Noi O, Makimoto K
Department of Otolaryngology, Osaka Medical College, Takatsuki, Japan.
Hear Res. 1998 Sep;123(1-2):55-60. doi: 10.1016/s0378-5955(98)00099-9.
Glycerol, an osmotic diuretic, has been used for the diagnosis and treatment of endolymphatic hydrops. Hearing improvements in hydropic ears are attributed to its dehydrating effect. In addition to this effect, glycerol also increases cochlear blood flow. Urografin, another hyperosmotic agent used for vasography, is similarly known to increase local blood flow. The present study compared these two hyperosmotic agents, glycerol and Urografin, in their effects on cochlear blood flow and serum osmolarity. Laser Doppler flowmetry on the lateral wall of the cochlea revealed that the increase in cochlear blood flow with a 30-min infusion (0.025 ml/min) of 76% Urografin continued for a longer time than with a 30-min infusion (0.025 ml/min) of 50% (v/v) glycerol. The significant increases appeared at 20 and 30 min after the infusion with the former; 10, 20, 30, 40, 50 and 60 min after the infusion with the latter. Intravenous infusion of these agents also caused elevation in serum osmolarity. This elevation was appreciably greater with Urografin infusion (maximal increase: about 30 mOsm on average) than with glycerol infusion (maximal increase: about 6 mOsm on average), and the former elevation appeared to be longer lasting than the latter. These differences were ascribed to differences between glycerol and Urografin with respect to the creation of an osmotic gradient across the capillary walls of cochlear blood vessels. Since glycerol penetrates the interstitial space and moves into inner ear fluids, the gradient may decline faster. It would be assumed that a higher concentration of the hyperosmotic agent in the capillary blood causes more vasodilatation and lowering of blood viscosity. Alternatively, direct action of these agents on the vascular wall may affect some biological processes, leading to vasodilatation in different degrees and durations with different agents. Hearing improvement with glycerol administration in hydropic ears was also discussed from the perspective of cochlear blood flow.
甘油是一种渗透性利尿剂，已被用于内淋巴积水的诊断和治疗。积水耳听力的改善归因于其脱水作用。除了这种作用外，甘油还能增加耳蜗血流量。泛影葡胺是另一种用于血管造影的高渗剂，同样已知能增加局部血流量。本研究比较了这两种高渗剂甘油和泛影葡胺对耳蜗血流量和血清渗透压的影响。耳蜗外侧壁的激光多普勒血流仪显示，以0.025 ml/min的速度输注30分钟76%的泛影葡胺后，耳蜗血流量的增加持续时间比以0.025 ml/min的速度输注30分钟50%（v/v）甘油后更长。前者在输注后20和30分钟出现显著增加；后者在输注后10、20、30、40、50和60分钟出现显著增加。静脉输注这些药物也会导致血清渗透压升高。泛影葡胺输注引起的这种升高（平均最大增加约30 mOsm）明显大于甘油输注（平均最大增加约6 mOsm），且前者的升高似乎持续时间更长。这些差异归因于甘油和泛影葡胺在耳蜗血管毛细血管壁上形成渗透梯度方面的差异。由于甘油可穿透间质间隙并进入内耳液，梯度可能下降得更快。可以假定毛细血管血中高渗剂的浓度越高，血管舒张和血液粘度降低的程度就越大。或者，这些药物对血管壁的直接作用可能会影响某些生物学过程，导致不同药物在不同程度和持续时间上引起血管舒张。还从耳蜗血流量的角度讨论了在积水耳中使用甘油改善听力的情况。
