The reality is that these reasons for doing tests are all dubious and can achieve the opposite to the desired result. There are few paediatric medical problems for which a test is more valid than clinical assessment. For example, upper respiratory tract infections - If the symptoms are all well controlled by simple analgesia, what useful information could tests add?
Worse still, many tests are potentially misleading or might cause anxiety. I like a full blood count as much as the next medic but goodness me don't they have a lot of information in them? Does it mean something when the lymphocyte count is just below the reference range if the total white cell count is normal? Sometimes the result can be alarming. "Toxic lymphocytes" are a good example of something that you don't want to get on the lab report, especially when the child is climbing up the shelves in your consulting room while you try to work out how to answer the question, "Was the blood test result normal?"
But it's not all me, me, me. The truly difficult part of all of this is that we should not use tests to reassure. No matter how much another person wants a child to have a test for their own reassurance, we should only be doing tests which are in the best interest of the child. Although a tough rule to live by, it is important to remember that the child is the patient, not the parent.
The good news is that tests rarely tell you something of great value once a child has been clinically assessed. Tests are most useful when they give you a number which has a clear clinical significance and where you could not have made a diagnosis without that test. This criteria applies very nicely to testing blood sugar for an acutely unwell child, in certain curcumstances.
Here are two cases where a simple skin prick glucose test has made all the difference:
Case 1
A three year old boy has been vomiting and febrile for 24 hours. Clinically they are not dehydrated (they have wet mucous membranes, normal skin turgor, their eyes are not sunken and they are passing urine reasonably well) and they are neither septic nor meningitic. In fact what is odd about them is that they seem subdued and grumpy despite having a normal heart rate and normal temperature.
Blood sugar is tested and found to be significantly low.
Why do unwell children get low blood sugar? This happens for one of two reasons. The most common reason is that the child has exhausted their available supplies of glucose. The child's body has a limited reserve and if consumption exceeds supply then the child will eventually run out of glycogen, the most readily available way of mobilising energy in times of need.
The second possible reason is that the child has a metabolic problem. Some children have a disorder in their metabolism which is normally masked by the almost constant supply of carbohydrate that they receive. When this supply is interrupted, it unmasks the fact that one of the chemical pathways (needed in times of crisis) is faulty. No plan B, no blood sugar.
How do children with low blood sugar look? The brain is a complicated thing but it runs on two main things: oxygen and sugar (or backup substances but let's keep this simple). If a child has a low blood glucose then the first signs are usually neurological. Most commonly the child is not fully alert and is often unhappy. I believe the term is hangry. They will be less active but they may also be combative.
How should low blood sugar be treated? The first thing to mention here is a pitfall. Do not use glucagon to treat hypoglycaemia in children when the reason for their low blood sugar is that they have run out of reserves. It simply won't work.
If the child is able to swallow safely, they can be given a sugary drink. If not then what happens next depends on where you work. If you are outside of a hospital setting, then a glucose gel rubbed into the oral mucosa will be a good plan. In hospital, most places will give an intravenous bolus of dextrose 10%. (ALSG recommends 2ml/kg) When the cannula goes in, there are usually some blood tests that need to be taken, depending on local guidelines.
The response to initial treatment should be assessed and further intervention given as needed. If there is a good response, it is important to realise that this is not 'job done'. To become hypoglycaemic, the child had to have exhausted their reserves, so a single bolus will have a very temporary effect. It is essential to continue the carbohydrate supply, often in the form of maintenance intravenous fluids.
Case 2
How should low blood sugar be treated? The first thing to mention here is a pitfall. Do not use glucagon to treat hypoglycaemia in children when the reason for their low blood sugar is that they have run out of reserves. It simply won't work.
If the child is able to swallow safely, they can be given a sugary drink. If not then what happens next depends on where you work. If you are outside of a hospital setting, then a glucose gel rubbed into the oral mucosa will be a good plan. In hospital, most places will give an intravenous bolus of dextrose 10%. (ALSG recommends 2ml/kg) When the cannula goes in, there are usually some blood tests that need to be taken, depending on local guidelines.
The response to initial treatment should be assessed and further intervention given as needed. If there is a good response, it is important to realise that this is not 'job done'. To become hypoglycaemic, the child had to have exhausted their reserves, so a single bolus will have a very temporary effect. It is essential to continue the carbohydrate supply, often in the form of maintenance intravenous fluids.
Case 2
A 5 year old girl presents with abdominal pain and vomiting. They started being non-specifically unwell two days ago. Yesterday they started having abdominal pains and overnight they started to vomit. The child is drinking well and passing urine.
The child has no significant past medical history. On examination the child is subdued and miserable. The abdomen is soft. The child is tachycardic but has a normal temperature.
When a blood glucose is checked, it reads three times the upper limit of normal.
Why do children get high blood sugar? Although any significant illness can cause a moderately raised blood sugar level, hyperglycaemia of this magnitude always means diabetic ketoacidosis. (Well, that's not strictly true. Occasionally it means that there is sugary residue from a drink or snack on the finger that was tested. That's why you need to clean the finger first.) Of course, it is possible (and preferable) to make the new diagnosis of type 1 diabetes before it gets as far as DKA. If the blood sugar is high, type 1 diabetes should be the presumed diagnosis.
How does diabetic ketoacidosis (DKA) present? DKA is a difficult diagnosis for all sorts of reasons:
- Symptoms are somewhat non-specific. Abdominal pain and vomiting are good examples.
- DKA is rare and gastroenteritis is common
- Clinicians tend to check that a child is drinking and passing urine enough, but may not ask if oral intake and urine output is excessive
- The onset of symptoms can be surprisingly gradual.
- While less common, type 1 diabetes can occur at very young ages. Unsurprisingly, it is not the first diagnosis that people think of when seeing an unwell young child.
Most commonly, the illness is initially mistaken for a viral URTI or gastroenteritis. Polyuria and polydipsia are unusual symptoms in a child with a viral illness who is significantly unwell and should be major clues. Abnormal breathing is a feature of the acidosis and should also prompt the clinician to think of DKA. However there is one feature that rather tidily applies to both high and low blood sugar: the child will be subdued and lethargic.
How should DKA or newly diagnosed type 1 diabetes be treated?
This is fairly specialised stuff so these children will all need to be referred. The acute management of DKA is rather complicated and requires careful fluid management to reduce the risk of developing cerebral oedema. According to the NICE guidelines (1), fluids should be the priority for the first 1-2 hrs after which insulin can be started for DKA.
As tests go, blood glucose is much more useful that many, and the result and meaning are usually clear. Blood glucose is a test to go for in children who have atypical symptoms or are significantly subdued. High or low, an abnormal result is a game changer and early recognition of the problem will make a huge difference.
Edward Snelson
Tricorder trainer
@sailordoctor
Disclaimer: While it would be wrong to do an unnecessary test on a child, it is perfectly acceptable to Feng Shui them. They then need careful monitoring to see the effect of the intervention.
Reference
