Tachycardia during the course of an anaesthetic is a common event. The clinical significance of tachycardia will in part be determined by the blood pressure and cardiac rhythm of the patient at the time. This may vary from a hypotensive to a hypertensive crisis. Tachycardia and hypertension have been shown to be independently associated with a poor outcome after prolonged procedures.¹ Hypotension may degenerate into a cardiac arrest or the patient may be pulseless from the outset.²

The scope of the problem is large when these situations are considered collectively. Problems are commonly resolved because the anaesthetist recognises patterns learnt from previous experiences. The potential exists, however, for the problem to lie outside the repertoire of the anaesthetist, particularly if they are inexperienced, the cause is rare, or the tachycardia is associated with an unusual phenomenon. Addressing the problem becomes increasingly difficult when there are simultaneous abnormalities in other systems. Attempting to initiate appropriate supportive therapy and consider a large differential diagnosis in a comprehensive manner may involve unacceptable delays in a crisis. It was therefore decided to examine the role of a structured approach to the problem of tachycardia associated with anaesthesia.

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.³ This was validated against the first 2000 incidents reported to the 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 the patient.⁴

It was concluded that, if this core algorithm had been correctly applied, a functional diagnosis would have been reached within 40–60 seconds in 99% of applicable incidents, and 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.³ However, 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.^3–5 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.⁶ This study reports on the place of the COVER ABCD–A SWIFT CHECK algorithm in the diagnosis and initial management of tachycardia, provides an outline of a specific crisis management sub-algorithm for tachycardia during anaesthesia, and provides an indication of the potential value of using this structured approach.

METHODS

Of the first 4000 incidents reported to AIMS, those which made reference to tachycardia or tachydysrhythmia were extracted and analysed with respect to the following criteria: surgical group, anaesthetic technique, patient’s ASA status, phase of anaesthesia at the time of presentation, presenting features (cardiac rhythm, blood pressure, oxygen saturation and other associated vital signs), the presumed precipitating cause, management, and outcome. The COVER ABCD–A SWIFT CHECK algorithm, described elsewhere in this series of articles,⁶ was applied to each 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 tachycardia is not adequately dealt with by this algorithm, a specific sub-algorithm for tachycardia was developed (fig 1) and its putative effectiveness was tested against the reports. How this was done is described elsewhere in this series of articles.⁶ The potential value of this structured approach—that is, the application of COVER ABCD–A SWIFT CHECK to the diagnosis and initial management of the problem followed by the application of the tachycardia 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. It was also of interest to evaluate if delays in diagnosis and overall outcome could be improved with the application of the sub-algorithm.

RESULTS

There were 123 reports which contained the word “tachycardia” or “tachydysrhythmia”. These occurred across a range of surgical groups (table 1).

The patients’ ASA grades were available in 117 cases (table 2).

Tachycardia was reported during all phases of anaesthesia but occurred most commonly at induction and in the maintenance period (table 3).

Aetiology and diagnosis

The contributing causes for all reported cases of tachycardia and for the subgroups are presented in table 4. A total of 145 causative events were identified within the 123 reports. In this series, drugs are the dominating associated cause of tachycardia. The haemodynamic status of the patient at the time that tachycardia was detected included cardiac arrest (17%), hypotension (33%), normotension (27%), and hypertension (26%).

Cardiac arrest was reported in 24 events (17%). The prevailing rhythm was sinus pulseless electrical activity (PEA), formerly known as electromechanical dissociation (four cases), pulseless ventricular tachycardia (VT; n = 9), and ventricular fibrillation (VF; n = 5). In one case a bizarre undiagnosable rhythm was present initially which degenerated into VT and VF and then asystole. One episode of VT could not be clearly distinguished from supraventricular tachycardia (SVT) on the monitor. In four cases VT degenerated into VF.

Most specified ASA grades were represented in the cardiac arrest group: ASA IV (n = 4), ASA III (n = 6), ASA II (n = 2), ASA I (n = 8), not stated (n = 4). Cardiac arrests occurring in ASA I patients were caused by anaphylaxis (n = 3, PEA), hypoxaemia (n = 1, VT-VF), and hypovolaemia (n = 1, VF). Two ASA I patients experienced sudden VT in association with intravenous induction agents and another during handling of the myocardium during thoracic surgery. None of these patients died.

There appears to be a higher incidence of allergy and cardiopulmonary events as causes among the reported cases of tachycardia (table 4). In 10 of the reports the patient was initially hypotensive and subsequently deteriorated to cardiac arrest. A pulseless state was reported from the outset to the remainder. No differences in aetiology were evident from an inspection of the reports. This supports the use of the cardiac arrest algorithm in every case of cardiac arrest, irrespective of how it presents.

Hypotension occurred in association with tachycardia in 48 cases (33%, table 4). Again there is a higher representation of allergy and cardiopulmonary events, but this is not the case for hypovolaemia as might be expected. The causes were also compared between sinus and non-sinus tachycardia. All cases of allergy were associated with sinus tachycardia. No other patterns were apparent; however, the number of cases was small. As a general observation, the profile of causes for hypotension and tachycardia occurring together is significantly different from either hypotension or tachycardia overall to warrant its own subgrouping.

Hypertension was reported in 37 cases (26%). The majority of cases involved sinus tachycardia. The remaining seven cases were associated with non-sinus tachydysrhythmias: VT (n = 1), SVT (n = 2), atrial fibrillation (n = 1), bigeminy (n = 2), and ventricular ectopy (n = 1). There was no apparent difference in causes with respect to rhythm.

There are notable differences in the causes in this group compared with hypotension. Light anaesthesia was the attributed cause in six cases. This included frank awareness and perceived pain. Two of these involved the inadvertent administration of muscle relaxant and one involved an empty vaporiser. Three cases were associated with hypercarbia secondary to rebreathing resulting from malfunction of the expiratory unidirectional valve or soda lime exhaustion. Drugs were implicated in 11 cases and again the profile of drugs differs considerably from hypotension (table 5). Four of these were associated with syringe or ampoule errors, three of which involved adrenaline.

Tachycardia occurred without a change in blood pressure in 39 cases (27%). The causes described in this category represented those already observed in hypotension and hypertension (tables 4 and 5).

An apparent abnormality of gas exchange as evidenced by desaturation on pulse oximetry, inadequate ventilation, obstruction, or dyspnoea was described in 30 reports (24%). Evaluation of these cases showed that desaturation may represent an artefact on pulse oximetry secondary to diminished peripheral perfusion,⁷ but this could not be distinguished at the time of detection of tachycardia from those cases in which real abnormalities of gas exchange existed.

Outcomes

The outcome of patients experiencing tachycardia during anaesthesia was studied. Poor outcomes are given in table 6. Thirty nine cases were considered to have had a poor outcome because they were not resolved by the completion of the normal recovery period. Three cases resulted in death on the table or in the postoperative period. This contrasts with previous reviews of death resulting from cardiac arrest under anaesthesia which described a 50% mortality rate.⁸ Factors contributing to a poor outcome were considered in terms of ASA rating, rhythm, cause and management.

A poor outcome was more likely to occur if tachycardia was associated with a pulseless state. All deaths occurred in this group. It appeared otherwise independent of blood pressure. Similarly, no strong relationship could be found with ASA rating (table 7). There were no cases in which it was felt that outcome could have been improved.

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; 40 cases (33%) from the database would have been diagnosed and, of these, 28 (70%) also resolved by application of the core algorithm COVER. The majority of these dealt with vaporiser incidents V2 (n = 1), circuit problems V1 (n = 7), possible artefacts from monitors R1 (n = 3), equipment malfunction or errors with non-anaesthetic drugs R2 (n = 25). The remaining cases required either completion of the sub-algorithm for tachycardia or pursuit of the sub-algorithms for the specific aetiological incidents dealt with under ABCD–A SWIFT CHECK. It was considered that carrying out the recommendations shown in fig 1 (the sub-algorithm) would have constituted appropriate management in all cases.

When the effectiveness of the structured approach represented by COVER ABCD–A SWIFT CHECK algorithm and the special sub-algorithm for tachycardia was compared with that of actual management as documented by each of the reports, it was considered that, if properly applied, the structured approach recommended would have led to quicker and or better resolution of the problem in four cases. There was a significant delay in diagnosis in three of these and inappropriate management in one.

DISCUSSION

The specific sub-algorithm for tachycardia is shown in fig 1. The hallmarks of the sub-algorithm are early clarification of the haemodynamic status and context specific treatment.

Tachycardia is frequently associated with abnormalities of blood pressure and separate sub-algorithms have been developed for these. Following multiple sub-algorithms may generate unnecessary workload and delays. The data were inspected for patterns which may provide guidance in this event and the following recommendations are made:

If the patient is:

• Pulseless: follow the sub-algorithm for cardiac arrest. A detailed discussion of the management of cardiac arrest is beyond the scope of this paper but can be found in other reviews^2,9 and guidelines.^10,11

• Hypertensive: follow the sub-algorithm for hypertension. The differential diagnosis evident in the AIMS reports closely resembles that for hypertension described in other series¹² and elsewhere in this set of articles.¹³ Management differs from other scenarios involving tachycardia in that immediate support of vital signs is not generally required, a diagnosis often being considered before any treatment is initiated.

• Hypotensive: the sub-algorithm for tachycardia should be followed until the cardiac rhythm is diagnosed. There will be some benefit in cross referencing to the hypotension sub-algorithm when hypotension co-exists with sinus tachycardia. Physiological models emphasise that sinus tachycardia is most likely to occur as a secondary response to hypotension. Immediate supportive and further definitive treatment will be similar to that described for hypotension. An exception to this is hypotension occurring as a result of tachycardia induced myocardial ischaemia. The sub-algorithm for hypotension incorporates this into its differential diagnosis.⁷ Management of hypotensive patients with non-sinus tachydysrhythmias is specified in the tachycardia sub-algorithm.

CONCLUSION

Tachycardia during anaesthesia is a common event which is frequently associated with a simultaneous change in status of other monitored vital signs. The differential diagnosis is large and addressing it in a comprehensive fashion must be preceded by supportive treatment. Tachycardia appears to be managed in an appropriate and timely manner in the majority of cases, but this is not without exception. Treatment pathways based on associated blood pressure and prevailing rhythm, in the case of hypotension, appear to offer a functional systematic guide which complements the already proven benefits obtained by employing the core algorithm COVER ABCD.