Nếu trong một nghi ngờ hoạt động xảy ra liên quan đến lưu thông của các chi, xung oxy ở cực tương ứng có thể cung cấp các chỉ dẫn ban đầu của các vấn đề tuần hoàn. Tùy thuộc vào áp suất vòng bít và chiều dài của thời gian sử dụng, miếng ga-rô có thể che giấu nguy cơ chấn thương do thiếu máu cục bộ mô (tổn thương thần kinh, nhược cơ, tiêu cơ vân | 119 10 Positioning injuries as seen by the anaesthetist the rarity of thoracic outlet syndrome for example 68 . If during an operation doubts occur with regard to circulation of the extremities pulse oximetry at the corresponding extremity can provide initial indications of circulatory problems. Depending on cuff pressure and length of time used tourniquets can conceal the risk of ischaemic injuries to the tissue nerve lesions myasthenia rhabdomyolysis compartment syndrome . Arterial vascular occlusions occur the frequency of deep vein thrombosis is not increased 6 28 . Cuff pressure of 100-150 mmHg above the systolic blood pressure is considered adequate and the tourniquet time should not exceed 2 h 76 . Shunt arms are wrapped up well in cotton wool loosely fixed and protected with arm positioning rails against exerted pressures. Eyes Lacking eyelid closure at the same time as a decrease in lacrimation while under anaesthetic can cause erosion of the cornea. Lacking eyelid closure increases the risk of direct injuries to the cornea . from face masks fingernails catheters or adhesive drapes. High persistent pressure on the orbita and bulbus can cause a fatal reduction in vision through to irreversible loss of sight. Irreversible loss of sight has been observed after being exposed to pressure for just 10 min in the prone position 22 . This is caused by ischaemia of the optic nerve and retina as a result of compression. Hypotension and anaemia can cause the ischaemic injuries and loss of sight 14 . The blood flow through the optic nerve and choroid is essentially passive from the arterial blood pressure with only very slight autoregulation mechanisms 67 . According to Wolfe 78 unexpected bradyarrhythmia can be a warning sign of increased intraocular pressure. Although impaired vision has been described for various positionings specific significance is attributed to the prone position with the use of headrests. In rare cases the use of face masks with a hard .
