|Home | About | Journals | Submit | Contact Us | Français|
Some studies have suggested that the intrathecal use of cyclooxygenase enzyme inhibitors provides an anti-nociceptive effect. Therefore, the occurrence of side effects seen in systemic usage can be eliminated.
The primary objective of this experimental, randomized, controlled trial was to test the hypothesis asserting that intrathecal dexketoprofen trometamol would demonstrate an analgesic effect during postoperative period.
Forty rats were randomized into 4 groups 7 days after intrathecal catheterization; the following drugs were given through catheter lumens: Group Lidocaine (Group L): Lidocaine 20 μg; Group Lidocaine-Morphine (Group LM): Lidocaine 20 μg and morphine 0.5 μgr; Group Lidocaine-Dexketoprofen (Group LD): Lidocaine 20 μg and dexketoprofen trometamol 100 μg; and Group Dexketoprofen (Group D): Dexketoprofen trometamol 100 μg. Paw incision was achieved under ether inhalation. To measure analgesic potential, hot plate and tail immersion tests were used as nociceptive tests during the postoperative period.
The mean reaction times detected in groups during hot plate and tail immersion tests were shortest in Group L at 15, 30, 45, 60, 75, 90, 105, and 120 minutes after start of surgery (p<0.01, all others). In the groups using dexketoprofen, as in the morphine group, longer reaction times were detected than in the lidocaine group at all measurement times except 120 minutes (p<0.01).
Intrathecal dexketoprofen in the optimal perioperative pain management is effective, and can be administered as an adjuvant in clinics after neurotoxicity studies in animals, and effective dose studies in volunteers.
Even though beneficial effects of cyclooxygenase enzyme (COX) inhibitors during the perioperative period are apparently known, debates on their usage are ongoing because of their potential risks, such as gastrointestinal mucosa and renal tubular damages, and the induction of platelet dysfunction (1). Some studies have suggested that the intrathecal (IT) use of COX inhibitors provides anti-nociceptive effect, and decrease in hyperalgesia; also, the occurrence of side effects seen in systemic usage can be eliminated (2,3). It has been indicated that nonsteroidal anti-inflammatory drugs (NSAIDs), which can spontaneously pass through the blood-brain barrier or be given via the IT route, demonstrate a central analgesic effect (4).
Dexketoprofen trometamol is a non-selective NSAID belonging to the aryl-proprionic acid group which is an active S-enantiomer of racemic ketoprofen. Owing to its rapid absorption, and the onset of its effect immediately after its administration, it is preferred for the alleviation of acute pains. In various animal studies, the analgesic effectiveness of ketoprofen has been attributed to its dexketoprofen component (5,6). Dexketoprofen trometamol, at the peripheral level, inhibits the release of prostaglandins from the site of the lesion, and subsequently prevents the stimulation of pain receptors. Also, its central effects block activities of COX, leading to a decrease in its central sensitization effect, and inhibit painful stimuli from reaching the upper levels of the nervous system.
Intrathecal dexketoprofen trometamol use has no place in clinical practice. In studies performed using NSAIDs, controversial results have been obtained regarding its IT effectiveness. Starting from this perspective, we aimed to test the hypothesis asserting that IT dexketoprofen trometamol would demonstrate an analgesic effect during the postoperative period.
Ethics approval for this prospective, experimental study (2009/76) was granted by Animal Ethics Committee of Animal Ethics Committee of Ondokuz Mayıs University Faculty of Medicine, Medical and Surgical Research Centre (Chairperson Dr. Fersat Kolbakir) on 23 November 2009. This study was performed using forty 12–16 month-old Sprague-Downey rats weighing 250–300 g from the Medical and Surgical Research Centre of Ondokuz Mayıs University, Faculty of Medicine. During the study, all rats were kept in separate cages under their natural environments (12 alternate hours of light and darkness, at 21±2°C).
Rats were starved from the night before surgery, and given 100 mg/kg i.p. ketamine (Ketalar, Pfizer; İstanbul, Turkey) anesthesia on the day of the experiment. After the induction of anesthesia, rats were fixed in the prone position on a stereotaxy device. After sterilization of the operative site, an occipitocervical incision was made exploring the atlantooccipital membrane. This membrane was perforated to see the flow of cerebrospinal fluid. Then, as described by Yaksh and Rudy (7), a stylet was inserted into a 28 G micro catheter (Portex®, Microcatheter system for continuous spinal anesthesia, Smith Medical; Ashford, UK) used for continuous spinal anesthesia, and advanced 8 cm towards the caudal direction. After placement of the catheter, the incised muscular and cutaneous layers were sutured; the external end of the catheter was fixed with dental acrylic sutures (Figure 1). Using a Hamilton injector, catheter lumen was flushed with 0.01 mL SF (death space volume), and plugged. All rats received antibiotherapy before and after surgical interventions.
To measure analgesic potential, hot plate and tail immersion tests were used as nociceptive tests. These tests were performed by a researcher blinded to the contents of the injector.
Rats were placed on a hot plate (Bioseb; Florida, USA) with a thermostatic base maintaining its mean temperature at 55±0.5°C, and time to the onset of rat’s reaction to hot plate was quantified. Licking or lifting hind paws was considered a positive reaction, and the time interval between rats’ first contact with the hot plate and their positive reactions was recorded. To prevent tissue damage, time to retain the rat on the hot plate was limited to 60 seconds (cut-off time).
The tails of rats were half-dipped into hot water kept constant at a mean temperature of 55±0.5°C; tail-flick or verbal reaction was considered a positive reaction, and the time interval between tail immersion and a positive reaction was recorded. To prevent tissue damage, retention time of the tail immersed in water was limited to 15 seconds (cut-off time).
Baseline value of each nociceptive test was calculated as an arithmetic mean of 3 successive measurements at 7 seven days after catheter insertion, before randomization.
Forty rats were randomized using computer generated random number table into 4 groups 7 days after catheterization; 10 rats were included in each group. The following drugs were given through catheter lumens:
Also, the amount of saline equal to the dead space volume (0.01 mL) was flushed via the external end of the catheters. Intrathecal placement of catheter was corrected with the prolongation of times of nociceptive tests. If there were no changes compare to the baseline values, the rat was excluded from the study and calculations.
The time interval between the delivery of the drug through a catheter and the onset of surgery was standardized as 10 minutes. To achieve immobility and surgical anesthesia in regions where spinal analgesia could not be accomplished, short-term inhalation anesthesia was induced using a cylindrical apparatus containing a swab dipped in a volatile ether solution. Ether inhalation time ranged between 30 and 60 seconds, and after the induction of sedation, surgery (paw incision) was started. As described by Brennan et al. (8), after surgical cleansing of the right hind paw with 70% alcohol, a longitudinal 1 cm incision was made extending from the corner of the heel to a distance 0.5 cm away towards the nails. Through this incision, plantar muscles were exposed, cut lengthwise, and the incision was sutured with 5.0 silk.
Nociceptive tests were applied at 15, 30, 45, 60, 75, 90, 105, and 120 minutes after the start of surgery. Before initiating nociceptive tests, sedation and motor function scores of all rats were rated.
Evaluation of sedation: degree of sedation was rated between “0” and “2” based on the severity of reactions of the rats subjected to auditory and tactile stimuli (Table 1).
Evaluation of motor functions was performed using placing-stepping and righting reflexes.
Placing-Stepping Reflex: Rats begin stepping movements after stimulating dorsum of either hind paw.
Righting Reflex: An animal placed horizontally with its back on the table will normally show an immediate coordinated twisting of the body around its longitudinal axis to regain its normal position on its feet. Responses elicited during both reflex tests were scored as 0, 1, and 2 (Table 2).
Reaction times measured during hot plate and tail immersion tests were compared with baseline values and maximum possible effect (MPE%) was calculated.
Accordingly, we have the opportunity to compare percent changes developed secondary to drug effects that were influential during postoperative test.
Sample size was determined based on previously performed IT ketoprofen study (9) with a statistical power of 80% (α=5%, β=20%). In this study, statistical calculations made in Minitab 14 software statistical program using postoperative mean pain scores obtained in ketoprofen and control group (8.1±1.3 vs. 14.7±1.3). The results indicated that a minimum number of 3 rats in each study group was sufficient with which to conduct statistical analysis. Since we used drugs belonging to the same group but with different formulations, we included 10 experimental animals in each group to increase the statistical power of the study to over 80%.
Data were transferred into SPSS 16.0 program (SPSS Statistic for Windows, Version 16.0, SPSS Inc.; Chicago, IL, USA), and expressed as mean ± standard deviation (SD). Concordance of data to normal distribution was analyzed using Shapiro-Wilk test. Kruskal-Wallis test was used because of the inability to ensure parametric conditions in intergroup comparisons. For pairwise comparisons of different parameters, Mann-Whitney test with Bonferroni correction was used. P<0.05 was considered to be significant.
During catheterization, respiratory arrest occurred in 1 rat, while 3 rats had arrest after a bleeding episode emerged during the insertion of the catheter into the spinal space. After the development of motor deficit in 8 rats and deterioration in the general health status of 3 rats following catheterization procedure, these rats were excluded from the study. In place of these rats, new rats were included in the study to take the study population up to 40 rats.
Before nociceptive tests, the mean sedation score of all rats was found to be “0”, while the mean motor function assessment score was 1 in Groups L and LM, and 2 in dexketoprofen groups. At the time of the second measurement (at 30 min), the motor function score of all rats was “2”. The mean operative time was 5.27±1.06 minutes without any difference between groups.
Baseline mean nociceptive test values are shown in Tables 3 and and4.4. No statistically significant difference was found between baseline values measured in groups during hot plate and tail-immersion tests before IT injection (p=0.467 and p=0.059, respectively).
Mean reaction times detected in groups during hot plate tests and calculated MPE values are shown in Table 3 and Figure 2, respectively. At 15 min, the mean MPE value of Group L was found to be lower than other groups (p=0.000; p=0.003; p=0.005, respectively). The mean MPE value of Group LM was also found to be higher than all other groups (p=0.004 and p=0.000, respectively). At 30 min, the mean MPE value of Group L was found to be lower than other groups (p=0.000, all others). Besides, the mean MPE value of Group LM was noted to be even higher than that of Group D (p=0.008). At 45 min, the mean MPE value of Group L was found to be lower than that of other groups (p=0.000, all others). At 60 min, the mean MPE value of Group L was lower than other groups (p=0.000, all others). Besides, the mean MPE value of Group LM was higher than that of Group D (p=0.002). At 75 min and 90 min, mean MPE values of Group L were found to be lower than those of other groups (p=0.000, all others). At 105 min, the mean MPE value of Group L was shown to be decreased when compared with that of Groups LM and LD (p=0.000, others). At 120 min, the mean MPE value of Group LD was higher than that of Group L (p=0.000).
The mean reaction times in tail immersion tests of groups, and calculated MPE percentages are shown in Table 4, and Figure 3, respectively. At 15 min, the mean MPE value of Group LM was found to be higher than other groups (p=0.000; p=0.004; p=0.000, respectively). At 30 min, the mean MPE value of Group L was detected to be lower than other groups (p=0.000; p=0.001; p=0.001, respectively). Besides, the mean MPE value of Group LM was higher than that of Group D (p=0.008). At 45 min, the mean MPE value of Group L was decreased when compared with other groups (p=0.000; p=0.002; p=0.001, respectively). At 60 min, the mean MPE value of Group L was found to be lower than other groups (p=0.000, all others). At 75 min, the mean MPE value of Group L was detected to be decreased relative to other groups (p=0.000; p=0.007; p=0.000, respectively). At 90 min, the mean MPE value of Group L was noted to be lower than other groups (p=0.001; p=0.003; p=0.003, respectively).
Many studies have indicated that NSAIDs have analgesic effects comparable to opioids without resulting in opioid-like side effects (10,11). A recently published review analyzed 35 randomized clinical studies encompassing 6380 patients where 3381 of them used dexketoprofen trometamol. In 29 of these 30 clinical studies, the drug was seen to be as effective as other analgesics (ketoprofen, paracetamol/codeine, etc.) with known efficacy (12).
Although the benefits of the use of NSAIDs during the perioperative period are clearly known, relevant debates have been conducted because of their potential risks with regard to gastrointestinal mucosal and renal tubular damage, and the induction of platelet dysfunction, as well as their inadequate efficacy relative to opioids (13). It has been conceived that prophylaxis against the apparent side effects of systemic usage of COX inhibitors can be accomplished by administering lower doses of these drugs via the IT route. In previously conducted studies, it was asserted that the IT administration of various non-selective COX inhibitors such as acetylsalicylic acid, ibuprofen, and ketoralac could alleviate hyperalgesia, and they could also be used at doses 100- to 300-fold lower than required for systemic usage without the development of any side effects seen in systemic usage (2,14).
COX-1 and COX-2 have been shown to be incorporated in the structure of the spinal cord (15–17). Various studies demonstrated that COX-2 inhibitors given via IT route are effective in alleviating mechanic allodynia, and thermal hyperalgesia secondary to inflammatory processes (2). On the contrary, in the postoperative pain model created by incisions made on the hind paws of rats, increase in the levels of COX-1 was observed in the spinal cord, and only COX-1 inhibitors could provide an analgesic effect (17).
Intrathecal administration of the non-selective COX inhibitor indomethacin has been shown to inhibit nociceptive wind-up reflex evoked by electrical stimulation of the sural nerve (15). Similarly, ketoprofen inhibits c-fiber activity in rats (18). Lopez-Munoz et al. (19) exposed rats to oral or intracerebroventricular dexketoprofen, and demonstrated that the drug had similar anti-nociceptive efficacy via both routes of administration. They demonstrated that in the peripheral inflammation model induced by carrageenan injection into the plantar surface of the hind paw of a rat, levels of COX-2 mRNA increased more significantly relative to COX-1 mRNA. However, in the postoperative pain model constructed by incising the hind paws of rats, levels of COX-1 mRNA in the spinal cord increased more significantly (20). Zhu et al. (21) intrathecally administered ketorolac, SC-560 (a COX-1 selective inhibitor) or NS-398 (a COX-2 selective inhibitor) 15 minutes before surgery, and found that in response to mechanical stimulation, ketoralac and SC-560 increased the threshold of the paw-flick withdrawal test, while NS-398 did not change this threshold. In thermal hyperalgesia induced by the injection of carrageenan into the paw of rats, SC-560 was found to be ineffective contrary to NS-398. In another study, in a rat model of tonic, chemical pain, after the concomitant IT usage of morphine, and non-selective NSAIDs, emergence of a synergic effect was demonstrated (22).
Miranda et al. (22) induced a chemical pain model by the acetic acid writhing test, and calculated an ED50 value of 0.86 mg/kg for an anti-nociceptive effect of IT use. Ossipov et al. (23) used 100μg IT dexketoprofen after paw incision in the hot plate test. We also have taken all of these studies into consideration, and used IT dexketoprofen trometamol at a dose of 100 µg. Since in our study we wanted to construct a surgical model suitable for spinal anesthesia, we used IT lidocaine in three groups. In our study, we wanted a short-term spinal anesthesia, and used lower doses of lidocaine which could not inhibit the movements of rats, and also paw withdrawal reflex. In fact, motor function assessment score was only ‘1’ in groups who received lidocaine injections before the tests. A partial motor block was observed which impaired the quality of gait, but did not prevent responses of rats to painful stimuli; at the time of the second measurement, the motor functions of all groups recovered completely.
In an experimental study in rats, ED50 of IT morphine was calculated as 1.6 μg/kg (24). Martin et al. (25) found ≥0.5 µg morphine to be effective in mechanic hyperalgesia induced following paw incision in rats. We also used morphine at an IT dose of 0.5 μg MPE values of morphine in the hot plate, and tail immersion tests indicated that its analgesic effect emerged between 15 and 105 minutes after its application. The decline in MPE values after 75 min in the hot plate and 60 min in the tail immersion test demonstrated that the analgesic effect decreases after 60 minutes of application.
Maximum possible effect values in the hot plate test suggested that although analgesic effect of dexketoprofen is inferior to morphine at 15 min, whereas from 30 min onwards, it equaled that of morphine. The peak value was achieved at 60 min in both dexketoprofen groups. Similarly, in the tail immersion test from 30 min up to 105 min, dexketoprofen demonstrated an analgesic effect that was similar to morphine.
Spofford et al. (9) induced postoperative pain model by incising a hind paw, just like we did in our study, and administered 150 µg ketoprofen IT 30 minutes before surgery. For the first hour, they observed pain-avoidance behavior of rats, while 2 hours after surgery they induced thermal hyperalgesia with hot plate test, and mechanic hyperalgesia with von Frey filament method to investigate analgesic efficacy. In these tests, the authors found ketoprofen to be ineffective in alleviating both thermal and mechanic hyperalgesia, while the drug was effective in inducing pain-avoidance behavior as a reaction against post incisional non-evoked pain. Because of the continuality of pain avoidance behavior, and lack of stimulation, they thought that ketoprofen might be effective in postoperative rest pain. Pain-avoidance scores 30 minutes after IT administration on postoperative days 1 and 2 were significantly lower compared with the control group. However, Zhu et al. (21) intrathecally administered 50 µg ketorolac, and 100 µg SC 560 15 minutes before paw incision, and found these drugs to be effective in mechanic hyperalgesia test at the postoperative second hour. However, IT dexketoprofen given 10 minutes before surgery demonstrated an analgesic effect in pain tests beginning from 15 min and extending up to 105 min postoperatively. Martin et al. (25) injected IT ketoralac to laparotomized rats with incised paws in the mechanic pain model, and found that a dose of 50 µg exerted a marked effect, and when added to morphine it augmented the effect of morphine by up to 3.5 times.
Ossipov et al. (23) induced thermal pain in a hot plate test after paw incision, and concluded that IT R-ketoprofen has only anti-allodynic, rather than anti-nociceptive effects, while on the contrary, dexketoprofen (S-ketoprofen) has only anti-nociceptive effects. In the dexketoprofen trometamol group, we detected morphine-like anti-nociceptive efficacy at 30 min in the tail immersion test performed following surgical procedure. Mazario et al. (26) evaluated the response of a single motor unit to electrical stimulation in healthy rats without inflammation, and demonstrated that dexketoprofen trometamol was as potent as µ opioid fentanyl in depressing wind-up, and spinal cord reflexes. This result supports the conclusion of our study.
In conclusion, we foresee that the IT usage of the non-opioid analgesic drug dexketoprofen in optimal perioperative pain management is effective, and that it can be administered as an adjuvant in order to be used as an alternative drug or with the intention of decreasing required opioid dosage. However, neurotoxicity studies and effective dose studies in volunteers must be conducted in the future.
Authors would like to thank Assistant Professor Fatih Ilkaya, MD, for the contribution to the preparation of rats, and Gurkan Kazanci for editing language of the manuscript.
Ethics Committee Approval: Ethics committee approval was received for this study from Animal Ethics Committee of Ondokuz Mayıs University School of Medicine, Medical and Surgical Research Centre.
Informed Consent: N/A.
Peer-review: Externally peer-reviewed.
Author contributions: Concept - B.M.E., İ.S.K.; Design - B.M.E., İ.S.K., A.B., S.B.; Supervision - İ.S.K.; Resource - B.M.E., İ.S.K., A.B., S.B.; Materials - B.M.E., İ.S.K., A.B., S.B.; Data Collection and/or Processing - B.M.E.; Analysis and/or Interpretation - B.M.E., İ.S.K., E.C.C.; Literature Search - B.M.E., İ.S.K.; Writing - B.M.E., İ.S.K.; Critical Reviews - B.M.E., İ.S.K., A.B., S.B., E.C.C.
Conflict of Interest: No conflict of interest was declared by the authors.
Financial Disclosure: All financial and material support for this research and work were Research Founding of Department of Anesthesiology of Ondokuz Mayıs University.