A comparison of pain on intravenous injection between two preparations of propofol

Propofol is frequently used for sedation, induction, and maintenance of anesthesia. It is, however, associated with pain on injection. Propofol-Lipuro has an oil phase that allows a larger proportion of propofol to be dissolved in it and, thereby, apparently reduces pain. However, studies investigating this have had methodological limitations. We devised a randomized, double-blind, crossover study comparing pain on injection between two preparations of propofol, Diprivan and Propofol-Lipuro, in subanesthetic doses. Sixty healthy patients received the drugs in random order via the same injection site separated by 10 min and a 0.9% saline flush. Pain was assessed using a verbal rating score (VRS) during and at 1-min time points after injection. Differences in VRS between the two propofol preparations at different time points in each patient were analyzed. In patients who were given Diprivan first followed by Propofol-Lipuro (group D-P), pain was significantly reduced with Propofol-Lipuro compared with Diprivan during initial injection (median difference in VRS = 2 [interquartile range 0-2], P = 0.002) and at 1 min (3 [0-4], P < 0.001). In patients who were given Propofol-Lipuro first followed by Diprivan (group P-D), no significant differences in VRS were shown. Propofol-Lipuro is associated with reduced injection pain compared with Diprivan and also seems to attenuate subsequent injection pain of Diprivan when administered first. The mechanism is unknown, but may be related to a reduction in the concentration of propofol in the aqueous phase.     

Lidocaine is more efficient than the choice of propofol formulations to reduce incidence of pain on induction

BACKGROUND AND OBJECTIVE: Propofol is associated with pain on injection. It is common practice to premix lidocaine with propofol prior to injection. Lipuro propofol, a propofol emulsified in medium- and long-chain triglycerides, has been shown to reduce the intensity of injection pain compared to Diprivan, although a number of studies report no reduction in overall incidence of pain. METHODS: We conducted this randomized double-blind trial to determine the extent of further pain reduction by adding lidocaine to Lipuro propofol. A total of 328 ASA I-III patients were randomized to one of four groups to receive Diprivan propofol (Group DP), Lipuro propofol (Group LP), Diprivan with lidocaine (Group DL) and Lipuro propofol with lidocaine (Group LL). The drug mixture was administered at a constant rate of 400 mL h(-1) via a 20-G cannula into a dorsal hand vein. Pain was assessed during induction and upon patient recovery, using a 10-point visual analogue scale. RESULTS: Both the incidence and severity of pain were found to be significantly lower with addition of lidocaine to Lipuro propofol (P < 0.0002) compared to Lipuro alone, Diprivan with or without the addition of lidocaine. CONCLUSION: Lidocaine added to Lipuro propofol makes induction of anaesthesia less painful compared to Lipuro propofol alone or Diprivan with lidocaine.     

Preventing pain during injection of propofol: effects of a new emulsion with lidocaine addition

BACKGROUND AND OBJECTIVE: Previous studies found that lidocaine addition to propofol long-chain triglyceride was associated with a lower incidence of injection pain than medium-chain triglyceride/long-chain triglyceride formulation, but the incidence was still high (31-40%). Our study investigated whether the incidence of injection pain could be further reduced by the addition of lidocaine (10 mg, 20:1) to propofol medium-chain triglyceride/long-chain triglyceride. METHODS: In a randomized double-blind controlled trial 464 patients scheduled to undergo regional anaesthesia were assigned to receive one of the following four options: propofol medium-chain triglyceride/long-chain triglyceride + lidocaine, propofol long-chain triglyceride + lidocaine, propofol medium-chain triglyceride/long-chain triglyceride or propofol long-chain triglyceride. Propofol was injected to reach grade 3 of the Observer's Assessment of Alertness/Sedation scale. RESULTS: Incidence of injection pain was 18% in the propofol medium-chain triglyceride/long-chain triglyceride + lidocaine group, 31% in the propofol long-chain triglyceride + lidocaine group, 47% in the propofol medium-chain triglyceride/long-chain triglyceride group and 60% in the long-chain triglyceride group. Propofol medium-chain triglyceride/long-chain triglyceride + lidocaine was associated with a statistically significant reduced incidence of injection pain compared with propofol long-chain triglyceride +lidocaine (P =0.0249, number needed to treat =7.7). CONCLUSIONS: Premixing propofol medium-chain triglyceride/long-chain triglyceride with lidocaine is one of the most effective measures currently available to reduce the incidence of injection pain in sedated patients during regional anaesthesia.     

Comparison of a lower-lipid propofol emulsion with the standard emulsion for sedation during monitored anesthesia care

BACKGROUND: The currently used emulsion formulations of 1% propofol contain 10% soybean oil. However, a new emulsion of 1% propofol (Ampofol) containing 50% less lipid has recently become available for clinical investigation. This study was designed to compare the pharmacodynamic properties of Ampofol with those of a standard formulation (Diprivan) when administered for intraoperative sedation. METHODS: Sixty healthy outpatients undergoing minor operations with local anesthesia were randomly assigned to receive either Ampofol (n = 31) or Diprivan (n = 29) for intravenous sedation. The sedation was initiated with an intravenous loading dose of propofol, 0.75 mg/kg, followed by an initial infusion rate of 50 microg x kg(-1) x min(-1) to achieve an Observer's Assessment of Alertness/Sedation score of 3. The targeted level of sedation was maintained with a variable-rate propofol infusion during the operation. The onset times to achieving a sedation score of 3, the severity of pain on injection of the loading dose, intraoperative hemodynamic variables, and electroencephalographic Bispectral Index values were recorded. In addition, recovery times, postoperative pain and nausea, and patient satisfaction with the sedative medication were assessed. RESULTS: There were no significant differences between Ampofol and Diprivan with respect to onset times, dosage requirements, Bispectral Index values, hemodynamic variables, recovery times, or patient satisfaction scores. The incidence of moderate pain on injection was higher in the Ampofol group (26%vs. 7% with Diprivan; P < 0.05). CONCLUSIONS: Ampofol was equipotent to Diprivan with respect to its sedative properties during monitored anesthesia care. Although both groups received pretreatment with intravenous lidocaine, Ampofol was associated with more pain on injection.     

Effect of prior administration of cold saline on pain during propofol injection

A single-blind, randomised, controlled study was undertaken to compare the efficacy of three methods of preventing pain during injection of propofol on induction of anaesthesia. Patients were allocated randomly to receive unmodified propofol, propofol with 0.05% lignocaine, propofol at 4 degrees C and unmodified propofol preceded by 10 ml of 0.9% saline at 4 degrees C. Prior injection of cold saline reduced the incidence of pain and discomfort significantly (22%) compared with unmodified propofol (75%; p less than 0.005) and was similar to that after cold propofol (33%) and propofol with lignocaine (44%). There was no significant difference between the treatment groups.     

Reduction of pain on injection of propofol: combination of pretreatment of remifentanil and premixture of lidocaine with propofol

BACKGROUNDS AND OBJECTIVE: There is a high incidence of pain following intravenous injection of propofol, and many studies have been conducted to find a way of reducing this. The administration of lidocaine and, recently, remifentanil has also been used for this purpose, but it is only partially effective. Thus, the purpose of this study was to investigate the analgesic effect of a combination of pretreatment with remifentanil and premixture of lidocaine with propofol and to compare either treatment alone during propofol injection in dorsal hand-veins. METHODS: In a prospective, randomized, double-blinded trial, we studied 141 adult patients scheduled for elective surgery. The combination of pretreatment of remifentanil (0.35 microg kg(-1) min(-1)) and a premixture of lidocaine with propofol (mixture of propofol 1% and lidocaine 1% in a 10:1 ratio) was compared with either treatment alone in the prevention of pain on propofol injection. Pain was assessed on a four-point scale (0=none, 1=mild, 2=moderate, 3=severe) during propofol injection. Patients in Group B received remifentanil (0.35 microg kg(-1) min(-1)) 30 s before the injection of propofol. RESULTS: The reduction of pain on propofol injection was similar in both the remifentanil pretreatment and lidocaine premixture groups (62.2% vs. 62.2%). Combination therapy was associated with a higher incidence of patients without pain (91.3%) than either treatment alone (P<0.001). On analysing the injection pain scores, we found a significant reduction of the score in the remifentanil and lidocaine Group C compared with the lidocaine Group A (P<0.001) and the remifentanil Group B (P<0.001). CONCLUSIONS: The combination of pretreatment of remifentanil and premixture of lidocaine with propofol was more effective in reducing the incidence of pain on injection of propofol than either treatment alone.     

Pretreatment with ketorolac and venous occlusion to reduce pain on injection of propofol

We performed a randomised, double-blind, prospective trial to discover whether intravenous ketorolac 10 mg made up to 2 ml with saline, with or without venous occlusion for 2 min, reduces the pain on injection of propofol. In 90 patients, pain scores were obtained during injection of propofol following pretreatment of the vein with saline, ketorolac or ketorolac with venous occlusion. Pain on injection of ketorolac was more common than with saline (p = 0.02). The incidence of severe pain following propofol was reduced by ketorolac with venous occlusion (p = 0.019) compared with saline or ketorolac without venous occlusion. There was no difference in venous sequelae at 7 days postoperatively between the groups. Our results suggest that pain on injection of propofol may be related to release of local kininogens and that nonsteroidal anti-inflammatory drugs may have a role in reducing that pain.     

Propofol-induced injection pain: comparison of a modified propofol emulsion to standard propofol with premixed lidocaine

Propofol is well known for its association with pain on injection. The most frequently used method to reduce this pain is premixture with lidocaine. Recently, a modified lipid emulsion of propofol containing medium-chain triglycerides (MCT) with long-chain triglycerides (LCT), in contrast to the usual LCT formulation, has been advocated to alleviate pain. In a randomized, prospective, controlled, double-blind study on 222 surgical patients, we compared the effect of the two solutions on the incidence and intensity of injection pain. Patients were randomly allocated to receive either propofol MCT/LCT (group M; n = 109) or standard propofol LCT with the addition of 20 mg of lidocaine (2 mL of lidocaine 1%) to 200 mg of propofol (group L; n = 113). Pain scores were assessed using a verbal analog scale (VAS) ranging from 0-10. Group L was found to have significantly less pain on the injection of propofol (mean VAS, 2.5 +/- 2.9) (mean +/- sd) than group M (mean VAS, 3.8 +/- 3.2; P = 0.002). Regarding postoperative recall of pain on injection, patients in group L indicated significantly less pain (mean VAS, 2.2 +/- 2.4) than patients in group M (mean VAS, 3.0 +/- 2.7; P = 0.02). Premixing of 20 mg of lidocaine (2 mL of lidocaine 1%) to 200 mg of standard propofol LCT causes less pain on injection than propofol MCT/LCT and thus increases patient comfort.     

Effect of ondansetron pretreatment on pain after rocuronium and propofol injection: a randomised, double-blind controlled comparison with lidocaine

In a randomised, controlled, double-blinded trial to study the effect of ondansetron pretreatment on the pain produced after intravenous injection of rocuronium and propofol in comparison with lidocaine, 60 patients were randomly assigned to one of three groups. Group 1 received 5 ml of intravenous 0.9% sodium chloride solution pretreatment, group 2 received ondansetron 4 mg (2 mg.ml-1 solution) diluted into a 5-ml solution, and group 3 received 50 mg lidocaine (5 ml 1% solution); this was followed 1 min later by rocuronium and propofol. Pain was reduced significantly in the ondansetron and lidocaine groups (p < 0.0001) compared with placebo, and significantly better with lidocaine than with ondansetron (p = 0.02). We conclude that ondansetron is effective in relieving the pain of rocuronium but is not as effective as lidocaine.     

The pharmacodynamic effects of a lower-lipid emulsion of propofol: a comparison with the standard propofol emulsion

Using a randomized, double-blind protocol design, we compared a new lower-lipid emulsion of propofol (Ampofol) containing propofol 1%, soybean oil 5%, and egg lecithin 0.6% with the most commonly used formulation of propofol (Diprivan) with respect to onset of action and recovery profiles, as well as intraoperative efficacy, when administered for induction and maintenance of general anesthesia as part of a "balanced" anesthetic technique in 63 healthy outpatients. Anesthesia was induced with sufentanil 0.1 microg/kg (or fentanyl 1 microg/kg) and propofol 2 mg/kg IV and maintained with a variable-rate propofol infusion, 120-200 microg x kg(-1) x min(-1). Onset times to loss of the eyelash reflex and dropping a syringe were recorded. Severity of pain on injection, speed of induction, intraoperative hemodynamic variables, and electroencephalographic bispectral index values were assessed. Recovery times to opening eyes and orientation were noted. The results demonstrated that there were no significant differences between Ampofol and Diprivan with respect to onset times, speed of induction, anesthetic dose requirements, bispectral index values, hemodynamic variables, recovery variables, or patient satisfaction. However, the incidence of pain on injection was more frequent in the Ampofol group (26% versus 6%, P < 0.05). We conclude that Ampofol is equipotent to Diprivan with respect to its anesthetic properties but was associated with a more frequent incidence of mild pain on injection. IMPLICATIONS: The pharmacodynamic profile of a lower-lipid containing emulsion of propofol (Ampofol) was compared with Diprivan when administered for induction and maintenance of general anesthesia. This preliminary study demonstrated that the two formulations of propofol were equivalent with respect to their induction and maintenance properties. However, Ampofol was associated with a more frequent incidence of pain on injection.     

Epidural anesthesia with lidocaine reduces propofol injection pain

PURPOSE: To determine whether epidural lidocaine reduces the severity of propofol injection pain compared with iv lidocaine. METHODS: A prospective, randomized double-blind clinical study was conducted in 120 female patients scheduled for elective gynecological laparotomy. A lumbar epidural catheter and an iv catheter placed in the cephalic vein of the non-dominant hand were used in all patients. Patients of the control group (Group C) were given epidural normal saline followed by iv normal saline then iv propofol. Patients of Group E were given epidural 2% lidocaine (0.08 mL.cm(-1)) followed by iv normal saline and then propofol. Patients of Group V were given epidural normal saline followed by iv 2% lidocaine (0.05 mL.kg(-1)) then propofol. Pain was scored as no pain=0, minimal pain=1, moderate pain=2, severe pain=3. RESULTS: The pain scores, in group E; 1 (0-2) and group V; 2 (0-2), were significantly lower than in group C; 2 (1-3); median (25th-75th percentile) (P <0.001). There was no difference in pain score between groups E and V The plasma lidocaine concentration 15 min after epidural lidocaine was 2.74 +/- 0.54 microg.ml(-1), compared with 1.54 +/- 0.31 microg.mL(-1) at three minutes after iv lidocaine. CONCLUSION: Epidural and iv lidocaine equally reduced the severity of propofol injection pain despite higher lidocaine plasma concentrations in epidurally administered lidocaine.     

Vein pretreatment with magnesium sulfate to prevent pain on injection of propofol is not justified

PURPOSE: Propofol produces anesthesia with rapid recovery. However, it causes pain or discomfort on injection. A number of techniques have been tried for minimizing propofol-induced pain with variable results. We have compared the efficacy of magnesium and lidocaine for the prevention of propofol induced pain. METHODS: Three hundred ASA I and II adults undergoing elective surgery were randomly assigned into three groups of 100 each. Group I received magnesium sulfate 1 g, Group II received lidocaine 2% (40 mg) and Group III received normal saline, all in a volume of 2 mL and accompanied by venous occlusion for one minute. Induction with propofol 2.5 mg.kg(-1) was accomplished following the release of venous occlusion. Pain was assessed on a four-point scale: 0 = no pain, 1 = mild pain, 2 = moderate pain, and 3 = severe pain at the time of pretreatment and propofol injection. Results were analyzed by 'Z' test. A P value of < 0.05 was considered as significant. RESULTS: Pain during i.v. pretreatment with magnesium was 31% as compared to 2% for both the lidocaine and control groups (P < 0.05). Seventy-six percent of patients in the control group had pain during i.v. propofol as compared to 32% and 42% in the magnesium and the lidocaine groups respectively (P < 0.05). Lidocaine and magnesium pretreatment were equally effective in attenuating pain during the propofol injection (P > 0.05). CONCLUSIONS: Intravenous magnesium and lidocaine pretreatment are equally effective in attenuating propofol-induced pain. However, magnesium pretreatment itself causes pain. Therefore, there is no justification in the use of magnesium pretreatment for attenuating pain associated with i.v. propofol.     

A lidocaine/metoclopramide combination decreases pain on injection of propofol

PURPOSE: Injection pain is a well-known adverse effect of propofol which distresses patients. Lidocaine pretreatment is the most popular method for reducing this pain but this drug cannot entirely eliminate the problem. The purpose of this study was to examine the analgesic effect of lidocaine/metoclopramide combination, compared with lidocaine alone, during propofol injection. METHODS: In a randomized, double-blind, placebo-controlled trial, 90 patients, 40 males and 50 females, scheduled for elective plastic surgery received either lidocaine 20 mg plus metoclopramide 10 mg iv, lidocaine 20 mg iv, or placebo (saline); (n = 30 in each), with venous occlusion for one minute, followed by administration of propofol 0.5 mg.kg(-1) into a dorsal hand vein. Pain was assessed on a four-point scale (0 = none, 1 = mild, 2 = moderate, 3 = severe) during propofol injection. RESULTS: 25 patients (83%) complained of pain in the placebo group, compared with 12 (40%) in the lidocaine group (P < 0.05) and three (10%) in the combination group (P < 0.05). Pain score (median) was less in the lidocaine (0) and combination (0) groups than in the placebo group (2); (P < 0.05). The difference in the incidence of pain between the combination and lidocaine groups was significant (P < 0.05). CONCLUSION: A lidocaine/metoclopramide combination is more effective than lidocaine alone for reducing pain on injection of propofol in a peripheral vein.     

Pain on injection of propofol: comparison of metoprolol with lidocaine

BACKGROUND AND OBJECTIVE: Pain is often experienced when propofol is injected, and intravenous lidocaine is often effective in preventing such pain. We decided to determine whether metoprolol, given before the injection of propofol, is as effective as lidocaine in reducing the incidence and severity of the pain. METHODS: Ninety patients scheduled for elective surgery under general anaesthesia were randomly allocated to one of three groups to receive either metoprolol 2 mg, lidocaine 20 mg or saline 2 mL before any propofol was injected. Each patient was given one of these agents intravenously via a 20-G cannula on the dorsum of the hand whilst the venous drainage was occluded manually, at the middle of the forearm, for 45 s. After the occlusion was released, propofol 2.0-2.5 mg kg(-1), at room temperature, was injected at 2 mL (20 mg) every 4 s. Pain was assessed verbally and scored as none (0), mild (1) or severe (2). RESULTS: The incidence of severe pain in the control group (56.7%) was significantly higher than in the metoprolol and lidocaine groups (16.6 and 10%, respectively). The number of patients who were free of pain was significantly higher in those who had been given either metoprolol or lidocaine. CONCLUSIONS: Pretreatment with intravenous metoprolol was equally as effective as lidocaine in reducing the pain associated with propofol injection.     

Effect of lignocaine and pH on propofol-induced pain

Propofol has the disadvantage of pain on injection. A higher partition of propofol in the aqueous phase of the preparation causes a higher incidence of pain on injection while addition of 1% lignocaine to propofol reduces pain. The low concentration of this local anaesthetic and the rapid pain relief observed indicates that mechanisms other than local anaesthesia are involved, that is change in pH. We performed a clinical study to investigate the influence of lignocaine and pH on pain during injection of 1% Diprivan. Ten parts of 1% Diprivan were mixed with one part of saline, 1% lignocaine or hydrochloric acid to achieve the same pH as that after addition of lignocaine. Diprivan 1% mixed with 1% lignocaine and with hydrochloric acid gave mean pain ratings (1-10) of 0.32 (SD 0.75) (n = 25) and 0.88 (1.30) (n = 24), respectively. These ratings were significantly lower than ratings after injection of a saline-Diprivan mixture (2.18 (2.06), n = 22). The pH of the 1% Diprivan formulation decreased after mixing with 1% lignocaine. The concentration of propofol in the aqueous phase was lower when 1% Diprivan was mixed with 1% lignocaine (0.376 g litre-1) or HCl (0.392 g litre-1) compared with 1% Diprivan and saline (0.476 g litre-1) mixed in the same proportion. Thus pH changes may modify propofol-induced pain on injection by a mechanism different from the effect of the local anaesthetic on the vascular endothelium. Our findings may explain why lignocaine mixed with propofol causes less pain than injection of lignocaine followed by propofol.      

The effect of mixing lidocaine with propofol on the dose of propofol required for induction of anesthesia

Lidocaine is used to reduce pain associated with propofol injection, either mixed with propofol or preceding it as a separate injection. The addition of lidocaine to propofol causes destabilization of the emulsion and reduces anesthetic potency in rats and humans. We conducted a randomized double-blinded study on 67 patients to assess the effect of mixing lidocaine with propofol on the dose of propofol required for the induction of anesthesia. Patients in Group S (n = 32) received IV lidocaine 0.2 mg/kg followed by an infusion of propofol whereas those in Group M (n = 35) received IV normal saline (placebo) followed by an infusion of a freshly prepared mixture of propofol 1%/lidocaine 1% in 10:1 volume ratio. The infusion was stopped when the subjects lost consciousness, as detected by the syringe-drop method. There was no statistically significant difference between the two groups in the mean (95% confidence interval) doses of propofol required for loss of consciousness: 2.0 (1.8-2.2) mg/kg for Group S versus 1.9 (1.7-2.0) mg/kg for Group M (P = 0.206). Mixing 20 mg of lidocaine with 200 mg of propofol is unlikely to affect the dose of propofol required for the induction of anesthesia. IMPLICATIONS: Adding lidocaine to propofol destabilizes the propofol emulsion. A randomized double-blinded trial found no statistically significant difference in the doses of propofol required for the induction of anesthesia whether administered as a freshly prepared propofol 1%/lidocaine 1% 10:1 mixture or as a separate injection after a dose of lidocaine.     

Pain during injection of propofol: the effect of prior administration of butorphanol

Propofol causes pain or discomfort on injection in 28%-90% of patients. A number of techniques have been tried for minimizing propofol-induced pain with variable results. We compared the efficacy of butorphanol and lidocaine for prevention of propofol-induced pain. One-hundred-fifty ASA I-II adults, undergoing elective surgery were randomly assigned into 3 groups of 50 each. Group I (NS) received normal saline, Group II (L) received lidocaine 2% (40 mg), and Group III (B) received butorphanol 2 mg. All patients received pretreatment solutions made in 2 mL with normal saline administered over 5 s. One min after pretreatment patients received one-fourth of the total calculated dose of propofol (2.5 mg/kg) over 5 s. Assessment of pain with IV propofol was done by using a four-point scale: 0 = no pain, 1 = mild pain, 2 = moderate pain and 3 = severe pain at the time of propofol injection. In the control Group 39 (78%) patients had pain during propofol injection as compared to 21 (42%) and 10 (20%) in the lidocaine and butorphanol groups, respectively (P < 0.05). Butorphanol was the most effective. We therefore suggest the IV pretreatment with butorphanol 2 mg for attenuation of pain associated with propofol injection.     

Emulsion of flurbiprofen axetil reduces propofol injection pain due to a decrease in free propofol concentration

Purpose Flurbiprofen axetil emulsion (FA), a prodrug of nonsteroidal anti-inflammatory drugs (NSAIDs) that is widely used for perioperative pain relief in Japan, has been effective for reducing propofol injection pain, but the mechanism is unclear. The purpose of this study was to test the hypothesis that the reduction of propofol injection pain by FA may be attributed to a decrease in free propofol concentration. Methods Diprivan (propofol emulsion; Dipri; AstraZeneca, Cheshire, UK) and Propofol-Lipuro (Lipuro; B. Braun, Melsungen, Germany) were used. A randomized double-blind study was performed to compare pain on injection with six kinds of propofol solution: plain Dipri, a 3 : 1 (v/v) mixture of Dipri and saline (Dipri-S), a 3 : 1 mixture of Dipri and FA (Dipri-FA), plain Lipuro, a 3 : 1 mixture of Lipuro and saline (Lipuro-S), and a 3 : 1 mixture of Lipuro and FA (Lipuro-FA). Three hundred patients (American Society of Anesthesiologists [ASA] physical status [PS] I–II) scheduled for elective surgery received one of these six propofol emulsions (n = 50, each group). Injection pain was evaluated every 10 s after the start of a 1-min infusion of up to 2 mg·kg⁻¹ propofol. We also measured the in vitro free propofol concentrations of the propofol preparations that we tested (n = 5, each). Results The mixture of FA with propofol decreased the incidence of injection pain, compared with plain propofol, for Lipuro (P < 0.01) but not for Dipri. The free propofol concentration in each emulsion in vitro was also decreased by mixing the propofol with saline or FA. The incidence of pain was reduced in a free-propofol concentration-dependent manner (R² = 0.926). Conclusion The findings suggest that the reduction of propofol injection pain by FA may be explained, at least in part, by a reduction in the free propofol concentration.     

Nitrous oxide/oxygen mixture and the prevention of pain during injection of propofol

BACKGROUND AND OBJECTIVE: The incidence of pain associated with the injection of propofol still remains a problem. This study sought to examine the analgesic effects of inhaled nitrous oxide in oxygen on the prevention of propofol injection pain. METHODS: Nitrous oxide in oxygen was compared with a lidocaine (20 mg)-propofol mixture and with propofol alone (control) in a prospective, randomized, observer-blinded study. ASA I and II patients (n = 135) scheduled for elective surgical procedures were studied. A standard propofol injection technique and scoring system to measure the pain on injection was used. RESULTS: Demographic variables were similar between the study groups. Without analgesia (control) 26 of 45 patients (58%) reported pain on injection compared with 11 of 45 patients (24%) in both the nitrous oxide (95% CI: 14-52%, P = 0.001) and lidocaine groups (95% CI: 14-52%, P = 0.001). CONCLUSIONS: The inhalation of a nitrous oxide/oxygen mixture significantly reduces the incidence of pain during propofol injection. This therapeutic stratagem was as effective as a lidocaine-propofol mixture.     

Pain on injection of propofol Methods of alleviation

A controlled randomised double-blind design was used to study the effect of lignocaine on the pain produced by intravenous injection of propofol. Patients received a 2-ml pretreatment solution with temporary venous occlusion, followed by an induction solution. One hundred and three patients were assigned to one of five groups: saline pretreatment, followed by induction with propofol plus saline 2 ml; lignocaine 20 mg pretreatment, followed by induction with propofol plus saline 2 ml; lignocaine 40 mg pretreatment, followed by induction with propofol plus saline 2 ml; saline pretreatment, followed by induction with propofol plus lignocaine 20 mg; or saline pretreatment, followed by induction with propofol plus lignocaine 40 mg. Pain was reduced significantly in all groups in which lignocaine was used and a dose of 40 mg was more effective than 20 mg. There were no significant differences in the incidence of pain among the groups which received lignocaine as pretreatment and the groups which received lignocaine mixed with propofol. Sixty-eight percent of patients who experienced pain or discomfort recalled it in the postoperative period.