Obstacle Called Vasospasm: Which Solution Is Most Effective in Microsurgery and How to Pharmacologically Assist It?

The success or failure of anastomosis in microsurgery often hinges on addressing vasospasm. This problem becomes even more significant as the caliber of blood vessels decreases. Tactics for affecting vasospasm vary, such as local or systemic application of calcium channel blockers or local application of papaverine or lidocaine.

Assessment of Metamizole's Vasodilatory Effect in Microsurgery 

The effect of papaverine and lidocaine has been demonstrated in numerous animal models in the past. Nowadays, these substances are frequently used in operating rooms during microsurgical procedures.

Metamizole (dipyrone) is a pyrazolone derivative and a widely used nonsteroidal anti-inflammatory drug. It can be administered orally, intramuscularly, or intravenously. It has strong analgesic and anti-inflammatory effects and, according to available studies, also has a relaxing effect on the smooth muscle of the intestine, vas deferens, uterus, aorta, Oddi's sphincter, ureter, and gallbladder. In a rabbit model, metamizole had a vasorelaxant effect on the arteria basilaris.

The aim of the study, the results of which are shown below, was to demonstrate the vasodilatory effect of topically applied metamizole and compare this effect with the commonly used topically applied papaverine and lidocaine. From an economic cost perspective, these three substances do not significantly differ; their prices are comparable.

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Methodology, Course, and Results of the Study

The study was conducted on an animal model. A total of 35 rats were randomly divided into four groups: control group (8 rats), “metamizole” group (9 rats), “papaverine” group (9 rats), and “lidocaine” group (9 rats). The surgical procedures were performed by the same operator and assistant for all groups.

The operator cut both femoral arteries. They were immediately photographed. Their diameter was then measured on the photographs using computer software (Universal Desktop Ruler software version 3.5.3364). The diameter of the femoral arteries of the rats before the local application of the control physiological solution or one of the vasodilatory agents was 0.565 (± 0.05) mm in the control group, 0.589 (± 0.04) mm in the “metamizole” group, 0.594 (± 0.03) mm in the “papaverine” group, and 0.573 (± 0.04) mm in the “lidocaine” group.

After application of the physiological solution in the control group or one of the vasodilatory agents in the remaining groups (metamizole 2.5 g/5 ml; papaverine 40 mg/2 ml; lidocaine 500 mg/5 ml), the diameter of the arteries was measured at intervals of 5, 10, 20, and 30 minutes (again via photographs and computer software). A significant increase in arterial diameter was observed in all groups (except the control). No significant difference was observed between the “metamizole” and “papaverine” groups. However, both metamizole and papaverine caused greater vasodilation than lidocaine. The effect persisted in all groups for the duration of the experiment, i.e., for 30 minutes.

Discussion and Conclusion

The success of microsurgical procedures depends on several variables. One of them is effectively addressing vasospasm. Papaverine and lidocaine are used for this purpose, for example. Although 10% lidocaine was used in this study, which according to previous studies exhibits greater effectiveness than less concentrated solutions, its use did not achieve the same results as metamizole and papaverine.

The spasmolytic and vasodilatory effect of metamizole has been repeatedly demonstrated. The work described above focused on the ability of this drug to affect vasospasm when applied locally in microsurgery. Based on the findings from this study, it can be concluded that locally applied metamizole is as effective in suppressing vasospasm as papaverine and more effective than lidocaine.

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Source: Kaya B., Elçin Işılgan S., Serel S., Ergün H. Metamizole: an effective solution for vasospasm. J Plast Surg Hand Surg 2016; 50 (3): 151–155, doi: 10.3109/2000656X.2015.1137924.