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Showing posts with label Renal impairment. Show all posts
Showing posts with label Renal impairment. Show all posts
Assessment of renal function
By Piscean | Sunday, September 18, 2011 | Posted in , , | With 0 comments

Adults
To make best use of the recommendations in Table 2.33, it is necessary to calculate creatinine clearance (CrCl) if it has not been formally measured and to use this value as an estimate of the glomerular filtration rate (GFR). The most widely recommended method for doing this is to use the modified Cockcroft-Gault formula:

Adult males:

Adult females:
Multiply the above equation by 0.85
Use the patient’s height and Table 2.31 to determine the ideal weight. (The actual weight is usually satisfactory, except in the morbidly obese.) The above formula will not accurately predict clearance in patients with rapidly changing renal function. A guide to calculating creatinine clearance in children is shown in Table 2.32.

Click here for creatinine clearance and ideal body weight calculators.
Although automated reporting of the estimated glomerular filtration rate (eGFR) has been recommended practice in Australia since 2005, the eGFR has not been validated for drug dosing, and the dose modifications recommended in Table 2.33 are based on the assumption that clearance has been calculated using the Cockcroft-Gault formula.

Ideal body weight (Table 2.31)
Height Ideal body weight (kg) [NB1]
cm inches female male
155
61
48
53
160
63
53
57
165
65
57
62
170
67
62
66
175
69
66
71
180
71
71
75
185
73
75
80
190
75
80
84
195
77
84
89
200
79
89
93
205
81
93
98
210
83
98
102
215
85
102
107
220
87
107
111
NB1: Ideal weight for male = 50 kg + 0.9 kg/each cm over 152 cm (2.3 kg/each inch over 5 feet)
Ideal weight for female = 45.5 kg + 0.9 kg/each cm over 152 cm (2.3 kg/each inch over 5 feet)

Children
When treating children, the appropriate dose for normal renal function should be calculated, then modified according to the guidelines in Table 2.33. A guide to calculating creatinine clearance in children is given in Table 2.32.

Guide to calculating creatinine clearance (mL/min) in patients under 21 years (Table 2.32)
Age Formula
1 month to <2 years
40 x height (cm)/serum creatinine (micromol/L)
2 to <12 years
49 x height (cm)/serum creatinine (micromol/L)
12 to 20 years (female)
49 x height (cm)/serum creatinine (micromol/L)
12 to 20 years (male)
62 x height (cm)/serum creatinine (micromol/L)
Renal impairment and antimicrobial dosing
By Piscean | | Posted in , , | With 0 comments

Renal impairment and antimicrobial dosing
In the presence of renal impairment, antimicrobials and/or their metabolites that are excreted totally or in part by the kidneys may accumulate, and dosage adjustment may be required. For example, aminoglycosides depend almost entirely on the kidneys for their clearance and will rapidly reach toxic levels in patients with impaired renal function if standard dosing schedules are used. Table 2.33 provides a guide to initial antimicrobial regimens, based on creatinine clearance.