The Boxmedicine Six
When you're the first to assess a new patient who has presented to hospital as an emergency, it is vital that you have a system in place. You need to make sure that you have considered all the tools at your disposal to help formulate a sensible differential diagnosis and safe initial management plan. At medical school, this was called taking a history, performing an examination, requesting investigations and so on. As part of this system, in this article we take you through the "Boxmedicine Six" - six simple tests that you need to consider for all patients that you clerk.
Here is a template of what the medical records might show for each patient you clerk, including the Boxmedicine Six:
Considering these non- or minimally-invasive tests and documenting the results should be an automatic process that comes after the history and examination. You may not need to perform them all, but if you at least think of the Boxmedicine Six, then you are unlikely to forget any single one of them. Let's now take a look at each one of these tests.
Capillary Blood Glucose (CBG)
Known to many as a 'BM', this is a bedside finger-prick test to give you a near-instant estimate of the patient's blood glucose. This is often forgotten yet there are plentiful reasons for it to be deranged. For example, a diabetic patient may have been unable to take his or her antihyperglycaemic medications (e.g. due to vomiting) and so the CBG may be dangerously elevated. Conversely, an insulin-dependent diabetic who has administered his or her insulin may present with a dangerously low CBG if they were unable to subsequently eat.
Checking the CBG may also remind you of significant differential diagnoses where presentation is often otherwise difficult to recognise. A classic example would be the patient with Diabetic Ketoacidosis (DKA), where the CBG may be dangerously elevated.
An ECG (or 'EKG') is an important tool, even when no cardiac problem is suspected. As a screening tool you may pick up signs of cardiac disease that could affect your patient's management. Or he or she may subsequently complain of chest pain later in his/her hospital stay (for a variety of reasons), and having a baseline 12-lead ECG can really help establish whether subsequent ECG abnormalities are new or old.
Other indications for requesting an ECG are clearly going to include chest pain. Also back pain and abdominal pain may warrant an ECG to look for signs of cardiac ischaemia that may be presenting somewhat atypically. Finally, any patient who has an irregular pulse or tachycardia should have an ECG to establish whether there is an arrhythmia.
This one's pretty simple:
FBC, U&E, CRP, LFT, bone profile (i.e. calcium), coagulation screen, group & saves or x-match.
You don't need to request them all, but you should have a reason if you haven't - most of these screening tests (excluding the blood compatibility tests) are pretty easy to justify. However, a person with a splinter doesn't necessarily need his liver function checked.
In the NHS, group & saves only really ought to be requested if you're patient risks further blood loss (e.g. small rectal bleed, or a patient who might be undergoing a procedure). A full cross-match would be indicated, for example, if you're actually planning to transfuse blood.
Plain radiographs (X-rays!)
Common presentations that warrant chest films are those with chest pain (multiple differentials, e.g. pneumothorax, rib fracture, etc) and abdominal pain (erect chest film - e.g. is there free subdiaphragmatic air?). Chest films are also indicated in those with a cough, and as part of a septic screen.
You may be asked to justify a plain abdominal radiograph in a patient with abdominal pain. Around 90% of renal stones are radio-opaque, and so may be visible on a plain film. So anybody with flank, iliac fossa or loin pain can be considered. Distension or a history suggestive of bowel obstruction or constipation would warrant an abdominal film - is there bowel dilatation or visible faecal loading? There are a host of other signs that can be found on an abdominal film in a patient with abdominal pain, but I won't list them. Just remember to consider this important tool.
Gases (arterial or venous blood gas)
Here are five good reasons why you might want to perform an arterial blood gas:
1) patient is hypoxic - here, you need an objective measure - the arterial PaO2. If the patient is hypoxic, then you need to know the type of respiratory failure by looking at the PaCO2 (see our tutorial on respiratory failure here);
2) patient is tachypnoeic - major causes of tachypnoea include pain (the gas might show a respiratory alkalosis), hypoxia/hypercapnia (look for respiratory failure), and a metabolic acidosis (hyperventilation in order to blow off CO2 and compensate for the low pH);
3) you suspect tissue ischaemia - the gas might reflect this by demonstrating a lactic acidosis;
4) you suspect a severe kidney injury - if so, you need to know if the patient is acidotic. A gas may also give you an instant approximation of the patient's potassium level;
5) the patient is unwell - this is deliberately vague. If you suspect something is not right, a gas will provide either reassurance or confirmation of your suspicion that your patient is very unwell and needs urgent help.
Arterial gases can be painful and there are some risks associated with it (e.g. arterial thrombosis/occlusion), and sometimes a venous gas will do just fine, but this depends on what you are looking for. For a thorough guide on interpreting ABGs, take a look at our tutorial here.
Urine dipstick (urinalysis)
Finally, this is a simple and non-invasive test that may give hints of diagnoses such as urinary tract infection (nitrites, leucocytes), urinary tract calculi (blood) and renal disorders (protein). However, take the result with a pinch of salt - too often are spurious diagnoses of UTI made just because there are leucocytes in the urine. Nitrites are a better indicator, but remember that sensitivity and specificity are imperfect when it comes to making the diagnosis of UTI based on any urine dipstick parameter.
Think outside the box when interpreting leucocytes and blood on a urine dipstick. Literally - outside the ureter. Any inflammation around the ureter may give a picture that you might otherwise attribute to a UTI. For example, appendicitis and diverticulitis.
The Boxmedicine Six may either help you make the diagnosis, or help you to pick up important physiological effects of the diagnosis. Once it is all on paper, you should look back through your notes and take a moment to assimilate it all. This final step is really important.
Do you have any tips on useful bedside tests or how you go about clerking new patients? If so, share them below!