Study on the Incidence of Delirium in a Respiratory Weaning Centre

Delirium has been defined, according to the Diagnostic and Statistical Manual of Mental Disorders (DSM IV), as a disturbance of consciousness characterized by an acute onset and fluctuating course. This impairment of cognitive functions, not being accounted for by a pre-existing dementia, reduces the patient's ability to receive, process and recall informations and its main features are inattention, disorganized thinking and reduced clarity of awareness of the environment.

All patients transferred from an intensive care unit to our respiratory weaning centre (RWC) will be screened for the occurrence of delirium. Our RWC is a 7-bed unit located within the respiratory department of a rehabilitation hospital and is fully equipped for invasive and non-invasive mechanical ventilation (MV) and for invasive and noninvasive cardiorespiratory monitoring. Patients are generally transferred to our unit from a general or surgical ICU for weaning from MV or, in case of patients already weaned, for rehabilitation, monitoring and intensive nursing care. All patients or their next of kin will give written informed consent to participate to the study and the study protocol has been approved by the local ethics committee.

For the assessment of delirium we use the Intensive Care Delirium Screening Checklist (ICDSC),a diagnostic tool already validated in the intensive care setting even in mechanically ventilated patients. It is based on the assessment of 8 different items dealing with the patient's mental status: each one is scored 0 or 1 in case of, respectively, absence or presence of the item itself and the final score is the resultant of the sum of the different items (see the appendix 1 for further details). The evaluation is performed on a daily basis by the physician in charge and the ICDSC score is ranked in the following way: 0 to 1 is considered normal, 2 to 3 is considered borderline, (i.e. indicative of a subsyndromal delirious state) and 4 or greater is considered diagnostic for delirium (13). In presence of a score greater than 1 the psychiatrist is called for consultation and diagnostic confirmation. Upon discharge of the patient from our RWC a score trend is drawn for every patient using the three highest scores sampled during the phases of admission, of mid stay and of discharge. Cases of overt delirium (only patients with ICDSC score ≥4) are categorized as hyperactive or hypoactive, according to a currently accepted classification. Treatment of delirium, when properly diagnosed, is instituted according to the psychiatist's prescriptions.

Patient's data collection include demographic data (age, gender), severity score (SAPS II), reason for admission (i.e. need for mechanical ventilation (MV) or not (NMV)) and previous episodes of delirium (hyperactive forms) occurring during ICU stay not linked to a pre-existing mental disease or to an acquired brain failure of vascular, metabolic or infectious origin. The Kelly scale is used for the assessment of the level of consciousness: the patient is considered comatose in presence of a persistent (>24 hours) Kelly score of ≥4. As far as the use of sedatives and analgesics in our RWC is concerned, our policy is based on the avoidance of continuous infusions regimens and on the limitation to the use of those drugs with a known or suspected capability to induce delirium; each drug is prescribed when strictly needed according to the judgement of the physician on duty and is targeted to the treatment of the specific symptom: pain, anxiety, insomnia etc.

Analysis of variance for repeated measures (MANOVA) is employed for statistical analysis, and a p value lower than 0.05 is considered the threshold value for statistical significance.