Can Bang Toan Kiem 2

CN BNG ACID- BASE

PGS Nguyn th an Hng

pH? Nanoequivalent [H+] so vi milliequivalent

concentrations ca cc cht in gii khc (Na+, K+, Cl-, HCO3-) trong dch c th.

Nanoequivalent = one thousand-millionths ca 1 gram equivalent

ECF [H+] bnh thng l 40 nEq/L hay l 0.00004 mEq/L so vi [K+] l 4.0 mEq/L

Trng lng phn t Mo

Gram Equivalent ,E = =

Ha tr x

CN BNG ACID-BASE

pH = -log10[H+] = log10(1/[H+])

[H+] = 40 nEq/L = 4 x 10-8 Eq/L

pH = -log10(4 x 10-8) = 7.4

pH bnh thng = 7.37-7.42 v gii hn cao nht ph hp vi s sng l 6.8 n 8.0

CN BNG ACID-BASE

HA H+ + A-

Acid = Cho Proton (HA)

Base = Nhn Proton (A-)

Phng trnh Henderson- Hasselbach

[A-]

pH = pK + log

[HA]

CN BNG ACID-BASE: Chuyn ha hng ngy

Chuyn ha cc acid amin c cha sulfur-trong protein cho ra acid sulfuric v chuyn ha phospholipids cho ra acid phosphoric : 40-80 mEq/ngy l acid c nh hay khng bay hi

Chuyn ha ng v m cho ra 15,000-20,000 mMol CO2 hay l acid bay hi

CN BNG ACID-BASE

Ti sao CO2 l mt acid ? (ti sao l cht cho H+?)

Men Carbonic anhydrase trong hng cu v trong TB ng thn xc tc phn ng

CO2 + H2O = H2CO3 Carbonic acid l cht cho proton :

H2CO3 = H+ + HCO3-

CN BNG ACID-BASE: Cht m (Buffers)

L cht c th nhn protons (H+ ) v lm gim s thay i pH

Mt dung dch acid yu v mui ca n

CN BNG ACID-BASE: Cht m (Buffers)

Hiu qu m ty thuc :

pH u th ca dch c th

Nng cht m trong dch c th

pKa ca cht m

Cc tnh hung c bit (t/d: bicarbonate l mt phn ca h thng m)

CC H THNG M Dch ngai bo (ECF)

Bicarbonate

Dch ni bo (ICF)

Phosphates

Proteins (t/d: Hb trong hng cu)

Carbonate trong xng

BICARBONATE

pKa l 1.3 n v di pH sinh l

Nng trong ECF cao (24 mEq/L)

Cn bng vi CO2

CO2 + H2O = H2CO3 = H+ + HCO3

-

PHOSPHATE

Quan trng trong ICF, nng cao (40 mEq/L)

Tng i khng quan trng trong ECF, nng thp (2 mEq/L)

Quan trng trong nc tiu (m bt acid) do pKa 6.8 ( pH ca dch ng thn xa = 6.0 to 7.0)

PROTEIN

Protein huyt tng gi vai tr m gii hn trong ECF

Protein trong t bo (c bit Hb trong HC) gi vai tr chnh trong m pH

CARBONATE TRONG XNG

C nng lc m d tr ln

Gi vai tr quan trng lu di trong p ng vi toan ha mn tnh

PHNG TRNH Henderson-Hasselbach

HA H+ + A- (v1 = k1[HA])

H+ + A- HA (v2 = k2[H+][A-])

mc cn bng : v1 = v2 k1[HA] = k2[H+][A-]

k1/k2 = Ka = [H+][A-]/[HA]

PT Henderson-Hasselbach

Ka = [H+][A-]/[HA]

pKa cng l mt i lng c trng cho mnh yu ca axit nh Ka . Dng pka chng ta khng phi ghi thm

s m vo , ta c pKa = -lgKa

pH = pKa + log([A-]/[HA])


Do H2CO3 /HCO3- l h m ch yu ca ECF , pH ca mu c tnh :

pH = pKa + log([HCO3-]/[H2CO3])

= 6,1 + log ([ HCO3-]/Pa CO2)

= 0.031 mM/L/mmHg P CO2 (hng s ch s ha tan ca CO2)

CO2 ha tan trong huyt tng c th to thnh H2CO3 :

pH = pKa + log([HCO3-]/[CO2 ha tan + H2CO3])


nhit v nng cht in gii ca ECF c 6,800 HCO3- v 340 phn t CO2 ha tan cho mi phn t H2CO3. Do , H2CO3 c th khng ng k.

CO2 ha tan lin quan n pCO2 qua h s ha tan :

CO2 ha tan = 0.03 x pCO2

PT Henderson-Hasselbach (dng lin quan n lm sng )

pH = pKa + log([HCO3-]/.03xpCO2)

pH = 6.1 + log([HCO3-]/.03xpCO2)

Cho thy pH l hm s ca t l gia bicarbonate v pCO2

CN BNG ACID-BASE : CON NG KHNG SINH L

Vic m l ha hc do cc h thng m trong ECF v ICF (giy)

Ri lan thng kh a n thay i pCO2 (giy n pht)

Thn ti iu chnh d tr HCO3- ca c th (gi n ngy)

pH = pKa + log(THN/PHI)

RI LAN CN BNG ACID-BASE NGUYN PHT

Ri lan chuyn ha

Toan chuyn ha

Kim chuyn ha

Ri lan h hp

Toan h hp

Kim h hp

RI LAN CN BNG ACID-BASE

Toan ha v kim ha

Acidosis - Alkalosis

So vi

Toan mu v kim mu

Acidemia - alkalemia

NHIM TOAN CHUYN HA Nhim toan chuyn ha xy ra khi lng acid khng bay hi

c to ra trong c th tng hay mt mt lng base , hoc s bi tit H+ ca thn gim

C ch b tr: tng [K+] ngai t bo

tng thng kh ---- gim PaCO2

thn tng thi H+, hp thu HCO3-

Nguyn nhn:

- Tng sn xut acid khng bay hi

- Mt bicarbonate : tiu chy, thuc c ch men anhydrase carbonic

- Gim thi acid : suy thn cp v mn

NHIM TOAN CHUYN HA Du hiu v triu chng

Nhp th Kussmaul

Gim sc co ca c tim, dn mch --- gim HA, suy tim

L ln, l m, hn m

Lang xng, lan dng xng

Cn lm sng : HCO3 gim, pH gim, PaCO2 gim, tng K+/mu

NHIM KIM CHUYN HA Do sn xut qu mc cht base hay mt acid khng bay hi

C ch b tr : Gim thng kh phi ---paCO2 tng, H2CO3 tng , pH tr li bnh thng

Thn tng thi HCO3-

Nguyn nhn:

- Mt H+ do thn

- Thuc li tiu, corticoid

- Tiu ha: nn i, tc rut cao

- Tng cht kim vo c th

NHIM KIM CHUYN HA Hi chng tetany : do gim ngng kch thch thn kinh-c

Co mch

Cn lm sng : HCO3 tng, pH tng, PCO2 tng , gim K+/mu

NHIM TOAN H HP L do lng CO2 tng c th cp hay mn

C ch b tr : CO2 tng ----- H2CO3 tng ----pH gim

H m ni bo c s dng : trao i H+ v K+ i vi Hb v cc protein khc trong ni bo

Trao i HCO3- /ni bo vi Cl-/ngai bo trong hng cu

Thn tng thi H+

Nguyn nhn : COPD- bnh phi lm gim thng kh

TT h hp b c ch (morphine)

Ri lan chc nng c-thn kinh (thuc dn c)

NHIM TOAN H HP Du hiu v triu chng :

- Thn kinh : ph thuc vo din tin : nhc u, l ln, l m, hn m, ph gai th

- Tun han : gim co c tim, dn mch

Cn lm sng : PO2/mu gim, HCO3- tng, pH gim, PCO2 tng

NHIM KIM H HP L tnh trng gim CO2 trong c th

C ch b tr:

- Trao i H+/ni bo vi K+/ngai bo

- Trao i Cl-/ni bo vi HCO3-/ngai bo

- Tng ly gii glucose to ra cc acid mnh (a.lactic, a.pyruvic)

- Thn: Gim tit H+

Nguyn nhn:

Tng thng kh

Kch thch trung tm h hp

Thiu oxy m

H hp h tr

NHIM KIM H HP Du hiu v triu chng

- Thn kinh : t tay chn, d cm, hi chng tetany

- Tng nhp th

- Cn lm sng : HCO3 gim, pH tng, PaCO2 gim

RI LAN CN BNG ACID-BASE : Nguyn tc phn tch

Mi ri lan nguyn pht (chuyn ha hoc h hp) theo sau l p ng th pht ca h thng cn li (h hp hoc chuyn ha )

pH s tr v gn nh bnh thng nhng khng han tan bnh thng

Hin tng n b qu mc khng xy ra


Ri lan pH [H+] Ri lan ban u

p ng th pht

Toan chuyn ha [HCO3-] pCO2

Kim chuyn ha [HCO3-] pCO2

Toan h hp pCO2 [HCO3-]

Kim h hp pCO2 [HCO3-]


Ri lan nguyn pht n gin v p ng (th pht) mong i thch ng

Hai ri lan nguyn pht hn hp xy ra cng lc trn cng mt ngi

Cn bit p ng n b trong trng hp c ri lan hn hp nh th

RI LAN CN BNG ACID-BASE Ri lan nguyn pht

p ng n b

Toan chuyn ha 0.7-1.2 mmHg pCO2 cho 1.0 mEq/L HCO3

-

Kim chuyn ha 0.7 mmHg pCO2 cho 1.0 mEq/L HCO3-

Toan h hp cp 0.15 mEq/L HCO3- cho 1.0 mmHg pCO2

Toan h hp mn 0.35 mEq/L HCO3- cho 1.0 mmHg pCO2

Kim h hp cp 0.25 mEq/L HCO3- cho 1.0 mmHg pCO2

Kim h hp mn 0.55 mEq/L HCO3- cho 1.0 mmHg pCO2

N B TRONG TOAN H HP

Bicarbonate khng th tham gia trong vic m H+ pht sinh do toan h hp :

CO2 + H2O = H2CO3 = H+ + HCO3

-

N B TRONG TOAN H HP

Bicarbonate c thnh lp khi cn bng CO2 + H2O = H2CO3 H+ + HCO3- c xy ra theo chiu phi

H+ c m bi Hb trong HC (giy n pht)

H+ vo trong t bo khc v c m bi proteins v phosphates (gi)

o thi H+ thn v to bicarbonate mi (2 n 6 ngy)

N B TRONG RI LAN CN BNG ACID-BASE

n b h hp cho ri lan chuyn ha phi han tt trong 24 gi

Cp l < 24-48 gi

Mn l > 24-48 gi

n b chuyn ha (thn) trong ri lan h hp chm hn v cn 2 n 6 ngy

ANION GAP Anion gap l sai bit gia cation (ion +) v anion (ion

- ) o c trong huyt thanh , huyt tng , hoc trong nc tiu . Trong y khoa , sai bit trong huyt thanh thng c tnh phn lai nguyn nhn ca toan chuyn ha. Nu anion gap ln hn bnh thng, chn an toan chuyn ha vi anion gap cao .

Thng dng thut ng "anion gap huyt thanh", hoc anion gap ca nc tiu .

ANION GAP C K+

Anion gap = ([Na+] + [K+]) ([Cl] + [HCO3])

Khng c K+ (thc hnh hng ngy )

Nng K= thng rt thp , t nh hng trn anion gap nn c th tnh :

Anion gap = [Na+] ([Cl-] + [HCO3])

Anion gap bnh thng : < 11 mEq/L

Anion Gap

RI LAN CN BNG ACID-BASE : PHN TCH

C ri lan cn bng acid-base khng ?

Ri lan nguyn pht l g ?

C mong i p ng th pht ?

Qu trnh bnh l c bn no gy ra ri lan cn bng acid-base?

IU HA CN BNG TOAN-KIM THN

Thn c chc nng d tr bicarbonate cho c th Theo sau l :

Ti hp thu 99.9% bicarbonate lc

Ti hp thu bicarbonate trao i vi o thi:

Acid (ch yu phosphate)

Mui Ammonium

Tt c nhng iu ny theo sau o thi H+

IU HA CN BNG TOAN-KIM THN

Nu H+ o thi kt hp vi bicarbonate lc, bicarbonate c ti hp thu

Nu H+ o thi kt hp vi phosphate hoc ammonia, o thi acid v thnh lp bicarbonate mi xy ra

Tt c l thuc vo h thng m m H+

gp trong dch ng thn, v lc dch l do chc nng ca nephron

TI HP THU BICARBONATE THN

ng gn: 70-85%

Quai Henle: 10-20%

ng xa v ng gp: 4-7%

YU T NH HNG N TI HP THU HCO3-

Lng bicarbonate lc

Th tch dch ngai bo

Thay i pCO2 ko di

Nng Cl- trong huyt tng

Nng K+ trong huyt tng

Hormone (t/d: mineralocorticoid glucocorticoid)

LNG ACID CHUN

Xy ra khi H+ b o thi gp phosphate trong dch ng thn

Lin quan n s lng base mnh cn chnh pH nc tiu v 7.4

40% (15-30 mEq) ca lng acid lc mi ngy

Tng i hng nh

O THI AMMONIUM

Xy ra khi H+ o thi kt hp vi NH3 v thnh mui NH4+ trong dch ng thn

60% (25-50 mEq) lng acid thi mi ngy

Rt thch ng (qua sn xut glutaminase )

O THI AMMONIUM

Mt s lng ln H+ c th c thi m khng lm pH nc tiu qu thp v pKa ca h thng NH3/NH4

+ rt cao (9.2)

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Can Bang Toan Kiem 2