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CYANOTIC SPELLS

Definition:

Cyanotic spell is also known as ‘tet’ spell or hypercyanotic spell. This is a sudden onset, occasionally progressive event seen in infants with Tetralogy of Fallots. It is associated with progressive cyanosis, hyperpnea (increased rate and depth of breathing) and disappearance of heart murmur. If not treated in time it may ultimately lead to altered sensorium, neurological complications and death.

PATHOPHYSIOLOGY

In a typical case of Tetralogy of Fallot the pressures in the right ventricle and left ventricle are equal. Hence the level of cyanosis and onset of cyanotic spell is determined the systemic vascular resistance and the level of pulmonary stenosis component. In case of mild pulmonary stenosis the right ventricular pressures are usually less than the left ventricle and hence the shunt is usually left to right. However, if the pulmonary stenosis is severe (due to any of the causes described later) then the right ventricular after load becomes high and hence the right ventricular pressures become high. If the systemic vascular resistance is low (which is usually the case in TOF with cyanotic spells) then the shunt flow becomes right to left. This results in progressive cyanosis. Low arterial pO2s lead to stimulation of the carotid receptors and the brain stem nuclei respectively which then leads to increased rate and depth of breathing which further increases the venous return to the right side of the heart and further right to left shunt of deoxygenated blood, thus leading to a vicious cycle. If not broken then it would ultimately lead to death.

Certain theories have also been postulated as possible explanation for the cause of cyanotic spells. These theories have basically compared the onset of cyanotic spells to exercise in normal individuals where there is fall in systemic arterial oxygen saturation during exercise and which reverses once exercise stops. In cyanotic spells this process of low systemic oxygen saturation continues and ultimately leads to progressive metabolic acidosis. These theories are:

a) Woods et al (2) - Postulated that hypoxemic spells are caused by spasm of the infundibulum of the right ventricle which precipitates a cycle of progressively increasing right to left shunting and metabolic acidosis.

b) Surge in Catecholamine release leads to increased myocardial contractility and infundibular stenosis. (Both these theories don’t

Explain the cause of cyanotic spells in patients with TOF with Pulmonary atresia).

c) Guntheroth et al (3) – episodes of paroxysmal hyperpnea are the cause rather than the effect of cyanotic spells. Hyperpnea increases the systemic venous return leading to right to left shunt as well as oxygen consumption through increase work of breathing.

d) Kothari et al (7) – argued against the commonly held views mentioned above and suggested the role of stimulation of mechanoreceptors in the right ventricle to be the cause of spells.

Increased contractility (due to catecholamine) and decreased right ventricular size (due to various factors) can trigger a reflex resulting in hyperventilation, some peripheral vasodilation without bradycardia, and this may initiate a spell. This mechanism he argued, explains most of the precipitating events and many other issues about cyanotic spells more satisfactorily.

CLINICAL MANIFESTATION

Typically cyanotic spells occur early in the morning (systemic vascular resistance lowest) or during naps in the day time. It occurs in infants between 6 weeks to 6 months of age. The possible triggers are anxiety, fever, anemia, sepsis or even spontaneously without any cause.

A typical infant with cyanotic spell would appear fussy, inconsolable and thereafter progresses to increasing cyanosis, hyperpnea that is typical of a spell.

CARDIAC CAUSES OTHER THAN TOF THAT MAY PRESENT WITH CYANOTIC SPELLS.

A) Tricuspid atresia with pulmonary stenosis.

B) Transposition of Great arteries with pulmonary stenosis

C) Single ventricle physiology with PS or pulmonary atresia.

Schematic representation of pathophysiology of cyanotic spell

? Spasm of RVOT

Anxiety

Crying

 

MANAGEMENT OF HYPOXEMIC SPELLS

BASIS OF MANAGEMENT

A) Knee chest position- To increase systemic vascular resistance

B) Oxygen- Oxygen to improve oxygenation. It is better given in nebulized form .

C) Morphine- Depresses respiratory center→ Decreases Systemic Venous Return. While giving this, facilities for ventilation should be available.

D) Inj Metoprolol- 0.1mg/kg over 5 min, repeat every 5 min to max 3 doses , then start infusion 1-5 mcg/kg/min. We use this medication in our set up as intravenous propranolol is not available. Once stable we move on to oral B-blocker preferably propranolol. The mode of action of metoprolol is similar to Propranolol. Another short acting B-blocker that can be used is Inj Esmolol(0.5mg/kg over 1 min then 50mcg/kg/min over 4 min.

E) Propanolol- 0.1-0.2 mg/kg intravenously over 5 min. Reduces dynamic RV outflow obstruction.

Slows HR (↓ R→ L Shunting). Slight ↑ in SVR. Blocks hyperpnea response.

F) Ketamine- 0.25- 1.0 mg/kg. IV or IM→ has dual benefit causes sedation and ↑ SVR

G) Phenylephrine Hydrochloride- 0.01 mg/kg IV (slowly) or 0.1 mg/kg SC or IM (↑ SVR – dose to be titrated to BP response).

H) Methoxamine- 0.10mg/kg IV over 5-10 min. Leads to ↑ SVR.

I) IV fluids- preferably initially as bolus of 10-20cc/kg which may be increased to 60cc/kg. Bolus fluid should be isotonic saline or colloid. Extra volume can be given in cyanotic spell as the physiology is not inductive to CCF and also because of a restrictive RV physiology.

J) Inj NaHCO3-(1-2 meq/kg intravenously slowly). To correct metabolic acidosis.(MUST BE GIVEN)

K) Transfuse PRBC’s- 5-10 ml / kg IV over 5 hrs.

L) Correct Tachyarrhythmia- Improve diastolic filling and cardiac output.

After a brief history the very first step in case the child is conscious is to put him/her in knee chest position against the mother’s shoulder. Oxygen at 5lt/min is given by a second attendant standing behind the mother. Once child is quiet, give morphine bolus subcutaneously (0.1mg/kg). This may be repeated 3-4 times( VENTILATION FACILITIES SHOULD BE AT HAND).

Thereafter an IV line is put in and immediate samples are sent for counts, hemogram, and culture if required. Thereafter IV fluid boluses in the form of normal saline is given in the dose of 10-20ml/kg. (Reasons for this has been mentioned before.) Inj Sodabicarb is then given slowly intravenously at a dose of 1-2 meq/kg. Blood pressure is noted and Inj Metoprolol is given under BP and ECG monitoring at a loading dose of 0.1mg/kg intravenously over 5 min thereafter the child is started on Metoprolol infusion.

Many authors recommend the availability of cardiac pacing facility when giving beta blockers. With metoprolol this has not been seen and as metoprolol is shorter acting than propranolol hence in case of significant bradycardia then mere stopping the infusion will reverse the effect in 30 min to 1 hr. In majority of cases children usually improve with these measures but in certain cases they would need additional measures in the form of correcting anemia, controlling tacchyarrhythmias and managing sepsis.

FLOW DIAGRAM SHOWING THE MANAGEMENT OF CYANOTIC SPELL

REFERENCES:

1) Neches W., Park S., and Ettedgui J., Tetralogy Of Fallot and Tetralogy of Fallot with Pulmonary Atresia In : Garson A., Bricker J., Fisher D., and Neish S.(Eds), The Science and Practice of Pediatric Cardiology, 2nd edition Vol.1, 1999, Williams and Wilkins.

2) Wood P. Attack of Deeper cyanosis and loss of consciousness (syncope) in Fallot’s Tetralogy. Br Heart Journal 1958;20:282

3) Guntheroth WG, Morgan BC, Mullins GL, Physiologic studies of Paroxysmal hyperpnea in cyanotic congenital heart disease. Circulation 1965;31: 70.

4) Park M. Pathophysiology of Cyanotic Congenital heart disease In: Park M Pediatric Cardiology for Practitioners 4th Edition 2002.Mosby.

5) Bernstein D. Cyanotic Congenital Heart Disease Lesions: Lesions associated with dereased Pulmonary blood flow: Chapter 423 In: Behrman,Kleigmen and Jenson (Eds), Nelson Textbook of Pediatrics 17th edition, 2004 Elsevier.

6) Spray T.,Wernowsky G., Tetralogy of Fallot: Right ventricular Outflow tract obstruction, Chapter 17 In. Chang A., Hanley F., Wernowsky G., Wessel D., (eds), Pediatric Cardiac Intensive Care, 1998, Williams and Wilkins.

7) Kothari S.S., Mechanism of cyanotic spells in tetralogy of Fallot--the missing link?, Intl. Journal of Cardiology,1992 Oct;37(1):1-5.