七氟烷对QT间期延长的影响在老年人中更明显

背景七氟炕和氟哌利多能延长QT间期。高龄不仅与QT问期延长有关,它也是一种}j起药物诱导的QT间期延长的危险因素。本研究中,我们比较了七氟炕和氧哌利多对于矫正的QT（QYc）间期和心室复极化的传播（T波波峰至T波结束的时间间隔[Tp-e]）在老年患者和年轻患者中的差别。方法在七氟烷（1．5％-2．5％）麻醉和给予止吐剂量的氟哌利多（1．25rag）的30例老年患者（≥70岁）和30例年轻患者（20—69岁）中,测量2小时QT间期和代表心肌壁复极化传播的Tp—e间期。通过3种不同的公式使心率的QT间期标准化：Bazen公式、Matsunaga公式和Vandewa船公式。数据以均数±标准差表示。结果老年组的平均年龄比年轻组大24．4岁（P〈0．05）。两组的QTc间期在麻醉前没有明显的差异。通过3种公式计算发现七氟烷明显延长老年组患者的QTc间期（用Bazecc公式得出在麻醉前、使用七氟烷60分钟、75分钟、90分钟和120分钟时的QTc间期分别是0．434±0．028秒、0．450±0．037秒、0．463±0．037秒、0．461±0．037秒和0．461±O．038秒）。在老年组患者中七氟炕引起QTc间期延长的程度明显高于年轻组（用Bazecc公式计算吸入七氟烷60分钟时：0．450±0．037秒VS0．432±0．034秒;75分钟时：0．463±0．037秒vs0．441±0．037秒;120分钟时：0．461±0．038秒vs0．436±0．030秒）。但是七氟炕引起的QTc间期的延长既不随着时间的延长而延长也不被氟哌利多加重。两组中的Tp—e间期都没有受到影响。结论与年轻组相比,七氟烷引起老年组患者QTc间期的延长更加明显。尽管七氟烷不影响复极化的透壁传播,其引起的QTc闻期延长也不随着时间和给予氧哌利多而加重,但是老年患者在使用七氖烷麻醉期间仍要严密监测QT间期及其相关的心律失常。     

Effects of sevoflurane on QT parameters in children with congenital sensorineural hearing loss

Sevoflurane prolongs the QT interval (QTI). Patients with congenital sensorineural hearing loss (SNHL) often have a prolonged QTI. This study was to investigate the effects of sevoflurane on the QTI in SNHL and control children. Thirty patients with SNHL and 30 controls were studied. The corrected QT interval (QTc), interval from peak to end of T wave (Tp-e) and QT variability index (QTVI) were analysed. QTc and Tp-e were estimated by the average QTc and Tp-e measured beat-by-beat for 15 min. Heart rate power spectral analysis was performed. In both groups, QTc and QTVI increased during anaesthesia, but Tp-e did not change. There were no differences in QTc, QTVI, Tp-e, low- and high-frequency power between the two groups. In both groups, sevoflurane lengthened the QTc and QTVI intervals but not Tp-e.     

The effects of droperidol and ondansetron on dispersion of myocardial repolarization in children

Objectives: To compare the effects of droperidol and ondansetron on electrocardiographic indices of myocardial repolarization in children. Aim: To refine understanding of the torsadogenic risk to children exposed to anti‐emetic prophylaxis in the perioperative period. Background: QT interval prolongation is associated with torsades des pointes (TdP), but is a poor predictor of drug torsadogenicity. Susceptibility to TdP arises from increased transmural dispersion of repolarization (TDR) across the myocardial wall, rather than QT interval prolongation per se. TDR can be measured on the electrocardiogram as the time interval between the peak and end of the T wave (Tp‐e). Tp‐e may therefore provide a readily available, noninvasive assay of drug torsadogenicity. The perioperative period is one of high risk for TdP in children with or at risk of long QT syndromes. Droperidol and ondansetron are two drugs commonly administered perioperatively, for prophylaxis of nausea and vomiting, which can prolong the QT interval. This study investigated their effects on myocardial repolarization. Methods: One hundred and eight ASA1‐2 children undergoing elective day‐case surgery were randomized to receive droperidol, ondansetron, both or neither. Pre‐ and post‐administration 12‐lead electrocardiogram (ECGs) were recorded. QT and Tp‐e intervals were measured and compared within and between groups, for the primary endpoint of a 25 ms change in Tp‐e. Results: Eighty children completed the study. There were no demographic or baseline ECG differences between groups. QT intervals lengthened by 10–17 ms after allocated treatments, with no between‐group differences. Values remained within normal limits for all groups. Tp‐e intervals increased by 0–7 ms, with no between‐group differences. There were no instances of dysrhythmia. Conclusions: Droperidol and ondansetron, in therapeutic anti‐emetic doses, produce equivalent, clinically insignificant QT prolongation and negligible Tp‐e prolongation, suggesting that neither is torsadogenic in healthy children at these doses.     

术前输注头孢呋辛钠后不同靶控浓度丙泊酚对妇科手术患者心室复极的影响

目的观察术前预防性输注头孢呋辛钠后不同靶控浓度丙泊酚对妇科手术患者心室复极的影响。方法选择择期妇科手术患者59例,年龄18~65岁,ASAⅠ或Ⅱ级,采用随机数字表法分为三组。入室补液并静滴头孢呋辛钠2.5g(溶于100ml生理盐水中)后,分别泵注丙泊酚血浆靶控浓度为2μg/ml(P2组,n=20)、3μg/ml(P3组,n=19)、4μg/ml(P4组,n=20)。分别在抗生素输注前(T_0)、抗生素输注完毕(T_1)、及丙泊酚达到靶控浓度时(T_2),测量并计算QT间期、QTc间期、T波峰值至终点时间(T_p-e间期)及Tp-e/QT。结果与T0时比较,T_1时P4组QTc间期[(469.9±34.0)ms vs.(451.2±24.9)ms]、Tp-e间期[(107±25)ms vs.(94±20)ms]、Tp-e/QT(0.260±0.058vs.0.236±0.043)明显延长(P0.05);与T_1时比较,T_2时P2组[(437.4±24.4)ms vs.(453.3±28.0)ms]和P4组[(438.8±29.9)ms vs.(469.9±34.0)ms]QTc间期明显缩短(P0.05)。结论丙泊酚可改善头孢呋辛钠引起的心室复极不均一性。     

Effects of remifentanil,nitroglycerin, and sevoflurane on the corrected QT and Tp-e intervals during controlled hypotensive anesthesia

Study objectiveControlled hypotension is a preferred method in various surgical operations, but limited data are available for the effects of drug combinations that are used to ensure the desired level of hypotension on cardiac repolarization.DesignRandomized, prospective, double-blinded study.PatientsThe study comprised 65 patients undergoing septorhinoplasty surgery under general anesthesia.InterventionsGroup S received sevoflurane inhalation alone, group R received sevoflurane and remifentanil, and group N received sevoflurane and nitroglycerine in a way that a mean arterial pressure of 60 ± 5 mm Hg was achieved.MeasurementsElectrocardiogram was performed before induction (T1), 30 minutes after induction (T2), and 5 minutes after extubation (T3). Corrected QT (QTc), QT dispersion (QTd), and corrected Tp-e (Tp-ec) intervals and Tp-e/corrected QT (Tp-e/QTc) ratio were calculated.Main resultsQTc prolongation was observed at T2 and T3 in all groups, but only QTc prolongation at T2 was statistically significant in group S (P> .05). Significant prolongation of QTd interval at T2 and T3 was observed in group S (P< .05). In all groups, Tp-ec decreased at T2. However Tp-ec decrease was not statistically significant in group S (P= .103) and group R (P= .058). Tp-e/QTc was significantly decreased on T2 in all 3 groups, and it was returned to baseline at T3 (P< .05).ConclusionThe present study demonstrated that none of the 3 hypotensive anesthesia methods has an overall negative effect on Tp-e and Tp-e/QTc. Therefore, we conclude that all 3 methods can be used safely in terms of proarrhythmic risk, but increased sevoflurane consumption may require more attention due to significant prolongation of QTc and QTd.     

Acquired long QT syndrome and elective anesthesia in children

We present the case of a child who had had a previous episode of torsades de pointes (TdP) and who was scheduled for elective surgery under general anesthesia. The pathophysiology of this condition and the anesthesia concerns are discussed. An 8-year-old male with a history of osteogenic sarcoma had undergone an uneventful limb salvage procedure 2 years earlier. During a subsequent admission to the hospital, he had had a cardiopulmonary arrest with complete recovery. Telemetry electrocardiogram (ECG) rhythm recordings obtained during the event showed TdP that degenerated into ventricular fibrillation, which then terminated spontaneously. On a subsequent ECG, the QTc interval was 694 ms. The prolonged QT interval was attributed to homeopathic use of cesium chloride supplements and the QT interval normalized after cesium was stopped. He presented for an elective procedure and, with an anesthetic plan that emphasized medications without known effect on the QT interval, had an uneventful perioperative course. The optimal anesthesia plan for patients with prolonged QT or those suspected to be at risk for prolongation of the QT interval has not been well described. Available evidence suggests that using total intravenous anesthesia with propofol may be the safest and was used uneventfully in this case. Additionally, this case emphasizes the need to inquire about the use of supplements and naturopathic medications, even in children, that may have life-threatening side effects or interactions with anesthetic agents.     

The assessment of P-wave dispersion and myocardial repolarization parameters in patients with chronic kidney disease

Objective: The risks of sudden death and cardiac arrhythmia are increased in patients with chronic kidney disease (CKD). Here, we aimed to evaluate the indicators of arrhythmias, such as p-wave dispersion (P-WD), QTc dispersion, Tp-e and Tp-e/QT ratio in patients with CKD stages 3–5 on no renal replacement therapy (RRT).

Material and methods: One-hundred and thirty three patients with CKD stages 3–5 and 32 healthy controls were enrolled into the study. No patients received RRT. QTc dispersion, P-WD and Tp-e interval were measured using electrocardiogram and Tp-e/QT ratio was also calculated.

Results: Mean age rates were found similar in patients and controls (60.8?±?14.2 and 61?±?12.9?y, p?=?.937, respectively). Compared patients with controls, P-WD (45.85?±?12.42 vs. 21.17?±?6.6?msec, p?p?p?p?p?p?=?.001) were found to be different. QTc-max and Tp-e interval were found to be similar in both groups.

Conclusion: P-WD and QTc dispersion, Tp-e interval and Tp-e/QTc ratio were found to be increased in with CKD stages 3–5 on no RRT.     

The effects of sevoflurane and propofol on QT interval and heterologously expressed human ether-a-go-go related gene currents in Xenopus oocytes

Sevoflurane can induce prolongation of the cardiac QT interval by inhibiting the repolarization phase of the action potential. This may occur as a result of inhibition of the human ether-a-go-go related gene (HERG) channel. To clarify the mechanisms of anesthetics on HERG channels, we monitored the electrocardiogram and measured QT intervals in the guinea pig in the presence of sevoflurane and propofol. Sevoflurane (1%-4%) prolonged QTc dose-dependently (7.5%-21.2%), but propofol did not affect it. Furthermore, HERG channels were expressed in Xenopus oocytes and outward HERG currents were obtained on step depolarization from a holding potential of -70 mV. Repolarization to -70 mV from positive test potentials resulted in large outward tail currents. Sevoflurane (1%-4%), in a dose-dependent manner, inhibited the HERG outward tail currents (9.7%-26.6%), whereas steady-state currents were inhibited only at large concentrations. The time constant of the converging current was decreased in the presence of sevoflurane, but the inactivation and activation curves were not shifted. Propofol did not affect these currents within the clinically relevant concentration. In conclusion, compared with steady-state currents, sevoflurane was more potent in inhibiting the outward tail currents, suggesting that sevoflurane may modulate the HERG channel kinetics in its inactivated state.     

QT dispersion in patients with end-stage renal failure and during hemodialysis.

Interlead variability of the QT interval in surface electrocardiogram (ECG), i.e., QT dispersion, reflects regional differences in ventricular recovery time, and it has been linked to the occurrence of malignant arrhythmias in different cardiac diseases. The purpose of the study was to assess the effect of hemodialysis on QT and corrected QT (QTc) interval and dispersion in chronic hemodialyzed patients. Data of 34 nondiabetic patients (male/female = 21/13; mean age, 54 +/- 15 yr) on chronic hemodialysis were studied. Polysulfone capillaries and bicarbonate dialysate containing (in mEq/L) 135 Na+, 2.0 K+, 1.5 Ca2+, and 1.0 Mg2+ were used. Simultaneous 12-lead ECG were recorded before and after hemodialysis in a standard setting. The QT intervals for each lead were measured manually on enlarged (x3) ECG by one observer using calipers. Each QT interval was corrected for patient heart rate: QTc = QT/square root of RR (in milliseconds [ms]). The average cycle intervals were 853 +/- 152 ms predialysis and 830 +/- 173 ms postdialysis; the difference was not significant. The maximal QT interval changed significantly from 449 +/- 43 to 469 +/- 41 ms (P < 0.01). The corrected maximal QT interval increased significantly from 482 +/- 42 to 519 +/- 33 ms (P < 0.01). The QT dispersion changed from 56 +/- 15 to 85 +/- 12 ms (P < 0.001) and the corrected QT interval dispersion from 62 +/- 18 to 95 +/- 17 ms (P < 0.001). During hemodialysis, the serum potassium and phosphate levels decreased from 5.5 +/- 0.8 to 3.9 +/- 0.5 (mM) and from 2.3 +/- 0.5 to 1.6 +/- 0.4 (mM), respectively, whereas calcium increased from 2.2 +/- 0.23 to 2.5 +/- 0.22 (mM). It is concluded that hemodialysis increases the QT and QTc interval and QT and QTc dispersion in patients with end-stage renal failure. Thus, it may be stated that the nonhomogeneity of regional ventricular repolarization increases during hemodialysis. Measurement of QT and QTc dispersion is a simple bedside method that can be used for analyzing ventricular repolarization during hemodialysis.     

Sustained prolongation of the QTc interval after anesthesia with sevoflurane in infants during the first 6 months of life

BACKGROUND: Sevoflurane, an inhalational anesthetic frequently administered to infants, prolongs the QT interval of the electrocardiogram in adults. A long QT interval resulting in fatal arrhythmia may also be responsible for some cases of sudden death in infants. As the QT interval increases during the second month of life and returns to the values recorded at birth by the sixth month, we evaluated the effect of sevoflurane on the QT interval during and after anesthesia in this particular population. METHODS: In this prospective two-group trial we examined pre-, peri-, and postoperative electrocardiograms of 36 infants aged 1 to 6 months scheduled for elective inguinal or umbilical hernia repair. Anesthesia was induced and maintained with either sevoflurane, or the well-established pediatric anesthetic halothane. Heart rate corrected (c) QTc and JTc interval (indicator of intraventricular conduction delays) were recorded from electrocardiograms before and during anesthesia, and at 60 min after emergence from anesthesia. RESULTS: Prolonged QTc was observed during sevoflurane anesthesia (mean [+/-SD], 473 +/- 19 ms, P< 0.01). Sixty minutes after emergence from anesthesia, QTc was still prolonged (433 +/- 15 ms) in infants treated with sevoflurane compared with those treated with halothane (407 +/- 33 ms, P< 0.01). Analogous differences were found for the JTc interval. CONCLUSIONS: Despite a shorter elimination time than better known inhalational anesthetics, sevoflurane induction and anesthesia results in sustained prolongations of QTc and JTc interval in infants in the first 6 months of life. Electrocardiogram monitoring until the QTc interval has returned to preanesthetic values may increase safety after sevoflurane anesthesia.     

Sustained Prolongation of the QTc Interval after Anesthesia with Sevoflurane in Infants during the First 6 Months of Life

Background: Sevoflurane, an inhalational anesthetic frequently administered to infants, prolongs the QT interval of the electrocardiogram in adults. A long QT interval resulting in fatal arrhythmia may also be responsible for some cases of sudden death in infants. As the QT interval increases during the second month of life and returns to the values recorded at birth by the sixth month, we evaluated the effect of sevoflurane on the QT interval during and after anesthesia in this particular population.

Methods: In this prospective two-group trial we examined pre-, peri-, and postoperative electrocardiograms of 36 infants aged 1 to 6 months scheduled for elective inguinal or umbilical hernia repair. Anesthesia was induced and maintained with either sevoflurane, or the well-established pediatric anesthetic halothane. Heart rate corrected (c) QTc and JTc interval (indicator of intraventricular conduction delays) were recorded from electrocardiograms before and during anesthesia, and at 60 min after emergence from anesthesia.

Results: Prolonged QTc was observed during sevoflurane anesthesia (mean [+/-SD], 473 +/- 19 ms, P < 0.01). Sixty minutes after emergence from anesthesia, QTc was still prolonged (433 +/- 15 ms) in infants treated with sevoflurane compared with those treated with halothane (407 +/- 33 ms, P < 0.01). Analogous differences were found for the JTc interval.     

The effect of intravenous lidocaine on QT changes during tracheal intubation

Laryngoscopy and tracheal intubation may provoke changes of cardiac repolarisation. The aim of this study was to assess the effect of intravenous lidocaine on the ECG changes induced by laryngoscopy and tracheal intubation. Forty-three female patients were randomly allocated to receive lidocaine (1.5 mg.kg⁻¹) or placebo immediately after induction of anaesthesia and changes in the ECG and arterial blood pressure were recorded. Correction of QT interval was calculated using Bazett's formula (QTcb), Fridericia's correction (QTcf), and Framingham formula (QTcF). Transmural dispersion of repolarisation (TDR) was determined as Tpeak-Tend time. There were no changes in the QTc value in the lidocaine group. In the placebo group, significant increases in QTcb, QTcf and QTcF values were observed after intubation compared to either control measurements or to comparative measurements in the lidocaine group. There were no significant differences in TDR either between or within the groups. Lidocaine diminishes prolongation of QTc, induced by tracheal intubation but there is no effect of intubation on TDR.     

Effects of sevoflurane versus propofol on QT interval.

BACKGROUND: Prolongation of the QT interval is an alteration of the electrocardiogram (ECG) that may result in a potentially dangerous polymorphic ventricular tachycardia known as torsade de pointes. Michaloudis et al. investigated the effect of isoflurane and halothane on the QT interval in premedicated and non premedicated children, and in premedicated adults. Isoflurane significantly prolonged the QTc interval, in contrast to halothane, which shortened the QTc interval. The aim of the study was to evaluate the effect of sevoflurane on the QT interval in patients undergoing non-cardiac surgery. METHODS: One hundred and eighty patients classified as ASA physical status I-III were enrolled and 102 were excluded. Patients had been scheduled for elective non cardiac surgery. Exclusions criteria were: cardiovascular impairment or chronic obstructive lung disease, medication affecting QT interval, and an abnormal prolongation of the QTc interval (440 ms). The patients were then randomly allocated to one of two groups, one receiving sevoflurane anesthesia and the other receiving propofol anesthesia. In all patients, a 12 lead ECG was recorded before surgery, after intubation, after extubation. The investigators reading the ECG were blinded to the type of induction and anesthesia used. The following variables were recorded or calculated: heart rate, P-R interval, QRS interval, QT interval, QTc interval according to Bazett's formula, systolic, diastolic and mean blood pressure. RESULTS: The sevoflurane significantly prolongs the QT and the QTc interval, whereas the induction and total intravenous anesthesia with propofol significantly shortens the QT but not the QTc interval. CONCLUSIONS: The amount the sevoflurane-associated QT prolongation may possibly be of clinical significance in some patients presenting long QT syndrome, hypokalemia, or in presence of other agents or factors that lengthen QT.     

QT interval,heart rate and arterial pressures using propofol,thiopentone or methohexitone for induction of anaesthesia in children

The effects on corrected QT interval (QTc), heart rate and arterial pressure were studied after induction with propofol 1.5, 2 or 2.5 mg'kg^-1, thiopentone 5 mg-kg^-1 or methohexitone 2 mg-kg^-1 in 123 ASA class I or II children undergoing outpatient otolaryngological surgery. Premedication consisted of oral midazolam and atropine. The children were randomly allocated to one of the three propofol groups or to the thiopentone or methohexitone group. After injection of the intravenous anaesthetic, the QTc interval was significantly prolonged after propofol 2.5 mg. kg^-1. Thirty seconds after suxamethonium 1.5 mg kg^-1, a significant prolongation of the QTc interval occurred in the thiopentone and propofol 1.5 and 2 mg-kg^-1 groups. After intubation, no further prolongation of the QTc interval occurred in any of the groups. Heart rate increased significantly after the barbiturates but not after propofol. Systolic arterial pressure decreased significantly after propofol 1.5 and 2.5 mg kg^-1. In all groups a cardiovascular intubation response occurred. Bradycardia and junctional rhythm occurred in 4% of the children in both barbiturate groups and in 19–29% in the propofol groups. It is concluded that propofol causes prolongation of the QT interval and results in a higher incidence of bradycardia and junctional rhythm than the barbiturates.     

Mechanism of QT interval prolongation induced by sevoflurane in guinea-pig ventricular myocyte

BACKGROUND: Sevoflurane causes QT interval prolongation clinically, but its precise mechanism has not been clarified. We examined the mechanism of QT interval prolongation induced by sevoflurane by means of electrophysiological technique in guinea-pig ventricular myocyte. METHODS: Electrocardiogram was recorded in guinea-pig and effect of sevoflurane (1, 2, 4%) was examined. Action potential (AP), delayed rectified potassium current (IKr), and L-type calcium channel current (ICa) were monitored as whole-cell current and by voltage clamp techniques in guinea-pig single ventricular myocytes. Sevoflurane was applied by bubbling into the bathing solution. RESULTS: Sevoflurane (1, 2, 4%) increased QTc value. Sevoflurane prolonged the duration of AP at 2%, but shortened it at 6%. IKr was reduced to 35% of control in the presence of 2% sevoflurane, but a higher concentration (6%) did not show further inhibition. ICa was reduced only to 87% of control in the presence of 2% sevoflurane and the reduction was dose-dependent (4, 6%). CONCLUSIONS: Sevoflurane 2% inhibited IKr, but it showed only slight inhibition on ICa. Because the duration of AP is regulated by ICa (plateau phase) and IKr (repolarization), greater inhibition of IKr than ICa could result in prolongation of AP. It is suggested that this mechanism may play a role in QT interval prolongation under sevoflurane anesthesia.     

Prolongation of the QT interval by volatile anesthetics in chronically instrumented dogs

The influence of volatile anesthetics on ventricular repolarization in vivo (QT interval) has not been studied in a systematic fashion. The purpose of this investigation was to characterize the electrocardiographic and hemodynamic actions of the volatile anesthetics halothane, isoflurane, and enflurane in chronically instrumented dogs. Because autonomic nervous system tone may influence ECG findings, experiments were completed with and without concomitant pharmacologic autonomic nervous system blockade. In six groups comprising 50 experiments with 21 instrumented dogs, anesthesia was mask-induced with nitrous oxide, oxygen, and one of the volatile anesthetics and maintained with the volatile anesthetic in 100% oxygen for 2 hours. Changes in the ECG and in hemodynamics were compared to the conscious state. In the absence of autonomic nervous system blockade, halothane and isoflurane significantly prolonged the QT interval (0.24 +/- 0.01 to 0.30 +/- 0.01 second and 0.22 +/- 0.01 to 0.28 +/- 0.01 second, respectively), whereas enflurane produced no change in ventricular repolarization (0.24 +/- 0.01 to 0.26 +/- 0.01 second). All of the volatile anesthetics increased the QT interval corrected for changes in basal heart rate (QTc), and all agents decreased intravascular pressure and dP/dt. Following autonomic nervous system blockade, halothane, isoflurane, and enflurane significantly increased the QT interval and QTc. The results demonstrate that ventricular repolarization is directly altered by the volatile anesthetics independent of changes in autonomic nervous tone. Whether or not such effects are additive with other congenital or acquired forms of QTc prolongation has yet to be examined. The present results indicate that caution should be used during the administration of volatile anesthetics to patients with abnormalities of the QT interval.     

异丙酚对兔心室M细胞和外膜层心肌细胞动作电位特性的影响

目的 评价异丙酚对兔心室M细胞及外膜层心肌细胞动作电位特性的影响.方法 新西兰大耳白兔48只,体重2～3 kg,经3%戊巴比妥钠30 mg/kg麻醉后建立离体心脏灌注模型,随机分为3组(n=16),对照组(C组)持续灌注标准台氏液;不同浓度异丙酚组(P1组和P2组)分别灌注含异丙酚10、50μmol/L的标准台氏液.三组均于标准台氏液平衡灌注60 min时,应用传统玻璃微电极技术测定M细胞及外膜层心肌细胞静息膜电位(RMP)、动作电位幅值(APA)和动作电位复极90%的时程(APD90),计算心室复极离散度(TDR)为基础值,异丙酚持续灌注60 min后测定M细胞及外膜层心肌细胞上述参数,计算TDR.结果 三组心室M细胞及外膜层心肌细胞的RMP和动作电位参数基础值差异无统计学意义(P>0.05);与c组比较,P1组和P2组心肌持续灌注期间心室M细胞及外膜层心肌细胞APD90伽缩短,P2组TDR降低(P<0.05),P1组TDR差异无统计学意义(P>0.05);与P1组比较,P2组心室M细胞及外膜层心肌细胞APD90缩短,TDR降低(P<0.05),RMP及APA比较差异无统计学意义(P>0.05).结论 异丙酚可缩短心室M细胞和外膜层心肌细胞动作电位时程,但不增加复极离散度,对心电活动具有一定的稳定效应.     

QT interval of the ECG, heart rate and arterial pressure using propofol, methohexital or midazolam for induction of anaesthesia

The effects of propofol 2 mg/kg, methohexital 2 mg/kg or midazolam 0.3 mg/kg were studied on the QT interval of the ECG corrected by the heart rate (QTc), heart rate and arterial pressure during induction of anaesthesia in 87 ASA class I-(II)-patients. The patients were randomly allocated to one of the three anaesthetic groups. The incidence of the patients with a prolonged QTc interval (= more than 440 ms) ranged from 29 to 41% between the groups. In each group these patients were treated separately. After all anaesthetics, the QTc interval was significantly prolonged in the patients with a normal control QTc interval, whereas in the patients with a prolonged control QTc interval, it tended to be shortened both after propofol and methohexital and it was significantly shortened after midazolam. After injection of suxamethonium, no significant QTc interval changes occurred in the patients with a normal control QTc interval in either the propofol or the methohexital groups, whereas in the patients with a prolonged control QTc interval treated with propofol the QTc interval decreased significantly 60 s after suxamethonium when compared with the corresponding preceding values. The mean values in the propofol group in the patients with a normal control QTc interval were always below the upper limit of the normal range.(ABSTRACT TRUNCATED AT 250 WORDS)     

Impact of haemodialysis on QTc dispersion in children

BACKGROUND: The purpose of the present paper was to investigate the corrected QT (QTc) interval and QTc dispersion value, and the impact of haemodialysis on these parameters in children with chronic renal failure. METHODS: Nineteen patients with chronic renal failure receiving haemodialysis were included in the present study. Electrocardiography (ECG), echocardiography and serum biochemistry were performed in all patients. Serum electrolyte levels were measured before and after haemodialysis, at the time of the ECG. Nineteen healthy age- and sex-matched children served as the control group. RESULTS: Patients with chronic renal failure had greater QTc interval and QTc dispersion compared to control subjects. The patients' sex, age and presence of hypertension or left ventricular hypertrophy (LVH) were not related to QTc interval/dispersion. However, the patients with left ventricular (LV) systolic dysfunction had significantly greater QTc dispersion value. After haemodialysis session, both QTc interval and QTc dispersion values significantly increased. Serum potassium levels significantly decreased, whereas the calcium level significantly increased after the haemodialysis session. The changes in electrolyte values were not associated with the changes in both QTc interval and QTc dispersion. CONCLUSION: Children receiving haemodialysis may be at greater risk of ventricular arrhythmia and sudden death because QTc dispersion reflects heterogeneous recovery of ventricular excitability.     

The effects of sevoflurane and desflurane anesthesia on QTc interval and cardiac rhythm in children

BACKGROUND: Inhalational anesthetics may prolong QTc interval (QT interval corrected for heart rate) of the ECG and cause life-threatening arrythmias. The effects of desflurane on QTc interval and cardiac rhythm have not been reported previously in children. We assessed the effects of desflurane anesthesia on QTc interval and cardiac rhythm and compared them with sevoflurane anesthesia in children. METHODS: The study was performed on 20 children admitted for inguinal hernia repair, with normal QTc intervals. Anesthesia was induced with propofol and intubation was achieved with vecuronium. Anesthesia was maintained with 2% sevoflurane (group I, n = 11) or 6% desflurane (group II, n = 9) and 66% nitrous oxide in oxygen. Electrocardiogram recordings were obtained by Holter recorder. QTc intervals were measured at baseline, 5, 10, 15, and 30 min after inhalation. RESULTS: None of the patients had significant arrythmia with desflurane anesthesia. One patient in the sevoflurane group had single, bigemini and multiform ventricular extrasystoles. There was no statistically significant difference in the baseline QTc values of the groups. Desflurane significantly prolonged QTc interval 5 min after induction until 30 min of anesthesia compared with baseline values (P = 0.029), while no significant prolongation was observed with sevoflurane (P = 0.141). CONCLUSIONS: Use of 2% sevoflurane during maintenance of anesthesia does not significantly prolong QTc interval while 6% desflurane significantly prolonged QTc interval in children with normal QTc interval undergoing inguinal herniorrhaphy.