Abstract
Background
Surgical stress can induce postoperative systemic leukocytic alterations, including leukocytosis, neutrophilia, or lymphopenia. The present study investigated whether the anesthetic technique could affect the leukocytic alterations, including neutrophil-to-lymphocyte (N/L) ratio, after gynecologic laparoscopy.
Methods
Forty patients scheduled for laparoscopy-assisted vaginal hysterectomy were randomly assigned into two groups: PR group, which received total intravenous anesthesia with propofol and remifentanil, and S group, which received inhalational anesthesia with sevoflurane. Differential counts of leukocytes with N/L ratio of peripheral blood were obtained just before induction (T1), at the end of surgery (T2), 2 hours after surgery (T3), and 24 hours (T4) after surgery.
Results
Significant increase in total leukocytic count, neutrophil count, and N/L ratio, and decrease in lymphocytic count were observed at all time points after surgery in both groups. N/L ratio was significantly lower in group PR compared with group S at T3. The increase of N/L ratio in contrast to the value at T1 was significantly lower at T2 and T3 in group PR compared with that of group S.
Conclusion
Total intravenous anesthesia with propofol and remifentanil resulted in transient but salient leukocytic alterations in the peripheral blood in terms of N/L ratio compared with inhalational anesthesia with sevoflurane in laparoscopy-assisted vaginal hysterectomy.
Keywords
Anesthesia, inhalation; Anesthesia, intravenous; leukocytes; lymphocytes; neutrophils;
1. Introduction
Systemic leukocytic alterations, including leukocytosis, neutrophilia, and lymphopenia, may occur in response to surgery by various hormones, cytokines, and acute-phase reactants; apoptosis of lymphocytes; or inhibition of apoptosis of neutrophils.1, 2 It is well known that the production of immune mediators is associated with the extent of surgical trauma.3, 4, 5 This kind of immune response is known to be influenced by the anesthetic technique.6, 7, 8, 9 Previous studies have shown that the serum levels of immune mediators, such as stress hormones or cytokines, are significantly lower with total intravenous anesthesia (TIVA) than with inhalational anesthesia.6, 8, 9 Furthermore, cellular immunity is less suppressed with TIVA.7 However, the comparison of the effects on systemic leukocytic alterations, especially concerning neutrophil-to-lymphocyte (N/L) ratio after surgery, between TIVA and inhalational anesthesia has not been worked out.
Although the significance of systemic leukocytic alterations as a signifier of inflammatory response is relatively uncertain, the impact of total leukocytic count, differential count, or N/L ratio on the outcome of cancer patients has been well demonstrated.10, 11, 12, 13 Furthermore, postoperative lymphopenia was demonstrated to be related to increased susceptibility to postoperative infection.14 The measurement of the leukocytic alterations, including N/L ratio, might be a useful method to assess the inflammatory response after surgery besides surrogating for infection and prognosis. Furthermore, in contrast to other sophisticated tests for immune mediators, such as interleukin measurements, leukocytic count of peripheral blood with N/L ratio is a simple and inexpensive test as a routine workup in the clinical practice. Therefore, we tried to evaluate whether the anesthetic technique might influence the leukocytic count of peripheral blood, differentiation, and N/L ratio after laparoscopy-assisted vaginal hysterectomy (LAVH).
2. Methods
After approval by our institutional review board and obtainment of written informed consent from all patients, 40 American Society of Anesthesiologists functional classification Class I or II female patients, 40–60 years, undergoing LAVH, were enrolled in this prospective randomized controlled study. Patients were randomly assigned to two groups to receive either TIVA with propofol and remifentanil (n = 20) or inhalational anesthesia with sevoflurane (n = 20) having recourse to Internet-based computer program www.randomizer.org. The patients with a history of endocrine disease inclusive of diabetes mellitus, morbid obesity (body mass index > 35 kg/m2), recent chemotherapy, chronic use of steroid, use of analgesic, or immunosuppressant use were excluded from the study.
No premedication was given. Intraoperative monitoring items included noninvasive blood pressure, heart rate, electrocardiography, pulse oximetry, oropharyngeal temperature, and end-tidal CO2. To ensure similar anesthetic depth during surgery, bispectral index (BIS) was maintained within 35–45 in both groups. Anesthesia was induced with propofol and remifentanil (effective-site concentration of 4.0–6.0 μg/mL of propofol and 3.0–5.0 ng/mL of remifentanil to maintain the BIS less than 45 until intubation) in the group PR. In patients of group S, anesthesia was induced with sevoflurane in oxygen through a face mask conveyed by semiclosed circuit system with a total gas flow of 4 L/min. The concentration of sevoflurane was initially 1% and then increased slowly until the end-tidal sevoflurane concentration had reached 2 MAC for endotracheal intubation.
Anesthesia was maintained with 2–4 ng/mL of remifentanil and 3–5 μg/mL of propofol in group PR, whereas in group S, it was maintained with sevoflurane in O2. The mean blood pressure was kept around 80% of the preoperative value and the BIS value less than 45 during the surgery. In group S, labetalol or esmolol was administered to maintain the mean blood pressure within 80% of the baseline. No opioids were given for the maintenance of anesthesia in group S. Rocuronium 0.8 mg/kg was administered to facilitate tracheal intubation. To maintain controlled ventilation, rocuronium was given intermittently as guided by train-of-four stimulation. Fluid replacement was made possible with lactated Ringer’s solution given at a rate of 6 mL/kg/h during surgery. Voluven® (Voluven, Fresenius Kabi, Bad Homburg, Germany) was administered at 8 mL/kg if blood loss was more than 300 mL. At the end of surgery, neuromuscular blockade was reversed with pyridostigmine and glycopyrrolate (0.3 mg/kg and 0.015 mg/kg, respectively). All patients were operated on by the same team of surgeons with identical surgical techniques. The surgeons were blind to whether the patients were receiving TIVA or sevoflurane. Postoperative pain control was made possible with intravenous patient-controlled analgesia (IV-PCA) programmed at a basal rate of 15-μg/h fentanyl with a bolus of 15 μg and a lockout time of 10 minutes. IV-PCA was maintained for a maximum duration of 3 days. When pain was inadequately controlled with IV-PCA, additional opioid (meperidine) or nonsteroidal anti-inflammatory drugs (NSAIDs) was given for succor. The IV-PCA and consumptions of analgesics were recorded and compared between the two groups. The side effects of pain medications, including those of IV-PCA, were recorded. Blood was sampled from a peripheral vein for total leukocytic count, differential count (neutrophils and lymphocytes), and N/L ratio. The time points for sampling blood were as follows: just before induction of anesthesia (T1), at the end of surgery (T2), 2 hours after surgery (T3), and 24 hours after surgery (T4). Neutrophil and lymphocyte counts were derived from differential percentages of leukocytes measured by automatic cell counters (ADVIA 2120; Siemens Healthcare Diagnostics, Deerfield, IL, USA). The obtainment of N/L ratio was entrusted to one of our authors (H.S. Jin) who was blinded to the samples from whichever group for the calculation of absolute counts of neutrophils and lymphocytes. The postoperative complications of infections, including wound infection, were assessed.
The sample size was determined based on the preliminary study. A power analysis was performed with a Type I error of 0.05 and a power of 80%, indicating that at least 17 patients should be recruited for each group. For this calculation, we assumed the mean difference of 2.0 of N/L ratio between the groups after surgery to be significant. To compensate for possible dropout, 20 patients were enrolled in each group. Statistical analysis was conducted by using Sigma Stat for Windows 3.1 (SPSS Inc., Chicago, IL, USA). According to the normality of variables, Student t test or Mann-Whitney rank-sum test was used. Categorized variables were analyzed by Chi-square or Fisher’s exact test. Counts of total leukocytes, neutrophils, and lymphocytes, and N/L ratio within the groups were analyzed by repeated-measures analysis of variance with Bonferroni correction. Comparison of total leukocyte, neutrophil, and lymphocytes counts and N/L ratio between the two groups at all time points was performed with Student t test or Mann-Whitney rank-sum test as appropriate. All data were expressed as mean [standard deviation (SD)], median (ranges), or number of patients, as appropriate. A p value <0.05 was considered as significant.
3. Results
There were no significant differences between the two groups regarding patient characteristics or perioperative data (Table 1). The estimated blood loss during surgery in both groups was comparable. Only one patient in group PR received 1 unit of packed red blood cells. A mean (SD) end-tidal sevoflurane concentration during surgery was 2.2 (0.3) volume % in S group, and mean (SD) effect site concentration of propofol and remifentanil during the same period was 4.4 μg/mL (0.4 μg/mL) and 2.6 μg/mL (0.6 μg/mL), respectively, in PR group to maintain the target BIS range. The average BIS values were not different between the two groups (38.5 ± 4.5 vs. 38.2 ± 4.7, p = 0.838). There was no significant difference of total rocuronium requirement during the surgery (54.2 ± 4.6 mg vs. 56.3 ± 3.9 mg, p = 0.642) between groups PR and S. The total amount of postoperative analgesic consumption of ketoprofen and meperidine, inclusive of fentanyl for IV-PCA. The incidence of side effects related to opioids was not significantly different between the two groups (Table 1). There was no incidence of wound problem or systemic infection in both groups.
Regarding systemic leukocytic alterations affected by surgical stress, as compared with preinduction values, significant increases in counts of total leukocytes, neutrophils, and N/L ratio, and decrease in lymphocyte count were observed at the end of surgery, 2 hours after the surgery, and 24 hours after the surgery, regardless of the anesthetic types (Table 2, Fig. 1). Regarding intergroup comparison, there were no statistically significant differences in absolute number of total leukocytes, neutrophils, and lymphocytes between the two groups at all time points. Although there were no significant differences of absolute numbers of neutrophils and lymphocytes between the two groups, the N/L ratio (7.87 ± 2.80 vs. 10.24 ± 3.35, p = 0.02) in group PR was significantly lower than that of group S at T3 (Table 2, Fig. 1). Regarding the changes of values of total leukocytes, neutrophils, lymphocytes, and N/L ratio at T2, T3, and T4 from baseline values at T1, we observed significant intergroup differences at T2 and T3 (Table 3). There was significantly lesser increase of total leukocytes (p = 0.017), neutrophil counts (p = 0.003), and N/L ratio (p = 0.021) at T2 in group PR compared with those in group S. Significantly lesser decrease of lymphocytes (p = 0.018) and increase of N/L ratio (p = 0.023) at T3 were observed in group PR compared with those in group S (Table 3).
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4. Discussion
The results of the present study indicated that significantly lower N/L ratio could be achieved at 2 hours after surgery under propofol and remifentanil TIVA, in comparison with sevoflurane anesthesia. Considering the changes of N/L ratio from the preinduction values, there was a significant difference between group PR and group S at the end of surgery and 2 hours after surgery.
Suppression of cellular immunity is a major inflammatory host response to surgical stress, which may be deleterious to host defense mechanism along with overproduction of inflammatory mediators. The significant increase of neutrophils and decrease of lymphocytes were supposed to be a predictor of postoperative infection.14 These leukocytic alterations were also proven to be associated with inflammatory mediators like interleukin-6.15 In addition to the change of total leukocytic count, alterations of subtype leukocytes, such as neutrophilia and lymphopenia, and increased N/L ratio as well have been proved to be associated with morbidity or mortality of patients with carcinoma, cardiovascular disease, or chronic renal failure in previous studies.10, 11, 12, 13, 16, 17, 18, 19, 20 Particularly, an elevated baseline N/L ratio in peripheral blood has been suggested as a surrogate symbol to signify poor survival in patients with various types of cancers.10, 11, 12, 13, 19 The N/L ratio not only provides the information of patient’s immune status but could also be a predictor of morbidity in the postoperative period. Furthermore, leukocytic count of peripheral blood with measurement of N/L ratio is an inexpensive and simple test in clinical practice.
Lymphopenia represents immunodepressive status, thus indicating the increased susceptibility to infection.14 A previous study reported that neutrophils might inhibit the immune system.13 Neutrophils could suppress the cytolytic activity of lymphocytes and natural killer cells, and activate T cells in the coculture of neutrophils and lymphocytes in normal healthy donors, and the degree of suppression is proportional to the number of neutrophils added.13 To our knowledge, there is, so far, no study comparing the effects of elevation of neutrophils and decrease of lymphocytes. Therefore, it is unclear whether their influence on immune system is similar or not, though the elevation of neutrophils seems to contribute more in the alteration of the N/L ratio than the decrease of lymphocytes in the present study.
The N/L ratio could be the surrogate for both suppression of cellular immunity by lymphocytes and activation of inflammatory response characterized by neutrophilia. The N/L ratio will be increased if the cellular immunity is suppressed and marked neutrophilia develops. Therefore, we define the favorable pattern of systemic leukocytic alteration as lesser impairment of cellular immunity measured by lymphocytic count and lesser activation of inflammatory response measured by neutrophil count. In other words, we could define the favorable pattern of systemic leukocytic alteration as the lesser value of N/L ratio.
There is no definite clinical critical value for the ratio of neutrophil to lymphocyte so far. However, the cutoff value from previous study showed the N/L ratio of 2.5 as the prognostic value of advanced gastric cancer.13 Another study evaluating the prognostic value of preoperative N/L ratio in patients undergoing coronary artery bypass grafting reported that N/L ratio in the high quartile (more than 3.36) represented low survival rates.20 Neal et al19 stated that N/L ratio greater than 5 was significant in overall survival in patients with resectable colorectal liver metastasis, but was not independently significant. As all these values are concerned with the prognosis of patients, we cannot interpolate these values into the present study. We can only postulate that the higher N/L ratio may have worse influence on the immune system. Further studies are required to determine the significance of N/L ratio as a surrogate for immune system and real clinical cutoff for the value of N/L ratio.
Strategies for restoration of suppressed immunity may contribute to ameliorate postoperative adverse reaction, like wound infection in surgical patients. By and large, anesthesia can reduce the surgical trauma-induced stress response. To investigate the effect of anesthetics per se on the immune competence, multimodal anesthetic techniques have been investigated. TIVA of various regimens has been shown to suppress adverse adrenergic, metabolic, or immunologic responses in the postoperative period compared with various inhalational anesthetics.6, 7, 8, 9 Although TIVA with propofol and remifentanil has become popular, no studies have been performed focusing on its effect on the N/L ratio in comparison with inhalational anesthesia with sevoflurane. Although the type of surgery was a minor one in the present study, we found a significantly lower N/L ratio 2 hours after surgery in the TIVA with propofol and remifentanil compared with inhalational anesthesia with sevoflurane. Similar to our finding, TIVA with propofol and sufentanil compared with sevoflurane anesthesia for partial discectomy decreased the acceleration of lymphocytic apoptosis in a previous study.8 The feature of cytokine response9 and T helper 1 (Th1) and T helper 2 cell ratio (Th1/Th2)7 after a major surgery showed that TIVA attenuated the surgical stress-induced adverse immune response better than inhalational anesthesia.
From the results of the present study, the influence of TIVA versus inhalational anesthesia on leukocytic alterations after surgery was shown to be transient. In group PR, the decrease of N/L ratio was less than that in group S only at 2 hours after surgery. Although it was revealed that the preoperative values were significantly different from those measured at the end of surgery and 2 hours after surgery, the effect was transient. However, as the magnitude of response of peripheral leukocytes has been suggested to be proportional to the extent of surgical trauma,3, 4, 5 it would be postulated that this transient effect might be greater and prolonged when the patient is immune compromised or the patient undergoes a major surgery.
There are several limitations in the present study. First, there might be other confounding factors explaining the difference of N/L ratio between the groups. Although we controlled the depth of anesthesia in both groups, the difference in degree of pain control during the surgery might have contributed to the difference of leukocytic alterations after surgery. Also, the individual difference of difficulty of surgery might not have been well controlled even though the time of surgery was similar and the surgical team was unique. Second, the choice of minor surgery with lower complication rate might have been unable to show greater or prolonged difference of leukocytic alterations between groups. Third, the follow-up period being limited to postoperative 24 hours might not be long enough to evaluate the effect of anesthetic technique on the immune response to surgery. A previous study on evaluating the subpopulation of helper T lymphocytes reported that the effect of an anesthetic could last very long even up to postoperative Day 7.7 Fourth, we used esmolol or labetalol instead of opiate to control the patient’s blood pressure in group S. This kind of anesthetic strategy might be a violation to the principle of balanced anesthesia and our routine clinical practice.
In conclusion, our data showed that TIVA with propofol and remifentanil compared with inhalational anesthesia with sevoflurane could favorably modify the leukocytic alterations, including neutrophil-to-lymphocyte ratio in peripheral blood during the postoperative period of LAVH.