2-4. Hypotension

SJH Theatres and Anaesthetics
NHS Lothian

Objectives

Hypotension is commonly due to unnecessarily deep anaesthesia, the autonomic effects of neuraxial block, hypovolaemia or combined causes.

You should rapidly exclude a problem in adequate oxygen delivery, airway and breathing first.

START

❶ Adequate oxygen  delivery

  • Pause surgery if possible.
  • Increase fresh gas flow AND give 100% oxygen AND check measured FiO2.
  • Visual inspection of entire breathing system including valves and connections.
  • Rapidly confirm reservoir bag moving OR ventilator bellows moving.

❷ Airway

  • Check position of airway device and listen for noise (including larynx and stomach).
  • Check capnogram shape compatible with patent airway.
  • Check airway AND airway device are patent (consider passing suction catheter).

❸ Breathing

  • Check chest symmetry, rate, breath sounds, SpO2, measured VTexp, ETCO2.
  • Feel the airway pressure using reservoir bag and APL valve <3 breaths.
  • Exclude high intrathoracic pressure as a cause.

 ❹ Circulation

  • Check heart rate, rhythm, perfusion, recheck blood pressure.
  • If heart rate <60 bpm consider giving anticholinergic drug (Box B).
  • Consider giving vasopressor (Box C) and positioning (e.g. move head down).
  • Consider fluid boluses (250 ml adult, 10 ml.kg-1 paediatric).
  • If heart rate >100 bpm sinus rhythm, treat as hypovolaemia: give i.v fluid bolus.
  • If heart rate >100 bpm and non-sinus → 2-7 Tachycardia.

❺ Depth

  • Ensure correct depth of anaesthesia AND analgesia (consider risk of awareness).

❻ Exclude potential surgical causes (Box D) – discuss with surgical team.

❼ Consider causes in Box E and call for help if problem not resolving quickly.

 

 

Box A: CRITICAL CHANGES

If problem worsens significantly or a new problem arises, call for help and go back to START of 1-1 Key basic plan.

Box B: ANTICHOLINERGIC DRUGS

  • Glycopyrrolate 5 μg.kg-1 (adult 200-400 μg)
  • Atropine 5 μg.kg-1 (adult 300-600 μg)

Box C: VASOPRESSOR DRUGS

  • Ephedrine 100 μg.kg-1 (adult 3-12 mg)
  • Phenylephrine 5 μg.kg-1 (adult 100 μg)
  • Metaraminol 5 μg.kg-1 (adult 500 μg)
  • Adrenaline 1 μg.kg-1 (adult 10-100 μg) in emergency only

Box D: SURGICAL CAUSES

  • Decreased venous return (e.g. vena cava compression / pneumoperitoneum)
  • Blood loss (unrecognised / undeclared / occult)
  • Vagal reaction to surgical stimulation
  • Embolism (gas / fat / blood / cement reaction)
 

Box E: DON’T FORGET!

  • Consider whether you could have made a drug error.
  • Pneumothorax and/or high intrathoracic pressure can cause hypotension.
  • Also consider:
  • Cardiac ischaemia → 3-12
  • Anaphylaxis → 3-1
  • Cardiac tamponade → 3-9
  • Local anaesthetic toxicity → 3-10
  • Sepsis → 3-14
  • Cardiac valvular problem
  • Endocrine cause (eg steroid dependency)

 

 

Editorial Information

Author(s): The Association of Anaesthetists of Great Britain & Ireland 2018. www.aagbi.org/qrh Subject to Creative Commons license CC BY-NC-SA 4.0. You may distribute original version or adapt for yourself and distribute with acknowledgement of source. You may not use for commercial purposes. Visit website for details. The guidelines in this handbook are not intended to be standards of medical care. The ultimate judgement with regard to a particular clinical procedure or treatment plan must be made by the clinician in the light of the clinical data presented and the diagnostic and treatment options available..

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