At the present time, plastic syringes are most commonly used for collecting arterial blood. The oxygen tension of the arterial blood (Pa,O2) in these syringes may fall. We studied the effect of the type of syringe, metabolism, and storage time on the arterial oxygen pressures measured and on the pulmonary shunt calculated. In 10 patients, 2-3 h after aortacoronary bypass surgery, a 100% oxygen test was performed. Four arterial blood gas samples were withdrawn from each patient in random order, two in glass syringes and two in plastic syringes. One glass and one plastic syringe were stored at room temperature (RT), and the others were stored in ice-water (IW). Each sample was analysed as soon as possible, and repeated 15, 30, 60 and 120 min after sampling. The Pa,O2 measurement in blood in the glass syringe in IW measured as soon as possible after sampling was considered the "gold standard". Pulmonary shunt calculations were performed using the results of the various blood gas analyses. Compared with the "gold standard", all of the other methods showed significant deterioration in the Pa,O2 measurement. The effect due to diffusion was 0.05 kPa x min(-1), and that due to metabolism 0.11 kPa x min(-1). The Pa,O2 in the glass syringes stored in IW remained stable with time. The pulmonary shunt was significantly overestimated when the "gold standard" blood gas results were not used (range 0.8-9.9%). Glass (not plastic) syringes should be used in the 100% oxygen test. The syringe should be cooled immediately, even when the sample is analysed as soon as possible.
Recent experiences from several centers indicate that the overall risk of spinal cord ischemia during thoracoabdominal aortic aneurysm repair has decreased to 5–8%. The results from these centers are rather consistent, despite the use of a variety of spinal protection strategies. An alternative to the various distal aortic perfusion techniques is selective spinal cooling by cold saline lavage. The principle advantage of selective hypothermia is the avoidance systemic heparinization and extracorporeal bypasses, while affording comparable spinal protection. The primary method of spinal cooling was pioneered by Cambria et al. at Massachusetts General Hospital. In their experience, paraplegia or paresis occurred in 6.9% of patients (5-year period, 170 cases). An alternative to the Cambria method utilizes readily available perfusion supplies and offers the potential advantages of lower cerebral spinal fluid-systemic blood pressure differences, more expedient cooling, and deeper spinal hypothermia. This report describes this method and the clinical course of a patient treated with it.
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