<![CDATA[Background: Position-dependent hypoxemia during spinal anesthesia positioning is uncommon but may pose safety concerns in older patients with unilateral lung disease.Case: An 84-year-old woman with a proximal femoral fracture and clinical radiographic features consistent with left-sided pneumonia was scheduled for bipolar hip hemiarthroplasty. Fracture-related pain and positioning limitations precluded the sitting position and right lateral decubitus, making the left lateral decubitus (LLD) position the only feasible option for spinal anesthesia. During LLD positioning, oxygen saturation dropped to 84-88% without dyspnea and promptly improved after returning to the supine position. Ancillary evaluation showed preserved biventricular systolic function (left ventricular ejection fraction 60%, TAPSE 19 mm), and no sonographic evidence of pulmonary edema. Spinal anesthesia was performed in the LLD position using 7.5 mg of 0.5% hyperbaric bupivacaine with 50 mcg intrathecal morphine. The surgery proceeded with a supine-position modification and remained hemodynamically and respiratory stable without intraoperative complications.Discussion: In unilateral pneumonia, placing the diseased lung in the dependent position can exacerbate ventilation perfusion mismatch and functional shunt, leading to reversible positional hypoxemia. Older adults may exhibit silent hypoxemia without overt dyspnea, so continuous monitoring during positioning for neuraxial anesthesia is crucial. In this case, the reproducible pattern of desaturation confined to the LLD position, with rapid improvement in supine and absence of cardiac decompensation or pulmonary edema, strongly supported a positional ventilation perfusion mechanism rather than primary cardiac failure or global ventilatory impairment.Conclusion: This case highlights the “bad lung down” phenomenon as a cause of silent, position-dependent hypoxemia during spinal positioning in an octogenarian with left-sided pneumonia. Early recognition of positional desaturation and simple modification of the operative position can help maintain intraoperative safety without abandoning regional anesthesia.]]>
