A comparison of the effect of total intravenous anaesthesia with propofol and remifentanil and inhalational anaesthesia with isoflurane on the release of pro- and anti-inflammatory cytokines in patients undergoing open cholecystectomy.
The aim of the study was to investigate the effects of two anaesthetic techniques (total intravenous technique vs. inhalational technique) on changes in pro- and anti-inflammatory cytokine levels during open cholecystectomy. Forty ASA PS I-II patients undergoing open cholecystectomy were randomly assigned to two groups. Group R received total intravenous anaesthesia with propofol and remifentanil and group F received balanced inhalational anaesthesia with isoflurane. The plasma levels of tumour necrosis factor-a (TNF-[alpha]), interleukin IL-6 and interleukin IL-10 were measured during and after surgery.
The pro-inflammatory cytokine levels (TNF-[alpha] and IL-6) and the anti-inflammatory cytokine (IL-10) showed a significant increase in their concentrations compared with pre-induction levels in both groups (P <0.05). By the end of anaesthesia and surgery, TNF-[alpha] and IL-6 were significantly lower in group R than in group F (P <0.05). At the end of anaesthesia and 12 hours postoperatively, IL-10 levels in group R were higher than in group F (P <0.05). These findings suggest that total intravenous anaesthesia using propofol and remifentanil suppresses the inflammatory response caused by surgery to a greater extent than a balanced inhalation technique using isoflurane.
Key Words: total intravenous anaesthesia, propofol, remifentanil, tumour necrosis factor-a, interleukin-6, interleukin-10
Any surgical procedure impairs homeostasis and triggers various haemodynamic, metabolic and immunologic reactions, (1,2). Results of many experimental and clinical studies have found that surgical trauma is associated with an impaired immune response in the postoperative period, which may be connected with altered production of pro-inflammatory cytokines, as well as inhibition of cellular responses (3). It has also been shown that proinflammatory and anti-inflammatory cytokines are pivotal for the acute-phase inflammatory and immunologic response induced after surgical trauma. The most important cytokines in this regard are tumour necrosis factor-[alpha] (TNF-[alpha]), interleukin IL-6 and interleukin IL-10 (4,5).
Anaesthesia itself may also alter immune function with potential impact on the postoperative course. General anaesthesia accompanied by surgical stress may influence the inflammatory responses that are essential for maintaining the homeostatic state during the postoperative course (6). Various anaesthetics have been suspected of impairing various functions of the immune system either directly, by disturbing the functions of immune-competent cells, or indirectly by modulating the stress response (7,8). Different anaesthetic methods may interfere with the stress response, especially cytokine activation during and after surgery.
The aim of this study was to evaluate possible differences in the plasma cytokine response of TNF-[alpha], IL-6 and IL-10 with two anaesthetic techniques--total intravenous anaesthesia (TIVA) using propofol/remifentanil versus balanced inhalational anaesthesia using isoflurane, in open cholecystectomy.
After approval by the local ethics committee and written informed consent, 40 patients (ASA physical status I-II) undergoing open cholecystectomy were randomised to receive either TIVA with propofol and remifentanil (group R, n=20) or with isoflurane and fentanyl (group F, n=20). Exclusion criteria were as follows: immune system disorders, major systemic illness known to alter inflammatory changes such as rheumatoid arthritis, and steroid medication within the past six months.
After the insertion of a peripheral IV cannula, anaesthesia was induced with remifentanil (0.5 [micro]g/kg/min) and propofol (6 mg/kg/h) in group R, and with fentanyl (3 [micro]g/kg) and propofol (2 to 3 mg/kg) in group E. In both groups, muscle relaxation was achieved with vecuronium (0.15 mg/kg) and tracheal intubation was performed using an endotracheal tube. The cuff was inflated with 10 ml of air. After endotracheal intubation, the infusion rate of propofol was decreased to 3 mg/kg/h and another infusion of remifentanil (0.25 [micro]g/kg/min) was started in group R. To achieve similar depth of anaesthesia, BIS monitoring (Monitor Model A-2000[TM], Aspect Medical Systems Inc) was used targeting values between 40 and 50 intraoperatively. Increases in BIS-levels >50 were treated by increasing, first, the isoflurane concentration (up to 1.2 MAC) and second, by a bolus of fentanyl (1 [micro]g/kg) in group F and in group R, by an increase first in propofol infusion rate (max 6 mg/kg/h) and second in the remifentanil infusion rate (max 0.35 [micro]g/kg/min). Muscle relaxation was supplemented with vecuronium 0.05 mg/kg as required. The lungs of the patients were ventilated using a pressure-controlled mode with a maximum pressure of 20 cm[H.sub.2]0 and a positive end-expiratory pressure (PEEP) of 5 cm[H.sub.2]O. Ventilation rate and maximum airway pressure were adjusted to maintain a normal end-tidal C[O.sub.2] (33 to 43 mmHg). Monitoring included continuous measurement of arterial blood pressure (mean arterial pressure [MAP]), heart rate (HR) and oxygen saturation (pulse oximetry). Hypotension (MAP <60 mmHg) was corrected with either fluid administration (lactated Ringer's solution, hydroxyethyl starch solution) or a small bolus of ephedrine.
Blood samples were drawn immediately before induction of anaesthesia ([T.sub.1]), at the end of anaesthesia and surgery ([T.sub.2]) and 12 hours postoperatively ([T.sub.3]). Blood samples (10 ml each) from all tested patients were drawn via an indwelling catheter inserted into a forearm vein and collected in heparinised syringes. After centrifugation of the blood at 3000 rpm for 10 minutes at 4[degrees]C, separated plasma samples were stored in two or three aliquots (120[micro]l) at -70[degrees]C until cytokine assay.
Using commercially available kits (Opt-EIA; Pharmingen, San Diego, CA, U.S.A.), plasma levels of TNF-[alpha], IL-6 and IL-10 were measured by a two-step sandwich enzyme-linked immunosorbent assay method, according to the manufacturer's instructions. Standards and samples were pipetted into the wells of a microtitre plate, which are precoated with specific cytokine antibodies. Cytokines are bound by the immobilised antibody. After washing away any unbound substances, an enzyme-linked polyclonal antibody specific for a cytokine is added to the wells. After a wash to remove any unbound antibody enzyme reagent, tetramethylbenzidine is added to the wells. The enzyme reaction yields a blue product, which turns yellow when the stop solution sulphuric acid is added. The optical density measured is in proportion to the amount of cytokine bound in the initial step. The sample values are then interpolated into the standard curve.
Analysis of variance for repeated measurements was used to compare the changes in values achieved at different intervals and to compare the difference between groups. Statistical analysis was undertaken with SPSS 11.5 (SPSS, Inc., Chicago, IL, U.S.A.) and P < 0.05 was considered statistically significant.
Patient groups were similar with regard to age, weight, gender, duration of anaesthesia and transfusion requirement. All values are expressed as mean [+ or -] SD (Table 1).
Pre-induction values of the pro-inflammatory cytokine levels (TNF-[alpha] and IL-6) and the anti-inflammatory cytokine (IL-10) did not differ significantly between the two groups. By the end of anaesthesia and surgery, TNF-[alpha] and IL-6 showed a significant change in their concentrations (P <0.05, Table 2). By 12 hours postoperatively, their values were still higher than the pre-induction level (P <0.05, Table 2). Also, the anti-inflammatory cytokine (IL-10) in both groups was increased significantly (P <0.05, Table 2) by the end of anaesthesia and surgery compared with the pre-induction level. It was then decreased at 12 hours postoperatively compared with the end of anaesthesia and surgery to reach a value above the pre-induction level (Table 2).
By the end of anaesthesia and surgery, TNF-[alpha] and IL-6 concentrations were significantly lower in group R (101[+ or -]20, 3.5[+or -]3.4 pg/ml) than in group F (164[+ or -]23, 18.7[+ or -]6.1 pg/ml, P <0.05, Table 2). At 12 hours postoperatively, the two cytokine levels appeared slightly higher in group F (132[+ or -]19, 15.5[+ or -]5.2 pg/ml) than in group R (98[+ or -]17, 13.7[+ or -]4.5 pg/ml), but the differences were not significant (Table 2). The IL-10 concentrations at the end of anaesthesia and surgery and 12 hours postoperatively in group R were higher than in group F (P <0.05, Table 2).
Major surgery causes a variety of physiological changes that are known collectively as the 'stress response' to surgery (1,2). The systemic inflammatory response during and after surgery is important in the development of postoperative complications. Severe dysregulation of the inflammatory process may provoke or aggravate postoperative complications, e.g. increased susceptibility to infections, inadequate stress reactions and hypercatabolism. Furthermore, the inflammatory cytokine response may exert a profound impact on the circulatory stability. Cytokines play a central role in the acute inflammatory and immune response initiated by trauma or infection (4,5).
Cytokines are a heterogeneous group of proteins which orchestrate the inflammatory response after surgery (9). The pro-inflammatory cytokines (IL-1, IL-6 and TNF-[alpha]) and the anti-inflammatory cytokines (IL-4 and IL-10) have local and systemic effects, which attempt to limit injury and the spread of infection, and provide a suitable environment for tissue healing and repair (10,11). The current study showed that the cytokine response to open cholecystectomy influenced both the pro-inflammatory (TNF-[alpha] and IL-6) and anti-inflammatory (IL-10) components.
TNF-[alpha] is thought to be the 'hub of the cytokine network', which is a critical early mediator in the genesis of a systemic inflammatory response. In addition to stimulating the production of secondary cytokines, such as the pro-inflammatory interleukin-6 and the anti-inflammatory interleukin-10, TNF-[alpha] is a primary inflammatory mediator that is responsible for many physiological changes such as hypotension, fever, tachycardia, oliguria and changes in consciousness in patients with septic shock (12,13). Overproduction of TNF-[alpha] can be disastrous to the host and is seen in such pathological conditions as autoimmune disorders and septic shock (14,15).
Interleukin-6 is a multi-potent cytokine produced in the course of inflammation (16). In addition to its role in the inflammatory response, it is important in host defence, immune responses and haematopoiesis. Interleukin-6 is critical to the development of acute-phase response during inflammation and has been demonstrated to be necessary for the final stages of plasma cell development as well as participating in a number of other processes (17-19). It has been reported that the IL-6 concentration in peripheral vein blood increases rapidly after abdominal surgery and the IL-6 response to surgery reflects the extent of tissue damage (20).
Interleukin-10 is associated with immunosuppressive responses (21). Interleukin-10 is a well-characterised cytokine produced by Th2 cells and has been shown to have predominately anti-inflammatory effects. This cytokine inhibits the production of IFN-y by lymphocytes, TNF-[alpha] and IL-6 by macrophages and monocytes, and TNF-[alpha] and granulocyte-macrophage colony-stimulating factor production by eosinophils. IL-10 is thought to be important in modulating multiple aspects of the Th2 response to certain parasitic infections. In IL-10 gene-deficient mice an overproduction of inflammatory cytokines and development of chronic inflammatory diseases have been shown (22,23).
Changes in the cytokines levels caused by surgical trauma are believed to influence local cellular immune response within the peritoneum. During that immunologic response several cells and mediators are engaged, both to eliminate infectious agents and remove and repair damaged tissues. The above-mentioned reactions are balanced by anti-inflammatory mechanisms that are responsible for the restoration of homeostasis and proper functioning of the afflicted tissues and organs. Regaining the correct function by the particular tissues and organs also depends on the delicate balance between the mediators of pro-inflammatory and anti-inflammatory mechanisms. Furthermore, increased levels of pro-inflammatory cytokines after major surgical procedures have been connected with increase in postoperative complications and morbidity (24,25). In the present study, elevated levels of TNF-[alpha] and IL-6 were demonstrated throughout the study period. At the same time, increased levels of the anti-inflammatory cytokine IL-10 were also observed. It is possible that the increased release of IL-10 observed after surgery plays a protective role during infection and trauma.
Our findings indicate that the choice of anaesthetic technique appears to affect the release of cytokines. Recently it has been shown both in vitro and in vivo that several intravenous anaesthetic agents have anti-inflammatory effects. Ketamine prevents the pro-inflammatory cytokine (TNF-[alpha], IL-1 and IL-6) responses to endotoxemia in vivo (26). Moreover, thiopentone, etomidate and propofol increase IL-10 concentrations in LPS-induced cultured human whole blood (27).
Remifentanil is a recently introduced, esterase-metabolised synthetic opioid with an extremely short duration of action. Remifentanil provides intense analgesia, and has been shown to provide excellent intraoperative haemodynamic stability with rapid postoperative recovery. Remifentanil is a highly effective mu opioid agonist with predictable pharmacokinetics and a close concentration effect relationship (28). Remifentanil for fast-track cardiac anaesthesia provided more safe and stable operating conditions and facilitated earlier tracheal extubation than sufentani1 (29). The results of some workers support the hypothesis that opioid analgesics play an important role in the attenuation of the cytokine response. Crozier (30) et al found that IL-6 production was both suppressed and delayed in patients receiving TIVA with propofol and alfentanil after abdominal hysterectomy. The suppression mechanisms are probably related to an interaction with the opioid receptor. Cyclic-AMP (cyclic adenosine monophosphate), as a second messenger, which could stimulate IL-6 secretion is reduced, leading to attenuation of IL-6 and TNF-[alpha] production (31). In this study, using propofol and remifentanil infusion, TNF-[alpha] and IL-6 concentrations were significantly lower in group R than in group F (P <0.05, Table 2).
This study investigated the cytokine levels in patients after open cholecystectomy in order to assess whether there exists a difference in cytokine levels between two different anaesthetic techniques. Serum TNF-[alpha] and IL-6 in both groups had a significantly rapid rise and circulating IL-10 concentrations also had an increase during and after surgery, which was significantly different between the two groups. Propofol and remifentanil seemed to have a significant effect on TNF-[alpha], IL-6 and IL-10 release. Our study certainly suggests that IL-10 concentrations in group R are higher than that in group F patients. Thus, with respect to limitation of surgery-associated stress, TIVA using propofol/remifentanil seems to have a favourable effect. Moreover, induction of the release of anti-inflammatory mediators under TIVA might contribute to the prevention of excessive post-operative inflammation, although this hypothesis would require further testing.
There are several limitations to this study. First, only a small number of patients were studied, limiting its statistical power. Also, we measured only three of several hundred known cytokines. Future studies would benefit from assessments of more cytokines and the effect of other anaesthetic techniques (e.g. regional vs. general). More importantly, we measured cytokine levels but not outcomes. Therefore further clinical studies would be required to ascertain whether the differences in cytokine levels affect any clinical outcome measures.
In summary, our data suggest that anaesthetic technique may have an influence on pro- and anti-inflammatory cytokine levels. TIVA using propofol/remifentanil has a better profile in relation to cytokine levels than a balanced inhalational technique with isoflurane. While the clinical implications of these findings are not known, it is possible that TIVA with propofol and remifentail may offer advantages in terms of inflammatory and immunomodulatory effects compared to an inhalational technique with isoflurane.
We thank Yichang Renfu Corporation (Yichang, China) for their excellent assistance in fund support.
Accepted for publication on September 25, 2007.
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J.J. KE *, J. ZHAN *, X.B. FENG *, Y. WU *, Y. RAO *, Y.L. WANG [dagger]
Department of Anesthesiology, Zhongnan Hospital of Wuhan University, Hubei Province, Peoples Republic of China
* M.D., Anaesthetist. [dagger] M.D., Professor.
Address for reprints: Professor Yan-Lin Wang, Department of Anesthesiology, Zhongnan Hospital of Wuhan University, East-lake Road 169, Wuhan, Hubei Province, 430071, PR China. firstname.lastname@example.org
TABLE 1 Characteristics of the two groups (mean [+ or -] SD, n=20) Characteristics Group R Group F Age (y) 48.0 [+ or -] 12.1 47.6 [+ or -] 13.2 Weight (kg) 52.0 [+ or -] 10.6 52.9 [+ or -] 9.7 Gender (% male) 46 44 Duration (h) 1.8 [+ or -] 0.3 1.9 [+ or -] 0.3 IV fluid (ml) 1308 [+ or -] 210 1446 [+ or -] 315 TABLE 2 TNF-, IL-6 and IL-10 concentrations in both groups before and after surgery (mean [+ or -] SD, n=20) Cytokines Groups [T.sub.1] [P.sub.1] * TNF-[alpha] (pg/ml) R 4.2 [+ or -] 0.5 0.1271 F 4.5 [+ or -] 0.7 IL-6 (pg/ml) R 3.4 [+ or -] 0.8 0.1877 F 3.1 [+ or -] 0.6 IL-10 (pg/ml) R 2.7 [+ or -] 0.2 0.1177 F 2.5 [+ or -] 0.3 Cytokines Groups [T.sub.2] [P.sub.2] * TNF-[alpha] (pg/ml) R 101 [+ or -] 20 * ** <0.001 F 164 [+ or -] 23 ** IL-6 (pg/ml) R 13.5 [+ or -] 3.4 * ** 0.0019 F 18.7 [+ or -] 6.1 ** IL-10 (pg/ml) R 76.2 [+ or -] 15.5 * ** <0.001 F 43.2 [+ or -] 11.5 ** Cytokines Groups [P.sub.2] ** [T.sub.3] TNF-[alpha] (pg/ml) R <0.001 98 [+ or -] 17 ** F <0.001 132 [+ or -] 19 ** IL-6 (pg/ml) R <0.001 13.7 [+ or -] 4.5 ** F <0.001 15.5 [+ or -] 5.2 ** IL-10 (pg/ml) R <0.001 63.9 [+ or -] 14.1 * ** F <0.001 38.3 [+ or -] 9.2 ** Cytokines Groups [P.sub.3] * [P.sub.3] ** TNF-[alpha] (pg/ml) R 0.0607 <0.001 F <0.001 IL-6 (pg/ml) R 0.2491 <0.001 F <0.001 IL-10 (pg/ml) R <0.001 <0.001 F <0.001 P * represents group R compared with group F; P ** represents comparison with the same group at [T.sub.1].