Clinical Procedures - Carotid Sinus Massage Anatomy and physiology • The carotid sinus is located at the bifurcation of the common carotid artery. It lies just under the angle of the jaw at the level of the thyroid cartilage and contains numerous baroreceptors which coordinate homeostatic mechanisms responsible for maintaining blood pressure • These baroreceptors are innervated by a branch of the glossopharyngeal nerve (CN IX), which relays back to the medulla and modulates autonomic control of the heart and blood vessels. Carotid sinus hypersensitivity • The carotid sinus can be oversensitive to manual stimulation, a condition known as carotid sinus hypersensitivity (also 'carotid sinus syndrome' or 'carotid sinus syncope') • In this condition, manual stimulation of the carotid sinus provokes significant changes in heart rate and/or blood pressure due to an exaggerated response to carotid sinus baroreceptor stimulation. This may result in marked bradycardia, vasodilation, and subsequent hypotension • The patient may complain of episodes of dizziness or syncope related to pressure on the neck (e.g. wearing a tight collar or turning the head quickly) • The underlying mechanism behind this exaggerated response is not fully understood. Carotid sinus massage • Carotid sinus massage is a diagnostic technique used to confirm carotid sinus hypersensitivity and is sometimes useful for determining the underlying rhythm disturbance in supraventricular tachycardia (SVT) • The procedure acts in a similar way to the Valsalva manoeuvre, increasing vagal tone and, therefore, reducing the heart rate Carotid massage is less effective than pharmaceutical management of SVT (verapamil or adenosine) though is still the preferable choice in the young haemodynamically stable patient • This procedure should be performed with caution in the elderly as it may cause disruption of atheromatous plaque disease in the carotid artery and result in stroke. Procedure • Explain the procedure in full to the patient and obtain written consent • If the test is to confirm carotid sinus hypersensitivity, then warn the patient that they may feel like they are going to faint but reassure them it is a controlled procedure • If the test is to determine the underlying rhythm in SVT, explain that they may feel a bit peculiar as the heart rate slows down transiently • Auscultate over the carotids for any bruits: •If present, the procedure will have to be abandoned as the risk of stroke is significant • D Document discussion of risks including failure, arrhythmias, stroke, faint, cardiac arrest • • Secure intravenous access • Ensure that you have ECG monitoring with a recordable rhythm strip • I Ensure access to full resuscitation equipment, including emergency drugs such as atropine and adrenaline • Position the patient supine on a bed with the neck extended and head turned away from the side to be massaged • Whilst watching the ECG monitor (recording on a rhythm strip) gently massage the carotid sinus for 10-15 seconds using circular motions of your hand • If there is no response, switch to the opposite side • I Never massage both carotid sinuses simultaneously • If successful (or 'positive' in the case of sinus hypersensitivity), the heart rate will slow: • This may allow you to determine the underlying rhythm in SVT • Ensure that the patient feels back to normal afterwards.
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