PreWork
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PreWork Objectives



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
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
 HCl
 etc.
Getting Rid of Acid
Bicarbonate Reabsorption by the
Kidneys (Metabolic)
Blood
Carbonic Anhydrase
HCO3-
H2CO3
Urine
H+
Getting Rid of Acid
The Lungs Eliminate CO2
(Respiratory)
HCO3-
+ H+
Acidic
H2CO3
Carbonic Acid
H2O + CO2
Getting Rid of Acid
The Lungs Eliminate CO2
(Respiratory)
HCO3Acid
+ H+
H2CO3
H2O + CO2
Carbonic Acid
pH
Alveoli
Normals
 Arterial
Blood
 pH:
7.35-7.45
 pCO2: 40
 PO2: 100
 HCO3 25
Normals
 Venous
Lytes
 Sodium:
140
 Potassium: 4.5
 Chloride
100
 Total CO2
26
Total CO2
pCO2 =40mm Hg
Dissolved
in/ L
Water
…..
 40mm

1.2
HgmEq
EQUALS
dissolved
+
CO2
25 mEq /L of HCO3
 =26
mEq / L = Total CO2
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Sodium and Water Prework
Volume and Tonicity
Salt rules volume
Salt
Rules
Volume
This represents normal sodium
and volume. Extracellular
space is the vascular plus tissue
Note that intracelluar
space is 2/3 of total
body water
Intracellular
Serum
Sodium
140 mEq/L
(Unchanged)
Serum
Sodium
140 mEq/L
Extracellular
Intracellular
Free Water Rules Serum
Sodium
This represents normal sodium
and volume. Extracellular
space is the vascular plus tissue
Note that intracelluar
space is 2/3 of total
body water
Intracellular
Serum
Serum
Sodium
Sodium
125
mEq/L
140 mEq/L
(hyponatremia)
Extracellular
No Clinically
Significant Volume
Change
(Water Spreads Out)
Intracellular
The Challenge
 Figure
out how the ReninAngiotensin-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


Vitamin D


serum calcium
Calcitonin


serum calcium
serum calcium
Calcium homeostasis figure (next
slide)
http://www.biol.andrews.edu/fb/spring/Chap.45-%20Endocrinology/4510.jpg
Corrected Calcium

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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/dL
 Pathophysiology

Hypoparathyroidism
 Vitamin D deficiency
 Hypomagnesemia
o
 Hyperphosphatemia, 2 hypoparathyroidism
 Medications/chelating agents

 Bisphosphonates,
phenytoin
loop diuretics, calcitonin,
Hypocalcemia
 Clinical
Presentation
 Acute
 Fatigue,
irritability, confusion, seizures
 Muscle cramps, spasms, tetany
 Chronic
 Prolonged
QT interval
 Brittle nails, hair loss
Hypocalcemia Treatment
Always correct calcium for albumin!!
 Depends on acuity and severity
 Check a magnesium level (find out
why for the exam! )
 Calcium supplementation

 IV
 PO
IV Calcium
Acute symptomatic patients
 Calcium 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 patients
 Corrected symptomatic patients
 1-3 g/day of elemental calcium ±
vitamin D
 Take with meals,
in divided doses for
best absorption

PO Calcium
Calcium Salt
Carbonate
(Tums®,
OsCal®,
VIACTIV®)
Acetate
(PhosLo®)
used as a phosphate binder
Citrate
(Citracal®) Important: Use when
patient has little stomach acid (PPI)
Elemental
Calcium
40%
25%
21%
Hypocalcemia Monitoring
 Albumin,
magnesium levels
 Symptomatic 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
Ca2+ > 10.5 mg/dL
 Pathophysiology
 Serum
 Primary
hyperparathyroidism**
 Malignancy**
 Other
 High
bone turnover, sarcoidosis
 Medications (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
Onset
0.9% NS (plus
200-300 cc/hr
furosemide below)
* First line therapy
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
Ca2+ q 6-12 hrs if symptomatic
 Serum Ca2+ daily if mild-moderate
 Serum
Summary of Calcium
 Calcium
regulation
 PTH,
Vitamin D, calcitonin
 Corrected calcium
 Oral
calcium products
 Treatment of hypercalcemia
Phosphorus
Phosphorus
 Normal
value 2.7-4.5 mg/dL
 Function
 Phospholipid
membrane
 Supports bone and teeth
 Metabolism of nutrients
 Source of ATP (energy, kinda critical)
Phosphorus
 Source
 Meats,
dairy, eggs
 Regulation
 Kidney
Hypophosphatemia
Mild to Moderate 1-2 mg/dL
 Severe < 1 mg/dL
 Pathophysiology

 Decreased
 Vitamin
intake/absorption
D deficiency, phosphate binders
 Increased
 Diuretics,
excretion
hyperparathyroidism
 Intracellular
 Parenteral
shift
nutrition, insulin
Hypophosphatemia
 Clinical
Presentation
– irritability, weakness,
seizures
 Muscular – myalgia
 Hematologic – hemolysis
 Pulmonary – respiratory distress
 Other – osteomalacia, arrhythmias
 Neuro
Hypophosphatemia Tx
 Mild
– moderate
 PO
 50-60
mmol/day divided in 3-4 doses
Neutra-Phos 1-2 packets QID mixed in 2.5 oz
water or juice
o K-Phos Neutral 1-2 tabs QID with water
o
 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 IV
 Repeat 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*
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!
Typically used as laxative
*Oral agents
Hypophosphatemia

Monitoring
 IV
therapy
 Serum
 PO
phosphorus every 6 hrs
therapy
 Serum
 Renal
phosphorus daily
function, BP (IV)
 Adverse events – diarrhea (PO), soft
tissue calcification, hypocalcemia,
hypotension (IV)
Hyperphosphatemia
Serum phos > 4.5 mg/dL
 Pathophysiology

 Decreased
 Renal
urinary excretion
failure, hypoparathyroidism
 Increased
intake
 Parenteral
nutrition, phosphate enemas
 Extracellular
 Acidosis
shift
Hyperphosphatemia
 Clinical
Presentation
 N/V,
muscle pain/weakness,
hyperreflexia, tetany
 Soft Tissue calcification
 Due
to calcium-phosphate product
 Goal is less than 55.
Hyperphosphatemia Tx
Restrict dairy products
 Phosphate binders

 Aluminum
and magnesium-based
antacids
 No
longer first line, avoid in renal failure
 Calcium
(Drug of first choice unless
Calcium is high)
 Sevelamer
 Binding
resin Usually given with meals
Hyperphosphatemia
 Monitoring
 Serum
calcium level
 Serum phosphorus level daily
 Renal function
Summary of Phosphorus
 IV
vs. PO replacement
 Give
IV phosphorus when severe
hypophosphatemia
 Medications
affecting serum
levels
 Phosphate-binders,
calcium,
diuretics, insulin, vitamin D