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Crisis management during anaesthesia: bradycardia

¹ Senior Staff Specialist and Director, Sydney Medical Simulation Centre, Royal North Shore Hospital, St Leonards, New South Wales, Australia
² Director, Research and Development, Sydney Medical Simulation Centre, Royal North Shore Hospital, St Leonards, New South Wales, Australia
³ Deputy Director, Department of Paediatric Anaesthesia and Pain Management, Royal Children’s Hospital, Parkville, Victoria, Australia
⁴ Consultant Specialist, Australian Patient Safety Foundation and Visiting Research Fellow, University of Adelaide and Royal Adelaide Hospital, Adelaide, South Australia, Australia

Correspondence to:
Professor W B Runciman
President, Australian Patient Safety Foundation, GPO Box 400, Adelaide, South Australia 5001, Australia; research{at}apsf.net.au 11 January 2005

	ABSTRACT

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Background: Bradycardia in association with anaesthesia may have many potential causes and associated conditions, some rare and/or obscure. A prompt appropriate response is important as some homeostatic mechanisms may be impaired under anaesthesia.

Objectives: To examine the role of a previously described core algorithm "COVER ABCD–A SWIFT CHECK", supplemented by a specific sub-algorithm for bradycardia, in the management of bradycardia occurring in association with anaesthesia.

Methods: The potential performance of this structured approach for each of the relevant incidents among the first 4000 reported to the Australian Incident Monitoring Study (AIMS) was compared with the actual management as reported by the anaesthetists involved.

Results: From the first 4000 incidents reported to AIMS, 265 reports which described bradycardia during anaesthesia were extracted and studied. Bradycardia was associated with hypotension in 51% of cases, cardiac arrest in 25% of cases and hypertension in one case. In 22% of reports apparent desaturation or an abnormality of ventilation was described. Bradycardia was caused by drug events (28%), airway related events (16%), autonomic reflexes (14%), and regional anaesthesia (9%). Airway and drug events caused 75% of cases involving children. It was considered that, correctly applied, the core algorithm COVER would have diagnosed 53 cases (20%) and led to corrective management in 45 (85%) of these; this included an important subset of airway and ventilation problems. Completion of COVER ABCD–A SWIFT CHECK followed by the specific sub-algorithm for bradycardia would have resulted in diagnosis and appropriate management in all but two cases. It would have led to earlier recognition of the problem and/or better management in 11 cases (4%) when compared with the actual management described in the reports.

Conclusion: Steps should be taken to manage bradycardia whilst associated conditions are managed concurrently. Analysis of cardiac rhythm should not be pursued to the exclusion of supportive therapy. The use of a structured approach in the management of bradycardia associated with anaesthesia is likely to improve management in the small percentage of cases in which the diagnosis of the cause may be missed or delayed.

Keywords: bradycardia; bradydysrhythmia; crisis management; anaesthesia complications

Cardiac output is determined by the product of heart rate and left ventricular stroke volume. The contribution of both atrial and ventricular contraction to the stroke volume underlies the significance of normal cardiac rhythm and conduction in the generation of cardiac output. Bradycardia may result in an insufficient rate to sustain cardiac output and hence oxygen delivery to tissue beds. This is particularly so in the case of young children in whom cardiac output is more affected by changes in heart rate than stroke volume. In older patients bradycardia may reflect an ischaemic myocardium which is unable to maintain a stable electrical rhythm as a result of systemic hypotension or hypoxaemia. A prompt appropriate response to bradycardia under anaesthesia is important as some causes are rare and/or obscure and homeostatic mechanisms may be impaired by anaesthetic agents. It was decided to examine the role of a structured response to bradycardia under anaesthesia as there are many potential causes and associated conditions.

In 1993 a "core" crisis management algorithm represented by the mnemonic COVER ABCD–A SWIFT CHECK (the AB precedes COVER for the non-intubated patient) was proposed as the basis for a systematic approach to any crisis during anaesthesia where it is not immediately obvious what should be done or where actions taken have failed to remedy the situation.¹ This was validated against the first 2000 incidents reported to the original Australian Incident Monitoring Study (AIMS). AIMS is an ongoing study which involves the voluntary anonymous reporting of any unintended incident which reduced or could have reduced the safety margin for a patient.²

It was concluded that, if this algorithm had been correctly applied, a functional diagnosis would have been reached within 40–60 seconds in 99% of applicable incidents, and that the learned sequence of actions recommended by the COVER portion would have led to appropriate steps being taken to handle 60% of problems relevant to this portion of the algorithm.¹ This study also showed that the 40% of problems represented by the remainder of the algorithm ABCD–A SWIFT CHECK were not always promptly diagnosed or appropriately managed.^1–3 It was decided that it would be useful for these remaining problems to develop a set of sub-algorithms in an easy-to-use crisis management manual.⁴ This study reports on the potential place of the COVER ABCD–A SWIFT CHECK algorithm in the diagnosis and initial management of bradycardia, provides an outline of a specific crisis management sub-algorithm for bradycardia during anaesthesia, and provides an indication of the potential value of using this structured approach.

	METHODS

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Of the first 4000 incidents reported to AIMS, those which made reference to bradycardia or bradydysrhythmia were extracted and analysed with respect to the following criteria: anaesthetic technique, patient’s ASA grading, phase of anaesthesia at the time of presentation, presenting features (cardiac rhythm, blood pressure, oxygen saturation), presumed precipitating cause, management and outcome. The algorithm COVER–A SWIFT CHECK algorithm, described elsewhere in this series of articles,⁴ was applied to each relevant report to determine the stages at which the problem might have been diagnosed and to confirm that activating the COVER portion would have led to appropriate initial steps being taken.

As bradycardia is not adequately dealt with by this algorithm, a specific sub-algorithm for bradycardia was developed (see fig 1) and its putative effectiveness was tested against the reports. How this was done is described elsewhere in this series of articles.⁴ The reports were used in conjunction with contemporary guidelines on resuscitation^5–9 to generate a differential diagnosis and management algorithm which was especially relevant to anaesthesia. The potential value of this structured approach—that is, the application of COVER ABCD–A SWIFT CHECK to the diagnosis and management of the problem followed by the application of the bradycardia sub-algorithm—was assessed in the light of the AIMS reports by comparing its potential effectiveness for each incident with that of the actual management as recorded in each report. In addition to determining a difference between the two approaches with respect to likelihood of correct diagnosis and management, it was of particular interest during this part of the project to evaluate if delays in diagnosis and overall outcome could be improved with the application of the sub-algorithm.

View larger version (65K): [in this window] [in a new window]   Figure 1  Bradycardia.

	RESULTS

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Problems with the airway or ventilation were described in 58 reports. These included desaturation on pulse oximetry, difficulty with ventilation, clinical cyanosis, or symptoms of dyspnoea. On eight occasions no specific cause of the problem could be found with the airway; it is possible that the desaturation represented an artefact or true desaturation resulting from altered ventilation-pulmonary blood flow matching. The remaining 50 cases were associated with real airway abnormalities. This represented 19% of all reports describing bradycardia and 16% of total causes described when multiple causes were accounted for. The specific nature of these airway events is shown in table 5.

Vagal reflexes were considered to have contributed to bradycardia in 45 reports, which represented 14% of the 319 causes described. These reflexes were surgically induced in 36 cases. The majority of these were attributed to either vagal stimulation in the abdominal cavity or pelvis (n = 13) or the oculocardiac reflex (n = 12). Anaesthetic causes included laryngoscopy (n = 4) and intravenous cannulation (n = 2).

Surgical events were associated with 13 reports (5%). These included reaming, cementing or manipulating fractured hips (n = 4), manipulation of wires or catheters in central veins (n = 4), and pneumoperitoneum (n = 2).

Diagnosis
Bradycardia was described with abnormalities of blood pressure in 202 reports (76%). Bradycardia in association with a state of cardiac arrest, as defined by the absence of a peripheral pulse or the presence of a cardiac rhythm incompatible with a cardiac output (sinus arrest, asytole), was described in 67 reports (25%). Within this group, 24 cases involved degeneration from an initial state of hypotension into a pulseless state. Bradycardia was associated with hypotension in 134 cases (51%) and hypertension in one (<1%). There was no significant change in blood pressure in the remaining 63 cases (24%).

The prevailing rhythm when bradycardia was detected was specifically described as sinus rhythm in 74 reports. In another 135 reports sinus bradycardia was inferred from the narrative (table 6). Together, these account for 79% of cases.

Management
The management of bradycardia as described in the narrative of the reports was classified as either conventional or non-conventional based upon the guidelines of the American Heart Association (AHA),⁵ the International Committee on Resuscitation,⁶ and the Australian Resuscitation Council (ARC).^7–9 It was subdivided into five grades which ranged from simple supportive measures to tertiary management (table 7)

Outcome
The outcome from bradycardia is shown in table 8; 37% of reports described a poor outcome. Reports were considered to have a poor outcome if they were not resolved by the completion of the normal recovery period. An exception to this was ECG evidence of myocardial ischaemia or other cardiac events which may have resolved but often resulted in overnight monitoring.

Verification of the sub-algorithm
When COVER ABCD–A SWIFT CHECK was applied to each report it was considered that the problem would have been detected in all cases either at the C1 stage of COVER or at C of ABCD. Fifty three cases (20%) were diagnosed of which 45 (85%) would also have received correct management as a result of applying the core algorithm COVER. The majority of these dealt with circuit problems V1 (n = 3), vaporiser incidents V2 (n = 34), problems arising from monitors R1 (n = 5), equipment malfunction or errors with non-anaesthetic drugs R2 (n = 11). The remaining cases required completion of the sub-algorithm for bradycardia; this failed to provide a diagnosis or appropriate corrective management in two cases. Asymmetrical radial pulses and an under-reading central venous pressure monitor were responsible in these situations. It was felt that the algorithm performed better than the reporter in 11 cases (4%): missed or delayed diagnoses (n = 7), inappropriate use of drugs (n = 3), and failure to improve monitoring (n = 1). Non-conventional management was not included here unless it was felt to have adversely affected the outcome.

	DISCUSSION

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The specific sub-algorithm for bradycardia is shown in fig 1. It draws heavily upon the differential diagnosis and management strategies presented in the reports because they specifically deal with bradycardia within the context of anaesthesia.

Analysis of the AIMS reports shows that, in the majority of cases, bradycardia is managed appropriately. It is clear, however, that deficiencies in problem solving which have been identified in other arenas also exist in anaesthesia. For example, ARC guidelines on basic and advanced cardiac life support are clear on the institution of ECC in pulseless states. On a number of occasions in the reports there was a failure to interpret loss of peripheral pulses as a cardiac arrest. Not enough information was available to attempt to associate this with a poor outcome. However, it was interesting to observe that, in approximately half of the cases of cardiac arrest in which ECC was not described, cardiovascular collapse followed an initial presentation of bradycardia with hypotension. The conventional management of asystole includes early adrenaline. Atropine is recommended as a second line agent in refractory asystole or in the initial management of bradycardia associated with hypotension. The AIMS reports describe several cases of cardiac arrest in which a successful outcome was achieved with the use of atropine instead of adrenaline. Atropine without ECC was used successfully in five cases of reflex induced sinus arrest. If necessary, cardiac pacing should be instituted.¹⁰

The sub-algorithm begins with a reconsideration of the core algorithm COVER ABCD–A SWIFT CHECK as an initial response, as the causes of 20% of cases of bradycardia can be expected to be diagnosed as a result. The high incidence of airway or ventilation related events lends further support to this approach. It is easy to visualise the difficulties and delays one might encounter in managing a crisis situation in which it is not clear whether the primary problem is airway, heart rate, or blood pressure. COVER ABCD–A SWIFT CHECK enables cross referencing with airway related problems which are represented on other pages of the crisis manual. This establishes a system by which airway problems can be diagnosed and managed definitively at the same time that supportive measures to restore heart rate and blood pressure are instituted. This is important because aggressive resuscitation of the cardiovascular system may follow an episode of hypoxaemia and the possibility of multiple causes for bradycardia will always need to be considered.

Key messages From the first 4000 reports to AIMS, 265 reports (7%) which described bradycardia were studied; 84% of these were adults and 16% were children under 14 years of age. More than half (62%) were graded ASA I or II. Bradycardia occurred most commonly in the maintenance phase (61%). Among 319 reported causes, the most common were drug events (28%), airway or ventilation problems (16%), autonomic reflexes (14%), epidural or spinal anaesthesia (9%). Airway events were the predominant cause of bradycardia in children (47%). Hypotension was less common (21%) but cardiac arrest more common (32%) than in adults. Cardiopulmonary events causing bradycardia are more likely than other causes to be associated with cardiac arrest. Neuraxial blockade causing bradycardia had the commonest association with hypotension. Surgical events were associated with 13 reports (5%): orthopaedic reaming, cementing, various manipulations, pneumoperitoneum. Bradycardia was "sinus" in 79%, "nodal" in 11%, and "complete heart block" in 5%. Degeneration into asystole occurred in 19 cases (7%). Death occurred on the operating table in eight cases and postoperatively in 14 cases. ICU admission occurred in 19 cases (7%). In the 25 cases of "non-conventional" management, the inappropriate use of drugs or techniques during resuscitation (for example, calcium, isoprenaline, omission of indicated adrenalin, DC cardioversion for asystole) was most common. While the core algorithm managed 45 cases (17%) adequately, the specific bradycardia sub-algorithm was successful for all but two of the remainder.

 

In a similar manner to the airway, there is the potential for concentration on one component of the problem to the neglect of the wider problem when bradycardia occurs with either hypotension, hypertension, or cardiac arrest. Even when using an algorithm-based approach, the question may be raised "On which page do I start?" The AIMS reports were analysed in an attempt to identify presentation profiles from which high yield diagnostic and management pathways could lead. Several conclusions were drawn.

It is not possible to predict whether bradycardia is the primary or secondary event from the outset. This is a retrospective diagnosis made on the understanding of the pathophysiology after a diagnosis has been made. In some instances it is never possible to determine, for example, sepsis, bone cement and cardiopulmonary events.

The significance of any decrease in heart rate will be determined by the associated blood pressure rather than the absolute heart rate. When bradycardia occurs and the patient is pulseless, then go to the cardiac arrest algorithm because early aggressive management is required (table 4). If the rhythm is reflex induced sinus arrest, then the most effective treatment is to cease the precipitating event. If the patient is hypotensive it is worth noting the causes of hypotension and considering the use of vasopressors and aggressive fluid therapy. This is equally important in the context of spinal, epidural,¹¹ or regional blockade (especially interscalene block¹²). This can be achieved by reviewing the hypotension sub-algorithm. However, it should remain a problem of rate until the diagnosis has been made because of the important role of atropine and tertiary management options which include transvenous pacing. If the patient is hypertensive, then the problem should be managed according to the hypertension sub-algorithm.

Another issue which has the potential to complicate the problem is whether the prevailing cardiac rhythm should be diagnosed early. Sinus and non-sinus rhythms were compared with respect to ASA grading, haemodynamic status at the time of diagnosis, management. and outcome. This was done in an attempt to determine whether an early diagnosis of rhythm would be of value in the overall management of the problem. No differences were apparent. Analysis of cardiac rhythm should therefore not be pursued to the exclusion of supportive therapy or diagnosis of possible causes.

	ACKNOWLEDGEMENTS

 
The authors would like to thank all the anaesthetists in Australia and New Zealand who contributed to the 4000 incident reports upon which this and the other 24 papers in the Crisis Management Series are based. The coordinators of the project also thank Liz Brown for preparing the draft of the original Crisis Management Manual; Loretta Smyth for typing; Monika Bullock RN for earlier coding and classifying of data; Dr Charles Bradfield for the electronic version of the algorithms; Dr Klee Benveniste for literature research; Drs Klee Benveniste, Michal Kluger, John Williamson and Andrew Paix for editing and checking manuscripts. Dr Craig Morgan carried out detailed review of cases and was an author of the initial draft of this paper but declined authorship of the final draft. He is thanked for having done the original hard work and participating in the development of the manuscript.

	FOOTNOTES

 
This study was coordinated by the Australian Patient Safety Foundation, GPO Box 400, Adelaide, South Australia 5001, Australia.

	REFERENCES

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1. Runciman WB, Webb RK, Klepper ID, et al. Crisis management: validation of an algorithm by analysis of 2000 incident reports. Anaesth Intensive Care 1993;21:579–92.[Medline]
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6. Kloeck W, Cummins RO, Chamberlain D, et al. The Universal Advanced Life Support Algorithm. An Advisory Statement from the Advanced Life Support Working Group of the International Committee on Resuscitation. Circulation 1997;95:2180–2.[Free Full Text]
7. The Advanced Life Support Committee of the Australian Resuscitation Council. Adult advanced life support algorithm. July 2002. Available from the Australian Resuscitation Council at http://www.resus.org.au (accessed 12 September 2004).
8. O’Connell T . Update in paediatric cardiopulmonary resuscitation. In: Keneally J, ed. Australasian anaesthesia. Melbourne: ANZCA, 1994:27–37.
9. The Advanced Life Support Committee of the Australian Resuscitation Council. Paediatric advanced life support algorithm. March 2004. Available from the Australian Resuscitation Council at http://www.resus.org.au (accessed 12 September 2004).
10. Toprak V, Yentur A, Sakarya M. Anaesthetic management of severe bradycardia during general anaesthesia using temporary cardiac pacing. Br J Anaesth 2002;89:655–7.[Abstract/Free Full Text]
11. Lesser JB, Sanborn KV, Valskys R, et al. Severe bradycardia during spinal and epidural anesthesia recorded by an anesthesia information management system. Anesthesiology 2003;99:859–66.[CrossRef][Medline]
12. Sia S, Sarro F, Lepri A, et al. The effect of exogenous epinephrine on the incidence of hypotensive/bradycardic events during shoulder surgery in the sitting position during interscalene block. Anesth Analg 2003;97:583–8.[Abstract/Free Full Text]
13. Australian Patient Safety Foundation. Crisis Management Manual: COVER ABCD A SWIFT CHECK. Adelaide: Australian Patient Safety Foundation, 1996, 74 pp. Available at http://www.apsf.net.au/anaesthesia.htm (accessed 6 September 2004).

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