Paediatric Anaesthesia 2000 10: 195–199

Quality of sedation during mechanicalventilation

S.D. PLAYFOR MBBS∗ , DAVID A. THOMAS MBBS∗ ,

IMTI CHOONARA† MBCHB MD AND ANITA JARVIS∗∗Paediatric Intensive Care Unit, Queens Medical Centre, Nottingham NG7 2UH and†Academic Division of Child Health, University of Nottingham, Derbyshire Children’sHospital, Uttoxeter Road, Derby DE22 3NE, UK

SummaryThe aim of the study was to determine the quality of sedation in

ventilated patients on a general paediatric intensive care unit

(PICU), including those treated with infusions of neuromuscular

blocking agents. Twenty-eight ventilated children on a PICU had

their level of sedation determined using an arousability scale

dependent upon the response to tracheal suction. Observed levels of

sedation were then compared to a predetermined desired level of

sedation. A total of 81 assessments were performed and 90% were

considered satisfactory. Thirty-two of these assessments were

performed in 15 children following the temporary discontinuation of

infusions of neuromuscular blocking agents; 97% of these

assessments were considered satisfactory. A regime of continuous

intravenous midazolam and morphine with additional oral sedation

using chloral hydrate and antihistamines when required provides a

satisfactory level of sedation for the majority of children ventilated

on a PICU, including those treated with infusions of neuromuscular

blocking agents.

Keywords: sedation; midazolam; critically ill patients; paediatric

intensive care unit

Introduction given the possibility of patients being insufficiently

sedated and aware during their administration (2).The use of sedation is an important aspect of the

There is a variety of methods available for thecare received by ventilated children in the paediatric

assessment of sedation, all of which have limitationsintensive care unit (PICU). Effective sedation can

(3). We have assessed the quality of sedation infacilitate mechanical ventilation, reduce anxiety, and

ventilated children using an existing scoring systemallow for better tolerance of medical procedures (1).

based on the response to tracheal suction.The quality of sedation in those receiving neuro-

muscular blocking agents is of particular concern,Methods

This project took place on a general PICU in a tertiary

referral centre, over 20 consecutive weeks, betweenCorrespondence to: S.D. Playfor, Paediatric Intensive Care Unit,

Queens Medical Centre, Nottingham NG7 2UH, UK. April and August 1998. The project was reviewed

195 2000 Blackwell Science Ltd

196 S.D. PLAYFOR ET AL.

Table 1and approved by the chairman of the local ethicsSedation scalecommittee; parental consent was not required as

sedation levels are assessed for clinical reasons. Sedation score Patient responseDuring an initial pilot period of 8 weeks only patients

1 No reponse to tracheal suctionreceiving infusions of neuromuscular blocking agents2 Cough and small limb movement and/or

were studied. This was in order to allow a supervisedgrimace in response to tracheal suction

introduction of the sedation scoring system, and to 3 Agitation with major limb movement or crying

in response to tracheal suctionensure that patients did not undergo any additional4 Patient is awake and moving but is not agitatedprocedures because of the project. Subsequently, all

when disturbedventilated and sedated children were considered 5 Patient is awake and restless or distressed

when not disturbedfor inclusion. Exclusion criteria included children

admitted in status epilepticus, those with neuro-

muscular problems impairing movement in response

to stimulation, and those considered either too

physiologically unstable to tolerate tracheal suction in order to achieve satisfactory sedation. If patients

become obviously distressed during physiotherapy,or likely to die imminently.

The sedation and analgesia regime routinely medical or nursing procedures then small bolus doses

of existing sedative agents are given to produceemployed in our unit is a combination of midazolam

and morphine, given by continuous intravenous satisfactory sedation. Any child requiring thorough

neurological examination would have their sedativeinfusion. Additional oral sedation using chloral

hydrate and/or antihistamines (promethazine, agents temporarily discontinued until such an

evaluation was completed.trimeprazine or chlorpheniramine) is prescribed as

required for certain patients in order to augment All patients, including those in the pilot study, had

their level of sedation formally assessed once inunsatisfactory sedation or to enable the weaning of

intravenous sedative agents after their prolonged every 24-h period, using a scoring system originally

described by Ratcliffe (4). This system involvesadministration. Starting doses of morphine infusions

are 10 lg·kg−1·h−1 for ventilated infants less than observation of the patient and noting their response

to tracheal suction, categorising their response using1 years of age, and 20 lg·kg−1·h−1 for ventilated

children over 1 years of age. Midazolam infusions a five-point scale (Table 1). On our unit tracheal

suction is not a routinely performed procedure andare started at 120 lg·kg−1·h−1. It is usual practice

to administer initial bolus doses of these agents if is only carried out on the basis of clinical need.

Patients who had never received an infusion ofsedation is judged to be unsatisfactory at that time;

doses of such boluses would be 10–20 lg·kg−1 of neuromuscular blocking agent, or who had

discontinued such an infusion for at least 2 h, hadmorphine and 120 lg·kg−1 of midazolam. Any oral

sedatives were prescribed as follows: chloral hydrate their level of sedation assessed by the PICU nursing

staff during their first planned episode of tracheal100 mg·kg−1·day−1 in four divided doses, pro-

methazine 1 mg·kg−1·day−1 in three divided doses, suction after 07.00 h each day. Patients included in

this study received no additional episodes of trachealtrimeprazine 1.5–3 mg·kg−1day−1 up to three doses

and chlorpheniramine 200–350 lg·kg−1·day−1 in two suction other than those required for clinical reasons.

The level of sedation was recorded and comparedto six divided doses.

The infusion rates of sedative agents are titrated with a desired level of sedation, which was specified

by the Paediatric Intensivist each morning.by the nursing staff against behavioural and

physiological parameters assessed at each patient If children were receiving continuous infusions

of neuromuscular blocking agents, these werecontact (changes in heart rate, pupillary responses,

respiratory patterns, lacrimation and patient temporarily discontinued and a train-of-four

peripheral nerve stimulator (TOF-Guard, Organon-movements) within limits prescribed by the medical

staff. The maximal doses used are usually Teknika NV, The Netherlands) used to determine

when the neuromuscular blockade had completely480 lg·kg−1·h−1 of midazolam and 50 lg·kg−1·h−1 of

morphine; when necessary these limits are exceeded worn off. This is a technique routinely performed

2000 Blackwell Science Ltd, Paediatric Anaesthesia, 10, 195–199

QUALITY OF SEDATION DURING MECHANICAL VENTILATION 197

Table 2to allow assessment of sedation and neuromuscularClinical diagnosesfunction. The temporary discontinuation of neuro-

muscular blocking agents would occur at various Clinical diagnosis Number of patientstimes during the day, supervised by a single in-

Head injury 7vestigator (SP), and was timed to coincide with aPneumonia 6

planned episode of tracheal suction. The level ofMeningococcaemia 4

sedation was then assessed using the technique Scoliosis repair 4

General surgery 2described above and the infusion recommenced.Septicaemia 1Three levels of sedation were considered ideal inCroup 1

different circumstances. A score of 1 (Table 1) is Other neurosurgery 1

Oncology 1the optimal level of sedation for children recentlyNear drowning 1admitted with severe head injury, a score of 2 is

desirable for children receiving a high level of intens-

ive care with frequent invasive procedures, and a

score of 4 is preferred for children prior to extubation.

Assessments that correlated exactly with the desired

level of sedation were considered ideal. Assessments

of 1, 2 or 4 on our scale, when this value was not in

agreement with the desired level of sedation, were

interpreted as acceptable as such children are not

distressed. Assessments that were ideal or acceptable

were considered satisfactory. Scores of 3 or 5, which

represent a patient in distress, were always con-

sidered unsatisfactory.

Following the assessment of sedation, it was left

to the discretion of the nurse who had elicited the

response whether to alter the doses of sedative agents

50

01

Nu

mb

er o

f as

sess

men

ts

Sedation score

40

30

20

10

2 3 4 5

12

4 4

42

710

1

IdealAcceptableUnacceptable

4

or not. Thus the results of these formal assessmentsFigure 1of sedation were acted upon on the same basis asNumber and acceptability of sedation assessments.

the informal assessment of sedation that would have

occurred during episodes of tracheal suction had this

project not been in progress.

occurred between 07.00 h and 22.30 h; this variation

arose because tracheal suction is not a routinelyResultsemployed procedure and because of assessments

carried out following temporary discontinuation ofTwenty-eight children were studied (15 female and

13 male), with a median age of 3.46 years (range neuromuscular blocking agents. In 14 patients (50%),

assessments could not be carried out until the second1 month to 16 years) and their clinical diagnoses

are shown in Table 2. During the pilot period, complete day of admission.

Eighty-one assessments were carried out and thenine patients were studied. During the subsequent

12 weeks, 93 patients were admitted to the PICU of sedation scores observed are shown in Figure 1. Sixty-

four assessments (79%) were ideal as the sedationwhom 32 were ventilated. Of these ventilated

patients, 19 (59%) were eligible and studied. The score correlated exactly with the desired level of

sedation. An additional nine assessments (11%) weremost common reason for ventilated children being

excluded was that the duration of their sedated acceptable as the observed sedation scores indicated

that the patient was comfortable. The level of sedationventilation was too brief to include an episode of

tracheal suction after 07.00 h. was therefore judged to be satisfactory in 90% of

assessments. Only eight assessments (10%) wereEach patient received a mean total of 2.9

assessments during admission (range 1–7) which unsatisfactory in that the observed sedation scores

2000 Blackwell Science Ltd, Paediatric Anaesthesia, 10, 195–199

198 S.D. PLAYFOR ET AL.

Discussion

Midazolam is the most widely used sedative agent

given to critically ill children in the UK (5). It has

been used for many years with a good record of

safety, its pharmacokinetics have been well described

(6) and it is recognized as an effective sedative agent

(7,8).

Since the work of Ramsay (9), many scoring

systems have been described for the assessment of

sedation. Some, similar to the one employed here,

are arousability scales relying on the response of

450

01

Do

ses

in µ

g·k

g–1

·h–1

Day of admission to PICU

250

400350300

20015010050

2 3 4 5 6 7 8

44.2

306

372

44.476

54.8

396

336

33.5 42.6

294

342

150

26

MorphineMidazolam

the patient to external stimulation. These scales are

simple and easy to apply at the bedside but areFigure 2Variation in administered doses of sedative agents by day of hampered by the need to disturb the patient. Otheradmission.

scoring systems, such as the COMFORT scale (10,11),

combine observational and physiological parameters

and do not require the patient to be disturbed, but

are rather cumbersome to use in practice.of 3 and 5 indicated that the patient was distressed.We have used an arousability scale based on theThese eight unsatisfactory assessments were per-

response to tracheal suction. By limiting formalformed in five children with a mean age of 2.0 years;assessments to coincide with planned episodes ofa single child had four unsatisfactory assessmentstracheal suction, we have ensured that patientsout of six performed during her PICU admission,receive no extra disturbance. In order to assessfour further children had one unsatisfactorypatients receiving infusions of neuromuscularassessment each out of a total of 15 assessments.blocking agents we have coordinated the temporaryAdditional oral sedation was being given at the timediscontinuation of such infusions with plannedof five of the eight unsatisfactory assessments (63%).episodes of tracheal suction. A daily discontinuationOf the 32 assessments carried out in childrenof neuromuscular blockade may be desirable forpreviously receiving infusions of neuromuscularseveral reasons (12). It not only allows for theblocking agents, 28 (88%) were ideal and three (9%)assessment of sedation and a thorough neurologicalwere acceptable. The level of sedation was thereforeexamination, but also may help to preventjudged to be satisfactory in 97% of assessments. Onlyaccumulation of neuromuscular blocking agents,one assessment (3%) was unsatisfactory.particularly in children concurrently receiving steroidThe mean doses being received during assessmentstreatment who may be at increased risk of developingoverall were 312 lg·kg−1·h−1 (SEM 44.8) of midaz-‘critical care myopathy’ (13,14).olam, and 45.9 lg·kg−1·h−1 (SEM 6.2) of morphine.

We have formally assessed the level of sedationThe mean doses being received during unsatisfactory

once in every 24-h period and it is clear that levelsassessments were 221 lg·kg−1·h−1 of midazolam, and

of sedation can vary widely over short periods of34 lg·kg−1·h−1 of morphine. The mean doses received

time (15). In practice, sedation is informally assessedat the time of assessment on each day of admission

by PICU nursing staff at every patient contact andare shown in Figure 2. It can be seen that the highest

doses of sedative agents are titrated accordingly. Amean doses of both drugs are administered on day

primary aim of this project was to assess the quality4 of admission; 396 lg·kg−1·h−1 of midazolam (range

of sedation in patients receiving infusions of neuro-60–840 lg·kg−1·h−1), and 76 lg·kg−1·h−1 of morphine

muscular blocking agents and it is impractical to(range 20–100 lg·kg−1·h−1). Twenty-two assessments

discontinue such infusions prior to every episode of(27%) were performed in nine patients (32%) who

tracheal suction purely to assess sedation.were receiving oral sedation in addition to intra-

Some patients are difficult to sedate; one of ourvenous midazolam and morphine infusions and 82%

of these assessments were judged to be satisfactory. patients was a 16-month-old girl with acute myeloid

2000 Blackwell Science Ltd, Paediatric Anaesthesia, 10, 195–199

QUALITY OF SEDATION DURING MECHANICAL VENTILATION 199

leukaemia. She spent 8 days on the PICU and had Referencessix assessments, each of which was unsatisfactory

1 Shelley MP. Sedation in the ITU. Care Crit Ill 1998; 14: 85–88.(four assessments with scores of 3 on the sedation

2 Parker MM, Schubert W, Shelhamer JH et al. Perceptions of ascale, and two assessments with scores of 2; all with critically ill patient experiencing therapeutic paralysis in an

ICU. Crit Care Med 1984; 12: 69–71.a desired level of 4 on the scale). This child received3 O’Sullivan G, Park GR. The assessment of sedation in criticallymean doses of 240 lg·kg−1·h−1 of midazolam, and

ill patients. J Clin Intens Care 1990; 1: 116–122.40 lg·kg−1·h−1 of morphine in addition to daily doses 4 Ratcliffe JM. Sedation in the intensive care unit. Curr Paediatrof chloral hydrate. Whilst children with cancer 1994; 4: 106–109.

5 Matthews AJ. An audit of sedation, analgesia and muscleexperience deranged physiology with alteredrelaxation in paediatric intensive care in the United Kingdom.

handling of drugs, there is no evidence that they Paed Anaesth 1993; 3: 107–115.are more difficult to sedate than other critically ill 6 Park GR, Navapurkar V. Sedation in the critically ill patient – the

place of midazolam. Care Crit Ill 1994; 10: 5–9.children.7 Notterman DA. Sedation with intravenous midazolam in theThis project investigates only a limited aspect of

pediatric intensive care unit. Clin Pediatr 1997; 36: 449–454.the sedation of critically ill children. The children 8 Hartwig S, Roth B, Theisohn M. Clinical experience with

continuous intravenous sedation using midazolam andstudied were ventilated for relatively short periods,fentanyl in the pediatric intensive care unit. Eur J Pediatr 1991;and were from a general PICU population. Also,150: 784–788.

we excluded patients admitted in status epilepticus,9 Ramsay MAE, Savage TM, Simpson BRJ et al. Controlled

which is a common reason for admission to a PICU, sedation with alphaxalone–alphadolone. Br Med J 1974; 2:

656–659.since such children frequently receive midazolam for10 Ambuel B, Hamlett KW, Marx CM et al. Assessing distress in

its anticonvulsant effects, following a different dosingpediatric intensive care environments. The COMFORT Scale. J

regime than that used for sedation alone. Pediatr Psychol 1992; 17: 95–109.

11 Marx CM, Smith PG, Lowrie LH et al. Optimal sedation ofIn conclusion, we have demonstrated that amechanically ventilated pediatric critical care patients. Critstandard regime of midazolam and morphineCare Med 1994; 22: 163–170.

infusions, with additional oral sedation using chloral 12 Shapiro BA, Warren J, Egol AB et al. Practice parameters for

hydrate and antihistamines given as required, can sustained neuromuscular blockade in the adult critically ill: an

executive summary. Crit Care Med 1995; 23: 1601–1605.provide a high proportion of satisfactory assessments13 Lacomis D, Giuliani MJ, Van Cott A et al. Acute myopathy of

of sedation on a PICU. This high proportion ofintensive care: clinical, electromyographic, and pathological

satisfactory assessments can also be achieved in aspects. Ann Neurol 1996; 40: 645–654.

14 Nates JL, Cooper DJ, Day B et al. Acute weakness syndromespatients receiving continuous infusions of neuro-in critically ill patients – a reappraisal. Anaesth Intens Care 1997;muscular blocking agents.25: 502–513.

15 Parkinson L, Hughes J, Gill A et al. A randomized controlled

trial of sedation in the critically ill. Paed Anaesth 1997; 7: 405–410.Acknowledgements

We are grateful to Jane Credland for her help in

supporting this project and to Dr Keith Girling for

the use of the TOF-Guard. Accepted 29 July 1999

2000 Blackwell Science Ltd, Paediatric Anaesthesia, 10, 195–199