Intravenous anaesthetics are used widely for induction and maintenance of general anaesthesia. Various anaesthetic drugs are available such as thiopentone, propofol, etomidate etc, each of them having unique attributes that are suitable for specific applications.

Propofol is a drug of choice for induction in millions of patients every year, it is used especially for brief cases, day care surgery or when a laryngeal mask airway(LMA) is to be used, owing to its rapid onset & short duration of action, easy titration & favourable side effect profile[1]. Despite these positive attributes, about three out of five patients experience pain on injection of propofol, with one of these patients reporting severe or excruciating pain. Some patients recall the induction of anaesthesia as the most painful part of the perioperative period[2]. It is distressing and uncomfortable for the patient and should be controlled or prevented to make the induction of anaesthesia pleasant.

The international association for the study of pain defines pain as an “unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.” Perception of pain is distressing for the patient; it can be associated with haemodynamic and psychological alterations. Hence, it should be recognized early and appropriate management of pain should be done[3-4].

Strategies to reduce the incidence of pain on propofol injection include adding lignocaine, cooling or warming propofol, diluting the propofol emulsion, injection into a large vein, and pretreatment with intravenous lignocaine, ondansetron, metoclopramide, an opioid, magnesium, or thiopental with or without tourniquet; all have been tried with variable results[5].

The use of lignocaine to prevent propofol injection pain is the most extensively studied technique and is the conventional method used in clinical practice. It may act via a local anaesthetic effect on the vein and by stabilizing the kinin cascade. It is considered superior to other drugs but not effective in all situations[6].

Metoclopramide (2-methoxy-5-chloroprocainamide) primarily antiemetic and a pro-kinetic drug shares similar, structural and physicochemical properties with Lignocaine, Procaine and Procainamide and is a weak local anaesthetic in its own right. Although Metoclopramide like Morphine may alter the movement of calcium ions across the membrane to produce a generalized analgesic effect, the exact mechanism whereby it prevents local injection pain is unknown ok and colleagues suggested a direct Local Anesthetic effect on peripheral nerves. In addition to this pharmacological property, Metoclopramide has a weak general analgesic effect[7]. In this study we compare the efficacy of intravenous lignocaine with metoclopropamide as a pretreatment in reduction of pain on propofol injection.

Study population will be randomly divided into 2 groups of each, namely group N and group L by tossing a coin. Patients will receive either Metoclopropamidepre treatment 10mg in a total volume of 2 mL (n=50) or 3 mL of 2% preservative free Lignocaine (60mg) pre-treatment (n=50). All drug preparations will be done at operating room temperature (21–23°C) and the anaesthesiologist who conducts the case will be blinded to the content of the solutions.

Inclusion Criteria:

(ASA) physical status I and II, of either sex, aged between 18 and 60 years, undergoing elective surgery under general anesthesia.

Exclusion Criteria:

• Patients less than 18 years and more than 60 years
• Patients belonging to ASA grade III and IV
• Patients with difficulty in communication
• Patients who had a history of allergic response to either Propofol or Metoclopropamide and Lignocaine
• Patients who had received any analgesics, sedative drugs within 24 hrs prior to surgery
• Patients with infection on the dorsum on the hand
• Patients with systemic illness, vascular diseases
• Patients undergoing emergency surgeries

After attaching routine monitoring (ECG, non-invasive arterial pressure, and pulse oximeter), a 20-gauge cannula will be secured in a vein on the dorsum of hand and Ringer lactate (RL) will be infused at 100ml/hr. After 1 min, RL will be stopped and the arm with the IV line will be elevated for 15sec for gravity drainage of venous blood. After occluding the venous drainage using a pneumatic tourniquet (pressure inflated to 70 mm Hg) on the upper arm, the patients will be pretreated over a period of 10 sec with either of the pretreatment solutions

Table 1: Age Distribution

Majority of the patients were above 35 years of age in both groups. The mean age of Group L and Group M was 34.7±8.4 years and 36.4±10.0 respectively, the difference was not statistically significant.

Table 2: Weight distribution

.Table 3: SA grading in both the groups

Studies done on patients with ASA distribution showed ASA1 of  34% in metoclopropmide group and 32% in lignocaine group and ASA2 of 16% in metoclopropamide group and 18% in lignocaine group and was found statistically not significant.

Table 4: Degree of pain

Degree of pain, as assessed by visual analogue scale, was measured at the time of drug administration, 10 seconds and 20 seconds after drug administration. Visual rating score done at 0 second, 10 seconds and 20 seconds showed mean of (0.3±0.51),( 0.72±0.57),(0.48±0.65) respectively in metoclopropamide group and in lignocaine group at 0 second, 10seconds and 20 seconds showed the mean of (0.2±0.4),(0.64±0.6), and (0.38±0.49) respectively and the results were found to be statistically not significant. Post-operative recall of pain studied on patients after 10hrs of injection of propofol showed 6% in metoclopropamide group and 4% in lignocaine group and was stastically not significant.

Table 5: Recall of pain

Table 6: Diastolic Blood Pressure at different time intervals

Changes in diastolic pressure at baseline, 1min and 5min. The changes with time in both the groups were not significantly different

Our study is the first to compare the efficacy of metoclopropamide versus lignocaine in reducing pain on propofol injection. We compared efficacy of pain control at 3 intervals to assess intraoperative pain relief with propofol injection. In addition, we assessed post-operative recall of pain which has both clinical applicability i.e. patient comfort with anaesthesia and scientific implication i.e adding to the limited body of literature assessing post-operative pain control on propofol injection[8].

Minimizing propofol injection pain is an important clinical goal, because it may influence the patient’s perception of quality and acceptability of anaesthesia. The incidence of pain varies between 28% and 90% in adults during induction of anaesthesia[9].

A number of methods to prevent propofol injection pain have been studied which include  Non-pharmacological methods like microfiltration, double line intravenous set, warming the propofol to 37°C, cooling of propofol to 4°C, and reducing the pH of propofol injectate. Pharmacological methods like pre-treatment with lignocaine, ondansetron, ketorolac, nafamostat, ketamine or topical nitroglycerine application with propofol and diluting propofol with 5% dextrose or 10% intralipid[10].

But none of the methods have been successful in eliminating the pain associated with propofol injection. Lignocaine is the most common method used in clinical practice to reduce pain on propofol injection. Lignocaine acts as a stabilizer for the kinin cascade. Scott et al.[11] proposed that lignocaine mixed with propofol decreased its pH, resulting in a lower concentration of propofol in the aqueous phase and therefore less pain. When lignocaine is used as pretreatment, it is presumed to have a local anaesthetic effect on the vein. Sharon Y King et al. showed that with addition of 20mg lignocaine with propofol, incidence of severe pain reduced from 31% to only 5.6% of the study population. Leena Jalota et al. analysis showed lignocaine-propofol admixture was of similar efficacy to pretreatment with lignocaine alone. Both interventions were, however, considerably less efficacious than pretreatment with lignocaine in conjunction with venous occlusion[12-13]. A range of dose from 20 – 40 mg as pretreatment has been used effectively to prevent pain with 40mg being more effective than 20 mg when used along with venous occlusion.

We conducted this study to evaluate a superior modality of pain relief on propofol injection. The analgesic effect of a small dose of metoclopropamide has been reported in a range of clinical situations. The role of metoclopropamide as pretreatment for propofol anaesthesia is under evaluation when either used alone or as an admixture with lignocaine[14].

We undertook the current study to define the role of nitrolycerine alone in relieving pain caused by intravenous propofol.  A brief overview of study conduct and results are presented below for ease of comparison

In the favour of our hypothesis we found that lignocaine 60 mg intravenous pretreatment and metoclopropamide 10mg intravenous pretreatment are equally efficacious in reducing the pain on propofol injection. We also assessed the postoperative recall of pain in both the study drug groups and found 6% in metoclopropamide group and 4% in lignocaine group recalled the pain and no significant difference in both groups. We also found no significant heamodynamic and cardiovascular changes produced by both the drugs, hence we conclude both metoclopropamide 10mg and lignocaine 60mg intravenous pretreatment is equally efficacious in reducing pain on propofol injection with lignocaine has better pain control than metoclopropamide

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