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Perioperative Hypotension and Myocardial Ischemia

Perioperative Hypotension and Myocardial Ischemia. Dr. 黃啟祥 台大醫院 麻醉部. Perioperative Hypotension. Assess Severity. Is the degree of hypotension SERIOUS? 20% or more below baseline values If YES then validate reading (if possible) Associated with end-organ ischemia

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Perioperative Hypotension and Myocardial Ischemia

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  1. Perioperative Hypotension and Myocardial Ischemia Dr. 黃啟祥 台大醫院 麻醉部

  2. Perioperative Hypotension

  3. Assess Severity • Is the degree of hypotension SERIOUS? • 20% or more below baseline values • If YES then validate reading (if possible) • Associated with end-organ ischemia • Drowsiness / Confusion / Agitation • Nausea • Angina / ST segment change • If YES then proceed to critical management • Otherwise manage as mild to moderate hypotension

  4. Hypotension Validation • Check NIBP monitor • Repeat cycle, check cuff size, check manually • Confirm with palpation of large artery for pulse • If no pulse, manage as for CARDIAC ARREST • Check arterial line • Flush, open to air and quickly confirm zero, pulsatile waveform • Independent pulse source – SpO2 • Has ETCO2 level fallen? • Low ETCO2 = Low cardiac output or Embolism

  5. Critical Management I • Increased inspired OXYGEN • Is the hypotension EXPECTED? • Is it the result of an anticipated surgical intervention? • If YES then manage in context of surgical causes • If UNEXPECTED, quickly check that there are no obvious surgical issues e.g. • Sudden massive blood loss • IVC compression (including obstetrics / laparoscopy) • Femoral shaft reaming etc. • CO2 insufflation • Tourniquet or Vascular Clamp release

  6. Critical Management IICheck EKG • If Asystole / VF or pulseless VT then manage CARDIAC ARREST • If TACHYARRHYTHMIA (AF/SVT/VT) then • Control rate with Vagal Manouvres / Vagotonic Drugs or Synchronized Cardioversion • Review possible causes including LIGHT ANAESTHESIA • If SEVERE BRADYCARDIA then • Increase rate with vagolytic agents (atropine) • Use chronotropic pressors (ephedrine, adrenaline) • Review possible causes including HYPOXIA

  7. Critical Management IIIProvide circulatory support in presence of normal rhythm • Volume resuscitation • First priority in context of recent neuraxial block • IV fluids • Posture legs up (if practical) • Consider wide-bore access • Vasopressors • Especially if GA or unresponsive to volume or limited ability to rapidly infuse fluids • Ephedrine / Metaraminol / Phenylephrine / Noradrenaline / Adrenaline / Vasopressin

  8. Critical Management IVAssess CAUSE and provide SPECIFIC treatment • Consider likely causes of SEVERE HYPOTENSION • Sudden BLOOD LOSS (surgical) • Impaired VENOUS RETURN (surgery / posture / high airway pressures / pneumothorax) • VASODILATION (neuraxial block - assess block height, anesthetic agents, drug reactions including ANAPHYLAXIS) • EMBOLISM (Air / CO2 / orthopedic / venous thromboembolism) • CARDIAC ARRHYTHMIA • CARDIAC Dysfunction • Ischemia / Infarction • Depressants (anesthetic agents etc)

  9. Critical Management VContinue to Support Blood Pressure • If still severely hypotensive • Call for assistance • Review Likely Causes • If cause still not determined : Perform Systematic Review of • AIRWAY: pressure, minute volume • BREATHING: CO2 exchange, oxygenation • CIRCULATION: rhythm, ischemia, volume (insert CVP, PAC, TEE) • DRUGS: check doses, agent • Consider other RARE CAUSES

  10. Non-Critical Management I • Validate reading • Attempt to IDENTIFY CAUSE • Treat by • CORRECTING CAUSE • DECREASING ANESTHETIC DEPTH (if GA) • VOLUME (IV or posture) • VASOPRESSORS (if unresponsive to other measures)

  11. Non-Critical Management II • Identify and treat COMMON CAUSES of mild to moderate intraoperative hypotension • Relative HYPOVOLAEMIA • Neuraxial BLOCK (assess block height), inadequate fluid replacement • Excessive relative DEPTH of ANESTHESIA • Volatile agent / IV agent too high • High AIRWAY PRESSURES • SURGICAL • Blood loss, venous return compression, release of tourniquet or vascular clamp • Mild RHYTHM disturbance • Nodal rhythm, slow AF

  12. Non-Critical Management III • If unable to identify a cause at this stage, proceed to a more thorough systematic assessment • Perform Systematic Review of • AIRWAY: pressure, minute volume • BREATHING: CO2 exchange, oxygenation • CIRCULATION: rhythm, ischemia, volume (insert CVP, PAC, TEE) • DRUGS: check doses, agent • Consider RARE CAUSES

  13. Rare Causes of Intraoperative Hypotension • Anaphylaxis • Drug Error • Transfusion Incompatibility • Acute Mitral Valve Rupture • Pericardial Tamponade • Septic Shock • Adrenocortical Insufficiency

  14. Perioprative Myocardial Ischemia

  15. Importance of perioperative myocardial ischemia • Adverse cardiac events are major cause of post-surgical morbidity and mortality • Perioperative ischemia (esp postoperative and prolonged) is associated with adverse cardiac events (early and late) • Most perioperative ischemia is silent • Real-time detection may allow therapeutic intervention

  16. Patients at Risk • Known coronary artery disease (CAD) • Increased risk of CAD • Diabetes, hypertension, smoking, hyperlipidemia, family history of CAD, peripheral vascular and cerebrovascular disease • Increased risk of cardiovascular complications • Renal insufficiency, age > 65, history of cardiac failure, poor functional capacity (<4 METS), abnormal ECG • Surgical factors • Major urgent surgery, vascular surgery (inc peripheral), significant fluid shifts, blood loss

  17. Risk Reduction Strategies 1 • Sympathetic modulation ­ avoid tachycardia • BETA-BLOCKADE • Alpha-2 agonists • ? Anxiety control (premed), Good analgesia, Epidural (local anes) • Maintain normothermia postoperatively • Hemoglobin > 9 ­ 10 g/dL • Avoid hypoxia ­ prolonged supplemental O2 (maybe > 3 days)

  18. Risk Reduction Strategies 2 • Coagulation modulation • Sympathetic modulation • Aspirin, ketorolac • Heparin • Warfarin • Periop period is a hypercoagulable state - thrombosis involved in pathogenesis of acute coronary syndromes and platelet inhibitors and anticoagulants are used to treat acute coronary syndromes

  19. How to Monitor for Ischemia • Symptoms: usually none • Pain, SOB, sweating, N &V, altered mentation • Clinical signs: usually none • Sweating, CHF, HR changes, arrhythmias, hypotension • ECG: key perioperative monitor • Pulmonary artery catheter • Increased PCWP, new V waves on PCWP tracing • TEE • SWMA, change in mitral regurgitation, diastolic dysfunction, decrease in global contractility

  20. ECG Monitoring for Ischemia 1Optimal use • Lead selection ­ II and V4 or V5 (3 lead - modified V leads e.g. CM5) • Correct electrode positioning • Good electrode application • Calibration (1mV = 1 cm) • Mode: diagnostic • Printout baseline and any changes • Automated ST segment analysis • Always review measurement points to verify ST segment changes

  21. ECG Cables

  22. Lead CM5

  23. ECG Monitoring for Ischemia 2Ischemic Manifestations • ST SEGMENT CHANGES (most specific) • T wave changes • esp inversion in high risk groups • Arrhythmias • New conduction abnormalities • New atrioventricular block • Heart rate changes

  24. ECG Monitoring for Ischemia 3ST Segment Criteria for Ischemia • Depression: subendocardial ischemia, poor localization • Horizontal / downsloping depression > 0.1 mV (1 mm) at 60-80 msec after J point • Upsloping depression > 0.15 mV at 80 msec after J point • Elevation: transmural ischaemia, good localization • > 0.1 mV at 60-80 msec after J point

  25. J Point and ST Segment

  26. ECG monitoring for Ischemia 4Other Causes of Acute ST Segment Changes • Conduction disturbances • R wave amplitude changes • Hyperventilation • Electrolyte changes, hypoglycemia • Hypothermia (< 30º) • Body position changes / retractors • Autonomic NS changes e.g. spinal • Myocardial infarction or contusion • Neurological changes (trauma, SAH) • Acute pericarditis

  27. ECG Monitoring for Ischemia 5Causes of Chronic ST Segment Changes • Non-specific changes ­ V4 most likely to be isoelectric • LVH • Early repolarization pattern • Digitalis • Bundle branch blocks esp LBBB • Old myocardial infarction • LV aneurysm

  28. Management of Suspected Intraoperative Ischemia • FIRSTLY • Secure system ­ ensure adequate oxygenation, BP, volume, Hb • SECONDLY • Verify change • Optimize hemodynamics - especially tachycardia and blood pressure • THIRDLY, consider • Increase FiO2 • NTG • Increased monitoring ­ CVP, PCWP, TEE • Inform surgeon, alter surgical plan • Postoperative management

  29. Management of Suspected Intraoperative Ischemia - Verify Change • Check ECG (calibration, mode, previous ECG printouts) • Verify automatic ST segment analyses • Look for associated features • Arrhythmias, hypotension • Increased filling pressures or new V waves • TEE changes (check all LV segments) • Consider • Other causes of ECG change • Patient’s risk of CAD

  30. Management of Suspected Intraoperative Ischemia - Tachycardia management • FIRSTLY treat cause e.g. hypovolemia, anesthetic depth, CO2 • NEXT: • Beta-blockade (aim for HR < 60) • Esmolol ­ 0.25 - 0.5 mg.kg bolus, 25 - 300 mg/kg/min infusion - atenolol ­ 0.5 - 10 mg titrated bolus over 15 minutes • Metoprolol ­ 1- 15 mg titrated bolus over 15 minutes • If beta-blockade contraindicated • Verapamil ­ 2.5 mg - repeat as needed. Infuse at 1-10mg/hr [may be first choice if ST segment elevation (coronary spasm)] • alpha-2 agonists ­ clonidine, dexmedetomidine

  31. Management of Suspected Intraoperative Ischemia - BP management • Hypotension • Treat cause e.g. hypovolemia, anesthetic depth, PEEP, surgical manipulation • Vasopressors (metaraminol, phenylephrine) (inotropes with caution as increase O2 demand) • Hypertension • Treat cause e.g. anesthetic depth, CO2 • NTG - sublingual (0.3-0.9 mg ­ works within 3 min) • IV infusion (0.25 - 4 mg/kg/min ­ titrate to effect) • Clonidine (30 mg every 5 minutes up to 300 mg) • Dexmedetomidine (1mg/kg load, infuse at 0.2-0.7 mg/kg/hr)

  32. Management of Persistent Ischemia If Ischemia Persists with Optimal Hemodynamics • Keep increasing NTG (may combine with vasopressor if hypotension) • May increase monitoring ­ CVP, PCWP, TEE • CONSIDER Acute Coronary Syndrome (unstable angina, infarct) • Aspirin or ketorolac • Heparin (5000 U bolus, then 1000 U/hr) if surgery permits • Continue beta-blockade (aspirin & beta-blockade reduce risk of infarct and mortality) • Observe for complications- arrhythmias, CHF, infarct • Cardiology consult - urgent reperfusion - within 12-24 hours (especially if persistent ST segment elevation) • PTCA most practical (thrombolysis CI after surgery) • ? IABP

  33. Postoperative Management of Perioperative Ischemia • CONSIDER • ICU or CCU postop and/or cardiology referral • Surveillance for periop MI • ECG immediately postop and on day 1 and 2 • Cardiac troponin at 24 hrs and day 4 (or hosp discharge) (CK-MB of limited use) • LONG TERM • Letter to GP / cardiologist • Risk factor management • Aspirin, statins, beta-blockade, ACE inhibitors

  34. THE END

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