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226 results for

Fractional Excretion of Bicarbonate

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121. Toxicity, Barbiturate (Treatment)

to be renally excreted. Urinary alkalinization is not recommended for short-acting barbiturates. Enhancement of urinary elimination may be accomplished with an initial sodium bicarbonate bolus of 1 mEq/kg followed by a constant infusion. This infusion may be made by adding 100-150 mEq of sodium bicarbonate to 850 mL of D5 and titrating to maintain a urine pH of greater than 7.5 with an arterial pH of less than 7.50. The goal should be a urine output of 150-250 mL/h. Risks include hypokalemia, fluid overload (...) it was administered at 30 minutes, 60 minutes, and 120 minutes, respectively, current guidelines in overdose management question its benefit. There is no evidence that the administration of activated charcoal improves clinical outcome. Indeed, its use has decreased to less than 5% of all reported ingestions in recent years. [ ] A single dose of activated charcoal may be given within an hour of overdose if the clinician estimates that a clinically significant fraction of the ingested substance remains in the GI

2014 eMedicine Emergency Medicine

122. Toxicity, Mushrooms (Treatment)

), Boletus edulis (king boletus), Leccinium versipelle (brown birch boletus), and Albatrellus ovinus (sheep polypore). Many of these are identified in field guides as edible. Treatment is with aggressive IV fluid resuscitation and consideration for IV sodium bicarbonate to alkalinize the urine. In rare cases, dialysis may be needed if renal failure occurs. Agitation, commonly observed with hallucinogenic mushrooms, is treated with benzodiazepines; phenothiazines are best avoided in this setting. Other (...) of them demonstrate an important decrease in hepatic necrosis histologically. [ ] A large human case series found an association between both silibinin and NAC and higher survival rates. [ ] Corticosteroids, vitamin C, kutkin, aucubin, and thioctic acid have been used in the past but have no proven benefit and are no longer recommended. Charcoal hemoperfusion and hemodialysis are also ineffective in removing toxins because once the toxin is formed, it is rapidly excreted by the kidneys. Plasma

2014 eMedicine Emergency Medicine

123. Cystinuria (Follow-up)

range of 7-7.5. Acetazolamide inhibits the brush-border carbonic anhydrase of the proximal convoluted tubule, thereby increasing urinary bicarbonate excretion. Acetazolamide is not widely used as a first-line drug and is of questionable efficacy. Sodium bicarbonate was used in the past for alkalinizatoinbut is no longer recommended as a first-line agent. The sodium ion may actually increase the amount of cystine excreted. Chelating agents Cystine-binding and cystine-reducing agents share the ability (...) is important for decision-making processes, and stone site and size also influence further management. See the treatment algorithm image below. Treatment algorithm for cystinuria. Hydration The average homozygous patient with cystinuria excretes 600-1400 mg of cystine per day. The solubility of cystine at a pH level of 7 is 250-300 mg/L. Therefore, one of the oldest and most effective cystine stone–prevention techniques is hyperdiuresis to decrease urinary cystine concentration. Early studies by Dent et al

2014 eMedicine.com

124. Toxicity, Mushroom (Follow-up)

), Boletus edulis (king boletus), Leccinium versipelle (brown birch boletus), and Albatrellus ovinus (sheep polypore). Many of these are identified in field guides as edible. Treatment is with aggressive IV fluid resuscitation and consideration for IV sodium bicarbonate to alkalinize the urine. In rare cases, dialysis may be needed if renal failure occurs. Agitation, commonly observed with hallucinogenic mushrooms, is treated with benzodiazepines; phenothiazines are best avoided in this setting. Other (...) of them demonstrate an important decrease in hepatic necrosis histologically. [ ] A large human case series found an association between both silibinin and NAC and higher survival rates. [ ] Corticosteroids, vitamin C, kutkin, aucubin, and thioctic acid have been used in the past but have no proven benefit and are no longer recommended. Charcoal hemoperfusion and hemodialysis are also ineffective in removing toxins because once the toxin is formed, it is rapidly excreted by the kidneys. Plasma

2014 eMedicine.com

125. Syndrome of Inappropriate Secretion of Antidiuretic Hormone (Diagnosis)

, the nonphysiological secretion of AVP results in enhanced water reabsorption, leading to dilutional hyponatremia. While a large fraction of this water is intracellular, the extracellular fraction causes volume expansion. Volume receptors are activated and natriuretic peptides are secreted, which causes natriuresis and some degree of accompanying potassium excretion (kaliuresis). Eventually, a steady state is reached and the amount of Na + excreted in the urine matches Na intake. Ingestion of water is an essential (...) of the antidiuretic hormone arginine vasopressin (AVP) despite normal or increased plasma volume, which results in impaired water excretion. [ ] The key to understanding the pathophysiology, signs, symptoms, and treatment of SIADH is the awareness that the results from an excess of water rather than a deficiency of sodium. Signs and symptoms Depending on the magnitude and rate of development, hyponatremia may or may not cause symptoms. The history should take into account the following considerations: In general

2014 eMedicine.com

126. Acute Tubular Necrosis (Follow-up)

(red arrow). Finally, intratubular obstruction due to the denuded epithelium and cellular debris is evident (green arrow); note that the denuded tubular epithelial cells clump together because of rearrangement of intercellular adhesion molecules. of 2 Tables Table. Laboratory Findings Used to Differentiate Prerenal Azotemia From ATN Finding Prerenal Azotemia ATN and/or Intrinsic Renal Disease Urine osmolarity (mOsm/kg) >500 < 350 Urine sodium (mmol/d) < 20 >40 Fractional excretion of sodium (FENa (...) ) (%) < 1 >2 Fractional excretion of urea (%) < 35 >50 Urine sediment Bland and/or nonspecific May show muddy brown granular casts Contributor Information and Disclosures Author Nikhil A Shah, MBBS, DNB(Neph) Clinical Research Fellow in Home Dialysis, Nephrologist, University of Alberta Faculty of Medicine and Dentistry, Canada Nikhil A Shah, MBBS, DNB(Neph) is a member of the following medical societies: , , , Canadian Society of Nephrology, , Disclosure: Nothing to disclose. Coauthor(s) Mahendra

2014 eMedicine.com

127. Acute Renal Failure (Follow-up)

be harmful for the patient. Maintenance of volume homeostasis and correction of biochemical abnormalities remain the primary goals of treatment and may include the following measures: Correction of fluid overload with furosemide Correction of severe acidosis with bicarbonate administration, which can be important as a bridge to dialysis Correction of hyperkalemia Correction of hematologic abnormalities (eg, anemia, uremic platelet dysfunction) with measures such as transfusions and administration (...) agents, nonsteroidal anti-inflammatory drugs [NSAIDs]) should be avoided or used with extreme caution. Similarly, all medications cleared by renal excretion should be avoided, or their doses should be adjusted appropriately. A 2013 study indicated that triple therapy using nonsteroidal anti-inflammatory drugs (NSAIDs) with 2 antihypertensive medications—a diuretic along with an angiotensin-converting enzyme (ACE) inhibitor or an angiotensin-receptor blocker (ARB)—significantly increases the risk

2014 eMedicine.com

128. Renal Failure, Acute (Treatment)

that suggest prerenal ARF include the following: Urine specific gravity >1.018 Urine osmolality (mOsm/kg water) >500 Urine sodium (mEq/L) < 15-20 Plasma BUN-creatinine ratio >20 Urine-plasma creatinine ratio >40 Urine indices that suggest ATN include the following: Urine specific gravity < 1.012 Urine osmolality (mOsm/kg water) < 500 Urine sodium (mEq/L) >40 Plasma BUN/creatinine ratio < 10-15 Urine-plasma creatinine ratio < 20 Previous Next: Calculation of Fractional Excretion of Sodium The calculation (...) of fractional excretion of sodium (FeNa) is as follows: FeNa = (urine Na/plasma Na)/(urine creatinine/plasma creatinine) If FeNa is less than 1%, this suggests prerenal acute renal failure (ARF). If FeNa is greater than 1%, this suggests ATN. The advantages of FeNa compared with other indices include the following: Physiologic measure of sodium reabsorption Measured creatinine and sodium clearances, accounting for filtration and reabsorption of sodium FeNa increased before oliguric phase established

2014 eMedicine Emergency Medicine

129. Rhabdomyolysis (Treatment)

Dehydration (hematocrit >50, serum sodium level >150 mEq/L, orthostasis, pulmonary wedge pressure < 5 mm Hg, urinary fractional excretion of sodium < 1%) Sepsis Hyperkalemia or hyperphosphatemia on admission Hypoalbuminemia AKI has occasionally developed in severely dehydrated patients with peak CK levels as low as 2000 IU/L. To prevent renal failure, many authorities advocate urinary alkalization, mannitol, and loop diuretics. Alkalization of urine is believed to be helpful and is based (...) . These invasive studies can assist in the assessment of the intravascular volume.) Repeat the CK assay every 6-12 hours to determine the peak CK level. Aggressive and early hydration with isotonic sodium chloride solution is important for the prevention of pigment-associated renal failure. The composition of repletion fluid is controversial and may also include sodium bicarbonate. Initial fluid use in young children has been recommended to be 20 mL/kg; in adolescents, 1-2 L/h has been recommended. Subsequent

2014 eMedicine Emergency Medicine

130. Azotemia (Diagnosis)

for hypothalamic production of antidiuretic hormone, which exerts its effect in the medullary collecting duct for water reabsorption. Through unknown mechanisms, activation of the sympathetic nervous system leads to enhanced proximal tubular reabsorption of salt and water, as well as BUN, creatinine, calcium, uric acid, and bicarbonate. The net result of these 4 mechanisms of salt and water retention is decreased output and decreased urinary excretion of sodium (< 20 mEq/L). Intrarenal azotemia Intrarenal (...) Failure Study Group. Kidney Int . 1996 Sep. 50 (3):811-8. . . Prakash J, Singh TB, Ghosh B, Malhotra V, Rathore SS, Vohra R, et al. Changing epidemiology of community-acquired acute kidney injury in developing countries: analysis of 2405 cases in 26 years from eastern India. Clin Kidney J . 2013 Apr. 6 (2):150-5. . . Carvounis CP, Nisar S, Guro-Razuman S. Significance of the fractional excretion of urea in the differential diagnosis of acute renal failure. Kidney Int . 2002 Dec. 62(6):2223-9

2014 eMedicine.com

131. Perioperative Management of the Female Patient

% of the time. Although it is most commonly observed in women with small-cell carcinoma of the lung, SIADH is also observed in women with gynecologic and bladder cancers. The management of this disorder may be difficult. SIADH occurs in a state of euvolemic hyponatremia. The hyponatremia is caused by over-secretion of ADH. Because free water cannot be excreted normally, persistent ADH secretion causes water retention, hyponatremia, and progressive expansion of intracellular and extracellular fluid

2014 eMedicine.com

132. Acute Tubular Necrosis (Diagnosis)

From ATN Finding Prerenal Azotemia ATN and/or Intrinsic Renal Disease Urine osmolarity (mOsm/kg) >500 < 350 Urine sodium (mmol/d) < 20 >40 Fractional excretion of sodium (FENa) (%) < 1 >2 Fractional excretion of urea (%) < 35 >50 Urine sediment Bland and/or nonspecific May show muddy brown granular casts Contributor Information and Disclosures Author Nikhil A Shah, MBBS, DNB(Neph) Clinical Research Fellow in Home Dialysis, Nephrologist, University of Alberta Faculty of Medicine and Dentistry (...) , but it also helps in the excretion of these toxins by glomerular filtration and tubular secretion. Exogenous nephrotoxins that cause ATN Aminoglycoside-related toxicity occurs in 10-30% of patients receiving aminoglycosides, even when blood levels are in apparently therapeutic ranges. Risk factors for ATN in these patients include the following: Preexisting liver or renal disease Concomitant use of other nephrotoxins (eg, amphotericin B, radiocontrast media, cisplatin) Shock Advanced age Female sex Higher

2014 eMedicine.com

133. Oliguria (Treatment)

, and an estimation of fluid status is a prerequisite for initial and ongoing therapy. This is accomplished by determination of input and output, body weights, vital signs, skin turgor, capillary refill, peripheral edema, cardiopulmonary examination, serum sodium, and fractional excretion of sodium (FENa). Children with intravascular volume depletion require prompt and vigorous fluid resuscitation. Initial therapy includes isotonic sodium chloride or lactated Ringer solution at 20mL/kg over 30 minutes, which can (...) < 7.2), especially in the presence of hyperkalemia, requires IV bicarbonate therapy. Recognize that bicarbonate therapy requires adequate ventilation (to excrete the carbon dioxide produced) to be effective, and it may precipitate hypocalcemia and hypernatremia. Patients who cannot tolerate a large sodium load (eg, those with congestive heart failure) may be treated in an ICU setting with IV tromethamine (THAM), with provision of adequate ventilatory support pending institution of dialysis. Previous

2014 eMedicine Pediatrics

134. Acidosis, Respiratory (Overview)

, bicarbonate, and protein bound. It diffuses freely across cell membranes, and this diffusion allows it to be efficiently transported from peripheral tissues to the lungs for excretion. When hypercapnia is present, this same property causes excess carbon dioxide to shift intracellularly and decrease intracellular pH. Carbon dioxide (CO 2 ) normally combines with water (H 2 O) to form carbonic acid (H 2 CO 3 ), which then dissociates to release hydrogen ion (H + ) and bicarbonate (HCO 3 (...) substantial changes in pH, and approximately 10% of carbon dioxide is bound to hemoglobin to form carbaminohemoglobin. Cellular buffering elevates plasma bicarbonate (HCO 3 – ) only slightly and causes plasma HCO 3 – to increase by 1 mEq/L for every 10-mm Hg increase in P a CO 2 . Renal compensation for sustained hypercapnia begins in 6-12 hours, but 3-5 days pass before maximal compensation occurs. The kidneys increase excretion of hydrogen ions (predominantly in the form of ammonium [NH 4

2014 eMedicine Pediatrics

135. Fluid, Electrolyte, and Nutrition Management of the Newborn (Follow-up)

output and a serum creatinine that does not decline postnatally or increases may have acute kidney injury (AKI). Urine electrolyte levels and specific gravity may be assessed. If the infant is being treated with diuretics, such as furosemide, results of these tests are difficult to interpret. Calculation of the fractional urinary excretion of sodium in relation to creatinine (FENa) and blood gas analysis may be indicated; metabolic acidosis may be a marker of inadequate tissue perfusion. Previous (...) + excretion and loss of bicarbonate. [ ] During the active growth period after the first week, the need for potassium may increase to 2-3mEq/kg/day, and the need for sodium and chloride may increase to 3-5mEq/kg/day. Some of the smallest preterm infants have sodium requirements of as much as 6-8mEq/kg/day because of the decreased capacity of the kidneys to retain sodium. Previous Next: Fluids and Electrolytes in Common Neonatal Conditions Infants with respiratory distress syndrome need appropriate fluid

2014 eMedicine Pediatrics

136. Rhabdomyolysis (Follow-up)

Dehydration (hematocrit >50, serum sodium level >150 mEq/L, orthostasis, pulmonary wedge pressure < 5 mm Hg, urinary fractional excretion of sodium < 1%) Sepsis Hyperkalemia or hyperphosphatemia on admission Hypoalbuminemia AKI has occasionally developed in severely dehydrated patients with peak CK levels as low as 2000 IU/L. To prevent renal failure, many authorities advocate urinary alkalization, mannitol, and loop diuretics. Alkalization of urine is believed to be helpful and is based (...) . These invasive studies can assist in the assessment of the intravascular volume.) Repeat the CK assay every 6-12 hours to determine the peak CK level. Aggressive and early hydration with isotonic sodium chloride solution is important for the prevention of pigment-associated renal failure. The composition of repletion fluid is controversial and may also include sodium bicarbonate. Initial fluid use in young children has been recommended to be 20 mL/kg; in adolescents, 1-2 L/h has been recommended. Subsequent

2014 eMedicine Pediatrics

137. Acidosis, Respiratory (Diagnosis)

, bicarbonate, and protein bound. It diffuses freely across cell membranes, and this diffusion allows it to be efficiently transported from peripheral tissues to the lungs for excretion. When hypercapnia is present, this same property causes excess carbon dioxide to shift intracellularly and decrease intracellular pH. Carbon dioxide (CO 2 ) normally combines with water (H 2 O) to form carbonic acid (H 2 CO 3 ), which then dissociates to release hydrogen ion (H + ) and bicarbonate (HCO 3 (...) substantial changes in pH, and approximately 10% of carbon dioxide is bound to hemoglobin to form carbaminohemoglobin. Cellular buffering elevates plasma bicarbonate (HCO 3 – ) only slightly and causes plasma HCO 3 – to increase by 1 mEq/L for every 10-mm Hg increase in P a CO 2 . Renal compensation for sustained hypercapnia begins in 6-12 hours, but 3-5 days pass before maximal compensation occurs. The kidneys increase excretion of hydrogen ions (predominantly in the form of ammonium [NH 4

2014 eMedicine Pediatrics

138. Altitude Illness - Pulmonary Syndromes (Diagnosis)

, triggered by oxygen-sensing cells in the carotid body. Increased ventilation produces a higher alveolar PO 2. Concurrently, a lowered alveolar PCO 2 results in a respiratory alkalosis and so acts as to limit the increase in ventilation. Renal compensation, through excretion of bicarbonate ion, gradually brings the blood pH back toward normal and allows further increase in ventilation. This process, termed ventilatory acclimatization, requires approximately 4 days at a given altitude and is greatly (...) Hypoxia is the primary physiological insult on ascent to high altitude. The fraction of oxygen in the atmosphere remains constant (0.21), but the partial pressure of oxygen decreases along with barometric pressure on ascent to altitude. The inspired partial pressure of oxygen (PiO 2 ) is lower still because of water vapor pressure in the airways. At the altitude of La Paz, Bolivia (4000 m; 13,200 ft), PiO 2 is 86.4 mm Hg, which is equivalent to breathing 12% oxygen at sea level. The response

2014 eMedicine Emergency Medicine

139. Altitude Illness - Cerebral Syndromes (Diagnosis)

important immediate response of the body to hypoxia is an increase in minute ventilation, called the hypoxic ventilatory response (HVR), and is triggered by oxygen sensing cells in the carotid bodies. Increased ventilation produces a higher alveolar PO 2. Concurrently, a lowered alveolar PCO 2 produces a respiratory alkalosis, acting as a brake on the respiratory center of the brain and subsequently limiting further increases in ventilation. Renal compensation, through excretion of bicarbonate ions (...) physiological insult on ascent to high altitude. The fraction of oxygen in the atmosphere remains constant (0.21) at all altitudes, but the partial pressure of oxygen decreases along with barometric pressure on ascent to altitude. The inspired partial pressure of oxygen (PiO 2 ) is lower still because of water vapor pressure in the airways. At the altitude of International Airport at La Paz, Bolivia (4062 m; 13,327 ft), PiO 2 is 98.18 mm Hg, which is equivalent to breathing 12.8% oxygen at sea level. See

2014 eMedicine Emergency Medicine

140. Hypocalcemia (Diagnosis)

: Pathophysiology Ionized calcium is the necessary plasma fraction for normal physiologic processes. In the neuromuscular system, ionized calcium facilitates nerve conduction, muscle contraction, and muscle relaxation. Calcium is necessary for bone mineralization and is an important cofactor for hormonal secretion in endocrine organs. At the cellular level, calcium is an important regulator of ion transport and membrane integrity. Calcium turnover is estimated to be 10-20 mEq/day. Approximately 500 mg (...) of calcium is removed from the bones daily and replaced by an equal amount. Normally, the amount of calcium absorbed by the intestines is matched by urinary calcium excretion. Despite these enormous fluxes of calcium, the levels of ionized calcium remain stable because of the rigid control maintained by parathyroid hormone (PTH), vitamin D, and calcitonin through complex feedback loops. These compounds act primarily at bone, renal, and GI sites. Calcium levels are also affected by magnesium

2014 eMedicine Emergency Medicine

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