The trouble with blood pressure cuffs

Case 1

A 42 year old man with an estimated weight of 120 kg was admitted to the intensive care unit after a road crash. A high speed deceleration injury resulted in bilateral lung contusions, a pneumothorax, several bilateral rib fractures, and a wedge fracture of T12 and fractured spinous process of C2.

He required sedation and ventilatory support because of respiratory failure and was transferred to the intensive care unit. He was initially cardiovascularly stable, with a blood pressure of 127/74 mm Hg (measured via a left brachial arterial line) and central venous pressure of12 cm H₂O. Blood pressure measurements taken from the invasive arterial system were persistently low, and he subsequently needed a norepinephrine infusion to maintain his mean arterial pressure and cerebral perfusion pressure. Reviewing the patient later that day, we noted that the blood pressure had been recorded as 135/75 mm Hg even though the invasive reading was 83/47 mm Hg. A non-invasive blood pressure cuff had been placed on the right upper arm, and all documented readings for that day had been taken from the cuff. The left brachial arterial line showed a good trace, and we were able to aspirate blood easily from the line. On closer inspection of the blood pressure cuff we noticed that a “small” …