Surgical trauma produces immune suppression and an inflammatory response that includes the release of pro-inflammatory interleukins (IL).1 General anaesthesia may impair the immune competence of cells and influences the inflammatory response to surgery, including the concentration of both pro- and anti-inflammatory interleukins.2–5
One of the most important pro-inflammatory interleukins whose concentration is influenced by both surgery and anaesthesia is IL-6. Circulating IL-6 concentrations increase after surgery to a degree that reflects the magnitude, duration and type of surgical intervention, for example open vs. laparoscopic.3,6–8 In cancer patients, IL-6 promotes tumour growth, affects tumour cell differentiation and protects cells from apoptosis.9,10
IL-10 is one of the most important cytokines with anti-inflammatory properties and its concentration is also an indicator of the extent of surgical stress.11 IL-10 suppresses pro-inflammatory cytokine synthesis and favours antitumour immunity.12,13
It has been shown that there are differences between intravenous and volatile anaesthetics in their effects on the immune response.14–17 Isoflurane and sevoflurane inhibit natural killer (NK) function to a greater degree than propofol.2,5,17 Sevoflurane and isoflurane increase pro-inflammatory cytokines, mainly IL-6, while propofol decreases them.14,15,18–20 These effects may be at least partly responsible for the differences in long-term outcome in cancer patients that have been reported, mainly in cancer recurrence.2,17,21,22 Only a few studies have focused on the influence of different techniques of general anaesthesia on the interleukin response in cancer patients and the results are not conclusive.23–25
The aim of the present study was to compare the influence of total intravenous anaesthesia (TIVA) using propofol with isoflurane anaesthesia on plasma concentrations of pro- and anti-inflammatory interleukins IL-6 and IL-10 in patients undergoing colorectal surgery for cancer.
Materials and methods
Ethical approval for this study (IRB approval no. 498/2011) was provided by the Ethical Committee of the Iuliu Hatieganu University of Medicine and Pharmacy Cluj-Napoca, Romania (Chairperson Prof Dr F Loghin) in December 2011.
After obtaining written informed consent, 70 American Society of Anesthesiologists (ASA) physical status 1 to 3 patients scheduled for colorectal surgery between February 2012 and August 2013 were allocated randomly into one of two study groups (35 patients each) by block randomisation (10 patients block size, allocation ratio 1 : 1) using a computer random number generator: in one group, patients were anaesthetised using TIVA and in the other group, patients were anaesthetised with isoflurane. Patients underwent open colorectal surgery with tumour resection (colectomy, anterior resection of the rectum) for cancer. All patients were operated on by the one of two surgical teams.
Inclusion criteria were patients over 18 years of age, with no sign of local invasion or distant metastasis at preoperative evaluation using imaging studies. Patients with hepatic or renal impairment, diabetes or other endocrine disorders, obesity (BMI ≥30 kg m−2), immune disorders or immunosuppressive therapy, asthma, steroid treatment in the last 6 months, chronic use of benzodiazepines or alcohol abuse were excluded from the study. We also excluded patients who had undergone radiotherapy or chemotherapy for colorectal cancer before surgery. Rectal amputations were also excluded from the study.
All patients received premedication with oral midazolam 7.5 mg before surgery. On arrival in the operating room, a peripheral venous cannula was inserted and a blood sample was taken for interleukin measurement. This cannula was designated for fluid administration during anaesthesia and for blood sampling for subsequent interleukin measurements during the postoperative period. An infusion of compound sodium lactate solution 500 ml was started after the first blood sample had been taken. A second cannula was inserted for the administration of anaesthetic drugs and for delivery of postoperative fluid infusions and analgesics.
Routine monitoring was used intraoperatively: ECG, heart rate (HR), noninvasive arterial blood pressure (BP), pulse oximetry (SpO2), capnography, end-tidal concentration of isoflurane and core temperature using a nasopharyngeal thermocouple probe. Depth of anaesthesia was monitored using bispectral index (BIS) (Vista; Aspect Medical System, Newton MA, USA).
Patients in the TIVA group received TIVA using a target-controlled infusion (TCI) of propofol (Orchestra Base Primea, Fresenius Vial, Brézins, France). Anaesthesia was induced with an initial target plasma concentration of 4 μg ml−1 using the modified Marsh model. The target concentration of propofol was then adjusted in steps of 0.2 μg ml−1 to maintain the targeted BIS value. The infusion of propofol was discontinued at the end of surgery before the last two skin stitches were inserted.
In patients in the isoflurane group, anaesthesia was induced with a bolus dose of propofol 1.5 to 2 mg kg−1 and maintenance of anaesthesia was achieved with isoflurane. Administration of isoflurane was stopped before the last two stitches were inserted.
Atracurium 0.5 to 0.6 mg kg−1 was administered to facilitate tracheal intubation and additional 10-mg boluses were given as needed. In all patients, the lungs were ventilated with 50% oxygen in air using pressure-controlled ventilation with end-tidal carbon dioxide partial pressure maintained between 4.7 and 5.3 kPa.
Depth of anaesthesia was monitored in both groups and the target concentration of propofol or the inspired isoflurane concentration was adjusted to maintain BIS values between 40 and 55.
In both groups, a TCI of remifentanil (Minto model) (Orchestra Base Primea, Fresenius Vial) was used for intraoperative analgesia, with an initial target concentration set at 4 ng ml−1 at induction, and between 3 and 8 ng ml−1 during maintenance. The target concentration was adjusted using increments of 0.5 ng ml−1, depending on the patients’ analgesic needs assessed by changes in HR, BP (more than 20% above baseline value), pupil size, sweating and lacrimation. The remifentanil infusion was stopped after skin closure.
At the end of surgery, neuromuscular blockade was reversed with neostigmine 0.05 mg kg−1, given with atropine 20 μg kg−1.
Postoperative analgesia was achieved using patient-controlled analgesia (PCA) with morphine boluses of 1 mg and a 5-min lockout period, with the aim of maintaining a pain score of less than 3 on a 10-point visual analogue scale (VAS). Intravenous morphine 0.15 mg kg−1 was administered 40 min before the end of surgery. When necessary, a 5-mg dose of morphine was administered in the recovery room to establish adequate analgesia before starting PCA. The loading doses were added when calculating the morphine requirement in the first 24 h postoperatively. In addition, intravenous paracetamol 1 g was administered every 8 h; the first dose was administered 30 min before the end of surgery. Postoperative nausea and vomiting (PONV) were treated by intravenous ondansetron 4 mg at the patient's request or when needed. None of the patients received dexamethasone for PONV prophylaxis.
SBP, DBP and HR were recorded every minute during induction and every 5 min after tracheal intubation, until the end of surgery. Hypotension (defined as a decrease of mean arterial BP by more than 20% of the baseline value) was treated with an increased infusion rate of crystalloid solution and intravenous boluses of ephedrine.
Blood loss was estimated by weighing the swabs and adding blood suction loss.
Target plasma concentrations of propofol and remifentanil were recorded every 5 min and the mean plasma concentration was calculated for each drug. The total requirement of remifentanil during surgery was also recorded to exclude the potential effects of significant differences in remifentanil requirements on the inflammatory response after surgery.
During the first 24 h postoperatively, the total morphine requirement, pain scores at 6, 12 and 24 h and the incidence of PONV requiring antiemetic administration were recorded. As indices of short-term outcome, the length of hospital stay (LOS) and the incidence of postoperative complications (thromboembolic events, surgical complications) were also recorded.
Interleukin IL-6 and IL-10 measurement
Blood samples (7 ml) were taken after venous cannula insertion before starting intravenous fluids and induction of anaesthesia (T0), after intubation but before skin incision (T1), and 2 h (T2) and 24 h (T3) after extubation.
Blood sampling before incision (T1) was performed using a separate venous puncture on the contralateral arm. At T2 and T3, blood samples were taken from a dedicated cannula inserted after anaesthesia. This cannula was preserved only for blood sampling; postoperative fluids, analgesics and antiemetic were administered through the cannula left in place after anaesthesia. The first 5 ml of blood was discarded and the next 7 ml was collected for interleukin assay.
The samples were centrifuged at 2500 rpm for 10 min and the plasma was stored at –70°C until interleukin assays were undertaken. These were performed using commercially available kits (Human IL-6, IL-10; Qantikine ELISA R&D Systems, Minneapolis, Minnesota, USA) as per manufacturers’ instructions (http://www.rndsystems.com/Products/D6050). Laboratory staff were unaware of the study group and were not involved in anaesthetic management.
Detection limits for interleukins as given by the manufacturer were less than 0.7 pg ml−1 for IL-6 and less than 3.9 pg ml−1 for IL-10.
We hypothesised that colorectal surgery for cancer leads to the release of pro-inflammatory interleukins and that TIVA would lead to a lower concentration of pro-inflammatory cytokines than isoflurane anaesthesia. The primary outcome of the study was IL-6 concentration. Secondary outcomes were IL-10 concentration, the VAS pain scores, postoperative opioid consumption and PONV during the first 24 h. Hospital stay and postoperative intrahospital complications were also recorded and compared. The sample size was calculated from a pilot study (n = 9 patients in each group). Calculated area under curve (AUC) for IL-6 showed a 45.3 pg h ml−1 mean difference between the two groups. For a type 1 (α) error of 0.05 and a type 2 (β) error of 0.02, we calculated a sample size of 29 patients per group. On the basis of our previous experience, we decided to enrol a slightly larger number of patients due to possible surgical or technical reasons for exclusion or missing data.
Statistical analysis was performed using SPSS 16.0 (SPSS Inc., Chicago, Illinois, USA). Nominal data were described by frequency and percentage. Quantitative data were tested for normality using the Kolmogorov–Smirnov test. Quantitative variables were described by mean and standard deviation or median (range), as appropriate. Between-group AUC and single-measurement differences were assessed using the Mann–Whitney U test or Student's t-test, as appropriate. The frequencies of nominal variables between groups were compared with a χ2 test. The level of statistical significance for univariate analysis was set at a P value less than 0.05. Differences between groups for variables that were measured repeatedly (VAS, IL-6, IL-10) were analysed using analysis of variance (ANOVA) for repeated measures. Bonferroni correction for multiple comparisons was used, leading to an α threshold of 0.01.
Of the 70 enrolled patients, 60 completed the study (Fig. 1). Patients’ characteristics, durations of anaesthesia and surgery, and type of surgery are summarised in Table 1. The highest blood loss was 1000 and 850 ml in the TIVA and isoflurane groups, respectively.
BIS values, core temperature, blood loss, remifentanil consumption and plasma remifentanil concentration intraoperatively did not differ between the groups (Table 2). The highest mean plasma concentrations of remifentanil during surgery were 6.5 ng ml−1 in the TIVA group and 6.06 ng ml−1 in the isoflurane group. In the recovery room, patients in the TIVA group received 8.8 ± 6.0 mg of morphine and patients in the isoflurane group received 8.2 ± 6.0 mg. The two groups consumed similar doses of morphine during the first 24 h and had similar VAS pain scores (Table 2).
Median (range) AUC values for IL-6 were 4657 (1219 to 8427) pg h ml−1 in the TIVA group and 5349 (839 to 8126) pg h ml−1 in the isoflurane group (P = 0.16). For IL-10, the AUC values were 1165 (344 to 5258) pg h ml−1 in the TIVA group and 1405 (463 to 8161) pg h ml−1 in the isoflurane group (P = 0.08).
Two-way ANOVA for multiple comparison of the time trend of interleukin concentrations between study groups showed no significant differences in IL-6 plasma concentration (P = 0.6) (Table 3). Similarly, for IL-10, taking into consideration the Bonferroni correction, there were no significant differences in plasma concentrations (P = 0.05) (Table 3). However, there was a trend towards higher IL-6 and IL-10 concentrations in the isoflurane group.
For within-group comparisons, the IL-6 and IL-10 plasma concentrations were significantly higher than baseline 2 and 24 h postoperatively in both the TIVA (P < 0.001 and P < 0.001 for IL-6 and IL-10, respectively) and the isoflurane groups (P < 0.001 and P < 0.001, respectively) (Table 3).
The mean LOS was 10.5 ± 7.5 days in the TIVA group and 10.1 ± 2.5 days in the isoflurane group. There were two fistulae in each group, and one death in the isoflurane group on the 15th postoperative day.
Our findings indicate that there were no significant differences produced by propofol or isoflurane on the IL-6 and IL-10 concentrations evaluated as AUC of plasma concentration for the first 24 h postoperatively. We also found no significant differences between groups using within-group analysis of the time trend of interleukin concentrations, although the values appeared to be greater in the isoflurane group.
In the last decade, it has been shown that anaesthetic agents may influence the balance between pro- and anti-inflammatory responses to surgery1,4,17 and may have an impact on cancer cell behaviour and tumour growth, thus influencing long-term postoperative outcome in cancer patients.2,5,21
In clinically relevant concentrations, propofol has only a minor effect on NK cell and lymphocyte activity compared with other intravenous agents.2,17,21,26 Propofol also has anti-inflammatory and antitumour properties, and cyclo-oxygenase (COX-2) inhibiting activity.22,27,28 The volatile anaesthetics isoflurane and sevoflurane modify tumour cell growth in a time-dependent manner.29
Similar results to ours have been reported by other studies in both cancer23–25 and noncancer patients.16,30 Kvarnström et al.23 found no significant differences between TIVA with propofol-remifentanil and sevoflurane-fentanyl anaesthesia in IL-6 concentrations during the first 24 h after open colorectal surgery, although potential differences between fentanyl and remifentanil were not considered by the authors. In patients with bladder cancer undergoing radical cystectomy, Sofra et al.24 reported that the plasma concentration of IL-6 was not significantly influenced in the early postoperative period by anaesthetic management (TIVA vs. sevoflurane). Deegan et al.25 found the same after breast cancer surgery when comparing sevoflurane-fentanyl with propofol-paravertebral anaesthesia. These studies were performed on smaller groups of patients, sometimes without a power calculation.24
Similar findings have been reported by Gilliland et al.16 and Ihn et al.30 who found that IL-6 concentration was not influenced by anaesthetic drugs in abdominal noncancer surgery.
Regarding the plasma concentrations of IL-10, our results showed no significant differences between TIVA and isoflurane anaesthesia. Our data are similar to those reported by Kvarnström et al.23 who did not find significant differences between TIVA with propofol-remifentanil and inhalational anaesthesia with sevoflurane-fentanyl during open colorectal cancer surgery. Different results from ours have been reported by others in cancer patients. Deegan et al.25 reported a significant increase in IL-10 concentration postoperatively in propofol-paravertebral anaesthesia vs. sevoflurane-opioid anaesthesia for breast cancer surgery.
In cancer patients, increased concentrations of IL-6 promote tumour growth, affect tumour cell differentiation and protect cells from apoptosis,9,10 while IL-10 suppresses pro-inflammatory interleukins and favours antitumour immunity.11
In the present study, both IL-6 and IL-10 exhibited significant increases 2 and 24 h postoperatively when compared with the baseline, independent of the anaesthetic technique. In patients suffering from cancer, Kvarnström et al.,23 Sofra et al.24 and Deegan et al.25 have all reported a significant increase in IL-6 concentrations at different time intervals postoperatively up to 5 days.24 As with IL-6, Kvarnström et al.23 found a significant postoperative increase in IL-10 concentrations, whereas Sofra et al.24 reported no changes in IL-10 concentrations compared with baseline after bladder cancer surgery.
We used morphine PCA for postoperative analgesia.31,32 Although immune suppressive effects of morphine have been described,4,21,22 we did not take them into consideration in our study. However, morphine consumption was similar in both groups and, unlike other studies, we administered the same opioids to both groups both during anaesthesia and postoperatively. In addition, there were no significant differences in both intraoperative and postoperative opioid requirements, effectively excluding a potential influence of opioids on interleukin concentrations in our study.
It is also known that blood transfusion may influence IL-6, IL-8 and IL-10 concentrations.33,34 In our study, there were no differences in blood transfusion requirements between study groups, thus eliminating the potential influence of blood transfusion on IL-6 and IL-10 concentrations.
The sample size was calculated on the basis of anticipated IL-6 concentrations, and thus may be underpowered for IL-10. However, we enrolled more patients than other studies on the same topic. The follow-up period was limited to 24 h, and interleukin concentrations may have returned closer to baseline values after a longer time interval. Due to the short time interval for postoperative follow-up, we did not evaluate the incidences of recurrence of cancer. Therefore, we consider that the limitations of our study are the short period of follow-up and the lack of information about long-term outcome.
The strengths of our study are the power of the study, the consistency of opioids used intraoperatively and postoperatively, the similar amounts of blood transfused, the doses of opioid administered and the similar pain scores between the propofol and isoflurane groups. Control of these variables eliminates possible cofactors that might affect the IL-6 and IL-10 concentrations.
In conclusion, we did not find significant differences in plasma concentrations of IL-6 or IL-10 between propofol-remifentanil and isoflurane-remifentanil anaesthesia after colorectal cancer surgery during the first 24 h postoperatively. However, further studies on larger groups of patients are needed to investigate the relationship between interleukin concentrations, general anaesthetic techniques and long-term outcome of these patients.
Acknowledgements relating to this article
Assistance with the study: the authors would like to thank Mrs Rodica Rahaian for performing the interleukin assays.
Financial support and sponsorship: the study was supported by an internal grant (no. 27020/2011) from Iuliu Hatieganu University of Medicine and Pharmacy, Cluj-Napoca, Romania, and partly from a grant for human resources development POSDRU 61577; Erika Balla received a research scholarship from this project.
Conflict of interests: none.
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