Circulation

Primary causes of dysfunction

Supraventricular tachycardia (a/w increased risk of cardiac event)
- Sinus
  - Caused by pain/anxiety, fever, hypovolaemia, hypovolaemia/anaemia, PE; less commonly heart failure, MI, thyrotoxicosis, phaeochromocytoma
- Atrial
  - AF
    - See separate topic under 'Cardiology'
  - Atrial flutter
    - Regular flutter P waves at 300/min. QRS is normal with variable AV block. There is usually underlying cardiac disease.
    - AF and flutter may be present in the same patient.
    - May respond to adenosine
    - Treatment is cardioversion, digoxin or verapamil.
- Paroxysmal SVT
  - Any tachycardia originating in AV node, atria or sinoatrial node
  - Changes to P waves or missing P waves
Ventricular
- PVC
  - Consider hypoxia, hypokalaemia, hypocapnia
- Ventricular tachycardia
- VF

Bradyarrhythmia
- Problematic if associated with hypoperfusion or hypotension
- Causes:
  - Autonomic
    - Pain, especially visceral
    - Raised ICP
    - Beta-blockers
    - Epidural
  - Non-autonomic
    - MI, especially inferior MI
    - Sepsis
    - Hypoxia
    - Digitalis toxicity
    - Hypothyroidism
    - Hypothermia
- Management:
  - Atropine 0.6-1.2mg may help
  - Pacing may be needed
  - Isoprenaline infusions can be used in ICU
Heart block
- RBBB
  - Right ventricular depolarisation occurs via the left ventricle
  - M-shaped QRS in V1, V2 and V3
  - RBBB with left axis deviation suggests bifascicular block - discuss with cardiology
- Left ventricle depolarises via right ventricle
- M-shaped QRS in V5, V6, I and aVL. W-shaped QRS in reciprocal leads, III and aVF

Most important thing is haemodynamics initially.
- Assess:
  - Vitals
  - Peripheral perfusion
  - Cardiac ischaemia/CHF
  - Level of consciousness
  - Management:
  - For all arrhythmias:
    - Check and correct electrolytes
    - Oxygen if needed
    - Optimise fluid
ECG
?telemetry
Tachyarrhythmia:
- Unstable - cardioversion
- Stable:
  - Supraventricular - may respond transiently to valsalva. beta blockers/digoxin/amiodarone. Adenosine 6mg or 12mg can be given to block the AV node (avoid in asthmatics and the presence of dipyridamole, but otherwise relatively safe in inexperienced hands).
  - Paroxysmal SVT: vagal stimulation or adenosine
  - VT: lidocaine/procainamide/amiodarone can be given. Cardioversion generally required. Especially urgently if there is compromised cardiac output.
Bradyarrhythmia:
- Sustained - atropine or beta adrenergic agonist
- Transient - nothing
Heart block:
- Persistent high-grade second degree or third degree: insertion of PPM

Aetiology
- Conditions affecting preload
  - Hypovolaemia
  - Fluid overload (most common perioperatively)
  - Pneumothorax/cardiac tamponade
- Conditions affecting intrinsic myocardial function
  - Ischaemia
  - Infarction
  - Dysrhythmias
  - Chronic heart failure
  - Hypocalcaemia (and other electrolytes)
  - Myocardial depressant factors (e.g. sepsis)
  - Pneumothorax/cardiac tamponade
- Conditions affecting afterload
  - Aortic/pulmonary valvular stenosis
  - PE
  - Pneumothorax/cardiac tamponade
  - Aortic dissection
Diagnosis
- Acute dyspnoea, orthopnoea and tachypnoea
- Tachycardia, diaphoresis, hypertensive
- Gallop rhythm
- Bibasal crepitations, wheeze (cardiac asthma), pink frothy sputum
- CXR - fluid in the horizontal fissure, peribronchial cuffing, upper lobe diversion, perihilar bat's wing appearance, Kerley B lines (rare)
Treatment:
- Administer oxygen
- ECG
- Treat any underlying cause
- Sit patient up
- Consider CPAP
- Diuretics
- IV opioids can help
- Reduce afterload if possible (nitrates)
- Consider ICU
Cardiogenic shock
- Severe impairment of cardiac function with BP <90mmHg (or 30mmHg less than 'normal')
- Most common causes are severe myocardial ischaemia or infarction

Refer to cardiology if BP persistently >220/120mmHg with signs of organ dysfunction

BP
- Non-invasive
- Invasive
  - Easiest is probably arterial at radial artery
  - Central venous pressure
    - Indicates preload of pulmonary circulation and a rough guide to systemic preload
    - Best route in elective setting is internal jugular vein with USS
    - Does NOT equal intravascular volume
    - Subject to a lot of variables
    - Indications:
      - Fluid replacement for hypovolaemia when conventional access is impossible or going to be difficult to manage
      - Measure effect of vasoactive drugs on venous capacitance
      - Aid diagnosis of RHF
Trans-oesophageal Doppler
- Measures blood velocity in the descending aorta
TTE/TOE
- Assessment of preload and cardiac contractility before and after an intervention
- Diagnosis of major cardiac structural abnormalities

For haemodynamic drugs, see separate topic under 'Pharmacology'