Medical Management of Hyper-cyanotic spells in Tetralogy of Fallots

Introduction

Hypercyanotic spells can occur in patients with uncorrected Tetralogy of Fallot and other abnormalities where there is dynamic right ventricular outflow tract obstruction and a ventricular septal defect. Such spells are often mild but are potentially very dangerous and patients can deteriorate rapidly. The cascade of therapeutic action is dependent upon the response to treatment. 
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Tetralogy of fallot (TOF) is a congenital heart defect. TOF is characterized by four morphological changes; ventricular septal Defect, stenosis of the right ventricular outflow tract (RVOT), stenosis of the pulmonary valve, an ante- and dextro-positioned overriding aortic root and a secondary right ventricular hypertrophy (Knuf et al 2010).

Scope

This guideline applies to all infants with uncorrected Tetralogy of Fallot and other abnormalities where there is a dynamic right ventricular outflow tract obstruction infants in the Oxford Southampton network.

Purpose

The purpose of this guideline is to provide a standardised approach a standardised approach to the management of hypercyanotic spelling in neonates/infants with uncorrected Tetralogy of Fallot and other abnormalities where there is dynamic right ventricular outflow tract obstruction.

Definitions

The cascade of therapeutic action is dependent upon the response to treatment. 
  • MILD: the baby may appear pale, grey blue and may be clammy, with tachypnoea. Oxygen saturations will be lower than usual. 
  • SEVERE: On examination the right ventricular outflow tract murmur may be absent or short in duration. Loss of consciousness or ‘dropping off to sleep’ may be seen due to poor systemic perfusion.

Related Policies - Resuscitation Council UK

Presentation
  • The baby may appear pale, grey blue and may be ‘clammy’ 
  • Tachypnoea (rapid shallow breathing) 
  • Peripheral oxygen saturations will be significantly lower than the baby’s usual measurement. 
  • On examination the RVOT murmur may be absent or short in duration. 
  • Loss of consciousness or ‘dropping off to sleep’ can be seen if there is poor systemic perfusion.

Potential triggers or predisposing factors: 
  • Can be triggered by a variety of stimuli (distress, crying, dehydration, defecation or straining, fever, tachypnoea, anaesthetic agents, cardiac catheterisation) but may also occur without any reason.

Mild Hypercyanotic Spell - Always assess infant using ABDCE principles
Call for help. In mild cases position on parent’s/carer’s shoulder with the knees tucked up underneath. 
(This calms the infant, increases systemic venous return and increases systemic vascular resistance)
Reassess using ABCDE principles. Call for help. Administer 100% oxygen via non re-breath bag valve mask if necessary. Monitor oxygen saturations and ECG
If no Response to above - Call for help
If stable, give oral morphine 0.1mg/Kg
Site IV cannula – check venous blood gas
Give IV 0.9% sodium chloride 20mls/Kg in aliquots of 10mls/Kg
Give IV morphine 0.1mg/Kg as a bolus (can be repeated)
Use IM or subcutaneous route if IV access not readily available
Monitor neurological and respiratory status as morphine has respiratory depressant effects
If no Response to above; Contact SORT Southampton Oxford retrieval team 02380775502

Cardiology team Contact 02380 777222 Bleep 2811 Paediatric cardiology registrar for advice
Give IV Propranolol 0.1mg/Kg as a slow bolus monitoring for bradycardia, and/or IV Phenylephrine 0.02mg/Kg IV
Deterioration
  • Consider further SVR manipulation with SORT.
  • Intubation ventilation anaesthesia

Implementation

This guideline will be made available regionally on the PIER Website.  Local leads for critically ill children will disseminate guideline and raise awareness locally.

Process for Monitoring Effectiveness

The Wessex Paediatric Critical Care Network will review problems associated with a failure to comply with this guideline through its regional governance process.

References

Document Version: 
2.0

Lead Author: 
Katy Stimson, ACP, UHS

Additional Authors:
Dr T Richens, Consultant Cardiologist, UHS
​Dr M Griksatis, Consultant Paediatric Intensivist, UHS
Approving Network:
Wessex Paediatric Critical Care Network

Date of Approval: 
January 2025
Review Due:
January 2028