The Effect of Erector Spinae Plane Block on Laparoscopic Cholecystectomy Anesthesia: Analysis of Opioid Consumption,Sevoflurane Consumption,and Cost

Introduction

Cost control is of great importance in the face of today's increasing health expenditures. Anesthesia methods can significantly affect the total cost of surgical procedures. Various cost containment strategies have been suggested in regard to controlling the cost of inhalational anesthetic agents due to their expensive feature. ¹ Inhalation agents constitute the cost of ∼20% of the total anesthetic agents used in patients. ²

Opioids are the other most used drug in anesthesia practice for intraoperative and postoperative analgesia. ³ Because of the cost of the opioid-related clinically meaningful events, modeling the use of opioid-sparing therapies are suggested for reducing health resource utilization and costs. ³

Erector spinae plane block (ESPB) is a recently described new technique for both acute and chronic pain. ⁴ The ESPB is performed by depositing the local anesthetic (LA) in the fascial plane, deeper than the erector spinae muscle at the tip of the transverse process of the vertebrae. ⁴ Each 3.4 mL of injected LA volume is distributed in the craniocaudal fascial plane of one dermatome. ⁵ And also LA agents are known to reduce the minimum alveolar concentration (MAC) of inhalation agents. ⁶ Bilateral ultrasound-guided ESPB leads to effective analgesia and a decreased postoperative opioid consumption in patients undergoing laparoscopic cholecystectomy (LC). ⁷

As mentioned hereunder, there are many studies regarding the analgesic effect of ESPB on LC, but few about the effect of ESPB on cost. In this study, we aimed to evaluate the effect of ESPB on consumption of inhaled agent and opioids at peroperative period for LC.

Materials and Methods

Approval for this prospective observational study was obtained from Kırıkkale University Local Ethics Committee (2019/11, Ref. no: 2019.06.04). Written informed consent was obtained from all patients. Eighty-four American Society of Anesthesiologists (ASA) I–III 18–75 years old patients undergoing LC in the operating theatre at the university hospital were included in this study between October 2019 and November 2019 in accordance with the Declaration of Helsinki. Patients with central nervous system disease, severe cardiovascular system disease, abnormal coagulation parameters, allergy to any of the study drug, infection of the injection area, and obesity (body mass index >35 kg/m²) were not included in the study. Also, cases that started as laparoscopic surgery and returned to open surgery were not included.

Patients were randomly divided into two groups whether the ESP block was performed or not by a computer program as Group ESP (n = 39) in which ESP block was applied at preoperative period and Group non-ESP (n = 41) in which ESP block was not applied at any of time. After standardized monitoring, bilateral ultrasound-guided ESP block (in-plane approach) at T₇ level was applied to the patients in sitting position under midazolam (0.03 mg/kg) sedation in Group ESP.

The ESP block was performed using a 7–18 MHz linear ultrasound probe (Esaote My Lab 6 US Machine, Florance, Italy) and a 22-gauge 100-mm Stimuplex needle (B. Braun, Germany) by experienced anesthesiologist residents who did not involve patients' perioperative anesthesia management. After sterilization of the skin with povidone iodine, the coated probe with sterile sheath was placed 3 cm lateral to the T₇ spinous process. The trapezius, rhomboid major, erector spinae muscles, and the transverse process of vertebrae were displayed. The needle was inserted into the fascial plane on the deep face of erector spinae muscle above the bone shadow of the transverse process. The 20 mL of 0.25% bupivacaine was administered on each side and spread of LA was seen. Then the patients were taken to the operating room.

In both groups (group ESP: patients with ESPB and group non-ESP: patients without ESPB) standardized monitoring (peripheral oxygen saturation [sPO₂], heart rate [HR], noninvasive mean blood pressure [MBP]), and standardized general anesthesia were applied. Propofol 2 mg/kg (i.v.) and fentanyl 1.5–2 mg/kg (i.v.) were administered for induction of anesthesia and 0.6 mg/kg (i.v.) rocuronium was administered to facilitate tracheal intubation. Anesthesia was maintained with 2% sevoflurane in 50% air and 50% oxygen with controlled ventilation in 4 L of fresh gas (FG) flow.

The anesthesia depth was obtained with bispectral index (BIS) monitoring (A-2000, Aspect Medical Systems) as keeping at 40–50 values and was provided consecutive increasing or decreasing sevoflurane concentration in both groups. But if hemodynamic control was not achieved, remifentanil (0.5–1 μg/kg/minute) infusion was administered to patients who did not have sufficient depth. Muscle relaxation was achieved by repeating the muscle relaxant according to the train-of-four ratio (when reached 25%) throughout the operation. The sPO₂, HR, and noninvasive MBP were monitored in all patients. All monitoring parameters were recorded at the 5th, 10th, 15th, 20th, 25th, 30th, 35th, 40th, 45th, 60th, 90th, 105th, and 120th minutes of intubation. MAC values of sevoflurane were also recorded at the same measurement times. Characteristics of the patients (age, gender, and ASA) and anesthesia (anesthesia time, surgical time, total consumption of sevoflurane, and total consumption of remifentanil) were recorded. The inhalational anesthetic (sevoflurane) delivery time was broken down into segments with constant FG flow and volatile anesthetic (VA) concentration settings. Total consumption of sevoflurane amounts were calculated using the formula reported by Biro. ⁸ Each time segment's VA consumption is to be calculated according to this formula ⁸ :

Fluid sevoflurane (mL) = FG flow (mL/dk) ¹  × VA conc (vol %) ²  × anesthesia duration (minute) / saturated gas volume (mL/mL) ³  × 100 (vol %)

For postoperative analgesia, paracetamol 1 g and tenoxicam 20 mg i.v. was given to all patients 30 minutes before the end of the surgery. After gaining muscle strength and spontaneous ventilation, patients were extubated and transferred to the recovery room. Postoperative pain was evaluated by using visual analog scale (VAS) indicating no to mild pain (0–3), medium (4–7), and severe pain (8–10) at postoperative 0th, 1st, 2nd, 6th, 12th, and 24th hours. ⁹ For rescue analgesia during postoperative period, 1 mg/kg tramadol was performed if VAS ≥4/10 and total amounts of consumed tramadol were recorded.

The total consumption amount of sevoflurane, remifentanil, and tramadol was multiplied by the unit price of the drug (milliliter and milligram) for performing cost estimation.

Results

Eighty-four patients were enrolled in the study. Three patients were excluded from the study because of switching to open surgery. So 81 patients were included in the analysis of this study. Characteristics of patients (age, gender, and ASA) and anesthesia (anesthesia time and surgery time) were shown in Table 1. Perioperative monitoring parameters were presented in Table 2. The MAC_mean value was significantly lower in Group ESP than Group non-ESP (P < .001, Table 2). The first postoperative analgesic time was significantly higher in Group ESP (N = 39) than Group non-ESP (N = 41) (P = .02, Table 2). The intraoperative consumed remifentanyl, sevoflurane, and the postoperative tramadol amounts, and costs were significantly higher in non-ESP group (respectively, P < .001, P = .01, and P < .001; Table 3). There were no differences in mean HR, sPO₂, and mean arterial pressure at any time intervals intraoperatively (P > .05). BIS values were similar in both groups (P > .05).

Discussion

In this study the cost of using preoperative ESP block for postoperative analgesia in patients undergoing LC surgery was found to be lower by reducing opioid and inhaled agent consumption in peroperative period.

In recent years, ESP block has become popular in patients undergoing LC for postoperative analgesia.^7,10 In these studies the effect of ESP block on postoperative pain and opioid consumption have investigated. However, we did not find any study in the literature investigating the effect of ESP block administration to general anesthesia on intraoperative analgesic consumption and inhalation agent consumption for LC. The aim of this study was to evaluate the effect of ESP block in terms of cost-effectiveness, intraoperative consumption of inhalation agents, and perioperative consumption of opioids.

General anesthesia is the reversible state of unconsciousness by creating hypnosis, amnesia, antinociception, immobility, and analgesia with pharmacological agents. ¹¹ Balanced general anesthesia is the strategy of the use of combination of different agents to maintain the current anesthetic condition. ¹¹ In balanced anesthesia, unconsciousness is maintained by inhalation agent. Inhaled agent sevoflurane contribute to antinociception by altering perception of nociceptive stimuli. ¹¹ In this approach, the aim is to use as low dose drugs as possible to minimize possible drug side effects. ¹² In this study we used balanced anesthesia and we found that consumption of inhaled agent sevoflurane was lesser in ESP block group. At this point ESP block contributes to multimodal anesthesia application as reducing gas consumption. As it is known, ESP block is the injection of LA agent into the facial plane. When LAs are used in nerve blocks and regional anesthesia, antinociceptive effect occurs by inhibiting excitation of nerve endings or by preventing the formation of action potential in the peripheral nerves. ¹³ Therefore, we thought the consumption of sevoflurane gas, which itself has an antinociceptive effect, was lower in block group due to the antinociceptive effect of the LA agent. There is only one study in the literature investigating the effect of block administration on intraoperative anesthetic inhaled agent consumption. ¹⁴ Kokulu et al. ¹⁴ reported that transversus abdominis plane block applied just after general anesthesia reduced the consumption and cost of desflurane. They suggested that the effect of block occurs by preventing the transmission of sensorial messages to central nervous system and by decreasing effects on the MAC value of inhaled agent. ¹⁴ In this study, we thought that the lower MAC values in the ESPB group were due to the reduction effect of LA.

At the present time, opioids are administered almost exclusively as intermittent boluses or continuous infusions for nociception and postoperative pain during surgery in balanced general anesthesia. ¹¹ Because of concerns about opioid overuse and undesirable side effects, multiple agents are additionally used to reduce opioid use to manage the nociceptive component of anesthesia. In a previous study on the reduction of intraoperative and postoperative opioid consumption by regional anesthesia applications, ultrasound-guided TAP block substantially reduced the perioperative opioid consumption. ¹⁵ In that study, patients without block group received significantly more intraoperative sufentanil and postoperative morphine compared with those in patients with block group. In this study we used ESP, a different regional block type, and similarly, opioid consumptions in perioperative period (intraoperative consumed remifentanyl and postoperative consumed tramadol) were lower in ESP block group. As mentioned earlier, opioid consumption may be reduced due to the antinociceptive properties of LAs.

Cost control in all areas of health care has become a priority. Hospital management should reduce costs without compromising patient safety with careful management. The operating room is one of the main costs of the hospitals. ¹⁶ Anesthesia costs only 5%–6% of surgical procedures per year. ¹⁷ Although this rate seems low, the increasing number of operations performed each year and the variation in used medicine and materials makes anesthesia costs remarkable for the health economy. In the cost-effectiveness study of balanced general anesthesia method versus total intravenous anesthesia method, a lower cost was reported in balanced general anesthesia. ¹⁸ In our study, the balanced general anesthesia was used and the cost effect of ESP block on LC surgery was investigated. Recently, reducing the consumption of expensive anesthestic agents with different strategies have become popular. ¹⁶ In this study, the consumption of inhaled agents as expensive anesthetic agent and consumption of opioids were lower in patients with preoperative regional block under general anesthesia. According to these, the cost of LC under general anesthesia with ESP block was significantly lower than without block.

One of the limitations of the study was that we could not measure the blood levels of LA, because systemic effects of LAs should be considered at this point. The second was that we could not assess the effect of block application on postoperative discharge period and thus the cost of hospital stay. In the future studies, different surgical procedures and different blocks can be evaluated with considering the whole hospitalization process and treatment per patient.

In conclusion, this study showed that performing preoperative ESP block for LC decreased the consumed amount and cost of inhaled agents and opioids in the perioperative period of surgery. And ESP block is a method that contributes to the basic principles of multimodal anesthesia for patients undergoing LC.