Analgesia related to the administration of local anesthetic solution into the fascia of erector spinae muscle is mediated by the effect of local anesthetic on the posterior and lateral branches of the anterior part of the spinal nerve. Comparable analgesic efficiency after the administration of both nerve blocks would reject the widespread theory of the paravertebral site of effect of the local anesthetic in ESPB.

Inclusion Criteria:

• Patiens undergoing VATS-surgery

Exclusion Criteria:

• Age < 20 years
• Body Mass Index >35 kg/m2
• Technical difficulties with the nerve block administration and/or subsequent bolus application
• Abnormal course of the surgery (e.g. conversion to thoracotomy) or the postoperative phase (e.g. surgical revision of the chest)
• Patient's refusal