A BIS monitor is a gadget that is used in observing a patients anesthesia depth during postoperative and surgical procedures. The BIS monitors estimate and note the patients consciousness level during sedation by studying their EEG or electroencephalogram Monitoring sedation can be hard due to the effects of sedative medications that differ between patients and because most of the sedative drugs have interactive effects. BIS monitors now start being useful from this stage.

The responsible care givers through the BIS monitors can now effectively be able to analyses and regulate the anesthesia depth of the patient. They can customize the precise sedative and dose anesthetic medicine and sedative so as to decrease the patient awareness and recalling of the tragic experience at the operation room. In enabling today’s anesthetic doses prediction on patients BIS monitors plays a leading role mainly on cerebral cortical responses case. BIS monitors today are extensively used in ICU, (O.R) operating rooms, and other clinical environs. In addition, during the process of outpatient surgery the BIS have also proved to be handy. It is with this overview that his paper will discuss how a BIS monitor works, its advantages and disadvantages and lastly give a conclusion on the findings.

How it works

The monitoring gadget has an inbuilt sensor, monitor, and interface cables for the patient, and signal converters for the digital data. The machinery is also assessable as a unit that can be interfaced with other monitoring systems from other manufacturers.

There is a self-bonding agent incorporated within the inbuilt sensors that are non-intrusive, much like in a general EEG pad. After alcohol has been used to wipe the patient’s temple and forehead to dry the skin, it will in a way of guarantee a superior quality signal is achieved. The machines are either placed on the patient’s forehead, or temples. It then sends the collected information to the BIS engine for possible conversion. The engine will then process the information according to an algorithm that links specific EGG features to create the BIS index. This index is a number displayed on the monitor that is between 0 -100 and mirrors the sedation level of the patients with no brain activity have a 0 rate on the BIS.

If the patient has an average reading of 40 to 60 in the machine it means that they well sedated and therefore have a less chance of awareness and possible intraoperative awakening. In addition other relevant information also displayed in the monitor. The BIS, for example, is a vivid depiction of the BIS index rate over time. It can aid in analyzing changes in the consciousness levels of a patient in reaction to, for example, stimulation during procedure or administration of the drug.

Other additional data shown include: the subdual ratio number (SR) and the signal quality index bar (SQI). The SQI bar measures the signal reliability; the monitor also shows an (EMG) electromyography bar graph, and a single-channel EEG waveform which is likely being used by the SQI to determine if the BIS indexes being displayed are dependable.

Operating Room Advantages of BSI

Some of the advantages of using a BIS monitor are that it lessens the anesthetics intake agents. The dose requirements for anesthetics vary widely between patients. The right concentration or dose for a patient in one condition may demonstrate to be extreme for the same patient in another state. Most Certified Registered Nurse Anesthetist and Anesthesiologists (CRNA) are taught to govern administer anesthetic medication based on patients movements, hemodynamic status and weight. Analysis has revealed that the usage of BIS to lead administration of anesthetics allows drug delivery optimization to the needs of individual patients. In the aspect, avoid the possibility of under dosage or overdose of anesthetic agents

A study confirmed that the incorporation of propofol rates in patients undergoing surgery is lessened through the application. They performed a randomized prospective study that included forty patients undertaking (CABG) elective coronary artery bypass grafting. In the study, there were 20 patients in the BIS group (propofol titrated to maintain a BIS value 40-50), and the regular practice group had 20 patients (received propofol at a target of 3 mcg/ml). The study showed that there was a 30% propofol reduction in the BIS group.

Another advantage of using the BIS monitor during surgery is it lessens the awareness incidences from happening during surgery. The type of surgery procedure mostly dictates how the intraoperative awareness incident will be. In a trauma study, patients have reported the highest intraoperative incidences awareness between 11- 43% while cardiac surgery patients reported rates of 1.14% (Health Quality, 2004).

The BIS monitor usage lessens early recovery time, total drug cost and length of stay. The Cochrane Database of Systematic, evaluation showed that the BIS usage resulted in lesser recovery period. The total number of the members used in the research was 2446. The participants awakening or eye opening period lessened by 2.14 minutes. While the extubation time for 777 of the participants, decreased by 2.87 minutes. Additionally in 316 participants the orientation time was reduced by 2.57 minutes. In 1949 participants stay duration in the PACU was cut by 7.63 minutes. By comparison the CS group and the BIS group total drug costs lessened (Punjasawadwong, 2010).

Disadvantages of BIS monitor

Even though, studies have shown that the BIS monitoring systems in different situations are reliable and can be used with different patients. BIS monitoring; however has some disadvantages that affect its safety and efficiency. Some of these disadvantages are as follows: It has been shown that the BIS monitor can be vulnerable to produce medical devices artifacts such as blanket warmer, electrocautery, train-of-four twitch simulator, pacemakers and high frequency oscillator produce.

The high generated BIS monitor false high readings can be attributed to the medical devices produced artifacts. Analysis done on a 54 year old patient experiencing open-heart surgery showed that once, an incursion is made by the surgeon, the author notes an increase in the BIS index mainly from 56 – 80.false increased BIS scores, similarly have been reported during forced air warming’s therapy of the head (Hemmering and Fortier, 2002).

BIS ratio can be affected by the anesthetic agents. BIS scores have been shown by studies to depend on the kind of anesthetic agent. Inhalation of 70% nitrous oxide in health volunteers has been shown by studies to produce no change in BIS scores (Rampil, Kim, Lenhardt, Negishi, Sessler, 1998) In addition; Ketamine is a dissociative anesthetic agent that is commonly used in adults and children. Studies found that a high dose of ketamine is enough to cause unconsciousness it however does not lower BIS scores.

Titrating anesthetic agents based on age shows that the BIS index can be very misleading and challenging in infants less than six months. BIS values despite the reductions in anesthetic dosage remained below the minimum target of 40.These are similar with results from a prospective blinded study of 49 infants and children who were circumcised (Davidson, McCann, Devavaram, Aubtle, Sullivan, Gillis and Lauren). Research done on infants showed that there were lower BIS results immediately before arousal compared with children. Studies have also reported altered sensitivity for inhaled and intravenous anesthetics among elderly patients.

In 1993, an analysis done by Katoh et al. showed that the BIS scores were heavily influenced by age. The report went on to state that in the analyzed more elderly patients there was a lower response probability at the lower BIS index. The value of the older patients if compared to that of much younger patients was shown to have higher response probabilities.

CONCLUSION

This article has mainly centralized on the BIS monitor use in the OR. In addition to the OR, the BIS have also shown potential in conducting other patient sedation while undergoing endoscopic procedures and for guiding the sedation of patients under the ICU. It is safe to conclude from the above analysis that: the BIS monitor is an effective and safe way of monitoring the hypnosis level of patients under anesthesia. The BIS have more morbidity and cheaper modes of monitoring if compared to other commonly used forms of monitoring.

Reference

Davidson, A. J., McCann, M. E., Devavaram, P., Abtle, S. A., Sullivan, L. J., Gillis, J. M., & Laussen, P. C.,(2001). The differences in the bispectral index between infants and children during emergence from anesthesia after circumcision surgery.326-30.

Health Quality, O. (2004). Bispectral index monitor: an evidence-based analysis. Ont Health Technol Assess Ser, 4(9), 1-70.

Hemmering, T. M., & Fortier, J. M. (2002). Falsely increased bispectral index in a series of     patients undergoing cardiac surgery using forced air warming therapy of the head.322-   323.

Katoh, T., Sugaro, Y., Ikeda, T., Kazama, T., Ikeda, K., (1993). Influence of age on     awakening concentration of sevoflrane and isoflurane.348-52.

Punjasawadwong, Y., Phongchiewboon, A., & Bunchungmongokol, N. (2010). Bispectral index for improving anesthetic delivery and postoperative recovery. Cochrane Database of Systematic Reviews.

Rampil, I. J., Kim, J. S., Lenhardt, R. S., Negishi, C., Sessler, D. I. (1998).Bispectral EEG     index during nitrous oxide adminstration.Anesthesiology.671-7.

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