IS PRESSING ON THE ABDOMEN A METHOD OF DIAGNOSING HYPOVOLAEMIA IN THE NEONATAL INTENSIVE CARE UNIT?

J. Tooley, M. Thoresen. University of Bristol, Bristol, UK

Aim: Assessment of detailed cardiovascular parameters in the newborn is difficult. Hypotension is commonly related to hypovolaemia and/or myocardial dysfunction. Historically it has been taught that blood pressure (BP) response to pressure over the right upper quadrant (RUQ) of the abdomen (over the liver) in hypotensive infants may help differentiate between the two. If BP rises significantly during this “test”, hypovolaemia rather than myocardial dysfunction is the cause. In theory the liver contains reserves of circulating blood (∼10 ml/kg) and the test leads to a temporary autotransfusion. This test is not validated.

Methods: Two newborn pigs (∼1.5 kg) were anaesthetised and ventilated in accordance with Home Office guidelines. An umbilical artery catheter was inserted to measure BP. Each test consisted of measuring BP response to RUQ abdominal pressure performed for 5 s in order to depress the abdominal wall by 3 cm. Over 6 h 10 ml/kg aliquots of blood were removed up to 30 ml/kg and then sequentially replaced until normovolaemic. This was then followed by 10 ml/kg additions of 0.9% saline up to 30 ml/kg above normal circulating volume. The response to this test was determined twice at each of these points as well as during myocardial ischaemia (induced by reducing inspired oxygen to 8%).

Results: 40 “tests” were analysed. Median BP (mm Hg (interquartile)) results are shown in the table. There was a consistent significant rise in BP (∼30%, p<0.01) during these tests. The BP rise was no different during hypovolaemia, hypervolaemia or hypoxia.

Conclusion: Pressing on the abdomen to assess cardiovascular status in the newborn is unhelpful. BP response to pressure over the liver does not provide information that can be used to determine overall circulating volume. Giving extra boluses of fluid purely in response to this …