CPSP IMM Medicine common mistakes
CPSP IMM Medicine · Understand the traps and how to avoid them.
In cardiology vignettes, treating any ST depression on the presenting ECG as automatically indicating acute coronary syndrome and jumping to antiplatelet/anticoagulant therapy, without first checking whether the depression is rate-related, digoxin-related, or part of a chronic pattern.
Candidates pattern-match on the phrase 'chest pain' plus 'ST depression' and stop reading the rest of the stem, missing the heart rate, medication list, or prior ECG comparison that reframes the finding.
What to do instead
Before committing to an ACS pathway, force yourself to answer three questions from the stem: what is the heart rate and rhythm, what drugs is the patient on, and is there a prior ECG described. If the depression is rate-related or the rhythm is uncontrolled AF, treat the rate/rhythm first and re-evaluate.
Choosing a fixed-dose diuretic or vasodilator regimen for acute decompensated heart failure without first classifying the patient by volume status (wet/dry) and perfusion (warm/cold).
The stem offers a tempting single 'best initial step' and candidates pick diuresis reflexively, forgetting that a cold and hypoperfused patient may need inotropic support or careful afterload reduction before aggressive diuresis.
What to do instead
Write W/D, W/W, C/D, or C/W in the margin of the question before reading the options. Then match the intervention to that quadrant: diuresis for wet-warm, inotrope or vasodilator for cold, and reassess perfusion before escalating diuresis.
Interpreting a widened alveolar-arterial gradient or a low PaO2 in isolation as the answer in a dyspnea vignette, instead of calculating the gradient and comparing it with the expected value for the patient's age and FiO2.
Candidates memorize that a high A-a gradient means 'shunt or V/Q mismatch' but do not actually compute the expected gradient or account for supplemental oxygen, so they misclassify hypoventilation as a gas-exchange problem.
What to do instead
On every blood gas question, calculate PAO2 = FiO2 x (Patm - 47) - PaCO2/0.8 and subtract PaO2. A normal gradient with hypercapnia points to hypoventilation (e.g., opioid, neuromuscular weakness); a raised gradient points to parenchymal or vascular disease.
Managing an asthma or COPD exacerbation with bronchodilators alone and omitting systemic corticosteroids, or giving antibiotics to every exacerbation regardless of whether sputum purulence and change in sputum volume are present.
The dramatic improvement after a beta-agonist in the stem pulls attention toward the bronchodilator, and candidates conflate 'exacerbation' with 'infection' by habit.
What to do instead
Build a fixed exacerbation bundle in memory: short-acting bronchodilator, systemic corticosteroid, controlled oxygen to a target saturation, and antibiotics only when there is increased sputum purulence plus increased volume or dyspnea. Check the stem for those three Anthonisen-type criteria before choosing antibiotics.
Attributing upper gastrointestinal bleeding to a peptic ulcer and stopping there, without screening the stem for cirrhosis stigmata, NSAID or anticoagulant use, and hemodynamic status that would change resuscitation priorities.
Ulcer is the most statistically common cause, so candidates anchor on it and skip the risk stratification and resuscitation steps that the question is actually testing.
What to do instead
For every GI bleed stem, first decide stability (tachycardia, orthostasis, hemoglobin), then risk-stratify with a validated score concept (e.g., Glasgow-Blatchford features), then choose the next diagnostic step. Varices, NSAID ulcers, and Mallory-Weiss each have distinct clues; name the clue that supports your choice.
Diagnosing acute pancreatitis on lipase elevation alone without requiring two of the three standard criteria (characteristic pain, enzyme elevation above roughly three times the upper limit of normal, or imaging findings).
The word 'lipase' in the stem reads as diagnostic, and candidates forget that mild elevations occur in renal failure, bowel ischemia, and other abdominal conditions.
What to do instead
State the two criteria you are using before selecting an answer. If only a mildly raised lipase is described, look for the alternative diagnosis in the options rather than defaulting to pancreatitis.
Correcting hyperglycemia in a diabetic emergency without first distinguishing diabetic ketoacidosis from hyperosmolar hyperglycemic state by checking ketones, pH, bicarbonate, and effective osmolality.
Both present with hyperglycemia and dehydration, and candidates memorize a single fluid-plus-insulin protocol rather than the branch points that determine whether insulin is needed immediately and how aggressively fluids are given.
What to do instead
On every hyperglycemia question, compute the anion gap and check ketones and pH. DKA needs isotonic fluid, insulin, and potassium replacement with attention to total-body potassium; HHS is dominated by profound free-water deficit and often needs fluid resuscitation before insulin. State which entity the labs support.
Treating a rising creatinine as acute kidney injury requiring fluids without checking the urine sodium, fractional excretion of urea, and volume status to separate prerenal, intrinsic, and postrenal causes.
Fluids feel safe and are the reflex answer, but in cardiogenic or nephrotoxic injury they may be wrong, and candidates skip the postrenal screen (bladder scan, obstruction risk) entirely.
What to do instead
Run a fixed sequence: is there obstruction (post-void residual, hydronephrosis risk factors), is it prerenal (BUN/creatinine ratio, urine sodium, response to fluid challenge), or intrinsic (sediment, eosinophils, prolonged oliguria). Choose the answer that matches the category, not the one that sounds most supportive.
Missing secondary hypertension or a renovascular clue in a hypertension vignette by not checking for hypokalemia, an abdominal bruit, or onset before age 30 or after age 55.
The stem gives a blood pressure number and candidates go straight to picking an antihypertensive class, ignoring the features that signal an underlying cause requiring different workup.
What to do instead
Before selecting a drug, scan the stem for age at onset, potassium, creatinine, and bruit. If any are abnormal, answer the workup question (aldosterone-renin ratio, renal artery imaging) rather than the treatment question.
Choosing a thyroid or adrenal test result as diagnostic without accounting for confounders such as biotin, illness, pregnancy, or exogenous steroids that alter binding proteins and assay results.
Candidates memorize 'high TSH plus low free T4 equals primary hypothyroidism' but do not apply the exceptions, and the exam deliberately includes stems with non-thyroidal illness or assay interference.
What to do instead
For each endocrine lab question, ask what else could move this value: acute illness, estrogen or pregnancy raising binding globulins, biotin interference, or exogenous hormone. If the stem mentions a confounder, the correct answer usually involves repeating the test or using a different assay rather than treating.