Thyrotoxicosis — FRCA Primary MCQ

Correct answer: D — High oxygen consumption and low FRC shorten safe apnoea time

Thyroid hormone increases metabolic rate and adrenergic responsiveness. Reduced haemoglobin lowers arterial oxygen content is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Pain and temperature ascend in the spinothalamic tract is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Left ventricular coronary perfusion occurs mainly in diastole is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Increased preload increases stroke volume through fibre stretch is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. In Primary FRCA physiology, the correct answer is usually the variable that best explains the observed change in the anaesthetised patient.

Reference: West's Respiratory Physiology; Ganong Review of Medical Physiology; Primary FRCA textbooks