Safety and Efficiency of Sedation for MR Imaging

Abstract & Commentary

Synopsis: Use of sedation for MR imaging results in a high percentage of good quality examinations. The use of skilled and trained radiology nurses to administer and monitor sedated patients has resulted in safe and highly effective sedation in both pediatric and adult patients.

Source: Bluemke DA, Breiter SN. Sedation procedures in MR imaging: Safety, effectiveness, and nursing effect on examinations. Radiology 2000;216:645-652.

Magnetic resonance (mr) sedation is costly in terms of time for the procedure, scheduling problems, and personnel requirements of physicians and nurses. This study was undertaken to evaluate by review of records, the safety and effectiveness of sedation for adults and children undergoing MR imaging. Patients who were sedated were continuously monitored for hemoglobin oxygen saturation (SpO2) and pulse rate. Blood pressure measurement was performed at five-minute intervals during induction and recovery, and between MR pulse sequences. Visual patient monitoring with a camera of the magnet bore was required. Sedation screening included a physical examination, history of present illness, past medical history, and review of systems. The contraindications to sedation were allergy to a sedation medication, less than six hours of fasting from solids and less than two hours fasting from liquids; abnormal electrocardiogram; conditions that might result in airway compromise; hemodynamic instability; and coexistent morbid conditions. Condition was classified as American Society of Anesthesiologists system: Class I (normally healthy) and II (mild systemic disorder).

Medication and dose used were based on patient age and weight. Medications used were Chloral hydrate, Pentobarbital sodium, Diazepam, and Alprazolam.

From March 1991 to November 1998, 4761 patients received at least one sedation medication. Only 78% of scheduled sedation MR examinations were performed. Of these, 93.5% had successful sedation. Time to sedation was a mean of 23.6 minutes for specialized MR sedation nurses and 26.8 minutes for general radiology nurses. For inpatient nurses, the sedation time was 47.3 minutes and more variable. Mean duration of sedation was 63.6 minutes. Adverse events were recorded in 20 (0.42%) patients. Eight patients developed hypoxemia—four had cough and congestion so that associated motion did not allow completion of the examination; three patients had bronchospasm and stridor. All were discharged home and had no long-term complications.

The break-even costs were 37% more for general radiology nurses than for specialized MR sedation nurses performing the procedure. Conscious sedation is safe and effective. A trained specialized nursing staff reduces the cost and variability of effectiveness.

Comment by Beverly P. Wood, MD, MSc

Sedation of patients for prolonged procedures and those requiring immobility has been a longstanding practice in pediatric radiology, with protocols established for sedation preparation, monitoring, and discharge. However, sedation of adults with claustrophobia, agitation, or other causes of motion may ensure completion of an adequate examination. As in children, monitoring of the airway and respiration is essential, especially in the noisy and longer examination situation of MR.

The study includes a large number of children, but it also included 20% adults who required sedation. The study indicates that sedation is safe, adverse reactions are few, and nondiagnostic studies rarely occur.

Of particular importance is specialized training and expertise in the sedation staff. Sedation is more effective and more efficient when administered by trained nursing staff in the department.

Despite the low incidence of complications of sedation, continuous monitoring is essential and blood oximetry for even minor alterations is a sensitive indicator of pending airway and respiratory complications. When possible, blood pressure and respiratory monitoring are also advisable. Since good screening, development of effective pharmacologic protocols, and constant monitoring are the key to successful sedation, a dedicated nursing staff is advisable.

References

1. Volle E, et al. Pediatr Radiol 1996;26:280-281.

2. Committee on Drugs. Pediatrics 1992;89:1110-1115.