Laparoscopic colorectal surgery is potentially associated with less surgical trauma, and this might also result in positive effects on the recovery of bowel function (1).
Combined epidural/general anesthesia is widely used for major abdominal surgery with positive effects on postoperative recovery (2) but results in more marked changes of thermoregulation caused by the combined depression produced by both general and epidural anesthesia on the hypothalamic thermoregulatory center and autonomic nervous system (3). Maintaining perioperative normothermia reduces the incidence of surgical wound infection and shortens hospitalization (4). Laparoscopic techniques could potentially reduce heat loss from exposure of abdominal organs at laparotomy and minimize postoperative pain with positive effects on the recovery of bowel function (5). However, little is known about the effects on perioperative hypothermia produced by laparoscopic techniques in patients receiving major abdominal surgery. We therefore conducted a prospective, randomized, controlled study to compare the effects on temperature control and recovery of bowel function in patients undergoing major abdominal surgery with either a laparoscopic or laparotomic technique.
Materials and Methods
With ethical committee approval and written informed consent, 44 ASA physical status I and II patients undergoing elective colorectal resection were studied. Patients with contraindications to epidural catheter placement, younger than 18 yr or older than 75 yr, manifesting obesity (body mass index >25 kg/m), allergies to local anesthetic solutions or opioids, receiving corticosteroids or chronic pain drugs, as well as patients unable to understand the use of patient-controlled (PCA) analgesia were excluded.
The same anesthesia and surgical teams performed all surgical and anesthetic procedures. Using a random sequence of numbers, patients were randomly allocated by the surgical team to receive either a laparoscopic (Laparoscopy group, n = 23) or a traditional laparotomic procedure (Laparotomy group, n = 21).
The day before surgery, all patients received a routine physical examination and were instructed on both the use of the PCA machine and visual analog scale to assess the degree of pain (0 = no pain; 100 mm = worst pain). After standard IV premedication with midazolam 0.3 mg/kg, core temperature was measured using a Foley catheter with indwelling thermocouple disposable probe (Mon-a-therm, Mallinckrodt Medical Inc, St Louis, MO) inserted into the bladder using a sterile technique. Probes and thermometer were calibrated in the temperature range 30°C–40°C, having an accuracy of 0.1°C and a precision of 0.01°C (6). All procedures commenced at 8–10 am, and the operating rooms had controlled laminar flow with room temperature ranging from 21°C to 23°C and a relative humidity of 40%–45%.
Lactated Ringer’s solution (10 mL/kg) was given IV; a thoracic epidural block up to T4 was then induced with 6 to 10 mL of 0.75% ropivacaine and maintained by injecting 50% of the induction bolus every 90–120 min (7). General anesthesia was induced with an IV injection of sodium thiopental (5 mg/kg), fentanyl (1 μg/kg), and atracurium bromide (0.5 mg/kg) and maintained with isoflurane (end-tidal concentrations, 0.4%–1.2%) and a continuous IV atracurium infusion (0.5 mg · kg−1 · h−1). Patients’ lungs were mechanically ventilated maintaining an ETco2 between 35 and 45 mm.
All infused solutions were actively warmed to 37°C (Hot Line™, SIMS Level 1, Rockland, MA). The Laparoscopy group received 4 mL · kg−1 · h−1 of the crystalloid solution, whereas the Laparotomy group received 8 mL · kg−1 · h−1 of the same solution; 3 mL of the same solution were infused for every 1 mL of blood loss. Allogenic red blood cells were given to compensate for blood loss exceeding 20% of the circulating blood volume.
In the Laparoscopy group, CO2 pneumoperitoneum was created and maintained through a periumbilical trocar; patients were then placed in a 30-degree Trendelenburg position according to the surgical procedure (8). Intraabdominal pressure was maintained at 12 mm Hg with computer-controlled insufflation of CO2 heated up to 37°C without active humidification. Open surgery (laparotomy) was performed using a conventional midline laparotomic incision.
Core temperature was recorded every 15 min until discharge from the postanesthesia care unit (PACU). At the last skin suture, the volatile drug was discontinued, residual neuromuscular block antagonized, and 100 mg of ketoprofen given IV. After extubation, the patients were transferred to the PACU where two blankets were placed on the patient. A dedicated anesthesia nurse blinded to the study’s aim recorded blood pressure and heart rate values, Aldrete score, and core temperature every 15 min until achieving readiness for PACU discharge. Criteria for PACU discharge were the presence of a modified Aldrete score ≥9, stable vital signs, pain and nausea controlled, and recovery of a core temperature ≥36°C. The occurrence of shivering, nausea, vomiting, and other undesired side effects were recorded.
Postoperative analgesia consisted of a continuous epidural infusion with 0.2% ropivacaine (infusion rate, 5 mL/h) and 100 mg of ketoprofen IV every 8 h. Rescue analgesia with PCA morphine was also available to the patient (incremental dose, 1 mg; lockout time, 10 min; maximum dose per hour, 4 mg), and total morphine consumption was recorded. The degree of pain was assessed every 12 h with the visual analog scale both at rest and during coughing. The time to first flatus, defecation, and intake of clear liquid was also recorded.
To calculate the required sample size, we took into account the changes in core temperature previously reported during integrated epidural/general anesthesia (3,9). Twenty patients per group were required to detect a 0.5°C difference in the core temperature at the end of surgery between the two surgical techniques accepting a two-tailed α error of 5% and a β error of 20%(10).
Statistical analysis was performed using the program Systat 7.0 (SPSS, Chicago, IL). Normal data distribution was first evaluated using the Kolmogorov-Smirnov test. Anthropometric variables, duration of surgery, morphine consumption, and times to PACU discharge, first flatus, defecation, and intake of clear fluids were evaluated with the Student’s t-tests or the Mann-Whitney U-test based on data distribution. A two-way analysis of variance for repeated measures was used to analyze changes over time in cardiovascular variables, core temperature, and degree of pain at rest and during coughing. The Fisher’s and Scheffe’s tests were used for post hoc comparisons. Sex distribution and incidence of side effects were evaluated with the Fisher’s exact test. A value of P ≤ 0.05 was considered as significant. Continuous variables are presented as mean (± sd) or median (range) according to data distribution. Ordinal data are presented as numbers (%).
No differences in age, weight, height, sex distribution, blood loss, and crystalloid infusion were observed between the two groups (Table 1). The duration of surgery was longer in the Laparoscopy group than in patients receiving laparotomy (Table 1).
Both systolic and diastolic arterial blood pressures decreased from baseline values after the general anesthesia induction. However, patients in the Laparoscopy group showed increased values than those observed in the Laparotomy group (Fig. 1). No surgical problems were reported in either group, and surgery was completed uneventfully in all patients.
Core temperatures decreased gradually throughout the procedures in both groups without differences between the groups (Fig. 2). After transfer to the PACU, core temperature progressively increased in both groups, and recovery of normothermia occurred in all patients within 2 h after surgery. PACU discharge criteria were fulfilled after 75 min (60–120 min) in the Laparoscopy group and 60 min (45–180 min) in the Laparotomy group (P = 0.56).
The degree of pain at rest was lower in the Laparoscopy group only at the 48 h observation time; however, patients of the Laparoscopy group showed better pain control during coughing from the 24th to the 72nd observation times (Fig. 3). Median consumption of PCA morphine during the first 48 h after surgery was 22 mg (2–65 mg) in the Laparotomy group and 5 mg (0–45 mg) in the Laparoscopy group (P = 0.02). The times to first flatus and defecation were shorter in the Laparoscopy group (24 h [16–72 h] and 70 h [24–84 h], respectively) than in the Laparotomy group (72 h [26–96 h] and 96 h [72–144 h], respectively) (P = 0.0005 and P = 0.0005, respectively). The first intake of clear liquid occurred after 48 h (24–72 h) in the Laparoscopy group and after 96 h (90–96 h) in the Laparotomy group (P = 0.0005).
Laparoscopic techniques cause less postoperative pain, shorter hospital stay, and faster return to normal life than conventional laparotomic techniques (11–13). Previous reports also suggested that the use of laparoscopic techniques might improve intraoperative temperature control by reducing heat loss produced by bowel exteriorization during laparotomy (5,14–16). Results of this prospective, randomized, controlled study confirmed previous reports on the positive effects of the laparoscopic technique on postoperative pain control and recovery of bowel function after colorectal surgery but failed to demonstrate any advantage in terms of incidence and severity of perioperative hypothermia, as compared with a control group of patients receiving conventional laparotomy.
Heat redistribution and depression of the hypothalamic thermoregulatory center induce hypothermia during general anesthesia (17), whereas the epidural block further depresses the normal thermoregulatory responses (3,18). Reducing heat loss by minimizing bowel exposure with laparoscopy did not compensate for the severe hypothermia induced by the anesthesia technique. Moreover, the increased ventilation requirements because of the CO2 pneumoperitoneum can further increase heat loss even if patients are ventilated with low-flow rebreathing systems (19,20).
In the present study, CO2 was warmed up to 37°C before abdominal insufflation. However, this did not prevent the heat loss induced by the humidification of the insufflated gas. Other authors reported similar findings and suggested actively humidifying the insufflated gas (21,22).
The reason for using a bladder temperature probe was mainly based on its minimal invasiveness and ease of monitoring core temperature in awake patients before the general anesthesia induction and in the PACU. This might represent a minor shortcoming of the study because of its slightly lower accuracy as compared with tympanic probes (6); however, it has been clearly demonstrated that bladder temperature is a close approximation to pulmonary artery temperature in patients undergoing major abdominal surgery (23,24).
Interestingly, arterial blood pressure values were slightly larger during laparoscopy than laparotomy. This may be related to the use of the 30-degree Trendelenburg position (8). In agreement with this finding, other authors reported slight but significant increases in arterial blood pressure during laparoscopy for gynecological procedures (25) or gastric banding (26).
Laparoscopic surgery also resulted in significant reduction of postoperative pain, with less consumption of rescue PCA morphine after surgery as compared with conventional laparotomy. Even if no differences in inflammatory markers have been demonstrated (27), the larger skin and peritoneum incision, as well as the wider bowel manipulation during laparotomic surgery, can reasonably account for more tissue trauma, resulting in increased analgesic requests as compared with laparoscopic procedures. The increased morphine consumption observed after laparotomy can also account for the delayed recovery of bowel function (28).
In conclusion, this study confirms previous reports on the positive effects of laparoscopic surgery on the degree of postoperative pain and recovery of bowel function. However, the minimal reduction in heat loss produced by reducing bowel exposure during laparoscopy does not compensate for the marked effects on perioperative thermoregulation produced by anesthesia, especially when epidural and general anesthesia techniques are combined. This finding demonstrates once more the crucial relevance of actively warming patients during surgery to prevent perioperative hypothermia, even when a laparoscopic technique is planned.
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