2014-18 Water and electrolytes disturbances Sodium balance Fluid and Electrolyte Disturbances Water balance Hao, Chuan-Ming MD assium Composition of body Fluids Water is the most abundant constituent in the body 50% of body weight in women Total body water is distributed in two major intravascular(plasma water) and The major ECF particles: Na* CH and HCO3- The predominant ICF osmoles: K* and organic phosphate esters (ATP, creatine phosp and phospholipids 命HO Certain solutes, particularly urea, do ontribute to water shifts across most … membranes and are thus known as ineffective Cell shrinks
2014-1-8 1 Fluid and Electrolyte Disturbances Hao, Chuan-Ming MD Huashan Hospital Water and electrolytes disturbances • Sodium balance – Hypovolemia • Water balance – Hyponatremia – Hypernatremia • Potassium balance – Hypokelemia – hyperkelemia Composition of Body Fluids • Water is the most abundant constituent in the body: – 50% of body weight in women – 60% in men • Total body water is distributed in two major compartments: – 55–75% is intracellular fluid (ICF) – 25–45% is extracellular fluid (ECF) • ECF is subdivided into – intravascular (plasma water) and – extravascular (interstitial) spaces in a ratio of 1:3. 2/3 ECF 1/3 ECF Osmoles • The major ECF particles: Na+ , Cl– and HCO3 – • The predominant ICF osmoles: K+ and organic phosphate esters (ATP, creatine phosphate, and phospholipids) • Certain solutes, particularly urea, do not contribute to water shifts across most membranes and are thus known as ineffective osmoles
2014-18 Water and electrolytes disturbances Sodium balance In the steady state, urinary excretion of Hypovolemia sodium is closely matched to dietary salt Water balance Hyponatremia This balance depends Afferent mechanisms that sense the volume of the Potassium balance ECF compartment relative to its capacitance Hypovolemia A reduction in the volume of the ECF compartment in relation to its capacitance. bsolute hypovolemia, a deficit in sodium reflects The volume of the ecf intravascular and extravascular(interstitial) subcompartments may he same or opposite directions. ICF volume is reflected by plasma osm sodium concentration and may be co disturbed i:注 Causes of hypovolemia EXTRARENAL Clinical features ntestinal fluid loss(diarrhea, vomiting, ileostomy or colostomy secretions) History: vomiting, diarrhea, trauma. ird space loss ma states(heart failure, cirrhosis) Large and more acute fluid losses lead to hypovolemic shock Absolut vasoconstriction and hypoperfusion: (cyanosis, cold and clammy extremities, oliguria and Endocrine disorders(e.g, hypoaldosteronism, adrenal 2
2014-1-8 2 Water and electrolytes disturbances • Sodium balance – Hypovolemia • Water balance – Hyponatremia – Hypernatremia • Potassium balance – Hypokelemia – hyperkelemia Sodium Balance • In the steady state, urinary excretion of sodium is closely matched to dietary salt intake. • This balance depends on: • Afferent mechanisms that sense the volume of the ECF compartment relative to its capacitance • Effector mechanisms that modify the rate of renal sodium excretion Hypovolemia • A reduction in the volume of the ECF compartment in relation to its capacitance. • absolute hypovolemia, a deficit in sodium reflects negative sodium balance. • The volume of the ECF intravascular and extravascular (interstitial) subcompartments may vary in the same or opposite directions. • ICF volume is reflected by plasma osmolality and sodium concentration and may be concomitantly disturbed Causes of hypovolemia Clinical features • History: vomiting, diarrhea, trauma… • Symptoms: Thirst, postural dizziness, oliguria, cyanosis, • Signs of intravascular volume contraction: – decreased jugular venous pressure, – postural hypotension, – postural tachycardia • Large and more acute fluid losses lead to hypovolemic shock: hypotension, – tachycardia, – peripheral vasoconstriction and – hypoperfusion: (cyanosis, cold and clammy extremities, oliguria and altered mental status)
2014-18 Diagnosis 个BUN,个SC,个BUN/SCr(>20 UNa <20 mmol/L(exception: ATN, Vomiting) 音 Treatment Water and electrolytes disturbances Goal: restore normovolemia Sodium balance Mild volume contraction oral route Severe hypovolemia:Ⅳ Water balance Hypernatremia Hypokele Water Balan Disorders of tasis result Water balance is regulated mainly by hirst and urine concentrated iras helos Maximal urine osmolality: 1200 be excreted per day Active Na, Cl reabsorption in TAL
2014-1-8 3 Diagnosis • History & physical examination • Labs: – BUN, SCr, BUN/SCr (>20) – UNa <20 mmol/L (exception: ATN, Vomiting), – UCl < 20 mmol/L (GI) Treatment • Goal: restore normovolumia • Mild volume contraction: oral route • Severe hypovolemia: IV Water and electrolytes disturbances • Sodium balance – Hypovolemia • Water balance – Hyponatremia – Hypernatremia • Potassium balance – Hypokelemia – hyperkelemia Water Balance • Disorders of water homeostasis result in hypo- or hypernatremia • Water balance is regulated mainly by thirst and urine concentration mechanism • The principal determinant of renal water excretion is AVP • Maximal urine osmolality: 1200 mosmol/kg • Minimal urine osmolality: 50 mosmo/kg • Normally about 600 mosmols must be excreted per day • Filtration • Active Na, Cl reabsorption in TAL • AVP
2014-18 AVP Collecting duct principal cell or Blood Side AVP secretion mosmol/kg. AQP4 blood volume and blood pressure. Nonosmotic stimul: nausea, intracerebral angiotensin Il, serotonin, and multiple drugs Half-life in the circulation 10-20 min antidiuretic hormone(ADH) Response to Changes in Serum Osmolality AVP rine osmolality AVP secretion: systemic osmolality, threshold level of 285 S5mAximally effective osmol/kg. vasopressin levels blood volume and blood pressure. Nonosmotic stimul: nausea, intracerebral angiotensin Il, serotonin, and multiple drugs 80284288290294296 erum osmolality (mOsm/) Hypovolemia or hypotension Hyponatremia Plasma sodium concentration less than 135 Hypervolemia The most frequently encountered electrolyte 260270280290300310320330340
2014-1-8 4 AVP • AVP secretion: – systemic osmolality, threshold level of 285 mosmol/kg. – blood volume and blood pressure. • Nonosmotic stimul: nausea, intracerebral angiotensin II, serotonin, and multiple drugs. • Half-life in the circulation: 10–20 min AVP • AVP secretion: – systemic osmolality, threshold level of 285 mosmol/kg. – blood volume and blood pressure. • Nonosmotic stimul: nausea, intracerebral angiotensin II, serotonin, and multiple drugs. • Half-life in the circulation: 10–20 min Hyponatremia • Plasma sodium concentration less than 135 mmol/L, • The most frequently encountered electrolyte abnormality in hospitalized patients
2014-18 olar Disorde Depletion effective solutes such as Primary Decreases in Total Body solute very high concentrations of glucose in diabetic patients or Secondary Water Retention Isotonic hyponatremia: hyperlipidemia or marked perglobulinemia-pseudohyponatremia True hypotonic hyponatremia: portant underlying disorder that leads to abnormal dy water balanc the hypotonic state indicates either past or ongoing ution(Primary Increases in Total Body Water* Secondary Solute Primary Decreases in Total Body Solute Secondary Water Impaired Renal Free Water Excretion Retention mpaired Distal Dilution inappropriate antidiuretic hormone secretion(SIADH) Combined Increased Proximal Reabsorption and impa ired Distal Nonrenal Solute Loss Gastrointestinal (diarrhea, vomiting, pancreatitis, bowel Congestive heart failure obstruction utaneous(sweating, burns Blood loss Decreased Urinary Solute Excretion Beer pototan Excess Water Intake Diagnostic Criteria for the Syndrome of Inappropriate ADH Release AL NERVOUS SYSTEM DISORDER Essential Diagnostic Criteria 1 c2ro mosman H or mud erective osmoasly Inappropriate urinary concentration (>100 mosm/kg H2 O) PULMONARY DESORDEI DH Elevated urinary Na concentration under conditions of normal Absence of adrenal, thyroid, pituitary, or renal insufficiency or ED Criterin 物bm H level inappropriately elevated relative to No significant correction af plasma Na level with volume 5
2014-1-8 5 • Hypertonic hyponatremia: an accumulation in the ECF compartment of non-sodium-containing effective solutes such as – very high concentrations of glucose in diabetic patients or – exogenously administered mannitol or glycerol. • Isotonic hyponatremia: hyperlipidemia or marked hyperglobulinemia – pseudohyponatremia • True hypotonic hyponatremia: – an important underlying disorder that leads to abnormal body water balance, – the hypotonic state indicates either past or ongoing expansion of ICF volume. Hypo-osmolar Disorders • Depletion: – Primary Decreases in Total Body Solute + Secondary Water Retention • Dilution: – Primary Increases in Total Body Water ± Secondary Solute Depletion Causes of SIADH