Hypocalcaemia Investigation

Glasgow in the Sun

No more Part 1 revision - found out this week that I passed! Part 2 next sitting isn't until December so a chance to take to foot off the gas a bit for a couple of months before CMT starts up.

It's June, the sun is shining and summer is here. Lots of good things going on right now. Finalising my poster presentation at the moment for the British Association of Dermatologists' annual meeting in Liverpool and putting together an audit presentation for the West of Scotland Dermatology regional audit meeting later this month

Investigating Hypocalcaemia: This topic of discussion occurs in an educational article in this week's BMJ and covers an area which often causes me confusion as calcium metabolism is a complex process. It is not uncommon for a patient admitted acutely to hospital to be calcium depleted and a 'bone profile' investigation is a useful blood investigation to carry out on any unwell acute medical admission. Adjusted calcium levels (that is, serum albumin adjusted calcium concentrations) are the most informative. Common causes of hypocalcaemia include drug related causes, chronic kidney disease and post-operative hypoparathyroidism. In a patient with a low serum adjusted calcium level, a serum parathyroid hormone level is informative. Low serum calcium frequently occurs alongside low phosphate and magnesium levels and these should be checked. A cause of hypocalcaemia which seems to be coming increasingly frequent is due to inadequate sunlight exposure leading to lack of vitamin D. Vitamin D levels can be checked in patients believed to be at risk, although Vitamin D deficiency would not cause acute hypocalcaemia. 

Here is an example of how the serum phosphate and PTH levels can help in investigating the cause of hypocalcaemia:

Low phosphate + High PTH: ?Acute pancreatitis or drug induced eg. secondary to bisphosphonates

High phosphate + Low PTH: ?Hypomagnesaemia, hypoparathyroidism

High phosphate + High PTH: ?CKD or rhabdomyolysis

Patients with severe hypocalcaemia may become symptomatic with neuromuscular irritability and paraesthesia (think Chovstek & Trousseau's signs!). There may also be prolonging of the QT interval and therefore an ECG is indicated. Treatment may involve oral calcium supplementation if hypocalcaemia is mild, or IV calcium gluconate in the treatment of severe hypocalcaemia.

CT Radiation, Weekend Safety, COPD and Acute Leg Ischaemia

Anonymous clinical image
courtesy of (Aaron G. Filler MD PhD FRCS)

Dangers of CT Radiation

CT scans are now widely available and accessible. In my experience, a relatively large proportion of patients admitted under medicine / surgery in our hospitals undergo CT scanning as part of their investigation - eg. Head CT to diagnose a stroke, CT Pulmonary Angiogram to diagnose a PE, CT KUB to diagnose stones or CT Chest/Abdo/Pelvis to investigate weight loss and search for malignancy. The risk of radiation posed by CT scans have long been known about and a new study published in the New England Journal of Medicine this week offers compelling evidence linking risk of cancer with radiation exposure. The study followed up young patients who had been scanned and looked at subsequent risk of cancer. The RELATIVE increased risk of malignancy was in the region of 24%. It is important to note though that the ABSOLUTE risk of malignancy was only marginally increased. This is because the baseline rate of childhood cancers is very low to start with. There was roughly one excess cancer per 1800 CT head scans performed. Although the benefits of CT scanning at the time are often likely to far outweigh the later increased risk of cancer, this piece of research can serve as a reminder (particularly in young people) that scans should only be requested where there is a clear indication and where the results will affect clinical decision making or treatment.

Safety at the Weekend

A big story in the news this week came with the publication of a retrospective study in England which has shown that patients who undergo elective surgery on a Friday or at the weekend have a greater risk of complications and death. So why might this be? The patients operated on at the end of the week had a lower index of comorbidity but still had worse outcomes. One of the most dangerous times following an operation comes in the days immediately after the operation as opposed to the time of the operation itself. Early identification of complications is essential and perhaps due to reduced staffing levels at the weekends it is the management of the patient in the peri-operative period which is most likely to contribute to adverse outcomes.

Treating an Acute Exacerbation of COPD

According to research published in JAMA this week, five days of high dose prednisolone is enough to treat most acute exacerbations of COPD. In this head to head trial in Switzerland there wasn't a statistically significant difference in outcomes between patients treated with five or fourteen day courses. The study shows that a five day course works just as well as fourteen and limits patient exposure to systemic steroids which can cause side effects and toxic accumulation.

A Diagnosis not to be Missed: Acute Leg Ischaemia

There are many conditions which could present with acute leg pain however this is one not to be missed. It results from thrombotic, embolic or traumatic arterial occlusion of the vessels of the leg.

Presentation can be remembered by "The 6 Ps":Pain, Pallor, Perishing with cold, Pulselessness (always present), Paraesthesia and Paralysis. It may be missed because it can be mistaken a lumbar disc prolapse or a Bakers' cyst and risk factors for vascular disease may not always be present. Immediate referral to a vascular surgeon is necessary as urgent limb-saving surgery may be required.