruption of renal blood flow from aortic cross-clamping.

13. PRE OPERATIVE MEDICATION MEDICATION SIDE EFFECT OR POTENTIAL CONCERN IN THE PERIOPERATIVE PERIOD RECOMMENDATION FOR PERIOPERATIVE USE Aspirin Platelet inhibition may ↑ bleeding. ↓ GFR. Continue until day of surgery. Monitor fluid and urine status Clopidogrel Platelet inhibition may ↑ bleeding. Rare thrombotic thrombocytopenic purpura Hold for 7 days before surgery except for CEA and severe CAD. Consider blood crossmatch . Avoid neuraxial anesthesia if not held for at least 7 days. HMG- CoA reductase inhibitors LFT abnormalities. Rhabdomyolysis . Assess LFTs and continue through morning of surgery. Check CPK if myalgias .

14. β blockers Bronchospasm , Hypotension. Bradycardia. Heart block. Continue through perioperative period. ACE inhibitors Induction hypotension. Cough. Continue through perioperative period. Consider one-half dose on day of surgery. Diuretics Hypovolemia. Electrolyte abnormalities. Continue through morning of surgery. Monitor fl uid and urine status. Calcium channel blockers Perioperative hypotension, especially with amlodipine . Continue through perioperative period (consider withholding amlodipine on the morning of surgery). Oral hypoglycemics Hypoglycemia preoperatively and intraoperatively. Lactic acidosis with metformin . When feasible, switch over to insulin preoperatively. Monitor glucose status perioperatively

15. SURGERIES OF THE AORTA

16. Surgery on the aorta presents unique challenges to anesthesia care providers Procedure complicated by: Need to cross-clamp the aorta Potential for large intraoperative blood loss These Surgeries are characterised by cross clamping and unclamping of the aorta which produces many physiological alterations in the haemodynamics and metabolism

17. PHYSIOLOGIC CHANGES WITH AORTIC CROSS CLAMPING Hemodynamic Changes A.Due to ↑ Arterial blood pressure above the clamp :   Acutely ↑ LV afterload → myocardial ischemia, LV failure, or aortic valve regurgitation ↑ Segmental wall motion abnormalities    ↑ Left ventricular wall tension    ↓ Ejection fraction    ↓ Cardiac output   ↑ Pulmonary occlusion pressure    ↑ Central venous pressure    ↑ Coronary blood flow B. Due to ↓ Arterial blood pressure below the clamp : ↓ Renal blood flow   ↓ blood flow to the spinal cord  

18. Metabolic Changes : ↓ Total-body oxygen consumption    ↓ Total-body carbon dioxide production    ↑ Mixed venous oxygen saturation    ↓ Total-body oxygen extraction    ↑ Epinephrine and norepinephrine    Respiratory alkalosis   Metabolic acidosis

19. PHYSIOLOGIC CHANGES WITH AORTIC UNCLAMPING Hemodynamic Changes ↓ Myocardial contractility    ↓ Arterial blood pressure    ↑ Pulmonary artery pressure    ↓ Central venous pressure    ↓ Venous return    ↓ Cardiac output

20. Metabolic Changes ↑ Total-body oxygen consumption    ↑ Lactate    ↓ Mixed venous oxygen saturation    ↑ Prostaglandins    ↑ Activated complement    ↑ Myocardial depressant factor(s)    ↓ Temperature    Metabolic acidosis Slow release of clamp, volume loading, briefly ↓ anesthetic depth, and intermittent dosing of vasopressors can alleviate the amount of hypotension .

21. Indications for aortic surgery include: Aneurysms Aortic dissection Occlusive disease Trauma Coarctation Specific site lesions: Ascending aorta Aortic arch Distal to left subclavian artery and above diaphragm Below the diaphragm

22. AORTIC ANEURYSMS Most commonly involve the abdominal aorta Etiologies; atherosclerosis, medial cystic necrosis, rheumatoid arthritis, spondyloarthropathies , and trauma Depending on site may produce aortic regurgitation, tracheal or bronchial compression or deviation, hemoptysis , and superior vena cava syndrome

23. Greatest danger: Rupture and exsanguination Normal aorta in adults: 2-3 cm in width Likelihood of catastrophic rupture related to size . <4cm--- u/s q 6 months . 4-5cm– elective repair w/low operative risk and good life expectancy. . 5-6 cm– need repair (mortality rate 0.9-5%) . 6-7 cm– threshold for rupture (mortality as high as 75%). Pseudoaneurysm formation Prosthetic graft used. Operative mortality rate ~ 2-5% and exceeds 50% if leaking or rupture has occurred.

24. DeBakey classification Characterized by a spontaneous tear of the vessel wall intima , permitting the passage of blood along a false lumen May be caused by variations in wall integrity HTN most common factor contributing to the progression of the lesion AORTIC DISSECTION

25. Most serious complication is aneurysm rupture Treatment of dissecting aortic lesions: Proximal dissections nearly always treated surgically Distal dissections may be managed medically initially Measures to reduce SBP and wall stress are initiated once diagnosis confirmed Anesthesia for aneurysms of the ascending and transverse aorta requires cardiopulmonary bypass

26. OCCLUSIVE DISEASE OF THE AORTA Thromboembolic occlusion of the aorta is most commonly atherosclerotic in origin Results from a combination of atherosclerotic plague and thrombosis Atherosclerotic process usually generalized affecting other portions of the arterial system Occurs at aortic bifurcation ( Leriche's syndrome). Surgical treatment: Aorto-bifemoral bypass Possible proximal thromboendarterectomy

27. COARCTATION OF THE AORTA Congenital heart defect classified in relation to the ductus arteriosus: ■ Preductal type often diagnosed during infancy: Diminished pulses in lower extremities. Lower-body cyanosis. Upper-body perfusion from aorta; lower-body perfusion from pulmonary artery. ■ Postductal type often diagnosed in adulthood. Severity of lesion and amount of collateral circulation determines severity of symptoms. Upper-extremity HTN.

28. AORTIC TRAUMA May be penetrating or non-penetrating May result in massive hemorrhage and require immediate surgical intervention Non-penetrating aortic trauma typically results from MVCs and falls Injury can vary from a partial tear to a complete aortic transection CXR: Wide mediastinum

29. PREOPERATIVE EVALUATION Patients who undergo major vascular surgery are frequently elderly and have varying degrees of concurrent disease Thorough preoperative evaluation significant in this patient population Special attention should be directed toward cardiac, renal, and neurologic function Preoperative renal dysfunction directly related to postoperative renal failure

30. ANAESTHETIC MANAGEMENT

31. MONITORING Large IV access above the diaphragm should be established prior to induction Pulse oximetry and ECG. Direct intra-arterial blood pressure monitoring (preferably on the right). the radial artery is most commonly selected for cannulation because of its superficial location, easy accessibility, and low complication rate. A noninvasive blood pressure cuff - contralateral arm in the event of IBP malfunction. A central venous catheter for all open aortic procedures. - CVP monitoring - administration of drugs pulmonary artery catheter for all patients requiring supraceliac aortic cross-clamping and pt.s with significant left ventricular dysfunction (ejection fraction <30%), a history of congestive heart failure, significant renal impairment (preoperative creatinine >2.0 mg/ dL ), or cor pulmonale .

32. Two-dimensional Transesophageal echocardiography (TEE): - to assess global ventricular function, guide fluid therapy. - Highly sensitive and specific in the diagnosis of an acute aortic dissection. - Helpful particularly in type A dissections in the assessment of the aortic valve, tamponade , and left ventricular dysfunction. - Limited images of distal ascending aorta and proximal aortic arch because of interposition of trachea or bronchus between esophagus and aorta. In-dwelling urinary catheter Double-lumen ETT (if needed) inserted for one-lung ventilation to expose the descending thoracic aorta

33. AUTOLOGOUS BLOOD PROCUREMENT Preoperative autologous donation, intraoperative cell salvage, and acute normovolemic hemodilution to reduce or eliminate exposure to allogeneic blood and the associated risks of transfusion-related complications. Abd . Aortic surgeries - 4 to 6 units of packed red blood cells. thoracoabdominal aortic surgery – appx . 15 units of packed red blood cells and 15 units of thawed fresh frozen plasma.

34. TYPE OF ANAESTHESIA Anesthetic techniques include general anesthesia, epidural anesthesia or Epidural anesthesia in conjunction with general anesthesia. Induction of general anesthesia -controlled fashion such that stable hemodynamics is maintained during loss of consciousness, laryngoscopy and intubation, and the immediate postinduction period. thiopental, etomidate, propofol can be used. addition of a short-acting, potent opioid such as fentanyl (3 to 5 µg/kg) -stable hemodynamics during and after induction. Volatile anesthetics in low concentration before intubation during assisted ventilation -to blunt the intubation response. Esmolol (10 to 25 mg), sodium nitroprusside (5 to 25 µg), nitroglycerin (50 to 100 µg), and phenylephrine (50 to 100 µg) bolus administration during induction if needed to maintain appropriate hemodynamics .

35. Maintenance of anesthesia : combination of a potent opioid (fentanyl or sufentanil) and an inhaled anesthetic ( sevoflurane , desflurane , or isoflurane ) Patients with severe left ventricular dysfunction may benefit from a pure opioid technique, but a balanced anesthetic technique allows the clinician to take advantage of the most desirable characteristics of potent opioids and inhaled agents while minimizing their undesirable side effects. Nitrous oxide can be used to supplement either an opioid or an inhaled anesthetic. In general, nitrous oxide decreases cardiac output and arterial pressure while increasing systemic vascular resistance. Epidural anesthesia in conjunction with general anesthesia- to reduce post op pain and morbidity.

36. THERAPEUTIC INTERVENTIONS DURING AORTIC CROSS CLAMPING: Afterload reduction: - sodium nitroprusside - inhaled anaesthetics - Amrinone - shunts and aorta –to- femoral bypass. Preload reduction : - nitroglycerine - controlled phlebotomy - atrial- to- femoral bypass         Others : - Renal protection   - maintaining hypothermia - sodium bicarbonate

37. THERAPEUTIC INTERVENTIONS DURING AORTIC UNCLAMPING: ↓ Inhaled anesthetics    ↓ Vasodilators    ↑ Fluid administration    ↑ Vasoconstrictor drugs    Reapply cross-clamp for severe hypotension    Consider mannitol    Consider sodium bicarbonate

38. Temperature Control : Normothermia should be maintained before skin incision by increasing ambient temperature in the operating room, applying warm cotton blankets, and warming intravenous fluids. If significant hypothermia occurs early in the procedure, normothermia is extremely difficult to achieve, and emergence and tracheal extubation may be delayed. During surgery, all fluids and blood products should be warmed before administration. A forced-air warming blanket should be applied over the upper part of the body. The lower part of the body should not be warmed because doing so can increase injury to ischemic tissue distal to the cross-clamp by increasing metabolic demands.

39. Renal Function and Protection : approximately 3% of patients undergoing elective infrarenal aortic reconstruction. intraoperative urine output does not predict postoperative renal function. thoracic aortic cross-clamping - 83% to 90% ↓in RBF. Infrarenal aortic cross-clamping – 38% ↓in RBF ( due to renal vasoconstriction ). Acute tubular necrosis accounts for nearly all the renal dysfunction and failure after aortic reconstruction. The degree of preoperative renal insufficiency remains the strongest predictor of postoperative renal dysfunction. Other factors like ischemic reperfusion injury, intravascular volume depletion, embolization of atherosclerotic debris to the kidneys, and surgical trauma to the renal arteries also contribute to renal dysfunction.

40. Mannitol , loop diuretics, and dopamine are used to preserve renal function during aortic surgery. Mannitol : improves renal cortical blood flow during infrarenal aortic cross-clamping and reduces ischemia-induced renal vascular endothelial cell edema and vascular congestion. Other mechanisms by which mannitol may be beneficial include acting as a scavenger of free radicals, decreasing renin secretion, and increasing renal prostaglandin synthesis. Loop diuretics and low-dose dopamine : to protect the kidneys from aortic cross-clamp–induced injury by increasing renal blood flow and urine output intraoperatively. Intravascular volume and electrolytes during the postoperative period are to be monitored as therapy with these agents could cause hypovolemia and resultant renal hypoperfusion . In addition, dopamine's positive inotropic and chronotropic activity may cause tachycardia and increase myocardial oxygen consumption in patients with limited coronary reserve.

41. COAGULOPATHY Frequent complication during TAA repair. A dilutional coagulopathy in which platelets become deficient after approximately one blood volume of replacement develops during massive transfusion. At somewhere between one and two blood volumes of replacement, coagulation factors are diluted to levels low enough to increase bleeding. Other contributing factors are residual heparin; ischemia of the liver, where most coagulations factors are produced; and persistent hypothermia after weaning from bypass. Management: The prothrombin time, partial thromboplastin time, fibrinogen level, and platelet count should be measured frequently. fresh frozen plasma and platelets. Cryoprecipitate- especially when the PT and APTT are prolonged and hypervolemia prevents the administration of significant volumes of FFPs. When coagulopathy persists despite these efforts, ε- aminocaproic acid is beneficial as antifibrinolytic therapy, and desmopressin can be given to increase circulating levels of von Willebrand factor and factor VIII.

42. METABOLIC MANAGEMENT Arterial blood gases and electrolyte levels should be measured frequently. Sodium bicarbonate - metabolic acidosis. Hyperkalemia - should be treated aggressively, especially in oliguric or anuric patients. Calcium chloride and sodium bicarbonate are the primary acute treatments of hyperkalemia .

43. Emergence And Extubation: should be conducted after restoration of circulation and establishment of adequate organ perfusion. Hemodynamic, metabolic, and temperature homeostasis must be achieved before skin closure. otherwise, patients are transported to the intensive care unit (ICU) with their trachea intubated and their ventilation controlled. Extubation shouldn’t be done in patients with supraceliac aortic cross-clamp times longer than 30 minutes, patients with poor baseline pulmonary function, or patients requiring large volumes of blood or crystalloid during surgery. Hypertension and tachycardia - aggressively controlled by short-acting agents such as esmolol , nitroglycerin, and sodium nitroprusside .

44. SURGERY ON THE ASCENDING AORTA Routinely uses median sternotomy and cardiopulmonary bypass Intraoperative course may be complicated by: large volume shifts Large intraoperative blood loss Long aortic cross-clamp times new or worsening Aortic regurgitation Left radial artery used to monitor arterial blood pressure Nitroglycerin or nitroprusside is often used for precise blood pressure control. β blockers should be used with caution, as bradycardia can worsen aortic regurgitation

45. SURGERY INVOLVING THE AORTIC ARCH Procedures usually performed through a median sternotomy with deep hypothermic circulatory arrest Additional considerations focus on achieving optimal cerebral protection: Systemic and topical hypothermia (15 °C) Thiopental infusion Methylprednisolone or dexamethasone Mannitol Phenytoin Long rewarming periods contribute to intraoperative blood loss

46. SURGERY INVOLVING THE DESCENDING THORACIC AORTA Left thoracotomy approach if limited to the descending aorta Thoraco -abdominal incision if abdominal aorta also involved One-lung anesthesia Aorta must be cross-clamped above and below the lesion: Acute HTN develops above the clamp Hypotension below the clamp Arterial blood pressure monitored from right radial artery

47. SURGERY ON THE ABDOMINAL AORTA Anterior transperitoneal or anterolateral retroperitoneal approach Cross-clamp can be applied to the supraceliac , suprarenal, or infrarenal aorta Heparinization prior to occlusion is necessary Intra-arterial blood pressure monitoring Farther distally the clamp is applied, the less effect on LV afterload Fluid replacement guided by CVP or PA monitoring Renal prophylaxis with mannitol

48. Sudden increase in LV afterload during cross-clamping may precipitate acute LV failure and myocardial ischemia and exacerbate pre-existing aortic regurgitation. CO falls and LVEDP and volume rise. Effects less pronounced as clamp is applied more distally. Nitroprusside infusion needed. Hemodynamic instability following release of the aortic cross-clamp (release hypotension) can be treated by : Decrease anesthetic depth Volume loading Partial or slow release of the cross-clamp Vasopressor , NaHCO 3 , and/or CaCl may be necessary

49. PARAPLEGIA Major complication of clamping the thoracic aorta is spinal cord ischemia and paraplegia Classic deficit is that of an anterior spinal artery syndrome: Loss of motor function and pinprick sensation but preservation of vibration and proprioception Anatomic variations in spinal cord blood supply are responsible for the unpredictable occurrence of deficits Spinal cord receives its blood supply from the vertebral arteries and from thoracic and abdominal aorta: One anterior and two posterior arteries descend along the cord Intercostal arteries and artery of Adamkiewicz

50. Monitoring somatosensory evoked potentials Use of temporary heparin-coated shunt or partial CPB with hypothermia Other protective therapeutic measures: Methylprednisolone Mild hypothermia Mannitol Drainage of CSF

51. RENAL FAILURE Increased incidence of renal failure following aortic surgery associated with: Emergency procedures Prolonged cross-clamp periods Prolonged hypotension Infusion of mannitol (0.5 g/kg) prior to cross-clamping Low (renal)-dose dopamine Fenoldopam infusions Maintenance of adequate cardiac function: Preload Contractility Systemic perfusion pressure

52. POSTOPERATIVE CONSIDERATIONS Most patients having surgery on the ascending aorta, arch, or the thoracic aorta should remain intubated and ventilated postoperatively Initial emphasis in postoperative care should be on maintaining hemodynamic stability and monitoring for postoperative bleeding Patients having abdominal aortic surgery are often extubated at the end of the procedure Require increased maintenance fluids in the immediate postoperative period

53. ENDOVASCULAR AORTIC ANEURYSM REPAIR New and less invasive approach Involves deployment of an endovascular stent graft within the aortic lumen Graft restricts blood flow to the portion of the aorta in which the aneurysm exists Performed for descending thoracic aortic aneurysms or abdominal aortic aneurysms The technique most commonly requires bilateral transverse groin incisions to expose the common femoral arteries.

54. Indications : Severe COPD Severe cardiac disease Active infection Medical problems that preclude operative intervention Administration of anesthesia: Endovascular AAA repair: Neuraxial blockade or local anesthesia and sedation Endovascular thoracic aortic aneurysm repair: General anesthesia

55. Advantages: much less invasive Patients are discharged in 1-2 days post-op Complications: Disadvantages: Endoleaks - (failure to exclude the AAA) Require follow-up eval’s w/serial CT scans Demands more office visits than open

56. THAN’Q’