Special Circumstances

Regarding ARDS patients needing extracorporeal life support systems (ECLS), there is a gray area about sedation, where safety aspects and the ability to positively influence recovery must be balanced. Patients on ECLS have numerous risk factors to develop both delirium during the ICU stay and PTSD after discharge. Hyperactive delirium or agitation can be life-threatening for these patients, so that a consequent monitoring and a symptomatic therapy of stress, anxiety, delirium, pain, and insomnia is essential to safely achieve a target RASS of 0. The higher level of alertness allows the patient to actively partake in physical exercises [94] that is considered a feasible and safe goal [95, 96]. International guidelines recommend a strict definition of sedation targets for patients on ECLS, including frequent clinical monitoring and continuous adjustment of the level of sedation required [4].

Positioning therapy has been demonstrated effective in ameliorating prognosis of severe ARDS patients. It is used for prophylaxis and treatment of respiratory dysfunctions and requires an individual sedation target. Changes of the position frequently represent a challenge for the symptomatic treatment of anxiety, stress, and pain. Therefore, a symptom-orientated therapy should be adapted for changing demands during positioning therapy. Though a deep sedation may be indicated for patient repositioning [97], an excessive sedation should be avoided through the use of objective tools based on EEG analysis, as previously described.

The use of non-depolarizing neuromuscular blockers in patients with severe ARDS is suggested during the first 48 ICU hours. Despite this practice, it is suggested not to routinely increase the dose of sedatives, when accompanied by an infusion of opiates, even in patients subjected to permissive hypercapnia [98]. To control respiratory rate, fentanyl is recommended as the analgesic of choice in patients with hemodynamic instability, bronchial asthma, or COPD, with respect to the other opiates. Methadone via the enteral route could be used in patients receiving opiates for more than 5 days, but still needing mechanical ventilation. Once tracheostomy is performed, it is advisable to consider a decrease in sedative and analgesic regimens.

After the hyperacute phase of respiratory failure, a defined sedation and analgesia monitoring and dose adjustment protocol is recommended, to shorten the weaning process. This protocol should include daily evaluation of sedation, an awakening test and a spontaneous breathing test. It is advisable not to use benzodiazepines in the withdrawal of MV. Dexmedetomidine is recommended in case of weaning difficulties, in patients with withdrawal syndrome, or after failed attempts of weaning secondary to agitation and delirium [67]. Low-dose remifentanil in continuous infusion is another effective alternative during weaning process. Music therapy is a possible non-pharmacological adjuvant to sedation [99]. Melatonin supplementation could be useful to decrease the need for sedative drugs, then shortening the ventilation length [100], and to restore the sleep-wake rhythm.