Croup: a cough to build a dream on
Few infections strike toddlers (2-4 year olds) quite like croup. It’s usually past midnight on a misty December night, temperatures outside a few degrees above average and it suddenly begins. A startling cough, rich as a quail calling from the underbrush in East Africa “Xiiq” and Middle East “cough adeekee” the cock’s cough a reference to its early morning timing as much as to its sound. In Europe and America “barking cough” compares the sound to the husky woof of a seal. Over 75% of cases are caused by the parainfluenza one of the few viral species that can survive in the human voicebox, something they achieve with blistering efficiency – within 30 minutes the vocal cords are swollen and millions of viral partials can be detected in the patient’s airborne sputum. In regions where children do not receive vaccinations or when parents refuse to offer this to their children – diphtheria with its bull neck, myocarditis and genital inflammation needs to be considered. The flu vaccine has also made croup less common in walk-in clinics over the last 5 years.
Croup is usually self limiting and can be eased by Tylenol, humidified air and a night in bed next to mom. But in reality, croup responds so well, in under 20 minutes, to a single dose of oral prednisolone or dexamethasone that I rarely forgo the opportunity to treat it. The rapid response is also useful to help exclude another dangerous possibility: the foreign body lodged in the airway, which is not a reference to illegal immigration, but may cause a croupy cough even days after inhalation.
How to recognize respiratory distress
Decades of paediatric emergency research has discovered two easy tests. First, the breathing rate. In most toddlers the resting respiratory rate (RR) is between 25-35 respirations per minute (rpm), if you have a toddler handy you can even measure it now, use a stopwatch and count how many breaths he takes in 1 minute. You can do it by watching the abdomen while listening for the breaths. Mind you, remember it has to be the resting rate so your toddler should be sitting calmly, which in my experience is almost never, at least until they get unwell that is. When they become unwell, the increasing metabolic demand calls for faster respiration which takes the RR to the 35-45rpm or even up to 50 respirations per minute. Anything above 55rpm is a warning sign and should prompt a direct visit to the emergency room, by ambulance if necessary. The important thing is not to measure this while the child is crying, laughing or chasing the cat.
The second useful rule is the CRT or capillary refill time. Press firmly on the back of your hand – if you have light coloured skin you should see a pale fingerprint left behind which slowly fades away. The time it takes for the fingerprint to disappear is the CRT. Pressing gently but firmly on the breast-bone of your healthy toddler leaves a fingerprint with a CRT of almost exactly 2 seconds at room temperature. This correlates with blood pressure, body temperature and levels of hydration. As a rule, if the CRT is 3 seconds you know there is a problem that needs a doctor, if the CRT reaches 4-5 seconds you have an emergency which, unless your child has just come in from making snow angels in his pyjamas, may require an ambulance.
This chart displays the age-adjusted paediatric respiratory rate, pulse, BP and other useful values
The ambulance or the car?
The ambulance is a rare necessity for any sick child, but fortunately in Canada most of us have access to high quality emergency care for our children, at minimum cost. In the case of airway obstruction due to croup, oxygen and dexamethasone will help, but what is quite peculiar, is the effect of placing the child in his mother’s arms. In a matter of seconds the obstructing vocal cords relax and the airway opens up. For this reason, in all but the exceptional case where intubation and ventilation is needed, the child with croup should remain in the mothers arms at every stage of treatment. It is also for this reason that I often advise parents driving children with croup to sit the child on his mother’s lap in the back and not to use the child’s carseat and for the mother only to wear the seat belt and not strap the kid under it. This is far from ideal, yet I not yet found any better technique. I think the chances of needing an ambulance for a croup cough may be, based on our clinic is about 1 in 30, yet don’t rely on stats, if the RR reaches a consistent 60rpm on repeat readings over 5 minutes, I would dial 911.
