Blood & Lymphoreticular/Immune, Physiology, USMLE Step 1 - Full Vignette with Extended Explanations скачать в хорошем качестве

Blood & Lymphoreticular/Immune, Physiology, USMLE Step 1 - Full Vignette with Extended Explanations

A 30-year-old Rh-negative woman delivers an Rh-positive infant at term with a brief postpartum hemorrhage. Despite uncomplicated prenatal care, a Kleihauer-Betke test reveals fetal red cells in her blood. With her history of medication allergies and current postpartum medications, what critical clinical factors should be considered when determining the optimal Rho(D) immune globulin dose within 72 hours? How does the institution's protocol guide this postpartum management decision? VIDEO INFO Category: Blood & Lymphoreticular/Immune, Physiology, USMLE Step 1 Difficulty: Moderate - Intermediate level - Requires solid foundational knowledge Question Type: Legal Pitfalls Case Type: Pregnant Patient Explore more ways to learn on this and other topics by going to https://endlessmedical.academy/auth?h... QUESTION A 30-year-old gravida 1 para 1 woman delivers a healthy Rh-positive infant vaginally at 39 weeks in December. Prenatal care was uncomplicated and routine vaccines were received. She plans to breastfeed. Allergies include wheezing with NSAIDs, watery eyes with pet dander, joint pain with quinolones, diarrhea with amoxicillin, and aspirin-associated angioedema. She is blood type O Rh-negative with a negative antibody screen on admission.... OPTIONS A. Administer 4 vials of 300 mug Rho(D) immune globulin intramuscularly on the postpartum ward now, based on 1.8% x 50 = 90 mL fetal whole blood - 90/30 = 3 vials, then add one safety vial per policy. B. Administer 3 vials of 300 mug intramuscularly now using 90/30 = 3 and omit the additional safety vial to avoid overexposure. C. Administer 7 vials of 300 mug intramuscularly now using an RBC-volume method (maternal blood volume x % fetal cells / 15 mL per vial), which yields about 7 vials in this patient. D. Administer a single 300 mug vial intramuscularly now because percentages under 2% fetal cells are adequately covered by the routine postpartum dose without calculation. CORRECT ANSWER A. Administer 4 vials of 300 mug Rho(D) immune globulin intramuscularly on the postpartum ward now, based on 1.8% x 50 = 90 mL fetal whole blood - 90/30 = 3 vials, then add one safety vial per policy. EXPLANATION After delivery of an Rh-positive infant to an unsensitized Rh-negative mother, postpartum Rho(D) immune globulin dosing is guided by the quantified fetomaternal hemorrhage. The institution s Kleihauer-Betke policy defines fetal whole-blood volume as % fetal cells x 50 and assigns vials as fetal whole blood / 30, with decimals less than 0.5 rounded down and =0.5 rounded up, then adds one safety vial. Here, 1.8% x 50 = 90 mL fetal whole blood. Dividing 90 by 30 gives 3 vials; adding one safety vial yields 4 vials of 300 mug intramuscularly within 72 hours postpartum. Teaching point: always follow the local, pre-specified algorithm and include the safety vial to avoid under-dosing when KB estimates straddle vial cut points. Alternative methods exist, such as using maternal blood volume and fetal RBC volume with 300 mug covering 15 mL fetal RBCs; that approach would produce about 7 vials in this patient. However, the question specifies the institution s whole-blood method, so 4 vials is correct for this policy. Single-vial empiric dosing is insufficient when a quantified fetomaternal hemorrhage exceeds 30 mL fetal whole blood, and omitting the safety vial invites alloimmunization if the KB percentage underestimates the true fetal load. Teaching point: document the calculation steps, rounding rule, and timing; administer promptly within 72 hours to minimize medicolegal risk and protect future pregnancies. Further reading: Links to sources are provided for optional further reading only. The questions and explanations are independently authored and do not reproduce or adapt any specific third-party text or content. --------------------------------------------------- Our cases and questions come from the https://EndlessMedical.Academy quiz engine - multi-model platform. Each question and explanation is forged by consensus between multiple top AI models (i.e. Open AI GPT, Claude, Grok, etc.), with automated web searches for the latest research and verified references. Calculations (e.g. eGFR, dosages) are checked via code execution to eliminate errors, and all references are reviewed by several AIs to minimize hallucinations. Important note: This material is entirely AI-generated and has not been verified by human experts; despite stringent consensus checks, perfect accuracy cannot be guaranteed. Exercise caution - always corroborate the content with trusted references or qualified professionals, and never apply information from this content to patient care or clinical decisions without independent verification. Clinicians already rely on AI and online tools - myself included - so treat this content as an additional focused aid, not a replacement for proper medical education. Visit https://endlessmedical.academy for more AI-supported resources and