Abode-Iyamah, Kingsley

Background: Pulse pressure variation (PPV) is widely used to guide fluid responsiveness in mechanically ventilated patients, but its accuracy in the prone position remains uncertain. Prone positioning alters respiratory mechanics and venous return, potentially diminishing the respiratory variation in stroke volume that PPV is designed to detect. We conducted a systematic review and meta-analysis to evaluate the diagnostic accuracy of PPV for predicting fluid responsiveness during prone spine surgery. Methods: We searched MEDLINE, Embase, Scopus, and Cochrane through July 2025 for prospective studies evaluating PPV in adults undergoing prone spine surgery. Two reviewers independently screened studies, extracted data, assessed risk of bias using QUADAS-2, and pooled diagnostic performance using a bivariate random-effects model. The protocol was registered with PROSPERO (CRD420251106134). Results: Of 599 records, 34 underwent full-text review, and 10 studies (433 patients) were included. PPV thresholds ranged from 7% to 15%. Most studies were at low risk of bias except for the index test because thresholds were determined post hoc. For predicting fluid responsiveness, PPV had a pooled sensitivity of 68% (95% CI: 61%-75%) and specificity of 76% (95% CI: 65%-84%), with a summary area under the receiver operating characteristic curve of 0.72 (95% CI: 0.64-0.80). Conclusions: PPV showed only moderate diagnostic performance for predicting fluid responsiveness during prone spine surgery. Its performance may have been influenced by threshold variability, heterogeneous reference standards, fluid-challenge protocols, ventilation strategies, and positioning systems. PPV should therefore be interpreted alongside complementary dynamic assessments rather than in isolation, particularly during lung-protective ventilation.

Background Effective hemostasis in spinal surgery is critical, especially near sensitive structures such as the spinal cord and dorsal root ganglia. Flowable hemostatic agents offer targeted control in irregular, hard-to-reach areas. This study evaluates the safety and efficacy of flowable collagen hemostat (FC) in an ovine lumbar laminectomy model with open durotomy by making a direct comparison with the gelatin hemostatic matrix with thrombin (GM) and a no-treatment control (Sham). Methods Fifty-four Polypay sheep (27 F, 27 M) underwent lumbar laminectomy and open durotomy and then received FC, GM, or no treatment ( n = 18/group). Hemostasis was assessed at 3 min postapplication without tamponade. Neurological examinations were performed at periodic intervals, and tissues were collected on days 7, 45, and 120 for a histological analysis. Results Hemostasis was achieved in 100% of FC-treated sites, 94.4% of GM, and 72.2% of Sham. Sham-treated animals exhibited more severe and prolonged neurological deficits compared with those treated with FC or GM. Inflammation decreased significantly across all groups, from mild/moderate on day 7 to minimal on day 45, and was barely detectable by day 120. FC was associated with favorable histological responses in both intradural and extradural spinal tissues, comparable to GM and Sham. Conclusion Flowable collagen hemostat was safe and effective when applied directly to the spinal cord and surrounding neurological tissues during laminectomy with open durotomy. Its performance was comparable to that of the gelatin hemostatic matrix with thrombin in terms of hemostatic efficacy and histological outcomes, with both agents demonstrating superior neurological recovery compared with the untreated Sham group.