Efficacy of thoracic epidural anesthesia for laparoscopic cholecystectomy.

BACKGROUND: Laparoscopic cholecystectomy is performed to minimize the postoperative morbidity and early return to work. This study was planned to evaluate the efficacy and feasibility of thoracic epidural anesthesia for laparoscopic cholecystectomy, so that it can be later used as anesthetic technique in patients when general anesthesia is not feasible.
MATERIALS AND METHODS: Forty-eight adult consented patients of ASA grade I and II of either sex scheduled for elective laparoscopic cholecystectomy were enrolled for thoracic epidural anesthesia with 15 ml of 0.75% ropivacaine and 50 μg fentanyl. Intraoperative hemodynamic parameters and respiratory efficiency were recorded. Intra-operatively patient anxiety, pain, vomiting, hypotension or any other adverse event was managed with appropriate drug regime. Postoperative pain management with epidural analgesia, and bowel recovery were also recorded.
RESULTS: The thoracic epidural anesthesia was effective for laparoscopic cholecystectomy in all except in two patients where conversion to general anesthesia was required. The hemodynamic parameters and respiratory efficiency were maintained within physiological limits. Only 4 patients required treatment for hypotension with vasopressor and 15 patients experienced shoulder pain, which was effectively managed with small doses of ketamine. The midazolam was required only in 11 patients for anxiety. The mean surgical time was 56.8±51.6 min. The 24-hour postoperative epidural infusion for analgesia was effective with limited effects on bowel and bladder function. Postoperatively only 3 patients had an episode of vomiting. There was good surgeon and patient's satisfaction.
CONCLUSIONS: The thoracic epidural anesthesia with 0.75% ropivacaine and fentanyl for elective laparoscopic cholecystectomy is efficacious and has preserved ventilation and hemodynamic changes within physiological limits during pneumoperitoneum with minimal treatable side effects.

INTRODUCTION

Laparoscopic cholecystectomy is advantageous due to reduction of postoperative pain, better cosmetic results with quicker return to normal activities. It is usually performed under general anesthesia with controlled ventilation due to pathophysiological changes of carbon dioxide pneumoperitoneum and extreme of patient positioning. In recent years, advanced laparoscopic surgery has targeted older and high risk sick patients for general anesthesia. In these patients, regional anesthesia offers several advantages with improved patient satisfaction.[1-4] However, this anesthetic approach requires a relaxed and cooperative patient, low intra-abdominal pressure (IAP) to reduce shoulder pain and ventilator disturbances, reduced table tilt with a precise and gentle surgical technique.[5]

Ropivacaine, a long acting local anesthetic, is a better alternative to bupivacaine due to its lower toxicity and greatest margin of safety of all long acting local anesthetics at present.[67] After epidural injection, it shows biphasic absorption with an initial rapid phase half -life of 4.2±0.9 minutes. The total plasma concentration increases during continuous epidural infusion of ropivacaine because of an increase in the degree of protein binding and subsequent decrease in clearance of ropivacaine.[8] Epidural administration of the ropivacaine with fentanyl has been shown to accelerate the onset of sensory and motor blocks without significant fentanyl-related side effects.[9]

Encouraged by these facts, this study was aimed to assess the efficacy of thoracic epidural anesthesia with 0.75% ropivacaine and 50 μg fentanyl for elective laparoscopic cholecystectomy, so later it can be used as anesthetic technique in patients who are at risk for general anesthesia.

MATERIALS AND METHODS

After approval from the Ethical Committee of the Institution and informed consent for the procedure, 48 adult patients aged between 22 and 56 years of either sex with ASA physical status I and II, scheduled for elective laparoscopic cholecystectomy under thoracic epidural anesthesia from January 2010 to March 2011 were enrolled for this prospective study. Patients who were unable to co-operate, had a body mass index >32 kg m2, acute cholecystitis, suspected common bile duct stones, history of cardiac, pulmonary or renal disease, history of drug or alcohol abuse, chronic pain or daily intake of analgesics, and allergy to amide local anesthetic were not included. Patients who preferred general anesthesia and in patients where surgeon suspect technical difficulty or patients had contraindications to perform epidural block were also excluded from the study. Patients were explained during the preoperative assessment about the procedure technique and were assured that any pain, anxiety or discomfort, during surgery would we treated effectively. The surgeons were free to request for general anesthesia if they felt technical difficulty for the surgery.

Anesthesia and surgical technique

In the operating room, an intravenous infusion of 500 mL of Ringer lactate was commenced and base line values of heart rate, mean arterial blood pressure, electrocardiography, respiratory rate and pulse oximetry reading were recorded. All patients were premedicated with midazolam 1 mg, ondansetron 4 mg and metoclopramide 10 mg intravenously.

Thoracic epidural anesthesia was performed in left lateral decubitus position. Under all aseptic precautions, 2 ml of 2% lignocaine with epinephrine was infiltrated at the T10-T11 inter-spinous space and an 18-gauge Touhy needle was introduced in midline to identify the epidural space using ‘loss of resistance’ to air method. The epidural catheter was then threaded and taped in place, leaving 4 cm in epidural space. A test dose of 3 ml of 2% lignocaine with epinephrine 5 μg/ml was injected through the epidural catheter. If no intrathecal or intravascular injection was evident up to 5 min, a bolus dose of 15 ml 0.75% ropivacaine with 50 μg fentanyl was given slowly over 5 min. The level of sensory block, assessed with pin-prick stimulus, covering the area of the proposed incision (T4-5) was confirmed before surgery. If needed, the incremental dose of 2 ml of 0.75% ropivacaine was given. The patients were breathing spontaneously with oxygen supplementation at the rate of 5 L/minutes. The nasogastric tube was inserted to decompress the stomach on surgeon demand. Pneumoperitoneum was established with low pressure carbon dioxide of 10 mm Hg at a flow rate of 1 L/min. After the creation of pneumoperitoneum but prior to gall bladder dissection, 12 ml of 0.25% Bupivacaine was instilled into the right sub-diaphragmatic space and over the gall bladder.[10] Head up and left lateral tilt of the operating table was employed as minimal as possible in order to minimize diaphragmatic irritation. Intra-operatively, the patients were monitored for heart rate, blood pressure, respiratory rate, arterial oxygen saturation (SpO2) and end tidal carbon dioxide (EtCO2). The parameters were recorded at 5 min intervals. Hypotension, defined as a fall in blood pressure by more than 20% of pre-anesthetic value, was managed by rapid crystalloid infusion and/or intravenous bolus of 6 mg mephentermine. Bradycardia (<50 beats/min) was treated with IV 0.6 mg atropine. Respiratory insufficiency was defined as a respiratory rate at or below 8 breaths/min, pulse oximetry value of less than 94% at any given time and/ or subjective breathing difficulty not relieved by reassurance. Duration of pneumoperitoneum as well as surgery was kept minimal. Anxiety was treated with midazolam 2 mg. The ketamine 0.25 mg/kg was given intravenously for shoulder pain. Any conversion of anesthetic or surgical technique was noted with reasons to do so.

Postoperative analgesia was provided as a continuous epidural infusion of 0.2% ropivacaine with fentanyl 2 μg/ ml, at a rate of 10 ml/hour and removed after 24 hours. Pain was assessed using visual analogue score (VAS) of 0 (no pain) -100 mm (worst pain imaginable). The other parameters included pulse rate, arterial blood pressure, headache, nausea, vomiting, pruritis, and retention of urine with bowel recovery. Patients were asked to rank their satisfaction with regards to the anesthetic procedure on a score scale ranging from 0 to 10.[11]

RESULTS

The present study enrolled 48 adult consented patients of either sex (male-12 and female-36) with ASA Grade I and II scheduled for elective laparoscopic surgery under thoracic epidural anesthesia with 0.75% ropivacaine and 50 μg fentanyl. Their average age was 41.8 years. An effective sensory block was developed with average of 15 (12-21) minutes. The median highest level of sensory blockade achieved was at T4-T5, and lower level was L1-L3. The dermatome level of analgesia achieved was satisfactory in all patients [Table 1].

Table 1

Patients demographic data and surgical out come

Transient hypotension was recorded in 8 patients who were treated effectively with one dose of 6 mg IV mephentermine. None of them required continuous pharmacological support. There was no observed change in the respiratory rate. The end tidal carbon dioxide increased over the first 10 minutes from 30.65±4.12 to 35.47±5.3 mm Hg (P<0.002) and declined after deflation. All other observed changes were within physiological limits. The 11 anxious patients needed IV midazolam supplementation and 15 patients complained of shoulder pain which was effectively treated with small doses of IV ketamine while all others were comfortable throughout the laparoscopic cholecystectomy. Only 2 patients required conversion to general anesthesia due to technical difficulty [Table 2].

Table 2

Intraoperative events

Postoperative analgesia was well maintained and intravenous opioid analgesic was not required. Only 1 patient had postoperative hypotension and 3 patients have experienced one or more vomiting episodes. No patient has complained of headache, pruritis and retention of urine. The bowel recovery was not altered [Table 3].

Table 3

Postoperative events

All patients gave an overall satisfaction score 8 or above and all resumed normal activities within few days. Only in 2 patients, the surgeon found technical difficulty for laparoscopic surgery hence conversion to general anaesthesia was done. Average time to discharge was 1.8 days.

DISCUSSION

Epidural anesthesia was considered safe for laparoscopic cholecystectomy without associated respiratory depression as the respiratory control mechanism remains intact to allow the patients to adjust their minute ventilation. Moreover, the respiratory changes are less evident in awaken patients under regional anesthesia and patients maintain an unchanged end tidal carbon dioxide.[12] The central neuraxial anesthesia has been found beneficial usually in patients with significant medical diseases when low intra-abdominal pressure and less degree of patient tilt during surgical procedure is used.[5] The shoulder pain, secondary to diaphragmatic irritation from carbon dioxide pneumoperitoneum, is incompletely alleviated using epidural anesthesia alone and extensive sensory block from T4 to L5 is needed for the laparoscopic procedure.

This present prospective study was aimed to evaluate the efficacy of epidural anesthesia with 0.75% ropivacaine with fentanyl for laparoscopic cholecystectomy. Lack of complications and morbidity encourage us to share our preliminary experience of thoracic epidural anaesthesia for laparoscopic cholecystectomy.

Many researchers have observed that laparoscopic cholecystectomy performed under regional analgesia is advantageous due to reduction of surgical stress response. Avoidance of airway instrumentation and lower incidence of deep vein thrombosis are other few advantages.[1] The low intra-abdominal pressure with low insufflation flow rate contributes only few hemodynamic changes. Critchley et al. reported 29% increase in mean arterial blood pressure after gas insufflation under general anesthesia.[13]

In the present study, the low incidence of right shoulder pain was observed which could be attributed to low intra-abdominal pressure of 10 mm Hg combined with minimal table tilt and the instillation of 0.25% bupivacaine into right sub-diaphragmatic space and over the gall bladder. Van Zundert et al.[14] also noted shoulder and neck pain in 2 of their 6 patients operated under epidural anesthesia. Minai et al. attributed the high incidence of shoulder pain to the physical and chemical stimulation of the diaphragm by pneumoperitoneum.[15] No patient experienced breathing difficulty during abdominal insufflation, perhaps due to low gas pressure flow rate.

During the present study, the hemodynamic changes were also minimal due to preloading with 15 ml/kg of ringer lactate over 20 minutes, low intra-abdominal pressure, minimal table tilt and absence of any cardiovascular disease. The study also did not show any notable events apart from hypotension which was easily treated by vasopressor drugs. The regional sympathetic block have compensated for the increased sympathetic tone resulting from pneumoperitoneum in a head-up tilt position.[16] Although regional anesthesia facilitates the unopposed vagal reflex, but none of our patients suffered bradycardia.

Postoperative nausea and vomiting was reported in 3 patients who were treated with intravenous ondansetron.[17] Low incidence in the present study could be attributed to antiemetic prophylaxis with metoclopramide and ondansetron, avoidance of hypotension, adequate pain control and avoidance of postoperative parenteral opioids medication. At the time of discharge, all patients reported being satisfied with the anesthetic technique, good postoperative pain control and minimal nausea and vomiting.

Bejarano et al. used spinal anesthesia with midazolam sedation for laparoscopic ventral hernia repair and concluded that spinal anesthesia is feasible and well tolerated.[18] Van Zundert et al. stated that segmental spinal anesthesia can be used safely for patients with impaired organ function.[14] Lau et al. also quoted that laparoscopic hernia can be performed successfully under spinal anesthesia.[19]

However, there are several disadvantages of the regional technique due to sympathetic denervation of high regional block which may lead to bradycardia, hypotension and decreased cardiac output. The vigilant monitoring is essential for prevention and treatment. Continuous infusion of low dose epidural analgesia with 0.2% ropivacaine and 2 μg/ml fentanyl provided good postoperative analgesia and no patient demanded for parenteral opioids.[2021]

CONCLUSION

The thoracic epidural anesthesia for elective laparoscopic cholecystectomy is efficacious. The continuous infusion of 0.2% ropivacaine, with fentanyl 2 μg/ml has provided effective postoperative analgesia. Success of the technique necessitates relaxed and co-operative patient and gentle surgical procedure with low intra-abdominal pressure technique.