Comparison of Intercostal Nerve Block Versus Patient-Controlled Intravenous Analgesia for Post Thoracotomy Pain

Introduction: Acute pain after thoracic surgery is frequent, intense and can raise morbidity. Effective postoperative pain control is essential to support early mobilization, optimal respiratory function, and recovery. Different pain relief methods, such as systemic opioids, patient-controlled analgesia, and intercostal nerve blocks, have been studied to reduce problems and enhance recovery for patients who have had thoracic surgery.

Objectives: This research aims to compare the difference in analgesic effect of intercostal nerve block (ICNB) versus patient-controlled intravenous analgesia (PCIA) for post-thoracotomy analgesia in cardiac surgery.

Methods: This prospective, single-blind, randomized comparative study involved 128 patients aged 30-60 years undergoing cardiac surgery through a thoracotomy under general anesthesia. Patients were randomly assigned to two groups. Group A received ICNB with 2.5 mg/kg of 0.5% ropivacaine and 0.5 mcg/kg fentanyl at the end of surgery; rescue analgesia with fentanyl 1mcg/kg was given if VAS score exceeded 4 within 24 hours post-intubation. Group B received PCIA with IV fentanyl (25 mcg/ml) at a basal rate of 1 ml/hour, with 1 ml bolus doses available every 15 minutes post-extubation for 24 hours. Pain was assessed using the Visual Analogue Scale (VAS), and total fentanyl consumption and sedation score were recorded. Significance level was kept at 95%.

Results: The demographic data were comparable between the two groups. The VAS score was significantly lower in the ICNB group than in the PCIA group (p value < 0.05). The total dose of fentanyl required in 24 hours after extubation was significantly higher in the PCIA group than in the ICNB group. The mean Ramsay sedation score was higher in the PCIA group compared to the ICNB group. Patients in ICNB group showed a lower incidence of side effects.

Conclusion: Our study suggests that the ICNB is more effective than PCIA for post-thoracotomy analgesia and also requires a lesser total dose of opioid.

INTRODUCTION

Pain is the major concern for both the patient and the anesthesiologist in the perioperative period (¹). Acute pain after thoracic surgery is common and severe, increasing morbidity (²). The pain hinders the patient from coughing effectively, breathing deeply, or moving. Severe postoperative pain, in general, increases post-operative complications and may lead to chronic pain (³). Optimal postoperative pain management for cardiothoracic surgery patients enables early mobilization, respiratory physiotherapy, and sufficient sleep. It also reduces stress, mechanical breathing time, stay duration in the hospital, and the risk of comorbidities like pneumonia, atelectasis, deep vein thrombosis, and cardiac ischemia (⁴). Systemic opioid-based treatment regimens, intramuscular or intravenous opioids, nonsteroidal anti-inflammatory drugs, per rectal administration of drugs, intercostal nerve block (ICNB), thoracic epidural block, thoracic paravertebral block, and erector spinae block are all options for controlling acute pain after thoracic surgery (¹,³).

Patient-controlled analgesia (PCA) allows patients to self-administer modest bolus doses of opioids, allowing them to achieve effective blood concentrations as needed. It shortens the interval between pain perception and drug administration and reduces the overall analgesic dose necessary (¹).

Morphine, tramadol, fentanyl, sufentanyl, oxycodone, and ketamine are among the drugs that can be utilized in a PCA pump. Continuous morphine infusion increases morphine intake, sedation, and, most likely, the prevalence of respiratory depression (⁵). Fentanyl has analgesic strength comparable to morphine, and its high lipid solubility shortens the onset time, making it suited for IVPCA. Unlike morphine, fentanyl does not create active metabolites that cause respiratory depression and has a shorter duration of effect. However, the use of IVPCA with fentanyl for acute post-thoracotomy pain management is still uncommon (⁶). Because nociception travels primarily through the intercostal nerves in the thorax, blockade of the intercostal nerve is used to provide analgesia after thoracic surgery. Intercostal nerve blocks are a regular component of multimodal analgesia following thoracic surgery (²).

Intercostal nerve blocks are an efficient means of relieving post-thoracotomy pain that can be performed using anatomic landmarks or ultrasound guidance (³). It offers technical simplicity, analgesia, enhanced pulmonary mechanics, less central nervous system depression, and avoidance of urine retention (⁵). It is also quite simple to perform and, when administered at the desired dermatome level, delivers segmental analgesia. Cardiac surgery by thoracotomy has the added benefit of allowing ICNB to be administered directly at the location before the surgical incision is closed. Ropivacaine has a low-fat solubility, cardiac and central nervous system toxicity (⁷), and is likely to provide a longer duration of anesthesia in digital nerve blocks than bupivacaine and lidocaine (⁵).

In this study, we compared the intercostal nerve block (ICNB) versus patient-controlled intravenous analgesia (PCIA) for relief of post-thoracotomy pain for adult cardiac surgery.

METHODS

This prospective, randomized, comparative study was conducted at a tertiary care cardiothoracic center after approval from the Institutional Ethical Committee No. 34/MC/EC/2021. The study was registered in the Clinical Trial Registry (CTRI/2022/10/046882). The study included 128 American Society of Anesthesiologists (ASA) physical status II-III patients in the age group of 30-60 years scheduled for an elective cardiac surgery through a thoracotomy incision. Written informed consent was obtained after a complete explanation of the study protocol and the procedures. Patients who had prior chest surgeries, were allergic to ropivacaine, could not complete the visual analogue scale (VAS) score, had trouble using the PCIA pump, or did not provide informed consent were not included in the study.

Sample Size

A sample size of 64 patients in each group was required at 95% confidence and 80% power to verify the expected difference of 0.7±1.4 μg/kg in the mean difference of total amount of fentanyl used after surgery between the two groups (⁵). Pre-procedure complete blood counts, chest X-ray (CXRs), electrocardiogram (ECGs), and coagulation profiles were acquired for every patient.

Intravenous (IV) access was acquired, and standard monitors were connected after establishing nil per oral status. An internal jugular line & an arterial line were secured under local anesthesia. General anesthesia (GA) was induced with an injection of Midazolam 0.05 mg/kg, Fentanyl 3 mcg/kg, Etomidate 0.3 mg/kg and Rocuronium 0.9 mg/kg for pre-anesthetic drugs, intermittent positive pressure ventilation (IPPV) was done for 60 seconds, and the patient was intubated with a proper-size cuffed endotracheal (ET) tube. Following standard institutional policy, GA was maintained in conjunction with capnography and bispectral index monitoring. The hemodynamic parameters were maintained within 20% of baseline.

A computer-generated random number table was used to divide the patients into two groups of 64 each, and coded, opaque, and sealed envelopes were used to keep them concealed. VAS score, dose of fentanyl needed, and sedation score were assessed immediately, and 1, 2, 4, 6, 8, 10, 12, and 24 hours after extubation. Total dose of fentanyl, Time to first rescue analgesia, length of stay in the Intensive Care Unit (ICU) and side effects if any were assessed for 24 hours post-extubation.

A day prior to the procedure, the patient's complete medical and surgical history, including any known drug allergies, was obtained. Vital parameters (blood pressure, pulse rate, temperature and respiratory rate), and body weight of the patients were noted. Standard monitors were attached once intravenous (IV) access was secured after establishing nil per oral status. General anesthesia was given, and hemodynamic parameters were maintained

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