Phosphates and Lactate (FSKP) Flashcards
% phosphate in bone, in soft tissues and in serum/plasma (active form)
80% in bone, 20% in soft tissues, <1% in serum/plasma
Predominant intracellular anion
Phosphate
Concentration of phosphate in blood
12 mg/dL (3.9 mmol/L)
Concentration of inorganic phosphates in blood
3-4 mg/dL
complex phosphodiesters
DNA and RNA
Coenzymes of phosphates
Esters of phosphoric or pyrophosphoric acid
Reservoirs of energy (phosphate)
ATP, creatine phosphate and phosphoenolpyruvate
Facilitates release of O2
2,3-biphosphoglycerate (2,3-BPG) in RBcs
-Acts to increase Phosphate in the blood
Vitamin D (increased)
-Increases both phosphate absorption in the intestine and phosphate reabsorption in the kidney
Vitamin D (increased)
In excessive secretion or administration of this, phosphate in the blood may increase because of decreased renal excretion
Growth hormone (increased)
Decreases phosphate by inhibiting reabsorption
PTH and calcitonin
60-80% of patients in ICU with hypophosphatemia has
Sepsis
Causes of hypophosphatemia
- increased renal excretion
- hyperparathyroidism
- decreased intestinal absorption, as w/ vit. D deficiency or antacid use
Mortality rate of mild hypophosphatemia
15%
Mortality rate of severe hypophosphatemia
<1.0 g/dL or 0.3 mmol/L
30%
Causes of hyperphosphatemia
- increased intake of phosphate (neonates)
- increased breakdown of cells
- lymphoblastic leukemia
Specimen for determination of inorganic phosphate
Serum or Li heparin plasma, urine (24hr)
Sources of error of inorganic phosphate
- oxalate, citrate, or EDTA: interfere
- hemolysis: high conc. inside RBCs
- Circadian rhythm: highest in late morning and lowest in the evening
Methods (phosphate)
Colorimetry
1. Fiske Subbarow 2. Gomori Modification
Formation of an ammonium phosphomolybdate complex (colorless)
Colorimetry
Colorimetry is read by
UV absorption at 340 nm or reduced to form molybdenum blue read at 500-700 nm
Specimen of this method is precipitated with TCA
Fiske Subbarow
This method uses Molybdenum reagent to form heteromolybdenum complex or phosphomolybdate complex
Gomori Modification
Reference range of serum/plasma for phosphate in neonates
1.45-2.91 mmol/L (4.5-9.0 mg/dL)
Reference range of serum/plasma for phosphate in child
1.45-1.78 mmol/L (4.5-5.5 mg/dL)
Reference range of serum/plasma for phosphate in adults
0.87-1.45 mmol/L (2.7-4.5 mg/dL)
Reference range of 24 hr urine for phosphate
13-42 mmol/day (0.4-1.3 g/day)
By-product of an emergency mechanism producing a small amount of ATP when O2 delivery is severely diminished
Lactate
The normal end product of glucose metabolism (glycolysis)
Pyruvate
Conversion of pyruvate to lactate is activated when
A deficiency of oxygen leads to an accumulation of excess NADH
Associated with hypoxic conditions (shock, myocardial infarction, severe blood loss)
Type A lactic acidosis
Metabolic origin (diabetes mellitus, severe infection, leukemia, liver or renal disease, and toxins [ethanol, methanol, salicylate poisoning])
Type B lactic acidosis
Specimen for determination of lactate
- tourniquet should not be used: venous stasis will increase lactate levels
- do not exercise the hand
- anaerobic glycolysis should be prevented
- heparinized blood may be used: must be delivered on ice and plasma must be quickly separated
- use iodoacetate or fluoride to inhibit glycolysis w/o affecting coag
Methods (lactate)
Monitoring oxygenation Enzymatic method (coupled)
Enzymatic method (coupled)
Lactae + oxygen (acted by the enzyme: lactate oxidase)—-> pyruvate + hydrogen peroxide (H2O2)
Hydogen peroxide + H donor + chromogen (acted by the enzyme: peroxidase) —-> colored dye + 2 water (H2O)
Reference Range of lactate (venous)
0.5-2.2 mmol/L (4.5-19.8 mg/dL)
Reference range of lactate (arterial)
0.5-1.6 mmol/L (4.5-14.4 mg/dL)
Reference range of lactate (CSF)
1.1-2.4 mmol/L (10-22 mg/dL)
Monitoring oxygenation
- in dwelling catethers that measure blood flow
- pulse oximeters
- base-excess determination
- measurements of oxygen consumption (VO2)
