The demand for high-end anesthesia machines with electronic gas mixing, anesthesia gas module, and depth of anesthesia will see an upward trend with experienced and well-trained anesthesiologists being recruited even in Tier-II and Tier-III cities.

The last decade has witnessed a paradigm shift in the demand for anesthesia workstations. Having a good, reliable anesthesia workstation with temperature-compensated anesthesia vaporizers and in-built ventilation has now become the new norm. The market is witnessing increased number of customers upgrading from existing Boyles-type basic anesthesia machines to quality anesthesia workstations packed with safety features. The demand is rapidly increasing with growing safety awareness and technology enhancements in anesthesia machines.

Low-flow anesthesia and electronic medical records dominate the current anesthesia market technology, which indirectly leads to lesser significant savings across the healthcare industry. However, rapid advancements in the anesthesia industry make it increasingly difficult for the anesthesiologist to keep up with anesthesia machine technology. Also, the latest anesthesia technology does not come low priced; even the most basic configuration of the equipment can cost a fortune. Decrease in reimbursements provided by governments for medical equipment, and increased availability of after-market service that prolongs the life of a facility's existing equipment are also the challenges involved.

Technology Trends

The modern integrated anesthesia workstation is designed to be a complete anesthesia, respiratory gas delivery, and monitoring system. The new machines use advanced electronics, software, and technology to offer extensive capabilities for ventilation, monitoring, inhaled agent delivery, low-flow anesthesia, and closed-loop anesthesia. They offer integrated monitoring and recording facilities and seamless integration with anesthesia information systems. It is possible to deliver tidal volumes accurately and eliminate several hazards associated with the low pressure system and oxygen flush.

Low-flow anesthesia (LFA). LFA with closed breathing system is becoming popular because of its various advantages. It benefits the users by reducing anesthesia gas consumption by up to 70 percent and reducing the concentration of anesthesia gas and nitrous oxide in the operating room.

Digital gas flow meters. The mechanical float-type flow meters used for anesthesia gas mixtures are now being replaced by digital flow meters, which can directly project the gas flow rates on the digital display or on the ventilator screen. The flow values are more accurate than the analog float meters as the flow sensors are temperature- and media-compensated with individual calibration constants stored in each sensor.

Modern circular breathing systems. The integrated circular breathing system minimizes the number of connections and dead space volume, which makes delivery more accurate and reduces leakage to the minimum. The reusable soda lime canisters are getting replaced by disposable cartridge soda lime canisters.

Electronic ventilator. The mechanical ventilators used for anesthesia ventilation are now being replaced by advanced software-controlled electronically driven ventilators, which are compact, smarter, and user friendly. The use of electronic sensors in close-loop improves the accuracy of flow, pressure, and ventilation.

Enhanced ventilation modes. Modern anesthesia machines provide high performances in delivering accurately and precisely the desired volumes and pressures, including assisted-ventilation modes. The end-inspiratory and end-expiratory pauses as well as flow-volume loop curves are additional assisted modes that need to be incorporated in anesthesia machines to optimize ventilation monitoring.

Monitors and peripherals. The modern anesthesia delivery systems are integrated with various monitoring equipment like end-tidal carbon-dioxide (etCO2) monitor, anesthesia gas concentration monitor, and patient monitor to have control on anesthesia delivery and to monitor the patient condition during the procedure. Peripherals like syringe pumps, suction devices, and scavenging units are also a part of the modern anesthesia workstation to make it a complete solution for anesthesia delivery.

Depth of anesthesia. The most important potential clinical benefit of using depth of anesthesia (DoA) monitoring during procedural sedation and analgesia (PSA) is that this technology reduces the risk of the most common antecedent event hypoxia from inadequate oxygenation or ventilation for sedation-related death and permanent neurological deficits. These advantages would be a strong indicator that DoA monitors are likely to improve patient safety during PSA.

Interoperability. Stand-alone anesthesia machines and anesthesia workstations offer different benefits to customers depending on their requirements. Vendors offering stand-alone machines are allowing clients to be independent and flexible in their purchasing, with hospitals not committing to any one brand of patient monitor. This can be beneficial to customers that are conservative with regard to changing the brand of equipment they use. Nonetheless, for this strategy to be successful, the anesthesia machine must be fully interoperable with patient monitors from different vendors, allowing the purchaser to essentially build their own anesthesia workstation with equipment from two different brands. Customers favoring more traditional anesthesia workstations can benefit from the servicing of machines being provided by the same manufacturer, in addition to the value gained from efficient workflows and ease of use.

Anesthesia information management systems (AIMS). AIMS began as simple automated intraoperative record keepers, the core function of which remains the generation of an automated, continuous electronic anesthesia record that captures and documents the patient's physiologic data (e.g., vital signs) and allows for the manual notation of intraoperative events (e.g., drug administration). Since then, AIMS have evolved into sophisticated hardware and software systems that are currently available as either stand-alone products or as part of a hospital's electronic health record (EHR) system - both types offer features to expand their capabilities beyond intraoperative record keeping to enhance other aspects of the perioperative experience. CDSS has become increasingly integrated into AIMS, and can be grouped into three categories, such as process of care, which involves improving adherence to clinical protocols and guidelines and perioperative antibiotic administration; practice management such as billing, maximizing operating room efficiency, and throughput; and outcome-based decision support like facilitating care that leads to better patient outcomes. CDSS is currently an active area of anesthesia research and development, largely due to its potential to improve patient care and outcomes.

The latest technology makes the workstation advanced and user friendly. Precise delivery of anesthesia is possible with the help of these latest technologies. The safety of patient, user, and environment is also addressed in this technological evolution.

Road Ahead

The market is moving from a conventional anesthesia delivery system to entry-level anesthesia workstations. The demand for anesthesia workstations will continue to be supported by the drive for integration of medical equipment across the healthcare continuum. Nonetheless, vendors that can offer both stand-alone and workstation configurations are likely to be the most effective, allowing customers to choose the best option suited to their needs. Manufacturers need to be flexible in their strategy surrounding selling patient monitors with anesthesia machines to be able to continue to compete in the dynamic anesthesia market.

In the next 5 years down the line, all basic pneumatic devices will be replaced. Availability of advanced and cost-effective technology will drive the anesthesia market. With increased knowledge-sharing in recognized forums and decrease in price points, the need for low flow and minimal flow anesthesia even in the entry-level anesthesia machine segment is on the rise. The demand for high-end anesthesia machines with electronic gas mixing, anesthesia gas module, and DoA will see an upward trend with experienced and well-trained anesthesiologists being recruited even in Tier-II and Tier-III cities.

Dr Dipankar Dasgupta,  Director-Department Of Anesthesia, Jaslok Hospital and Research Centre, Mumbai Dr Bhushan Vadnere,  DNB Resident-Department of Anesthesia, Jaslok Hospital and Research Centre, Mumbai
Second Opinion
Measuring Depth of Anesthesia

Anesthetic depth ranges from a 100 percent probability of an easily suppressed response to a mild stimulus and readily suppressed responses to a 100 percent probability of nonresponse to profoundly noxious stimuli and responses that are difficult to suppress. Plomley (1847) first defined depth of anesthesia in three stages - intoxication, excitement, and deeper levels of narcosis. In the same year, John Snow described five degrees of narcotism for ether anesthesia. In 1937, Guedel published clinical signs of four stages of ether anesthesia involving somatic muscle tone, respiratory patterns, and ocular signs. In 1957, Woodbridge defined anesthesia with four components - sensory blockade, motor blockade, blockade of autonomic reflexes, and loss of consciousness. According to him, general anesthesia is suppression of conscious perception of noxious stimuli.

Objective of monitoring depth of anesthesia is to prevent awareness during surgery without inadvertently overloading the patient with potent drugs, especially in susceptible cases like those with multiple trauma, caesarean section, cardiac surgery, and hemodynamically unstable patients.

Anesthesia depth-monitoring involves subjective methods, objective methods, and derived indices including bispectral index (BIS), patient safety index (PSI), entropy, and evoked potentials like auditory, visual, and somatosensory-evoked potentials, and auditory-evoked potential index.

Clinical Usage

Bispectral index. It is an empirically derived scale proposed by Aspect Medical System (1987) to monitor level of consciousness among patients receiving general anesthesia and sedation. The algorithm processes the EEG in near-real time and computes an index value between 0 and 100 that indicates the patient's level of consciousness. A value of 100 corresponds to being completely awake, whereas 0 corresponds to a profound state of coma or unconsciousness that is reflected by an isoelectric or flat EEG.

Patient safety index. It is like BIS, a proprietary algorithm that assesses level of consciousness based on the EEG for patients receiving general anesthesia or sedation. The PSI was approved by the FDA in 2000 and was originally produced by Physiometrix (North Billerica, MA), but it is now manufactured and sold by Masimo (Irvine, CA). Development of the PSI was the outgrowth of several years of research conducted by E. Roy John at the Brain Research Laboratory at the New York University School of Medicine. Like the BIS, PSI is also scaled between 0 and 100. However, the PSI range to ensure that the patient is unconscious is between 25 and 50.

Entropy. The use of entropy to track the level of consciousness in patients receiving general anesthesia or sedation is relatively new. Entropy monitor was developed by Datex-Ohmeda, GE Healthcare (Little Chalfont, UK). Entropy is a well-known concept in the physical sciences, mathematics, and information theory. It measures the degree of disorder or the lack of synchrony or consistency in a system. The algorithm uses frequency-domain analysis, combined with burst suppression to measure the entropy of the EEG in patients receiving anesthetic drugs.

Evoked potentials. Evoked potentials (EPs) show the response of more localized areas of the brainstem, mid-brain, and cerebral cortex to motor and sensory stimuli. EPs represent a time-versus-voltage relationship that can be quantitated by measuring the post-stimulus latency and interpret amplitudes in the waveform.

Future Ahead

At present, it is unlikely that any single method is found to measure the depth of anesthesia reliably for all anesthetic agents. The only reliable way of determining depth of anesthesia will require a measure of cerebral activity and a localization of the activity to specific cortical regions and areas in brain stem, in real time.

Dr Dipankar Dasgupta
Director-Department Of Anesthesia,
Jaslok Hospital and Research Centre, Mumbai

Dr Bhushan Vadnere
DNB Resident-Department of Anesthesia,
Jaslok Hospital and Research Centre, Mumbai


 

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