Cellular and humoral immunity are altered in patients with renal failure. Infection is frequent and is the major cause of mortality in AKF patients. Physicians have to be aware of this eventuality and use appropriate antibiotics promptly. The dose of antibiotics (and other drugs)
should he adjusted for rhe degree of renal function (sec recommended readings).
It is very important to weigh rlie patients daily to assess adequacy of fluid balance. 1'atients with A.RF have ati increase in catabolism which should be reflected in a decrease in tissue mass, The dry weight should fall around 0.2-0.^ kg/day and even more in patients with bypercatabol-ism Tissue diabolism produces "endogenous" water which is different for carbohydrates, lipids and proteins (sec appendix). The weight reflects fluid intake, output and catabolism. i"hcrcforc, a patient with ARF should lose~0 5 kg/day if his fluid balance is well managed. However, hypcrcataholism in these patients can be halted with early and continuous high caloric intake.
Right!. The kidney is opening up and it begins to make more urine, During this period the kidney eliminates water and not toxic products, In other words, the urine increases in quantity but not in quality (Fig. 33). Therefore, the patient is still uremic, but an incneaiie in urine output decreases any fluid overload which, usually, hail complicated the oliguric period in spite of efforts to maintain good fluid balance.
PERIOD III (The Kidney Begin» to Open Up)
(The Kidney is Working Again!)
This period is called polyudc. I fere, fhe urine output increases further but now ihe kidney is mskJns urine of better quality Than in the previous period, and concentrating mechanisms recover slowly. There is an increase in the excretion of urea, creatinine, potassium etc. (Fig. During this period ihe urine output can he very high (10 liters per 24 hniirs or even more). Thi.i ircmcndons urine ntirput is secondary to hoih the increase In urinary urea, that aces as an osmotic diuretic, and to the fact that the concentrating mechanisms of the kidney are not, yet. fully recovered. We have to watch the patient very closely, because the In-crease in urine output will increase electrolyte excretion ajid cause severe hypokalemia, hyponatremia and hypomagncscmia as well as orthostatic hypotension.
During this period the uremic symptoms improve slowly,
Ftgufe 34 Pbl^uric phase: increase of urine output (polyiiria^ >2 literg/24iiFs) with Hi ereasa at eliimnalnni or substances ( ur&a, creatinrw, oleclnciiytes etc,),
Two to three weeks after "the kidney starts opening up" renal function is almost hack to normal. However, the anemia and a decrease in the ability to maximally conccntratc or dilute the urine may last longer. Therefore, the patient has to be careful with excessive fluid and salt intake, while the kidney completely recover* its concentrating mechanisms.
PERIOD V (The Kidney is naclt to Normal)
DIFFERENTIAL DIAGNOSIS AND PROGNOSIS
The differential diagnosis includes prerenal, intrinsic and postrenal acute renal failure
First obtain a good medical history and perform a physical examination. This gives an idea of what is happening to the patient, e g,f excessive fluid losses (diarrhea), weight loss and orthostatic hypotension suggests dehydration (Fig, 35). A history of heart disease with acute
Lov/ FtAMb INTRfcE.
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