About Visual fields

 A patient presents with a bilateral homonymous quadranopsia involving the right upper visual field. Which of the following represents the MOST likely anatomic location of the abnormality?

• (A) Prechiasmal, right side
• (B) Optic chiasm
• (C) Postchiasmal, prethalamic, left side
• (D) Occipital lobe, right side
• (E) Occipital lobe, left side

The answer is E.

Homonymous visual field cuts imply a postchiasmal location of the abnormality because this is the first point where fibers from the same visual field of both eyes join. Fibers further divide between the thalamus and occipital lobe into upper and lower quadrant visual fields. The most common location for quadranopsia defects is the occiptal lobe. Stroke, tumor, and atypical migraine may present with quadranopsia.
Visual fields are named from the perspective of the patient, i.e., the right visual field corresponds to the left side of the retina. Therefore, a right-sided visual field cut involves the left-sided neurologic tracks.

Preoperative dose of antibiotic

When vancomycin is used as a preoperative prophylactic antibiotic, it should be administered within ______ minutes of the start of surgery.

A) 15
B) 30
C) 60
D) 120
E) At the time of incision

Answer and Discussion

The answer is D.
Ideally, a preoperative dose of antibiotic should provide a sufficient antibiotic serum level throughout the surgery to combat organisms most likely to cause a site infection. It is recommended that the first dose be timed to occur within 60 minutes before the surgical incision is made. If a fluoroquinolone or vancomycin is chosen for prophylaxis, the first dose should be administered within 120 minutes of the start of surgery. If the surgery involves the use of a tourniquet (e.g., hip or knee arthroplasty), the antibiotic infusion should be completed before inflation of the tourniquet. For most surgeries, it is recommended that use of prophylactic antibiotics end within 24 hours after surgery.

Mindmap for Appendicitis

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