Ultradian cardiac rhthms in surgical intensive care unit patients

Several reports have suggested that heart rate may be regulated by an ultradian biological rhythm with a period of about 90--100 min. Blood pressure and heart rate were collected from 10 Surgical Intensive Care patients at 5-min intervals and analyzed by computer. No 90-min rhthms were found, indicating this rhythm has no significant influence on heart rate or blood pressure in postsurgical patients.