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Cardiac arrest - the human factor

Critical incident technique analysis applied to perianaesthetic cardiac arrests at a university teaching hospital.
Erik H Hofmeister, Rachel A Reed, Michele Barletta, Molly Shepard & Jane Quandt.  
Veterinary Anaesthesia and Analgesia 2018 (45), 345-350

What did the study find?

16 cats and dogs experienced perianaesthetic cardiac arrest during a 36-month period at a university teaching hospital. The majority of arrests were attributed to animal and human factors (14 and 12 cases respectively).  Arrests because of procedural, drug and equipment factors were uncommon (4, 1 and 1 respectively). Most animals experienced more than one factor and two animals arrested after a change in recumbency (considered a human factor).  The study concluded that future work should focus on the root cause of the arrests and interventions should be designed to minimise all factors, particularly human ones.

Study design

The objective of this study was to apply the Critical Incident Technique (CIT) methodology to a series of perianaesthetic cardiac arrest events at a university teaching hospital in order to describe the factors that contributed to the cardiac arrest.

A group of 16 dogs and cats that suffered a perianaesthetic cardiac arrest between November 2013 and November 2016 were analysed.  Perianaesthetic cardiac arrests were defined as those occurring between premedication and transfer to another service following recovery.  The case history and events leading up to the arrest were debated using CIT methods, within 7 days of the event.  2 board-certified anaesthetists assessed the case history, intensive care records, surgery and pathology reports, client communication logs and the description of the events leading up to the arrest.  This was followed by a discussion of what could have been done to change the outcome. 

Data, in the form of excerpts and quotations, was generated to provide a description of events and to determine the contributing factors in the cardiac arrest.  Possible sources of error were classified as: animalhumanproceduralequipment and drug factors.

No assessment was performed on the outcomes of the cardiac arrest, only the events leading up to the incident. 


Of the 16 cardiac arrest cases examined the most common contributing factor was animal (n = 14), followed by human (n = 12), procedural (n = 4), drugs (n = 1) and equipment (n = 1). The majority (n = 11) of animals had multiple factors identified.Two animals arrested after a change in recumbency (considered a human factor).

Animal factors were largely attributed to the severity of illness of the animal, such as a rapidly worsening intracranial neurologic disease or severe pulmonary disease. This is consistent with prior findings, where more than half of perianaesthetic arrests were in animals with significant pathology.

Human factors were attributed to deficient planning, the skill of the anaesthetist, the skill of the clinician doing the procedure and rapid changes in recumbency (possible orthostatic hypotension).  Deficient planning included cases where more thorough monitoring was indicated but not carried out; cases where more thorough preparation of the animal was indicated but not carried out; and cases where a thorough workup was not conducted.  Errors related to the skill of the anaesthetist included equipment knowledge; intubation skill; and not identifying a tension pneumothorax rapidly. Errors related to the skill of the clinician included length of time taken to complete the procedure.  Two animals arrested because of a rapid change in recumbency

Procedural factors were assigned when cardiac arrest occurred during the primary intervention and there was contribution from another issue e.g rupture of a blood vessel. 

The one equipment factor was a result of an internal pacemaker failing.

There was one cardiac arrest attributed to a drug factor.

Why is this important? 

The events leading up to a perianaesthetic cardiac arrest have not been previously documented in small animals, but this study has demonstrated where we can potentially improve outcomes.

Some animals are extremely poor anaesthetic candidates and anaesthesia may complicate their existing disease to the point where cardiac arrest occurs.  In such cases it is particularly important to communicate the potential risks to clients.

The human factors show the greatest potential for intervention to improve the likelihood of a positive outcome. Deficiencies in planning create an environment where subsequent errors tend to become compounded.  Therefore, thorough workups and preparation for anaesthesia may decrease the likelihood of planning errors contributing to a perianaesthetic arrest. Deficiencies of skill or knowledge are inherent in any human system, so the careful training/supervision of students and other clinical personnel is essential. It should be noted however, that this study was performed in a university teaching hospital and may not reflect the situation in general practice.

Changes in body position in anaesthetised animals should occur slowly and be undertaken carefully with close monitoring of the animal.

Article by
Dr. Karen Heskin

Veterinary Technical Manager, Jurox UK

Originally published: Thursday, 30th August 2018

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