[Meralgia paraesthetica as complication of patient positioning : A not fully controllable risk]. / Meralgia paraesthetica als Lagerungsschaden : Kein voll beherrschbares Risiko.

Meralgia paraesthetica (MP) is the consequence of an entrapment or stretch injury of the lateral femoral cutaneous nerve at the crossing region with the inguinal ligament where the nerve exits the pelvis. It results in temporary or permanent sensory loss, paraesthesia and pain in the anterolateral region of the thigh. Idiopathic forms are known for example as seat belt syndrome or jeans syndrome. An MP can also occur as a complication of surgical or intensive care patient positioning. In focus are the lithotomy position, prone position and beach chair position.We analyzed 21 complaints about MP occurring for the first time postoperatively, which had been submitted to the expert committee for medical treatment errors at the North Rhine Medical Association over the past 10 years. Among these, six cases could be identified as positioning damage after a lithotomy position. In three cases MP occurred after supine positioning but the etiology could not be clarified with certainty. In 12 cases MP was recognized as a direct surgical complication.The pathophysiology, incidence and course as well as legal implications of position-related MP are discussed. Pressure damage to the nerve at its intersection with the inguinal ligament is assumed to be the main pathomechanism. Although all the cases presented here occurred after lithotomy positioning, the complication also appears to occur with other types of positioning according to the literature data, the most common being prone positioning. This also explains the increasingly published case reports of MP after prone positioning in COVID-19 patients for respiratory treatment. Safe avoidance of the positioning-related complication does not appear to be possible due to the anatomical variability of the course of the nerve and the unclear pathomechanisms.

[Thalamic infarction following paradoxical embolism during total hip replacement : Case report and pathophysiological considerations]. / Thalamusinfarkt nach paradoxer Embolie bei Hüftgelenkersatz in unauffälliger Allgemeinanästhesie und Seitlagerung : Falldarstellung und pathophysiologische Überlegungen.

Because of a painful right-sided coxarthrosis a 57-year-old female patient underwent a cementless total arthroplasty under general anesthesia. Except for Asperger's syndrome and an occlusion of a vein in her left eye she stated no other diseases or complaints, especially no cardiac problems. Postoperatively she developed neurological symptoms of left-sided hemiparesis and hemihypesthesia. A cranial computer tomography was performed and a right-sided infarction of the thalamic region was found. A patent foramen ovale (PFO) and atrial septal aneurysm were detected 5 days later. The incidence of a PFO is given as 25% of the population. A paradoxical air embolism in the presence of a PFO is a feared complication in neurosurgical interventions in a semi-sitting or sitting position. Corpuscular emboli, such as bone, cement, fat or wound debris may be the reason for paradoxical embolisms in combination especially with partial or total hip replacement. The kind of embolism in the case described could not be clarified. Deep vein thrombosis or cardiac arrhythmia could be excluded. Therefore, it can be considered most likely that the operation site was the source of the embolism. The trigger for a paradoxical embolism is a reversal of the pressure difference between the right and left atria: normally the left atrial pressure exceeds the right atrial pressure by ca. 2-4 mm Hg, resulting possibly in a small clinically irrelevant left-to-right shunt. If the pulmonary arterial circulation is compromised and pulmonary vascular resistance increases, the pressure gradient between the left and right atria reverses and a right-to-left shunt can occur causing a paradoxical embolism. Positive end-expiratory pressure (PEEP) ventilation during anesthesia could be an important reason for a shunt reversal between the right and left atria and therefore favoring a paradoxical embolism but the pathophysiological role of PEEP has not yet been finally clarified.