55 year old female a known case of thryotoxicosis in control posted for abdomino perineal resection during surgery there was sudden drop in B.P., and end tidal CO2 decreased from 40 to 10 mmHg. On auscultation there was a mill wheel murmur, what is the diagnosis –
**Core Concept**
The patient's symptoms are indicative of a condition that affects the cardiovascular and respiratory systems, likely related to a sudden increase in pulmonary vascular resistance or a mechanical obstruction in the respiratory circuit.
**Why the Correct Answer is Right**
The patient's sudden drop in blood pressure and decreased end-tidal CO2 suggest a decrease in cardiac output or a mechanical obstruction in the respiratory circuit. The presence of a mill-wheel murmur, which is a high-pitched, rough, whooshing sound, is characteristic of a patent foramen ovale (PFO) or an atrial septal defect (ASD). However, in the context of surgery, it is more likely related to a mechanical obstruction. The mill-wheel murmur is a result of blood flowing through the obstruction, creating a turbulent flow.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the clinical scenario described.
**Option B:** This option is incorrect because a patent foramen ovale (PFO) or atrial septal defect (ASD) would not typically cause a sudden drop in blood pressure and end-tidal CO2 during surgery.
**Option C:** This option is incorrect because a pulmonary embolism (PE) would likely cause a sudden increase in pulmonary vascular resistance, leading to hypoxia and possibly a decrease in end-tidal CO2, but it would not typically cause a mill-wheel murmur.
**Option D:** This option is incorrect because an aortic dissection would likely cause a sudden increase in blood pressure and possibly a decrease in cardiac output, but it would not typically cause a mill-wheel murmur.
**Clinical Pearl / High-Yield Fact**
A mill-wheel murmur is a characteristic sound of a patent foramen ovale (PFO) or atrial septal defect (ASD), but in the context of surgery, it may also be caused by a mechanical obstruction in the respiratory circuit, such as a kinked endotracheal tube or a misplaced bronchial blocker.
**Correct Answer:** C.