Case 35 The importance of interpretation
A 4-month-old Pakistani infant, Arif, presents to the ED with a 24-hour history of abnormal movements. One of the episodes is witnessed by the triage nurse who feels that Arif is having a tonic-clonic fit with loss of consciousness. That episode lasts for 4 minutes but there have been five other episodes in the past 24 hours, the longest being for 15 minutes. Arif is fully breast fed and has not been weaned yet. There is no other relevant medical history.
Arif has a temperature of 37.1°C, a flat fontanelle and no rash. The paediatric ST1 can elicit no abnormal signs. The blood glucose is normal at 5.1mmol/L. Following discussion with the registrar, who is primarily concerned about the possibility of meningitis, a FBC, CRP, U and E’s, bone chemistry, LFTs, blood cultures, urine culture and a LP are performed and iv ceftriaxone and aciclovir are administered.
The results are as follows:
| Normal | ||
| Hb | 9.2 g/dL | 9.0–13.0 g/dL |
| WBC | 17.2 × 109/L | 4.5–15.0 × 109/L |
| Neutrophils | 9.1 × 109/L | 1.5-8.0 × 109/L |
| Platelets | 362 × 109/L | 150–400 × 109/L |
| U and E’s | Normal | |
| Calcium | 1.52 mmol/L | 2.20–2.75 mmol/L |
| Phosphate | 2.62 mmol/L | 1.30–2.10 mmol/L |
| ALP | 878 U/L | 145–420 U/L |
| LFTs | Normal | |
| CRP | 1 mg/L | <6 mg/L |
| CSF | ||
| WBC | 4 × 106/L | <5 × 106/L |
| RBC | 2 × 106/L | 0–2 × 106/L |
| Gram stain | Negative | |
| Protein | 0.38 g/L | 0.20–0.40 g/L |
| Glucose | 3.6 mmol/L | 2.8–4.4 mmol/L |
| Urine dipstick | Negative |
Overnight Arif has 3 more fits and requires iv lorazepam on 2 occasions. He remains apyrexial.
What is your opinion of the investigation results and the treatment to date?
At the 8.30 am handover the consultant notes the low calcium that is documented in the handover sheet and asks the ST1 about the low calcium and how it could relate to the fitting. After a pause, the ST1 states that he did notice that it was low but that he didn’t think that it was low enough to cause a fit. The result had not been discussed with the registrar.
What do you think the likely diagnosis is and which further investigations would you do?
A diagnosis of rickets with hypocalcaemic fits is made. A blood sample is immediately obtained for vitamin D, parathyroid hormone levels, Mg and repeat bone chemistry and an urgent blood gas analysis (which also measures a number of electrolytes) is performed which shows the ionized calcium to be low. A ferritin level and a haemoglobinopathy screen are also performed and a wrist X-ray is also ordered.
What treatment would you administer?
IV calcium gluconate is administered. Oral calcium and vitamin D are also prescribed. The wrist X-ray provides further confirmation of the rickets. The calcium and phosphate levels normalize and Arif stops fitting. The ceftriaxone and aciclovir are stopped.
The ferritin level is also low and Arif is commenced on a 3-month course of iron.
He is discharged with a 3-month course of vitamin D and with dietary advice.
What else should be done?
The mother who is dark skinned, mostly covered in traditional dress and a vegetarian, is referred to her GP who diagnoses her as also having vitamin D deficient rickets. Arif is well and thriving on subsequent clinic follow-up.
The mother complains stating that he had unnecessary investigations, unnecessary drugs and multiple fits due to the delay in diagnosis.
Expert opinion
Hypocalcaemic fits in infancy secondary to rickets are rare, but this possibility should nevertheless have been on the differential diagnosis list in Arif. Whether Arif, who was afebrile and had no signs of meningitis such as a bulging fontanelle, should have had a LP and iv antimicrobials immediately, or whether he should have been observed pending the preliminary investigation results is debateable. It would be reasonable to do a LP and give antimicrobials on the grounds that meningitis and encephalitis can be difficult to diagnose in infants, they are a common cause of fits in infants and early treatment for these conditions is very important. Treatment can then be stopped if the patient’s condition and the investigation results suggest an alternative diagnosis.
Having received the above results, which should have been obtained urgently, the diagnosis should have been reviewed. One of the advantages of having a patient in hospital is that they can be observed carefully and repeatedly reviewed. The slightly raised blood WBC count is probably secondary to the fitting. The results exclude meningitis and it would be highly unusual to have encephalitis with a normal CSF result. The normal urine dipstick suggests that a urine infection is very unlikely and Arif does not have the features of the two other common serious infections, pneumonia and septicaemia. A significant infection is therefore unlikely.
Not only is it the responsibility of the doctor ordering the investigations to check the results (or to ask a colleague to do so) but they must also act on them. If there is uncertainty about a result then it should be discussed with a more senior doctor. The registrar’s supervision of the ST1 should also be investigated.
Many doctors would use their initiative and use search engines such as Google to look up hypocalcaemia in infants to discover more about this condition. Diagnosis and treatment should have been speedier but fortunately Arif does not seem to have sustained any long-term harm from his repeated fits.
Legal comment
According to the Expert Opinion, it was acceptable to do a LP, but Arif may have been spared the three fits and the iv lorazepam during the night, if an earlier diagnosis had been made. The paediatric ST1 failed to act on the low calcium results. This is unacceptable. The hospital should apologize unreservedly for the error that the ST1 made and should consider whether the ST1 needs further training in view of his mistake.
