ABG interpretation in the context of hypothermia The interpretation of blood gas data relies on certain standard variables being in place. Apart from atmospheric pressure (which everybody always assumes is 760 mmHg), theother  most important variable is temperature. Temperature changes the physicochemical properties of water, influencing solubility of gases and the autoionisation of water into H3O+ and OH-. Influence of temperature on pH and gas solub...

ABG interpretation in the context of normal pregnancy The college examiners seem to love nothing more than to throw seemingly normal-looking ABG results at the candidates, with the respiratory acidosis disguised by the effects of pregnancy. There are several such examples: Question 6.2 from the first paper of 2013Question 6.1 from the second paper of 2012Question 9.2 from the second paper of 2011Question 7.3 from the first paper of 2009 These ...

A systematic approach to ABG interpretation For blood gas interpretation, there is an official "Diagnostic Sequence" available in Oh's Manual. It is presented in T.J. Morgan's chapter for Oh's Manual (Chapter 92, "Acid base balance and disorders"); an owner of the Manual may find it on page 943 of the 7th edition. One expects that the college examiners, being the authors of the Manual, expect their exam candidates to use this ritualised approach. Therefo...

Sources of error in blood gas analysis Essentially, this chapter is a short list of reasons as to why your ABG (or venous biochemistry)  measurement may be wrong, i.e. not reflective of what is happening in the patient. In 99% of cases, it is a problem with the collection storage and transport of the sample, because these are factors which are subject to human input and thus human error. The self-calibrating blood gas analyser is a dutiful and dependable serv...

How the blood gas analyser measures ABG variables Question 9.1 from the second paper of 2008 asks of the bewildered candidates: "Outline  how pH, PCO2 and PO2  are measured in a blood gas analyser and briefly state the underlying principle behind  each of those measurements." The pass rate of 47% was pleasantly surprising, suggesting that many (if not all) of the candidates arose from an intellectually robust anaesthetic background. Judgi...

CLINICAL PICTURE| VOLUME 395, ISSUE 10235, P1516, MAY 09, 2020 Myocarditis in a patient with COVID-19: a cause of raised troponin and ECG changes Denis Doyen, Pamela Moceri, Dorothée Ducreux, et al Lancet 2020; 395: 1516 A 69-year old man, from Lombardy, Italy, was admitted to our unit because of acute respiratory distress syndrome that required mechanical ventilation; he was in Nice, France, on holiday. He had previously been fit and well; he had a history of...

Massive Splenomegaly from Disseminated Mycobacterium avium–intracellulare Infection Lucas R. Massoth, Abner Louissaint, Jr. N Engl J Med 2020; 382:1041DOI: 10.1056/NEJMicm1905550 A 29-year-old man with HIV infection presented with abdominal pain and drenching nights sweats. Computed tomography of the abdomen revealed massive splenomegaly caused by disseminated Mycobacterium avium–intracellulare infection.

IMAGES IN CLINICAL MEDICINE Skin Discoloration from Amiodarone Robert P. Murphy and Michelle Canavan N Engl J Med 2020; 382:e5DOI: 10.1056/NEJMicm1906774 An 81-year-old man with a history of atrial fibrillation and hypertension presented to the emergency department after a fall. His medications were apixaban, ramipril, bisoprolol, amlodipine, and amiodarone. Physical examination revealed blue and gray pigmentation, sometimes referred to as ceruloderma, wit...

IMAGES IN CLINICAL MEDICINE Crazy Paving in Pulmonary Alveolar Proteinosis Brian W. Allwood and Sami Bennji N Engl J Med 2020; 382:275DOI: 10.1056/NEJMicm1908563 A 34-year-old man with a 20-pack-year smoking history presented to the emergency department with a 4-month history of progressively worsening dyspnea and nonproductive cough. The oxygen saturation was 65% while the patient was breathing ambient air. He appeared to have dyspnea at rest, his fi...

IMAGES IN CLINICAL MEDICINE Crepitus and Subcutaneous Emphysema Yehia Saleh and Ahmad Alratroot N Engl J Med 2020; 382:e1DOI: 10.1056/NEJMicm1907386 An 86-year-old woman with a history of severe emphysema presented to the emergency department with sudden-onset shortness of breath. Two weeks earlier, she had been treated for community-acquired pneumonia that was complicated by a pneumothorax on the right side, leading to the temporary insertion of a chest t...