Preoperative Esketamine Alleviates Postoperative Pain after Endoscopic Plasma Adenotonsillectomy in Children

Abstract

Objective: We aimed to investigate preoperative esketamine alleviating postoperative pain in children after endoscopic plasma total adenotonsillectomy.

Methods: We recruited 200 children with adenotonsillar hypertrophy at Wuhan Children’s Hospital between September 2021 and April 2022. The children were randomly assigned to receive preoperative esketamine (ESK group) or fentanyl (FEN group). The primary endpoint was serum c-fos and c-jun levels. The secondary endpoints were face, legs, activity, cry, and consolability (FLACC) score and adverse events.

Results: After surgery, c-fos and c-jun mRNA levels were increased significantly in both groups. Postoperatively, c-fos and c-jun mRNA levels were higher in FEN group compared with the ESK group (P<0.05). The FLACC scores were higher in the FEN group compared with the ESK group at 1 and 24 hours after surgery (P<0.05). Prediction probability (P_k) values indicated that c-fos and c-jun mRNA levels were quantitative predictors for early postoperative pain and stress reaction after surgery.

Conclusions: Esketamine-based anesthesia (1mg/kg) can alleviate postoperative pain and regulate the inflammatory reaction in children undergoing endoscopic plasma adenotonsillectomy.

Tonsillectomy is one of the commonly performed surgical procedures in children, yet pain post tonsillectomy can be substantial and prolonged. Recognition of under-treatment of pain by caregivers and inadequate education led the American Academy of Otolaryngology-Head-Neck Surgery to include in its 2019 update to the Clinical Practice Guideline Tonsillectomy in Children a recommendation advising providers to:

“counsel patients and caregivers regarding the importance of managing post-tonsillectomy pain as part of the perioperative education process, and recommending they should reinforce this counseling at the time of surgery with reminders about the need to anticipate, reassess, and adequately treat pain after surgery.”¹

Opioid analgesics have been used by humans for several thousand years, but opioid analgesics have many side effects, such as nociceptive sensitization, respiratory inhibition, nausea, and other gastrointestinal side effects.^2-4 Non-steroidal anti-inflammatory drugs (NSAID, specifically ibuprofen), once avoided by many otolaryngologists, have been widely adopted and accepted as safe. However in those age >12 years and with a history of recurrent tonsillitis, NSAIDs were associated with increased bleeding risk. Patients experiencing hemorrhage were significantly more likely to require transfusion if ibuprofen was received.⁵ The 2019 update of the American Academy of Otolaryngology-Head & Neck Surgery’s Clinical Practice Guideline softened its prior recommendation against ketorolac stating, “Ketorolac use with tonsillectomy remains controversial and dependent on provider preference.’⁶

Ketamine has a chiral structure consisting of two pure optical isomers, named S- and R-ketamine, with each racemate composed of both isomers in equal amounts. The anesthetic potency of the S(+)-isomer is approximately three or four times that of the R(−)-isomer.⁷ Esketamine, S(+)-isomer, as the pure dextrorotatory enantiomer of ketamine, has been available for clinical use in analgesia and anesthesia from the early 1990s. Esketamine administration during or prior to surgical operations has been used for a more favorable postoperative outcome, primarily due to its actions to reduce the production of excess proinflammatory cytokines in vivo.⁸ The anti-inflammatory effects of ketamine have been observed when the drug was administered prior to and following an immune stimulation, indicating that ketamine may be able to prevent exacerbation of inflammation and also reduce existing inflammation.⁹ Upon this basis, this trial further investigated the influences of anesthetic induction of esketamine on perioperative stress and inflammatory responses and postoperative analgesia of patients.

Materials and Methods

Study Design and Patients

This was a randomized controlled clinical trial. Patients with adenoidal and tonsillar hypertrophy were recruited at the Department of Otorhinolaryngology of Wuhan Children’s Hospital between September 2021 and April 2022. The surgeons and anesthesiologists of the operations were the same groups, as they were competent and qualified. The study was approved by the ethics committee of the Wuhan Women and Children Health Care Center. Informed consent was signed by the legal guardians.

The inclusion criteria were:

• 1)3 to 7 years of age;
• 2)diagnosed with obstructive sleep apnea-hypopnea syndrome (moderate or less: 1≤apnea-hypopnea index [AHI] ≤10) with or without hypoxemia (moderate or less: 75%≤ blood oxygen saturation [SpO2] ≤ 92%);¹⁰
• 3)tonsillar hypertrophy; and
• 4)met the sleep-disordered breathing surgical criteria for adenotonsillectomy.
• 5)ASAII~III

The exclusion criteria were:

• 1)participated in another clinical trial within 4 weeks before enrollment;
• 2)history of long-term narcotic use or esketamine administration;
• 3)allergy to opioids or esketamine;
• 4)heart diseases (degree II or more with cardiac functional insufficiency);
• 5)with severe hypertension;
• 6)with mild to moderate hypertension, but blood pressure higher than 140/90 mmHg before medication;
• 7)hepatic or renal indexes higher than two folds of the upper limit of normal);
• 8)drug dependency history;
• 9)dehydration (decreased peripheral perfusion, deep breathing, decreased skin turgor, high urea, low pH, and/or large base deficit);
• 10)developmental retardation (Figure 1)

Figure 1.

Study flowchart

Randomization and Grouping

The patients were randomized using sequential sealed envelopes. When one child was entered into the study, the envelope was opened by a designated supervisor, and the child was randomized (1:1) to one of two groups. The children were given a random ID number. Only the ID number was used in all study paperwork and database. The two groups were: 1) fentanyl-induced anesthesia (FEN group) or 2) esketamine-induced anesthesia (ESK group). Fentanyl was used for postoperative continuous analgesia in two groups. This was a single-blind trial. Only the patients and their parents did not know the grouping. The face, legs, activity, cry, and consolability (FLACC) score, Baxter Retching Faces (BARF) score, and Steward recovery scale were assessed by a single anesthetist who did not participate in the operations and was blind to grouping.

Anesthesia Protocol

Both groups of children were fasted from solid foods for 8 hours prior to the procedure; clear liquids were permitted until 2 hours prior to admission to the operating room (OR). Atropine was intramuscularly injected at 0.02 mg/kg 30 minutes before operation for all patients. A total of 0.01 mg/kg penehyclidine hydrochloride (Avanc Pharmaceutical Co., Ltd., Jinzhou, China) was administered intravenously to all children ante-aesthetic admission. Intravenous induction of anesthesia started using midazolam (0.05 mg/kg; Enhua Pharmaceutical Group Co., Ltd., Xuzhou, China), remifentanil (1 ug/kg; Yichang Humanwell Pharmaceutical Co., Ltd., Yichang, China) and propofol (4 mg/kg ; Kelun Pharmaceutical Co., Ltd., Chengdu, China) intravenously injected 3 to 5 minutes before operation, with fentanyl (2 ug/kg; Yichang Humanwell Pharmaceutical Co., Ltd., Yichang, China) (FEN group) or esketamine (1 mg/kg; Hengrui Pharmaceutical Co., Ltd., Lianyugang, China) (ESK group), followed by oxygen inhalation. Cisatracurium (0.05 mg/kg; Hengrui Pharmaceutical Co., Ltd.,Lianyugang, China) was injected intravenously, and tracheal intubation was conducted after assisted respiration for 3 minutes. Propofol 4-12 mg/kg/h and remifentanil 3 to 6 ug/kg/h were infused continuously to sustain anesthesia. Hydroxyethyl starch was injected at 10 ml/kg/h to sustain circulation stability. All operations were performed by an experienced attending otolaryngologist. Mechanical ventilation was used, and the tracheal tube was removed under vacuum during the recovery period, followed with immediate clearing of secretions and residual blood in the oropharynx. No perioperative steroids were used. Tropisetron (0.1 mg/kg, Southwest Pharmaceutical Co., Ltd., China) was administered intravenously to the patients 30 minutes prior to the end of surgery. Each child was tested for c-fos and c-jun mRNA before surgery (after atropine intramuscular and vein detained needle) as the baseline. The patients were observed for 1 hour before the patient-controlled intravenous analgesia (PICA) was given to the patients (fentanyl at 6 ug/kg/d using a Apon electronic analgesia pump: Apon Co., Ltd, China). The drug was diluted in normal saline to 100 ml and continuously injected at 4 mL/h for 24 hours.

Observation Parameters

Blood pressure, electrocardiogram, heart rate, and SpO₂ were monitored anti- and post-operation. The FLACC scores were determined. FLACC varies from 0 to 10, and < 5 is considered as satisfying analgesia. BARF scores were evaluated at 1 hour post operation. BARF varies from 0 to 10, and < 5 is considered as mild nausea. The Steward recovery scale was used to evaluate the degree of awakening in the anesthesia recovery room. The FLACC score, BARF scores, and Steward recovery scale were assessed by a single anesthesiologist who did not participate in the operations and was blind to grouping. The patients stayed at the post-anesthesia care unit (PACU) at least 1 hour for evaluation.

Quantitative Real-Time Polymerase Chain Reaction

The relative transcription levels of c-fos mRNA, c-jun mRNA¹³ and β-actin were determined by fluorescence quantitative Real-Time Polymerase Chain Reaction (RT-PCR) before surgery, and 15 minutes and 1 hour after surgery using peripheral blood serum to calculate the change of the values at 15 minutes and 1 hour to the baseline values as the relative serum concentration of c-fos and c-jun, respectively. Total RNA was extracted using Trizol (Invitrogen Inc., Carlsbad, CA) and assessed by electrophoresis. The amount and purity were determined by ultraviolet spectrophotometry. Total RNA (1.0 μg) was denatured at 65°C for 5 minutes and cooled, and the M-Mulv reverse transcriptase was added. The total reaction volume was 20 μL. The mixture was incubated at 42°C for 60 minutes before inactivation at 85°C for 5 minutes. The conditions for RT-PCR were: 1) denaturation at 95°C for 30 seconds; 2) 40 cycles of denaturation at 95°C for 15 seconds and extension at 58°C for 20 seconds; and 3) 72°C for 90 seconds.

The relative amount of PCR products was calculated by the 2^−ΔΔCt method. The primers were: c-fos, forward 3′-AGTT-CATCCTGGCAGCTCAC-5′ and reverse 5′-TGCTGCTGAT-GCTCTTGACA-3′ (204 bp); β-actin, forward 3′-GTC-ACCAACTGGGACGACAT-5′ and reverse 5′-GAG GCGTACAGGGATAGCAC-3′ (209 bp). c-jun, forward 3′-AACTCCCGTAGCAGTATCTTCCAGCAAAGG-5′ and reverse 5′-GAACCCCTCCCTGCTCATTCTGTCACGTTC-TT-3′(315bp); β-actin, forward 3′-GACTTAGAAACCT-CATGCGACCTA-5′ and reverse 5′-AAATTGAAAGTTAAC TTATGCACGC-3′(623 bp).

Endpoints and Follow-up

The primary endpoint was the relative transcription levels of c-fos and c-jun. The secondary endpoints were FLACC score and adverse events. The patients were monitored for 1 hour after operation in the anesthesia recovery room, and they were evaluated at 1 and 24 hours after operation. The adverse events were recorded by questioning the patients and their parents and by physical examinations. The awakening time was defined as from the start of extubation to time the Steward score reached 6 in the anesthesia recovery room.

Statistical Analysis

The sample size was calculated by online statistic software https://www.cnstat.org/samplesize/ with two-sided α of 0.05, power of 80%, and mean reduction of pain intensity after treatment of 7±1.8 in the ESK group and 6±2 in the FEN group. The estimated sample size was at least 58 patients for each group. Assuming a drop-out rate of 20%, 70 patients were needed for each group.

SPSS 17.0 (IBM, Armonk, NY) was used for statistical analysis. Continuous data in accordance with the normal distribution (tested with the Kolmogorov-Smirnov test) were presented as mean ± standard deviation (SD). Intergroup comparisons were performed using repeated measures analysis of variance (ANOVA) and Tukey’s post hoc test. Categorical data were presented as frequency (percentage) and were analyzed using the chi-square test. The correlations were analyzed using the Pearson method. The prediction probability (P_k) of c-fos mRNA and c-jun mRNA levels to the FLACC score was calculated using the P_k MACRO software.¹⁴ Two-sided P values <0.05 were considered statistically significant.

Results

Patients

A total of 200 patients were identified for possible inclusion from September 2021 to April 2022. Among them, 44 patients were excluded according to the inclusion and exclusion criteria (13 for severe sleep apnea-hypopnea syndrome, 18 for mild symptoms and no need for surgery, 2 for mental development disorder, one for participation in another clinical trial, 4 for hepatic or renal dysfunction, and 6 for other reasons). The remaining 156 patients with confirmed moderate or less adenotonsillar hypertrophy who were randomized into the two study groups. Of these, 39 patients were withdrawn for the following reasons: massive hemorrhage (n=1); teeth, oral mucosa, or tongue injury (n=2); insufficient blood sampling for c-fos measurement (n=9); inappropriate timing of blood sampling (n=6); inappropriate handling of blood (n=8); RT-PCR technical failure (n=5); and loss to follow-up (n=8). The 124 patients who completed the study were included in the final analysis. There were no significant differences between the two groups regarding baseline characteristics, heart rate, blood pressure, and SpO₂ before and after anesthesia (Tables 1 and 2).

Table 1.

General characteristics of the two groups before analgesia

Variable	ESK (n = 63)	FEN (n = 61)
Gender (boy/girl)	34/29	37/24
Age (years)	5.15±2.59	5.54±2.60
Body Mass Index	18.67±0.91	17.32±0.84
ASA	I-II	I-II

Table 2.

HR, BP, and SpO₂ comparison among the two groups before and after extubation

Variable	ESK (n = 63)	FEN (n = 61)
HR (bpm)
Before	97±11	95±13
Extubation	108±25	101±18
Postoperative 1h	101±14	90±17
Mean arterial pressure (kPa)
Before	13.3±0.9	13.6±0.7
Extubation	11.4±1.1	10.5±1.2
Postoperative 1h	11.9±0.9	10.1±1.1
SpO2 (%)
Before	97.8±1.9	96.2±1.6
Extubation	97.9±1.2	97.5±1.8
Postoperative 1h	95.8±2.2	95.5±2.7

HR, heart rate; BP, blood pressure; SpO₂, blood oxygen saturation; ESK, esketamine; FEN, fentanyl

C-fos and C-jun mRNA Levels

After surgery, c-fos mRNA and c-jun mRNA levels significantly increased in both groups (Tables 3 and 4). Postoperatively, the change of c-fos mRNA and c-jun mRNA levels relative to the baseline were higher in the FEN group compared with the ESK group (P<0.05).

Table 3.

Comparison of the relative serum c-fos mRNA levels among the two groups (mean ± SD).

Group	n	Postoperative Time
		15 min	1 hour
ESK	63	0.97±0.86*	4.71±1.05#&
FEN	61	2.15±0.24	6.29±0.51♦

^*P<0.05 ESK vs. FEN at postoperative 15min

^#P<0.05 ESK vs. FEN at postoperative 1hour

^&P<0.05 ESK group postoperative 1hour vs. postoperative 15 min

^♦P<0.05 FEN group postoperative 1hour vs. postoperative 15 min

ESK, esketamine; FEN, fentanyl

Table 4.

Comparison of the relative serum c-jun mRNA levels among the two groups (mean ± SD).

Group	n	Postoperative Time
		15 min	1 hour
ESK	63	0.30±0.90*	0.71±0.79#&
FEN	61	0.52±0.20	I.07±0.48♦

^*P<0.05 ESK vs. FEN at postoperative 15min

^#P<0.05 ESK vs. FEN at postoperative 1hour

^&P<0.05 ESK group postoperative 1hour vs. postoperative 15 min

^♦P<0.05 FEN group postoperative 1hour vs. postoperative 15 min

ESK, esketamine; FEN, fentanyl

FLACC Score

Table 5 presents the FLACC scores between the two groups. The FLACC scores of the ESK group were decreased at 1 and 24 hours after surgery compared with the FEN group (P<0.05). In the ESK group, the FLACC scores at 24 hours were lower than the scores at 1 hour (P<0.05). However, in FEN group, the FLACC scores at 24 hours were higher (P<0.05).

Table 5.

Comparison of BARF score and FLACC score between the two groups (mean ± SD) BARF score FLACC score Postoperative Time Postoperative Time

Group	n	BARF score		FLACC score
		Postoperative Time		Postoperative Time
		1 h	24 h	1 h	24 h
ESK	63	3.67±0.48	1.54±0.54	1.83±0.62*	1.28±0.45&#
FEN	61	3.05±0.61	1.34±0.52	2.06±0.38	3.15±0.24♦

BARF, Baxter Retching Faces; FLACC, face, legs, activity, cry, consolability; ESK, esketamine; FEN, fentanyl

^*P<0.05 ESK vs. FEN at postoperative 1 hour

^&P<0.05 ESK vs. FEN at postoperative 24 hour

^#P<0.05ESK group postoperative 24 hours vs. Postoperative 1 hour

^♦P<0.05FEN group postoperative 24 hours vs. Postoperative 1 hour

Correlations and P_k Values

Significant positive correlations were observed between postoperative FLACC scores (at 1 hour) and postoperative c-fos mRNA and c-jun mRNA levels (at 15 minutes and 1 hour) (Tables 6 and 7). The P_k values were >0.5, indicating the c-fos mRNA levels and c-jun mRNA were quantitative predictors for early postoperative stress reaction after surgery.

Table 6.

Correlation coefficients and P_k between postoperative FLACC score (at 1 h) and postoperative c-fos mRNA relative serum levels (at 15min and 1 h compared with the baseline)

n	FLACC score (1h)	c-fos mRNA (15min)	r	Pk	c-fos mRNA(1h)	r	Pk
124	2.33±0.71	1.56±1.02	0.72	0.82±0.11	5.50±1.14	0.76	0.85±0.12

Table 7.

Correlation coefficients and P_k between postoperative FLACC score (at 1h) and postoperative c-jun mRNA relative serum levels (at 15min and 1 h compared with the baseline)

n	FLACC score (1h)	c-jun mRNA (15min)	r	Pk	c-jun mRNA (1h)	r	Pk
124	2.33±0.71	0.42±0.78	0.71	0.81±0.11	0.91±0.08	0.75	0.84±0.11

Adverse Events

There were two cases of vomitus and four cases of nausea in each group. The vomitus was mild, and the vomitus and nausea happened 1 to 2 hours postoperatively. There was no significant difference between the two groups regarding nausea and vomiting (P>0.05). There were no differences in BARF scores of both groups at 1 and 24 hours (P>0.05). No respiratory depression or recurrent tonsillitis occurred, and no postoperative agitation was observed.

Discussion

The operation does not only damage peripheral nerves that induce acute pain effect, but it also destroys the cells that result in danger-associated molecular patterns (DAMPs.)¹⁵ The acute pain can be sensitized. The first evidence for acute pain hypersensitivity was described in 1983.⁶ Activation of N-methyl-D-aspartate (NMDA) receptors is an essential step in both initiating and maintaining activity-dependent central sensitization as its blockade by noncompetitive (MK801) or competitive (D-CPP). NMDA receptor antagonists prevents and reverses the hyperexcitability of nociceptive neurons induced by nociceptor conditioning inputs and conditional deletion of NR1 abolishes NMDA synaptic inputs and acute activity-dependent central sensitization.¹⁷ Hyperalgesia caused by opioid treatment represents a form of secondary hyperalgesia, and it is associated with diffused nociceptive sensitization induced by exposure to the drug. However, remifentanil inhibits primary hyperalgesia and induces secondary hyperalgesia.¹⁸ Therefore, in children undergoing tonsillectomy, esketamine combined with remifentanil intravenous anesthesia can reduce postoperativie remifentanil-induced hyperalgesia.

Esketamine not only inhibits hyperalgesia, but it also uniquely regulates acute inflammatory reaction and stress-induced immune disturbances that are caused by the DAMPs induced by surgery. Its regulatory action is more pronounced when it is administered before the inflammatory challenge. This is of particular interest knowing that ketamine is mostly given at the induction of anesthesia before surgery.¹⁹ This is the same as our results. The anesthetic induction of propofol combined with esketamine 0.5 mg/kg was more conducive to reducing the stress response and alleviating the inflammatory response of elderly surgical patients.²⁰ But children have more apparent volume of distribution, therefore, in our study, we selected esketamine 1 mg/kg.

The FOS and JUN protein are immediate stress response proteins. FOS shows elevated plasma levels as early as 30 to 60 minutes after stimuli and returns to normal by 90 minutes.²¹ Additionally, JUN shows maximum plasma levels by 60 minutes after stimuli and returns to normal after 180 minutes.²² Even though the relative transcription levels of the c-fos and c-jun mRNA in the serum are not a direct measurement of pain, it may sensitively and quantitatively reflect stress levels.²³ In this regard, c-fos and c-jun levels have been shown to have good sensitivity but low specificity.²⁴ In the present study, the relative transcription levels of the c-fos and c-jun mRNA in serum were increased along with the severity of pain, as supported by previous studies.²⁵ It is firmly established that the NMDA glutaminergic transmission system directly participates in the inflammatory cascade and its consequence, id est, pain by mechanisms including peripheral nerve, spinal cord sensitization, glial activation and dorsal root reflexes.¹⁹ Therefore, esketamine should induce the decrease of transcription levels of the c-fos and c-jun mRNA post-surgically. Our results were accordant with the above. The levels of c-fos mRNA and c-jun mRNA were lower in the ESK group compared with the FEN group.

The FLACC scores of the two groups were significantly different at 1 and 24 hours. There were lower FLACC scores in the ESK group 24 hours post surgery. FLACC scores at 1 hour were positively correlative with c-fos and c-jun mRNA levels. The c-fos and c-jun belong to immediate-early genes (IEGs), which are activated and transcribed within minutes after stimulation, without the need for de novo protein synthesis, stimulated in response to both cell-extrinsic and cell-intrinsic signals.²¹ It has been shown that noxious stimulation of airway epithelial cells with house dust mite extract leads to rapid up-regulation of IEG.²⁶ IEG expression was linked to synaptic plasticity and fear memory in post-traumatic stress disorder (PTSD).²⁷ Inhibiting IEG expression alleviated PTSD-like behaviors and fear memory through regulating neuroinflammation.²⁸ Therefore, preoperative esktamine use can decrease postoperative pain and promote corporal recovery by adjusting inflammation. These are concordant with previous research.^29-31

Hublet et al³² found that opioid-free anesthesia (OFA) was associated with significantly reduced cumulative postoperative morphine consumption in comparison with opioid-based anesthesia; however, the research was a retrospective cohort design. To ensure the conclusion, we designed a randomized controlled clinical trial. And we found that esketamine per se was the main component of OFA. Opioids are widely used for PICA. The recommended dose is safe but not enough for post-surgical analgesia in some patients. Additional doses will increase the risk of respiratory inhibition, nausea and vomiting, bradycardia, dry cough, constipation, and the potential risk to contribute to cancer progression in the long term. But OFA can decrease the postoperative opioid dose, lowering the relative risk of opioid overdose.

Conclusions

Esketamine-based anesthesia (1 mg/kg), can alleviate postoperative pain and regulate the inflammatory reaction in children undergoing endoscopic plasma adenotonsillectomy. This approach is superior to opioid-based anesthesia.