Perioperative Hypotension and Myocardial Ischemia

Dr. 黃啟祥台大醫院 麻醉部

Perioperative Hypotension

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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

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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

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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

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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 ANAESTHE

SIA

• If SEVERE BRADYCARDIA then– Increase rate with vagolytic agents (atropine)– Use chronotropic pressors (ephedrine, adrenaline)– Review possible causes including HYPOXIA

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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 / Noradrenal

ine / Adrenaline / Vasopressin

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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 pre

ssures / pneumothorax)– VASODILATION (neuraxial block - assess block height, anesthet

ic agents, drug reactions including ANAPHYLAXIS)– EMBOLISM (Air / CO2 / orthopedic / venous thromboembolism)– CARDIAC ARRHYTHMIA– CARDIAC Dysfunction– Ischemia / Infarction– Depressants (anesthetic agents etc)

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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 CV

P, PAC, TEE)– DRUGS: check doses, agent

• Consider other RARE CAUSES

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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)

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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

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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

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Rare Causes of Intraoperative Hypotension

• Anaphylaxis

• Drug Error

• Transfusion Incompatibility

• Acute Mitral Valve Rupture

• Pericardial Tamponade

• Septic Shock

• Adrenocortical Insufficiency

Perioprative Myocardial Ischemia

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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

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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 periphera

l), significant fluid shifts, blood loss

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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 (may

be > 3 days)

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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

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How to Monitor for Ischemia

• Symptoms: usually none– Pain, SOB, sweating, N &V, altered mentation

• Clinical signs: usually none– Sweating, CHF, HR changes, arrhythmias, hypotensio

n• 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

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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

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ECG Cables

Monitoring cable connections

Europe 

RedYellowGreenBlackWhite

Connect to: 

Right ArmLeft ArmLeft Leg

Right LegChest

U.S.A. 

WhiteBlackRed

GreenBrown

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Lead CM5

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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

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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 p

oint• Elevation: transmural ischaemia, good localizatio

n– > 0.1 mV at 60-80 msec after J point

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J Point and ST Segment

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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

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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

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Management of Suspected Intraoperative Ischemia

• FIRSTLY– Secure system ensure adequate oxygenation, BP, volume, Hb

• SECONDLY– Verify change– Optimize hemodynamics - especially tachycardia and blood pres

sure

• THIRDLY, consider– Increase FiO2– NTG– Increased monitoring CVP, PCWP, TEE– Inform surgeon, alter surgical plan– Postoperative management

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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

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Management of Suspected Intraoperative Is

chemia - 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 g/kg/min infusion - at

enolol 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

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Management of Suspected Intraoperative Ischemia - BP management

• Hypotension– Treat cause e.g. hypovolemia, anesthetic depth, PEE

P, surgical manipulation– Vasopressors (metaraminol, phenylephrine) (inotrope

s 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 g/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)

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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 i

nfarct and mortality)– Observe for complications- arrhythmias, CHF, infarct– Cardiology consult - urgent reperfusion - within 12-24 hours (esp

ecially if persistent ST segment elevation)• PTCA most practical (thrombolysis CI after surgery)

– ? IABP

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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 dischar

ge) (CK-MB of limited use)

• LONG TERM– Letter to GP / cardiologist– Risk factor management– Aspirin, statins, beta-blockade, ACE inhibitors

THE END