THANG BANG ACID - BASE
14. Chtfc nang chuyen hoa cac ch&'t cua than
Than tham gia vao cac qua trinh thoai hda glucid, lipid de cung cap nang
ltfdng cho than.
Dac biet d than cd nhidu enzym khtf amin nhtf L-aa dehyrogenase cua
glycin, L-glutamic va cac transaminase. Vi vay, than tao ra nhidu acid a-cetonic va
NH3 (bai xua't trong ntfdc tieu dtfdi dang mudi ammoni).
Than con tham gia qua trinh to'ng hdp acid hippuric ttf glycin va a. benzoic cung nhtf qua trinh khtf ntfdc cua creatin de tao thanh creatinin.
Ngoai ra than con tham gia qua trinh dieu hda chuyen hda muoi ntfdc cda
cd the. *
2. NlJCfC TIEU
Ntfdc tieu la dich bai xua't bdi than, di qua nieu quan, chtfa d bang quang va
dtfdc thai ra ngoai qua nieu dao. Ntfdc tidu chtfa phin ldn nhtfng cha't can ba cda cd thd Cac thay do'i vd cac chi sd hoa ly va thanh phin hda hoc cda ntfdc tieu la
nhtfng bidu hien cho tha'y cd nhtfng rdi loan chuydn hoa trong cd thd. Xet nghiem phan tich ntfdc tidu giiip danh gia dtfdc cac rdi loan chuydn hda cd the xay ra va de dam bao kdt qua xet nghiem dtfdc chinh xac cln phai lay mau chinh xac va dung
quy each.
2.1. Tinh chat chung cua ntfdc tieu
2.1.1. The tich ntfdc tieu
Thd tich ntfdc tidu trung binh d ngtfdi ldn trong 24 gid vao khoang 1.000 ml -
1.400 ml (khoang 18 - 20 ml/kg can nang).
Cac nguyen nhan sinh ly cd thd lam thay do'i thd tich ntfdc tieu bao gom:
- Tudi: tre em tidu nhieu hdn ngtfdi ldn (tinh theo can nang).
- Thtfc an : ltfdng ntfdc udng vao cang nhilu.-hutfc tidu cang nhieu (trung binh
2.500 ml/ngay d ngtfdi ldn).
-Ltfdng ntfdc thoat ra (hdi thd, mo hoi) cang nhieu, ntfdc tieu cang it. ^ - Nhiet do va do am cda khong khi cung anh htfdng ddn thd tich ntfdc tieu.
Cac trtfdng hcfp benh ly : .. • , -
-Ltfdng ntfdc tidu cd thd len tdi tren 2.500 ml/24 gid trong trtfdng hdp dai thao
dtfdng, dai thao nhat.
- Ltfdng ntfdc tidu dtfdi 750 ml/24 gid gap trong cac trtfdng hdp thieu nieu, vo nieu do ro'i loan bai tidt (do benh viem clu than, viem o'ng than, mat mau, bong nang), hoac do stf ngan chan cd hoc (do soi dtfdng nieu).
2.1.2. Mau cua ntfdc tieu , v
Mau cda ntfdc tidu binh thtfdng thay do'i ttf vang nhat den mau ho phach,
tuy thuoc ltfdng ntfdc tidu bai xua't va dam do cda ntfdc tidu. Mau ntfdc tieu do cac
-, sac td trong ntfdc tieu nhtf urochrom, urobilin (san pham oxy hoa cda urobilinogen khong mau), cac dan xuat cda indoxyl, porphyrin. Cac sac to tren cd the tang trong mot sd benh ve gan, mat. Ngoai ra, mot so dtfdc pham dao thai qua ntfdc tieu
(rifampicin, vitamin B2...) cung lam thay ddi mau cda ntfdc tieu.
2.1.3. Do trong suot
Ntfdc tieu binh thtfdng thi trong suot. Sau khi de yen mot thdi gian, trong ntfdc tieu se cd vln due Id lffng dgiffa hay lang xuo'ng day dng dtfng ntfdc tidu (tuy
vao ty trong cda ntfdc tieu). Nhffng vln due nay la nhffng te bao noi md cda cac
dtfdng tiet nieu va cac chat nhay uromucoid.
Ntfdc tieu binh thtfdng sau khi de yen trong lo vln cd the xua't hien tda lang xudng day. Dd cd the la can acid uric, mud'i urat natri, hay muo'i phosphat. Hai loai muo'i urat va phosphat cd the phan biet bang each dun ndng ntfdc tieu, muo'i urat se tan khi dun ndng, ntfdc tieu trong trd lai; con can phosphat khong tan trong moi trtfdng trung tinh va kiem, chi tan trong mdi trtfdng acid nhe (nhtf acid acetic).
2.1.4. Dr) sanh
Ntfdc tieu binh thtfdng cd do sanh cao hdn ntfdc mot it. Trong cac trtfdng hdp benh ly, stf cd mat cac chat nhtf md, mau, protein, mucoprotein, dtfdng chap,
md... lam tang do sanh, hoi, va cd bot.
2.1.5. Mui
Ntfdc tieu binh thtfdng cd mui dac biet. Cac trtfdng hdp benh ly lam bie'n
ddi mui cda ntfdc tieu nhtf mui aceton (tieu dtfdng), hay mui thd'i (sot cao, ung thtf
than, bang quang).
2.1.6. Stfc cang mat ngoai
Binh thtfdng ntfdc tieu cd stfc cang mat, ngoai tha'p hdn ntfdc (64-69 dynes/cm2 so vdi 72 dynes/cm2 cua ntfdc). Mot so chat khi dtfdc dtfa vao cd the cd the lam giam stfc cang mat ngoai cda ntfdc tieu nhtf: alcol, ete, cloroform. Trtfdng hdp benh ly vang da tac mat, muo'i mat xua't hien trong ntfdc tieu cung lam giam
stfc cang mat ngoai cda ntfdc tieu.
2.1.7. Ty trong
Ty trong cda ntfdc tieu binh thtfdng cda ngtfdi ldn trong 24 gid, do d dieu
kien 15° C, thay ddi ttf 1,005 -1,030. Trong trtfdng hdp benh ly nhtf dai thao dtfdng
do tuy, ty trong ntfdc tieu cd the tang len 1,030 -1,040.
2.1.8. Do pH cua ntfdc tieu
Ntfdc tieu binh thtfdng cd phan tfng hdi acid, cd pH khoang ttf 5-6, thtfdng khoang 5,8. Ltfdng acid trong ntfdc tieu ngtfdi binh thtfdng trong 24 gid cd ndng do ttfdng tfng khoang 30-40 mEq H+ , ttfdng dtfdng vdi khoang 2g acid sulfuric.
Do acid cda ntfdc tieu la do stf cd mat cua cac acid ttf do nhtf acid acetyl acetic, acid uric, phosphat acid ( P04H2" ) va stf bai xuat cac hdp chat acid dtfdi dang mud'i ammoni nhd vai trd dieu hoa thang bang acid-base cua than.
Cac dieu kien sinh ly cd the lam thay ddi do pH cda ntfdc tieu. Khi khau phin an cd nhieu dam thi pH ntfdc tieu cang acid, khi khau phin an cd nhieu rau thi ntfdc tieu cd it acid hdn, pH cd khi trung tinh hoac kiem. Khi van dong the ltfc nhieu, lao dong nang cung lam tang do acid cda ntfdc tieu.
Cac trtfdng hdp benh ly cd the lam thay ddi pH ntfdc tieu nhtf sau :
- Trong trtfdng hdp viem be than, viem bang quang thi pH ntfdc tieu thtfdng
kiem vi cd stf len men ammoniac.
- Do'i vdi nhtfng benh nhan dai thao dtfdng the ceton, pH ntfdc tidu thtfdng acid do cd stf bai xua't acetyl - acetic, p-hydroxybutyric dang ttf do va dang muo'i
ammoni.
2.2. Thanh phin cac chS't cua ntfdc tieu binh thtfdng
Ntfdc tieu binh thtfdng trong 24 gid sau khi bo'c hdi d 100-110°C, thu dtfdc can khd ntfdc tieu (55 - 57g/ntfdc tieu 24 gid) gdm nhffng chat vd cd va hffu cd. Can kho sau do dem nung thu dtfdc tro de xac dinh thanh phin cua ntfdc tieu.
2.2.1. Cac thanh phin vo cd (khoang 15-25g/24gicf)
Thanh phin vd cd cda ntfdc tieu binh thtfdng trong 24 gid dtfdc trinh bay d
bang 9.1 sau :
Bang 9.1. Thanh phin cac chat vo cd trong ntfdc tieu 24 gid
Thanh phin Ndng do Thanh phan Ndng dQ
Na+ 3-5g ; Zn2+ 600mg
K+ 2-4g . I" 50-250pg
Ca2+ 0,l-0,2g Cu2+ 100 pg
Mg2+ 0,05-0,2g As 50 pg
NH4+ 0,3-lg Pb 50 pg
c r 5-9g
po43- 2-2,5g
so42" 0,7-3,5g Natri va Kali
Binh thtfdng cd the dao thai khoang 3-5g Natri va 2-4g kali trong ntfdc tieu trong 24 gid. Stf dao thai nay thay ddi theo che do an, tinh trang can bang acid-base
cda cd the va dtfdc dieu hoa bdi hormon vd thtfdng than.
Calci va Magne
Phin ldn ltfdng calci va magne dtfdc dao thai d ruot. Khoang 15-30% ltfdng
calci va 20-50%ltfdng magne dtfdc dao thai ra ngoai qua ntfdc tieu. Trong mot sd benh chuyen hoa xtfdng ltfdng nay cd the thay ddi. -
Clo
Stf bai xua't clo phu thuoc che do an. Ltfdng clo trong ntfdc tieu giam trong mot sd trtfdng hdp benh ly nhtfviem than, benh nhiem trung.
Phosphat
Phosphat bai tie't qua phan va ntfdc tieu chd yeu la d dang vo cd. Phosphat cd 2 nguon gd'c ngoai sinh (dtfdc dtfa vao cd the ttf thtfc an) va noi sinh (do thoai hoa phospholipid va nucleoprotein). Hai thanh phin phosphat acid (H2P04") va phosphat base (HP042) tao thanh he thdng dem chinh cda ntfdc tieu (quyet dinh pH ntfdc tieu). Cac muo'i phosphat it tan (mud'i calci va magne) xua't hien trong ntfdc tieu kiem (thtfdng la thanh phin cda soi nieu). Stf bai xua't phosphate tang len trong mot sd benh ve xtfdng, ctfdng can giap va giam trong trtfdng hdp thieu nang can
giap.
Sulfat
Sulfat cd nguon gd'c chu ydu ttf stf thoai hoa hoan toan cac acid amin chtfa Itfu
huynh. Stf bai xua't sulfat qua ntfdc tidu phu thuoc vao Itfdng protein trong thtfc an.
Cd 2dang sulfat chinh trong ntfdc tieu binh thtfdng:
^- Sulfat vd cd: ty le vdi ltfdng protein thtfc an, ltfdng sulfat vd cd dtfdc xem la
chi so'thoai hoa protein.
- Sulfat lien hdp (10%): cd trong cac chat hffu cd nhtf sulfon, cresol, indoxyl...
va mot ltfdng nho acid amin cd chtfa ltfu huynh.
Amoniac
Amoniac dao thai qua ntfdc tieu chu yeu dtfdi dang ion NH4+ do stf khuech tan NH3 ttf te bao o'ng than ra va ket hdp vdi ion H+
2.2.2. Cac thanh phan hffu cd (khoang 30-40g/24gid)
Thanh phin hffu cd cua ntfdc tieu binh thtfdng trong 24 gid dtfdc trinh bay d
bang 9.2 sau : ••