Paul M. Parizel,1 Nick Van de Voorde,1 Robert Slappendel,2 Marcel Vercauteren2
1 Department of Radiology, Antwerp University Hospital and University of Antwerp, Belgium
2 Department of Anesthesiology, Antwerp University Hospital and University of Antwerp, Belgium
As medicine continues to evolve towards minimally invasive procedures (often obviating the need for open surgery), the range and complexity of image-guided interventional procedures in the radiology department has steadily increased in recent years. Radiology has grown from being a mainly diagnostic and non-invasive discipline, towards becoming an increasingly interventional and therapeutic specialty. This evolution has created a growing need for the presence of anaesthesiologists during interventional radiology, especially since radiologists have, in general, limited experience with life support and pain control. The collaboration of these two disciplines, radiology and anaesthesiology, requires flexibility and understanding on both parts.
Anaesthesiologists have to face the challenges of working outside the operating theatre, in an alien environment, involving complex machinery, ionizing radiation, unfamiliar procedures, and cramped spaces. Sedation and analgesia outside the operation theatre is risky, although a change is visible. A survey by Quine et al. published in1995 showed a mortality rate of 1 out of 2,000 patients. More recently, larger patient series published by Sharma (2007) and Vargo (2006) both showed mortality rates of 1 out of 10,000 patients. The difference between the mortality rates can be attributed to better monitoring of patients and administration of drugs by trained persons. Radiologists have to accept that the anaesthesiologist takes charge of patient life support, and deals with vital parameters, co-morbidity, pain management, and medication administration.
This forced cohabitation can potentially lead to conflicts of interest, since both radiology and anaesthesiology are complex, technology-driven departments, with high patient turnover, and occupy pivotal positions in the hospital workflow. Radiology and anaesthesiology provide assistance to the entire hospital community, around the clock, on a 24/7 basis; both share a concern for efficient patient workflow, and they are often faced with a demand for service that exceeds capacity. Needless to say, this situation poses a unique set of challenges for both disciplines.
When performing non-operating room anaesthesia (NORA), anaesthesiologists are forced to venture out of their professional comfort zone. In the (neuro)vascular interventional radiology suite, anaesthesiologists have to perform their craft in a challenging and unfamiliar environment, with imperfect (and sometimes inadequate) monitoring devices, facing a wide range of procedures, performed with a complex technical platform involving one (“monoplane”) or two (“biplane”) X-ray tubes attached to a ceiling mounted C-arm or a multipurpose interventional robot. In this challenging environment, they have to work with doctors, nurses, and technologists with whom they are less well acquainted. Moreover, anaesthesiologists have to deal with radiation risks and other potential hazards of providing anaesthetic care outside the operating theatre. The most commonly performed transarterial catheterization procedures involve the treatment of (critically ill) patients with acute stroke, subarachnoid haemorrhage (due to rupture of a cerebral aneurysm) or vascular malformations. Not infrequently, these treatments are performed on an emergency basis. During interventional radiology procedures, the anaesthesiologist guarantees not only immobility of the patient, but is also in charge of managing unexpected complications, optimizing cerebral blood flow, monitoring blood pressure and fluid balance, and maintaining intracranial pressure. In order to overcome these challenges, rigorous standards of procedure should be applied (Youn et al.). The necessary facilities (e.g., intraprocedural monitoring devices, anaesthesia ventilators) must be available in the interventional radiology suite. The equipment should suitable for the environment, and must be connected to the hospital information system, so that it is possible to export the clinical data needed for complete and accurate patient anaesthesia records. After the procedure, the anaesthesiologist accompanies the patient during transport from the procedure room to the recovery room or intensive care unit, and facilitates rapid awakening while minimizing adverse effects (Youn et al.).
Anaesthesiologists also play a role in the computed tomography (CT) suite. A typical example of CT-guided interventional procedures is percutaneous radiofrequency ablation (RFA). Percutaneous RFA is a minimally invasive procedure in which a special radiofrequency needle electrode is inserted into the lesion under CT-guidance. Multiplanar evaluation is used to confirm accurate needle positioning. Once the needle is placed, it is connected to a generator, which delivers a rapidly alternating current (RF energy) to heat the tip of the electrode; the temperature increase causes liquefactive necrosis of the tumour. RFA is used for percutaneous treatment of liver neoplasms (e.g., inoperable hepatocellular carcinoma or liver metastases). RFA is also applied for the ablation of some bone tumours, such as osteoid osteoma. To ensure patient comfort, general anaesthesia is the option of choice during RFA; this is not only to achieve optimal pain relief and tolerance, but also because RFA sometimes requires uncomfortable positioning of the patient. During the procedure, the anaesthesiologist and nursing staff can intermittently be subjected to radiation and need to wear proper protective lead aprons and thyroid shields.
Magnetic Resonance Imaging (MRI) poses a different kind of challenge. Anaesthesiologists often need to guide a patient safely through a narrow tunnel, in which a strong, magnetic field is applied. The MRI suite, in the presence of a strong magnetic field and within the confines of a Faraday cage, limits the possibilities of technical support. Other challenges include a high noise level (due to rapid gradient switching), a darkened room, limited space, and, last but not least, the inherent danger of unintended projectiles. Ferromagnetic objects are attracted by the magnet, may fly inside the scanner and can cause serious injuries and even death of the patient. The magnets of MRI scanners are never switched off, and pose a continuous danger. Most accidents are caused by human error. Many radiology services now require that all anaesthesiology personnel should first successfully pass an MRI safety briefing, in order to understand the potentially lethal accidents that can be caused by scissors, surgical clamps, gas containers, stethoscopes, and other flying objects. In the MRI suite, the anaesthesia machine should be MRI compatible, meaning that it has been approved for use with MRI systems of 1.5 and 3 Tesla and can be safely operated at gradient field strengths of 40 mTesla (400 gauss).
In summary, the availability of state-of-the-art anaesthesia services is a conditio sine qua non for performing complex interventional radiology procedures. Hospital administrators and financial planners should be informed that this approach requires considerable investments in infrastructure and manpower, for both radiology and anaesthesiology, in order to provide a patient-safe environment for performing image-guided interventional procedures.
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