Bi ging

cn bng acid-base

TS. Phan Hi Nam

i cngI. Khi nim cn bng acid-baseII. Cc c ch n nh cn bng acid- base 2.1. Hot ng ca cc h m : + H huyt tng + H ca hng cu 2.2. Hot ng sinh l ca phi 2.3. Hot ng sinh l ca thn.III. Mt s thng s chnh nh gi trng thi CBABIV. Mt s ri lon CBAB * Mt s lu v XN CBAB

Khi nim cn bng acid-baseCBAB - S n nh nng ion hydro (pH) dch th/ l trng thi m H+ thch hp nht cho cc CH/ c th. Nc (60-70%) phn ly: H2O H+ + OH- trng thi cn bng phn ly (L tc dng khi): [H+] [OH-] = k = 10-14 (k- hng s phn ly) H2OV [H+ ]= [OH-] =>[H+]x[OH-] = [H+]2 = 10-14Log [H+]2 = Log 10 -14 =>2 Log [ H+] = - 14 -> Log [ H+] = -7 Qui c: pH l gi tri m ca Log nng H+, tnh: pH = - Log [ H+]

nh hng ca pH ti cc phn t sinh hc +pH thay i: -> thay i cc lin kt hydro, LK disulfua (-S-S-)=> thay i cu trc, CN ca protein c bit protein l enzym -> ri lon hng, tc v cng cc f/ m E xc tc. + pH nh hng: - Receptor/ mng Tb (nhn bit v v.c cht qua mng TB)- Hb & i lc gn O2 ca Hb - Acid nucleic (AND, ARN)- Di truyn. - Khng th- bo v c th - Hormon ( HCH)

Cc nguy c gy ri lon CBABS to thnh CO2, H2CO3: - CO2: Krebs & kh carboxyl ca amino acid (~ 200 ml/min). - CO2 kt hp vi nc, phn ly to H+ & HCO3-:CB ng CO2 + H2O H2CO3 H+ + HCO3- Nu CO2 ko o thi -> nhim acid (cn bng -> phi). S to thnh acid HC, VC:+ Chuyn ho G, L, P -> SPTG a s l acid1,3-DPG, a.pyruvic RL:--> acid pyruvic, lactic, -Hydroxybutyric ,-> nhim acid , RL cc CH -> xu hng nhim acid: acidoseBnh l: + Bnh lm acid mu: - Tiu ng: acid cetonic/M

Nguy c gy ri lon CBAB+ Bnh lm kim mu:- Nn/ tc mn v, ht dch v DD: mt H+- Dng qu nhiu thuc li niu.- Tim, truyn qu nhiu Nabicarbonat (sai .+ : pH mu M: 7,38 7,42 duy tr c do H+ = H+ o thi. => CBAB thc cht l duy tr s n inh ion H+/ c th.Cc c ch n nh CBAB: 1- H m (Ht, HCu). 2- H sinh l phi 3- H sinh l ca thn.

Cc h m ca mu

H m mu= H huyt tng + H Hng cu

Vai tr ca cc h m/ iu ho CBABH huyt tng: * H m bicarbonat: H2CO3/ NaHCO3+ Quan trng: 35% DT/ c th, iu ho: nhanh, mnh.+ Cn bng ng: CO2 + H2O H2CO3 H+ + HCO3-+ Pt Handerson-Haselbalch:

pH = pK H2CO3 + log = 6,1 + log + C ch H: KM => Kim yu; Acid mnh => acid yu-> T - Kim (OH-) / M => Kim yu, XOH + H2CO3 XHCO3 + H2O, VD: NaOH + H2CO3 NaHCO3 + H2O. - Acid (H+) / M: RH + NaHCO3 RNa +H2CO3 (phn ly)VD: HCl + NaHCO3 NaCl +H2CO3 H2O [HCO3- ][ H2CO3 ]0.03. pCO2[HCO3- ]CO2Phi -> thi

H m huyt tng* H m protein:+ Cu to t cc A.A (COOH, NH2), c tnh lng tnh:- COOH COO- + H+ ( + base) - chng li kim ho - NH2 + H+ NH3+ - chng li acid ho.+ Chng li acid = a.a kim (Arg, Lys)/ NH2 + H+ NH3+.+ Chng li kim = a.a acid (Glu, Asp)/ H+ + base (OH-). Vai tr m: ng k (60 80 g/l) * H m phosphat (NaH2PO4/ Na2HPO4 )- Tt v c pK = 6,8 (~ 7,40).- Vai tr m: yu v c nng thp/ M (1 2 mmol/l)

H m hng cu+ HC c H bicarbonat, phosphat nhng VT m ch yu do Hb + Hb c 2 H: HHb/ KHb & HHbO2/ KHbO2, m = 2 cch:1- To DX carbamin: NH2/ Hb + CO2 -> dx carbamin (5% CO2).2- Nh hot ng ca nhn Imidazon/His: Hb + O2 -> HbO2 + H+, H+ -> pH/ phi (*) HbO2 + H+ -> HHb + O2 => H+ -> pH/ TC (*) Vai tr m ca Hb l o thi CO2 cho c th -> chng acid ho (S )

K+HCO3- K+HCO3- K+HCO3- H2CO3H2OCO2CAKHbO2 KHbO2 KHbO2 CO2H2OCAO2H2CO3CAHHb HHb HHb H+O2H+K+K+HCO3- HCO3- MCh.hoTh raT chcMuPhiTMBt: CO2/TC = CO2 / Phi

Phi iu ho CBABCO2CO2 th raPhiMuT chcH+ HCO3 - +H2CO3CO2H2OBT: CO2/TC = CO2/ phiNhim acid (H+ /M): . TK phi (TS, B th) -> o thi CO2 (chng acid). CO2 phi > CO2/ TC Nhim base (OH- /M): CO2MuT chcOH - HCO3 - CO2Phi . TK phi ( TS, B th) -> o thi CO2 Tt: Phi o thi CO2, bn b, lin tc => iu ho CBAB c hiu quHn ch: k , TS, B th qu mcCO2 + H2O H2CO3 H+ + HCO3- . CO2 TC > CO2/ Phi

Thn iu ho CBAB* c im: chm, hiu qu mnh, duy tr HCO3-/ H.t & DGB* Ti hp thu gn hon ton HCO3-: 90%/ TB L gn, 10% L xa.

TB ng ln gnMao qunLng .T (NTB)NaHCO3Na+Na+Na+K+K+HCO3-HCO3-HCO3- (90%)H2CO3H2CO3H2O +H2OCO2CO2CO2CAH+H+E1E2E1- HCO3-.ATPaseE2- Na+,K+-ATPaseTHT HCO3- : + PCO2 (CC b tr ca thn khi c th nhim base, acid h hp) + THT Na+/ TB ng thn.

Thi H+, ti hp thu HCO3- ng ln xaLng T (NT u)TB ng ln xaMao qunHPO4--Na+Na+K+Na+K+K+RHCO3-H2CO3H2OCO2NH3CO2H+H+H2 PO4-RHHCO3-(~10%)NH4+GlnE2E1GluGlutaminase+ o thi H+: Acid (RH), mui amoni, mui phosphat+ Ti hp thu HCO3- : ~ 10% + Tn to HCO3-: : n bt-> 50- 100 mmol H+/ 24h/: H2SO4 (SPCH a.a S); H3PO4 (SPTH ca P0-Lipid, acid nucleic); A.uric-(base purin) -> H+ . H+ + HCO 3- -> Nguyn nhn mt HCO3-, b li? = Tn to HCO3 - ~ to NH4+ (ko -> TB .L xa). Mt : ti TB thn -> CO2, + H2O -> H2CO3 -> HCO3-.

Cc thng s nh gi trng thi cn bng acid- base pH mu PaCO2 Bicarbonat Bicarbonat thc ( Actual Bicarbonat = AB) Bicarbonat chun (Standard bicarbonat = SB) CO2 ton phn ( Total CO2 = t.CO2) Base m (Bufer base = BB) Base d (Base excess = BE)

pH mu pH mu/ M = 7,38 7,42. pH < 7,38 nhim acid pH > 7,42 - nhim base pH mu/TM < M 0,02 pH -> nh gi mc b tr ca c th:- Acidose: pH 7,38 7,42: b ton phn (nhim acid) 7,37 7,25: b 1 phn < 7,25: mt b. - Alcalose: pH 7,38 7,42 : b ton phn (nhim base) 7,43 7,55: b 1 phn > 7,55: mt b. + pH < 7,30: Nhim toan h hp: ph qun ph vim Nhim toan CH nng: T. + pH > 7,55: Nhim kim h hp: CTSN Nhim kim chuyn ho nng: a chy ko di..

PaCO2, CO2 ton phn : PaCO2 = 40 mmHg - Thng s cho bit cc ri lon CBAB do NN h hp - Ph thuc thng kh ph nang: khi TKPN v ngc li.BL: - nhim toan HH do o thi CO2 phi, gp: . Thng kh PN, tc nghn ph qun . Bnh phi: PQPV, vim phi, hen . Ht phi CO2, ht li Ko kh th . B c ch TK: thuc ng, bi lit, nhim c, CTSN, u not.CO2 = CO2 ha tan + CO2 carbaminat + CO2/bicarbonat PaCO2-5% (+Hb)- 5% HCO3-- 90% . : t.CO2 = 25 - 30 (mmol/l). t.CO2 : Nhim toan h hp, nhim kim CH

Bicarbonat ( HCO3-) + L lng HCO3- c trong H.T 37OC, gm B thc v B chun. - Bicarbonat thc (actual bicarbonat = AB): . L nng thc t HCO3- ca mu mu M ly K ko tip xc vi ko kh, n tng ng vi pH v PaCO2 thc ca mu mu. . : AB = 25 mmol/l. - Bicarbonat chun (standard bicarbonat= SB): . SB: l lng HCO3- (mmol/l) ca h.t c qui v K chun nh PaCO2= 40 mmHg, To= 37oC, pH = 7,40. . : SB = 24 2 (mmol/l). + L TS cho bit RLCBAB lin quan ti NN chuyn ho. BL: HCO3-: NT h hp, NKCH: nn nhiu, ht dch DD, a chy : Nhim toan CH, gp: . T do ng cc th cetonic. Ph phi cp, ng kinh: RLCH glucid-> ng acid lactic.. Vim thn cp; mn: ko thi c acid. a chy cp lm mt HCO3-

Base m (Buffer base = BB), Base d (Base exess = BE) Base m: L tng cc anion m trong mu (mmol/l). BB = [HCO3-] + Protein- + Hb- + Phosphat- : 46 - 48 (mmol/l) Base d : L s chnh lch gia BB ca BN v BB ca ngi bnh thng. : BE = 0 (pH = 7,40; PaCO2= 40 mmHg; Hb TP = 150 g/l, 37OC). BE cng vi Bicarbonat l 2 TS c ngha xc nh nguyn nhn RLCBAB do chuyn ho. BE dng () gp: Nhim kim CH (nn nhiu, a chy ko di..) BE m () gp : Nhim toan CH (T..)Ch : + Cc TS: pH, PaCO2 - o = CCL Cc TS khc: HCO3- (AB), t.CO2, BB, BE- tnh ton + Kt qu CBAB chnh xc khi: - Ly mu: . M (tr, quay,cnh tay), MM ho - u ngn tay, di tai . Dng c chuyn bit-> Mu ko tip xc vi ko kh. - My c chy chun, o ngay.

Cc ri lon cn bng acid- base 3 nhm RL: - Do N.N h hp, N.N chuyn ho & Do N.N hn hp. ( PaCO2) (HCO3-, BE)

PaCO240

Nhim toan h hpRi lon khi pht l pCO2 do thi tr CO2 phi, gp: * Bnh phi: - P. Qun, ph vim - Vim phi - Hen - Kh thng phi * HCTK: - Thuc ng - Bi lit - CTSN, u no - Ri lon tun hon no * Ht phi CO2/ k.kh th * XN: pH (< 7,38) pCO2 (> 40mmHg) HCO3- mu (> 25 mmol/l) t CO2 , cc TS khc t thay i

Nhim kim chuyn hoL trng thi tha Base hoc mt acid (ko phi l H2CO3) * Nguyn nhn: + Qu tha base: - qu nhiu bicarbonat (T) - n ung: qu nhiu cht t/c kim + Do mt acid: - Nn nhiu (HCL , K+ ) - Ht D.dy (Cl- ), a chy(H+ ) - Thuc li niu nhiu -> K+ * KQXN cc thng s: - pH mu (> 7,5, mt b) - pCO2 (> 40mmHg do thng kh ) - HCO3- (> 25mmol/l) v tCO2, BB , BE

Nhim kim h hpRi lon khi pht l pCO2Gp: + Thng kh phi : - Giai on u vim phi - St cao - H hp nhn to qu mc - CTSN + Th trong kh quyn c pCO2 thp (ln cao) KQXN: - pH mu (> 7,42) (khi mt b) - pCO2 mu - t.CO2 - BB - BE (-)

Nhim toan chuyn ho L s mt anion m- ch yu l HCO3- mu&D ngbo; Tch lu cc acid C/ thc t l acid mnh m anion ca chng ko th bi xut qua thn *KQXN - pH mu (< 7,24- mt b) - pCO2 (f/ b tr ca phi) - t.CO2 Hoc bnh thng - SB - BB , BE (-) - HCO3- * Gp: - tiu ng ( acid cetonic) - RLCH Glucid: ng a.pyruvic, a.lactic - Tn thng thn: THT HCO3- RL => HCO3- - T nhiu thuc li niu -> thi HCO3- => HCO3-

Nhim toan hn hp L s kt hp nhim toan CH v h hp => pH mu * XN: - pH mu mnh - p CO2 - HCO3- - SB va - BB - BE(-) Nhim kim hn hpL kt hp ca nhim kim h hp v nhim kim chuyn ho => pH mu rt nhiu * XN: - pH mu - pCO2 t - HCO3- - SB : 34-36 mmol/l (bt 24mmol/l)