Evaluation of the response of cortisol , corticotropin and blood platelets kinetics after laparoscopic and open cholecystectomy

Purpose: To compare the behavior of serum cortisol and ACTH levels and platelet kinetics after laparoscopic and open cholecystectomy. Methods: In this prospective study, 31 patients with symptomatic cholelithiasis submitted to elective cholecystectomy, 17 by the laparoscopic route and 14 by the open route, were compared. Peripheral blood samples were collected on admission of the patient, during anesthetic induction, and 2, 6, 12, 24 and 48 hours after the surgical incision. Platelets were counted in hematoxylin-eosin-stained specimens under a light microscope at 100X magnification. Cortisol and ACTH were measured by chemiluminescence. Results: Cortisol and ACTH levels showed a significant increase (p<0.05) within the first hours after surgery compared to preoperative values. At 2 hours, a significantly higher cortisol concentration was observed in the laparoscopic group compared to the open surgery group (p=0.0365). A return to basal levels during the later postoperative periods (24 and 48 hours) was only observed for ACTH, while serum cortisol continued to be elevated during the same period, being significantly higher in the open surgery group than in the laparoscopic group (p24 = 0.0248 and p48 = 0.032). Different platelet response curves were obtained for the two groups, but their levels were normal at all times studied. No significant difference (p>0.05) between the postand preoperative periods was observed for either group. Conclusion: A hormonal response was observed for both procedures studied, but the surgical stress was higher and longer lasting in open surgery compared to the laparoscopic approach. However, no significant variation in platelet kinetics in response to tissue injury was observed between the two procedures.


Introduction
Over the last few years, laparoscopic cholecystectomy has been increasingly applied as a method of choice for the treatment of patients with conditions such as cholelithiasis due to the current concern in minimizing surgical trauma through a smaller incision in the abdominal cavity, with a consequent reduced exposure [1][2][3] .
Laparoscopic cholecystectomy has been shown to attenuate endocrine-metabolic, immunological and inflammatory responses [4][5][6][7] .Consequently, this approach provides a better clinical outcome for the patient, including a reduction in postoperative pain, better ventilatory function, faster recovery and earlier discharge from the hospital compared to open cholecystectomy [8][9][10][11] .
Therefore, in the present study we evaluated changes in serum cortisol and ACTH levels in order to compare the hormonal response to tissue injury that occurs after laparoscopic and open cholecystectomy.In addition, platelet kinetics was determined during these procedures in view of the fact that these cells participate in the acute phase of the inflammatory response and also because of their fundamental role in spontaneous hemostasis 12 .We did not find any study in the literature evaluating the platelet response in these surgical procedures.

Methods
A prospective study was conducted on 31 patients with symptomatic cholelithiasis without complications, who underwent elective cholecystectomy at the Discipline of Digestive Tract Surgery of the Teaching Hospital, Federal School of Medicine.Patients presenting enzyme alterations or acute cholecystitis were excluded.The patients included in the study were divided into two groups: 17 patients were submitted to laparoscopic cholecystectomy and 14 patients were submitted to open cholecystectomy.The clinical characteristics of the patients including age, gender, weight and physical status are shown in Table 1.There was no significant difference between the laparoscopic and open surgery groups.The patients were submitted to general anesthesia in order to minimize the influence of the procedure on the hormonal response.Blood samples were collected on admission of the patient, immediately before anesthesia, and 2, 6, 12, 24 and 48 hours after the surgical incision (A2, A6, A12, A24, A48 respectively) Platelets were counted in hematoxylin-eosin stained specimens under a light microscope at 100X magnification.Cortisol and ACTH were measured by chemiluminescence.Statistical analysis was performed using the Mann-Whitney U test, with differences being considered statistically significant when p<0.05.

Response of cortisol and ACTH
A significant increase in plasma cortisol (Figure 1) was observed in the laparoscopic group 2 hours after the surgical incision compared to preoperative values (p=0.0365).The open surgery group presented a maximum cortisol peak after 6 hours, whereas in the laparoscopic group the maximum peak was reached 12 hours after the surgical incision.A significant decrease in plasma cortisol concentration was observed in the laparoscopic group compared to the open surgery group 24 and 48 hours after surgery (p=0.0248 and p=0.032, respectively).However, the values observed during these periods were higher than the preoperative levels.
Regarding ACTH (Figure 2), the laparoscopic group presented an expressive increase 2 hours after surgery, followed by a rapid decline at 12 hours.The open surgery group showed a maximum peak 6 hours after surgery, with a decrease in these values close to preoperative levels being only observed 24 hours after the surgical incision.Comparison of ACTH levels with preoperative values only demonstrated a significant difference (p<0.05) at 2 and 6 hours in the two groups.No significant difference in ACTH levels was observed between groups at any time point studied.

Blood platelets kinetics
The absolute platelet counts (Figure 3) were normal (200,000-400,000/mm 3 ) or close to normal in the two groups at all time points studied, with no significant (p<0.05)difference between post-and preoperative values.Also, no significant difference (p<0.05) in platelet count was observed between the laparoscopic and open surgery groups.The mean absolute number of platelets ranged from 189,750 to 214,750/mm 3 in the laparoscopic group, and from 198,000 to 227,000/mm 3 in the open surgery group.

Discussion
The objective of the present study was to determine the alterations in cortisol, ACTH and platelet number in response to surgical stress provoked by laparoscopic cholecystectomy compared to open cholecystectomy.Both procedures caused changes in the hormonal response 13,14 .A significant increase in plasma cortisol and ACTH was observed during the intraoperative period and in the first hours after surgery, an expected response to surgical stress also reported in the literature [13][14][15] .A significant difference in cortisol levels was observed between the laparoscopic and open surgery groups 2, 24 and 48 hours after surgery 16 , with the increase being higher in the laparoscopic group at 2 hours, probably because of the presence of pneumoperitoneum 17 .Similar to other reports 17,18 , an earlier increase in cortisol levels and a faster return to preoperative values were observed for the laparoscopic procedure.In open cholecystectomy, however, cortisol levels continued to be elevated 24 and 48 hours after surgery compared to baseline, indicating a longer lasting response to surgical stress as previously described 19,20 .
In contrast, no significant difference was observed between the groups studied regarding ACTH.Similar the  cortisol response, an earlier increase in ACTH and a faster return to preoperative values were observed during laparoscopic cholecystectomy 21 .However, in contrast to cortisol, ACTH returned to basal levels during the postoperative period in both groups, as also demonstrated in other studies 14,17 .
Platelets play an important role in spontaneous hemostasis, interrupting in a natural manner the hemorrhage resulting from the traumatic rupture of blood vessels.In addition, these cells act on the acute phase of the inflammatory response that occurs in response to tissue injury, releasing vasoactive amines (histamine and serotonin) that are chemical mediators of inflammation 12 .However, we observed no significant difference in the absolute number of these cells in response to the surgical procedure in either group.Other studies have reported that in situations of stress, such as that caused by these surgical procedures, initially only increased volume platelets are mobilized, while an increase in the absolute number of circulating cells is observed after 1 or 2 days 22,23 .

Conclusion
A hormonal response to cholecystectomy occurred in both procedures studied, but the surgical stress was higher and longer lasting in open surgery compared to the laparoscopic approach.However, no significant variation in platelet kinetics in response to tissue injury was observed between the two procedures.

TABLE 1 -
Characteristics of the patients.