in this issue of critical care , triltsch and colleagues   report on the use of the bispectral index ( bis ) as a monitor of sedation in the paediatric intensive care unit ( picu ) . they attempted to correlate bis scores with the comfort score  a commonly used clinical sedation scoring system . the authors were able to demonstrate good correlation between bis scores and comfort scores during deep sedation and in cases where the electrical impedance of the bis electrodes was lowest . the stated aim was to determine whether bis is a useful tool for assessing the level of sedation in critically ill children . in their study , analysis of the bis score enabled correct prediction of the comfort score in 80% of cases overall , but in only 55% of lightly sedated children . the study population was quite selected in that 85% of patients had undergone cardiac surgery , and children were assessed only in the first few hours of admission to the picu . this makes the study findings less applicable to a general picu population , where children are admitted with a much broader range of diagnoses , particularly with neurological dysfunction and altered levels of consciousness , which would have an impact on the use of bis scores . the median duration of endotracheal intubation in a noncardiac picu would typically be in region of 34 days , and the utility of bis as a measure of sedation in critically ill children would therefore have to be assessed during the entire period of sedation rather than just focusing on the first few hours . this is particularly important , given the finding of the authors that analysis of the bis score would enable correct prediction of the comfort score in only 55% of lightly sedated children . during the course of a period of critical illness , children require different depths of sedation according to their clinical status and the interventions to which they are subjected . frequently , at the outset of a picu admission a relatively deep level of sedation is required to allow for the instigation of certain invasive procedures and therapies , particularly in certain specific disease states such as raised intracranial pressure or pulmonary hypertension . as a picu admission progresses there is usually a requirement for a lighter degree of sedation , and the utility of bis scores in guiding the titration of sedative agents longitudinally during a picu admission that includes such periods of lighter sedation remains questionable . crain and colleagues   studied 31 mechanically ventilated picu patients using the bis score and the comfort scale twice daily for up to 5 days and found that individual measurements of bis score and comfort scale were only moderately correlated . the authors concluded that bis scores may be best used to identify and prevent over - sedation in the picu . berkenbosch and colleagues   compared bis scores with simultaneously obtained clinical sedation scores in 24 mechanically ventilated picu patients . in differentiating adequate from inadequate sedation , bis values below 70 had a sensitivity of 0.870.89 and a positive predictive value of 0.680.84 . in differentiating adequate from excessive sedation , bis values below 50 had a sensitivity of 0.670.75 and a positive predictive value of 0.070.52 . the bis reliably differentiated between inadequate and adequate sedation , but it was relatively insensitive for differentiating between adequate and over - sedation . the data suggested that 80% of patients were adequately sedated when bis scores were maintained at less than 70 . at bis scores below 40 , fewer than half of the clinical sedation scores were found to indicate excessive sedation , whereas almost half of those determined to be excessively sedated patients on clinical sedation scales had bis scores in excess of 40 . a group of patients we are particularly anxious to sedate adequately are those receiving neuromuscular blocking agents . these patients are at risk of inadequate sedation and of being able to recall periods of neuromuscular blockade . aneja and colleagues   compared the bis score with clinical assessment of sedation using the ramsay score in 24 mechanically ventilated picu patients . they compared picu nurses ' clinical assessments of depth of sedation with bis scores of children receiving neuromuscular blocking agents . nurse assessments detected only 8% of those patients with a bis score of 80 or greater , and who were therefore at risk for awareness and recall . nurses clinical assessment for oversedation ( bis < 40 ) had a reasonable sensitivity of 89.7% but a low specificity of 38.6% . that study served to highlight the inadequacy of clinical scoring systems in the assessment of sedation in those receiving neuromuscular blocking agents . triltsch and colleagues   have demonstrated that the bis has potential for monitoring sedation in critically ill children , but that this role has yet to be clearly defined . it must be remembered that the optimal range of bis scores for varying depths of sedation remain poorly defined and are subject to great variability between patients . many factors encountered during critical illness , including body temperature variation , hypotension and even critical illness itself , may alter the bis score , as may drugs such as opioid analgesics , ketamine and nitrous oxide . electrical interference from picu equipment and muscle activity at lighter levels of sedation may both confound bis scores . there is currently insufficient evidence to recommend the routine use of bis monitors in the picu , even in those patients who are receiving neuromuscular blocking agents .
the bispectral index ( bis ) is a processed neurophysiological electroencephalographic parameter that may be used to evaluate the depth of sedation in critically ill children . 
 triltsch and colleagues attempted to correlate bis scores with a commonly used clinical sedation scoring system . 
 they were able to demonstrate good correlation during deep sedation and in cases where the electrical impedance of the bis electrodes was lowest . 
 studies have shown only moderate degrees of correlation between bis scores and clinical sedation scoring systems . 
 there is currently insufficient evidence to recommend routine monitoring of bis scores in critically ill children .