Summary The American Society of Anesthesiologists (ASA) physical status is a tool commonly used to classify a patient's physical fitness before surgery. Since its introduction in 1941 it has undergone very few modifications to improve its reliability and to eliminate subjectivity, despite vast changes in both surgical and anaesthetic technique. We present the history of the ASA physical status and review the literature on its applicability to contemporary anaesthetic practice.

Summary Bleeding during and after surgery ranges from trivial to fatal. Bleeding is in part determined by the patient's coagulation status. The UK National Institute for Health and Care Excellence recommends a pre‐operative clotting test for patients with a history of abnormal bleeding. Anaesthetists are familiar with the prothrombin time assay, used to monitor warfarin effect, but anaesthetists may be less familiar with the activated partial thromboplastin time (APTT), which tests the function of the ‘intrinsic’ clotting pathway. The activated partial thromboplastin time may be prolonged due to contamination, anticoagulant therapy, clotting factor deficiencies, lupus anticoagulant or acquired inhibitors of specific clotting factors. A prolonged activated partial thromboplastin time should lead to: further testing to exclude heparin contamination or therapy, mixing studies to identify factor deficiencies and if necessary dynamic studies, such as the dilute Russell's viper venom time and the Actin FS‐activated partial thromboplastin time, to identify direct factor inhibitors. These tests identify abnormalities and their implications for bleeding, helping anaesthetists and haematologists to manage haemostasis for individual patients.

Heparin exhibits complex pharmacology with a wide variation in individual response. Despite this, heparin is the most commonly used anticoagulant during cardiopulmonary bypass. Heparin resistance in the context of a patient with severe cardiovascular compromise presents a potentially life-threatening challenge. A 31-year-old woman was listed for emergency excision of a massive left atrial myxoma. On induction of anaesthesia, she developed marked cardiovascular instability secondary to mitral inflow obstruction. An initial heparin dose of 600 units.kg-1 produced an activated clotting time of 360 s; however, immediate cardiopulmonary bypass was required. Heparin resistance remained problematic throughout the procedure, with an inadequate response to antithrombin three supplementation. Despite a total dose of 120,000 units of heparin, anticoagulation was fully reversed with 500 mg protamine and there was no subsequent re-heparinisation. Heparin resistance, when coinciding with profound cardiovascular instability, requires a pragmatic response to expedite establishment of cardiopulmonary bypass whilst minimising potential harm. In this case, successful cardiopulmonary bypass was achieved with additional heparin boluses from an alternative batch administered both intravenously and via the bypass circuit. We therefore advocate consideration of this approach as one possible solution to achieving safe entry onto cardiopulmonary bypass in a crisis scenario.