Influence of anaesthesia on defibrillation threshold

Propofol dose and efficacy of defibrillation testing during implantation of subcutaneous implantable cardioverter-defibrillators: A retrospective, single center cohort study

INTRODUCTION

Defibrillation testing (DFT) is recommended during subcutaneous implantable cardioverter-defibrillator (S-ICD) implantation. Previous studies analyzing the potential interference of propofol with defibrillation threshold are inconsistent. The purpose of this study was to analyze whether propofol affects DFT post S-ICD placement.

METHODS

All patients with S-ICD implantation between 01/2017 and 11/2020 at the University Heart Center Freiburg were retrospectively analyzed. Two groups were generated depending on the success of the first shock during DFT. Implantation characteristics and dose of anesthetics were analyzed.

RESULTS

In 12 of the included 80 (15%) patients, first shock during DFT failed. The absolute dose of propofol was significantly higher in patients with first shock failure (median 653 mg [IQR 503-855]) compared to patients with first shock termination (376 mg [200-600]; p = 0.027). Doses of opioids and midazolam as well as type of anesthesia did not differ between the groups. A multivariable binary logistic regression analysis confirmed an independent association of first shock termination and propofol dose (per 100 mg: OR 0.73 (95% CI: 0.56-0.95); p = 0.021).

CONCLUSION

There is an independent association of propofol dose and first shock failure in routine S-ICD defibrillation testing.

Anesthesia for Insertion of Implantable Cardioverter Defibdilators

The use of implantable cardioverter defibrillators (ICDs) for patients at risk for sudden death from ventricular tachycardia or ventricular fibrillation has steadily in creased since the 1980s. ICDs have undergone a signifi cant evolution over the past 2 decades, initially requir ing thoracotomy for placement of epicardial patches to the modern-day devices that involve only transvenously placed leads. Indications for the placement of ICDs are expanding. This article reviews the perioperative anes thetic management of patients undergoing insertion of ICDs. Preoperative assessment of patients for ICD place ment includes careful assessment of underlying medical disease as well as specific determination of the need for continuation or discontinuation of perioperative antiar rhythmic agents. It is important to consider the poten tial effects of anesthetic choice both on hemodynamic stability in patients with limited cardiac reserve and on the ability to intraoperatively induce, and subsequently treat, ventricular dysrhythmias. The relative merits of inhalational and intravenous general anesthesia, as well as those of local anesthesia and intravenous seda tion, should therefore be considered. The present re view also addresses issues of myocardial stunning from repeated defibrillation, cerebral function in the context of repeated circulatory arrest, appropriate intraopera tive monitoring, and postoperative care of patients undergoing ICD placement.

Safe and effective use of conscious sedation for defibrillation threshold testing during ICD implantation

BACKGROUND

Over a period of years general anesthesia has been a standard anesthetic technique for defibrillation threshold (DFT) testing at the time of implant. DFT testing without general anesthesia cover has gained limited acceptance. Use of local anesthesia combined with deep sedation for DFT testing might facilitate and simplify these procedures by reducing the procedural time, staff time, avoiding inefficient service in organizing anesthetic cover; thereby improving patient compliance.

OBJECTIVE

The objective of this study was to evaluate feasibility, safety and efficacy of conscious sedation for DFT testing during Implantable cardioverter defibrillators (ICD) implantation.

METHOD

Data of 87 non-selected patients who achieved adequate sedation with titrated doses of midazolam and pethidine were analyzed retrospectively. These medications were administered by a circulating nurse under the supervision of the implanting physicians. All hemodynamic measures, treatment and complications were monitored and recorded throughout the procedure.

RESULTS

A retrospective analysis of data from 87 patients who underwent ICD implantation and DFT testing under conscious sedation at our center was reported. The mean dose of midazolam and pethidine administered was 4.9 ± 1.8 and 47.7 ± 20 mg, respectively. During the period of conscious sedation, no patient depicted episode of sustained apnea. No major complication or mortality was reported.

CONCLUSION

Use of conscious sedation as an alternative to the use of general anesthesia for DFT testing during ICD implantation is found to be feasible, safe and effective, with an added advantage of reduced procedural time and improved patient compliance.

[Implantation of cardioverter-defibrillators. How much anesthesia is necessary?]

Updated cardiologic guidelines constitute the background for an extended spectrum of indications for the implantation of automatic implantable cardioverter defibrillators (AICDs) and lead to an increasing number of operative implantations of AICDs. Moreover, during implantation of devices for cardiac resynchronization therapy the anesthesiologist is responsible for the most critically ill patients with the longest duration of surgery. As a result anesthesiologists face an increasing number of critically ill patients, whose management contributes to perioperative outcome. Automatic implantable cardioverter defibrillators can be implanted either during general anesthesia, local anesthesia or during a combination of local anesthesia combined with deep conscious sedation accomplished by an anesthesiologist. Besides economic aspects there is an increasing demand for anesthesia with the least cardiovascular side effects and rapid recovery in the often seriously ill patient with preexisting limitations of cardiac and pulmonary functions. Accordingly procedure and anesthesia-associated risks are reviewed and an algorithm for anesthesia management is suggested.

Intraoperative hypothermia increased defibrillation energy requirements

We describe two patients with newly implanted automatic implantable cardioverter-defibrillators that had excessive defibrillation thresholds associated with hypothermia at intraoperative defibrillation threshold testing. Normal defibrillation threshold levels were obtained during postoperative non-invasive electrophysiology testing in an electrophysiology laboratory when the patients were normothermic. We hypothesize that inadvertent intraoperative hypothermia during device implantation may increase the defibrillation threshold.

The dilemma of ICD implant testing

Ventricular fibrillation (VF) has been induced at implantable cardioverter defibrillator (ICD) implant to ensure reliable sensing, detection, and defibrillation. Despite its risks, the value was self-evident for early ICDs: failure of defibrillation was common, recipients had a high risk of ventricular tachycardia (VT) or VF, and the only therapy for rapid VT or VF was a shock. Today, failure of defibrillation is rare, the risk of VT/VF is lower in some recipients, antitachycardia pacing is applied for fast VT, and vulnerability testing permits assessment of defibrillation efficacy without inducing VF in most patients. This review reappraises ICD implant testing. At implant, defibrillation success is influenced by both predictable and unpredictable factors, including those related to the patient, ICD system, drugs, and complications. For left pectoral implants of high-output ICDs, the probability of passing a 10 J safety margin is approximately 95%, the probability that a maximum output shock will defibrillate is approximately 99%, and the incidence of system revision based on testing is < or = 5%. Bayes' Theorem predicts that implant testing identifies < or = 50% of patients at high risk for unsuccessful defibrillation. Most patients who fail implant criteria have false negative tests and may undergo unnecessary revision of their ICD systems. The first-shock success rate for spontaneous VT/VF ranges from 83% to 93%, lower than that for induced VF. Thus, shocks for spontaneous VT/VF fail for reasons that are not evaluated at implant. Whether system revision based on implant testing improves this success rate is unknown. The risks of implant testing include those related to VF and those related to shocks alone. The former may be due to circulatory arrest alone or the combination of circulatory arrest and shocks. Vulnerability testing reduces risks related to VF, but not those related to shocks. Mortality from implant testing probably is 0.1-0.2%. Overall, VF should be induced to assess sensing in approximately 5% of ICD recipients. Defibrillation or vulnerability testing is indicated in 20-40% of recipients who can be identified as having a higher-than-usual probability of an inadequate defibrillation safety margin based on patient-specific factors. However, implant testing is too risky in approximately 5% of recipients and may not be worth the risks in 10-30%. In 25-50% of ICD recipients, testing cannot be identified as either critical or contraindicated.

Can we implant cardioverter defibrillator under minimal sedation?

Aim In a prospective study, we tested the feasibility of implantable cardioverter-defibrillator (ICD) implantation under local anaesthesia (LA) with minimal sedation (MS) vs. short general anaesthesia (SGA) for defibrillation test (DT).

METHODS AND RESULTS

We implanted ICDs in 118 patients between October 2002 and November 2003. Surgery was performed under LA with MS. Depending on the day of admission, patients had DT without SGA with a shock delivered when patient is unconscious (MS group, n = 73) or with short general anaesthesia (SGA group, n = 45). The patients were asked to rate the intensity of pain on a 10-point visual analogue scale (VAS) at the end of the implantation procedure and for the patient of MS group just after DT (VAS-DT). Visual analogue scale was not influenced by the type of anaesthesia (MS vs. SGA). Univariate analysis showed that NYHA >III, 3 leads implanted and an incomplete understanding of the explanation on the procedure were risk factors of VAS >4. Only understanding of the explanation on the procedure has an influence on pain in multivariate analysis.

CONCLUSION

ICD implantation under MS even for DT is feasible and acceptable for the patient.

Anesthetic management for cardioverter-defibrillator implantation in a patient with Kearns-Sayre syndrome

Kearns-Sayre syndrome (KSS) is a rare mitochondrial myopathy and often involves cardiac conduction abnormality and muscle weakness. We report a patient with KSS who had an implantable cardioverter-defibrillator (ICD) implanted during general anesthesia with propofol and nitrous oxide (N2O). These anesthetics did not show any effects on respiration, cardiac conduction, or neuromuscular transmission in this case. The surgery was performed successfully, and the postoperative period was uneventful. The authors recommend that propofol and N2O are suitable general anesthetics for ICD implantation in KSS patients.

Attenuated adult biphasic shocks compared with weight-based monophasic shocks in a swine model of prolonged pediatric ventricular fibrillation

AIM

To compare the safety and efficacy of attenuated adult biphasic shocks with standard monophasic weight-based shocks in a piglet model of prolonged prehospital ventricular fibrillation (VF).

BACKGROUND

If attenuated adult shocks are safe and effective for prehospital pediatric VF, automated external defibrillators (AEDs) can be easily adapted for pediatric use.

METHODS

After 7 min of untreated VF, piglets were randomized to treatment with attenuated adult biphasic shocks or weight-based monophasic shocks. The attenuated adult biphasic group received 200/300/360 J shocks, attenuated by specialized pediatric electrodes to 51/78/81 J and the monophasic weight-based control group received 2/4/4 J/kg shocks. Forty-eight female piglets were studied, 16 in each of three weight categories: 4 kg (neonatal), 14 kg (younger child) and 24 kg (older child). The primary outcome measures of efficacy and safety were 24h survival with good neurological outcome and post-resuscitation left ventricular ejection fraction (LVEF), respectively.

RESULTS

For the 24 kg piglets, attenuated adult biphasic shocks resulted in superior 24 h survival with good neurological outcome (6/8 versus 0/8, P < 0.001) and greater LVEF 4 h post-resuscitation (34 +/- 4% versus 18 +/- 5%, P < 0.05). For the 14 and 4 kg piglets, 24 h survival with good neurological outcome occurred in 7/8 versus 5/8 and 7/8 versus 3/8, respectively, and LVEF 4 h post-resuscitation was 30 +/- 3% versus 36 +/- 6% and 30 +/- 3% versus 22 +/- 4%, respectively.

CONCLUSIONS

The escalating attenuated adult biphasic dosage strategy was at least as safe and effective as the standard weight-based monophasic dose over a wide range of weights in this piglet model of prehospital VF. This work supports the concept of using an attenuated adult biphasic dosage in children.

Implantable cardioverter-defibrillator placement in patients with mild-to- moderate left ventricular dysfunction: hemodynamics and recovery profile with two different anesthetics used during deep sedation

OBJECTIVE

To compare the effects of thiopental and propofol during defibrillation threshold testing (DFT) on hemodynamics and recovery profile in patients requiring automatic internal cardioverter-defibrilator placement.

DESIGN

Prospective clinical investigation.

SETTING

University hospital.

PARTICIPANTS

Thirty-four adult patients.

INTERVENTIONS

After administration of midazolam, 0.025 mg/kg, and fentanyl, 0.5 to 1 mug/kg, surgery was performed under topical infiltration with 1% lidocaine. In group I (GI) (n = 17), patients received thiopental by slow injection and patients in group II (GII) (n = 17) received propofol before induction of ventricular fibrillation (VF).

MEASUREMENTS AND MAIN RESULTS

Patients received 4.1 +/- 1.4 mg of midazolam, 114 +/- 34 mug of fentanyl, and 280 +/- 78 mg of thiopental in GI; and 4.6 +/- 1.7 mg of midazolam, 119 +/- 62 mug of fentanyl, and 147 +/- 40 mg of propofol in GII (p > 0.05). Hemodynamics did not show significant differences between the groups at any recording time. Average time needed to regain the pretest sedation level was 16.4 +/- 8.8 minutes in GI and 10.9 +/- 5.5 minutes in GII (p = 0.03). Time required to achieve a score of 10 using a modified Aldrete score was 26.4 +/- 9.3 minutes in GI and 17.4 +/- 4.9 in GII (p = 0.001). Seven patients in GII (41%) and 1 patient in GI (6%) became hypotensive after DFT (p = 0.04).

CONCLUSIONS

Deepening the sedation level by slow injection of thiopental or propofol before DFT provided satisfactory conditions during brief episodes of VF. Delay in recovery of arterial pressure after DFT with propofol and delay in arousal and discharge of patients with thiopental are major disadvantages of the regimens.