This case report describes a patient who suffered an electrical accident, but whose good general condition upon initial assessment, along with the course of events in the accident and the presumed current exposure, could easily have resulted in him receiving insufficient testing and observation. Further testing revealed that there were indications for intervening to prevent renal damage as a result of muscle injury. Since test results prior to the accident were normal, and there was a seemingly obvious causal trigger, no further differential diagnoses were considered.
The patient did not describe either muscle spasms that could have kept him in contact with the circuit, or strong muscle contractions, and he did not fall from the stepladder on which he had been working. Such brief exposure to low-voltage current as seems to be the case here, is generally considered relatively unlikely to cause injury as a result of tissue heating. In Norway, electricians often colloquially refer to such exposures as 'candies'.
When assessing electrical accidents, it is important to describe the current flow in such a way as to allow exposure to subsequently be estimated. Keywords are current type, voltage level, probable route of the current through the body, and perceived or observed duration of the event. Any findings from examinations in the acute phase that could add to the patient's description of the exposure, such as spasms in the arms or legs, the surface and moisture level of the contact points (which affect the resistance), and skin alterations, should also be included (2).
The most common type of electrical accident involves exposure to low-voltage alternating current – 230 V or 400 V – with a frequency of 50 Hz. However, direct current is also used, especially in the workplace. Direct current and alternating current have somewhat different effects on the human body. The most important difference is that the 50 Hz frequency of alternating current can contribute to tetanic muscle contractions that may prevent a person who is holding onto a conductor from being able to let go. This will increase the duration of current exposure and thus the risk of tissue damage, including muscle injury. Tissues in the path of the current that have high resistance, such as bones and tendons, are particularly likely to undergo heating. This means that areas around joint and muscle attachments are vulnerable to injury (13). Exposure to direct current normally does not cause significant muscle spasms and is therefore typically of shorter duration than exposure to alternating current. In the case of lightning strikes or other high-voltage accidents, the type and duration of the exposure are of less significance given that large amounts of energy are transmitted regardless.
When assessing potential muscle damage, further tests should be conducted in the event of abnormally high total serum CK. CK is found primarily in skeletal muscle and myocardium, but also in the brain, intestines, kidney, thyroid and prostate. The creatine kinase enzyme consists of polypeptide chains that can be of two types: B and M. Total CK is a measure of three isoenzymes: CK-BB (brain type), CK-MB (cardiac muscle type – a marker for myocardial infarction) and CK-MM (skeletal muscle type). Of these isoenzymes, only CK-MB is measured routinely. The normal range for total serum CK in men aged 18–49 years is around 50–400 U/l, varying slightly between laboratories. A person's baseline level correlates with muscle mass, and muscle use can lead to significant increases in total serum CK, with even moderate muscle use increasing activity by 50 % (14).
Throughout the patient's hospitalisation, we observed highly elevated total serum CK levels. These may occur as a result of widespread damage to muscle tissue/rhabdomyolysis or severe myocardial infarction, for example. Measurement of total serum CK is therefore indicated as part of the workup and monitoring of muscle injuries, and when assessing the indication for treatment in cases of rhabdomyolysis (8, 12). The total CK serum concentration reflects to a large extent the amount of muscle tissue affected, and 10 000 U/l is sometimes used as a threshold for initiating forced diuresis (15, 16). In critically ill patients with widespread damage to muscle tissue, measurement of plasma myoglobin has greater sensitivity and specificity than measurement of serum CK for assessing the risk of acute renal failure (17). Plasma myoglobin was not quantified in this patient.
Knowing precisely when the exposure occurred makes it easier to interpret the total serum CK level. This is because total serum CK will be in the normal range shortly after muscle damage, before starting to increase after 2–12 hours (18). After about 24 hours, serum CK reaches its peak (8, 19), where it remains stable for up to 3 days (8) before gradually decreasing and returning to normal after 2–3 (19) or 4–5 days (8). However, extensive variation is seen, depending on the degree of hydration and on renal function. The relative timing of the injury and of sampling is therefore important as samples taken too soon after the injury will still be in the normal range, while levels may already have started to decrease after about two days. Our patient had an increase in total serum CK after 2 hours 45 minutes. Given the known variation, it may be worth taking multiple samples over the course of the first 12 hours post-injury to help ensure that any increase is detected, so that treatment can be initiated if required.
Documenting an increase in total serum CK could also prove important should the patient subsequently experience medical problems related to the arms, and there is reason to assess whether this is an occupational injury occurring in the wake of the previous accident.
In this case, the patient's previous medical history contributed to further testing, which in turn led to admission and treatment. The initial blood test was therefore crucial in ensuring that the patient received the treatment he needed to achieve the best possible outcome after the accident.
Upon suspicion of acute myocardial injury, especially when current is likely to have travelled through the chest region or where there is chest pain following the accident, troponin T (or I) should be measured, possibly in addition to CK-MB. In this patient, the troponin level was within the reference range of < 14 ng/l (99th percentile) when measured four hours after the accident (< 10 ng/l). The results thus suggest that striated muscle was affected to a greater degree by the accident (given the elevated total serum CK) than cardiac muscle. This is further supported by the fact that the ECG did not provide evidence of arrhythmias. Thus, according to test results, the accident probably did not lead to an increased risk of cardiac complications.
The blood tests following the accident strongly suggest muscle damage, although this was not expected on the basis of the clinical findings. The exposure to current may thus have been more serious in reality than the initial description suggested. However, it may also be that the threshold for muscle damage is lower than assumed, with the result that such damage is often overlooked and undertreated. The initial finding of normal serum potassium and high total serum CK is surprising, and difficult to explain. Normally levels of these two substances track one another after cell damage (20). Rhabdomyolysis is a known complication of high-voltage accidents (8, 21), but we are not aware of it having been described following exposure to low-voltage current.
Recommendations have been published for inpatient examination of those with electrical injuries (3). We recommend that hospital emergency departments review these when developing internal procedures.