theABG
20
the ABG
description
abg ppt
Transcript of theABG
the ABG
Learning Objectives
1.
Physiology2.
Clinical implications of disturbed ABG
3.
Standardised approach to interpret ABG’s
4.
(ABG is not the same as VBG!)
1. The ABG - physiology
H+
CO2 H+/HCO3
2. The ABG –
clinical implications
•
If the patient is acidaemic
they are sick – take this patient seriously.
3. The ABG – an approach
1.
Is there an acid base disturbance?2.
Is it due to a metabolic disturbance?
3.
Is it due to a ventilatory
disturbance?4.
Is there compensation?
5.
Is there a mixed disturbance?
Compensation
A system can not over compensate
i.e
The pH will never compensate beyond 7.4 (7.35-7.45)
Compensation
Metabolic acidosis•
CO2 = [1.5xHCO3] + 8 (+/-2)
1.Metabolic Alkalosis•
CO2 = 40 + 0.6[Δ
HCO3]
OR: CO2 = last two digits of pH +/-
5min 20, max 50-55
Compensation
•
Chronic Respiratory Acidosis–
Increase in HCO3 = 3.5(ΔCO2/10)
•
Chronic Respiratory Alkalosis–
Decrease in HCO3 = 6(ΔCO2/10)
Case 1 – NEJM challenge
•
54yr F admitted•
Abdo
pain
•
Vomiting•
Confusion
•
Type 2 DM, nephrolithiasis, HTN, CKD•
enalapril, metformin, glimepiride, nimesulide, imipramine, aspirin, and ibuprofen
•
SBP 120, HR 50, RR 26, afebrile, ECG AF 115•
Abdo
exam normal –
blood from NG
•
CT –
thick walled small bowel loops, pancreatitis
ABG
•
pH -
6.9•
CO2 -
24
•
HCO3 -
12•
O2 -
90
Interpretation??
Diagnosis?1.
Salicylate
overdose
2.
Renal tubular acidosis3.
Mesenteric ischaemia
4.
Diabetic ketoacidosis5.
Toxic effects of metformin
6.
Vomiting 7.
Rapid infusion of large volumes of N Saline
Check July 25 issue NEJM!
Case 2
•
22 yr•
Hx
of childhood
asthma•
Allergic rhinosinsitus
•
36 hours of deteriorating dyspnea
and wheeze•
Old ventolin
puffer not
effective
pH 7.47
CO2 30
HCO3 22
O2 80
pH 7.36
CO2 44
HCO3 26
O2 80
Case 3
•
65yr M•
80 pack year smoker
•
Severe COPD –
FEV1 40% predicted•
2 weeks of cough and dyspnea
•
1 week of amoxycillin•
BIBA sudden deterioration in shortness of breath and chest tightness
Case 3
•
pH 7.30•
CO2 75
•
HCO3 35•
PO2 160
What next?
Case 3
•
pH 7.36•
CO2 65
•
HCO3 35•
O2 62
Case 3
•
pH 7.33•
CO2 70
•
HCO3 37•
O2 65
What next?
Case 4•
80M
•
2 years progressive dypsnoea
and dry
cough•
3 days severe diarrhoea
•
pH 7.32•
CO2 40
•
HCO3 16•
O2 65
Case 5•
48M alcoholic + smoker
•
3/52 in hospital with severe pancreatitis
•
TPN for 1 week
•
Develops fevers and progressive SOB over 48 hours
•
pH 7.15•
CO2 49
•
HC03 18•
O2 95 (Fi02 40%)
•
Na 143•
K 3.8
•
Cl
117
1.
What does the gas show?
2.
Explain the pathophysiology.
Case 6•
38F
•
BMI 26•
Exercises at gym 3xweekly
•
HTN •
10mg perindopril
•
10mg amlodipine•
100mg metoprolol
•
Injures shoulder at gym - ED
•
Venous gas•
pH 7.51
•
CO2 48•
HCO3 34
•
O2 110•
Na 147
•
K 2.9•
Cl
110
1.
What does the gas show?
2.
What is the diagnosis?
