Assessment Of Creatine Phosphokinase (CPK) Changes In Patients With High-Voltage Burns

Summary

The aim was to evaluate change in creatine phosphokinase (CK) enzyme in high-voltage burn patients. A retrospective study was conducted of 104 patients (aged from 16 to 83 years old) who suffered from burns due to high voltage and were treated as inpatients at the National Burns Hospital. Patients were divided into two groups: patients with limb amputations in group A and patients without limb amputations in group B. Analysis was conducted on medical records of testing for plasma CK level immediately upon admission and during treatment. Testing of CK plasma enzyme was performed on an AU480 machine manufactured by Beckman Coulter. Data were processed using SPSS 20.0 software. Average plasma CK index increased on the first day of admission. In group B, plasma CK enzyme index increased from 5.5 to 22.4 times, and in group A this index increased from 5.6 to 46.5 times compared with the plasma CK index of normal people (170 U/l). The mean plasma CK enzyme index in the amputation group (n=20) was higher than in the non-amputation group (n=84). In patients with limb amputations, CK levels significantly decreased after deep necrosis incision and after amputation (p=0.00001). In patients with burns due to high voltage, plasma CK levels rise in the first days after burns. Increased plasma CK enzyme levels are directly proportional to total burn surface area (TBSA) and burn depth. After escharotomy and amputation, plasma CK levels decreased significantly compared to preoperation levels.

Introduction

Creatine phosphokinase (CK or CPK) is an enzyme that catalyzes the chain of reactions between ATP and creatine phosphate and plays a key role in controlling the flow of energy to various tissues in the body, especially muscle tissue. CK concentration increases in myocardial infarction, tetanus, multiple trauma causing crush syndrome, electrical injuries, insect bites and rhabdomyolyses syndrome. Rhabdomyolysis is a syndrome that occurs when damaged skeletal muscle releases a series of substances in muscle cells into the bloodstream, including creatine kinase (CK), accompanied by symptoms of myalgia and the appearance of myoglobinuria (rhabdomyolysis releases intracellular enzymatic content into the bloodstream that leads to systemic complication. The classic presentation of this condition is muscle pain, weakness, black-tea colored urine-pigmenturia and a marked elevation in serum creatine kinase-CK five to ten times above the upper limit of normal serum level, with development of life-threatening complications such as acute kidney injury). This syndrome can be life threatening when causing electrolyte imbalance and acute kidney damage. In trauma and severe burns, up to 50% of patients have rhabdomyolysis syndrome.^1,2,3 Gabow et al. proposed to take CK values 5 times compared to normal as diagnostic criteria for rhabdomyolysis.⁴

Burns caused by high-voltage currents cause damage to skin, tendons, muscles, bones, blood vessels, brains, organs... (injured tissue situated under the skin: tendon, muscles, bones, blood vessels and so on) corresponding to the path of the electricity current in the body.⁵ The extent of damage shown on the skin surface is only a “floating iceberg”. Damage to the tendon, muscle, joints etc. is common, with a high amputation rate from 18.5 to 44% and the risk of acute kidney injury (AKI).^1,4,6 Jurgen et al. studied 42 patients with electric burns that showed that the plasma CK index increased in the first 10 days after burns, proportional to the length of hospital stay and complications of renal failure and limb amputation.⁷

Assessing CK index in patients with electric burns has a predictive value for degree of muscle damage, the risk of amputation, and the prevention of renal failure complications in the first days after burns.^5,8

We conducted this study with the desire to understand the correlation between plasma CK enzyme levels and the level of muscle damage in high-voltage burn patients.

Materials and methods

A retrospective study was conducted between January 2018 and December 2018 on 104 patients in Viet Nam National Burn Hospital who suffered burn injury caused by high-voltage electricity. Patients were divided into two groups: patients with limb amputations in group A (n=20) and patients without limb amputations in group B (n=84). The collected data were processed using SPSS 20.0 software. All cases were tested for plasma CK enzyme immediately after admission to the inpatient hospital and/or one day after amputation surgery. The CK enzyme index of patients was compared between the two groups and with the index in normal people. The average values of plasma CK were compared before and after limb amputation. Testing of CK plasma enzyme was conducted on an AU480 machine manufactured by Beckman Coulter.

Results

In total, the data of 104 patients were analyzed. CK level was recorded and increased on day 1 to day 2 after a high-voltage burn. There were 97 males and 7 females, with an average age of 37.1 years (range 16- 83 years). The common burn area was 12.90±0.97% of total burn surface area (TBSA) and deep burn area was 5.89±0.55% of TBSA. All patients had a change in color of urine, oliguria. The percentage of amputation of the limb was 13.8%. Seven patients died, the cause of death being multiple organ failure in 6 patients and septic shock in 1 patient (Table I).

Table I. Clinical characteristics of patients.

In the group of patients with amputation in group A (n=20), the plasma CK index increased to very high levels, from 15.6 to 46.5 times compared with normal CK index. The CK level increased from the first day of inpatient stay to the 4th day post-operation, average 6.5 days. The deeper the burn area, the higher the plasma CK levels. One day after limb amputation surgery, the plasma CK enzyme index was examined and found to have decreased significantly from 52931.21±4200.94 U/l to 733.97±432.01 U/l (p=0.00001). In group B-without amputation patients (n=84), plasma CK index increased for all groups of burn area, from 5.5 to 22.4 times compared with plasma CK in normal subjects (Table II).

Table II. Changes in plasma CK enzyme levels at the beginning of hospital admission in amputation (A) group and without amputation (B) group.

Discussion

In 2018, the number of electrical burn patients receiving inpatient treatment in our hospital was 196, of which men accounted for 96.4%. The statistical data showed that self-employed workers and farmers who do not have safety knowledge and protective equipment are at higher risk of high-voltage burns compared to workers in the electricity industry. The patients with high-voltage burns were mainly workers working under high-voltage lines using a labor tool touching electric lines, or holding a conductor that touched a high-voltage electrical line. Therefore, the entry wound is usually observed on the upper limb and the exit wound is on the lower limb. Electrical burn defects involve multiple tissues, deep necrosis reaches to fasciocutaneous tissues, damages blood vessels, nerves, tendons and muscles, and leads to anaerobe and compartment syndrome. The ratio of limb amputation in our study was 13.8%. In these cases, the muscles in the upper or lower limbs were damaged completely. Dry necrosis and the plasma CK enzyme index increased dramatically at the beginning of admission.

The average number of days of inpatient treatment was 36,88±1,73 days. In severe cases, secondary progressive necrosis commonly occurs after 2-3 weeks. The depth of the injury is not consistent so tangential excision must be conducted several times, and the exposed tendons, joints or muscles require covering up by pedicle flaps. In this study, 47 cases were observed to have defects on a combination of upper limb, lower limb and other position, which accounted for 45.1%. This was a consequence of the entry, exit and path of the current when entering the body, and is also consistent with previous studies.2,8

In patients who suffered high-voltage electrical burn injury, especially in the amputated patients group, plasma CK enzyme levels increased significantly in the first days after admission, about 5.6 times to 46.5 times compared to the CK index in normal people (170 U/l). It proved that the deeper the burn area, the greater the plasma CK concentration (Fig. 1). In these patients, the color of urine was dark, oliguria and sometimes signs of rhabdomyolysis appeared immediately in 24-48 hrs after burns. According to some authors, an understanding of the mechanism of rhabdomyolysis syndrome will help physicians take measures to promptly treat and prevent possible complications.^5,9

Fig. 1. Correlation between deep burn area and CK enzyme concentration in plasma in high-voltage burn patients.

In a study on multivariate regression methods on 157 patients with acute rhabdomyolysis, Ward et al.¹⁰ showed: CK index from 1000-6000 U/l = there is a risk of rhabdomyolysis syndrome, CK index from 6000-16000 U/l = high risk of rhabdomyolysis syndrome and CK index >16000 U/l = very high risk of rhabdomyolysis syndrome. The results of the study show that muscle resorption syndrome can be seen in all patients with high-voltage burn even if the burn area is not large. Especially in the group of patients with deep burn and assigned amputation, the enzyme CK plasma concentration was very high (52679.82±27403 U/l). In these cases, the skin was damaged completely, the muscle and vessels were exposed and the limb could not be preserved.

According to Gabow et al.,⁴ plasma CK levels increased to 23800 U/l in patients with rhabdomyolysis syndrome. The plasma CK level increased the highest in the group with severe acute renal failure at 40246.3±47231.8 U/l. Elevated plasma CK enzyme indicates great muscle damage. ^7,9 Given the high degree of variability associated with the course of the pathology, multiple attempts are needed to assess the extent of rhabdomyolysis. ⁶ Therefore, plasma CK test results are valuable for diagnosis and prognosis of rhabdomyolysis syndrome in patients with high-voltage burns.

Ahrenholz et al.¹¹ in a study on patients with electric burns have suggested that elevated plasma CK index is associated with prolonged hospital stay and indications for surgical intervention, with risk of amputation of limb when CK enzyme is >4000 U/L. The study also found a link between elevated CK enzyme in the first 2 days after burns and amputation and death. Thus, in our hospital, we suggested the time for performing amputation surgery was on day 2 or day 3 after high-voltage burns or immediately when the CK level exceeds 4000 U/L. When the patient underwent escharotomy, the limb was saved in patients with highvoltage burns with a burn area <40% of body area. Escharotomy within the first 4-6 hours after the burn prevented progressive tissue necrosis. The half-life of CK enzyme is 1.5 days and it will be reduced by 40-50% compared to the first value. If this indicator does not decrease, it means that muscle cells continue to be damaged or compartment syndrome is progressing. The plasma CK enzyme is a factor that directly reflects muscle breakdown with high sensitivity. It is suggested that patients with high-voltage burns should use plasma CK index as a prognostic indicator to make an indication for intervention for early limb compression release, proactive necrosis removal surgery and prevention of complications.12 In our opinion, the operation to remove necrosis of deep burns or amputation has eliminated the cause of rhabdomyolysis syndrome and significantly decreased plasma CK enzyme index. It was proved by the reduction of the plasma CK index significantly with p=0.00001 (Table III).

Table III. Changes in plasma CK enzymes after interventions in the amputation group.

This study has faced several limitations. Firstly, our retrospective study lacked a monitoring of changes in CK enzyme from highest to normal level in several patients in the group without amputation, because of transferring department for treatment. Secondly, the number of patients with major limb amputation operation was not separated from those with minor amputation. This will be clarified in our next study.

Conclusion

In patients with burns due to high voltage, CK serum index increased significantly on the first day after the burn. The plasma CK enzyme index was higher in the group of patients with assigned amputation compared to the patient group without amputation. Increased plasma CK enzyme ratio was directly proportional to the area of burn and the extent of deep burn injury. After escharotomy and amputation, the plasma CK enzyme index decreased significantly compared to pre-operation values.