The septic anticoagulated patient — interpreting a multi-test panel

(a) The interpretation and the immediate action for each abnormal result (8 marks).

• Raised lactate — in the Surviving Sepsis Campaign database only lactate above 4 mmol per litre, with and without hypotension, was significantly associated with in-hospital mortality, and mortality was 44.5 per cent with combined lactate above 4 and hypotension. Action: the Hour-1 Bundle — lactate measurement, blood culture, broad-spectrum antibiotics, 30 mL/kg crystalloid for hypotension or lactate of 4 mmol/L or more, and vasopressors for hypotension during or after fluid resuscitation, within 1 hour of sepsis recognition.^[1][19]
• Raised INR on warfarin, in sepsis — sepsis-induced coagulopathy is present in 24 per cent of patients with sepsis and 66 per cent with septic shock, and its scoring systems weigh prothrombin time or INR changes. If he bleeds, life-threatening bleeding requires urgent reversal: prothrombin complex concentrates probably provide an advantage in INR reversal compared with plasma, and 4F-PCC with vitamin K controlled the INR better at 24 hours than 4F-PCC alone in one retrospective study. Without bleeding, the ASH Choosing Wisely list advises avoiding plasma or prothrombin complex concentrate for nonemergent reversal.^{[25][11][20][16]}
• Troponin above baseline and the 99th percentile — the 99th percentile upper reference limit defines myocardial injury, and changing concentrations (deltas) help differentiate acute from chronic injury. Type 2 myocardial infarction occurs secondary to ischaemia from increased demand or decreased supply, with sepsis accounting for 24 per cent in one survey, and needs a rise and fall of troponin with an imbalance unrelated to coronary thrombosis.^[23][24]
• Markedly raised D-dimer — D-dimer is an exclusion test: nonhigh clinical pretest probability with a negative D-dimer excludes DVT or PE in one-third to a half of outpatients, and CT pulmonary angiography is the primary imaging test for PE.^[27]
• Raised potassium with peaked T waves — intravenous calcium salts should be given immediately with ECG changes; calcium stabilises the cardiac cell membrane within 1–3 minutes, insulin and salbutamol shift potassium, only dialysis, binders and loop diuretics remove it, and potassium should be re-evaluated frequently.^[21]
• Lipase above the upper limit of normal — acute pancreatitis needs two of three criteria (upper abdominal pain, amylase or lipase above three times the upper limit of normal, or characteristic imaging). In a hypoperfused patient with abdominal findings, laboratory tests cannot establish mesenteric ischaemia: only CT angiography had adequate accuracy to establish that diagnosis.^[5][26]
• Mildly raised CK — creatine kinase is the biochemical gold standard for diagnosing rhabdomyolysis.^[14]
• Acidaemic venous gas — in ICU patients, central venous pH, bicarbonate, base excess and lactate agreed closely with arterial values.^[29]

(b) Spurious or incidental results and how to confirm (3 marks).

• The potassium — pseudohyperkalaemia can follow mechanical trauma, prolonged tourniquet use or fist clenching during the draw, and point-of-care whole-blood analysers cannot identify haemolysis; haemolysis is one of the most frequent preanalytical errors behind pseudohyperkalaemia. With ECG changes, intravenous calcium is still given immediately.^[21][22]
• The D-dimer — read it through the clinical pretest probability: nonhigh pretest probability with a negative D-dimer excludes DVT or PE, and CT pulmonary angiography is the primary imaging test for PE.^[27]
• The troponin — consider type 2 myocardial infarction from sepsis, and use the delta to separate acute from chronic injury.^[23][24]

(c) The first-hour actions, with doses (4 marks).

• Hyperkalaemia with ECG changes — the KDIGO summary lists intravenous calcium gluconate 3 × 1 g (3 × 10 ml of 10% solution) or calcium chloride 1 g (10 ml of 10% solution); insulin 5 units with 25 g glucose was as effective as nebulised salbutamol 10 mg, the two may be additive, and hypoglycaemia must be watched for.^[21]
• Septic shock — the Hour-1 Bundle, including 30 mL/kg crystalloid for hypotension or lactate of 4 mmol/L or more and vasopressors for hypotension during or after fluid resuscitation.^[19]
• If life-threatening bleeding develops on warfarin — urgent reversal with prothrombin complex concentrate, with vitamin K, dosed per the local protocol.^[11][20]