Anaesthesia, 1991, Volume 46, pages 780-783 Comparison of two techniques for sedation in dental surgery

J.A. Church, Senior Registrar, Department of Anaesthesia, Western Infirmary, Dumbarton Road, Glasgow, GI I 6NT, J.S.S. Pollock, Senior Registrar, Victoria Infirmary, Langside, Glasgow, G42 9TY, D.M. Still, Department of Oral Surgery, Glasgow Dental Hospital and School, 378 Sauchiehall Street, Glasgow, G2 352, G.D. Parbrook, Senior Lecturer, University Department of Anaesthesia, Royal Infirmary, 8-1 6 Alexandra Parade, Glasgow, G31 2ER.

Summary Forty-eight patients were randomised to receive sedation for outpatient dental surgery with midazolam. Sedation was given using the Verrill technique (24 patients) and the Glasgow Dental Hospital technique (24 patients). The diferences in recovery and patient acceptability were assessed. There was no statistical diference in mean recovery times between the two groups. Memory function was examined using the Warrington memory test. Fewer patients in the Verrill group recalled the injection of local anaesthetic but they demonstrated memory defects 4 hours after sedation for words and 3 hours for faces. The Glasgow Dental Hospital group demonstrated memory defects for words up to 2 hours following sedation, but not for faces at any time. Thirty-eight patients would have dental surgery again with similar sedation. The dental surgeon found conditions for surgery inadequate in two patients. In view of the shorter duration of amnesia we recommend the Glasgow Dental Hospital technique.

Key words Hypnotics, benzodiazepines; midazolam. Surgery; dental.

Midazolam has proved to be a reliable and safe method for intravenous sedation in dental outpatients.' There are two different techniques of midazolam sedation currently in use. The Verrill technique, where the end-point is ptosis' and the technique used in the Glasgow Dental Hospital (GDH) where sedation is considered satisfactory when the patient becomes less responsive on direct q~estioning.~ In their study, Skelly and colleagues' used the Verrill technique and showed a significant memory impairment at 5 hours with midazolam given at a mean dose of 12.73 mg (range 5-18 mg). They concluded that instructions should warn of continuing impairment. A recent study by Ho and colleagues4comparing midazolam and isoflurane in dental sedation has also shown a significant impairment of memory one hour postoperatively in the midazolam group despite the use of a smaller dose of midazolam, 5.5 mg (range 3-10 mg). The aim of this study was to compare the two different techniques of midazolam sedation to determine any difference in amnesia, in the rate of recovery, or in the patients' opinions. Patients and methods

Approval was granted by the local Ethics Committee. We studied 48 patients, aged 16-60 years, who required minor dental surgery under sedation. Patients were excluded if they were not ASA 1 or 2, if they took any psychotropic medication, or were pregnant. The study was observer and patient blind. Patients were allocated randomly to receive sedation by the GDH or Verrill techniques. Informed consent was obtained from all patients. The memory test developed by Warrington was used as described in the previous study by Ho and colleagues4 but with the addition of two further sets each of 25 words and faces. Patients were tested before sedation to obtain a

Accepted 11 December 1990.

baseline score, and then 2, 3 and 4 hours following administration of midazolam. The order of the sets of memory tests was randomised to prevent any bias. Anxiety was assessed by the Corah dental anxiety scale5 and a visual analogue scale (VAS). Systolic arterial pressure, heart rate and oxygen saturation (Sao,) were measured during the procedure using an automated system consisting of an Ohmeda Biox 3700 pulse oximeter and a Critikon Dinamap i 846 noninvasive arterial pressure monitor. These were interfaced to an Atari 1040 ST microcomputor programmed to store data on magnetic disc at 2-minute intervals. In the dental chair a 23-gauge cannula was inserted in the back of the hand. The Verrill group received 2 mg midazolam then intermittent doses of 1 mg/minute up to a maximum of 10 mg. The end-point was taken as the degree of ptosis demonstrated when the eyelid was halfway across the pupil, unless the patient previously showed excessive drowsiness, slurred speech or nystagmus. The GDH group received 2 mg midazolam, then intermittent doses of 1 mg/minute up to 5 mg, then 0.5 mg/minute up to 10 mg. The end-point was judged by the patient's loss of interest in maintaining conversation, with a tendency to monosyllabic replies rather than extended sentences. The patient no longer directed his gaze to the speaker and tended to forget the trend of conversation. The duration of blinking lengthened and there was a loss of tone in the arm. The anaesthetist who sedated all the patients (G.D.P.) was the only investigator aware which method of sedation was used in each case, and he was not involved in testing recovery from sedation or testing memory function. The dental surgeon injected local anaesthetic, lignocaine 2% with adrenaline. Recovery tests, as in the previous study,4 were performed 10 minutes after the end of the procedure, and every subsequent 5 minutes until the patients were capable of walking unaided in a straight line. The patients were

Forum discharged 4 hours after surgery with written and verbal postoperative instructions. They returned a questionnaire when they visited the dental surgeon one week later.

Table 2. Systolic arterial pressure (mmHg).

Before surgery After surgery

Results

Forty-eight patients were studied, seven males and 17 females in the Verrill group, and two males and 22 females in the GDH group. Forty patients had extraction of teeth, one an exploration, two curettage, four apicectomies, and one had excision of a lesion of the hard palate. There was no statistical difference in the age or weight of the two groups (Table 1). Corah dental anxiety scores were similar in both groups. Postoperatively there was a significant decrease in VAS for anxiety in both groups, but there was no significant difference between the groups. The patient estimated the duration of surgery to be less than the true value. Durations of surgery were similar, as were the times to injection of local anaesthetic. The mean dose of midazolam administered in the Verrill group was 8.18 mg (range 5-10 mg) and 5.4 mg (range 3-10 mg) in the GDH group, and the difference of the means did not reach full significance (p < 0.1, Mann-Whitney U test). Ptosis, as in the Verrill technique with the eyelids half over the pupil, was not seen in any patient in the GDH group. Full ptosis was only achieved in the Verrill group in nine out of the 24 patients; excess sedation with diplopia and drowsiness was seen. The mean recovery time in the Verrill group was 21.5 (range 10-35) minutes. This was not statistically significant from the mean recovery times in the GDH group, 16.9 minutes (range 10-25 minutes), (Table 1). There was no significant difference between the lowest Sao, recorded during the procedure in the two groups. In the Verrill group, the lowest value recorded was 89%, (mean 93.8, range 89-99), and in the GDH group the lowest value was 91% (mean 94.6, range 91-98). There was a significant increase from baseline values in systolic arterial blood pressure at the end of the procedure, (p < O.OOOl), but no statistical difference between the two groups. In the Verrill group, the increase in heart rate was statistically significant, (p < 0.05), but there was no significant change in the GDH group (Table 2). The dental surgeon rated surgical conditions as satisfactory in 46 patients. One patient became very weepy and not fully cooperative and sedation was judged inadequate. The technique was a failure in another patient; he remained anxious and uncooperative during surgery. Both patients were in the Verrill group. The patients were questioned at the end of surgery to assess their opinion of the sedation. Significantly more patients recalled the injection of local anaesthetic in the Table 1. Demographic data and operative details, (mean (SD)).

Verrill group

GDH group

116.04 (15.23) 131.75 (18.43)

109.46 (1 1.08) 127.67 (16.54)

Heart rate Before surgery After surgery

72 (12) 80 (13.4)

Table 3. Patients’ assessment of sedation.

Number of patients Estimation of mean duration of the procedure; minutes

24 23.67 (5.6) 64.73 (14.42) 11.08 (0.76)

24 27.08 (1 1.93) 62.98 (10.52) 11.38 (0.72)

Opion of LA (if remembered) Acceptable Unpleasant Painful

5.36 (2.34) 0.92 (0.76) 32.96 (12.16)

5.10 (2.60) 1.44 (1.70) 30.21 (13.83)

8.58 (0.43) 21.46 (6.84) 8.19 (1.92)

6.29 (0.40) 16.88 (10.85) 5.4 (1.80)

VAS, visual analogue scale; LA, local anaesthesia.

75.79 (13.4) 77 (13.2)

GDH group compared to the Verrill group (Table 3). There was no statistical significance between groups in recall of the procedure (Table 3). In the Verrill group, six patients felt they still had some degree of anxiety during the operation, while four patients acknowledged anxiety in the GDH group. Only two patients experienced dreams. One patient in the GDH group could not recall the content of the dream. The second patient, in the Verrill group, dreamed of a previous unpleasant dental experience. This patient was judged to have been inadequately sedated by the dental surgeon. On specific questionning 7 hours after sedation she did not recall the dream. Memory Tests. The results of the memory tests are illustrated in Figure 1. There was no significant difference between groups for the baseline retention scores assessed before operation for words and faces. In the Verrill group the falls in retention scores for words were significant at 2 and 3 hours (p < 0.001 in each case; Wilcoxon signed rank test, Bonferroni correction) and also at 4 hours (p < 0.05; Wilcoxon signed rank test, Bonferroni correction). In the GDH group, the decreases in retention scores for words was only significant at 2 hours (p < 0.01, Wilcoxon signed rank, Bonferonni correction). For faces, significant falls in the retention scores were seen in the Verrill group up to 3 hours (p < 0.01 in each case; Wilcoxon rank test, Bonferroni correction). In the GDH group the decreases in the retention scores were not statistically significant. Patient Questionnaire. Eighty-nine percent (22/24) in the Verrill group and 85% (21/24) in the GDH group returned questionnaires (Table 4). There was no significant difference between the two groups. A similar incidence of side

Remembered Injections of LA Dental procedure Number of patients Age; years Weight; kg Corah dental scale Anxiety VAS; cm Before operation After operation Duration of operation; minutes Time to injection of LA Recovery time; minutes Midazolam dose; mg

78 1

Verril group

GDH group

24 22.88

24 19.88

5

15* I8

11 4

0

13 0 2

General opinion Anxious Comfortable/relaxed Dreams

6 18 1

4 20 1

Would have the same again

23

21

1

LA, local anaesthesia. *p < 0.01; Chi-squared with Yates’ correction.

Forum

782

Table 4. Postoperative side effects (number of patients).

Verrill group (n = 22)

.GDH group (n = 21)

Evening

Next day

Evening

Next day

14

8 5 6 3

15 I1 6

4 5 4 5

0

Drowsiness Lack of ability to concentrate Dizziness/unsteady Nausea Vomiting

Headache Muscle pain/stiffness Pain at site of dental procedure Pain at site of injection in the hand Sore throat Time to return to work Next day

13 8 3 2 8 6 17

6

2 9 3

14

13

2 9 1 12

4

3

3

2

5

4

6

6

Later Would have same sedation again

effects was recorded by both groups; over 50% felt drowsy, were unable to concentrate and had pain at the operation site the same day. Thirty out of the 41 patients who returned the questionnaire had not returned to work the next day. Thirty-eight patients said they would like a similar sedation technique if they required further surgery. Discussion

Sedation techniques are now commonly used in outpatient dental chair surgery. The benzodiazepine midazolam is a suitable alternative to diazepam in outpatients because of its short half-life and inactive metabolites: Its amnesic properties are well doc~mented.'.~This is important during the surgical procedure but gives some cause for concern in day case patients who may forget instructions 25

E

Verrill technique

GDH technique

20 ? 0 0 v)

% L

15

0

E E

Q,

c

10

0 W

r 5

I

0 Words

Faces

Words

Faces

Fig. 1. Mean memory score for words and faces before and after sedation. There was a significant reduction in mean scores in the Verril! group for words at 2 and 3 hours (p < 0.001) and also at 4 hours (p < 0.05). For faces the reduction in scores was significant at 2 and 3 hours (p < 0.01). There was a significant reduction in scores for words in the GDH group up to 2 hours after sedation (p < 0.05). The reduction in scores for faces in the GDH group was not significant. (Wilcoxon signed rank test, Bonferroni correction). M,0 hours; M, 2 hours; 0, 3 hours; B, 4 hours.

7

7 15 18

5

6 15 18

issued to them at the time of discharge from the dental surgery. The Warrington memory test was used by Ho and colleagues4 to assess memory function after intravenous midazolam and inhalation of isoflurane, and they found the test to be reliable and easy to use, as we did. Simple recognition of words and faces is 'patient friendly'. Memory impairment is dependent on the dose of benzodiazepine' and as a previous study' using the Verrill technique appeared to have used a higher dose than the alternative technique it seemed possible that there would be more amnesia after the use of the Verrill technique. In our study the difference in dosage between the two groups did not achieve full significance, even though in the Verrill technique the patient was titrated to a deeper degree of sedation, with marked ptosis. The lack of significance in the mean dosage was, we believed, related to the wide range of doses required in the individual patients. The deeper degree of sedation with the Verrill technique was associated with significantly greater amnesia for the local anaesthetic injections. Defects in memory, as shown by the Warrington memory tests, were seen up to 4 hours after the Verrill and 2 hours after the GDH technique. Our results are in keeping with those of Skelly and her colleagues' who also demonstrated amnesia at 5 hours after the Verrill technique, using a larger dose of midazolam. Both techniques gave comparable results apart from the differences in the memory tests. There were no significant differences in recovery times, dental surgeon or patient opinions or in the longer term side effects reported on the questionnaire. Comparable numbers of patients in each group reported willingness to be sedated in a similar manner again for dental surgery. Some patients considered sedation was an unnecessary adjunct to local anaesthesia for them personally and would therefore decline sedation again. One patient who requested a general anaesthetic before being offered sedation would still have preferred general anaesthesia when questioned at the end of the procedure. This same patient was judged inadequately sedated by the dental surgeon, and possibly came to the surgery with preconceived ideas about sedation for dental surgery. Dreaming in the dental chair while having surgery under sedation is reportedfoand may result in litigation." In this study only two patients reported dreams during the procedure. This may be related to the lower doses used in this study.

Forum In conclusion, memory defects were demonstrated for up to 4 hours after use of the Verrill technique and at 2 hours using the GDH technique. The Verrill technique also gave more amnesia for the injection of local anaesthetic, but the GDH technique may be preferred since it produces less memory defect during the hours following the surgery. In view of the memory defects with both techniques we would recommend written instructions are given to the patient before sedation and also, at discharge, to the patient's escort. We would also recommend that dentists are instructed in the use of the GDH technique by anaesthetists teaching sedation for dental surgery.

References I . SKELLY AM, BOSCOE MJ, DAWLING S , ADAMS AP. A comparison of diazepam and midazolam as sedatives for minor oral surgery. European Journal of Anaesthesiology 1984; I: 25347. 2. ONEIL R, VERRILL PJ, AELLIG WH, LAURENCEDR. Intravenous diazepam in minor oral surgery. Further studies. British Dental Journal 1970 128: 15-18.

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3. BRAIDDP. Anaesthesia for Dental Surgery. In: NIMMO WS, SMITH G, eds. Anaesthesia, Vol 1, Blackwell Scientific, 1989; 654-64. 4. Ho ETF, PARBRCOK GDP, STILLDM, PARBROOK EO. Memory function after IV midazolam or inhalation of isoflurane for sedation during dental surgery. British Journal of Anaesthesia 1990, 64:337-40. 5. CORAH NL. Development of a dental anxiety scale. Journal of Dental Research 1969; 48: 596. 6. REVES JG, FRAGENRJ, VINIK HR, GREENBLATT DJ. Midazolam: pharmacology and uses. Anesthesiology 1985; 6 2 3 10-24. 7. DUNDEE JW, WILSON DB. Amnesic action of midazolam. Anaesthesia 1980; 35: 459461. 8. BERGGRENL, ERIKSWN I, MOLLENHOLT P, WICKBOM G. Sedation for fibreoptic gastroscopy: a comparative study of midazolam and diazepam. British Journal of Anaesthesia 1983; 5 5 289-96. 9. GHONHEIM MM, HINRICKS JV. MEWALDTSP. Dose-resnonse r ----analysis of the behavioural effects of diazepam. British Journal of Anaesthesia 1970; 4 2 6W7. 10. DUNDEE JW. Unpleasant sequelae of benzodiazepine sedation. Anaesthesia 1990; 45: 336. I 1. BRAHAMS D. Medicine and the law. Lancet 1990; 335 157.

Anaesthesia, 1991, Volume 46, pages 783-785

Haemodynamic effects of propofoi in children

S. M. Short, FFARCS, Lecturer, C. S. T. Aun, FFARCS, Senior Lecturer, Department of Anaesthesia and Intensive Care, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong.

Summary

The haemodynamic efects of induction of anaesthesia with propofol in children were studied. Two hundred and sixteen children (ASA I ) were randomly allocated to receive one of six digerent doses of propofol, from 1.6 mglkg to 2.6 mglkg, in 0.2 mglkg increments. Noninvasive measurement of blood pressure showed that mean arterial pressure was reduced by approximately 15% after 1 minute, and by 30% after 5 minutes. The reduction in pulse rate over a 5-minute period was approximately 17%. These changes were similar in each group, regardless of the dose administered. The propofol was mixed with lignocaine, 0.5 mglml, and the incidence of pain on injection into a vein on the dorsum of the hand was 24%. We conclude that, within the dose range of our study, the haemodynamic disturbance after induction of anaesthesia with propofol in children is not dose related. Key words

Anaesthetics, intravenous; propofol. Anaesthesia; paediatric.

Propofol has become increasingly popular as an induction agent since its introduction in 1983. This is primarily due to rapid recovery conferred by its high plasma clearance and short half-life.' In common with many intravenous induction agents, it causes a decrease in blood pressure on induction of anaesthesia. The reduction in blood pressure with propofol is observed to be more than that with thiopentone in both adults* and ~ h i l d r e n Studies .~ in children suggest that they require a larger induction dose of propofol than adults, probably in excess of 2.5 mg/kg.3,4 However, larger doses of propofol may be associated with Accepted 29 November 1990.

pronounced haemodynamic side effect^.^ The aim of this study was to determine whether or not there was a doserelated change in haemodynamics following induction of anaesthesia with propofol in children.

Method Approval for this study, and for the use of propofol in children, was granted by the Chinese University Research Ethics Committee and informed parental consent was obtained. Two hundred and sixteen children (ASA I),

Comparison of two techniques for sedation in dental surgery.

Forty-eight patients were randomised to receive sedation of outpatient dental surgery with midazolam. Sedation was given using the Verrill technique (...
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