Table 1.

Variation in preoperative characteristics across cardiac surgery units.

Characteristic	Units reporting	Overall	Variation across units
			Median	IQR	Range
Patients (n)	16	50,871	2639	2193, 3580	1861, 5983
Age > 75 years (%)	15	25	25	23, 27	15, 34
Female (%)	15	28	29	26, 30	24, 31
Pulmonary disease (%)a	15	14	15	13, 17	6, 20
Neurological dysfunction (%)b	15	3.6	3.5	2.7, 4.0	1.0, 6.5
Creatinine > 0.2 mg/dL (%)c	15	1.7	1.5	0.8, 2.2	0.8, 4.5
Poor left-ventricular function (%)d	15	4.7	4.9	2.9, 5.8	1.3, 9.0
Critical preoperative state (%)e	15	2.5	2.5	1.7, 3.2	1.4, 4.8

^a Defined as long-term use of bronchodilators or steroids for lung disease.

^b Defined as previous stroke.

^c Measured preoperatively.

^d Defined as left-ventricular ejection fraction of ≤ 30%.

^e Defined as ventricular arrhythmia or aborted sudden death, preoperative cardiac massage, preoperative ventilation before anaesthetic room, preoperative inotropes or intra-aortic balloon pump, preoperative acute renal failure (anuria or oliguria < 10 ml/hour)

IQR, interquartile range.