The "sedation holiday" came up in Question 1 from the first  paper of 2013 and Question 5 from the second paper of 2008, a time scale which is somewhat surprising in its lateness. You'd have expected it to come up closer to the year 2000, shortly after the seminal Kress paper was published in NEJM, or when Jacobi et al promoted the practice as the new standard of care in ICU.  Instead, the college waited until 2008. The 3013 question at least makes more sense because the well-received Canadian trial of this practice was published in 2012 (Mehta et al). The best resource for a "critically evaluate" answer to such a question is PulmCCM, where the primary author, enraged and frothing,  fell upon the practice and tore it limb from limb. Here, only a brief summary will be attempted.

Rationale for daily interruption of sedation

• Exposure to sedating agents is undesirable, given that most agents have unpleasant side-effects
• Interruptions in sedation may decrease the total dose of sedation over the course of one's ICU stay
• Decreased sedation means better cooperation with physiotherapy and weaning trials
• Earlier extubation, decreased healthcare costs and shorter ICU stay should theoretically result.

Proposed advantages of the sedation holiday

• More rapid weaning from ventilation
• Reduction in ICU length of stay
• Reduced need for vasopressors
• Reduced need for fluid boluses

Expected disadvantages of the sedation holiday

• Greater risk of self-extubation
• Greater psychological distress; potential for PTSD
• Increased nursing workload
• Increased patient-ventilator dyssynchrony
• In fact, more sedation (Mehta et al, 2012): there was an increase in the total daily dose of midazolam and fentanyl: the patients went berzerk during their holiday, and required large boluses.

Arguments in favour of this practice

• In the recent trial (Mehta et al, 2012) the rate of self-extubation was unchanged (clearly, the patients were well restrained!)
• There was no real increase in identified delirium between the groups (so, sedation holidays don't promote delirium)
• The nursing workload was not substantially increased. The difference was rated on a 10-point visual analog scale. The difference was 4.2 vs. 3.8. So, going by this average measurement, having a sedation holiday made the patient 4% more difficult to look after.

Evidence exploring the utility of the daily sedation holiday

• Kress et al (2000) - small single centre RCT; n=128
  • length of stay in ICU and duration of ventilation was reduced
• Kress et al (2003) - small single centre RCT; n=108
  • reduced symptoms of PTSD; no adverse psychological outcome
• Girard et al (2008) - multicentre trial, n=336
  • Reduced mortality at 1 year, but increased risk of self-extubation
• Mehta et al (2012) - multicentre randomised controlled trial, n=430
  • No reduction in length of ICU stay or duration of ventilation
• Cochrane verdict (2014) - meta-analysis, n=1282; no strong evidence in support of this practice. Tracheostomy may be performed less often.