Academic Medical Centers; Adolescence; Adult; Aged; Aged, 80 and Over; Apache; Arterial Catheters; Chi Square Test; Correlational Studies; Critical Care Nursing; Descriptive Research; Descriptive Statistics; Female; Intensive Care Units; Length of Stay; Male; Medical Records; Middle Age; Questionnaires; Record Review; Retrospective Design; Spearman's Rank Correlation Coefficient; United Kingdom; Human