1. ABGseries
ANASSAHLE , MD
DAMASCUSE HOSPITAL

2. Acid-Base Disorders and the ABG 3
3. BREIFPREVIEW
4. Summary of the Approach to ABGs
Check the pH
Check the pCO2
Select the appropriate compensation formula
Determine if compensation is appropriate
Check the anion gap
AG=NA (HCO3 + CL):124
If the anion gap is elevated, check the delta-delta
G:G Ratio = AG (12-AG) HCO3 (24-HCO3)
If a metabolic acidosis is present, check urine pH
Generate a differential diagnosis
5. EXPECTED CHANGES IN
ACID-BASE DISORDERS
From: THE ICU BOOK - 2nd Ed. (1998) [Corrected]
6. 7. Gap:gap ratio??
8. 9. HIGH AG M.AC
Osmolal gap = measured serum osmolality -(2 NA + gluco18 + bun2,8)
Corrected osmolal gap =
measured serum osmolality -(2 NA + gluco18 + bun2,8 + ETOH4,6)
10. HIGH AG M.AC
High
normal
11. Expected PCO2 : Measured PCO2
12. YES
NO
YES
NO
YES
NO
YES
NO
13. 5,5
Urine AG = (UNA +UK) - UCL
14. CASE:1An old man with abdominal pain & shock
An 85 year old man was admitted with severe abdominal pain and shock.
The abdominal pain started about 15:00hrs and quickly became quite severe.
There was no radiation to the back.
The patient was known to have an abdominal aortic aneurysm (AAA).
On arrival at hospital, the patient was shocked with peripheral circulatory failure and hypotension (BP 70-80 systolic).
The abdomen was guarded and quite tender.
He was distressed but able to talk and could understand instructions.
Past history was of hypertension (on metoprolol and prazosin) and angina (on Isordil).
Prior to this event, the patient was mobile and independent.
15. Biochemistry
at 15:20hrs was:(All results in mmol/l)
Na+ =138,
K+= 4.9,
Cl- =107,
Glucose= 11.2= 201mgdl
Urea =12.8=230 mgdl
Creatinine= 0.188=3,38mgdl.
Anion gap was =11
Mgdl = mmol /L * 18
16. CONTINUE
A ruptured AAA was diagnosed clinically and he was transferred to theatre for emergency laparotomy.
On arrival in theatre BP was 120 systolic.
The patient was talking but distressed by pain with rapid respirations at a rate of 30/min.
It was noted that neck veins were very distended.
An external jugular triple lumen central line and a brachial arterial line were placed before the surgical team had arrived in theatre.
CVP was +40 mmHg.
17. CONTINUE

pre-oxygenation with 100% oxygen at 17:38 hrs

(about 4.5 hours after onset of symptoms:

A lactate level collected at the same time as the blood gases was 8.3 mmol/l.