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"Emergency medicine" 6 (61) 2014

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Dynamic of Parameters of Corrected QT and QT Dispersion and Theirs Prognostic Value in Patients with Coronary Artery Disease under Epidural Anesthesia with Different Local Anesthetic Agents

Authors: Svitlyk Y.O. - Lviv National Medical University named after Danylo Galytsky, Ukraine

Categories: Medicine of emergency

Sections: Clinical researches

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epidural anesthesia, local anesthetic agents, coronary artery disease, corrected QT interval, dispersion of QT interval

Summary. Objective. The paper describes the dynamics of corrected QT interval (QTc) and its dispersion in the perioperative period in patients with coronary artery disease (CAD) operated for the inguinal hernia using an epidural anesthesia (EA). We have determined the relationship between the examined parameters and use of lidocaine, bupivacaine and ropivacaine.

Methods. Eighty seven males who were operated for the inguinal hernia under an EA were examined. Group I (55 patients, mean age 55.27 ± 1.83 years old) with CAD, stable angina (NYHA I–III) was randomly divided into 3 subgroups: the subgroup 1 (15 patients) consisted of the persons who had an EA with a local anesthetic (LA) lidocaine (2 %); the subgroup 2 (25 patients) and subgroup 3 (15 patients) received ropivacaine (0.75 %) and bupivacaine (0.5 %), respectively. The group II included 32 healthy individuals (mean age 50.09 ± 2.24 years old), which were randomly divided into 3 subgroups, in which an EA was performed using lidocaine (subgroup 1 — 8 patients), ropivacaine (subgroup 2 — 13 persons) and bupivacaine (subgroup 3 — 11 patients).

The control group consisted of healthy volunteers: 12 men aged 35 to 65 years old (mean age 54.06 ± 3.74 years old), in which the absence of CAD was confirmed with an exercise test (bicycle ergometer). The patients of the control group were undergone echocardiography, HolterECG monitoring, registration of 12-lead ECG, blood biochemistry.

Results. We have found specific myocardium repolarization depending on the administered anesthetic.

In patients with lidocaine anesthesia the average value of QTc interval increased by 5 % (p < 0.05), but 3 hours after anesthesia the value returned to the initial level. After 24 hours QTc interval value tended to a slight increase (+2.63 %, p > 0.05).

Under ropivacaine QTc interval has increased by 10.53 % (p < 0.05) while anesthesia development. Within 3 hours we observed a reduction of its value by 5 % (p < 0.05), but up to 24 hours after anesthesia QTc did not reach initial values and statistically significantly exceeded the normal range.

In the group of the patients undergone epidural bupivacaine administration, the average QTc intervalin creased by 5 % (p< 0.05). A day after surgery QTc decreased by 2.44 % (p < 0.05), but did not reach a baseline.

QT dispersion in patients who had anesthesia with lidocaine decreased by 20 % (p > 0.05), and to the end of the day — by 40 % (p < 0.05). On the background of ropivacaine administration QTd increased slightly over 3 hours and within 24 hours decreased by 20 %. The same situation was observed under anesthesia with bupivacaine. The dynamic of QTc interval and its dispersion was more favorable during lidocaine administration, and among two other local anesthetics bupivacaine had better safety profile.

We compared the changes of QT interval characteristics in the patients with CAD and without it depending on the chosen local anesthetic.

In the patients with CAD and without CAD undergone EA with lidocaine the initial value of QTc was equal. In the beginning of surgical intervention the average meaning of QTc increased in both groups, however in patients with CAD its increment was 8 % (p < 0.05) and in the patients without CAD — by 5 % (р < 0.05). Three hours after anesthesia QTc decreased in both groups, and in patients without CAD it became lower than the initial level and practically returned to the normal parameters. The 24 hours after the epidural anesthesia average level of QTc in patients with CAD remained on the beginning level, and in the patients without CAD it didn’t have a tendency to increase.

In the groups of epidural ropivacaine and bupivacaine a significant increase of QTc value was observed in the patients with CAD. Predictably, after 3 and 24 hours from the beginning of anesthesia mean values of QTc had tendency to normalization, while in the patients with CAD decrease of QTc was less evident.

It should be noted, that increase of QTc mean values during the surgery in the patients with CAD was less prominent in lidocaine and bupivacaine administration.

Positive dynamics of QTd was observed within 24 hours, it was highr in case of anesthesia with lidocaine and bupivacaine (with some superiority of lidocaine). It should be noted, that QT dispersion increased by 16.67 % (р > 0.05) from initial value in first hours after surgery during ropivacaine anesthesia in the patients with CAD that indicated a tendency to decrease of electrical stability of myocardium.

Conclusions. The patients undergone a surgery for inguinal hernias under EA had increased values of QTc and QT dispersion, that indicates a decrease in myocardial electrical stability and increased risk of life-threatening ventricular arrhythmias — ventricular tachycardia and ventricular fibrillation. Insignificant decrease was observed within 24 hours after surgery, the average values of these parameters didn’t return to the normal ones. More evident changes of QT interval parameters were observed in patients with CAD.

Violation of myocardium repolarization homogeneity and the decrease of its electrical stability are less intensive under epidural lidocaine. In comparison with other two anesthetic agents (ropivacaine and bupivacaine) bupivacaine had better safety profile in patients with CAD.

Increasing parameters of QTc and its dispersion in the patients during EA may be the criteria for increased risk of the life-threatening arrhythmias in the perioperative period.

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