Topical application of amrinone (a selective phosphodiesterase III inhibitor) for relief of vasospasm

Vasodilating Effects of Antispasmodic Agents and Their Cytotoxicity in Vascular Smooth Muscle Cells and Endothelial Cells-Potential Application in Microsurgery

This study aimed to elucidate the vasodilatory effects and cytotoxicity of various vasodilators used as antispasmodic agents during microsurgical anastomosis. Rat smooth muscle cells (RSMCs) and human coronary artery endothelial cells (HCAECs) were used to investigate the physiological concentrations and cytotoxicity of various vasodilators (lidocaine, papaverine, nitroglycerin, phentolamine, and orciprenaline). Using a wire myograph system, we determined the vasodilatory effects of each drug in rat abdominal aortic sections at the concentration resulting in maximal vasodilation as well as at the surrounding concentrations 10 min after administration. Maximal vasodilation effect 10 min after administration was achieved at the following concentrations: lidocaine, 35 mM; papaverine, 0.18 mM; nitroglycerin, 0.022 mM; phentolamine, 0.11 mM; olprinone, 0.004 mM. The IC₅₀ for lidocaine, papaverine, and nitroglycerin was measured in rat abdominal aortic sections, as well as in RSMCs after 30 min and in HCAECs after 10 min. Phentolamine and olprinone showed no cytotoxicity towards RSMCs or HCAECs. The concentrations of the various drugs required to achieve vasodilation were lower than the reported clinical concentrations. Lidocaine, papaverine, and nitroglycerin showed cytotoxicity, even at lower concentrations than those reported clinically. Phentolamine and olprinone show antispasmodic effects without cytotoxicity, making them useful candidates for local administration as antispasmodics.

Mechanically Induced Vasospasm-Evaluation of Spasmolytic Efficacy of 10 Pharmaceutical Agents Using Laser Speckle Contrast Imaging

BACKGROUND AND OBJECTIVES

Vasospasm is a thorny problem often encountered in microvascular surgery that seriously threatens the survival of vascularized tissue transfers. This investigation is dedicated to establishing a model of vasospasm and to evaluating the antispasmodic efficacy of 10 pharmacologic agents.

STUDY DESIGN/MATERIALS AND METHODS

Eighty Sprague-Dawley rats were used. After anesthesia and depilation, the femoral neurovascular bundle was exposed, and a pair of microsurgical forceps were used to trigger vasospasm of the femoral vessels by blunt dissection. Then, 10 pharmacological agents, namely, prostaglandin E1, sodium nitroprusside, magnesium sulfate, papaverine, normal saline, phentolamine, verapamil, 2% lidocaine hydrochloride, amrinone, and 12% lidocaine hydrochloride, were dripped to the femoral vessels, after which laser speckle contrast imaging was used to collect perfusion images, acquiring the perfusion and the inner caliber of the femoral vessels at multiple timepoints. Furthermore, blood perfusion and the time consumed to escape vasospasm and reach hyperperfusion in each group were calculated. The difference of spasmolytic efficacy among the agents was statistically analyzed by one-way analysis of variance.

RESULTS

There was a significant difference in antispasmodic ability among the 10 agents (P < 0.001). 10% magnesium sulfate and 12% lidocaine were distinguished among the 10 agents in resolving the vasospasm. 10% magnesium sulfate demonstrated the best antispasmodic potency, which enabled the shortest time consumed for vessels to escape spasm and reach hyperperfusion. 12% lidocaine ranked second in efficacy, demonstrating a similar effect except that it could not propel the femoral vein to a state of hyperperfusion. For the remaining agents, the time consumed for the artery to escape spasm was all significantly shortened when compared with normal saline (P < 0.001). For the venous spasm, all agents except prostaglandin E1 could significantly shorten the time consumed for the vein to escape spasm (P < 0.001).

CONCLUSIONS

In terms of resolving mechanically induced vasospasm, 10% magnesium sulfate is the best antispasmodic, followed by 12% lidocaine. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Management of vasopressor induced ischemia

Purpose

We evaluated a cohort of patients who developed vasopressor-induced limb ischemia and the management options to prevent progression or minimize morbidity of digital necrosis.

Methods

We reviewed all current literature on pressor-induced limb ischemia and report options for the management of patients requiring vasopressors who developed limb ischemia. We then retrospectively reviewed presentation, treatment, and short-term outcomes for patients at our tertiary referral academic medical center that developed this complication. Finally, we recommend guidelines for the tiered management of these complex patients.

Results

Thirty-six patients were included. Twenty-six patients (72%) required resuscitation with more than one vasopressor. Vasopressors were initiated for septic-shock (52.7%), cardiogenic-shock (16.7%), hypovolemic-shock (13.9%), acute transplant rejection (13.9%), and neurogenic-shock (2.8%). According to the tiered management recommendations, patients were managed with phase 1 care (19%), phase 2 care (8.3%), phase 3 care (50%) or phase 4 care (5.6%). The patient expired in the acute setting in 13.9% of cases.

Conclusion

Life-saving vasopressors risk digital ischemia and necrosis. Early recognition, reporting, and treatment of this complication are important in minimizing morbidity. Using a tiered approach helps organize the healthcare team's management of this iatrogenic complication while respecting the treatment paradigm of "life over limb," and may be safely performed with acceptable outcomes.

Comparative study of different combinations of microvascular anastomosis types in a rat vasospasm model: versatility of end-to-side venous anastomosis in free tissue transfer for extremity reconstruction

BACKGROUND

There have been many studies comparing the patency rates of end-to-end and end-to-side microvascular anastomoses in both arteries and veins. Most of them failed to demonstrate a significant difference. The purpose of this study was to compare three different combinations of microvascular anastomoses in a rat vasospasm model, and determine which type of anastomosis is the most tolerant to vasospasm.

METHODS

Ninety Wistar rats were divided into three groups (n = 30 for each). In each group, a free pectoral skin flap was elevated and microsurgically transferred to the anterior cervical region. In group 1, end-to-end anastomoses were performed on both arteries and veins, in group 2 end-to-side anastomoses were performed on arteries and end-to-end anastomoses were performed on veins, and in group 3 end-to-end anastomoses were performed on arteries and end-to-side anastomoses were performed on veins. After revascularization, vasospasm was induced with topical epinephrine. Flap survival was assessed on day 3, and the success rates of the three groups were compared.

RESULTS

The flap success rate was 73.3% (22 of 30) in group 1, 66.7% (20 of 30) in group 2, and 96.7% (29 of 30) in group 3. The differences between groups 1 and 3 and between groups 2 and 3 were statistically significant. Overall, venous thrombosis was much more frequent than arterial thrombosis.

CONCLUSIONS

In a rat epinephrine-induced vasospasm model, venous thrombosis was much more frequent than arterial thrombosis. The type of arterial anastomosis did not affect the success rate, but end-to-side venous anastomosis had a higher success rate than end-to-end venous anastomosis.

The influence of sildenafil on random skin flap survival in rats: an experimental study

Sildenafil (Viagra), a selective and specific inhibitor of cyclic guanosine monophosphate (cGMP) phosphodiesterases (PDEs), is currently marketed for the treatment of erectile dysfunction. Sildenafil is a potent and highly selective PDE-V inhibitor and enhances smooth muscle relaxation in human. Systemic arterial and venous smooth muscle cells contain PDE-V and nitric oxide (NO) which is a major mediator of relaxation of the smooth muscle cell. The aim of the present study is to investigate, in a rat model, the potential effect of sildenafil on survival of random pattern skin flaps. For this purpose, 32 Sprague-Dawley rats were used and a McFarlane-type caudally based skin flap was designed on the dorsum of the rat (2.5 x 8 cm). Rats were divided into four groups: One control (Group D), and three treatment groups (Groups A, B, C). Sildenafil was administered orally to the experiment groups; Group A: 3 mg/kg/single dose a day, Group B: 10 mg/kg/single dose a day and Group C: 10 mg/kg/twice dose a day. The areas of flap necrosis were measured in each group. The extent of viable flap areas were expressed as a percentage of total flap area, and differences were studied by Completely Randomised Experimental design. The areas of necrosis of skin flaps decreased depending on sildenafil dose, but viability of the flaps treated with 3 mg/kg/day was not different than the control group. The flaps receiving 2 x 10 mg/kg/day sildenafil gave the highest (P < 0.01) survival rate. As a conclusion, sildenafil may have a dose dependent effect to increase flap survival in random skin flaps.

Cardiac and vascular effects of diltiazem, dobutamine and amrinone, drugs used after myocardial revascularization

Hemodynamic care during postoperative management of myocardial revascularization should include vasorelaxing drugs to insure adequate graft and coronary flow, and stimulation of stroke volume to maintain vascular perfusion pressure. We tested the cardiac (inotropic and lusitropic) and vascular (relaxant) effects of diltiazem (0.1 nM to 0.1 mM), dobutamine (10 microM to 10 mM) and amrinone (10 microM to 1 mM) on isolated rat atria and thoracic aorta, and also on isolated human saphenous vein (HSV) and human mammary artery (HMA). Dobutamine produced a maximal positive inotropic effect (+dF/dt max = 29 +/- 7%) at its ED50 for aortic relaxation (88 +/- 7 microM). Conversely, at their ED50 for aortic relaxation diltiazem depressed myocardial contractility and amrinone did not exhibit myocardial effects. In HSV and HMA contracted with 80 mM potassium, diltiazem and dobutamine (but not amrinone) had a vasorelaxant activity similar to that in rat aorta. Norepinephrine-contracted human vessels were significantly more sensitive than potassium-contracted vessels to the relaxant effect of amrinone (ED50 HMA = 15 +/- 5 microM, ED50 HSV = 72 +/- 31 microM, P < 0.05). We conclude that at concentrations still devoid of myocardial effects dobutamine and amrinone are effective dilators in graft segment vessels and rat aorta contracted by membrane depolarization. If the difference between aortic and myocardial tissue still holds in human tissues, at the appropriate concentrations these drugs should be expected to improve cardiac performance while still contributing to the maintenance of graft patency.

Clinical use of amrinone (a selective phosphodiesterase III inhibitor) in reconstructive surgery

Amrinone is a selective phosphodiesterase III inhibitor that increases cyclic adenosine monophosphate by preventing its breakdown. It is effective in the treatment of congestive heart failure because of its ability to increase myocardial contractility and vascular smooth muscle relaxation. This study was designed to clarify the potential efficacy of amrinone in plastic surgery by clinically assessing its ability to enhance flap blood flow after reconstructive surgery and relieve intraoperative vasospasm. Its effects were compared with those of prostaglandin E1 and lidocaine, which are widely approved agents for improving the hemodynamics of flaps. In the first clinical study, the effects on flap blood flow after flap transfers were investigated. Twenty-six patients underwent reconstructive surgery with vascularized free or pedicled flaps. Blood flow was measured before and 60 minutes after intravenous infusion of lactated Ringer solution (control), amrinone (10 microg/kg/min), or prostaglandin E1 (10 ng/kg/min) using a laser Doppler flowmeter. In the second study, the effects on relief of vasospasm during operation were evaluated. The blood flow of 28 island flaps was measured by laser Doppler flowmetry immediately after flap elevation and 10 minutes after topical application of saline (control), amrinone (5 mg/ml), or lidocaine (10%) to the pedicle in an attempt to resolve the vasospasm. In both clinical studies, the effects of amrinone were statistically no less than those of prostaglandin E1 and lidocaine. The results show that amrinone positively influences the microcirculatory blood flow of transferred flaps and relieves intraoperative vasospasm in clinical cases. The present study suggests that amrinone could be useful for postoperative and intraoperative care in reconstructive surgery.