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1
Q

Hypotension post-cardiac surgery

Acronym?

A

PROVED?

Pump, rhythm, obstruction, volume, (endocrine), distributive, ? = artefactual

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2
Q

Hypotension post-cardiac surgery

Possible sources of error/artefacts (7)

A
  • examine the patient for pulses and check for symmetry
  • transducer error: check transducer, zero, level, calibrate, NIBP
  • damping of waveform: assess damping co-efficient, replace
  • NIBP malfunction: check cuff (size, fit, connection)
  • check inotrope infusions into patient
  • Radial/ central arterial monitoring discrepancy with severe vasoconstriction
  • Upper limb vascular disease (radial arterial line) or obstruction (e.g. dissection or aorto-occlusive disease: femoral arterial line)
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3
Q

Causes of hypovolaemia post cardiac-surgery

Two main categories?

Approach to each?

A

Bleeding

Check drains, dressings, CXR, give fluids/blood products, correct coagulopathy/temperature

Diuresis

Check urine output and sodium

Give fluids

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4
Q

Approach to haemodynamic instability post-op

Four categories

A

Heart rate & rhythm

Preload

Afterload

Contractility

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5
Q
A
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6
Q

Causes of heart rate/rhythm issues leading to hypotension

(2 categories, 2+3 examples)

A

Tachydysrhythmia

  • Pacing malfunction
  • Electrolyte imbalance

Bradydysrhythmia

  • Pacing malfunction
  • Electrolyte imbalance
  • Ischaemia
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7
Q

Causes of altered preload leading to hypovolaemia

4 categories

3,2,1,2examples

A

Hypovolaemia

  • Bleeding
  • Diuresis (esp post bypass)
  • Rewarming/vasodilator therapy

Increased intrathoracic pressure

  • Excessive PEEP
  • Pneumothorax

Increased intra-pericardial pressure

  • Tamponade

RV failure

  • Contractility
  • Increased RV afterload
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8
Q

Causes of altered afterload leading to hypovolaemia

3 categories

3,4,4 examples

A

Increased LV afterload

  • Aortic valve dysfunction
  • Excessive vasoconstrictor therapy
  • Dynamic outflow tract or mid-cavity obstruction

Decreased LV afterload

  • SIRS
  • Post CPB vasoplegia
  • Anaphylaxis
  • Excessive vasodilator therapy

Increased RV afterload

  • Acidosis
  • Hypoxia
  • Excessive PEEP
  • Thromboembolism
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9
Q

Causes of altered contractility leading to hypotension post-op

3 categories

2, 1, 1 examples

A

Ischaemia

  • Acute graft dysfunction
  • Air embolus (particularly RCA)

Inadequate myocardial protection on CPB

  • Inadequate cardioplegia or ventricular dilatation

Pre-existing ventricular dysfunction

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10
Q

Initial priorities following handover

10 categories

Aims for each category

Tasks for each category

A

Ventilation

Aim: Ensure initial settings adequate

Tasks

  • Check PIP waveforms + patient ventilator synchony
  • Check ETT size and position at teeth

Monitor

Aim: Display all relevant information

Tasks

  • Zero all pressure
  • Ensure correct channel display
  • Set up cardiac output monitor

Examination

Aim: Rapid assessment

Tasks

  • Pupils, GCS, Temp, Peripheral perfusion, Neck veins, Breath sounds, Heart sounds, Mediastinal/pleural drain outputs, Urine output

Infusions

  • Check infusion pumps, check volume remaining

Investigations

  • Blood gas, Formal bloods, CXR

Fluids and electrolytes

  • Chart fluid bolus

Drugs

  • Antiemetics/analgesia
  • Electrolyte replacemnt

Pacing ​

Glucose

Documentation

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11
Q

Main cardiovascular complications of cardiac surgery (6)

A
  • Cardiac tamponade
  • Low CO/organ dysfunction
  • Periperative MI
  • Arrhythmias
  • Stroke
  • Peripheral/mesenteric ischaemia
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12
Q

Cardiac tamponade

Frequency

Signs (7)

Prevention (3)

Treatment (3)

A

0.5–6% of the patients within the first 24–48 postoperative hours

Hypotension, tachycardia, elevated CVP, reduced UO, pulsus paradoxus, dyspnoea, mental confusion

Administer prophylactic drugs to reduce bleeding risk/haemostasis, frequent suction of chest drains

Evacuation of pericardial space via pericardiocentesis or re-sternotomy, fluids, vasopressors

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13
Q

Most common mechanism of acute LV dysfunction (3)

What is myocardial stunning? Frequency? Treatment?

A

The most common mechanisms of the acute LV systolic dysfunction are myocardial ischaemia, acute myocardial infarction (AMI), and myocardial stunning.

Myocardial stunning occurs in about 45% of the patients undergoing elective cardiac surgery. It is represented by viable myocardium that has suffered from prolonged coronary hypoperfusion
during heart surgery. Therefore, the causal mechanism of stunning is the ischaemic reperfusion injury. The systolic dysfunction correlated with myocardial stunning is generally transient and responsive to positive inotropes with a complete recovery of the heart function in the early postoperative hours

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14
Q

Which risk model is used to calculate risk of death following a heart operation?

A

EuroSCORE II

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15
Q

What are the benefits of cardioplegia?

What are the effects of temperature of cardioplegic solutions?

What are the two main types of solution?

What are the two main types of delivery?

A

Hypothermic cardioplegia is commonly employed
in cardiac surgery to provide heart standstill. It reduces myocardial oxygen demand and it reverses the ischaemic injury-carrying oxygen and metabolic substrates.

Hypothermic marginally reduces MvO2 but increases plasma viscosity and activates cold agglutinins. No difference in adverse effects between warm and cold but better recovery after warm.

Blood vs crystalloid solutions. Blood may be better but no mortality benefit.

Can be delivered antegrade (through aortic root/coronary ostia) and retrograde (through coronary sinus).

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