not enough patients were recruited

The purpose of this study is to evaluate differences between single-shot EQUAL ropivacaine doses of the serratus anterior plane block (SAPB) or erector spinae plane block (ESPB) injection, when used as adjuvant to treat postoperative pain, after one-stage unilateral hybrid arrhythmia (atrial fibrillation, ventricular tachycardia, inappropriate sinus node tachycardia) ablation surgery. The primary outcomes are to evaluate block placement efficacy in the hybrid surgery setting (total time to block placement in seconds, time to visualization of location of injection in seconds, adequacy of ropivacaine spread) by picturing and worst numerical scale pain at rest or moving, using a visual analog pain scale from 0= no pain to 10= maximal pain, in the first 12 hours after admission to the post-anaesthesia care unit. Secondary outcomes aim to evaluate to investigate pain location, additional analgesic consumption and requests, ease of breathing, breathing quality, sleeping quality and quantity, duration of hospitalisation, and general level of satisfaction.

This clinical investigation is an interventional uni-center, prospective, open, randomized, double arm, blinded to the pain physician and the patient, clinical evaluation.

To ensure the same number of patients in each group, a stratified block randomization will be performed. A randomization list is generated for each type of arrhythmia. Patients will be block randomized into two groups: the serratus anterior plane block (SAPB) arm or the erector spinae plane block (ESPB) arm. As such the nerve block performing physician will be informed on the nerve block choice just before surgery.

132 consecutive patients. (22 in each group) Single Center study: Universitair Ziekenhuis Brussel - department of Anesthesiology 3 years Subject will be followed till 3 days post-procedure

Primary outcome measurement details:

The total time to block placement is obtained by starting a timer after local antiseptic application, just before puncturing the skin, to full injection of the local anaesthetic ropivacaine where the timer will be stopped.

In practice: a physician places the nerve block, a nurse anaesthetist manages the patient and a second nurse assistant records the timing and takes a picture just before drug injection and after block injection The time to visualization of the optimal location before nerve block injection is defined as the time needed to find the best place before local anaesthetic injection.

A picture of the location will be taken just before and after injection (by the second nurse assistant with an I-phone or similar device and kept with the patient's file Pain assessment will start 1 h after ICU admission by a different team (ICU nurse- intensive care physician or pain nurse). The first 24h assessments are blinded to the block performing physician.

Visual- analog- pain scores (0 no pain-10= maximal pain) will be analysed at rest or moving every 4 h or more depending on the patient's needs/requests for the first 24 h. After this period pain will be analysed twice daily (morning and afternoon) up to 72 h after start of surgery or less when dismissed earlier.

Secondary outcome measurements will be recorded after the initial 24h twice/da (morning and afternoon) by a pain nurse. Written data will be transmitted for storage to REDCAP.

Inclusion Criteria:

1. Age 18-80 years.

2. Provision of signed informed consent prior to any study-specific procedure

3. Selected for Hybrid Rhythm ablation surgery (ISNT, VT, AF)

4. American Society of Anesthesiologist physical Status I to III

5. Dutch, French or English speaking

6. Ability to follow the study protocol

7. BMI > 35 kg/m2 . BMI or Body mass index will be obtained from body weight in kg divided by the square of the length in meter and is expressed in kg/m2

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   Exclusion Criteria:

   • a. History of chronic pain or drug treatment abuse
   • b. Depression, psychiatric morbidity or mal-adaptive coping behaviour
   • c. Neuropathy
   • d. Severe anxiety or other mental ailment, taking drugs affecting their capacity to assess pain (gabapentin, pregabalin, opiod use)
   • e. Chronic or acute skin infection of the back or the lateral thorax
   • f. Hypersensitivity to ropivacaine
   • g. Severe hepatic, renal , pulmonary or cardiac (EF < 30%) disease or refuse to participate to the study..