PreWork

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PreWork Objectives

Understand the respiratory and metabolic mechanism for eliminating acid

Know the normals for Arterial Blood Gasses and Venous Electrolytes

Explain ADH and Aldosterone effects on sodium and water.

Explain the effects of sodium and free water on volume and serum sodium

Explain hormonal regulation of Ca++ and P04

Problem: Metabolism Produces Acid

H2SO4

H3PO4

HCletc.

Getting Rid of Acid

Bicarbonate Reabsorption by the Kidneys (Metabolic)

Carbonic AnhydraseCarbonic Anhydrase HH22COCO33

UrineUrine

BloodBloodHCOHCO33

--

HH++

The Lungs Eliminate CO2 (Respiratory)

Getting Rid of Acid

HH22COCO33HCOHCO33-- HH++ HH22O + COO + CO22++

AcidicAcidicCarbonic AcidCarbonic Acid

The Lungs Eliminate CO2 (Respiratory)

Getting Rid of Acid

HH22COCO33HCOHCO33-- HH++ HH22O + COO + CO22++

AcidAcid

pHpH

Carbonic AcidCarbonic Acid

AlveoliAlveoli

NormalsArterial BloodpH:7.35-7.45pCO2: 40

PO2: 100

HCO3 25

NormalsVenous LytesSodium: 140Potassium: 4.5Chloride 100Total CO2 26

Total CO2

pCO2 =40mm Hg

40mm Hg EQUALS 1.2 mEq / L dissolved CO2

+ 25 mEq /L of HCO3

=26 mEq / L = Total CO2

Dissolved in Water…..

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Sodium and Water Prework

Volume and Tonicity

Salt rules volume

Intracellular IntracellularExtracellular

H20H2

0

Serum Sodium

140 mEq/L(Unchanged)

Serum Sodium

140 mEq/L

This represents normal sodium and volume. Extracellular

space is the vascular plus tissue

Note that intracelluar space is 2/3 of total

body water

Salt Rules

Volume

Free Water Rules Serum Sodium

Intracellular IntracellularExtracellular

Serum Sodium 125 mEq/L

(hyponatremia)

Serum Sodium

140 mEq/L

This represents normal sodium and volume. Extracellular

space is the vascular plus tissue

Note that intracelluar space is 2/3 of total

body water

H20 H

20

No Clinically Significant Volume

Change

(Water Spreads Out)

H20H2

0

The Challenge

Figure out how the Renin-Angiotensin-Aldosterone system and how ADH relate to the above examples of sodium and water. What turns them on and what turns them off.

Calcium And Phosphate Prework

Prework questions on Calcium and Phosphate will be easy. Exam questions will be slightly less easy.

Calcium

Calcium

Normal value: Total: 8.5–10.5 mg/dL (2.1–2.7 mmol/L) Ionized (free): 4.6–5.2 mg/dL (1.15–1.38 mmol/L)

Function Bone and teeth Neuromuscular activity (SA node, AV node) Endocrine/exocrine function Platelet function Muscle cell contraction

Calcium Regulation

PTH serum calcium

Vitamin D serum calcium

Calcitonin serum calcium

Calcium homeostasis figure (next slide)

http://www.biol.andrews.edu/fb/spring/Chap.45-%20Endocrinology/4510.jpg

Corrected Calcium

Only ionized (unbound) calcium is active Calcium must be corrected when there is a

low albumin (a larger percent is ionized) For each 1mg/dl change in albumin from

normal, 0.8mg/dl change in Ca2+

[(4 – alb) x 0.8] + serum Ca2+

Ex. Alb 2.3 Ca2+ 7.6 Corrected calcium = [(4-2.3) x 0.8] + 7.6 = 8.96 mg/dL

Hypocalcemia

Serum Ca2+ < 8.5 mg/dLPathophysiology

Hypoparathyroidism Vitamin D deficiency Hypomagnesemia Hyperphosphatemia, 2o hypoparathyroidism Medications/chelating agents

Bisphosphonates, loop diuretics, calcitonin, phenytoin

Hypocalcemia

Clinical PresentationAcute

Fatigue, irritability, confusion, seizuresMuscle cramps, spasms, tetany

ChronicProlonged QT intervalBrittle nails, hair loss

Hypocalcemia Treatment

Always correct calcium for albumin!!Depends on acuity and severityCheck a magnesium level (find out

why for the exam! )Calcium supplementation

IV PO

IV Calcium

Acute symptomatic patientsCalcium chloride

1 gm IV (27% elemental) Very irritating to veins

Calcium gluconate 2-3 gm IV (9% elemental) availability in liver disease

PO Calcium

Chronic asymptomatic patientsCorrected symptomatic patients1-3 g/day of elemental calcium ±

vitamin DTake with meals, in divided doses for best absorption

PO Calcium

Calcium SaltElemental Calcium

Carbonate (Tums®, OsCal®, VIACTIV®)

40%

Acetate (PhosLo®) used as a phosphate binder

25%

Citrate

(Citracal®) Important: Use when patient has little stomach acid (PPI)

21%

Hypocalcemia Monitoring

Albumin, magnesium levelsSymptomatic patient

Serum and ionized calcium levels every 4-6 hrs after IV calcium

Serum calcium every 24-48 hrs during oral therapy, then 1-2 times weekly

Hypercalcemia

Serum Ca2+ > 10.5 mg/dLPathophysiology

Primary hyperparathyroidism**Malignancy**Other

High bone turnover, sarcoidosisMedications (thiazides, lithium, vitamin D)

Hypercalcemia

Clinical Presentation Depends on degree and onset GI – N/V, anorexia, constipation CV – short QT, prolonged PR & QRS Neuro – fatigue, weakness, confusion Renal – polyuria, nocturia, nephrolithiasis

Hypercalcemia Treatment

Drug Dose Onset0.9% NS (plus furosemide below) * First line therapy

200-300 cc/hr 24-48 hrs

Furosemide 40-80 mg IV q 1-4 hrs Upon diuresis

Calcitonin 4 units/kg SC or IM q 12 hrs 1-2 hrs

Bisphosphonates Pamidronate 30-90 mg IV over 2-24 hrs

1-2 days

Prednisone 40-60 mg/day 1-2 weeks

Hypercalcemia Treatment

Other treatment options Gallium nitrate, mithramycin

Monitoring Albumin ECG Serum Ca2+ q 6-12 hrs if symptomatic Serum Ca2+ daily if mild-moderate

Summary of Calcium

Calcium regulationPTH, Vitamin D, calcitoninCorrected calcium

Oral calcium productsTreatment of hypercalcemia

Phosphorus

Phosphorus

Normal value 2.7-4.5 mg/dLFunction

Phospholipid membraneSupports bone and teethMetabolism of nutrientsSource of ATP (energy, kinda critical)

Phosphorus

SourceMeats, dairy, eggs

RegulationKidney

Hypophosphatemia

Mild to Moderate 1-2 mg/dLSevere < 1 mg/dLPathophysiology

Decreased intake/absorptionVitamin D deficiency, phosphate binders

Increased excretionDiuretics, hyperparathyroidism

Intracellular shiftParenteral nutrition, insulin

Hypophosphatemia

Clinical PresentationNeuro – irritability, weakness,

seizuresMuscular – myalgiaHematologic – hemolysisPulmonary – respiratory distressOther – osteomalacia, arrhythmias

Hypophosphatemia Tx

Mild – moderate PO

50-60 mmol/day divided in 3-4 doseso Neutra-Phos 1-2 packets QID mixed in 2.5 oz

water or juiceo K-Phos Neutral 1-2 tabs QID with water

NOTE: Dose in mmol NOT mEq

Hypophosphatemia Tx

Mild – moderate IV

0.08-0.15 mmol/kg IV Repeat until serum phosphorus > 2

mg/dL

Hypophosphatemia Tx

Severe IV

0.25-0.5 mmol/kg IVRepeat until serum phosphorus > 2

mg/dL

Phosphorus Replacement

Product Phos Content Na Content K Content

K-Phos Neutral* 250mg 8 mmol 13 mEq 1.1 mEq

Fleet Phospho-soda*Typically used as laxative

20 mmol 24 mEq 0

Sodium Phosphate 3 mmol/mL 4 mEq/mL 0

K-Phos Original Dissolving Tablets

3.6 0 3.7mEq

Neutra-Phos* 250mg Recently discontinued

Doesn’t matter!

Neutra-Phos K* 250mg Recently discontinued

Doesn’t matter!*Oral agents

Hypophosphatemia

Monitoring IV therapy

Serum phosphorus every 6 hrs PO therapy

Serum phosphorus daily Renal function, BP (IV) Adverse events – diarrhea (PO), soft tissue

calcification, hypocalcemia, hypotension (IV)

Hyperphosphatemia

Serum phos > 4.5 mg/dLPathophysiology

Decreased urinary excretionRenal failure, hypoparathyroidism

Increased intakeParenteral nutrition, phosphate enemas

Extracellular shiftAcidosis

Hyperphosphatemia

Clinical PresentationN/V, muscle pain/weakness,

hyperreflexia, tetanySoft Tissue calcification

Due to calcium-phosphate productGoal is less than 55.

Hyperphosphatemia Tx

Restrict dairy productsPhosphate binders

Aluminum and magnesium-based antacidsNo longer first line, avoid in renal failure

Calcium (Drug of first choice unless Calcium is high)

SevelamerBinding resin Usually given with meals

Hyperphosphatemia

MonitoringSerum calcium levelSerum phosphorus level dailyRenal function

Summary of Phosphorus

IV vs. PO replacementGive IV phosphorus when severe

hypophosphatemiaMedications affecting serum

levelsPhosphate-binders, calcium,

diuretics, insulin, vitamin D