European Journal of Cardiovascular Medicine

Spinal anaesthesia is a simple, safe and reliable method for surgery of the lower body that provides profound sensory and motor block by a single use of spinal needle to administer local anaesthetics into the subarachnoid space.1 The main reasons for rejecting neuraxial blocks are fear of needle, backache as well as anticipated immediate pain associated with lumbar puncture.2 Relieving the lumbar puncture pain not only increases the patient’s satisfaction and comfort, but also let the anaesthetist apply spinal puncture fast and easily.3

Lignocaine 2% solution is routinely used for infiltration of skin and subcutaneous tissues before lumbar puncture to reduce needle prick pain. Infiltration of local anaesthetics requires needle insertion which may itself cause acute pain and discomfort to the patient, may cause masking of anatomical landmarks which are used to identify the lumbar spaces and risks of accidental intravascular administrations.4

Eutectic mixture of local anaesthetics (EMLA) is an effective topical anaesthetic mixture containing lignocaine and prilocaine. EMLA cream provides a non-invasive analgesia and has been effectively used in many studies to reduce needle prick pain.5,6 Despite its well documented efficacy for the relief of pain associated with cutaneous procedures that involve needle insertion, it has been rarely used in patients undergoing lumbar puncture.

Thus the present study was conducted to find out the efficacy of topical EMLA cream in comparison to the standard infiltration technique in reducing pain of needle insertion during lumbar subarachnoid block and have better patient satisfaction level.

This prospective, single blinded, randomized controlled study was conducted in the Department of Anaesthesiology and Critical Care, Pt. B. D. Sharma PGIMS, Rohtak after obtaining approval from Institutional Ethical Committee from September 2021- August 2022. Patients aged 18-60 years, of either sex undergoing elective lower abdominal, pelvic and lower limb surgeries belonging to ASA grade I and II were selected. Patients with known hypersensitivity to EMLA cream or any other local anaesthetics, pregnant and lactating patients, patients with methaemoglobinaemia or on drugs that may cause methaemoglobinaemia, psychiatric disorders and those requiring more than 3 attempts at lumbar puncture were excluded.

Sample Size:

Massoth et al (2017) reported a mean difference of 0.29±0.4 minutes in VAS scores between prilocaine infiltration and EMLA.1 Assuming these as references values, the minimum required sample size at power of 80% and type 1 error of 5%, number of participants required in each group were 30.

Patient preparation

Pre-operatively, a detailed clinical history regarding the disease, co-morbidities, drugs, allergies was taken. General physical as well as systemic examination was carried out. Routine investigations include complete haemogram, kidney function tests, coagulation profile, viral markers, ECG, chest x-ray, urine analysis, blood sugar, and other specific tests as required for respective surgeries. The purpose and procedure of the study was explained and informed consent was obtained from all patients. Visual analogue scale (VAS 0-10) for assessment of pain was explained to each patient during preoperative evaluation.

Randomization

Using computer generated randomization number table, the patients were divided into two groups of 30 each (Figure 1):

Group1 EMLA- This group included 30 patients in whom 2.5 gms of 5% EMLA cream per 10sq.cm was applied for a minimum of 60 minutes prior to lumbar puncture and covered with an occlusive dressing (Figure 2). After the prescribed time of application of EMLA cream, the occlusive dressing was removed. The area was then wiped dry with gauze and observed for signs of any local reaction.

Group 2 Lignocaine - This group included 30 patients in whom skin and deeper structures were infiltrated with 2ml of 2% lignocaine just prior to lumbar puncture.

Anaesthesia Technique

Patients were shifted to operation theatre after obtaining consent to participate in the study, for surgery and anaesthesia. All routine monitors were attached (NIBP, SPO2, ECG) and baseline vitals were recorded. Intravenous line secured with 18G IV cannula and IV infusion started. Patients were seated upright, lower back cleaned and draped. L3-L4 intervertebral space identified and Group-E will directly go for lumbar puncture, Group-L will receive 2ml of 2% lignocaine infiltration before lumbar puncture. Under all aseptic

and antiseptic precautions, lumbar puncture was done with a 25 gauge Quincke‘s spinal needle. After giving the subarachnoid block patients were laid supine and pain scores were noted by the candidate who is blinded about the analgesic procedure. Heart rate, SpO2 and blood pressure were recorded again soon after the subarachnoid block. The following observations were made by the candidate.

Observations

1.       Vitals monitoring- Heart rate, mean arterial pressure were recorded before and during the procedure for haemodynamic stress response to pain.

2.       Number of attempts- No. of chances taken for Lumbar puncture (i.e. appearance for CSF at the hub of LP needle )

3.       Pain score was graded as shown below:

·         Visual analogue scale13 - the VAS score on the scale of 0-10 was assessed immediately when the patient is laid supine after the subarachnoid block a 0 - no pain 10 -worst pain imaginable.

·         Using the 4-point scale14 on the scale of 0-3 as shown below

0              – no response

1              - mild facial grimace

2              - verbal response

3              - movement of the back

This pain score was graded by the candidate who is blinded with respect to EMLA application or lignocaine infiltration during to lumbar puncture.

4.       Patient’s satisfaction with the analgesic procedure was assessed immediately after the subarachnoid block when the patients were laid supine as excellent, good, satisfactory or poor.

5.       Local skin reactions like pallor, erythema, edema, pruritus, burning sensation, cold feeling, tingling etc were recorded and managed accordingly.

Statistical analysis

The data was coded and entered into Microsoft Excel spreadsheet. Analysis was done using SPSS version 20 (IBM SPSS Statistics Inc., Chicago, Illinois, USA) Windows software program. Descriptive statistics included computation of percentages, means and standard deviations. The unpaired t test (for quantitative data to compare two independent observations) was applied. The chi square test was used for quantitative data comparison of all clinical indicators. Level of significance was set at P≤0.05.

Demographic characteristics were comparable between the two groups (Table 1). The heart rate and mean arterial pressure values before and after lumbar subarachnoid block were statistically similar between the two groups (p>0.05). Mean heart rate of patients in Group E were 77.40±10.52 per minute (pre-lumbar puncture) and 78.70±9.897 per minute (post lumbar puncture) while in Group L were 77.87±11.184 per minute (pre-lumbar puncture) and 78.47± 10.197 per minute (post lumbar puncture) (Table 2). The mean arterial pressures in the two groups before subarachnoid block (EMLA=96.43±8.780, Lignocaine=94.50±10.352; p=0. 43) and after subarachnoid block (EMLA =96.03±8.568, Lignocaine=95.27±11.203; p=0.76) were comparable with no statistical difference between the two groups (p>0.05) (Table 3). The number of attempts for subarachnoid block were comparable between the two groups (p>0.05) (Table 4). The VAS score was 0 in 10% patients of EMLA group while in no patient in Lignocaine group. VAS score of 1 was noted in 26.7% patients of EMLA group while in 13.3% patients of Lignocaine group. VAS score of 2 was observed in 26.7% patients of EMLA group while in 23.3% patients of Lignocaine group. VAS score of 3 was noted in 30% patients of EMLA group while in 40% of Lignocaine group. VAS score of 4 was noted in 6.7% patients of EMLA group while in 23.3% patients of Lignocaine group. The VAS score in EMLA group appears to be lower in the present study but statistically VAS scores in both groups were comparable with no significant difference between the two groups (p=0.1) (Table 5). There was no response to needle insertion in 33.3% of patients in both EMLA and Lignocaine groups, Facial grimace was observed in 63.3% patients of EMLA group while in 66.7% of Lignocaine group, Verbal response was noted in 3.3% patients of EMLA group while no patient in Lignocaine group. There was no movement of back during spinal needle insertion in any of the groups. The 4-point pain scale was comparable with no statistical difference between the two groups (p=0.59) (Table 6). There was a significant difference in patient satisfaction score in the two groups (p=0.03) (Figure 3). The procedure was rated as: excellent by 30% patients in EMLA group as compared to 10% in lignocaine group; good in 56.7% patients in EMLA and 86.7% in lignocaine group; satisfactory in 13.3% patients in EMLA and 3.3% in lignocaine group. There was no pallor, erythema, edema, pruritus, cold feeling, tingling sensation in the groups. The local skin reaction in both the groups was comparable with no statistical difference amongst the two groups (p>0.05)

Table 1: Demographic parameters

Table 2: Comparison of heart rate between the groups

Table 3: Comparison of Mean Arterial Pressure in the two groups.

Table 4: Number of attempts in the two groups.

                       P value=0.11

Table 5: Comparison of VAS

       P value=0.1

Table 6: Comparison of 4 Point Pain Scale in two groups

                                       P value=0.59

Spinal anaesthesia is a simple, fast, and reliable method for surgery of the lower body. Relieving the lumbar puncture pain not only increases the patient’s satisfaction and comfort, but also let the anaesthetist perform spinal puncture fast and easily.3 Local skin infiltration of 2% lignocaine is a standard procedure which is usually used prior to lumbar puncture. It is invasive and itself leads to fear and anxiety in patients before application and is also associated with pain during the procedure. EMLA cream provides surface analgesia, hence the fear, anxiety and pain of analgesic infiltration is prevented. The mixture is termed eutectic as it has a melting point lower than its individual components. The mixture is liquid at room temperature while the individual components are crystalline substances. EMLA is used for relieving the pain caused during venous and intra-arterial cannula insertions in paediatrics and adult patients, excision of cutaneous lesions, radiofrequency ablation of warts, fine-needle aspiration of thyroid nodules, minor surgical procedures such as during perineal repair after childbirth, for pain control during shockwave lithotripsy, humeral block placement in non-sedated patients, peribulbar injection, mammography, transrectal biopsy of prostate, hysterosalpingography, IUD insertions, dental procedures, epidural injections and lumbar punctures.5,6 Disadvantage of EMLA cream is, it is more expensive and need at least one hour application time which is not suitable during emergency. Despite its well documented efficacy for the relief of pain associated with cutaneous procedures that involve needle insertion, it has been rarely used in patients undergoing lumbar puncture.

The present study was conducted in 60 patients aged 18-60 years, of either sex, undergoing elective lower abdominal, pelvic and lower limb surgeries, belonging to ASA grade I and grade II after obtaining approval from Institutional Ethical. In our study, we followed the standard practice and all patients were subjected to detailed clinical history and examination in our institute. The study included only those patients who fulfilled the inclusion criteria.

Hemodynamic parameters

The mean heart rates pre-lumbar puncture (EMLA:77.40±10.52; Lignocaine: 77.87±11.84; p=0.86) and post lumbar puncture (EMLA:87.70±9.897; Lignocaine: 78.47±10.197; p=0.92) were comparable between the two groups (p>0.05). This is similar to the study conducted by Firdaus et al where there was no significant difference in heart rate values in both groups (p=1.483 pre-lumbar; p=0.131 post lumbar). The mean heart rate during needle insertion was significantly reduced in EMLA group as compared to placebo in the study conducted by Kaur et al (EMLA:159.3±2.3; Placebo: 175.2±2.7; p<0.001).10 This is different from our study in which the mean heart rate was comparable in both groups because we used lignocaine infiltration instead of a placebo. The mean arterial pressure in the two groups before subarachnoid block (EMLA:96.43±8.780; Lignocaine:94.50±10.352; p=0.43) and after subarachnoid block (EMLA:96.03±8.568; Lignocaine:95.27±11.203; p=0.76) were comparable with no statistical difference between the two groups (p>0.05). In the study conducted by Firdaus et al, there was no significant difference in mean arterial pressure in the two groups before (p=0.996) and after (p=0.629) lumbar puncture which was similar to our study.11

Number of attempts

Successful lumbar puncture in first attempt was EMLA:93.4%; Lignocaine:86.7%. Second attempt in EMLA:6.6%; Lignocaine13.3%; p=0.31. The number of attempts for subarachnoid block was comparable with no statistical difference between the two groups (p>0.05).

This was similar to study conducted by Sharma et al in which all spinal needle insertions were successfully completed in one or two attempts with no significant difference in the number of attempts between the two groups (p>0.05).6 The of number of attempts for successful lumbar puncture in the study conducted by Massoth et al was comparable between the two groups (EMLA:1.41±0.75; Prilocaine:1.52±0.85, p=0.88).1

Pain scores

Visual Analogue Score

The VAS score in EMLA group appears to be lower in the present study but statistically VAS scores in both groups were comparable with no significant difference amongst the two groups (p=0.1). This may indicate either a greater anaesthetic depth or little pain from deeper tissues during insertion of spinal needle. This was similar to the study conducted by Firdaus et al where the NPRS scores were (0-3) in EMLA and (0-4) in Vapocoolant group with no significant statistical difference between the two groups, (p=1.0). In the study conducted by Massoth et al, there was no significant difference between the VAS scores between the two groups, but there was a trend towards lower VAS scores in EMLA as

compared to Prilocaine group (EMLA:1.06 ±1.33; Prilocaine:1.35±0.8; p>0.05) similar to our study.1 In the study conducted by Sharma et al (1996), mean pain scores were significantly lower in the EMLA group than in the lignocaine group (EMLA:1.5±1.3; Lignocaine: 3.52±2; p<0.001) which may be due to study subjects comprising only females as compared to majority males in our study since female tend to tolerate pain of needle insertion lesser than male and tend to give higher pain score in response to same painful stimulus.6,15 In the study conducted by Kaur et al, EMLA cream significantly decrease the pain response as compared with the placebo as shown by lower mean heart rate (EMLA:153±2.3; placebo:175±2.7; p<0.001) and a lower mean total behavioral score at insertion and withdrawal of needle (EMLA:4.0±0.3; placebo:5.0±0.0; p=0.004).10

4-Point Pain Scale

There was no response to needle insertion in 33.3% of patients in both EMLA and Lignocaine groups, facial grimace in EMLA: 63.3%; Lignocaine:66.7% , verbal response in EMLA:3.3%; Lignocaine:0.0%. There was no movement of back during spinal needle insertion in any of the groups. The 4-point pain scale in both the groups was comparable with no statistical difference between the two groups (p=0.59). Firdaus et al conducted a study comparing the analgesic efficacy of EMLA cream with Vapocoolant spray in 94 patients where there was no movement‖ of back in EMLA:46 (97.9%); Vapocoolant: 46 (97.9%) patients. There was one movement of back in each group (2.1%) with no significant statistical difference between the two (p=1.00) which is similar to our study.11

Patient Satisfaction Score

There was a significant statistical difference in patients’ satisfaction score in the two groups (p=0.03). 30% of people in EMLA group rated the procedure as excellent as compared to 10 % in lignocaine group.  In the study conducted by Sharma et al, the number of patients satisfied with the method of analgesia was significantly higher in the EMLA than in the lignocaine group (EMLA:17/19 i.e. 90%; Lignocaine:12/22 i.e. 55%; p< 0.05).6

Local Skin Reactions

There was no pallor, erythema, edema, pruritus, cold feeling, tingling sensation in the groups. The local skin reaction in both the groups was comparable with no statistical difference amongst the two groups (p>0.05) which was similar to the study conducted by Firdaus et al and Kaur et al where there was no allergy or other reactions observed in any of the two groups.10,11 This is in contrast to the study conducted by Sharma et al comparing the efficacy of EMLA cream with that of infiltration with lignocaine in relieving the pain associated with administration of spinal anesthesia in forty one women undergoing postpartum tubal ligation at Parkland Memorial Hospital and the Obstetrics Division, Dallas, Texas where they observed localized skin pallor in 80% of patients in EMLA group.6 This dissimilarity in local reaction may be due to all participants being females from a different race as compared to majority being Indian males in our study.

Limitations

It was a single centre study with small sample size. Multicentric studies with larger number of patients should be conducted.

EMLA cream is an effective alternative to lignocaine infiltration for analgesia during administration of spinal anaesthesia when using a 25G spinal needle. Application of EMLA cream for at least 60 minutes prior to spinal needle insertion is adequate to provide good analgesia during needle insertion. We recommend the use of EMLA cream in patients who are particularly concerned about pain during spinal anaesthesia.

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