1Populations with lower total body water percentage and calculation for men and women
Patients with obesity and older adults. men: 0.5 L/kg Women 0.45 L/kg
2Simple weight-based adult daily fluid estimate
30-35 mL/kg/day.
3Increase in insensible fluid losses with ___ and ___
diarrhea and fever
4Electrolytes that are higher in extracellular fluid (plasma)
sodium, chloride, bicarbonate, calcium (none is considered intracellular/muscle)
5Electrolytes that are higher in intracellular fluid (muscle)
potassium, magnesium, phosphate
6GI secretion with highest chloride concentration (mEq/L)
stomach - 100-130 duodenum, jejunum/ileus - 90-120
7GI secretions rich in bicarbonate
Pancreatic - 115 duodenal secretions - 80 jejunal/ileal (30-40) and bile (30) also contain it.
8which GI secretions do not contain bicarb
stomach and colon
9whicj GI secretions do not contain magnesium
duodenum
10Lower-GI fluid loss causing important potassium losses
Colon (20-30)/diarrheal losses. stomach (10-15) mEq/L
11Sodium contents of GI fluids
colon - 60 bile- 140 duodenum - 140 pancreas - 140 mEq/L stomach - 60-90 jejunum/ileum 140
12Sodium and chloride content of 0.9% NaCl
154 mEq/L sodium and 154 mEq/L chloride.
13Sodium and chloride content of 0.45% NaCl
77 mEq/L sodium and 77 mEq/L chloride.
14Sodium concentration of 3% NaCl
513 mEq/L.
15Chloride concentration of 3% NaCl
513 mEq/L.
16Electrolytes in Lactated Ringer's (LR)
Na 130, K 4, Cl 109, HCO₃ eq 28, Ca 2.7 mEq/L.
17Electrolytes in Plasma-Lyte A / Normosol-R
Na 140 K 5, Cl 98, HCO₃ eq 27 Mg 3 mEq/L.
18Balanced crystalloid containing calcium
Lactated Ringer's.
19Balanced crystalloid containing magnesium
Plasma-Lyte A / Normosol-R.
20Sodium correction for hyperglycemia cocept
Add 2.4 mEq/L Na for every 100 mg/dL glucose above 100.
21Sodium correction formula for hyperglycemia
Corrected Na = measured Na + [((BG − 100)/100) × 2.4]
22Lab conditions causing pseudohyponatremia (isotonic hyponatremia)
Severe lipemia (triglycerides >1000 mg/dL) or hyperproteinemia (e.g., multiple myeloma).
23Serum osmolality defining hypotonic hyponatremia
Serum osmolality <280 mOsm/kg.
24guidelines: Why check urine sodium/osmolality before ECF volume in ICU?
ECF volume status is notoriously difficult to determine in critically ill patients.
25Hypervolemic hyponatremia physiologic findings
edema large positive fluid balance pulmonary infiltrates (without PNA) enlarged heart increased pulmonary capillary wedge pressure and/or end diastolic volume index
26hypovolemic hyponatremia physiologic findings
poor skin tugor dry mucous membranes decreased urine output concentrated urine tachycardia BUN/Scr >20
27Urine osmolality >450 + urine sodium >20 = ____ and may be caused by:
hypovolemic hyponatremia -diuretics -have adrenal insufficiency -cerebral salt wasting -thiazides -salt wasting nephropathy
28Urine osmolality >450 + urine sodium <20 = ____ and may be caused by:
hypovolemic hyponatremia GI fluid third spacing
29urien mOsm/kg >100 Urine Na >20
euvolemic hypoNa SIADH hypothyroidism
30urien mOsm/kg <100 Urine Na <20
euvolemic hypona excessive hypotonic fluids
31hypervolemic hyponatremia
urine mOsm/kg >100 urine Na >20: renal failure urine Na <20: CHf, cirrhosis with ascites fluid and sodium restriction diuretics as needed vaptan
32hypovolemic hupoNa treatment
give sodium and fluids reduce diuretis
33CSWS vs SIADH in TBI difference
CSWS is hypovolemic (decreased ECF); SIADH is euvolemic/hypervolemic.
34Urine sodium and osmolality in CSWS and SIADH
Both are increased in both conditions.
35Hemodynamic markers in CSWS vs SIADH
CVP, PCWP, and EDVI are decreased in CSWS; normal/increased in SIADH.
36sodium balance in CSWS vs SIADH
CSWS: negative SIADH: variable
37What patients is active hyponatremia treatment reserved for?
Acute hyponatremia (<48 hours) and/or severe symptoms (coma, seizures, mental status changes regardless if acute or chronic)
38Therapy for severe symptomatic hyponatremia
Hypertonic saline (usually 3% sodium chloride). 150 mL (2 mL/kg) IV over 20 minutes x3 or 100 mL Iv over 10 minutes x3
39Initial target sodium increase with hypertonic saline
About 5 mEq/L in the first hour.
40Maximum sodium correction goal in first 24 hours
Limit total increase to about 10 mEq/L.
41Daily sodium correction limit after first 24 hours (until Na reaches 130)
An additional 8 mEq/L per 24 hours. until na 130 or symptom resolution
42Neurologic risk of overly rapid hyponatremia correction
Central pontine myelinolysis / osmotic demyelination syndrome.
43Patients at heightened risk of osmotic demyelination
Na ≤105, alcohol use disorder, hypokalemia, malnutrition, or advanced liver disease.
44Why guidelines prefer bolus over continuous 3% NaCl
Boluses reach target sodium faster and improve GCS scores sooner.
45Purpose of DDAVP clamp in hyponatremia
To prevent overcorrection by controlling water diuresis while giving 3% NaCl.
46DDAVP clamp dose (prevention)
Desmopressin 1-2 mcg IV q6-8h plus 3% NaCl infusion to raise Na ~6 mEq/L/day.
47When is DDAVP clamp appropriate?
Severe hyponatremia with high overcorrection risk (studied only with continuous 3% infusion).
48Avoid DDAVP clamp in (prevention of overcorrection hyponatremia)
Heart failure, hepatic cirrhosis, or volume overload.
49How to relower sodium if overcorrected in high-risk patients (treatment)
Desmopressin 1-4 mcg IV q8h plus free water (3 mL/kg/h) with hourly Na checks.
50Treatment of hypervolemic hyponatremia
Fluid/sodium restriction; diuretics; consider vaptans if other therapies fail.
51Treatment of hypovolemic hyponatremia with low urine sodium
Sodium and fluid for volume expansion; reduce diuretics if applicable.
52IV fluids for hypovolemic hyponatremia volume expansion
0.9% NaCl, Lactated Ringer's, or Plasma-Lyte/Normosol.
53First-line treatment of euvolemic SIADH-type hyponatremia
Fluid restriction or free-water restriction. with 0.9% sodium chloride with or without diuretic therapy
54Options for chronic / refractory SIADH after fluid restriction
Salt tablets, urea, demeclocycline, conivaptan, or tolvaptan.
55Physiologic meaning of hypernatremia
A water deficit relative to total body sodium.
56Safe rate of serum sodium lowering in hypernatremia
Aim for 6-8 mEq/L/day; limit to 10-12 mEq/L/day.
57Neurologic risk of correcting hypernatremia too quickly
Cerebral edema.
58signs and Treatment of hypervolemic hypernatremia
urien MOsm/kg 100 1. urine Na >20: escessive sodium intake diuretics sodium restriction water replacement and or RRT
59Treatment of euvolemic hypernatremia
1. estimated free water deficity: 0.5/0.6 x kg x (sr sodium/140-1) correct over 2-3 days enteral free water boluses 200-300 mL every 4-6 hours D5W or D50.225% Free water replacement.
60Why avoid large enteral water boluses in post-pyloric tubes?
Can cause cramping, diarrhea, and rarely bowel necrosis.
61Formula estimating sodium change after 1 L of IV fluid
(IV fluid Na − serum Na) / (TBW + 1)
62Initial treatment of hypovolemic hypernatremia
Restore hemodynamics with volume expansion first, then replace free water. Initially - voluem expansion to restore hemodynamics then free water replacement once stable
63How often should you check serum sodium when correcting hypernatrmemia
every 6-12 hours
64Normal serum potassium range
3.5-5.2 mEq/L.
65influences on potassium
pH increase, K decreases magnesium influences
66Empiric ICU serum potassium target
K ≥4.0 mEq/L if possible.
67ECG changes with hypokalemia
ST depression, QT prolongation, flat T waves, and U waves.
68which electrolyte being low may lead to hypokalemia?
magnesium
69Medications shifting potassium intracellularly
Beta-agonists, sodium bicarbonate/alkalinizing agents, and insulin.
70Physiologic states shifting potassium intracellularly
Acute alkalemia, hypothermia, and pentobarbital therapy.
71Electrolyte to check/correct in refractory hypokalemia
Magnesium (hypomagnesemia causes refractory hypokalemia).
72Timeframe to replace potassium deficit
Over 1-3 days, depending on severity and ongoing losses.
73Preferred route for potassium replacement in asymptomatic patients
Enteral/oral potassium (safer due to feed-forward mesenteric sensing).
74Why avoid giving liquid KCl directly into the small bowel?
High osmolality can cause cramping, distension, and diarrhea.
75Max IV potassium rate with continuous ECG monitoring (central)
20 mEq/hour.
76Safest IV potassium rate for asymptomatic patients
10 mEq/hour.
77Empiric IV KCl dose for K 3.5-3.6 mEq/L
40-60 mEq.
78Empiric IV KCl dose for K 3.0-3.4 mEq/L
80 mEq.
79Empiric IV KCl dose for K 2.0-2.9 mEq/L
120 mEq (with repeat K checked 1-2 h after).
80When to use potassium phosphate instead of KCl
When hypokalemia and hypophosphatemia are both present.
81Potassium content of 30 mmol potassium phosphate
About 44 mEq potassium.
82Definition of hyperkalemia
Serum K >5.2 mEq/L.
83Threshold where hyperkalemia becomes highly significant
Approaching 6 mEq/L, especially with ECG changes.
84Classic ECG finding for hyperkalemia
Peaked, tented T waves, arrythmias, weakness, paralysis
85When is ctreatment used in hyperkalemia?
Only when ECG changes are present, symptomatic patients K >5.5 mg/dL
86Does IV calcium lower serum potassium?
No, it only stabilizes the myocardium. should be given in addition to other therapies
87When should IV push calcium chloride be avoided?
Avoid except in cardiac arrest (due to extravasation risk).
88Insulin regimen to shift K intracellularly
Regular insulin 10 units IV, with 25 g dextrose (omit dextrose if BG >250).
89Sodium bicarbonate dose for hyperkalemia shifting
50-100 mEq IV, especially if acidemic.
90Albuterol dose for hyperkalemia shifting
10-20 mg nebulized over 10 minutes.
91Therapies that eliminate potassium in hyperkalemia
Loop diuretics, sodium zirconium cyclosilicate (SZC), and hemodialysis.
92Sodium zirconium cyclosilicate (SZC) acute dose
10 g PO every 8 hours for up to 48 hours.
93Most effective and predictable way to eliminate potassium
Hemodialysis.
94When is hemodialysis reserved for hyperkalemia?
Life-threatening hyperkalemia or patients already receiving dialysis.
95Normal serum magnesium range
1.8-2.4 mg/dL.
96Percentage of serum magnesium that is protein-bound
About 30%.
97Empiric ICU serum magnesium target
Serum magnesium >2 mg/dL.
98Effect of hypoalbuminemia on serum magnesium
It may slightly falsely lower measured serum magnesium.
99Signs and symptoms of hypomagnesemia
Weakness, cramping, paresthesias, Chvostek/Trousseau signs, tetany, QT prolongation, hypokalemia, hypocalcemia.
100Expected magnesium deficit when serum Mg is <1.5 mg/dL (1.3 mEq/L)
About 1-2 mEq/kg deficit.
101Coexisting hypokalemia and hypomagnesemia treatment order
Treat magnesium concurrently with or before potassium.
102Duration of IV therapy for successful hypomagnesemia repletion
Usually 4-5 days of IV therapy.
103Why avoid intramuscular magnesium replacement?
Dose volume limits and tissue irritation.
104Empiric Mg sulfate dose for Mg 1.6-1.8 mg/dL
0.05 g/kg IV.
105Empiric Mg sulfate dose for Mg 1.0-1.5 mg/dL
0.1 g/kg IV.
106Empiric Mg sulfate dose for Mg <1.0 mg/dL
0.15 g/kg IV.
107Ordering increments for IV magnesium sulfate
2-g increments for ease of preparation.
108Maximum IV magnesium sulfate infusion rate
No faster than 1 g/hour (8 mEq/hour).
109Maximum IV magnesium sulfate ceiling per administration
8-10 g per administration.
110How long serum Mg remains elevated after infusion
Several hours; full redistribution takes about 48 hours.
111When is oral magnesium reasonable in the ICU?
Asymptomatic patients tolerating oral intake with Mg ≥1 mg/dL.
112Why is oral magnesium difficult for ICU repletion?
GI side effects (diarrhea) and the high elemental doses needed.
113Oral magnesium salt with highest percent elemental magnesium
Magnesium oxide (~60% elemental magnesium).
114mag carbonate % elemental
45%
115Definition of hypermagnesemia
Serum Mg >2.4 mg/dL.
116Threshold for manifestations of hypermagnesemia
Usually when serum Mg >4 mg/dL.
117Signs and symptoms of hypermagnesemia
Hypotension, decreased deep tendon reflexes, bradycardia, somnolence, paralysis, arrhythmias.
118Initial treatment for severe symptomatic hypermagnesemia
Remove Mg source and give slow calcium gluconate 2 g over 5-10 min. until severe symtpoms resolves transient may need to redose
119renal fx and mag admin
give half the dose
120Supportive/elimination therapies for hypermagnesemia
Ventilation if needed, 0.9% NaCl plus loop diuretic, or hemodialysis.
121Normal total serum calcium range
8.5-10.5 mg/dL.
122Normal ionized calcium range
1.12-1.32 mmol/L.
123effects on calcium
ph increase, decrease ca decreased albumin, decreased ca increased phos, decreased ca
124What total calcium <7 mg/dL usually indicates
Most of these patients are truly hypocalcemic by ionized calcium.
125IV calcium requirement in PN
10-15 mEq/day.
126Oral calcium requirement range
1-3 g/day.
127How hypomagnesemia causes hypocalcemia
It causes PTH resistance and may impair PTH secretion.
128Timeframe for hypocalcemia improvement after correcting Mg
Within about 2 days.
129Definition of hypocalcemia
Ionized calcium <1.12 mmol/L.
130Signs and symptoms of hypocalcemia
Tingling, paresthesias, hyperactive deep tnedon reflexes, tetany, Chvostek/Trousseau signs, prolonged QT, seizures
131Electrolyte disorders causing hypocalcemia
Hypomagnesemia and hyperphosphatemia.
132IV calcium regimen for ionized Ca 1.0-1.12 mmol/L
Calcium gluconate 2 g in 100 mL over 2 hours.
133IV calcium regimen for ionized Ca ≤0.99 mmol/L
Calcium gluconate 4 g in 100-250 mL over 4 hours.
134Preferred IV calcium salt for routine repletion
Calcium gluconate (calcium chloride has ~2.5x more elemental Ca; extravasation risk).
135When to recheck ionized calcium after IV infusion
Several hours after completion to allow equilibration.
136When to consider continuous calcium infusion
Severe/persistent hypocalcemia (e.g., CRRT or massive transfusion with citrate toxicity).
137Definition of hypercalcemia
Corrected total Ca >10.5 mg/dL or ionized Ca >1.32 mmol/L.
138Threshold where hypercalcemia symptoms become evident
Total Ca ≥12 mg/dL or ionized Ca ≥1.5 mmol/L.
139Signs and symptoms of hypercalcemia
Mental status changes, polyuria, shortened QT interval, bradycardia, and AV block.
140First-line supportive treatment for hypercalcemia when dehydrated
mobilize patient 0.9% NaCl at 200-300 mL/hour x48 hours or until rehydrated (± furosemide 40-80 IV every 12 hours).
141Calcitonin dose for hypercalcemia
4 units/kg IM or SC q12h; may increase to 8 units/kg q8h.
142Calcitonin limitations in hypercalcemia
Rapid onset within hours, but tachyphylaxis occurs within days; limit to 24-72 h.
143When is denosumab preferred for hypercalcemia?
Bisphosphonate-refractory hypercalcemia or poor kidney function.
144Denosumab dose in renal disease / bisphosphonate-naive moderate hypercalcemia
60 mg or 0.3 mg/kg subcutaneously once. prescence of kidney dysfunction increases the risk of hypocalcemia
145Denosumab regimen for severe/persistent hypercalcemia
Up to 120 mg weekly for 3 weeks, then 120 mg every 4 weeks.
146Steroid regimen for granulomatous disease-related hypercalcemia
Prednisone ≥40 mg/day for 10 days. (TB, saarcodoiss)
147When is hemodialysis necessary for hypercalcemia?
Severe hypercalcemia (e.g., serum calcium >3 mmol/L).
148Normal serum phosphorus range
2.5-4.5 mg/dL.
149Effect of alkalemia on serum phosphorus
Alkalemia can decrease serum phosphorus.
150Definition of hypophosphatemia
Serum phosphorus <2.5-3 mg/dL.
151Definition of severe hypophosphatemia
Serum phosphorus <1 mg/dL.
152Mild/moderate symptoms of hypophosphatemia
Weakness and paresthesias.
153Severe complications of hypophosphatemia
Cardiomyopathy, cardiac arrest, seizures, respiratory arrest (diaphragm weakness), rhabdomyolysis.
154ICU ventilator-dependent phosphorus target
About 4 mg/dL.
155IV phosphorus dose for Phos 2.3-3 mg/dL (general ICU)
0.16 mmol/kg.
156IV phosphorus dose for Phos 1.6-2.2 mg/dL (general ICU)
0.32 mmol/kg.
157IV phosphorus dose for Phos <1.6 mg/dL (general ICU)
0.64 mmol/kg.
158IV phosphorus dose for Phos 2.3-3 mg/dL (high-requirement)
0.32 mmol/kg.
159IV phosphorus dose for Phos 1.6-2.2 mg/dL (high-requirement)
0.64 mmol/kg.
160IV phosphorus dose for Phos <1.6 mg/dL (high-requirement)
1 mmol/kg.
161Maximum IV phosphorus infusion rate
No faster than 7.5 mmol/hour.
162Prescribing units for phosphorus
Millimoles (ideally divisible by 3 mmol).
163When to use potassium phosphate instead of sodium phosphate
When serum K is <4 mEq/L and K content won't exceed repletion needs.
164Potassium content of potassium phosphate products
3 mmol of phosphorus contains about 4.4 mEq potassium.
165When to use sodium phosphate instead of potassium phosphate
When serum K is ≥4 mEq/L or potassium load would exceed needs.
166Sodium content of sodium phosphate
3 mmol of phosphorus contains about 4 mEq sodium.
167High-requirement populations for phosphorus repletion
Thermal injury, trauma/TBI, significant refeeding, and hepatic resection.
168Why avoid oral phosphorus for severe hypophosphatemia?
Need for rapid correction and high risk of diarrhea at high oral doses.
169Definition of hyperphosphatemia
Serum phosphorus >5 mg/dL (clinically relevant >6 mg/dL).
170Signs of hyperphosphatemia
hypocalcemia and metastatic calcifications (Neuromuscular irritability, prolonged QT, and tetany)
171Calcium-phosphorus product associated with calcification
Usually when Ca × Phos product approaches ≥55 mg/dL.
172How to reduce phosphorus intake in PN
Omit phosphorus from PN; consider reducing lipid (ILE) content if a high fat formulation
173How to reduce phosphorus intake in EN
Change to a low- or no-electrolyte renal enteral formula.
174Timing of phosphate binders
With meals for oral diets, or at regular intervals during EN.
175Phosphate binders to avoid in hypercalcemia
Calcium carbonate and calcium acetate.
176Why sevelamer carbonate powder is preferred for EN in renal failure
Easier to give enterally; less likely to worsen metabolic acidosis than HCl tablets.
177Common initial dose of sevelamer
800-1600 mg three times daily.
178Common initial dose of calcium acetate
1334-2001 mg three times daily.
179Common initial dose of lanthanum
500 mg three times daily.
180Phosphate binders that may increase iron concentrations
Ferric citrate and sucroferric oxyhydroxide.