Management of Snakebite and Research Management of Snakebite ...

INTRODUCTION
Urinary NAG: An Indicator for Detection of Early Renal Damage in Russell’s Viper Bite Cases
Oliguric acute renal failure (ARF) is the commonest severe clinical manifestation responsible
for most deaths from Russell’s viper (Daboia russelli siamensis) bite in Myanmar. Being a
national health problem in the country, much has been studied on various aspects of
laboratory diagnosis of Russell viper envenomation and its fatal complications. Recently, a
great deal of interest has been focused on the utilization of the urinary enzyme, N-acetyl
ß-D glucosaminidase (NAG; ß-N acetylglucosa-minidase, EC 3.2.1.30 ) , for early diagnosis
of renal damage since the activities of urinary NAG increase before the results of other
renal function tests become abnormal (Prince & Dance) 1 . Measurement of urinary NAG
has been reported to be a sensitive and specific indicator of renal damage in patients with
any disease reported to show renal involvement and may prove valuable for early detection
of renal injury prior to manifestation by other renal function tests 2 . This review summarizes
the results of a wide range of studies on the urinary NAG activities in Russell’s viper (RV)
bite patients carried out by members of the Scientific group on Snake Bite Research at the
Department of Medical Research (Lower Myanmar).
1. Urinary NAG in RV bite victims with acute renal failure
The activities of urinary NAG excretion in 23 RV bite patients with ARF following the
systemic envenomation were studied and compared with the results of other routine
standard renal function tests 3 . In this study, urinary NAG activities, urinary albumin, blood
urea, serum creatinine and creratinine clearance were measured in these patients at different
time intervals after the bite during clinical observation for 5 days. Urinary NAG was measured
by using the method of Levvy and Conchie (1966 ) 4 in which a substrate p-nitro phenyl-Nacetyl-ß-D
glucosaminidase is converted by NAG present in the urine, in the presence of
0.08% of Bovine serum albumin (BSA) and 0.2 M citrate buffer, into p nitrophenol
(pNP ) and N acetyl-ß-D-glucosamine. After incubation for one hour at 38 C, this enzyme
catalyzed reaction is terminated by the addition of an inhibitor, glycine–NaOH buffer. The
liberated end product, pNP (yellow colour) was measured by spectrophotometer at 430
nm and the enzyme activity of NAG was calculated by using the molar extinction coefficient
of pNP. Activities of NAG were compared with other indicators of renal function in three
clinical conditions; namely non oliguric acute renal failure (ARF), oliguric ARF not requiring
peritoneal dialysis (PD) and oliguric ARF requiring PD. Cut-off values to identify the three
conditions were established by using the non-parametric Fisher’s exact test. Results of this
study showed that urinary NAG activities were found to be raised at the time of admission
at the hospital in all types of ARF.
When the times of onset of the condition, indicated by the cut-off values were
compared, urinary NAG was found to be the earliest indicator of renal damage. In each
type of ARF, the urinary NAG level was abnormal before changes in the values of the other
indicators of renal function. Besides, it may be possible to predict the types of ARF within
two hours after the bite by measuring the activities of urinary NAG as shown in the table
mentioned below.
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