Frequency and clinical impact of preserved Bispectral Index activity

during deep sedation in mechanically ventilated ICU patients

Electronic Supplementary Material

A/ BIS recordings

BIS values were recorded through a single front temporal electrode with the BIS®–XP 2000 monitor (software version 3.12) developed by Aspect Medical System, according to the manufacturer recommendations. Each electrode (BIS QuatroTM electrode sensor, Aspect Medical System) was applied on the patient’s forehead after careful skin cleaning. Sensor placement was systematically checked before each measurement to obtain a signal quality index of  70%. If used, forced air warming system was stopped because of potential artifacts with the BIS [1].

B/ Neuromuscular blockade monitoring protocol

Neuromuscular function was monitored by visual estimation of contractions of the adductor pollicis in response to a calibrated train-of-four (TOF) stimulation, as previously reported in our setting[2]. A 50 mA intensity was delivered using a peripheral nerve stimulator (Innervator NS252F, Fisher-Playkel Health Care, Baxter, Maurepas, France). When neuromuscular blockade was no longer considered as indicated, TOF at the adductor pollicis was performed every 15 min until obtaining four responses. A double burst stimulation was then delivered every 15 min until two equivalent responses had been obtained. This was considered to indicate near complete recovery from neuromuscular blockade [3].

C/ Management of sedation and analgesia

Dosages of midazolam and fentanyl were adjusted following a previously published algorithm [4]. Briefly, the aim of the algorithm was first to ensure patient tolerance to the ICU environment, including comfort, analgesia, calmness and adaptation to the ventilator, using increasing dosage of sedatives and analgesics, even if this would result in consciousness impairment. Especially, in patients with severe respiratory failure, the high dosages of sedatives and analgesics required to obtain strict adaptation to the ventilator, as deemed necessary by physician, often resulted in transiently altered consciousness. Once tolerance to ICU environment was achieved, sedative and analgesic dosage was progressively decreased to reach a satisfactory level of awakeness and comprehension, unless poor tolerance reoccurred and again required increasing dosages. This strategy is in accordance to the French Society of Critical Care 2007 guidelines [5].

According to the above algorithm [4], consciousness and tolerance to the ICU environment were assessed at least every 3 hours using the ATICE score immediately after onset of mechanical ventilation. In case of poor tolerance to the ICU environment as measured on the ATICE score (poor synchrony with the ventilator, agitation or face grimacing), the bedside nurse adjusted midazolam and fentanyl dosage, except in patients with very poor tolerance or in whom no improvement after two repeated bolus and subsequent increase in doses occurred. In such case the attending physician was alerted. As soon and as long as tolerance to the ICU environment was achieved, sedatives and analgesics were tapered according to the algorithm, until the objective for consciousness was reached (i.e. an ATICE Awakeness of 4 or 5 and Comprehension of 4 or 5). The bedside nurse decreased sedatives and analgesics around the clock. When ATICE Awakeness and Comprehension goals were reached, the patient could remain under sedatives or morphinics to maintain tolerance to the ICU environment. In this case, sedatives and morphinics were discontinued 3 hrs prior to the first T-piece trial.

D/ Instruments to assess ICU recall

The ICU Stressful Experiences Questionnaire examines specific recalls about the tracheal tube and more general recalls about ICU stay [6]. We adapted the instrument to quantify the amount and severity of recalls in a range from 29 (no recall) to 145 (extremely numerous and severe recalls) (Appendix). The ICU Memory Tool [7], adapted for use in the setting of shortly discharged ICU patients, consists in 2 questions about remembering of the overall hospital and ICU stay and a more specific question about recall contents categorised in recalls of factual events (score from 0 to 11), feelings (score from 0 to 6) or delusions (score from 0 to 6)(Appendix). Physicians who conducted the weaning process and interviewed the patients at discharge from ICU were blind to the BIS versus ATICE discordance level.

Adapted ICU Stressful Experiences Questionnaire

The patient is asked to quote each question “No”, “Yes, but was not bothered at all”, “Bothered a little”, “Quite a bit” or “Extremely”

Experiences of those patients who remembered the endotracheal tube (ETT)

1 – Remember not being able to speak
2 – Remember pain or discomfort associated with ett
3 – Remember feeling anxiety about the ETT
4 – Remember feeling choked by ETT
5 – Remember ETT interference with sleep
6 – Remember not getting enough air from the ETT
7 – Remember difficulty breathing after ETT removed

Experiences of those patients who remembered the intensive care unit

1 – Remember trouble speaking
2 – Remember being thirsty
3 – Remember procedures
4 – Remember feeling tense or keyed up
5 – Remember not being in control
6 – Remember difficulty swallowing
7 – Remember noise
8 – Remember feeling blue or depressed
9 – Remember feeling fearful
10 – Remember being restrained
11 – Remember missing spouse or friends
12 – Remember feeling something bad will happen
13 – Remember awakening in the middle of the night
14 – Remember feeling lonely
15 – Remember thoughts of death or dying
16 – Remember not being able to sleep
17 – Remember being in pain
18 – Remember trouble falling asleep
19 – Remember spells of terror or panic
20 – Remember feeling nervous when left alone
21 – Remember nightmares
22 – Remember feeling headaches

Scores:

Of the 30 original items, one item aimed at quantifying endotracheal tube pain was removed because item scaling and weighting differed from the other 29 items. Each of the 29 remaining items scored 1 (No, I don’t remember), 2 (Yes I remember, but was not bothered about this), 3 (Yes, bothered little), 4 (Yes, bothered quite a bit) or 5 (Yes, bothered extremely); range: 29-145.

Adapted from:

Rotondi AJ, Chelluri L, Sirio C, Mendelsohn A, Schulz R, Belle S, Im K, Donahoe M, Pinsky MR. Patients' recollections of stressful experiences while receiving prolonged mechanical ventilation in an intensive care unit. Crit Care Med. 2002; 30:746-52.

Simplified ICU Memory Tool

Do you remember being in intensive care ? / Yes
No
Do you remember all the stay clearly ? / Yes
No
What do you remember ? (Circle those things you remember)
Familya
Alarmsa
Voicesa
Lightsa / Facesa
Breathing tubea
Suctioninga
Being uncomfortableb / Darknessa
Clocka
Tube in your moutha
Ward rounda / Feeling confusedb
Feeling downb
Feeling anxious/
Frightenedb
Feeling that people were trying to hurt youc / Hallucinationsc
Nightmaresc
Dreamsc
Panicb
Painb

Scores:

a, factual memories: each item scores 1 point; range : 0-11

b, memories of feelings: each item scores 1 points; range : 0-6

c, delusional memories: each item scores 1; add 1 or 2 points for mention of nurse (1 point) or doctor (1 point) trying to kill the patient in the item “Feeling that people were trying to hurt you”; range : 0-6

Adapted from:

Jones C, Griffiths RD, Humphris G, Skirrow PM. Memory, delusions, and the development of acute posttraumatic stress disorder-related symptoms after intensive care. Crit Care Med. 2001; 29: 573-80

References

1. Hemmerling TM, Fortier JD (2002) Falsely increased bispectral index values in a series of patients undergoing cardiac surgery using forced-air-warming therapy of the head. Anesth Analg 95:322-3

2. Lagneau F, D'Honneur G, Plaud B, Mantz J, Gillart T, Duvaldestin P, Marty J, Clyti N, Pourriat JL (2002) A comparison of two depths of prolonged neuromuscular blockade induced by cisatracurium in mechanically ventilated critically ill patients. Intensive Care Med 28:1735-41

3. Drenck NE, Ueda N, Olsen NV, Engbaek J, Jensen E, Skovgaard LT, Viby-Mogensen J (1989) Manual evaluation of residual curarization using double burst stimulation: a comparison with train-of-four. Anesthesiology 70:578-81

4. De Jonghe B, Bastuji-Garin S, Fangio P, Lacherade JC, Jabot J, Appere-De-Vecchi C, Rocha N, Outin H (2005) Sedation algorithm in critically ill patients without acute brain injury. Crit Care Med 33:120-7

5. (2007). 4ème conférence de consensus commune: sédation et analgésie en réanimation (nouveau-né exclus). Available from

6. Rotondi AJ, Chelluri L, Sirio C, Mendelsohn A, Schulz R, Belle S, Im K, Donahoe M, Pinsky MR (2002) Patients' recollections of stressful experiences while receiving prolonged mechanical ventilation in an intensive care unit. Crit Care Med 30:746-52.

7. Jones C, Griffiths RD, Humphris G, Skirrow PM (2001) Memory, delusions, and the development of acute posttraumatic stress disorder-related symptoms after intensive care. Crit Care Med 29:573-80.