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• Adenosine dosing in Supraventricular Tachycardia - ? Time for change
  Anjum Gandhi
  Published on: 9 January 2022
• Pitfalls in the use of Adenosine
  Eric Rosenthal
  Published on: 9 January 2022
• BNF for Children is also incorrect about adenosine dosage
  Sam Richmond
  Published on: 9 January 2022

• Published on: 9 January 2022

  Adenosine dosing in Supraventricular Tachycardia - ? Time for change

  • Anjum Gandhi, SpR Paediatric Cardiology
  • Other Contributors:
    • Orhan Uzun

  Dear Editor

  We read with great interest the article by Dixon, Foster, Wyllie and Wren, on the dosing of adenosine in supraventricular tachycardia (SVT). We have recently reviewed cases of SVT presenting to the Children’s Heart unit of Wales with a special focus on the effective dose of Adenosine and have made disturbingly similar observations. Our findings were recently presented in a research society meeting....

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  Dear Editor

  We read with great interest the article by Dixon, Foster, Wyllie and Wren, on the dosing of adenosine in supraventricular tachycardia (SVT). We have recently reviewed cases of SVT presenting to the Children’s Heart unit of Wales with a special focus on the effective dose of Adenosine and have made disturbingly similar observations. Our findings were recently presented in a research society meeting.

  Over a period of 10 years a total of 137 infants and children presented to our unit with a diagnosis of SVT. Of these Adenosine was used in 37 cases on 70 occasions. Through out South Wales the Advanced Paediatric Life Support (APLS) guidelines for adenosine are followed which suggest incremental doses of 50 micrograms/Kg, 100 micrograms/Kg and 250 micrograms/Kg for the acute management of SVT.

  The recommended starting dose of 50 micrograms/Kg was effective only on 4 occasions, that is in less than 6% of the cases. The second dose was effective on another 33 (47%) occasions, while the third dose of 250 micrograms successfully terminated the arrhythmia in another 24 (34%) cases. Adenosine was ineffective on 9 (13%) occasions. Other agents were required in these cases. The mean effective dose of Adenosine thus works out to be 156 micrograms/Kg.

  Our findings support Dixon et al’s conclusions that the current recommended Adenosine doses for acute management of SVT are ineffective in the vast majority of cases. This highlights the urgent need for review of the dose protocol of Adenosine in SVT.

  Reference

  1. J Dixon, K Foster, J Wyllie, and C Wren Guidelines and adenosine dosing in supraventricular tachycardia Arch Dis Child 2005; 90: 1190-1191

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  Conflict of Interest:
  None declared.

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• Published on: 9 January 2022

  Pitfalls in the use of Adenosine

  • Eric Rosenthal, Consultant Paediatric Cardiologist

  Dear Editor,

  The report by Dixon et al. on the dosing of adenosine is important.[1] That the use of higher starting doses (100 - 200ug/kg) should significantly increase the chance of adenosine terminating the supraventricular tachycardia or demonstrating its mechanism on the first dose was clearly demonstrated in their retrospective review.

  It is worth repeating that the maximum dose for children of 500ug...

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  Dear Editor,

  The report by Dixon et al. on the dosing of adenosine is important.[1] That the use of higher starting doses (100 - 200ug/kg) should significantly increase the chance of adenosine terminating the supraventricular tachycardia or demonstrating its mechanism on the first dose was clearly demonstrated in their retrospective review.

  It is worth repeating that the maximum dose for children of 500ug/kg and neonates of 300ug/kg is for a singly administered dose. An issue that we see far too frequently is the summing of each dose of adenosine to arrive at a cumulative dose that "precludes further administration". When starting at 50ug/kg and incrementing in 50ug/kg per dose a common sequence is 50, 100, 150 and 200ug/kg at which point there will be some who add these doses and conclude they have given 500ug/kg i.e. the upper dose limit. The refrain is then that "adenosine did not work". From Dixon et al's study it is not surprising.

  Another issue is when adenosine does not terminate the tachycardia in appropriate doses but the ECG has not been recorded during its administration. In some patients, the tachycardia may only stop for a beat and then re-initiate but this is not always clear on a monitor screen. Knowledge that adenosine has worked - even if only for one beat - suggests that a supraventricular re-entry tachycardia using the AV node is present. In addition, blocking the AV node with drugs such as digoxin or betablockers is likely to be effective due to their longer duration of action. A brief slowing of the ventricular rate during atrial flutter or atrial tachycardia clarifies the tachycardia mechanism – but again this is best seen on the rhythm strip performed during adenosine administration. The transient slowing and accelerating of the rate in sinus tachycardia is also best appreciated on a printed rhythm strip.

  Very rarely, the child has a ventricular tachycardia and adenosine does not terminate the tachycardia but does alter the relationship of the P-waves to the QRS complexes. This too cannot be appreciated on a monitor screen. An example of the subtle changes is shown in Fig. 1. While these changes would not be expected to be recognised by every general paediatrician, the strip can always be reviewed at a cardiac centre - but only if it has been recorded! In the example shown, the 8-year-old child had a DC cardioversion after adenosine in appropriate doses did not terminate the tachycardia. The diagnosis however, was altered from supraventricular tachycardia with aberration to ventricular tachycardia after review of the rhythm strip and the child then had a successsful radiofrequency ablation for a left ventricular tachycardia.

  Figure 1. After the starred beat in this relatively narrow QRS tachycardia it is apparent that the regular deflection in the ST segment (circled in beats 4 – 6 for clarity) disappears. It then becomes clear that this deflection represents atrial activity (retrograde atrial activation from ventricle to atrium). It also becomes clear that after the starred beat, there is independent atrial activity (some of the P-waves are highlighted by arrows). That the tachycardia continues independently of atrial activity, confirms that it is a ventricular tachycardia.

  References

  1. Dixon J, Foster K, Wyllie J, Wren C. Guidelines and adenosine dosing in supraventricular tachycardia. Arch Dis Child 2005; 90: 1190-1191.

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  Conflict of Interest:
  None declared.

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• Published on: 9 January 2022

  BNF for Children is also incorrect about adenosine dosage

  • Sam Richmond, Consultant Neonatologist

  Dear Editor,

  I am sorry to say that the BNF for Children (http://www.bnfc.org), published in October 2005, is also incorrect in its recommendation of starting dosage for use of adenosine in newborns and infants. The BNFC incorrectly recommends starting at 50-100 micrograms/kg and increasing the dose by 50 microgram/kg until a maximum of 300 microgram/kg.

  However...

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  Dear Editor,

  I am sorry to say that the BNF for Children (http://www.bnfc.org), published in October 2005, is also incorrect in its recommendation of starting dosage for use of adenosine in newborns and infants. The BNFC incorrectly recommends starting at 50-100 micrograms/kg and increasing the dose by 50 microgram/kg until a maximum of 300 microgram/kg.

  However, I am pleased to report that the Neonatal Formulary (4th edition published 2003 - http://www.neonatalformulary.com) correctly recommends starting with a dose of 150 microgram/kg and suggests that a larger dose of 300 microgram/kg is sometimes needed.

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  Conflict of Interest:
  None declared.

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