Fig. 5.1
A working model of pediatric sedation. The x-axis is the time of phase of sedation. The y-axis is the depth of sedation, ranging from inadequate to oversedation. A sedation scale should be able to accurately assess the depth of sedation and maximize the chance that the patient is in the goal zone. The black dots are the patient at a single point in time, ranging from preprocedure, through intra- and post-procedure. C designates the work done by the provider to counteract the adverse effects of sedation or accomplish a task. C1 is the procedure control loop, C2 the procedural pain and anxiety control loop, and C3 the sedation-related respiratory depression control loop. R1 is the undesired side effects of therapeutic action: R1 undersedation and pain, R2 oversedation, and R3 rescue from oversedation (Adapted from Cravero JP, Blike GT, Surgenor SD, Jensen J. Development and validation of the Dartmouth Operative Conditions Scale. Anesth Analg. 2005;100:1614–21, with permission from Lippincott Williams & Wilkins)
Sedation Scales
The Joint Commission, the American Academy of Pediatrics, and the American Society of Anesthesiologists have recently revised their definitions of the levels of pediatric sedation [5, 6] (Table 5.1, Figure 5.2). The four levels of sedation are now minimal, moderate, deep, and general anesthesia. The previously used term “conscious sedation” has been eliminated because it was misleading, and particularly in pediatric patients, they can change rapidly from minimal to deep levels of sedation. Any assessment of levels of sedation needs to take these basic considerations into account.
Table 5.1
American Academy of Pediatrics/Joint Commission/American Society of Anesthesiologists Definitions of Levels of Sedation
Minimal sedation (anxiolysis) | A drug-induced state during which patients respond normally to verbal commands |
Although cognitive function and coordination may be impaired, ventilatory and cardiovascular functions are unaffected | |
Moderate sedation (previously called conscious sedation or sedation/analgesia) | A drug-induced depression of consciousness during which patients respond purposefully to verbal commands either alone or accompanied by light tactile stimulation |
No interventions are required to maintain a patent airway, and spontaneous ventilation is adequate | |
Cardiovascular function is usually maintained | |
Deep sedation | A drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposefully after repeated or painful stimulation. (Note: reflex withdrawal from a painful stimulus is not considered a purposeful response) |
The ability to independently maintain ventilatory function may be impaired | |
Patients may require assistance in maintaining a patent airway and spontaneous ventilation may be inadequate | |
Cardiovascular function is usually maintained | |
General anesthesia | A drug-induced loss of consciousness during which patients are not arousable, even to painful stimulation |
The ability to independently maintain ventilatory function is often impaired | |
Patients often require assistance in maintaining a patent airway, and positive pressure ventilation may be required because of depressed spontaneous ventilation or drug-induced depression of neuromuscular function | |
Cardiovascular function may be impaired |
Fig. 5.2
The sedation continuum. A patient may readily pass from a light level of sedation to deep sedation or general anesthesia. Healthcare providers must be prepared to increase vigilance and intensity of monitoring consistent with the depth of sedation. One should consider all children younger than the age of 6 years as deeply sedated because “conscious sedation” in this age group for most children is an oxymoron (ASA, American Society of Anesthesiologists; JCAHO, Joint Commission on Accreditation of Healthcare Organizations) (Adapted from [6].)
Sedation scales are indeed necessary for pediatric procedural sedation, particularly when practiced by nonanesthesiologists. For example, Reeves et al. [7] studied 16 children undergoing propofol sedation for bone marrow aspiration by nonanesthesiologists, and found that for all children, their level of consciousness, motor activity score, and bispectral index score was consistent with either deep sedation or general anesthesia at some point during the procedure. In the largest pediatric procedural cohort reported to date, Cravero et al. assessed 49,836 propofol sedations. Complications were noted in 5.92 % of patients, including an airway or pulmonary complication in 1.17 %, yet there was no assessment of depth of sedation reported [8]. Sedation scales are essential to minimize complications from sedation by providing early warning of sedation that is deeper than intended, to allow the practitioner to intervene proactively, instead of having to rescue the patient from an episode of hypoxemia from airway obstruction or apnea. The ideal sedation scale would be applicable to children of all ages, easy and rapid to administer to allow repeated objective assessment, and correlate both with depth of sedation necessary for successful completion of the procedure and with adverse effects of sedation, i.e., airway obstruction, hypoxemia, hypotension, and bradycardia. It would be validated against other accepted scales, and also an objective method of assessment such as a processed EEG technique. And, it would be further validated in very large numbers of patients to determine that the scale did correlate with outcomes. Unfortunately, no such ideal sedation scale exists. However, there are a number of objective and semiobjective methods, some validated, to assess depth of sedation.
The Ramsay Scale
The Ramsay Sedation Scale (RSS) was described by Ramsay and colleagues in 1974 for the purpose of monitoring sedation with alphaxalone/alphadolone [9] (Table 5.2). It has been validated by several methods including a modified Glasgow Coma Scale and the Sedation-Agitation Scale [10]. The Ramsay Scale was one of the earliest sedation scales, and although not strictly validated in children, it is one of the most widely used scales for assessing and monitoring pediatric sedation in daily practice, as well as in clinical research. It spans the continuum of sedation but does not clearly separate purposeful from nonpurposeful responses.
Table 5.2
Ramsay Scale
Level | Characteristics |
|---|---|
1 | Patient awake, anxious, agitated, or restless |
2 | Patient awake, cooperative, orientated, and tranquil |
3 | Patient drowsy, with response to commands |
4 | Patient asleep, brisk response to glabellar tap or loud auditory stimulus |
5 | Patient asleep, sluggish response to stimulus |
6 | Patient has no response to firm nail-bed pressure or other noxious stimuli |
A later modification of the Ramsey scale more clearly coincides with the AAP and Joint Commission guidelines (Table 5.3) [6]. A score of 2–3 is anxiolysis, 4–5 is moderate sedation, 6 is deep sedation, and 7–8 is general anesthesia.
Table 5.3
Modified Ramsay Sedation Scale with American Academy of Pediatrics/Joint Commission/American Society of Anesthesiologists designation
Score | Characteristics |
|---|---|
1 | Awake and alert, minimal or no cognitive impairment |
2a | Awake but tranquil, purposeful responses to verbal commands at conversation level |
3a | Appears asleep, purposeful responses to verbal commands at conversation level |
4b | Appears asleep, purposeful responses to verbal commands but at louder than usual conversation level or requiring light glabellar tap |
5b | Asleep, sluggish purposeful responses only to loud verbal commands or strong glabellar tap |
6c | Asleep, sluggish purposeful responses only to painful stimuli |
7d | Asleep, reflex withdrawal to painful stimuli only (no purposeful responses) |
8d | Unresponsive to external stimuli, including pain |
The Observer’s Assessment of Alertness/Sedation Scale and Modified Observer’s Assessment of Alertness/Sedation Scale
The Observer’s Assessment of Alertness/Sedation Scale (OAA/S) [11] was developed to measure the alertness of adult subjects who are sedated with benzodiazepines. It assesses consciousness level in four areas: responsiveness, speech, facial expression, and eyes (Table 5.4). The OAA/S was validated in 18 healthy males 19–44 years of age, who received intravenous midazolam, initial dose 0.035 mg/kg, followed by additional doses of 0.015 mg/kg every 60–90 s until one of two levels of sedation was reached: light or heavy. A placebo group was also used, and two raters determined the depth of sedation using the OAA/S and 100 mm visual analog scale (VAS) rating patients from 0 (very sedated) to 100 (completely alert). Each subject was tested three separate times in a crossover design to assess the OAA/S reliability, criterion, and construct validity. The scale was found to be reliable with high correlations between raters, to have strong criterion and behavioral validity with consistently decreasing scores for placebo, light, and heavy sedation. The construct validity among the four components was also strong, as was the validity for subsequent administration to the same subject in the crossover phase. Finally, the investigators also used two performance tests—the Digit Symbol Substitution Test and the Serial Sevens Subtraction Test—to compare to OAA/S scores and again found strong correlation.
Table 5.4
The Observer’s Assessment of Alertness/Sedation Scale
Assessment categories | ||||
|---|---|---|---|---|
Responsiveness | Speech | Facial expression | Eyes | Composite score level |
Responds readily to name spoken in normal tone | Normal | Normal | Clear, no ptosis | 5 (alert) |
Lethargic response to name spoken in normal tone | Mild slowing or thickening | Mild relaxation | Glazed or mild ptosis (less than half the eye) | 4 |
Responds only after name is called loudly and/or repeatedly | Slurring or prominent slowing | Marked relaxation (slack jaw) | Glazed and marked ptosis (half the eye or more) | 3 |
Responds only after mild prodding or shaking | Few recognizable words | – | – | 2 |
Does not respond to mild prodding or shaking | – | – | – | 1 (deep sleep) |
Despite this thorough validation of the OAA/S in adult patients, and its use in several sedation research studies in children [12, 13], the OAA/S has not been separately validated in children. The OAA/S has been used in the validation of the University of Michigan Sedation Scale [14], and in assessments of the reliability of the bispectral index monitor in children [15].
The Modified Observer Assessment Sedation Score (MOAA/S) uses only the responsiveness category of the OAA/S. This category was separately validated in the original study [11] but, as with the OAA/S, has not been separately validated in children.
The COMFORT Scale
The COMFORT Scale is a physiologically based scale that was originated and validated in children receiving intensive care, and as such is not completely applicable to the procedural sedation environment [16] (Table 5.5). It was tested and validated in 37 ventilated pediatric patients, and inter-rater agreement and internal consistency were very strong. Criterion validity, assessed by comparison with concurrent global ratings of pediatric intensive care unit (PICU) nurses, was also high. It is included here as an example of such a physiologically based scale. An added dimension is the assessment of pain or discomfort. Generally, a COMFORT score between 18 and 26, with each area scored as 2–3, is desirable to signify appropriate levels of sedation in the ICU setting. It is clear that this scale is complex and will require several minutes to assess, and as such is appropriate for ICU care where the scale is performed no more frequently than every hour. In the context of most procedural sedation, this scale will be inappropriate.
Table 5.5
The COMFORT Score
Domain | Characteristics | Score |
|---|---|---|
Alertness | Deeply asleep | 1 |
Lightly asleep | 2 | |
Drowsy | 3 | |
Fully awake and alert | 4 | |
Hyperalert | 5 | |
Calmness/agitation | Calm | 1 |
Slightly anxious | 2 | |
Anxious | 3 | |
Very anxious | 4 | |
Panicky | 5 | |
Respiratory response | No coughing and no spontaneous respiration | 1 |
Spontaneous respiration with little or no response to ventilation | 2 | |
Occasional cough or resistance to ventilator | 3 | |
Actively breathes against ventilator or coughs regularly | 4 | |
Fights ventilator; coughing or choking | 5 | |
Physical movement | No movement | 1 |
Occasional slight movement | 2 | |
Frequent slight movement | 3 | |
Vigorous movement limited to extremities | 4 | |
Vigorous movement including torso and head | 5 | |
Blood pressure | Blood pressure below baseline | 1 |
Blood pressure consistently at baseline | 2 | |
Infrequent elevations of 15 % or more (1–3 observations) | 3 | |
Frequent elevations of 15 % or more (more than three episodes) | 4 | |
Sustained elevation of >15 % | 5 | |
Heart rate | Heart rate below baseline | 1 |
Heart rate consistently at baseline | 2 | |
Infrequent elevations of 15 % or more (1–3 observations) | 3 | |
Frequent elevations of 15 % or more (more than three episodes) | 4 | |
Sustained elevation of >15 % | 5 | |
Muscle tone | Muscle totally relaxed | 1 |
Reduced muscle tone | 2 | |
Normal muscle tone | 3 | |
Increased muscle tone and flexion of fingers and toes | 4 | |
Extreme muscle rigidity and flexion of fingers and toes | 5 | |
Facial tension | Facial muscles totally relaxed | 1 |
Facial muscle tone normal; no facial muscle tension evident | 2 | |
Tension evident in some facial muscles | 3 | |
Tension evident throughout facial muscles | 4 | |
Facial muscles contorted and grimacing | 5 |
The University of Michigan Sedation Scale
The University of Michigan Sedation Scale (UMSS) is an assessment tool that has been shown to be valid when compared to the OAA/S Scale and other scales of sedation (Table 5.6) [14]. It is a level of consciousness tool that readily separates patients into the sedation categories defined by the AAP, ASA, and Joint Commission. It does not explicitly rate pain, and does not include an assessment of vital signs. In a study of 32 children aged 4 months to 5 years undergoing computed tomography (CT) scanning with oral chloral hydrate, 50–75 mg/kg, Malviya et al. [14] validated the UMSS by comparing the scores assessed every 10 min before, during, and after the procedure by the clinical sedation nurse, with assessments made by trained, blinded observers of the videotaped assessments, which were edited and viewed in random order. UMSS was compared to a 10-point VAS and the OAA/S. One hundred sixty-four observations were made, and the UMSS showed an excellent correlation with VAS (r = 0.955) and OAA/S (r = 0.929), p < 0.0001 for both. There was excellent inter-rater agreement between sedation nurse and trained observers at UMSS 0 and 1, and good agreement at UMSS 3 and 4, as well as excellent agreement in a test–retest scenario where 75 videotaped observations were rescored at a later date. Thus it would appear that the UMSS meets several of the requirements for the ideal sedation scale, in that it is validated, rapid to administer, and allows repeated observations. A problem shared with other scales is the need to arouse the patient to make an assessment; this is not possible during a procedure such as a magnetic resonance imaging (MRI) scanning sequence, and may be undesirable if the patient remains aroused, interfering with the procedure.
Table 5.6
University of Michigan Sedation Scale (UMSS)
Score | Characteristics |
|---|---|
0 | Awake and alert |
1 | Minimally sedated: tired/sleepy, appropriate response to verbal conversation and/or sound |
2 | Moderately sedated: somnolent/sleeping, easily aroused with light tactile stimulation or a simple verbal command |
3 | Deeply sedated: deep sleep, arousable only with significant physical stimulation |
4 | Unarousable
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