A Comparison Of Intravenous Magnesium Sulphate And Lidocaine For The Prevention Of Pain On Injection Of Propofol.

 

KN Litchfield*, J Prinzlin, A Hay*, M Watson, A Lal
Dept of Anaesthesia, University of Glasgow*, Golden Jubilee National Hospital, Glasgow, UK

 

Background and Goals:

Approximately 70% of patients will report pain on injection of propofol1. A recent systematic review identified lidocaine 40mg with a venous tourniquet applied for at least 30 seconds as the most efficacious technique in preventing the subsequent pain on injection of propofol2. Latterly magnesium sulphate (MgSO4) has also been shown to be effective compared to placebo3. Is MgSO4 as effective as lidocaine in preventing pain on injection of propofol?

 

Material and Methods:

Prospective randomised controlled double blind trial. With local ethics approval 120 ASA 1 or 2 patients undergoing GA for elective surgery were recruited. Group L= lidocaine 40mg and venous tourniquet for 30 sec, Group M= MgSO4 2.5mmols, Group S= 5mls Saline (placebo). Pain on injection of study drug and propofol were measured with modified verbal rating score (0-3). Data were analysed with Students t-test for parametric and Kruskal-Wallis ANOVA on ranks and Mann Whitney rank sum test for non-parametric data.

 

Results:

Groups were similar in age, weight, and sex.

 

Table 1. Distribution of pain scores after injection of propofol.

Pain Score

0

N (%)

1

N (%)

2

N (%)

3

N (%)

Group S (n=40)

17 (42.5)

15 (37.5)

7 (17.5)

1 (2.5)

Group L* (n=40)

24 (60)

6 (15)

7 (17.5)

3 (7.5)

Group M† (n=40)

33 (82.5)

5 (12.5)

2 (5)

0 (0)

*The difference in pain scores between Group L and Group S did not reach statistical significance. †The distribution of pain scores was significantly different between Group M and Group S (p<0.05) and Group M and Group L (p<0.05).

 

Pain scores on injection of study drugs showed no significant difference between the three groups. 10 patients in Group M experienced pain on injection of the study drug. If you consider the pain on injection of study drug and pain on injection of propofol combined, for Group M and Group L, the difference seen in Table 1 is no longer significant (p=0.84).

 

Conclusions:

 In this study MgSO4 2.5mmols given before IV propofol is more effective than either lidocaine or saline in preventing pain on injection of propofol. However pain on injection of the MgSO4 itself may limit its clinical usefulness.

 

References:

1.             Tan CH, Onsiong MK. Anaesthesia 1998; 53:468-476.

2.             Picard P, Tramer MR. Anesth Analg 2000; 09:963-969.

3.             Memis D, Turan A, Maramanlioglu B et al. Anesth Analg 2002; 95:606-608.