title: Carotid Flow Time Changes With Volume Status in Acute Blood Loss.
abstract: OBJECTIVE
  Noninvasive predictors of volume responsiveness may improve patient care in the emergency department. Doppler measurements of arterial blood flow have been proposed as a predictor of volume responsiveness. We seek to determine the effect of acute blood loss and a passive leg raise maneuver on corrected carotid artery flow time.
  
  
  METHODS
  In a prospective cohort of blood donors, we obtained a Doppler tracing of blood flow through the carotid artery before and after blood loss. Measurements of carotid flow time, cardiac cycle time, and peak blood velocity were obtained in supine position and after a passive leg raise. Measurements of flow time were corrected for pulse rate.
  
  
  RESULTS
  Seventy-nine donors were screened for participation; 70 completed the study. Donors had a mean blood loss of 452 mL. Mean corrected carotid artery flow time before blood loss was 320 ms (95% confidence interval [CI] 315 to 325 ms); this decreased after blood loss to 299 ms (95% CI 294 to 304 ms). A passive leg raise had little effect on mean corrected carotid artery flow time before blood loss (mean increase 4 ms; 95% CI -1 to 9 ms), but increased mean corrected carotid artery flow time after blood loss (mean increase 23 ms; 95% CI 18 to 28 ms) to predonation levels.
  
  
  CONCLUSIONS
  Corrected carotid artery flow time decreased after acute blood loss. In the setting of acute hypovolemia, a passive leg raise restored corrected carotid artery flow time to predonation levels. Further investigation of corrected carotid artery flow time as a predictor of volume responsiveness is warranted.
authors.affiliation: Department of Emergency Medicine, Maine Medical Center, Portland, ME, and Tufts University School of Medicine, Boston, MA. Electronic address: DMackenzie@mmc.org.
authors.forename: David C
authors.initials: DC
authors.lastname: Mackenzie
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Boston, MA.
authors.forename: Noman A
authors.initials: NA
authors.lastname: Khan
authors.affiliation: Department of Emergency Medicine, University of Massachusetts Medical School, Worcester, MA.
authors.forename: David
authors.initials: D
authors.lastname: Blehar
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Boston, MA.
authors.forename: Scott
authors.initials: S
authors.lastname: Glazier
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Boston, MA.
authors.forename: Yuchiao
authors.initials: Y
authors.lastname: Chang
authors.affiliation: Department of Pathology, Massachusetts General Hospital, Boston, MA.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Stowell
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Boston, MA.
authors.forename: Vicki E
authors.initials: VE
authors.lastname: Noble
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Boston, MA.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Liteplo
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D001810:Blood Volume / Q000502:physiology*; D002339:Carotid Arteries / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D006470:Hemorrhage / Q000503:physiopathology*; D006801:Humans; D008297:Male; D011446:Prospective Studies; D016683:Supine Position / Q000502:physiology; D014463:Ultrasonography