Canadian Cardiovascular Society/Canadian Anesthesiologists' Society/Canadian Heart Rhythm Society joint position statement on the perioperative management of patients with implanted pacemakers, defibrillators, and neurostimulating devices

There are more than 200,000 Canadians living with permanent pacemakers or implantable defibrillators, many of whom will require surgery or invasive procedures each year. They face potential hazards when undergoing surgery; however, with appropriate planning and education of operating room personnel, adverse device-related outcomes should be rare. This joint position statement from the Canadian Cardiovascular Society (CCS) and the Canadian Anesthesiologists' Society (CAS) has been developed as an accessible reference for physicians and surgeons, providing an overview of the key issues for the preoperative, intraoperative, and postoperative care of these patients. The document summarizes the limited published literature in this field, but for most issues, relies heavily on the experience of the cardiologists and anesthesiologists who contributed to this work. This position statement outlines how to obtain information about an individual's type of pacemaker or implantable defibrillator and its programming. It also stresses the importance of determining if a patient is highly pacemaker-dependent and proposes a simple approach for nonelective evaluation of dependency. Although the document provides a comprehensive list of the intraoperative issues facing these patients, there is a focus on electromagnetic interference resulting from electrocautery and practical guidance is given regarding the characteristics of surgery, electrocautery, pacemakers, and defibrillators which are most likely to lead to interference. The document stresses the importance of preoperative consultation and planning to minimize complications. It reviews the relative merits of intraoperative magnet use vs reprogramming of devices and gives examples of situations where one or the other approach is preferable.     

Society position statement

Purpose

There are more than 200,000 Canadians living with permanent pacemakers or implantable defibrillators, many of whom will require surgery or invasive procedures each year. They face potential hazards when undergoing surgery; however, with appropriate planning and education of operating room personnel, adverse device-related outcomes should be rare. This joint position statement from the Canadian Cardiovascular Society (CCS) and the Canadian Anesthesiologists?? Society (CAS) has been developed as an accessible reference for physicians and surgeons, providing an overview of the key issues for the preoperative, intraoperative, and postoperative care of these patients.

Principal findings

The document summarizes the limited published literature in this field, but for most issues, relies heavily on the experience of the cardiologists and anesthesiologists who contributed to this work. This position statement outlines how to obtain information about an individual??s type of pacemaker or implantable defibrillator and its programming. It also stresses the importance of determining if a patient is highly pacemaker-dependent and proposes a simple approach for nonelective evaluation of dependency. Although the document provides a comprehensive list of the intraoperative issues facing these patients, there is a focus on electromagnetic interference resulting from electrocautery and practical guidance is given regarding the characteristics of surgery, electrocautery, pacemakers, and defibrillators which are most likely to lead to interference.

Conclusions

The document stresses the importance of preoperative consultation and planning to minimize complications. It reviews the relative merits of intraoperative magnet use vs reprogramming of devices and gives examples of situations where one or the other approach is preferable.     

Improved Delivery Through Biological Membranes LX: Intradermal Targeting of Acyclovir Using Redox-Based Chemical Drug Delivery Systems

Two types of novel chemical drug delivery systems (CDS's) for acyclovir, A-CDS-1 (based on oxidation, which utilized the 1,4-dihydrotrigonelline moiety) and A-CDS-2 (based on reduction, which utilized the lipoic acid moiety), were designed to create reservoirs of metabolic precursors for the enhanced local delivery of the antiviral agent acyclovir to the skin. They were evaluated in two-compartment diffusion cells using hairless-mouse skin in vitro. This approach could be useful in the treatment of mucocutaneous herpes simplex virus (HSV-1) infection in the epidermal region of the skin. Upon application to the freshly excised hairless-mouse skin, A-CDS-1 was rapidly oxidized to form the quaternary metabolite AQ⁺, which was extensively localized in the skin. AQ⁺ then served as a reservoir for the release of the antiviral agent in the skin. A-CDS-1 delivered almost equivalent amounts of acyclovir not only to the skin but also transdermally. On the other hand, A-CDS-2 specifically localized acyclovir delivery to the skin as opposed to transdermal delivery. Due to their redox properties, both CDS's demonstrated significant depot formation of metabolic precursors, thus enhancing intradermal acyclovir delivery. The CDS's exhibited greater skin membrane partition coefficients than the parent underivatized acyclovir and were able to release the antiviral agent in the skin tissue. The CDS's were susceptible to hydrolysis in biological media, resulting in the release of acyclovir under near physiological conditions. Thus, the CDS's can serve to enhance intradermal targeting and delivery of the antiviral agent acyclovir.     

The role of vascular resistance in BOLD responses to progressive hypercapnia

The ability of the cerebral vasculature to regulate vascular diameter, hence resistance and cerebral blood flow (CBF), in response to metabolic demands (neurovascular coupling), and perfusion pressure changes (autoregulation) may be assessed by measuring the CBF response to carbon dioxide (CO₂). In healthy individuals, the CBF response to a ramp CO₂ stimulus from hypocapnia to hypercapnia is assumed sigmoidal or linear. However, other response patterns commonly occur, especially in individuals with cerebrovascular disease, and these remain unexplained. CBF responses to CO₂ in a vascular region are determined by the combined effects of the innate vascular responses to CO₂ and the local perfusion pressure; the latter ensuing from pressure‐flow interactions within the cerebral vascular network. We modeled this situation as two vascular beds perfused in parallel from a fixed resistance source. Our premise is that all vascular beds have a sigmoidal reduction of resistance in response to a progressive rise in CO₂. Surrogate CBF data to test the model was provided by magnetic resonance imaging of blood oxygen level‐dependent (BOLD) signals. The model successfully generated all the various BOLD‐CO₂ response patterns, providing a physiological explanation of CBF distribution as relative differences in the network of vascular bed resistance responses to CO₂. Hum Brain Mapp 38:5590–5602, 2017. © 2017 Wiley Periodicals, Inc.     

Anesthesia considerations for patients with an implanted deep brain stimulator undergoing surgery: a review and update

Purpose

Deep brain stimulation (DBS) can be an effective treatment option for patients with essential tremor and Parkinson’s disease. This review provides an overview on the functioning of neurostimulators and recent advances in this technology and presents an updated guide on the anesthetic management of patients with an implanted neurostimulator undergoing surgery or medical intervention.

Source

A search was conducted on MEDLINE®, EMBASE?, and Cochrane Database of Systematic Reviews databases to identify studies published in English from 1974 to December 2015. Our search also included relevant and available incident reports from the manufacturers, Health Canada, the United States Food and Drug Administration, and the European Medicines Agency. Thirty of 232 articles identified were found to be relevant to this review.

Principal findings

Deep brain stimulation systems now offer a range of options, including pulse generators with dual-channel capabilities, rechargeable batteries, and current-control modes. Preoperatively, the anesthesiologist should ascertain the indications for DBS therapy, identify the type of device implanted, and consult a DBS specialist for specific precautions and device management. The major perioperative concern is the potential for interactions with the medical device resulting in patient morbidity. Neurostimulators should be turned off intraoperatively to minimize electromagnetic interference, and precautions should be taken when using electrosurgical equipment. Following surgery, the device should be turned on and checked by a DBS specialist.

Conclusion

The anesthesiologist plays an important role to ensure a safe operating environment for patients with an implanted DBS device. Pertinent issues include identifying the type of device, involving a DBS-trained physician, turning off the device intraoperatively, implementing precautions when using electrosurgical equipment, and checking the device postoperatively.