Anaesthesia in the MR Environment-Minimum Requirements - Report Example

Anaesthesia in the MR environment-Minimum requirements Introduction Magnetic resonance imaging is a routine procedure nowadays. Patient’s safety is always a primary aim in any MRI set up. MRI staff is well trained to carry out precautionary measures in order to avoid accidents and offer the best care to the patients. In some MRI instances, administration of anaesthesia becomes a necessity. Those conditions are further described below. Patients acquiring anaesthesia are at times very hard to manage and demand experts’ attention. This document has highlighted the minimum requirements of anaesthesia in MRI unit such as a well-equipped anaesthesia room, MRI compatible anaesthesia equipments, and availability of experts for the complete health and safety of the patient under anaesthesia. Background The need of anaesthesia during MRI was understood long back, but there were no clear guidelines available as how to set up anaesthesia techniques in MRI chamber till 1993 (Farling, 2003, p. 421). Technicians have started utilising anaesthesia drugs in MRI setup; however, the anaesthesia techniques generally used in here were found outdated and so failed to cope up with the advance national standards. The leading anaesthetist Wetzel revealed the same fact that “unfortunately, anaesthesia in MRI does not uniformly adhere to the basic national standards” (2007, p. 1602). In this time, Wetzel (2007, p. 1602) and others highlighted shortcomings of practice such as use of gravity-micro drips when they should have been superseded by controlled infusion pumps. Safe anaesthesia administration before and during MRI procedure has always been a big challenge in front of all the experts (Fogal et al., 2008; Pendel & Twigg, 2003). In 2009, The American Society of Anaesthesiologists had established the practice ‘Advisory on Anaesthetic Care for Magnetic Resonance Imaging’ (ASA) describing minimum requirements for anaesthetic care for MRI. Advisory mentioned that anaesthesia needed during MRI could be in the form of simple anaesthesia or long standing general anaesthesia. It is also needed when the patient is critical and requires life system support. ASA had following goals (2009, p. 459): 1. To assure maximum protective environment to patient and MRI staff. 2. To minimise the incidences of mishaps during MRI activities. 3. To plan for better patient management. 4. To focus on all equipments that can be hazardous. 5. To determine the constraints of the staff posted for continuous monitoring in the MRI section. Need for anaesthesia Some patients cannot lie down steadily in the MRI bore due to various reasons such as claustrophobia, disability and critical illnesses. In addition, it is always difficult to have MRI imaging in paediatric group due to their hyperactivity. Patient needs to be really very steady and calm during MRI procedure. Hence, experts realised the need of anaesthesia administration in all such cases. Following are the same conditions when anaesthesia is a definite requirement: 1- MRI- long duration- Although MRI techniques’ have improved and scanning time reduced, there are exceptions of more complex scans or some repetitive scans which require approximately 25 minutes to almost 1 hour to complete the entire examination. In all such cases, patient needs sedation (Fogal et al., 2008). Figure 2: Larger MRI scanners tend to feature less claustrophobic reactions from patients (Physical Therapy, 2012) 2- Children and/or infants –Children cannot lie down quietly. And this is the basic need of the MRI procedure. Hence, in almost all the paediatric cases, especially with neurological investigations, anaesthesia is must (Pendel & Twigg, 2003). 3- Unstable adults- Certain groups of adults do need anaesthesia throughout MRI in some cases such as repeated scans, claustrophobia, inability to remain steady, having learning difficulties or disabilities (Farling, 2002, p. 421). 4- Noisy process- MRI is very noisy process. Gradient coils make lot of acoustic sounds. Sometimes the noise is unbearable. Ear protectors are must to all the staff and patient too, no matter whether patient is sedated or not (Fogal et al., 2008; Pendel & Twigg, 2003; Association of Anaesthetics of Great Britain and Ireland, 2002). Administering anaesthesia- dosage very important General anaesthesia better for sedating children: It is advisable to sedate the sick child to achieve maximum immobility in order to have better imaging. Sedating children requires good skills and adequate knowledge of dosage and its side effects too. It is always advisable that expert anaesthetist only do the needful. As per Fogal, multidisciplinary sedation teams have shown an excellent success rate along with an incredible safety record with the use of sedation throughout the MRI process (2008). However, it has been seen that administering general anaesthesia is always a challenge to the non-specialised unit and offering correct sedation dose is equally very important to avoid massive side effects. Example given by Fogal as inappropriate sedation in increased intra cranial pressure cases can be very dangerous (Fogal et al., 2008; Pendel & Twigg, 2003). A deeper level of anaesthesia required due to noise: The level of noise generated by the MRI throughout an examination is at times around 85 dB due to the gradient magnetic fields. Noise is described as loud thumping or loud tapping sound. This can be daunting and very disconcerting for an awaken patient. This may necessitate the use of deep anaesthesia (Pendel & Twigg, 2003). MRI compatible anaesthetic machines Using anaesthetic equipments in MRI unit is major challenge mainly due to their intense magnetic field along with the associated radio frequency currents in use throughout the imaging, which requires the need for MR compatible equipment (Pendel & Twigg, 2003). American Institute of Anaesthesiologists (2002) suggests in its newsletter that MRI room is considered as second anaesthesia set up as all the instruments should be compatible to the ongoing MRI process. It is suggested that there should be a primary anaesthesia set up, associated close to the MRI room with all the advanced facilities. In case of emergency, patient can be transferred there in no time. All the machines are MRI compatible including ventilators and all (The Association of Anaesthetics of Great Britain and Ireland, 2002). These new MRI compatible anaesthetic machines and ventilators can safely be situated adjacent to the magnetic bore. These machines use piped medical gases with all reserve cylinders being made of a non-ferromagnetic material. E.g., co-axial Mapleson D circuit with a suitable length is in common use for adults; while Ayre’s T-piece will be used for children. Figure 1: MRI-Compatible Anaesthesia Machine (Macron technologies, 2012) Health and safety of the patients and staff It is the size and complexity of the MRI systems that draw anaesthetists away from the areas of the clinical setting in which they are comfortable performing duties and into a new setting with new contingencies” (Oldman & Nicholls, 2004). Need for an anaesthetist has already been established in MRI set up as the safety of the patients has tremendous importance. All the staff members, patient, and relatives are thoroughly screened before entering the MRI room (The Association of Anaesthetics of Great Britain and Ireland, 2002). Ferromagnetic objects The instruments used inside and outside the MRI should clearly be labelled as MRI safe. Instruments inside the anaesthesia room need not be MRI friendly. Hence, it is utmost important to record and check each instrument before taking it to MRI room. This can cause dangerous situations such as projectile effect and burns. This may also lead to malfunctioning of the instrument (Farling, 2003, p. 421; The Association of Anaesthetics of Great Britain and Ireland, 2002). Magnetic property of iron, nickel and cobalt makes them unsafe in MRI set up whereas certain metals are safe and do not interfere with the MRI radiofrequency with no risks of projectile issues. Those metals are aluminium, titanium, copper, silver and gold (Litt& Cauldwell, 2002). Some of the potential risks associated with the use of MR and the associated magnetic field are ferromagnetic objects, and surgical objects becoming lethal projectiles, and the effect the magnetic field may have on patients with pacemakers. This requires that there is a need for systems in place protecting and safeguarding the patients well being, safety and health but also that of the attending staff (Pendel & Twigg, 2003). It is clear so far that not all the equipments used for administering anaesthesia are MRI compatible. Hence, anaesthetist performs certain procedures on patient before sending in for imaging. Those procedures are: (a) Examination of air passage- As mentioned above, every instrument used by anaesthetists is not MRI safe including laryngoscope (due to their ferromagnetic batteries). Hence, anaesthetist makes sure that patient’s airway is clear and no obstacle exists while breathing before the commencement of the MRI procedure. The anaesthetist must also be familiar with all set procedures with the rapid removal of a patient to a safe area, in case of an emergency (American Society of Anaesthesiologists, 2009). (b) Monitoring prior to MRI- Monitoring patient and equipments before sending in MRI room is an important task of for all the respective staff. Care should be taken in terms of checking all the equipments for MR compatibility before sending them in and maintenance of all the instruments needed for patient monitoring .Recent guidelines by the Association of Anaesthetists suggest that all monitoring systems should be placed within the control room with all the essential cables and hoses and waveguide radio-frequency screening ports into the MRI room (Pendel & Twigg, 2003). (c) Ear protection-There is a need for ear protection by all patients regardless of if the patient is awake or under anaesthesia as the noise levels of a MRI can and often exceed 85 dB (Pendel & Twigg, 2003). (d) Other precautionary measures- Removal of all potentially hazardous equipment and articles such as bleeps, watches, stethoscopes, and so forth. Unnecessary repeated exposure can have ill effects; hence, all staff should exit the MRI room during scanning. Need for adequate gas scavenging system Anaesthetic room and MR room should have pipe gas and suction tubes installed to have proper gas exchanging. All the anaesthetic gasses should be scavenged adequately to avoid exposure to any of the staff that may be required to stay within the MRI room through the scanning procedure (Pendel & Twigg, 2003). Magnetic field is permanent An anaesthetist must consider that the magnetic field as a ongoing process, and must not assume that in case of any emergency it can be turned off. Physics of a MR is complicated and all the staff should have fair knowledge about it in order to tackle emergencies. (Pendel & Twigg, 2003). The administration of the anaesthesia- Routine methods Anaesthesia room MR unit has a control room or the anaesthesia room that is usually located adjacent to MRI room containing five gauss magnetic field contour. This location is advisable for maximum convenience .This, in turn, provides staff the place where an anesthetised patient is quickly transferred into the scanner or removed if there is an emergency. Patient can also rest there during recovery phase. Transport of all the patients is done on a non-ferrous MRI compatible trolley to the magnet area of the MRI (Pendel & Twigg, 2003). Role of anaesthetist The anaesthetist is a well-trained person. His teal includes nurse and technical people. In order to tackle any unwanted situation, anaesthetist will always be present within the control room to monitor the patient throughout, though in certain conditions, they may have to be there in the MRI room. All the staffs are well informed and trained about the risk involved during the procedure and measures to handle the situation. The dose of anaesthesia is manipulated through intravenous route or by inhalation while patient is under scanning following all the safety measures (Pendel & Twigg, 2003). Figure 3: The following scene shows the need for specialists in attendance when anaesthesia is required for MRI even in the case of animals (Purdue University, 2010). Care for intravenous anaesthesia Intravenous anaesthesia is the most accepted and suitable method of sedation throughout radiological procedures. However, infusion pumps are strongly ferromagnetic and liable to malfunctioning in the presence of magnetic field and it can be harmful in terms of being projectile when placed near or in the magnetic field. Hence, the infusion pump are located in the control room and connected to the patient with the use of a long-line that goes through the Faraday Cage by passing through the waveguide. The volatile agents can be given using vaporizer that has been fixed to the suitable anaesthetic machine that is either in the control room or in the actual scanning room (Pendel & Twigg, 2003). Conclusion MRI compatible anaesthesia equipments should have been available to all the MRI set-ups in order to have maximum patient safety. All these equipments should be checked thoroughly for MR compatibility. These equipments no matter what is the cost should match the standards set by national anaesthesia department offering provision to have all sorts of anaesthesia dosage along with thorough monitoring of the patient in the safest environment around. In addition, the anaesthetist should examine every patient acquiring MRI procedure prior to the test. MRI technicians and other staff should take care of the arrangement of MRI room, emergency instruments, central gas supply and power connections in order to have minimum accidents and maximum patient safety. References American Society of Anaesthesiologists. (2009). Practice Advisory on Anaesthetic Care for Magnetic Resonance Imaging. Anaesthesiology. 100, pp. 459 – 79. Farling, P. (2002). Anaesthesia in the Magnetic Resonance Unit: A hazardous environment. Anaesthesia. Vol.57, pp.421 – 423. Fogal, M., Weinberg, P., Parave, E., Harris, C., Montenegro, L., Harris, M. & Concepcion, M. (2008). Deep Sedation for MRI: a Comparison with Cardiac Anaesthesia. The Journal of Paediatrics. pp. 534 – 539. Litt, L. & Cauldwell, C. (2002). Being extra safe when providing anaesthesia for MRI examinations. American Society of Anaesthesiologists. Vol 66. [Online]. Available from http://asatest.asahq.org/Newsletters/2002/6_02/litt.html [Accessed: April 25, 2012] Oldman, M. & Nicholls, B. (2004). 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Comparison between MRI screening and CT-plus-MRI screening for thrombolysis within 3 h of ischemic stroke’, Journal of the Neurological Sciences.Vol. 294, pp.119 – 123. Diagram Macron technologies. (2012). MRI-Compatible Anaesthesia Machine. www.macrontechnologies.com Read More