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Dialysis/Artificial Kidney

Is a procedure in which principles of diffusion are applied for the treatment of renal failure?

Types

  • Hemo dialysis
  • Peritonial dialysis

Hemo Dialysis

Solution is prepared in which

  • Waste products are absent
  • Electrolytes are adjusted
  • Nutrients are provided

Solution is separated from patient՚s blood by a dialyzing membrane.

Blood is normalised by the process of diffusion.

Hemo Dialysis
Dialyzer for Hemo Dialysis

Peritoneal Dialysis

  • In it diffusion takes place across the patient՚s own peritoneal membrane
  • About 1 L of sol. is introduced in peritoneal cavity
  • Kept for 20 to 60 min & replaced by fresh fluid
Peritoneal Dialysis

Peritoneal Dialysis

  • Indications
  • In acute renal failure, most of the time condition is reversible. Dialysis can support the patient for a few weeks during the period of crisis
  • In patient of chronic renal failure it is life saving
  • Permanent sol. is Renal Transplantation

Renal Transplantation

  • Were among the first transplants to be done and are among the most successful transplants
  • Both cadavar & live donors are used
  • Detailed antigen typing of both is done
  • Immuno suppression is required
  • Occasionally a graft is rejected

PH Expression

  • H + concentration is very low & their expression is very cumbersome
  • It is customary to express them on a logarithm scale

Normal H + is 40 nEq/L (0.00000004 Eq. /L. & the Ph. Is)

PH of Body

  • pH is – ve log. of concentration
  • Normal concen. in body fluids
  • Normal variation
  • Concen. is maintained in a very narrow range

PH of Some Body Fluids

  • Plasma pH
    • Arterial … 7.4
    • Venous … 7.35
  • Extra cellular fluid … 7.35 to 7.45
  • Intra cellular fluid … 6 to 7.4
  • Urine … 6 (4.5 to 8)
  • Gastric HCl … 0.8

PH

  • pH compatible with life 6.8 to 8.0 & person can live for few hours.
  • Daily H + production or ingestion about 80 mEq
  • These excess of ions must be removed

Acid Produced in Body

  • Acids produced in body
    • Volatile acids
    • Nonvolatile acids

Volatile Acids

  • a major end product of metabolism
  • Removed by lungs as
  • It accounts for about

Nonvolatile/Fixed Acids

  • Sulphuric acid — end product of sulpher containing aminoacids eg. Cystenine, methionine metabolism
  • Phosphoric acid — end product of phospholipid metabolism
  • Hydrochloric acid — end product of lysine, arginine & histidine mata.

Fixed Acids

  • Organic Acids
    • Lactic acid … severe anemia
    • Acetoacetic acid, hydroxy butyric acid … uncontrolled D. M.
    • Uric acid … metabolism of nucleoproteins

Base Production

  • Negligible amount
  • Bicarbonate … metabolism of organic anions eg. Citrates
  • Ammonia … from metabolism of amino acids is converted to urea, so not important

Buffering of H + Ions

  • Any substance that can reversibly bind H + ions is buffer
  • Reaction can go in both directions

Regul. Of pH

  • Body Buffers — 3 Systems
    • Chemical Buffers … come into action with in fraction of seconds. They keep ions tied up
    • Respiratory System … acts with in minutes Renal System … acts over a period of hours to days. Most efficient

Chemical Buffers

  • Forms I line of defence
  • Three types
    • Bicarbonate buffers
    • Phosphate buffers
    • Protein buffers

Bicarbonate Buffer

  • Has two components
    • Weak Acid
    • A salt with strong Base

When a strong acid is added. Like

  • A strong acid is converted to a weak acid
  • If a strong base is added, NaOH
  • Weak base is formed
  • Thus change in pH is minimized

Quantitative Dynamics

  • BICARBONATE BUFFER
  • is ionized
  • It՚s dissociation constant is (1)
  • The amount of free is (2)
  • cannot be measured but is proportionate to (3)
  • The solubility coefficient for is 0.03 mmol/mm Hg at body temp.
  • Therefore, equation 3 can be written as (4)
  • concentration is expressed as pH units
  • ions
  • Similarly dissociation constant can be expressed as
  • Thus (5)
  • therefore (6)
  • If we change the sign
    • (7)
    • (8)

Bicarbonate Buffer System Titration Curve

Bicarbonate Buffer System Titration Curve

Handerson-Hasselbalch Eq

Phosphate Buffer

  • Two components are
  • important buffer in
  • Renal tubules &
  • Intracellular fluid (high concentration)

Protein Buffer

  • Have
    • Free carboxyl group
    • Free amino gp.
  • Important intracellular buffer

PK of Some Buffer Systems

  • Bicarbonate System … 6.1
  • Dibasic System … 6.8
  • Proteins …
  • Ammonia … 9.0
  • Effective buffers are those with pKs close to the pH. of fluid in which they are operating

Principal Buffers in the Body Fluids

  • 1 Whole blood
    • Hemoglobin
    • Proteins
    • Bicarbonates
  • 2 Intrestitial fluid … Bicarbonate
  • 3 Intracellular fluid
    • Proteins
    • phosphates

Respiratory System

  • II line defense
  • Hyperventilation … Alkalosis
  • Hypoventilation … Acidosis
  • Effect is mediated by change in CO2 concen.

Renal System

  • III line defense
  • Acts by
    • Reabsorption of bicarbonates
    • Generation of new bicarbonates
    • H + excretion

Disorders of Acid-Base Balance

  • Simple
    • Metabolic Acidosis
    • Metabolic Alkalosis
    • Respiratory Acidosis
    • Respiratory Alkalosis

Mixed Disorders

  • Metabolic Acidosis & Resp. Acidosis
  • “& Res. Alkalosis”
  • Metabolic Alkalosis & Res. Alkalosis
  • “& Res. Acidosis”
Mixed Disorders

Anion Gap

  • The concentration of anions & cations must be equal in plasma, so there is no real gap
  • We measure only some anions & cations
  • The anion gap is a diagnostics concept

Anion Gap

  • Is the difference between unmeasured anions & unmeasured cations
  • Normal range is

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