What causes Hypoxia

Clinical Causes of Hypoxia During Anesthesia

Every doctor should know the answer to the basic question What causes Hypoxia . Factors responsible:

1. Preanaesthesia factors

• Poor physiological status

• Drug intake

• Premedication with narcotics and sedatives depress the respiration

• Decreased compensatory mechanism due to any cause

2. Decreased partial pressure and concentration of the inspired oxygen in anesthesia breathing mixture.

3. Mechanical factors

• Flow meter defects

• Inaccurate reading at low flow rates

• Pressure gauge defects

• Exhausted oxygen cylinders

• Obstruction due to kinking of corrugated tubes

4. Inspired ventilatory inefficiency

• Airway obstruction upper or lower

• Hypoventilation due to any cause

• Decreased effective alveolar ventilation

• Increased shunting

• Obstructive airway diseases

• Types of operative procedure: thoracic operations, 50% shunt; Abdominal operations, 35% shunt

• Poor pattern of ventilation

• Lack of periodic hyperventilation (sigh)

Impaired ventilation

• Increased shunting

• Increased dead space

Deficient oxygen loading

• Metabolic or respiratory acidosis

• Low levels of hemoglobin

• Pulmonary edema

Decreased transport

• Hypovolaemia due to any cause

• Blood loss due to any cause

• Fluid loss due to any cause

5. Cardio circulatory inability

• Pre-existing compensatory disability

• Decreased cardiac output due to any cause

• Myocardial disease

• Metabolic acidosis due to any cause

• Negative iontropic drugs

• Myocardial depression due to drugs or acidosis

• Interference with venous return

• Circulatory depression due to blood loss or due to sympathetic analysis

• Excessive pressure

• Positive pressure ventilation

6. Impaired tissue delivery

• Impaired regional blood flow

• Increased utilization due to acidosis

• Decreased cerebral blood flow

• Excess tissue lactate production and hypocalcaemia

This is a brief discussion of what causes hypoxia, if you have any more questions fell free to ask a doctor.

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