Cardiac Surgery

Cardiac surgery forms a significant component of intensive care work, and is unique due to the:

Initial Evaluation

Reception of the post-cardiac surgical patient includes:

  • Handover
  • Examination
  • Investigation

Handover

Important information for the cardiac admission:

  • Patient factors
    • Age
    • Key past medical history
      • Allergies
      • Major CVS risk factors and previous interventions
      • Chronic health conditions
      • Current medications
        Timing of last anticoagulants and anti-platelet agents.
    • Social history
      • Functional state
      • Next of kin
        Have they been contacted by the surgical team?
  • Surgical factors
    • What operation?
      • CABG
        • Adequacy of graft targets
        • Graft locations
      • Valvular
        • Adequacy of repair
        • Type of replacmeent
          • Mechanical
          • Tissue
    • Adequacy of myocardial protection
    • Complications and management
    • Bleeding
    • Drain location
      Pleural drains generally placed only if pleural breached (e.g., left pleural during mammary takedown for CABG).
    • Major surgical concerns
  • Anaesthetic factors
    • Airway management and intubation grade
    • Any issues with lines?
    • Pre-bypass haemodynamics
    • Pre-bypass echo
      Ventricular and valvular function.
    • Bypass time and cross-clamp time
    • Separation from bypass
      Requirements for:
      • Inotropes/vasopressors
      • Nitric Oxide
      • Pacing
      • IABP
      • Return to CPB
    • Post-bypass haemodynamics and changes in vasoactives
    • Post-bypass echo
    • Transfusion requirement
    • Coagulation status
    • Pacing wires
      Thresholds.
    • Current supports on arrival to ICU

Examination

Examination should involve:

  • Airway
    • ETT position
  • Breathing
    • Adequacy of gas exchange
      • ABG
      • Auscultation
      • Monitoring
    • Ventilation settings
  • Circulation
    • Haemodynamic state
      • HR
      • BP
      • CI/
      • Pressures
        Ensure zeroed.
    • Peripheral perfusion
    • Drain
      • Patency
      • Outputs
  • Disability
    • Pupils
    • GCS
  • E
    • Temperature

Investigations

Post-operative investigations should include:

  • ABG
    • Adequacy of gas exchange
    • Lactataemia
    • Hb
    • Electrolyte abnormalities
  • ECG
    Compare with pre-operative ECG:
    • Common and benign post-operative changes include:
      • RBBB
      • Pericarditic changes
    • Concerning changes include:
      • Heart block
        Indicates AV nodal dysfunction, particularly after valvular surgery.
      • STE in continguous leads in a grafted vascular territory
        May be acute graft failure.
      • Anterior STE
        LIMA spasm in a LIMA-LAD graft.
      • Low voltage
        Consider tamponade.
  • CXR
    • Pneumothorax
    • Device position
      ETT, PAC, NGT, ICC, drains.
  • Bloods
    Depending on degree of concern.
    • AVG
    • Electrolytes
    • Coagulation status
    • TEG
    • Cardiac markers
      Always elevated post-cardiac surgery, but are useful in trending changes.

Management

The goal for the uncomplicated intubated post-operative cardiac patient is to rewarm, desedate and ensure adequate analgesia, wean ventilator support, and extubate.

General post-operative trajectory:

Specific post-operative considerations for different procedures are under the relevant operation in the cardiac anaesthetic section.

  • C
    • Remove PAC
      Once HDx stable for 6 hours on minimal vasoactive suppport.
    • Remove other invasive lines
      As able.
    • Remove pacing wires
      • Once there has been no pacing requirement for 24 hours, wires can be isolated, i.e. removed from the pacing box
        This improves mobility whilst still allowing pacing to be restarted if required.
      • Wires can be removed after a further 24 hours, provided there is no coagulopathy
  • D
    • Analgesia
    • Wean sedation
      Short acting agents preferred.
  • E
    • Warming
      Should be rewarmed to >36°C. This:
      • Reduces arrhythmia
      • ↓ SVR and myocardial work
      • Improves coagulopathy
  • F
    • Electrolytes
      • Hypokalaemia
        Aim 4.5-5mmol/L.
      • Hypomagnesaemia
        Aim >1mmol/L.
    • Urine output
      Polyuria dominates the early post-operative period, but usually resolves in ⩽6 hours.
    • Remove IDC
      Second post-operative day if mobilising.

Complications

Key issues in the post-cardiac surgical patient include:

  • Bleeding
  • Haemodynamic instability
  • AF
  • Cardiac tamponade

Bleeding

Medical bleeding, due to abnormalities of coagulation:

  • Causes:
    • Platelets
      • Qualitative abnormality
        Platelet function is ↓ by:
        • Preoperative use of antiplatelet agents
        • Cardiopulmonary bypass
          Greater bypass duration is associated with greater impairment.
      • Quantitative abnormality
    • Coagulation abnormality
      • Residual heparinisation
      • Haemodilution
      • Consumption
    • Fibrinogen
      • Plasminogen is activated by CPB
  • Treatment:
    • Normalise temperature
    • Prevent hypertension
    • Correct platelet dysfunction:
      • Platelet transfusion
        Aim functional platelet count >100 × 109 in significant bleeding.
      • DDAVP
        Aim to improve platelet function.
        • 20μg IV
    • Correct coagulopathy
      Aim to normalise APTT and PT.
      • Typically 20ml/kg of FFP
    • Correct fibrinogen
      Aim to keep fibrinogen >1g/L.
    • Prevent fibrinolysis
      Consider in the setting of fibrinolysis (i.e. elevated D-Dimer and low fibrinogen).
      • TXA
    • ↑ mediastinal pressure
      Theoretically reduce venous bleeding.
      • ↑ PEEP
      • Raise head of bed

Surgical bleeding, due to uncontrolled (typically arterial) source. Suggested by:

  • Bleeding with normal coagulation parameters
  • Bleeding following period of extreme hypertension
    Anastomotic breakdown.
  • Large volume drain outputs

    • 500ml in 1 hour

    • 400ml/hr for 2 hours

    • 300ml/hr for 3 horus

    • 200ml/hr for 4 hours

Causes of Haemodynamic Perturbation

Haemodynamic impairment can be divided into problems with:

  • Heart Rate/Rhythm
    • Tachycardias
      • Pacing malfunction
      • Electrolytes
      • AF
    • Bradycardia
      • Pacing malfunction
      • Electrolytes
      • Ischaemia
  • Preload
    • Hypovolaemia
      Associated with lower filling pressures, and accentuated by diastolic dysfunction.
      • Bleeding
      • Diuretics
      • Rewarming
      • Vasodilators
    • ↑ Intrathoracic pressure
      • Pneumothorax
      • Excessive PEEP
    • ↑ Intrapericardial pressure
      • Tamponade
        Elevation and equalisation of diastolic pressures.
    • RV failure
  • SVR/
    • ↑ LV afterload:
      • Aortic valve dysfunction
      • Excessive vasoconstrictors
      • Dynamic outflow tract obstruction
    • ↓ LV afterload:
      • SIRS
      • Post-pump vasoplegia
      • Anaphylaxis
        • Protamine reactions
      • Excessive vasodilator therapy
      • Thyroid dysfunction
      • Adrenal insufficiency
    • ↑ RV afterload:
      • Acidosis
      • Hypoxia
      • Excessive PEEP
      • Thromboembolism
  • Contractility
    • Ischaemia
      • Acute graft dysfunction
      • Air embolus
        Predominantly RCA.
    • Inadequate myocardial protection
      • Myocardial stunning
        Long bypass time.
      • Ventricular dilatation
      • Inadequate cardioplegia
    • Pre-existing ventricular dysfunction

Cardiac Tamponade

Post-surgical tamponade:

  • Occurs in up to 5%
  • May emerge slowly
  • Combination of clinical suspicion and echocardiographic diagnosis
  • Features (not all of which may be present):
    • Tachycardia
    • Low UO
    • Fall in SV/2
    • Elevation and equalisation of diastolic pressures
      RAP ≃ PADP ≃ PCWP. May not occur if a small clot impedes filling to only one chamber.
    • Loss of y-descent on CVP waveform Indicates that the pressure gradient between the atria and the ventricles is reduced.
    • Loss of mediastinal drain output
    • Echocardiography evidence of tamponade
  • Treatment
    • Resternotomy and evacuation of clot

Atrial Fibrillation

AF occurs in 10-40% of post-cardiac surgery patients, and is associated with significant morbidity:

  • ↑ CVA risk (3x)
  • ↑ Inotrope requirement
  • ↑ Reoperation
  • ↑ ICU and hospital LoS

Risk factors include:

  • Age
  • Use of cardiac supports:
    • Inotropes
    • IABP
  • Previous AF
  • Valvular heart disease

Prevention strategies include:

  • Antiarrhythmics
    • Beta-blockade
    • Amiodarone
    • Diltiazem
    • Sotalol
  • Procedural
    • Bi-atrial pacing
  • Anti-inflammatories
    • Statins
    • Dexamethasone
    • Colchicine

Treatment strategies:

  • Pharmacological
    • Rhythm control
      • Amiodarone
      • Magnesium
    • Rate control
      • Beta-blockade
      • Diltiazem
      • Digoxin
    • Anticoagulation
      Consider if >48 hours.
  • Procedural
    • Electrical cardioversion

Renal Failure

Post-operative AKI:

  • Occurs in 1-5%
  • Significant associated morbidity and mortality

Other

Other complications of cardiac surgery include:

  • C
    • Permanent pacing
      • AVR + MVR: 11%
      • MVR: 8%
      • AVR: 5%
  • D
    • Delirium/POCD 10-20%.
    • Stroke
      1-5%.
  • G
    • Mesenteric ischaemia
      • Embolic
  • I
    • Infection
      • Deep sternal wound infection in 1-2%
        Significant morbidity.

Key Studies

  • TRICS-III (2017)
    • 5092 non-pregnant, non-lactating, adult standard cardiac surgical patients (not heart transplants or VAD) with EUROSCORE I >6
    • Randomised, allocation concealed, assessor blinded, multicentre (73), international RCT
    • 90% power for 3% non-inferiority margin for composite of death, MI, inpatient RRT
    • Restricted vs. liberal transfusion
      • Restrictive
        Transfused if Hb <75g/dL.
      • Liveral
        Transfused if Hb <95g/dL intraoperatively or in ICU, or <85g/dL once discharged from ICU.
    • No difference in primary outcome (11.4% vs. 12.5%), or any secondary outcomes
      • Subgroup showed restrictive transfusion ↓ primary outcome in >75 year olds
    • ~50% of the liberal group were transfused an average of 2 units, compared to 7~3% of the liberal group (3 units)

References

  1. Melanson, P. Management of post-op cardiac surgery patients. 2001. McGill.
  2. Mazer CD, Whitlock RP, Fergusson DA, et al. Restrictive or Liberal Red-Cell Transfusion for Cardiac Surgery. New England Journal of Medicine. 2017;377(22):2133-2144. doi:10.1056/NEJMoa1711818