Carotid Flow as a Surrogate for Cardiac Output Measurement in Hemodynamically Stable Participants.

OBJECTIVE: Evaluation of common carotid artery (CCA) blood flow can provide valuable information regarding the hemodynamic status of a patient. Utilizing ultrasound, we aimed to evaluate the correlation between cardiac output and different hemodynamic parameters in the CCA, namely systolic carotid flow (SCF), corrected flow time (CFT), and total carotid flow (TCF). METHODS: We studied a pilot sample of 20 healthy volunteers. Hemodynamic parameters were collected in the right CCA and the heart at rest (baseline), 1-leg compression, 2-leg compression, and passive leg raise. Nonparametric Spearman correlation was calculated using STATA 13 software. RESULTS: This study demonstrated the feasibility and safety of the leg compression testing as a hemodynamic maneuver to simulate volume depletion status. We demonstrated a direct correlation between cardiac output and SCF of 0.67 with a P value < 0.001. Interestingly, TCF calculated based on volume-time integral (VTI) in the carotid artery showed positive correlation of only 0.41, with P < 0.06, and it did not reach statistical significance. We also found a positive correlation between CFT and cardiac output at baseline 0.57, with P < 0.001. CONCLUSION: Variations in cardiac preload and the subsequent alterations in cardiac output were directly translatable into variations in the carotid blood flow. This supports the potential for using carotid flow as a surrogate for cardiac output. The most promising parameters were SCF, CFT, and carotid systolic VTI. Further work is needed to validate these correlations and utilize these acquired carotid parameters to guide fluid management and predict fluid responsiveness.

Risk of cardiac arrhythmias and conduction abnormalities in patients with acute myocardial infarction receiving packed red blood cell transfusions.

PURPOSE: Although transfusion has been linked to the development of atrial fibrillation (AF) in cardiac surgical patients, this association has not been investigated in patients with acute myocardial infarction (AMI). Evidence supports an inflammatory mechanism in the development of AF, and red cell transfusions also elicit an inflammatory response. We therefore sought to evaluate whether packed red blood cell transfusion increases the risk of AF, ventricular tachycardia (VT), and other arrhythmias and conduction abnormalities in patients with AMI. MATERIALS AND METHODS: This is a retrospective study on patients with AMI and no prior history of AF, admitted to a critical care area and entered in Project Impact database from 08/2003-12/2007. Primary outcome measures were new-onset cardiac arrhythmias or conduction disturbances. RESULTS: Transfused patients had significantly higher incidences of AF (4.7% vs 1.3%, P = .008), cardiac arrest (9.5% vs 1.7%, P < .001) and heart block (3.4% vs 0.1%, P < .001), and a trend toward a higher incidence of VT (3.4% vs 1.3%, P = .058). Multivariate regression analysis confirmed transfusion as an independent risk factor for "non-lethal" cardiac events (AF/heart block; odds ratio [OR], 4.7 [1.9-11.9]; P = .001), "lethal" events (VT/cardiac arrest; OR, 2.4 [1.1-5]; P = .016), and all cardiac events (OR, 2.8 [1.5-65.1]; P = .001). Transfused patients had significantly longer length of stay (P < .0001) and significantly higher mortality rates than nontransfused patients (OR, 3 [1.7-5.5]; P < .001). CONCLUSIONS: Packed red blood cell transfusion is independently associated with an increased risk of new-onset cardiac arrhythmias and conduction abnormalities in the setting of AMI, even after controlling for traditional risk factors.