Anaesthesia and the QT interval. Effects of isoflurane and halothane in unpremedicated children

Investigation of proarrhythmic effect of high sugammadex doses: an experimental animal study

BACKGROUND

Studies on higher doses of sugammadex effect on QT interval and leading arrhythmia have been limited. In this study, we aimed to investigate possible proarrhythmic effect of higher doses of sugammadex in conditions that required urgent reversal of neuromuscular blockade during general anesthesia in an experimental animal model.

METHODS

It was experimental animal study. Total of 15 male New Zealand rabbits were randomly divided into three groups for low (4 mg/kg, n = 5), moderate (16 mg/kg, n = 5), and high dose of sugammadex (32 mg/kg, n = 5). All rabbits were premedicated by intramuscular ketamine 10 mg/kg, and general anesthesia was inducted by intravenous injection of 2 mg/kg of a propofol, 1 mcg/kg fentanyl, and 0.6 mg/kg rocuronium injection. Airway was provided by V-gel rabbit and connected to anesthetic device and ventilated at about 40 cycle/min and 10 ml/kg; oxygen 50% plus air 50% mixture was used with 1 MAC isoflurane to maintain anesthesia. Electrocardiographic monitorization and arterial cannulation were provided to follow-up mean arterial pressure and for arterial blood gas analyses. Intravenous sugammadex in three different doses were injected at 25th min of induction. After observing adequate respiration of all rabbits, V-gel rabbit was removed. Parameters and ECG recordings were taken basal value before induction and at the 5th, 10th, 20th, 25th, 30th, and 40th min to measure corrected QT intervals and were stored on digital media. QT interval was calculated as the time from the beginning of the Q wave to the end of the T wave. Corrected QT interval was calculated according to the Bazett's formula. Possible adverse effects were observed and recorded.

RESULTS

In all three groups, there was no significant statistical difference in mean arterial blood gases parameters, arterial pressures, heart rates, and Bazett QTc values, and no serious arrhythmia was recorded.

CONCLUSION

We found in animal study that low, moderate, and high doses of sugammadex did not significantly altered corrected QT intervals and did not cause any significant arrhythmia.

Anaesthetic consideration in patients with cardiac implantable electronic devices scheduled for surgery

With advances in cardiology and cardiothoracic surgery, several newer implantable cardiac devices have become common in the surgical population. Multichamber pacemakers, implanted cardiac defibrillators and ventricular assist devices are frequent in current day practice. Many of the newer implantable cardiac electronic devices are targeted at managing heart failure. While managing such patients for non-cardiac surgeries, specific issues related to equipment characteristics and troubleshooting should be a priority for the anaesthesiologists. There is a possibility of malfunction of the devices resulting in catastrophic outcomes. Therefore, it is imperative to understand the pathophysiology, device characteristics and troubleshooting before embarking on anaesthetising patients with implantable cardiac electronic devices.

Effects of dose ranging of adenosine infusion on electrocardiographic findings during and after general anesthesia

PURPOSE

To assess changes in the electrocardiogram (ECG) associated with intraoperative infusion of adenosine in patients undergoing open abdominal gynecological surgery.

METHODS

One hundred and sixty-six patients undergoing gynecological surgery were randomly assigned to receive one of four doses of adenosine infusion (25, 50, 100, or 200 μg/kg/min) or matching placebo. Study drug administration was started at skin incision and discontinued at end of surgery. A standardized general anesthetic regimen was used and adjusted based on hemodynamic and bispectral index values. Heart rate and rhythm variables, and PR, QRS, QT, and QTc intervals were recorded from 12-lead ECGs before anesthesia and immediately after patient arrival in the postanesthesia care unit. In addition, a rhythm strip was obtained during administration of the loading dose of the study drug. ECG variables were compared within and between groups. Incidence of ECG and hemodynamic abnormalities was recorded.

RESULTS

One hundred and fifty-one subjects had a full set of electrocardiographic data: placebo (n = 38), group adenosine 25 μg/kg/min (n = 31), group adenosine 50 μg/kg/min (n = 29), group adenosine 100 μg/kg/min (n = 28), and group adenosine 200 μg/kg/min (n = 25). Statistically significant postoperative QTc prolongation was observed in all study groups when compared with baseline except for the adenosine 200 μg/kg/min group. However, these changes from baseline were not different among the groups. There were also no significant differences in PR, QRS, and QT intervals between the treatment groups.

CONCLUSION

There was no difference in QTc prolongation following intraoperative administration of adenosine infusion compared with placebo during isoflurane general anesthesia. However, QTc prolongation is common following general anesthesia.

Anesthesia for videoscopic left cardiac sympathetic denervation in children with congenital long QT syndrome and catecholaminergic polymorphic ventricular tachycardia--a case series

OBJECTIVE

To describe our experience in the anesthetic management of pediatric patients who have undergone left cardiac sympathetic denervation (LCSD) for congenital long QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia (CPVT).

BACKGROUND

Long QT syndrome and CPVT predispose patients to ventricular arrhythmias and sudden death. One treatment option for these patients is LCSD. When these patients present for LCSD or other surgical procedures, anesthetic management is challenging, as many medications may exacerbate QT prolongation.

METHODS

Retrospective review of the electronic medical records of 22 pediatric patients who underwent LCSD between November 2005 and December 2008.

RESULTS

Six patients (27%) received midazolam as a premedication. Eleven patients (50%) underwent inhalation induction with sevoflurane. Eighty-six percentage received either sevoflurane or isoflurane for maintenance of anesthesia, while the remaining 14% received a propofol infusion. Nine patients (41%) received esmolol infusions intraoperatively, while one patient (4.5%) received a labetalol infusion. Three patients (14%) received lidocaine infusions. no significant cardiac or other events occurred in any of these patients in the perioperative period.

CONCLUSIONS

Important anesthetic considerations in this population include avoidance of sympathetic stimulation, correction of any abnormal electrolytes, and the immediate availability of a defibrillator and magnesium sulfate to treat arrhythmias. Anxious patients may benefit from premedication to reduce sympathetic tone. We have safely used both volatile agents and propofol for induction and maintenance of anesthesia. In our experience, intraoperative infusions of beta-blockers and lidocaine seem to be helpful in reducing arrhythmogenic potential, especially in patients with profound QT prolongation.

[Long QT syndrome and anaesthesia]

The long QT syndrome (LQTS) is a rare, congenital or acquired disease, which may lead to fatal cardiac arrhythmias (torsade de pointes, TdP). In all LQTS subtypes, TdPs are caused by disturbances in cardiac ion channels. Diagnosis is made using clinical, anamnestic and electrocardiographic data. Triggers of TdPs are numerous and should be avoided perioperatively. Sufficient sedation and preoperative correction of electrolyte imbalances are essential. Volatile anaesthetics and antagonists of muscle relaxants should be avoided and high doses of local anaesthetics are not recommended to date. Propofol is safe for anaesthesia induction and maintenance. The acute therapy of TdPs with cardiovascular depression should be performed in accordance with the guidelines for advanced cardiac life support and includes cardioversion/defibrillation and magnesium. Torsades de pointes may be associated with bradycardia or tachycardia resulting in specific therapeutic and prophylactic measures.

Cardiac risk factors for dental procedures: knowledge among dental practitioners in Wales

OBJECTIVES

To determine knowledge and educational needs of dental practitioners in Wales regarding congenital or acquired cardiac disease and the provision of antibiotic prophylaxis.

DESIGN

Self-administered postal questionnaire.

SETTINGS

Cardiff University Dental Hospital, district general hospitals (HDS), all general dental practices (GDP) and community dental service (CDS) clinics throughout Wales. Methods A questionnaire sent to 1,182 dentists in Wales in 2004-5.

RESULTS

528 questionnaires were returned (a response rate of 45%). These were analysed using one-way analysis of variance to compare summary scores between the occupation groups. Significant differences in knowledge of cardiac risk factors for infective endocarditis and for dental procedures requiring cover were observed between the occupation groups. The majority of dentists (92% GDPs, 94% CDS and 77% HDS) requested postgraduate education in cardiac risk factors and laminated flow diagrams for their surgeries as the preferred educational format.

CONCLUSION

The knowledge of Welsh dentists regarding cardiac conditions or procedures which are risk factors for paediatric and adult patients varied according to place of work. The study identified potential for under- and over-prescription of antibiotic prophylaxis within the current guidance. There was confusion as to which patient groups and cardiac conditions required prophylaxis and for which particular dental procedures. Postgraduate education detailing advances in cardiology practice is necessary for dentists.

The Influence of desflurane on QTc interval

Volatile anesthetics may prolong the QTc interval and this may result in grave cardiac arrhythmias. We assessed the effect of desflurane on the QTc interval in 40 ASA physical status I or II patients. Volatile anesthetic induction with desflurane was performed, and after obtaining adequate level of anesthesia, QTc interval, heart rate, and noninvasive arterial blood pressure were measured. Prolongation of the QTc interval was observed within the first minute of anesthesia. There were no differences in QTc interval changes between sexes at any time. We conclude that desflurane prolongs the QTc interval, but that there are no differences between genders in sensitivity to this action.

IMPLICATIONS

We assessed the effect of desflurane on QTc interval in patients without cardiac diseases. Prolongation of the interval was evident by the first minute of desflurane anesthesia. There were no differences between female and male patients.

Anaesthesia with remifentanil and rocuronium for caesarean section in a patient with long-QT syndrome and an automatic implantable cardioverter-defibrillator

A 24-year-old woman with congenital long-QT syndrome (LQTS) required caesarean section at 32 weeks' gestation. Her risk of premature death from malignant ventricular tachyarrhythmias had necessitated implantation of an automatic cardioverter-defibrillator (AICD) with pacemaker capability. The patient expressed a preference for general anaesthesia. To minimise the risk of increased serum catecholamine concentrations and consequent ventricular arrhythmias, an analgesia-based regimen was chosen. With cardioversion, defibrillation, and antitachycardia pacing functions of the AICD selectively deactivated, anaesthesia was induced with bolus doses of thiopentone and remifentanil. Rocuronium was used for neuromuscular block. Anaesthesia was maintained with nitrous oxide and isoflurane, supplemented by a remifentanil infusion. We outline the pathophysiology and treatment of LQTS, and discuss the anaesthetic management of an obstetric patient with the congenital syndrome. This is the first reported case of caesarean section in a patient with an AICD, and the first description of the use of either remifentanil or rocuronium in LQTS.

Is prolongation of the QTc interval during isoflurane anaesthesia more prominent in women pretreated with anthracyclines for breast cancer? †

BACKGROUND

Inhalation anaesthetics and anthracycline chemotherapeutic drugs may both prolong the QT interval of the electrocardiogram. We investigated whether isoflurane may induce or augment QTc prolongation in patients who had previously received cancer chemotherapy including anthracycline drugs.

METHODS

Forty women undergoing surgery for breast cancer were included in the study. They were divided into two groups: (A) women previously treated with anthracyclines (n=20); and (B) women not treated with antineoplastic drugs (n=20). All patients received a standardized balanced anaesthetic in which isoflurane 0.5 vol% was used. The QT and corrected QT intervals were measured before anaesthesia, after induction and tracheal intubation, after 1, 5, 15, 30, 60 and 90 min of anaesthesia, and during recovery.

RESULTS

In both groups we observed a tendency to QTc prolongation, but statistically significant differences among baseline values and values observed during isoflurane-containing anaesthesia were seen only in group A. During anaesthesia, significant differences in QTc values between the two groups were observed.

CONCLUSION

In female patients pretreated with anthracyclines for breast cancer, the tendency to QTc prolongation during isoflurane-containing general anaesthesia was more strongly expressed than in patients without previous chemotherapy.

Atrioventricular Nodal Ablation and His-Bundle Pacing:. An Acute Canine Model for Proarrhythmic Risk Assessment

INTRODUCTION

QT interval prolongation following drug exposure is considered a marker for increased risk of drug-induced arrhythmias. QT interval measurements are common components of the safety pharmacology assessment of new therapeutic compounds but are potentially confounded by concurrent changes in heart rate that also alter QT intervals. We describe an anesthetized canine model of AV dissociation with His-bundle pacing that overcomes the confounding effects of a change in heart rate.

METHODS AND RESULTS

Transvenous radiofrequency ablation of the AV node was performed in isoflurane-anesthetized dogs and followed by open chest implantation of bipolar pacing electrodes in the vicinity of the His bundle. Pace rates were adjusted from 50 to 190 in steps of 20 beats/min, holding each step for 30 seconds. At each paced rate, QT intervals were measured manually to the nearest 1 ms to construct paced QT interval-heart rate (QT-HR) relationships. Paired QT-HR relationships using identical ascending ramps of pace rates were compared to paired QT-HR relationships with an ascending and descending pace ramp to evaluate short-term reproducibility and hysteresis effects. For proof of concept, an additional QT-HR relationship was constructed in three dogs after intravenous administration of a compound known to alter QT intervals: one dog received terfenadine (0.48 mg/kg bolus followed by 0.017 mg/kg/min infusion), one dog received quinidine (20 mg/kg), and the third dog received sotalol (1 and 3 mg/kg). Substantial inter-dog variation was found for QT-HR, although short-term reproducibility was high within one dog (average absolute difference for paired ascending ramps < 5 ms). QT intervals measured during descending paced ramps were generally lower than the value for the corresponding paced rate on an ascending ramp. This hysteretic effect was small, averaging < 7 ms over the entire ramp. All test compounds prolonged QT intervals and shifted the QT-HR relationship upward. Maximal QT prolongation was 30 ms for terfenadine, 50 ms for quinidine, and 59 ms for sotalol.

CONCLUSION

AV nodal ablation and His-bundle pacing provide a sensitive animal model to identify acute effects of test compounds on indices of myocardial repolarization such as the QT interval. The model is devoid of confounding effects of changing heart rates while enabling identification of effects of drugs over a wide range of controlled rates.

QT dispersion increases during intubation in patients with coronary artery disease

Anesthetic drugs have been shown to increase QT interval, however data regarding their effects on QT dispersion (QTd) are scarce, especially in patients with coronary artery disease (CAD). We tested whether induction of Anesthesia with thiopental and etomidate would increase QTd in patients with CAD. Thirty American Society of Anesthesiologists (ASA) physical status I-II patients without CAD were randomly allocated to groups I (n = 15) and II (n = 15) and 30 ASA physical status III patients with CAD were randomly allocated to groups III (n = 15) and IV (n=15). Anesthesia was induced with thiopental 5-7 mg/kg IV in groups I and III and with etomidate 0.2-0.3 mg/kg IV in groups II and IV. Endotracheal intubation was facilitated with vecuronium bromide 0.1 mg/kg IV. Twelve-lead electrocardiogram (ECG) was recorded in all patients at baseline (ECG(1)), 1 min after the induction agent (ECG(2)), 1 min (ECG(3)) and 5 min (ECG(4)) after intubation. Anesthesia was maintained with isoflurane and nitrous oxide in 34 % oxygen after ECG(2) recording. QTd and corrected QT dispersion (QTcd) were calculated. In patients with CAD induced with thiopental, QT dispersion increased significantly during the intubation period compared with baseline (from 43.0 +/- 25.6 ms to 69.2 +/- 25.3 ms; P <.01). Likewise, QT dispersion also increased during intubation in patients with CAD induced with etomidate (from 41.5 +/- 17.2 ms to 80.0 +/- 33.6 ms; P <.001). There was no increase in QT dispersion in patients without known CAD. QT dispersion seems to be increased during the intubation period in patients with CAD regardless of the induction agents used.

The effects of volatile anesthetics on the Q-Tc interval

OBJECTIVE

To examine the effects of halothane, isoflurane, and sevoflurane on Q-Tc interval (corrected for heart rate) during inhalation induction of anesthesia.

DESIGN

Prospective, double-blind, randomized study.

SETTING

Departments of Cardiology and Anesthesiology in a university hospital.

PARTICIPANTS

Patients undergoing noncardiac surgery.

INTERVENTIONS

A total of 65 American Society of Anesthesiologists physical status I-II patients, aged 16 to 50 years, undergoing general anesthesia, were randomly allocated to receive halothane, isoflurane, or sevoflurane.

MEASUREMENTS AND MAIN RESULTS

The time to reach the predetermined end-tidal concentrations of 3 minimum alveolar concentration was 6 to 10 minutes. When compared with preinduction values, heart rate decreased after halothane (p < 0.01) and sevoflurane (p < 0.05) administration; in contrast, heart rate increased after induction of anesthesia with isoflurane (p < 0.05). The mean QRS intervals were not significantly changed after halothane, isoflurane, or sevoflurane. The Q-Tc interval was increased with isoflurane compared with baseline (465 +/- 23 v 441 +/- 18 msec, p < 0.01), not changed with sevoflurane (441 +/- 17 v 434 +/- 19 ms, p > 0.05), and shortened with halothane (426 +/- 23 v 445 +/- 21 msec, p < 0.01).

CONCLUSION

Sevoflurane or halothane may be preferred to isoflurane in patients with conditions that are known to induce a prolonged Q-Tc interval. The effects of Q-Tc interval changes resulting from different anesthetic agents on morbidity and the incidence of arrhythmias during anesthesia warrant further investigation.

Sevoflurane, but not propofol, significantly prolongs the Q-T interval

Prolongation of the Q-T interval may be associated with polymorphic ventricular tachycardia known as torsade de pointes, syncope and sudden death. Existing data show that isoflurane prolongs the Q-T interval, whereas halothane shortens it. The aim of this study was to determine whether sevoflurane or propofol affects the Q-T interval. Thirty female patients undergoing gynecologic surgery were randomly assigned to two groups, one receiving inhaled induction with sevoflurane and the other receiving total IV anesthesia with propofol. Before and 20 min after the induction, a six-lead electrocardiogram was recorded, and blood pressure was measured. The Q-T interval and heart rate adjusted Q-T interval (Q-Tc interval) were significantly prolonged during the administration of anesthesia with sevoflurane, while the Q-T interval was significantly shortened, and the Q-Tc interval was statistically unaffected during propofol anesthesia administration. We conclude that, in otherwise healthy female patients, sevoflurane prolongs the Q-Tc.

IMPLICATIONS

In this study, we evaluated the effect of sevoflurane induction and anesthesia versus propofol induction and anesthesia on the Q-T interval. Sevoflurane significantly prolonged the Q-T interval and the heart rate adjusted Q-T interval, whereas propofol shortened the Q-T interval but not the heart rate adjusted Q-T interval.