The effect of tranexamic acid on cochlear blood flow in guinea pigs measured by laser Doppler flowmetry

The effect of tranexamic acid on cochlear blood flow in guinea pigs measured by laser Doppler flowmetry

Auris Nasus Larynx 28 (2001) 215– 218 www.elsevier.com/locate/anl The effect of tranexamic acid on cochlear blood flow in guinea pigs measured by las...

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Auris Nasus Larynx 28 (2001) 215– 218 www.elsevier.com/locate/anl

The effect of tranexamic acid on cochlear blood flow in guinea pigs measured by laser Doppler flowmetry Yen Hai Tran a, Katsuichiro Ohsaki a,*, Hitoshi Houchi b, Teruhiro Ogawa c, Chun-Sheng Zhu d, Shuji Fushitani b, Kazuo Minakuchi b a

Di6ision of Clinical Otology, Tokushima Uni6ersity Hospital, Tokushima 770 -8503, Japan b Di6ision of Pharmacy, Tokushima Uni6ersity Hospital, Tokushima 770 -8503, Japan c Department of Otolaryngology, Okayama Uni6ersity Medical School, Okayama 700 -8558, Japan d Department of Otolaryngology, Second Uni6ersity Hospital, Fourth Military Medical Uni6ersity, Xi’an 710038, People’s Republic of China Received 10 June 2000; received in revised form 25 December 2000; accepted 19 January 2001

Abstract Objecti6e: This study investigated the vasoactive effect of tranexamic acid on the cochlear blood flow in guinea pigs. Method: 3 ml solution (infusion speed, 0.5 ml/min) containing different concentrations of tranexamic acid was intravenously infused into 15 guinea pigs under general anesthesia. The guinea pigs were grouped according to four levels of dosage of the medicine (470 mg/kg, n=6; 220 mg/kg, n=3; 4 mg/kg, n =3; 1 mg/kg, n= 3). Before administering medicine, saline solution was administered in similar volume and speed as a control. The cochleas were surgically exposed and laser Doppler flowmetry monitored cochlear blood flow volume (CBF). The left femoral artery was cannulated to permit a transducer to monitor systemic blood pressure (BP). Results: (1) Stimulatory effect of tranexamic acid on CBF was dose-dependent at concentrations of 1 – 470 mg/kg and, (2) the time course of changes in CBF was almost identical to that in BP following tranexamic acid administration. Conclusion: Preliminary findings suggest that intravenous administration of tranexamic acid increases CBF due to vasomotorial mechanism effect on BP. © 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Tranexamic acid; Cochlear blood flow; Blood pressure; Laser Doppler flowmetry; Guinea pig

1. Introduction Idiopathic sudden sensory hearing loss (ISSHL) is a disease with no proven pathogenetic mechanism but disturbance of blood flow in the cochlea is one possible etiology. Vasoactive drugs are recommended for the treatment of ISSHL to improve oxygenation of cochlear tissue by increasing cochlear blood flow volume (CBF) [1]. Tranexamic acid, trans-4 aminomethylcyclohexanecarboxylic acid (C8H15NO2), is a potent antifibrinolytic agent with high value for the treatment of bleeding due to systemic and local fibrinolysis [2]. Other pharmacological action consistent with the action of vasoactive * Corresponding author. Present address: Professor emeritus, The University of Tokushima, Okayama Otology Institute 5-25 Nanokaichi Nishi-Machi, Okayama 700-0851, Okayama, Japan. Tel.: +81-86-2226188; fax: +81-86-2226178.

drugs is suggested by a report that tranexamic acid treatment of ISSHL is more significant in traditional treatments, especially if treatment is begun early [3]. Since measurement of CBF is important in elucidating the pathophysiology of ISSHL, laser Doppler flowmeter measurement of CBF during exploratory tympanotomy was attempted [4]. Laser Doppler flowmetry [5] was also used to investigate the effects of intravenous infusion of tranexamic acid on CBF in guinea pigs.

2. Materials and methods All experimental animal procedures were approved and monitored by the Institute of Animal Care and Use Committee of the University of Tokushima, and performed according to institutional guidelines on the care and use of laboratory animals.

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2.1. Animals and surgical approach Fifteen healthy male Hartley guinea pigs (age, 10– 11 weeks) with normal Prayer’s reflex were used. Anesthesia was induced by intraperitoneal pentobarbital sodium (40 mg/kg). After the animal’s head was firmly fixed in a head-holder, a tracheotomy was performed and ventilation was maintained with an artificial respirator (SN-480-7, Shinano, Tokyo). The left femoral artery was cannulated with INTRAMEDIC® polyethylene tubing (i.d. 0.28 mm, o.d. 0.61 mm, Clay Adams, Division of Becton Dickinson, NJ) to monitor systemic blood pressure (BP) using a transducer (AP601G, Nihon Kohden, Tokyo). A catheter was inserted into the right internal jugular vein to allow intravenous administration of medicine. For laser Doppler flowmetry, the left auditory bulla was exposed using a ventral surgical approach which did not cut muscles or large blood vessels. A hole of approximately 5 mm diameter was made on the surface of the bulla to expose the cochlea. To avoid blood contamination of probe tip, the mucosa of the lateral wall of the cochlea was not surgically removed. The 1.7 mm diameter needle probe of a laser Doppler flowmeter (ALF21D, Advance, Tokyo) was placed on the bony wall of the basal turn of the cochlea using a three-dimensional micromanipulator. Units of blood flow volume on the laser Doppler flowmeter were set in ml/min/100 g to establish arbitrary units (AU).

2.2. Experimental protocol To begin the experiment, the general condition of animals (mean9S.E.) was observed, including body weight (6369 15 g), rectal temperature (37.990.1°C [thermistor, class 1.0, Shibaura Electronics, Tokyo]), heart beat (25396 beats/min [blood pressure transducer with recording speed of 1200 mm/min, AP-601G, Nihon Kohden, Tokyo]), hematocrit (46.890.3% [high speed centrifugal micro-hematocrit method, KH-120, Kubota, Tokyo]), glycemia (1179 4 mg/dl [blood glucose test meter, TOECHO SUPER II, KDK, Kyoto]) and serum total protein (4.890.1 g/dl [clinical refractometer, M-E, Erma, Tokyo]); (n =13 – 15). Three millilitres of solution containing various concentrations of tranexamic acid was infused into the right internal jugular vein of 15 guinea pigs for 6 min using an infusion device with infusing speed of 0.5 ml/min (TE-311, Terumo, Tokyo). In this experiment, tranexamic acid concentrations corresponded to CBF values with the aim of calculating the amount of decreased CBF value. Concentrations of tranexamic acid were gradually reduced to focus on significant difference in CBF value. Animals were grouped according to four drug concentrations:

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Group A: Six animals were infused with 470 mg/kg tranexamic acid prepared from commercially available Transamin®S containing 10% tranexamic acid (Daiichi Pharmaceutical, Tokyo). “ Group B: Three animals were infused with 220 mg/ kg tranexamic acid prepared from commercially available Transamin® containing 5% tranexamic acid (Daiichi Pharmaceutical, Tokyo). “ Group C: Three animals were infused with 4 mg/kg tranexamic acid (tranexamic acid powder JP diluted with sterile saline solution adjusted to 0.08%). “ Group D: Three animals were infused with 1 mg/kg tranexamic acid (tranexamic acid powder JP diluted with sterile saline solution adjusted to 0.02%). Before administering medicine, saline solution in similar volume and similar infusing speed was administered as a control and measured values provided the baseline. Animals studied did not show any side effects of tranexamic acid infusion [6], such as nausea, vomiting, and diarrhea, even in the high-dose groups of 470 and 220 mg/kg.

2.3. Data presentation CBF and BP were simultaneously recorded on a chart with a pen-recorder (SS-250F, Sekonic, Tokyo) with recording speed of 600 mm/h. Stable CBF and BP measurement for at least 10 min was recorded at the beginning of each stage of the experiment. An average value for 1 min taken immediately before drug application was considered to be the initial value, providing a baseline of 0%. Percentage values of change relative to this initial baseline were calculated subsequently. Results are presented as mean9 S.E. of values and percentages of the baseline. Statistical significance of percentage of observed CBF changes following drug application was calculated using one-factor ANOVA. A post-hoc test was performed by Fisher’s PLSD. Differences were considered significant at PB0.05.

3. Result All guinea pigs tolerated the surgery well. BP and CBF were unchanged after saline solution was administered as a control. Following medicine administration, the stimulatory effect of tranexamic acid on CBF was dose-dependent at concentrations of 1–470 mg/kg (Fig. 1). Compared with baseline values, mean9 S.E. per cent increase of dose response of tranexamic acid administration on CBF was: Group A, 24.594.0% (470 mg/kg, n=6), Group B, 20.79 1.9% (220 mg/kg, n=3), Group C, 11.190.1% (4 mg/kg, n=3) and Group D, 5.490.5% (1 mg/kg, n= 3). There were significant mean per cent increases; Group A (470 mg/kg) was higher (PB0.001)

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Table 1 Change in CBF and BP after 10% tranexamic acid (470 mg/kg) administrationa CBF, mean9S.E. BP, mean9 S.E. (n =6) (n =6) Pre-administration baseline Post-administration peak value Start of increase Time of peak value Period of increase

Fig. 1. Dose response curve of tranexamic acid intravenous administration on CBF. X-axis indicates logarithm in scale. Concentrationdependent increase at four concentrations (1, 4, 220, and 470 mg/kg) of tranexamic acid. Data points are mean 9 S.E. Baseline, 5.3 90.3 AU. Group A vs. Group D (P B0.001), Group A vs. Group C (P B0.01), Group B vs. Group D (P B 0.01).

than Group D (1 mg/kg) and higher (PB 0.01) than Group C (4 mg/kg); Group B (220 mg/kg) was higher (PB 0.01) than Group D (1 mg/kg). Apparently, significant increase in CBF corresponded to increased concentration of tranexamic acid administered intravenously. Representative records show (Fig. 2) that the time course of changes in CBF was almost the same as that in BP following tranexamic acid administration. Ten percent of tranexamic acid (470 mg/kg), one of two concentrations of medicine clinically used, was selected to investigate in detail the responses of CBF and BP. Table 1 shows: (1) mean systolic BP varied from 46 to 86 mmHg (mean9 S.E., 6195 mmHg) at the baseline and varied from 82 to 100 mmHg (9193 mmHg) after tranexamic acid administration. Tranexamic acid administrations caused simultaneous increase in CBF and systolic BP. (2) CBF began to increase at an average of 0.6 min after 10% tranexamic acid administration, reaching a peak (average value, 6.7 AU or 24% increase) after an average of 5.3 min. CBF then gradually decreased and returned to the baseline within

Fig. 2. Representative records of BP and CBF after intravenous administration of 10% tranexamic acid (470 mg/kg).

5.4 90.3 (0%) 6.7 9 0.4 (24%) 0.6 90.3 5.3 90.6 10.1 9 0.5

AU AU min min min

61 95 mmHg (0%) 91 93 mmHg (49%) 0.6 9 0.1 min 4.7 9 0.9 min 11.2 9 0.2 min

a Intravenous infusion. AU, indicates arbitrary units; BP, systolic blood pressure; 0% indicates average values of the baseline.

an average of 10.1 min (n= 6). (3) BP began to increase at an average of 0.6 min after 10% tranexamic acid administration, reaching a peak (systolic BP average value, 91 mmHg or 49% increase) after an average of 4.7 min. BP then gradually decreased and returned to the baseline within an average of 11.2 min (n=6).

4. Discussion Clinical pharmacology indicates that tranexamic acid is an important drug for the treatment of fibrinolytic bleeding and hemorrhage [2]. Articles consider clinical application of inhibitors of fibrinolysis [6] and hemostatic restoration during cardiopulmonary bypass [7], but such articles do not refer to the increased blood flow or blood pressure characteristic of a vasoactive drug when tranexamic acid is used clinically and experimentally. Recent experiments suggest that tranexamic acid is effective in treatment of hypoxemia [8]. If pathophysiology of ISSHL is reversible [9,10], increased supplies of oxygen and glucose in blood using vasoactive drugs will restore the hypoxemic state of cochlea and these increased supplies may help restore hearing loss. Current studies on inner ear blood flow discuss extrinsic factors of autonomic neural and circulatory hormonal agents and extrinsic factors of myogenic properties, local metabolic activity and maintained normal homeostasis of the inner ear [11]. Recent techniques in laser Doppler flowmetry permit dynamic, precise, and quantitative measurement of blood flow of the inner ear [11]. There is a report that laser Doppler flowmetry measured values at the basal turn of the cochlear wall differ before and after removal of the mucosal layer in the bulla of guinea pigs [12]. However, that report does not describe in detail the value measured before and after removal of mucosa. In human patients undergoing surgery, middle ear mucosal vessels covering the cochlea contribute 50–80% [4] or 40–90% [13] to values

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measured by laser Doppler flowmetry. Mucosal vessels in the bulla covering cochlea in guinea pigs and rats contribute only approximately 10% to laser Doppler flowmetry measurement value [13] and the blood vessels in the cochlear bony wall are few [13]. At the basal turn of the guinea pig cochlea, laser Doppler flowmetry values are similar on the bony wall where mucosal layer was removed and on the surface of the soft tissue of the cochlea that was exposed by drilling a small hole through the bony wall [12]. To produce experimental conditions that allow stable measured value by laser Doppler flowmetry and optimum reproducibility of measured value, the probe tip of a laser Doppler flowmeter was placed on the thin mucosa on the basal turn of cochlea in guinea pig. Blood flow volume was measured, including intra-cochlear circulation and extra-cochlear circulation. Our values measured by laser Doppler flowmetry without removing mucosal layer on the basal turn of cochlea in guinea pigs reflect slight change in blood flow volume of middle ear mucosal vessels in the extracochlear circulation [13]. Animal experiment using guinea pigs [13] suggests that most measured values using laser Doppler flowmetry probably reflect intracochlear circulation, but in human patients [4,13], much of the change in CBF may simply reflect the blood flow volume of middle ear mucosal vessels in the extra-cochlear circulation. Our study shows that, in guinea pigs, CBF increases according to dose-dependent intravenous infusion of tranexamic acid (Fig. 1). Our study also shows that tranexamic acid causes simultaneous increase in CBF and BP (Fig. 2 and Table 1), suggesting CBF change in nearly exact proportion to BP between 20 and 70 mmHg [14]. However, sympathetic nerve regulation occurred markedly when BP is above 160 mmHg [15] and the autoregulatory function for inner ear blood flow is impaired in the hydropic ear of guinea pig [16]. After tranexamic acid administration, the time course of changes in CBF is almost the same as that in BP. Administration of 3 ml saline solution as a control shows no change in BP or CBF, indicating that increased blood circulation volume does not change in BP or CBF. These preliminary findings, suggesting that intravenous administration of tranexamic acid may affect the vasomotorial mechanism, must be confirmed through further studies.

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Acknowledgements Tranexamic acid powder JP used in this experiment was offered courtesy of Daiichi Pharmaceutical, Tokyo.

References [1] Kohut RI, Hinojosa R. Sudden sensory hearing loss. In: Bailey BJ, editor. Head and Neck Surgery — Otolaryngology. Philadelphia, PA: JB Lippincott, 1993:1820 – 5. [2] A, stedt B. Clinical pharmacology of tranexamic acid. Scand J Gastroenterol 1987;22(Suppl. 137):22 – 5. [3] Ohsaki K. Comparison of tranexamic acid (Transamin®) and traditional therapy for sudden deafness. Acta Med Okayama 1980;34:323 – 32. [4] Nakashima T, Suzuki T, Morisaki H, Yanagita N. Measurement of cochlear blood flow in sudden deafness. Laryngoscope 1992;102:1308 – 10. [5] Fujii H, Asakura T, Nohira K, Shintomi Y, Ohura T. Blood flow observed by time-varying laser speckle. Opt Lett 1985;10:104 – 6. [6] Verstraete M. Clinical application of inhibitors of fibrinolysis. Drugs 1985;29:236 – 61. [7] Schumann F. Hemostatic restoration during cardiopulmonary bypass. In: Pifarre´ R, editor. New Anticoagulants for the Cardiovascular Patient. Philadelphia: Hanley & Belfus, 1997:453 – 69. [8] Moriuchi H, Yuizono T. Oleic acid-induced PaO2 decrease model for primary screening of drugs for hypoxemia: effects of tranexamic acid and procaterol hydrochloride on the decrease in PaO2. Folia Pharmacol Jpn 1994;103:27 – 36 (abstr). [9] Ohsaki K, Aoyama H. Pathophysiology of reversible sudden deafness — epidemiological study. Acta Med Okayama 1983;37:131 – 9. [10] Nakashima T, Yanagita N. Outcome of sudden deafness with and without vertigo. Laryngoscope 1993;103:1145 – 9. [11] Miller JM, Ren T-Y, Nuttall AL. Studies of inner ear blood flow in animals and human beings. Otolaryngol Head Neck Surg 1995;102:101 – 13. [12] Filipo R, Barbara M, Cordier A, Mafera B, Romeo R, Attanasio G, Mancini P, Marzetti A. Osmotic drugs in the treatment of cochlear disorders: a clinical and experimental study. Acta Otolaryngol 1997;117:229 – 31. [13] Scheibe F, Haupt H, Berndt H, Magnus S, Weymar P. Laser light transmission and laser Doppler blood flow measurements on the human, rat and guinea pig cochlea. Eur Arch Otorhinolaryngol 1990;247:20 – 3. [14] Brown JN, Nuttall AL. Autoregulation of cochlear blood flow in guinea pigs. Am J Physiol 1994;266:458 –67. [15] Degoute C-S, Preckel M-P, Dubreuil C, Banssillon V, Duclaux R. Sympathetic nerve regulation of cochlear blood flow during increases in blood pressure in humans. Eur J Appl Physiol 1997;75:326 – 32. [16] Yamamoto K, Kubo T, Matsunaga T. Autoregulation of inner ear blood flow in normal and hydropic guinea pigs. Acta Otolaryngol 1991;111:312 – 8.