Effect of Erector Spinae Plane Block in Terms of Analgesic Efficacy in Elderly Patients Undergoing Posterior Lumbar Spine Surgery: A Retrospective, Propensity-Score Matched Study

Study Design

This study was conducted in compliance with the Helsinki declaration’s ethical principles and was approved by the institutional review board of Ganzhou People’s Hospital. As a result of the retrospective design, signed informed consents for participation were unavailable; therefore, the institutional review board at Ganzhou People’s Hospital waived the informed consent procedure for the current study. The electronic medical records of our hospital were reviewed to identify patients who met the following inclusion criteria: (1) aged 65 years or older, (2) posterior lumbar spine surgery under general anesthesia, (3) American Society of Anesthesiologists (ASA) physical status 1–3, (4) body mass index (BMI) less than 40 kg/m2. The exclusion criteria included (1) a previous history of surgery in the involved lumbar spine, (2) severe organ insufficiency, (3) a history of prolonged use of analgesic drugs, and (4) absence of complete data.

Data Collection

Data of selected patients were retrospectively retrieved from the medical database of our hospital. Demographic features included age, gender, BMI, marital status, smoking history, ASA physical status, and surgery time. Charlson comorbidity index (CCI) was calculated to obtain an overall assessment of preoperative comorbid condition. CCI included prior stroke, circulatory abnormalities (hypertension, coronary heart disease, prior myocardial infarction, and arrhythmia), type 2 diabetes, chronic obstructive pulmonary disease, dementia, pulmonary infection, Parkinson’s disease, digestive system disorders, chronic renal failure, rheumatologic disease, and osteoporosis [19]. Preoperative vital signs, as well as blood glucose (Glu), hemoglobin (HGB), serum albumin (ALB), platelet (PLT) count, white blood cell (WBC) count, international normalized ratio (INR), blood urea nitrogen (BUN), and left ventricular ejection fraction (LVEF), were recorded. An abnormal vital sign was defined according to the criteria of Zanker and Duque’s study [20].

Outcomes

The primary outcome was opioid consumption at 24 h after surgery. Secondary outcomes was visual analog scale (VAS) pain scores at rest in the first 24 h, number of patient-controlled intravenous analgesia (PCIA) pump compressions, ratio of patients requesting rescue analgesia, incidence of nausea and vomiting, and length of stay. Additional secondary outcomes were adverse events, which were monitored from the beginning of anesthesia until 24 h after surgery.

Treatment Protocol in Perioperative Period

Visit the patient in the ward on the day before surgery, inquire and understand the general physical condition of the patient, and establish relevant preoperative preparation and improvement of relevant examinations. Communicate fully with patients and their families, and inform them about the anesthesia protocol and the use of PCIA pump.

After entering the operating room, all patients underwent tripartite verification, and peripheral venous access was routinely opened after verification. The drip rate of sodium lactate Ringer injection was set at 8 ml/kg/h. Vital signs were routinely monitored, and the depth of anesthesia was monitored with bispectral index (BIS) monitor (Covidien llc, USA). Before anesthesia induction, 0.5 mg atropine was injected intravenously to estimate the scope of surgical incision, and body surface markers were made in the median of the corresponding lumbar segment.

In the ESPB group, patients were placed in the prone position, and an ultrasonic high-frequency linear array probe (5–10 MHz) was installed with disposable sterile protective sleeve. The position of the spinous process of the third lumbar spine was determined by median sagittal long-axis scanning (Fig. 1). Then the probe was rotated to the horizontal position of the short axis, and the probe was moved laterally 2–3 cm to identify the pectoralis longissimus muscle and multifidus muscle successively. The puncture needle tip (22 G, 90 cm long) was positioned at the fascia space between the longissimus pectoralis and multifidus muscle. After blood was withdrawn, all patients received an injection of 0.33% ropivacaine 15 mL.

Fig. 1figure 1

Ultrasound image of erector spinae plane block

Anesthesia induction was performed immediately after completion of nerve block. Anesthesia induction was performed in the two groups by intravenous injection of midazolam 0.05 mg/kg, sufentanil 0.5 μg/kg, etomidate 0.2 mg/kg, and cisatracurium sulfonate 0.15 mg/kg. After anesthesia induction, 4–6 L/min high-flow pure oxygen was given for 3 min under mask pressure. After the full effect of the induction drug, the patient’s body movement, pain and eyelash reflex disappeared, and the muscle relaxation was satisfactory, endotracheal intubation was performed under laryngeal exposure. After intubation, the anesthesia machine (Draeger Medical GmbH, Germany) was used for mechanical ventilation, and the tidal volume was set at 6–8 mL/kg to control respiratory parameters. The respiratory rate was 10–12 times/min, and the partial pressure of ETCO2 was maintained at 35–45 mmHg. Propofol 4–8 mg/kg/h, remifentanil 0.1–0.2 μg/kg/min, and cisatracurium 0.06–0.12 mg/kg/h were used to maintain BIS at 45–65. The infusion rate was adjusted according to BIS value and vital signs. The mean arterial pressure of the patients was maintained to be no less than 20% of that before surgery to ensure stable blood flow. Sufentanil was added periodically according to specific conditions and the infusion speed of anesthetic drugs was adjusted. All operations were performed by the same group of experienced surgeons who did not know the experimental grouping.

Statistical Analysis

Continuous data were evaluated for normality using the Shapiro–Wilk test and Q–Q plots. Variables with normal distribution were expressed as mean ± SD and compared with the independent t test; otherwise, they were expressed as median (interquartile range) and compared with Mann–Whitney U test. Categorical variables are presented as total numbers and percentages. Comparisons between groups were made using the χ2 test for categorical variables and the Mann–Whitney U test for continuous variables, as appropriate.

The total number of initial participants comprised the original cohort. PSM was used to create well-balanced groupings, notably the matched cohort, in addition to the original cohort. PSM-based propensity score adjustments were also applied to confirm the validity of our findings [21, 22]. The propensity score was calculated utilizing a non-parsimonious multivariable logistic regression model, with ESPB as the dependent variable and all baseline parameters as the independent factors. Patients in the ESPB group were matched with patients in the control group using the greedy nearest neighbor-matching method with a caliper width of 0.2. To assess the efficacy of the PSM, the standardized mean differences (SMD) were computed. SMD < 0.1 is considered a reasonable compromise between the groups [21].

All statistical analyses were performed using R software (version 4.1.1), and P < 0.05 was considered statistically significant.

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