How to read blood gas analysis results

A blood gas analyzer can be used to determine whether the body's Qi and blood are sufficient or insufficient, but how do we read the results of a blood gas analysis? Generally speaking, the results of the inspection can be seen from six aspects. These include normal pH values, alkali poisoning, acidosis, normal PCO2 values, alkalinity, etc. Each has a standard value, and the standard value is used to detect whether there are certain problems with the body. Of course, the test results should still be viewed by a doctor.

Six steps to teach you how to quickly interpret blood gas analysis

(I) Look at the pH value to determine whether it is acidosis or alkali poisoning

1. Normal pH value: 7.35~7.45, average value is 7.40

2. Alkali poisoning: PH>7.45

3. Acidosis: pH < 7.35

4. When pH < 7.2, alkali supplementation is required

(II) Determine whether it is alkaline or acidic breathing by looking at PCO2

1. Normal value of PCO2: 35~45mmHg

2. Respiratory alkali: PCO2<35mmHg

Common cause: Hyperventilation

Solution: For those with ventilators, adjust the ventilator frequency, tidal volume, etc.; for those without ventilators, use a mask to breathe oxygen.

3. Respiratory acidosis: PCO2>45mmHg

Common causes: CO2 retention, ventilator paralysis or weakness, upper airway obstruction, airway stenosis, etc.

Solutions: Increase alveolar ventilation, treat primary disease, mechanical ventilation, suction sputum, etc.

(III) Determine whether there is respiratory failure based on PCO2 and PO2

1. Normal PO2 value: 80~100mmHg

2. When PO2 < 60 mmHg, it is the clinical experimental basis for respiratory failure and is also an indication for intubation and mechanical ventilation.

3. When PO2<60mmHg and PCO2 is normal, it is type I respiratory failure;

Common causes: Ventilation dysfunction

Solution: Correct hypoxemia, maintain normal airway, etc.

4. When PO2<60mmHg and PCO2>50mmHg, it is type II respiratory failure.

Common causes: Alveolar hypoventilation

Solution: Mechanical ventilation, etc.

(IV) Determine whether there is hypoxia by looking at oxygen and index

1. Oxygen index = oxygen partial pressure/oxygen concentration

2. Normal value of oxygenation index: >300

3. Abnormal oxygen and index: <300, common causes: acute lung injury, ARDS

ARDS oxygen and index classification: mild 200~300; moderate 150~200; severe <150 (intubation and mechanical ventilation are required)

(V) Metabolic index: Standardized alkali excess (SBE) and standard bicarbonate (SBC)

1. Normal value of SBE: ±2~3mmol/L

2. Normal SBC value: 21~24mmol/L

The higher these two values ​​are, the more alkaline it is, and the lower they are, the more acidic it is.

(VI) Look at electrolytes

⑴ Potassium

① K+: Normal value: 3.5~5.5mmol/L

② K+>5.5mmol/L is high potassium

Clinical manifestations: Cardiac arrest

Common causes: excessive intake, metabolic abnormalities, etc.

Solutions: intravenous push of calcium gluconate, intravenous drip of sodium bicarbonate, intravenous drip of glucose + insulin, hemodialysis, etc.

③ K+<3.5mmol/L is low potassium

Clinical manifestations: muscle weakness, fatigue, arrhythmia, abdominal distension, etc.

Common causes: insufficient intake, excessive loss

Solution: Eat more potassium-rich foods such as bananas, oranges, etc., take potassium water orally, or intravenously drip potassium water, etc.

Note: Five things not to do with potassium supplementation: 1. Not too early: potassium supplementation should be done when urine volume is ≥40ml per hour 2. Not too fast: <60ml per hour

3. It is not suitable to be injected intravenously 4. The concentration should not be too high: ≤0.03% 5. The total amount should not be too large: 4~8g potassium supplement per day]

⑵Sodium [Osmotic pressure response]

① Na+ normal value: 135~145mmol/L

② When Na+>145mmol/L is high sodium

Common causes: insufficient water intake, excessive water loss, large amounts of diuresis, etc.

Treatment: Follow the doctor's advice to feed warm water through nasogastric tube, change all the rehydration fluid with 0.9% sodium chloride to 5% glucose, hemodialysis, CRRT, etc. when necessary.

③ When Na+<135 is low sodium

Common causes: loss of large amounts of digestive fluid, use of potassium-sparing and sodium-excreting diuretics, etc.

Treatment: Oral administration of concentrated sodium, replacement of 5% glucose solution with 0.9% sodium chloride solution if necessary, etc.

⑶ Chlorine

① Normal value of Cl-: 98~106mmol/L

② When Cl->106mmol/L is high chlorine

Common causes: renal insufficiency, hypertonic dehydration, etc.

③ When Cl-<98mmol/L is low chlorine

Common causes: vomiting, loss of a large amount of body fluid, etc.

Note: [Generally, high sodium and high chloride, low sodium and low chloride appear at the same time]

⑷ Calcium

①C a2+ normal value: 2.1~2.6mmol/L

② When Ca2+ is reduced, common causes include: convulsions, pancreatitis, etc. → Treatment: Eat more calcium-rich foods such as shrimp, calcium supplements, etc.

⑸ Lactic acid (to determine oxygen metabolism)

①Normal lactate value: <2mmol/L

②When lactate level>4mmol/L, it is a critical condition, which is especially important for the treatment of critically ill patients such as myocardial infarction and heart failure.

③ Common causes of increased lactic acid: sepsis, shock

④Treatment : eliminate the cause, use antibiotics, debridement, mechanical ventilation, CRRT, etc.