WBR1089
| Author | [[PageAuthor::Mohamed Moubarak, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 3 |
| Main Category | MainCategory::Primary Care Office |
| Sub Category | SubCategory::Cardiovascular, SubCategory::Electrolytes |
| Prompt | [[Prompt::A 57-year-old male comes to your office for follow up. He is a newly diagnosed lung cancer patient, and undergoes his first round of cisplatin. He has insignificant past medical history. On examination, his BP is 100/80 mmHg, irregular heart rate 50 beat per minute, temperature 37 C (98.6 F), respiratory rate is 17/minute. His laboratory tests are:
Sodium 135 Potassium 6.8 Chloride 108 CO2 20 BUN 35 Creatinine 3.4 Glucose 152 Calcium 7.5 What would be the most likely finding on this patient’s EKG?]] |
| Answer A | AnswerA::Shortened P-R segment |
| Answer A Explanation | [[AnswerAExp::Incorrect
Hyperkalemia does not cause shortened P-R segment. The most common causes of shortened P-R segment include AV junctional rhythm, and Wolff-Parkinson-White syndrome.]] |
| Answer B | AnswerB::Abnormally prominent U waves |
| Answer B Explanation | [[AnswerBExp::Incorrect
Abnormally prominent U waves are characteristically seen in severe hypokalaemia. U waves are prominent if > 1-2mm or 25% of the height of the T wave. The most common cause of prominent U waves is bradycardia.]] |
| Answer C | AnswerC::Widened QRS complexes |
| Answer C Explanation | [[AnswerCExp::Correct
Hyperkalemia will produce significant EKG abnormalities, including peaked T waves and widened QRS complexes]] |
| Answer D | AnswerD::Flattened T waves |
| Answer D Explanation | [[AnswerDExp::Incorrect
Flattened T waves may indicate myocardial ischemia, or hypokalemia.]] |
| Answer E | AnswerE::Atrial fibrillation |
| Answer E Explanation | [[AnswerEExp::Incorrect
Hyperkalemia will produce significant EKG abnormalities, including peaked T waves and widened QRS complexes. Bradycardia and irregular heart rate on physical examination are suggestive of the cardiac effects of hyperkalemia.]] |
| Right Answer | RightAnswer::C |
| Explanation | [[Explanation::The patient has tumor lysis syndrome. The destruction of malignant cells by chemotherapeutic agents will lead to the release of intracellular contents, including potassium, phosphorus, and uric acid (from nucleic acids). This can result in hyperkalemia, hyperuricemia, and hyperphosphatemia.
Hyperkalemia will produce significant EKG abnormalities, including peaked T waves and widened QRS complexes. The presence of bradycardia and irregular heart rate on physical examination are suggestive of the cardiac effects of hyperkalemia, which can lead to life threatening arrhythmias if not managed properly. |
| Approved | Approved::No |
| Keyword | [[WBRKeyword::Tumor lysis syndrome]] |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |