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Clinical assessment of level of sedation in the intensive care unit: a correlation study


Sedation and analgesia are common techniques widely used in the intensive care unit. Since complications such as prolonged sedative effects and associated long-term mechanical ventilation use are common, a careful assessment of level of sedation is warranted to avoid such complications. Nowadays, noninvasive devices like Bispectral Analysis (BIS) recorders are commercially available and are actually considered gold standard tests in level of sedation assessment; however, clinical scales (Ramsay's and the Observer's assessment of Alertness/Sedation [OAA/S] scales) are cheaper and more widely performed in critically ill patients. In the present study we compared clinical assessment scales with BIS recordings.


Prospectively we analyzed nine mechanically ventilated patients under deep sedation. We excluded patients with muscle relaxants, metabolic encephalopathy or primary central nervous disease. All patients were simultaneously evaluated with a BIS device, and with clinical assessment scales (Ramsay and OAA/S). At least 9 periodic measurements in 24 hours were performed in each patient, recording neuronal activity level and the signal quality index (SQI) with the BIS device, excluding all measurements with a SQI more or equal to 50%. Data comparisons among BIS recordings and each clinical scale were analyzed with Pearson's and Spearman's correlation, and determination coefficients, considering significant a 0.75 and a 0.11 value for each category (according to Colton), with a significance level set on 0.05.


Eighty-five measurements were analyzed. Correlation and determination coefficients are shown in the following Table.

Table 1


According to our statistical results, no clinical scale is strongly correlated to Bispectral Analysis in our sedated patients. Bispectral analysis is advised over clinical assessment to evaluate level of sedation in intensive care unit patients.

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Colomé-Ruiz, J., Rubio-Payán, D., Lescas-Vásquez, J. et al. Clinical assessment of level of sedation in the intensive care unit: a correlation study. Crit Care 5 (Suppl 1), P191 (2001).

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