| A-Fib | Atrial fibrillation |
| AAA | Abdominal aortic aneurysm |
| ABG | Arterial blood gas(es) |
| ACA | Anterior cerebral artery |
| ACE | Angiotensin converting enzyme |
| ACEI, ACE-I | Angiotensin converting enzyme inhibitor |
| ACh | Acetylcholine |
| ACLS | Advanced cardiac life support |
| ACS | Acute coronary syndrome |
| ACT | Activated clotting time |
| ACTH | Adrenocorticotropic hormone |
| ADH | Antidiuretic hormone |
| ADP | Adenosine diphosphate |
| AED | Automated external defibrillator |
| AF, Afib | Atrial fibrillation |
| AH | Autonomic hyperactivity |
| AHA/ACC | American Heart Association/American College of Cardiologists |
| AI | Aortic insufficiency |
| AICD | Automated implantable cardiac defibrillator |
| ALI | Acute lung injury |
| ALT | Alanine aminotransferase |
| AMI | Acute myocardial infarction |
| ANH | Acute normovolemic hemodilution |
| ANS | Autonomic nervous system |
| APAP | Acetaminophen |
| aPTT | Activated prothrombin time |
| AR | Aortic regurgitation |
| ARB | Angiotensin receptor blocker |
| ARDS | Acute respiratory distress syndrome |
| ARF | Acute renal failure/acute respiratory failure |
| AS | Aortic stenosis |
| ASA | American Society of Anesthesiologists/Acetylsalicylic acid |
| ASAP | As soon as possible |
| ASD | Atrial septal defect |
| ASIS | Anterior-superior iliac spine |
| ASRA | American Society of Regional Anesthesia |
| AST | Aspartate aminotransferase |
| ATLS | Advanced trauma life support |
| ATN | Acute tubular necrosis |
| ATP | Adenosine triphosphate |
| AV block | Atrio-ventricular block |
| AV node | Atrio-ventricular node |
| AVF | Arterio-venous fistula |
| AVM | Arterio-venous malformation |
| AVNRT | Atrio-ventricular nodal reentrant tachycardia |
| BBB | Bundle branch block |
| BID | Twice a day |
| BIPAP, BiPAP | Bilevel positive airway pressure |
| BLS | Basic life support |
| BMI | Body mass index |
| BMR | Basal metabolic rate |
| BMS | Bare metal stent |
| BNE | Bilateral neck exploration |
| BNP | Brain natriuretic peptide |
| BP | Blood pressure |
| BPH | Benign prostate hypertrophy |
| C1-INH | C1-esterase inhibitor |
| CA | Carotid artery |
| CABG | Coronary artery bypass graft |
| CAD | Coronary artery disease |
| CAR | Cerebral autoregulation |
| CASP | Carotid artery stump pressure |
| CBC | Complete blood count |
| CBF | Cerebral blood flow |
| CBV | Cerebral blood volume |
| CEA | Carotid endarterectomy |
| CHD | Congenital heart disease |
| CHF | Congestive heart failure |
| CI | Cardiac index |
| CIRCI | Critical illness–related corticosteroid insufficiency |
| CK | Creatine kinase |
| CM | Cardiomyopathy |
| CMRO2 | Cerebral metabolic rate of oxygen consumption |
| CMV | Controlled mechanical ventilation/Cytomegalovirus |
| CN | Cranial nerve |
| CNB | Central neuraxial block |
| CNS | Central nervous system |
| CO | Cardiac output/carbon monoxide |
| COPD | Chronic obstructive pulmonary disease |
| COX | Cyclo-oxygenase |
| CPAP | Continuous positive airway pressure |
| CPB | Cardiopulmonary bypass |
| CPD | Cephalo-pelvic disproportion |
| CPK | Creatine phosphokinase |
| CPNB | Continuous peripheral nerve block(s) |
| CPP | Cerebral perfusion pressure |
| CPR | Cardio-pulmonary resuscitation |
| Cr | Creatinine |
| CRP | C-reactive protein |
| CRPS | Complex regional pain syndrome |
| CRRT | Continuous renal replacement therapy |
| CSE | Combined spinal-epidural |
| CSF | Cerebrospinal fluid |
| CSHT | Context-sensitive half-time |
| CVA | Cerebrovascular accident |
| CVC | Central venous catheter |
| CVL | Central venous line |
| CVP | Central venous pressure |
| CVVH | Continuous veno-venous hemofiltration |
| CVVHD | Continuous veno-venous hemodialysis |
| CVVHDF | Continuous veno-venous hemodiafiltration |
| CXR | Chest radiograph |
| D/C | Discontinue, discontinuation, discharge, discharged |
| DA | Dopamine |
| DBP | Diastolic blood pressure |
| DDAVP | Desmopressin |
| DES | Drug-eluting stent |
| DI | Diabetes insipidus |
| DIC | Disseminated intra-vascular coagulation |
| DKA | Diabetic ketoacidosis |
| DL | Direct laryngoscopy |
| DLCO | Diffusion capacity of the lung for carbon monoxide |
| DLETT | Double-lumen endotracheal tube |
| DLT | Double-lumen endotracheal tube |
| DM | Diabetes mellitus |
| DT | Delirium tremens |
| DTR | Deep tendon reflex |
| DVT | Deep vein thrombosis |
| EBV | Ebstein-Barr virus |
| ECF | Extracellular fluid |
| ECG | Electrocardiogram |
| ECMO | Extra-corporeal membrane oxygenation |
| ECT | Electroconvulsive therapy |
| EEG | Electroencephalogram |
| EF | Ejection fraction |
| EGD | Esophagogastroduodenoscopy |
| EJ | External jugular (vein) |
| EKG | Electrocardiogram |
| EMG | ...