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Editorial |
1 From the Department of Radiology, Northwestern University, 448 E Ontario St, Suite 700, Chicago, IL 60611. Received and accepted June 7, 2000. Address correspondence to the author.
Index terms: Anesthesia, **.121412 • Editorials • Magnetic resonance (MR), in infants and children, **.12141 • Magnetic resonance (MR), quality assurance, **.12141 • Magnetic resonance (MR), safety, **.12141
In this issue of Radiology, Drs Bluemke and Breiter provide an elegant description of the Johns Hopkins Hospital experience with sedation for magnetic resonance (MR) imaging over an 8-year span (1). The authors accessed a huge database that comprises the records of 4,761 patients who received sedation. They reviewed the medications used, supportive nursing procedures, success rates, and effects on the cost and efficiency of MR imaging with various levels of nursing skill and specialization.
Several interesting points are raised in this article. The high rate of sedation in the current article (up to four cases per day in the latter years) reflects the preponderance of children in the study group. However, whereas previous articles have focused almost exclusively on pediatric patients, about 20% of the subjects in the current study group (approximately 950 patients) were adults and formed by far the largest and most broad-based study of MR imaging sedation of which I am aware.
As in previous articles (2–4), Bluemke and Breiter found that, properly administered, sedation is very safe. They report a rate of adverse reactions of 0.42%, and none of these reactions were serious. Similar safety indexes were reported in children by Shepherd et al (2), Vade et al (3) and Volle et al (4). Bluemke and Breiter also report a high rate of successful examinations, with only 6.5% of sedated patients having nondiagnostic studies. Vade et al (3) reported a success rate approaching 100%; Shepherd et al (2), a rate of about 85%; and Volle et al (4), a rate of 91%. It is not clear why Vade et al had such a low rate of failure due to awakening or motion. Patient selection may have played a role: All their subjects were younger than 4 years old and had physical status I (normal) or II (mild, nonlimiting systemic disease) according to the American Society of Anesthesiologists Physical Status Classification.
Bluemke and Breiter also noted that sedation is more efficiently and effectively administered by nursing staff in the radiology department than by staff from the wards. In the study by Shepherd et al (2), nursing staff on the wards administered the sedation, and it is interesting to speculate that their somewhat lower success rate may in some part be related to this.
The plethora of drug protocols described in the literature speaks to the absence of a standard pharmaceutical regimen for conscious sedation. Various age-specific protocols, including combinations of chloral hydrate, antihistamines, neuroleptics, narcotics, orally and intravenously administered benzodiazepines, and intravenously administered barbiturates have been reported (1–5). The lack of such a standard is reflected in the American Academy of Pediatrics Committee on Drugs guidelines for the treatment of sedated pediatric patients (6), where close monitoring, independent of drug regimen, is stressed.
Safety is the prime consideration in patients of all ages undergoing conscious sedation, and vigilance should be no less intense in the adult population, especially if intravenous sedation is used. While sedated in the magnet, patients should undergo continuous pulsimetry and oximetry and frequent observation of blood pressure and breathing pattern; the utility of the electrocardiogram for monitoring purposes may be severely compromised by magnetic field effects, and little reliance should be placed on it. A dedicated nurse should be present whose sole responsibility is to monitor the patient during sleep through recovery (6–9).
Reports of which I am aware, culminating in the current large series from Bluemke and Breiter, support the view that conscious sedation in MR imaging, with appropriate screening and monitoring of patient conditions, is extremely safe. These results should be generalizable to other sites with similar practice procedures. However, even one unanticipated disaster will be too many, and it is important to stress that each case is unique. Cote (7) notes that the term "conscious sedation" is a euphemism when applied to children sedated for MR imaging. He rightly points out that these children are in pharmacologic coma and must be sufficiently deeply asleep not to be aroused by the noise of powerful gradients. Even minor degrees of blood oxygen desaturation must be addressed immediately. The task in adults is to allay anxiety, and this represents a lighter level of sedation.
An intriguing analysis of the dollar cost of conscious sedation is presented by Drs Bluemke and Breiter (1). The authors note that sleep is induced more quickly and with a narrower SD if dedicated radiology sedation nurses are used. They propose that the length of time the MR imaging machine must be put on hold pending the onset of sedation is about equal to the width of this time window (1 SD from the mean). They describe three categories of nurses who administered sedation over 8 years: Group A comprised radiology nurses dedicated to patient sedation; group B comprised radiology nurses used occasionally for conscious sedation, but this was not their primary focus; and "inpatient floor nurses" (which, for convenience, I will call group C). The time windows (SDs) for the respective groups A, B, and C were 15, 20, and 37 minutes, during which the MR imager was on standby. This time must be purchased on the basis of the rate per minute charged by the hospital ($7 in the current study). Additional costs include nurses’ salaries and benefits ($238 per day) and medication ($30 per patient).
To "break even," all costs must be covered by reimbursement for the sedation procedure (quoted at $256 per case). By assuming four procedures per nurse per day, reimbursement is $1,024, which leaves $666 after the deduction of salary and medication costs, or $166 per patient to defray the MR imaging room costs. The break-even MR imaging room rate is the ratio of the net reimbursement per patient in dollars to the time window per patient in minutes, which for the three groups of nurses is $166/15, or $11.07/min; $166/20, or $8.30/min; and $166/37, or $4.49/min for groups A, B, and C, respectively. This is the maximum rate at which MR room time must be charged if reimbursement for sedation is to cover all costs.
The take-home point is that specialized nurses can minimize the time delays and dollar costs of conscious sedation in MR imaging. It seems clear that if at least four sedation examinations are performed per day, it makes sense to have a specialized sedation nurse.
But what about adult practices, where conscious sedation is far less commonly used? For now, we will assume that MR room time is charged at the rate quoted by Bluemke and Breiter: $7/min (although in many practices a higher rate may apply). Assuming there are no safety implications to having nondedicated nurses monitor the sedation, if only one patient per day is sedated, it would not make economic sense to have a dedicated sedation nurse.
When using a nondedicated nurse within the radiology department, the cost per procedure at 0.25 full-time-equivalent nurse is $60 + $30 + (20 x $7) = $230. This cost is fully covered by the quoted sedation reimbursement of $256. However, if MR room time is charged at double the quoted rate ($14/min), then there will be a nonreimbursed cost of $114 per case.
It should be noted that, whereas the overhead for nurses’ salaries and for medication has a clear ceiling, prolonged delays in getting sedated patients onto the imager table can become very expensive. It seems that, if sufficient sedation examinations are performed to occupy a nurse full-time, it makes economic and logistical sense to have a dedicated nurse. Otherwise, local practice conditions dictate which nursing scenario is most economically viable.
Under all circumstances, safety takes precedence over economics, and careful patient selection, preparation, and monitoring must be stressed. We must ensure that the excellent safety record reported here by Bluemke and Breiter and earlier by other authors is replicated in all our practices. Nobody expects serious adverse effects or death to occur as a complication of MR imaging; that would be too high a price to pay for sedation.
FOOTNOTES
See also the article by Bluemke and Breiter in this issue (pp 645–652 ).
REFERENCES
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