Presentasi asam basa sederhana

1. Interpretasi
Analisa Gas Darah
Akhyar Albaar
Division of Nephrology and Hypertension
Department of Internal Medicine
Hasanuddin University

2. Approaches to Understanding Acid-Base
Physiology
• Traditional Approach
– The discussion of acid-base physiology outlined in most of
this lecture is the ‘traditional’ empirical approach. The
concepts and explanations of this approach are still the
most common way that acid-base physiology is taught
and understood by many clinicians to some extent
• Physico-chemical Approach
– An alternative approach derived from physico-chemical
principles was proposed by Stewart in 1981

3. pH
• The term pH was coined by the Danish
chemist, Soren Peter Sorensen in 1909 to
refer to the negative log of hydrogen ion
concentration
• The symbol pH meaning ‘potenz’ (power) of
Hydrogen.
• pH = -log [H+]

4. Relationship between pH & [H+]
pH [H+]
(nanomoles/l)
6.8 158
6.9 125
7.0 100
7.1 79
7.2 63
7.3 50
7.4 40
7.5 31
7.6 25
7.7 20
7.8 15

5. Terminology of Acid-Base Disorders
• Acidosis –
– an abnormal process or condition which would lower arterial pH
if there were no secondary changes in response to the primary
aetiological factor.
• Alkalosis –
– an abnormal process or condition which would raise arterial pH
if there were no secondary changes in response to the primary
aetiological factor.
• Simple Disorders
– are those in which there is a single primary aetiological acid-
base disorder.
• Mixed Disorders
– are those in which two or more primary aetiological disorders
are present simultaneously.
• Acidaemia - Arterial pH < 7.36 (ie [H+] > 44 nM )
• Alkalaemia - Arterial pH > 7.44 (ie [H+] < 36 nM )

6. The Anion Gap
• Anion gap = [Na+] - [Cl-] - [HCO3
-]
• Reference range is 8 to 16 mmol/l.
• An alternative formula which includes K+ is :
– AG = [Na+] + [K+] - [Cl-] - [HCO3-].

7. Na +
140
Other Cations
Other Anions
HCO3-
A-
Cl -
Anion gap = [Na+] - [Cl-] - [HCO3
-]
25
103
Unmeasured Anions
Proteins (15 mEq/L)
Organic Acids (5 mEq/L
Phosphates (2 mEq/L)
Sulfates (1mEq/L)
UA = 23 mEq/L
Unmeasured Cations
Calcium (5 mEq/L)
Potassium (4.5 mEq/L)
Magnesium (1.5
mEq/L)
UC = 11 mEq/L

8. Na +
140
Other Cations
Other Anions
HCO3-
A-
Cl -
Metabolic Acidosis with increased anion gap
103
L- Added Anions
When an
acid such
lactic
acid is
added
The
HCO3-
will fall
and
replaced
by
lactate
anion

9. Na +
140
Other Cations
Other Anions
HCO3-
A-
Cl -
25
103
Other Anions
HCO3-
A-
Added Anions
A-
L-
Normal AG Increased AG

10. Na +
140
Other Cations
Other Anions
HCO3-
A-
Cl -
Metabolic Acidosis with normal anion gap
Note that
with a loss
of
NaHCO3
HCO3- will
fall but no
new anions
will be
added

11. Figure 27.15
A Diagnostic Chart for Acid-Base Disorders

12. Clinical Acid Base Problem Solving
• Langkah Pertama :
– Harus tahu harga normal parameter yang akan digunakan
untuk menganalisis kelainan asam basa :
– a. pH 7.40 atau [H+ ] 40 nmol/L
• Cara merubah pH ke dalam [H+ ] : pada pH 7,0  100 nmol (setiap
kenaikan 0,1 dikali 0,8 dan penurunan 0,1 dikali 1,25)
• Buang angka tujuh dan desimalnya jadi misal pH 7.26 didapat 26
Kurangi 40 dengan nilai tersebut jadi 40 – 26 = 14
Tambahkan 40 kedalam harga tersebut : 40 + 14 = 54 nmol
– b. pCO2 = 40 mm Hg
– c. [HCO3
] = 24 mmol/L
– d. Anion gap plasma Na-(Cl+[HCO3
]) = 12 mEq/L jika kadar
albumin normal yaitu 4 gr% . Setiap penurunan albumin 1 gram
% dari harga normal maka kadar AG dikurangi 4

13. Clinical Acid Base Problem Solving
Langkah Kedua :
– Apakah ada Lab Error ?
– Cara mengetahuinya adalah masukkan harga pH ,
pCO2 dan [HCO3
] kedalam persamaan Henderson di
bawah ini : [H+ ] = pCO2 X 24/ [HCO3
]
– Jika [H+ ] yang dihitung dan yang diukur berbeda lebih
dari 10% maka ada lab error .
– Kita harus mengulangi pemeriksaan. Kita tidak ingin
menganalisis hasil AGD berdasarkan hasil
laboratorium yang salah .

14. Clinical Acid Base Problem Solving
Langkah Ketiga :
– Tetapkan hasil pH :
• Acidemia jika kurang dari 7.36
• Alkalemia jika lebih dari 7.44

15. Clinical Acid Base Problem Solving
Langkah Keempat :
–Tentukan apakah kelainan primernya
respiratorik atau metabolik
–Alkalemia :
• Respiratory Alkalemia jika pCO2 kurang dari 35
• Metabolic Alkalemia jika [HCO3
] lebih dari 24
–Acidemia :
• Respiratory Acidemia jika pCO2 lebih dari 45
• Metabolic Acidemia jika [HCO3
] kurang 24

16. Clinical Acid Base Problem Solving
Langkah Kelima :
–Hitung anion gap (AG) serum yaitu :
–Kadar Na serum – ( Cl + [HCO3
] serum
• Jika AG > 10 ada kemungkinan
metabolic acidemia
• Jika AG > 20 dapat dipastikan
ada metabolic acidemia
–Jangan lupa factor albumin !
Na+
(140)
A-
Cl-
(103)
Other
Cation
HCO3-
(25)
Other
Anion

17. Clinical Acid Base Problem Solving
Langkah Keenam :
– Check derajat kompensasi tubuh :
• Metabolic Acidemia :
– Setiap penurunan pCO2 = 1.2 X penurunan [HCO3
]
• Metabolic Alkalemia :
– Setiap kenaikan pCO2 = 0.7 X kenaikan [HCO3
]
• Respiratory Acidemia :
• Akut :
– Setiap pCO2 naik 10 mmHg = [HCO3
] naik 1 mEq/L
• Kronik :
– Setiap pCO2 naik 10 mmHg = [HCO3
] naik 3 mEq/L
• Respiratory Alkalemia :
• Akut :
– Setiap pCO2 turun 10 mmHg = [HCO3
] turun 2 mEq/L
• Kronik :
– Setiap pCO2 turun 10 mmHg = [HCO3
] turun 5 mEq/L

18. Clinical Acid Base Problem Solving
Langkah Ketujuh :
– Determine Delta ratio (Delta gap) =
(Increase in anion gap / Decrease in
bicarbonate)

19. Guidelines for Use of the Delta Ratio in Metabolic
Acid-Base Disorders
Delta Ratio Assessment Guideline
< 0.4 Hyperchloraemic normal anion gap acidosis
0.4 - 0.8 Consider combined high AG & normal AG
acidosis Ratio often <1 in acidosis assoc.
with renal failure
1 to 2 Usual for uncomplicated high-AG acidosis
Lactic acidosis: average value 1.6
DKA more likely to have a ratio closer to 1
due to urine ketone loss (esp if patient not
dehydrated)
> 2 Suggests pre-existing elevated HCO3 level:
consider a concurrent metabolic alkalosis
or a pre-existing compensated respiratory

20. Kasus 1
pH : 7,59
PaO2 : 89 mmHg
PaCO2 : 30 mmHg
HCO3 : 24 mEq/L
BE : +3
SaO2 : 96%

21. Kasus 2
pH : 7,21
PaO2 : 56 mmHg
PaCO2 : 51 mmHg
HCO3 : 18 mEq/L
BE : -8
SaO2 : 90%

22. Kasus 3
pH : 7,36
PaO2 : 76 mmHg
PaCO2 : 56 mmHg
HCO3 : 30 mEq/L
BE : -4
SaO2 : 92 %

23. Kasus 4
pH : 6,84
PaO2 : 55 mmHg
PaCO2 : 55 mmHg
HCO3 : 18 mEq/L
BE : -6
SaO2 : 70 %

24. Selamat Belajar…