Opioid Free Anesthesia in Thoracic Surgery

Active Comparator: Control group

General anesthesia was induced with midazolam 0.1 mg∙kg-1, propofol 2 mg∙kg-1, and cisatracurium 0.15 mg∙kg-1. The patients were intubated with a left-sided double-lumen tube in adequate size and positioned laterally. Anesthesia was maintained with 1 minimum alveolar concentration (MAC) sevoflurane. The patients awoke from anesthesia in a post-anesthesia care unit, and were extubated after the administration of adequate doses of atropine and neostigmine as required. After surgery, if a patient complained of pain then she/he was given i.v. oxycodone by an anesthetist before commencing the patient controlled analgesia (PCA). This dose was titrated to achieve adequate analgesia. Each patient then commenced PCA. The PCA solution was oxycodone (1mgml-1) and the PCA was programmed to allow a self-administered bolus dose of 1mg oxycodone with a lockout time of 5 min. Additionally, patients were given 1 g intravenous paracetamol every 6 h and 100mg of intravenous ketoprofen every 12 h.

Drug: Opioid Anesthesia

Intraoperatively, fentanyl in fractional doses of 1-3 µg∙kg-1 were applied if the heart rate (HR; Heart Rate) or mean blood pressure (MBP; Mean Blood Pressure) increased by more than 20% above the baseline value obtained just before surgery commencement.

Experimental: Opioid Free Aneasthesia group

General anesthesia was induced with midazolam 0.1 mg∙kg-1, propofol 2 mg∙kg-1, and cisatracurium 0.15 mg∙kg-1. The patients were intubated with a left-sided double-lumen tube in adequate size and positioned laterally. Anesthesia was maintained with 1 minimum alveolar concentration (MAC) sevoflurane. The patients awoke from anesthesia in a post-anesthesia care unit, and were extubated after the administration of adequate doses of atropine and neostigmine as required. After surgery, if a patient complained of pain then she/he was given i.v. oxycodone by an anesthetist before commencing the patient controlled analgesia (PCA). This dose was titrated to achieve adequate analgesia. Each patient then commenced PCA. The PCA solution was oxycodone (1mgml-1) and the PCA was programmed to allow a self-administered bolus dose of 1mg oxycodone with a lockout time of 5 min. Additionally, patients were given 1 g intravenous paracetamol every 6 h and 100mg of intravenous ketoprofen every 12 h.

Drug: Opioid Free Anaesthesia

Before the induction of general anesthesia, a single-shot thoracic paravertebral block (ThPVB) was performed at the Th3-Th4 level. An insulated needle was used, connected to a peripheral nerve stimulator. 0.5% bupivacaine (0.3 ml∙kg-1) was then injected after a negative aspiration test. The efficacy of the blockade was checked after 20 min on both sides of the thorax with a plastic ampoule of saline. A difference in the sensation of cold between the sides of the thorax was assumed to indicate an effective block. Afterwards a continuous intravenous infusion of lidocaine and ketamine was started:

1. immediately after anesthesia induction, lidocaine was administered as an i.v. bolus at a dose of 1.5 mg∙kg-1 and ketamine in an i.v. bolus of 0.35 mg∙kg-1;
2. followed by an infusion of lidocaine 2.0 mg∙kg-1∙h-1 for 2 hours, continued at a dose of 1.2 mg∙kg-1∙h-1, and ketamine infusion 0.2 mg∙kg-1∙h-1 for 2 hours, continued at a dose of 0.12 mg∙kg-1∙h-1.

Intraoperative pain related stress [oscillations per second]

During general anesthesia the pain-related stress was assessed using a method of skin conductance fluctuations. The measurement was based on changes in skin conductance that arise under the influence of a pain stimulus.

Intraoperative opioid usage [mg]

Intraoperative usage of opioids was noted.

Intraoperative arterial blood pressure [mmHg]

Non-invasive arterial blood pressure was recorded every 5 minutes during operation.

Intraoperative heart rate [bpm]

Heart rate was recorded every 5 minutes during operation.

Overall postoperative analgesia satisfaction

Overall analgesia satisfaction was recorded at 24 and 48 postoperative hours with Likert scale. The points in Likert scale were assigned as below:

1. Very satisfied.
2. Satisfied.
3. Neither satisfied nor dissatisfied.
4. Dissatisfied.
5. Very dissatisfied.

Postoperative pain intensity (VAS)

Pain intensity at rest was recorded with Visual Analogue Scale (VAS) at 0, 1, 2, 4, 8, 12, 18, 24, 30, 36, 42, 48 postoperative hours. Patient pointed intensity of symptoms on a 10cm ruler, where 0cm corresponded to no pain and 10cm corresponded to the strongest possible pain.

Postoperative pain intensity (PHHPS)

Pain intensity at rest was recorded with Prince Henry Hospital Pain Score (PHHPS) at 0, 1, 2, 4, 8, 12, 18, 24, 30, 36, 42, 48 postoperative hours. The points in PHHPS score were assigned as below:

0. No pain during coughing.

1. Pain during coughing.
2. Pain during breathing.
3. Constant light pain.
4. Constant strong pain.

Postoperative arterial blood pressure [mmHg]

Non-invasive arterial blood pressure was recorded at 0, 1, 2, 4, 8, 12, 18, 24, 30, 36, 42, 48 postoperative hours.

Postoperative heart rate [bmp]

Heart rate was recorded at 0, 1, 2, 4, 8, 12, 18, 24, 30, 36, 42, 48 postoperative hours.

Postoperative sedation level

Sedation level was was recorded at 0, 1, 2, 4, 8, 12, 18, 24, 30, 36, 42, 48 postoperative hours with Ramsay scale. The points in Ramsay scale were assigned as below:

1. Patient is anxious and agitated or restless, or both.
2. Patient is co-operative, oriented, and tranquil.
3. Patient responds to commands only.
4. Patient exhibits brisk response to light glabellar tap or loud auditory stimulus.
5. Patient exhibits a sluggish response to light glabellar tap or loud auditory stimulus.
6. Patient exhibits no response.

Postoperative analgesic requirement [mg]

Analgesic requirement was recorded at 0, 1, 2, 4, 8, 12, 18, 24, 30, 36, 42, 48 postoperative hours.