A randomized and controlled study comparing efficacy of intra-operative patient controlled sedation versus radiologist controlled sedation using midazolam and fentanyl, for patients undergoing insertion of a central venous line.

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Diagnostic and therapeutic procedures performed in interventional radiology can provoke anxiety and may be painful. Mild sedation with analgesia is administered by the interventional radiologist to calm patient anxiety, reduce unwanted movements and alleviate patient discomfort. Central line placements are common, (including Hickman line placement, tunnelled dialysis catheter placement, injectable port implantation) and intravenous sedation would typically be used for these procedures. The most commonly used drug for sedation in radiology is midazolam, a benzodiazepine. Midazolam has a short half-life of 2-6 hrs, but very powerful anxiolytic (anti-anxiety), amnestic, hypnotic, anticonvulsant, skeletal muscle relaxant, and sedative actions. It is administered at 1 milligram per dose to the desired response, has a 2 minute onset time and duration of 45 to 60 minutes. The most common analgesic used is fentanyl, a short acting opioid that is administered at an incremental dose of 25 micrograms and repeated every 5 minutes to a maximum dose of 100 micrograms. Its onset time is 2-3 minutes and it has a duration time of 30-60 minutes. Midazolam and fentanyl are usually administered concurrently, with 1 milligram midazolam and 25 micrograms fentanyl being the standard single dose. Multiple doses are titrated carefully to achieve and maintain adequate sedation and alleviation of anxiety, while preserving cardio-respiratory function, protective reflexes and the ability to respond appropriately to verbal and/or tactile stimulation. Doses are given incrementally, often starting with a double dose with at least 5 minutes interval before the next dose to allow evaluation of drug effect. Oxygen saturation, blood pressure, heart rate, and respiratory rate are monitored continuously and documented every 10 minutes. Neurological response is also monitored continuously by observing the patients response to command or conversation. Reversal "antidote" agents for these medications are flumazenil and naloxone respectively. The current practice is that the radiologist takes a history from the patient, looking for patient factors that may affect the safety and practice of sedation. These would include patient size, age, prior cardiac and respiratory disease, diabetes, renal failure, obesity, allergies, drug interactions, previous anaesthetic history, and airway issues. There will be assessment of the patient’s level of anxiety and expectation of procedural discomfort. The radiologist will then decide on the appropriateness of midazolam/fentanyl sedation, and choose an initial dose. As the procedure starts, the level of sedation is assessed, and if needed, further aliquots of midazolam/fentanyl are administered at the radiologists’ discretion. Our hypothesis is that this practice has problems in that there is a fear of the effects of oversedation (eg low blood pressure or slower respiratory rate), and this results in many patients being undersedated. The patient may be apprehensive to ask for more sedation and thus their overall experience of the procedure is suboptimal. Based on prior evidence in the literature in other medical settings, we believe that by giving the control of sedation to the patient (within a safe dose and lockout period), that the patient is more likely to seek sedation when required and hence will be at less risk of undersedation. We expect that this will lead to an overall greater experience for the patient. The medical procedure being performed (ie insertion of a tunnelled central line) will not be affected by this study.

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