An audit of insulin stress tests performed by an individual endocrine specialist nurse - a safe and reliable procedure
D Wright, M Shah & SR Peacey
The insulin stress test (IST) continues to be considered a potent test for assessing ACTH and GH reserve. The test has been shown to be safe when performed in an experienced unit. Many endocrine nurse specialists independently perform IST's using appropriate protocols. We audited all consecutive IST's performed by an individual endocrine specialist nurse in our unit. IST was not performed if patients had a history of seizure, ischaemic heart disease or were > 60 yrs. All patients received verbal and written information about the test. The endocrine nurse remained in attendance at all times but without direct medical supervision. Fifty-seven patients; 23M, 34F, median (range) age 41 (16 - 60) yrs underwent a total of 78 IST's over a 54 month period. 76 / 78 patients received intravenous soluble insulin 0.2 iu / kg. Laboratory measured glucose nadir was 1.2 (0.4 - 3.2) mmol / l and occurred at t=30 minutes in 88% of tests. Despite the use of a relatively high insulin dose, 7 / 78 (9%) of tests failed to achieve a glucose nadir of 2.2 mmol/l or less, often due to co-existing diabetes mellitus. Bedside glucose measurement was used to assess adequacy of the hypoglycaemic stimulus. A significant correlation was found between the bedside glucose nadir and laboratory glucose nadir (r = 0.70; p<0.0001). Following adequate hypoglycaemia, oral glucose was given in 25% of cases and intravenous glucose on only one occasion. No seizures or cardiac symptoms occurred during these tests. Medical support was only required during one IST and related to a prescribing issue. The IST when performed by an experienced endocrine specialist nurse remains a reliable and safe procedure.