Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
➤ Gửi thông báo lỗi ⚠️ Báo cáo tài liệu vi phạmNội dung chi tiết: Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
co.Title: ainlcal Physiology of Acid-Base and Electrolyte Disorders, 5th Edition'Copyright ©2001 McGraw-Hill> Table of CcrttrCs > Par: Three - Physclo Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2ogic iporoach to Add-Base and Electrode ctsonders > chapter Thirteen • Meaning and Aspiration of ume OnemistnesChapter ThirteenMeaning and Application of Urine ChemistriesAs IS discussed in the ensuing chapters, measurement of the urinary electrolyte concentrations, osmolality, and pH plays an Impor Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2tant role in the diagnosis and management of a variety of disorders. This chapter briefly reviews the meaning of these parameters and the settings inEbook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
which they may be helpful (Table 13-1). It is important to emphasize that there are no fixed normal values, since the kidney varies the rate of excretco.Title: ainlcal Physiology of Acid-Base and Electrolyte Disorders, 5th Edition'Copyright ©2001 McGraw-Hill> Table of CcrttrCs > Par: Three - Physclo Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2 an example, the urinary excretion of 125 meq of Na4 per day may be appropriate for a subject on a regular diet, but represents inappropriate renal Na+ wasting in a patient who is volume-depleted.In addition to being clinically useful, these tests are simple to perform and widely available. In most Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2circumstances, a random unne specimen Is sufficient, although a 24-h collection to determine the daily rate of solute excretion IS occasionally indicaEbook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
ted. When K* deplebon Is due to extrarenal losses, for example, the urinary K* excretion should fall below 25 meq/day. In some patients, however, randco.Title: ainlcal Physiology of Acid-Base and Electrolyte Disorders, 5th Edition'Copyright ©2001 McGraw-Hill> Table of CcrttrCs > Par: Three - Physclo Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2 20 meq of K+ per day will be associated with an apparently high urine K4 concentration of 40 meq/L (20 meq/day-r 0.5 ựday=40 meq/L).Table 13-1 Clinical application of urine chemistriesParameterUses Assessment of volume statusNa+ excretionDiagnosis of hyponatremia and acute renal failure Dietary com Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2pliance in patients with hypertension Evaluation of calcium and uric acid excretion in stone formersCI’excretionSimilar to that for Na+ excretion DiagEbook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
nosis of metabolic alkalosis Urine anion gapK+ excretionDiagnosis of hypokalemiaOsmolality or specific gravityDiagnosis of hyponatremia, hypernatremiaco.Title: ainlcal Physiology of Acid-Base and Electrolyte Disorders, 5th Edition'Copyright ©2001 McGraw-Hill> Table of CcrttrCs > Par: Three - Physclo Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2idney vanes the rate of Na4 excrebon to maintain the effective circulabng volume, a response that Is mediated by a variety of factors, including the renln-angiotensin-aldosterone system and perhaps atrial natrlurebc peptide and related peptides (see Chap. 8). As a result, the unne Na* concentration Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2can be used as an esbmate of the patient's volume status. In particular, a urine Na* concentration below 20 meq/L Is generally indicative of hypovolemEbook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
ia. This finding Is especially useful in the differenbal diagnosis of both hyponatremia and acute renal failure. The two major causes of hyponatremia co.Title: ainlcal Physiology of Acid-Base and Electrolyte Disorders, 5th Edition'Copyright ©2001 McGraw-Hill> Table of CcrttrCs > Par: Three - Physclo Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2 former, but greater than 40 meq/L In the SIAOH, which Is characterized by water retention but normal Na* handling (i.e., output equal to Intake; see Chap. 23).Similar considerations apply to acute renal failure, which is most often due to volume deplebon or acute tubular necrosis.1 The urineNa* con Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2centration usually exceeds 40 meq/L In the latter, in part because of the associated tubul hftnQ*//khnthlivipr mm to maximally reabsorb Na*.1’2 and 3Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
Measuring the fractional excretion of Na* and the urine osm> 'lupa.imiiuuiuv It-11.UUIII between these conditions (see below).In normal subjects, urinco.Title: ainlcal Physiology of Acid-Base and Electrolyte Disorders, 5th Edition'Copyright ©2001 McGraw-Hill> Table of CcrttrCs > Par: Three - Physclo Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2eck dietary compliance in patients with essential hypertension. Restriction of Na* intake is frequently an Important component of the therapeutic regimen/ and adequate adherence should result in the excretion of less than 100 meq/day.The concurrent use of diuretics does not interfere with tne utilit Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2y of this test as long as drug dose and dietary intake are relatively constant. A thiazide diuretic, for example, Initially increases Na* and water exEbook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
cretion by reducing Na' transport in the distal tubule. However, the diuresis is attenuated over a period of days, because the ensuing volume depletioco.Title: ainlcal Physiology of Acid-Base and Electrolyte Disorders, 5th Edition'Copyright ©2001 McGraw-Hill> Table of CcrttrCs > Par: Three - Physclo Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2t is the establishment within 1 week of a new steady state in which the plasma volume is somewhat diminished, but .'Vé* excretion is again equal to intake (see Fig. 15-2)/Measurement of urinary Na1 excretion IS also Important when evaluating patients with recurrent kidney stones. A 24-h urine collec Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2tion IS typically obtained in this setting to determine If calcium or uric acid excretion IS increased, both of which can predispose to stone formatioEbook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
n.0-However, the tubular reabsorption of both calcium and uric add Is Indirectly linked to that of Na' (see Chap. 3). Thus, the increased Na' reabsorpco.Title: ainlcal Physiology of Acid-Base and Electrolyte Disorders, 5th Edition'Copyright ©2001 McGraw-Hill> Table of CcrttrCs > Par: Three - Physclo Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2 that volume depletion IS not a limiting factor for calcium or uric add excretion.LimitationsDespite its usefulness, there are some pitfalls in relying upon the measurement of Na* excretion as an index of volume status. A low urine Na1 concentration, for example, may be seen in normovolemic pabents Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2who have selective renal or glomerular ischemia due to bilateral renal artery stenosis or acute glomerulonephritis.2--2 On the other hand, a defect inEbook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
tubular Na- reabsorption can lead to a high rate of Na* excretion, despite the presence of volume depletion. This can occur with the use of diureticsco.Title: ainlcal Physiology of Acid-Base and Electrolyte Disorders, 5th Edition'Copyright ©2001 McGraw-Hill> Table of CcrttrCs > Par: Three - Physclo Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2 can be exemplified by central diabetes insipidus, a disorder in which a deficiency of antidiuretic hormone (ADH) can lead to a urine output exceeding 10 L/day. In this setting, the daily excretion of 100 meq of Na’ will be associated with a urine Na* concentration of 10 meq/L or less, incorrectly s Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2uggesting the presence of volume depletion. Conversely, a high rate of water reabsorption can raise the urine Na* concentration and mask the presenceEbook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
of hypovolemia. To remove the effect of water reabsorption, the renal handling of Na* can be evaluated directly by calculating the fractional excretioco.Title: ainlcal Physiology of Acid-Base and Electrolyte Disorders, 5th Edition'Copyright ©2001 McGraw-Hill> Table of CcrttrCs > Par: Three - Physclo Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2y of Na * filteredThe quantity of Na* excreted 1$ equal to the product of the urine Na* concentration (UNa) and the urine flow rate (V): the quantity of Na’ filtered IS equal to the product of the plasma Na' concentration (PNa) and the glomerular filtration rate (or creatinine clearance, which is eq Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2ual to Uy X V/Py). Thus,UN:. X VFEn“ Pnu X (Ucr X V/PCT) x 100f-No X PerPNa X UcrX 100The primary use of the FEU1 IS In patients with acute renal failEbook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
ure. As described above, a low urine Na1 concentration favors the diagnosis of volume depletion, whereas a high value points toward acute tubular necrco.Title: ainlcal Physiology of Acid-Base and Electrolyte Disorders, 5th Edition'Copyright ©2001 McGraw-Hill> Table of CcrttrCs > Par: Three - Physclo Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2ter reabsorption, can be minimized by calculating the FENa.iJ-1'1 Na* reabsorption is appropriately enhanced in hypovolemic states, and the FENe is usually less than 1 percent: I.e., more than 99 percent of the filtered Na1 has been reabsorbed. In contrast, tubular damage leads to a FEto In excess o Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2f 2 to 3 percent In most patients with acute tubular necrosis.There are, however, exceptions to this general rule, as the FEfva may be less than 1 perEbook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
cent when acute tubular necrosis is superimposed upon chronic effective volume depletion (as occurs in cirrhosis, heart failure, and burns) or when Itco.Title: ainlcal Physiology of Acid-Base and Electrolyte Disorders, 5th Edition'Copyright ©2001 McGraw-Hill> Table of CcrttrCs > Par: Three - Physclo Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2 may be better preserved In these disorders.14LimitationsThe major limitation in the use of the FEM, Is that it is dependent upon the amount of Na* filtered, and therefore the dividing line between volume depletion and normovolemia is not always 1 percent. This can be best appreciated in patients wi Ebook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2th normal renal function. If the glomerular filtration rate (GFR) is ISO ựday (125 mựmin) and the plasma Na* concentration is 150 meq/L, then 27,000 mEbook Clinical physiology of acid - base and electrolyte disorders (5th edition): Part 2
eq of Na* will be filtered each day. As a result, the FEfla will always be under 1 percent as long as daily Na* intake IS in the usual range of 125 toGọi ngay
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