Whether to give oxygen

The question of whether to give oxygen is always interesting because the tendency with any blue baby of course would be to give oxygen. But to warn you that in some of our babies we are concerned about giving oxygen in that oxygen can decrease the pulmonary vascular resistance and in some of these babies we need the increased pulmonary vascular resistance to achieve increased systemic oxygen saturation. This is, for example in patients with hypoplastic left heart syndrome, where the systemic circulation is dependent upon the pulmonary circulation. We want to maintain a pulmonary resistance that will allow perfusion of the systemic circulation via the ductus from the pulmonary bed. So think about the oxygen before you administer to these babies with potential cyanotic congenital heart disease.

If our baby has tetralogy of Fallot, let’s think about what that means in terms of the pathology involved. The embryologic aberration is probably a single phenomenon and that’s of mal-distribution of the division of the conus so that the conal septum is deviated anteriorally, crowding out the pulmonary outflow tract, if you will, leaving a defect in the ventricle septum and also a disproportionately large overriding aorta. So as complicated as tetralogy may seem, it’s probably a single embryologic problem. The presentation of tetralogy of Fallot can be quite variable, often depending upon the age and of course the severity of the cyanosis. The presentation may be with a murmur with or without cyanosis. If the obstruction of the outflow tract is very mild then the patient may have little or no cyanosis and present only because of the presence of a murmur. On the other hand, some of the most severe tetralogy of Fallot may have little or no murmur but the severe cyanosis being the key to that potential diagnosis. A physical examination, depending upon the level or degree of obstruction to the right ventricular outflow tract, cyanosis or not. If there is cyanosis then there is likely … long standing cyanosis, then there will be clubbing of the digits. So we don’t usually see clubbing in very young infants and neonates but after a matter of some months we often can see clubbing of the digits in these babies. An increased right ventricular impulse in that this right ventricle is facing obstruction to the outflow tract, as well as systemic resistance via the overriding aorta allows heart sounds and harsh mid-systolic murmur. This is another picture showing clubbing. We rarely see clubbing to this extent anymore except to those of us who go to Peru or third-world-countries occasionally to see cardiac patients and this is still a very prominent finding. The proliferation of capillary beds is apparent too as we look at the conjunctiva and we see these very full capillary beds that look like conjunctivitis often.

The murmur can be quite variable. Typically a harsh, mid-systolic murmur of varying lengths that we hear at the mid left sternal border, transmitted usually along the left sternal border. In fact the duration and the loudness – the intensity – of the murmur can be a clue as to how severe the obstruction to the outflow tract is. If the murmur is long, loud and harsh then usually that’s less severe obstruction to the outflow tract. In other words, the right ventricle is managing to get flow through this obstructive outflow through most of systole. If the murmur, on the other hand, is very short and relatively soft then it usually represents a more severe form of tetralogy of Fallot. In other words, the right ventricle is not affecting a significant outflow through the obstruction. And in fact the patient is usually bluer because of their right to left shunting into the overriding aorta, in the severe forms of obstruction. This becomes important in the follow-up of these patients. For example, when you are seeing patients as primary care physicians and happen to determine whether the tetralogy is becoming more severe.

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