Background: Blood transfusion is a life-saving intervention but is associated with adverse reactions in a subset of recipients. An acute transfusion reaction (ATR) is defined as any unfavorable response occurring within 24 h of blood component administration. This retrospective observational study aimed to determine the frequency and characteristics of ATRs at King Saud Medical City (KSMC), Riyadh, Saudi Arabia. Methods: We conducted a retrospective study using data from the Transfusion Medicine Laboratory (TML) at KSMC between January 2019 and December 2023. Demographic, clinical, and laboratory data from 238 confirmed ATR records were analyzed using SPSS v21.0. Chi-square, Mann–Whitney U, and risk ratio analyses were performed; p < 0.05 was considered statistically significant. Results: Among 238 patients (59.2% female; mean age 33.7 ± 18.5 years), allergic reactions were the most frequent ATR (70.2%, n = 167), followed by febrile non-hemolytic transfusion reactions (FNHTRs); (24.4%, n = 58). Packed red blood cell (PRBC) transfusion was the most commonly implicated product (82.4%; n = 196; p < 0.001). Fever, rash, itching, and chills were significantly associated with specific reaction subtypes (p < 0.001). The pattern of post-transfusion workup differed significantly across reaction types (p < 0.001). Age, gender, ward distribution, and reaction timing were not significant predictors of ATR occurrence. Conclusions: Allergic reactions are the predominant ATR form at KSMC. Demographic variables are not reliable predictors of ATR. Strengthening hemovigilance systems and clinician education is recommended to improve transfusion safety.

Background: Blood donation deferral poses a significant challenge to transfusion services worldwide, threatening blood supply adequacy and donor retention. Population-specific data on deferral epidemiology and subsequent donor return behavior in Saudi Arabia remain limited. This study aimed to characterize the prevalence, reasons, and demographic patterns of blood donation deferral at King Fahad Medical City (KFMC)—a major quaternary referral center in Riyadh—and to quantify the rate at which temporarily deferred donors re-engage with the donation process at the encounter level. Methods: A retrospective observational study was conducted on records of all registered volunteer blood donor encounters at KFMC from 1 January 2023 to 31 December 2024 (n = 60,290), extracted from the Hematos IIG blood bank information system. Donor demographics (age, sex, weight, nationality), deferral classification (temporary, permanent, indeterminate), deferral reason, pre-deferral donation frequency, and post-temporary-deferral donation frequency were analyzed. Inferential statistics employed the Chi-square test and Fisher’s exact test (significance threshold: p < 0.05). A multinomial logistic regression, restricted to the 10,681 encounters classified as temporarily deferred, identified correlates of post-deferral donation frequency, adjusted for donation frequency before deferral. Results: Of 60,290 registered donor encounters, 18,458 (30.6%) resulted in deferral. Male donors constituted 86.4% of deferrals; the 31–45-year age group accounted for 47.3%. The three leading deferral reasons were abnormal vital signs (39.4%), post-donation transfusion-transmitted infectious disease (TTID) screening reactivity (35.6%), and low hemoglobin (14.0%). Sex-stratified analysis revealed that among female donors, low hemoglobin (40.50%) exceeded abnormal vital signs (35.50%) as the leading reason. Among the 10,681 encounters classified as temporarily deferred, 86.70% did not return to donate within the observation window. In a multinomial regression restricted to this subgroup, donation frequency before deferral was the strongest correlate of return (OR 21.02, 95% CI 14.94–29.58 for three or more subsequent donations among donors with ≥3 prior donations vs. none), and deferral for abnormal vital signs was also associated with higher odds of return (OR range 3.55–4.60, all p < 0.001). Conclusions: Nearly one-third of blood donor encounters at this tertiary center resulted in deferral, with abnormal vital signs and TTID screening reactivity as the predominant reasons. The low re-engagement rate (13.30%) among temporarily deferred donors underscores a need for structured follow-up programs, particularly for first-time donors, for whom an established donation history was the strongest predictor of return. Sex-specific interventions—targeting hemoglobin optimization in female donors and cardiovascular risk factor awareness in male donors—are warranted to reduce the deferral burden and safeguard the blood supply.

Endovascular thrombectomy [EVT] has revolutionized acute ischemic stroke care by restoring macrovascular reperfusion in large vessel occlusion; however, a persistent “reperfusion–outcome gap” remains, leaving nearly half of successfully recanalized patients without functional independence. This review aims to bridge this translational gap by establishing a mechanistic and procedural framework for adjunctive pharmacotherapy designed to target the microvascular, thromboinflammatory, and reperfusion-related injuries left unaddressed by purely mechanical models. Synthesis of recent literature reveals that futile recanalization is driven by three distinct anatomical and biological bottlenecks: distal microembolization, microcirculatory no-reflow, and ischemia–reperfusion injury. Furthermore, the inconsistency of clinical trial results reflects a critical precision deficit, including dilution of treatment effects across heterogeneous reperfusion grades, inadequate stroke etiology stratification, delayed pharmacologic intervention relative to evolving microvascular injury, and reliance on functional endpoints that inadequately capture tissue-level reperfusion. To address these limitations, this review outlines a tri-axial clinical decision framework integrating reperfusion status, stroke etiology and hemorrhagic risk, which maps specific patient phenotypes, such as incomplete macrovascular reperfusion or underlying intracranial atherosclerotic disease, to targeted pharmacologic strategies including microcatheter-directed intra-arterial thrombolytics and glycoprotein IIb/IIIa inhibitors. The review further argues that future progress will require imaging-guided identification of residual hypoperfusion, mechanistically enriched patient enrolment, and incorporation of biological and tissue-level reperfusion endpoints alongside conventional functional outcomes. Ultimately, closing the reperfusion–outcome gap will require moving beyond empirical, universal drug administration toward a precision, pharmacologically augmented EVT paradigm that aligns adjunctive therapy with mechanism-specific procedural phenotypes and prioritizes true tissue-level recovery over angiographic success alone.

Background/Objectives: Blood group antigen frequencies vary across ethnic populations and are critical for safe transfusion practice, inventory management, and alloimmunization prevention. This study aimed to determine ABO blood group, extended Rh phenotype (D, C, c, E, e), and K antigen frequencies among blood donors at the Riyadh Regional Blood Bank, and to examine their associations with donor ethnicity. Methods: This retrospective cross-sectional study analyzed 10,463 blood donors (January–December 2021) using the Immucor NEO Iris fully automated immunohematology analyzer. Donors were classified into five ethnic groups. Chi-square tests assessed associations (p < 0.05), the primary scientific contribution is the descriptive frequency data, with hypothesis testing presented as secondary and exploratory. Results: Most donors were male (95.2%). Blood group O+ was most prevalent (31.6%); AB− was rarest (0.9%). Rh D-positivity was 84.7%, lowest among Saudis (81.1%). The most frequent Rh phenotypes were CcDee (24.2%), ccDee (19.9%), and CCDee (17.7%). K antigen positivity was 13.7%. Significant associations were found between D antigen and ethnicity (p < 0.001), Rh phenotype and ethnicity (p = 0.003), and ABO and ethnicity (p < 0.001). A hypothesis-generating association between Rh phenotype and K antigen (p = 0.019) did not meet the Bonferroni-corrected threshold and is considered exploratory. Conclusions: This study provides, to our knowledge, one of the largest ethnically stratified blood group datasets from Riyadh to date. The high D-negativity among Saudi donors (18.9%) has direct implications for extended phenotyping protocols and rare donor registry development. The association between Rh phenotype and K antigen requires molecular confirmation before any biological or clinical conclusions can be drawn.