Barakat M M, Nawab Z M, Yu A W, Lau A H, Ing T S, Daugirdas J T
Loyola University Stritch School of Medicine, Maywood, IL.
J Am Soc Nephrol. 1993 May;3(11):1813-8. doi: 10.1681/ASN.V3111813.
Although the hypotensive effects of food ingestion during hemodialysis have been documented, the hemodynamic mechanism is unclear. It could be decreased cardiac output due to splanchnic sequestration or decreased vascular resistance due to splanchnic vasorelaxation. Also, the effects of caffeine, which block postprandial hypotension in the elderly, have not been studied in a dialysis setting. Central hemodynamics were monitored by thoracic electric bioimpedance in 10 dialysis patients who ingested a test meal 1 h into dialysis. All ultrafiltration was done during the initial 2 h. Bicarbonate dialysate was used. Each patient was studied three times in a double-blind (with respect to placebo/caffeine) cross-over trial: placebo/no meal, placebo/meal, and caffeine/meal. Blood pressure decreased sooner and to a great extent in the treatments in which food ingestion accompanied ultrafiltration (e.g., at 30 min after food ingestion, percent change in mean arterial pressure was -12.4 +/- 1.8 versus -2.4 +/- 3.5 mm Hg when food was not ingested; P < 0.05). The hemodynamic mechanism of food-associated hypotension was found to be a fall in systemic vascular resistance (SVRI). Caffeine pretreatment (200 mg), which resulted in intradialytic plasma caffeine levels of about 4 micrograms/mL at time of food ingestion, had no effect on food-associated reductions in blood pressure or SVRI. The results suggest that food ingestion during dialysis causes hypotension primarily because of decreased SVRI. The effects of food ingestion on mean arterial pressure and SVRI are not attenuated by the ingestion of 200 mg of caffeine 1 h before dialysis.
尽管血液透析期间进食导致血压降低的现象已有文献记载，但其血流动力学机制尚不清楚。可能是由于内脏血管淤滞导致心输出量减少，或者是由于内脏血管舒张导致血管阻力降低。此外，咖啡因可阻止老年人餐后低血压，但其在透析环境中的作用尚未得到研究。对10名透析患者在透析1小时后进食试验餐，通过胸电阻抗监测其中心血流动力学。所有超滤均在最初2小时内完成。使用碳酸氢盐透析液。在双盲（关于安慰剂/咖啡因）交叉试验中，每位患者接受三次研究：安慰剂/不进餐、安慰剂/进餐、咖啡因/进餐。在进食伴随超滤的治疗中，血压下降更快且幅度更大（例如，进食后30分钟，平均动脉压的变化百分比为-12.4±1.8，而未进食时为-2.4±3.5mmHg；P<0.05）。发现与食物相关的低血压的血流动力学机制是全身血管阻力（SVRI）下降。咖啡因预处理（200mg）在进食时使透析期间血浆咖啡因水平达到约4μg/mL，对与食物相关的血压降低或SVRI没有影响。结果表明，透析期间进食导致低血压主要是因为SVRI降低。透析前1小时摄入200mg咖啡因不会减弱进食对平均动脉压和SVRI的影响。
