Unnecessary investigations in patients with acute pancreatitis: Arterial blood sampling and serum biochemistry

Background: Most patients admitted with acute pancreatitis undergo arterial blood gas sampling (ABG) to calculate the modified Glasgow score (MGS) and serum amylase and liver function tests (LFTs) are requested frequently during admission. This study aims to assess the necessity of these investigations. Materials & methods: A retrospective study of all patients attending a district general hospital with a diagnosis of acute pancreatitis (AP) between November 2005 and November 2006 was performed. Patients were identified from clinical coding data, excluding those with serum amylase levels of <550iU/l thereby increasing the likelihood of correct diagnosis. Demographic data and ABG reports were retrieved from the case notes. Criteria were defined for necessity of amylase and LFT requests. Results: Data were retrieved for 63 patients with 227 amylase requests, 329 LFT requests, 95 ABGs and 80 MGSs. Eight ABGs were found to have PaO2 values less than 8kPa, a result that could be predicted in all cases by pulse oximeter-derived oxygen saturations of less than 95%. When the MGS excluding the PaO2 parameter was two, only one patient out of 22 (4.5%) was upgraded to a score of three due to a PaO2 of less than 8 kPa and this could have been predicted by pulse oximeter-derived oxygen saturations of 92%. The MGS excluding the PaO2 parameter was always three or more in cases where acid-base disturbance exhibited more than a mild metabolic acidosis. One hundred and sixty-two unnecessary amylase requests and 168 unnecessary LFT requests were made according to our defined criteria, equating to 2.6 unnecessary amylase requests and 2.7 unnecessary LFT requests per admission at a cost of £83.40 (£1.32 per admission). Conclusions: We propose not performing ABGs if the MGS excluding the PaO2 component totals two or less. Clinical judgment would have to be exercised. Unnecessary serum biochemistry requests are frequent but at little financial expense.