Transthoracic echocardiographic assessment of cardiac output in healthy women at elective caesarean section under spinal anaesthesia with ephedrine hypotension prophylaxis: an observational cohort study

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One of the most common types of anaesthetic used for caesarean section is a spinal anaesthetic. In order for women to be comfortable during the operation a large number of nerves are blocked. In addition to the pain nerves it is very common for other nerves to be affected, including those which are responsible for other types of sensation, movement in the legs and also those which normally help control blood pressure. Significantly low blood pressure in the mother may be associated with side-effects including nausea and vomiting, dizziness and possibly loss of consciousness and in extreme situations the baby may also receive a reduced blood supply from the placenta. For the anaesthetist to provide a safe anaesthetic it is very important to monitor these effects and especially any changes to blood pressure and how the woman’s body responds to it. This is particularly important during the first 5 to 10 minutes after the injection of the spinal anaesthetic. During this period it is usual to closely measure blood pressure, heart rate, the amount of oxygen in the blood and the electrical activity of the heart from an electrocardiogram. Recently, it has also become possible to directly observe the function of the heart relatively quickly and easily via a hand-held ultrasound probe placed on the chest – a transthoracic echocardiogram or TTE. These devices are very similar to those used for obtaining images of the baby during pregnancy. It is known from the use of these devices in other situations, including in pregnant women, that valuable information may be obtained about how the heart is performing. Until now this has not been done in healthy women having a spinal anaesthetic for an elective caesarean section. Hence, the purpose of our study is to document the effects of a standard spinal anaesthetic on the output of the heart by comparing measurements at approximately 10 minutes after the spinal injection with measurements taken immediately before the spinal using TTE. In keeping with usual practice, drugs will be given to help maintain normal blood pressure throughout. Information obtained from this study will be helpful in further understanding the impact of spinal anaesthetics on the cardiovascular system in pregnant women which is likely to help guide anaesthetists to reduce side effects and improve safety.

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