Comparison of urine anion gap, urine osmolal gap and modified urine osmolal gap in assessing the urine ammonium in metabolic acidosis.

Twenty-four hour urine and spot urine samples from 29 patients with metabolic acidosis were collected for evaluation of urine ammonium in relation to urine anion gap, urine osmolal gap (OG) and modified urine osmolal gap (MOG). Their underlying diseases included SLE in 8, RTA in 7, CRF in 6, RPGN in 2 (one with SLE), Lowe syndrome in 2, on acetazolamide in 2, gastroenteritis in 2, and CAH in one. Twenty-three patients had normal serum anion gap (< 14 mmol/L). Their mean CO2 was 13.77 (9.4-17.9) mmol/L, net acid excretion (NAE) was 33.18 +/- 35.36 mmol/24 hour, NH+4 excretion was 29.16 +/- 31.97 mmol/24 hour. Neither the 24-hour urine nor spot urine anion gap correlated with corresponding urine NH+4 with or without adding urine HCO-3 in the calculation. Spot urine NH+4 correlated well with urine OG (r2 = 0.82, p < 0.001) and less with MOG (r2 = 0.339, p < 0.006). The urine osmolality was well correlated with the sum of 2 (Na+ + K+ + NH+4) + urea for both spot (r2 = 0.990, p < 0.001) and 24 hour urine (r2 = 0.907, p < 0.001) collection. Twenty-four hour urine NH+4 did not correlate with the OG or the MOG. There was no correlation between spot urine NH4/Cr ratio and 24 hour urine NH4/Cr ratio (r2 = 0.243, p = 0.53) nor between spot NAE/Cr ratio and 24 hour urine NAE/Cr ratio (r2 = 0.380, p = 0.014). Therefore in the presence of low urine NH+4 (< 100 mmol/L), urine osmolal gap may be used to determine urine NH+4 indirectly with good correlation. Twenty-four hour urine collection is still necessary to assess renal acidification.

Single daily dose of gentamicin in the treatment of pediatric urinary tract infection.

Fourty-nine patients aged 6 months to 12 years old with suspected urinary tract infection (UTI) were evaluated in this open randomized study. Twenty-seven patients received gentamicin 4.5 mg/kg/d once daily (OD group) and 22 patients received the same daily dose in three divided doses (TID group) for 3 days before being switched to amoxy-clavulanic acid. Ninety-six per cent (26/27) of the OD group had peak gentamicin within therapeutic level while 40 per cent (9/22) of the TID group had peak gentamicin within therapeutic level. One in OD group had high gentamicin level due to technical error in obtaining blood sample. None in neither group had trough level in toxic level. Only 24 patients had confirmed UTI and were evaluated for clinical efficacy and toxicity. Demographic data were the same in both groups except there were more males in OD group (8:3 vs 4:9). Patients in OD group became afebrile earlier than TID group (8.69 vs 15.31 hours) but no statistically significant difference. All patients had negative urine culture results within 48 hours. None had clinical nephrotoxicity in both groups. More patients in TID group had laboratory nephrotoxicity (5/11 vs 2/13) but no statistically significant difference. We conclude that gentamicin can be given safely and efficiently as single daily dose or thrice daily but more cost effective and less time consuming in once daily dose.