Point-of-Care Ultrasound is a method of performing a rapid clinical ultrasound, with the aim of responding to a clinical question immediately. This is not an ultrasound performed systematically as the radiologists do, nor does it pretend to replace it. It is useful in some kind of screening (abdominal aortic aneurysm) and is of special interest in ultrasound-guided procedures (joint infiltration by injection). It allows to adapt the derivations, minimising the uncertainty, ruling out certain pathologies due to its high diagnostic precision. It can also lead to overdiagnosis, if the examinations carried out are not limited to the organs on which our clinical suspicion is based. Ultrasound is one tool more in the diagnostic process, but its use must be limited to certain clinical situations. Its use in early detection of prevalent diseases in Primary Care should be properly evaluated. On the other hand with more evidence of a high diagnostic accuracy in a large list of pathological conditions.
Background
Corrected carotid flow time (CFTc) and carotid blood flow (CBF) are sonographic measurements used to assess fluid responsiveness in hypotension. We investigated the impacts of mechanical ventilation on CFTc and CBF.
Materials and methods
Normotensive patients undergoing cardiac surgery were prospectively enrolled. Carotid ultrasound (US) was performed pre and post-intubation. Post-intubation measurements took place after the initiation of mechanical ventilation. To measure CFTc and CBF, a sagittal carotid view was obtained with pulse wave-Doppler (maximum angle 60°). CFTc was calculated with the Bazett formula (CFTc = systolic time/√cycle time). CBF was calculated using CBF (mL/min) = area (cm
2
) x time average mean velocity (TAMEAN) (cm/sec) x 60 (sec/min). The maximum carotid diameter was measured at the level of the thyroid.
Results
Twenty patients were enrolled. Mean CFTc pre-intubation was 328 ms (SD 43.9 ms) compared to CFTc post-intubation 336 ms (SD 36 ms). There was no significant difference between pre and post-intubation CFTc (mean differences=-0.008; t(19)=-0.71, p=.49). Mean CBF pre-intubation was 487 mL/min (SD 176 mL/min) compared to CBF post-intubation 447 mL/min (SD 187 mL/min). There was no significant difference between pre and post-intubation CBF (mean differences= 40; t(19)=1.24, p=.23).
Conclusions
In this study of normotensive patients, there were no detected differences in CFTc or CBF pre and post-intubation with mechanical ventilation.
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