Paracetamol and Metamizole With SPI-guided Anaesthesia for VRS (P&MSPIVRS)

Influence of SPI-guided Analgesia With Preemptive Analgesia Using Either Paracetamol or Metamizole on the Presence of Oculocardiac Reflex, Postoperative Pain, Postoperative Nausea and Vomiting in Patients Undergoing VRS Under General Anaesthesia: a Randomised, Controlled Trial

The aim of this randomized trial is to assess the efficacy of preemptive analgesia using paracetamol or metamizole or both of them under SPI-guided anaesthesia for vitreoretinal surgery (VRS), presence of PONV (postoperative nausea and vomiting) and oculocardiac reflex (OCR) and compare Numerical Rating Scale (NRS) with Surgical Pleth Index (SPI) for monitoring pain perception postoperatively. Patients will receive general anaesthesia combined with either preemptive analgesia using preemptive intravenous infusion of 1,0 g of metamizol or preemptive intravenous infusion of 1,0 g of acetaminophen or both of them together.

Monitoring depth of anaesthesia using spectral entropy (SE) and quality of neuromuscular block are routine in modern anaesthesia, whereas monitoring of analgesia still requires further studies. Recently, the Surgical Pleth Index (SPI) was added as a surrogate variable showing the nociception-antinociception balance into abovementioned parameters constituting a novel approach in monitoring patients intraoperatively, known as adequacy of anaesthesia (AoA) or tailor-made anaesthesia. Different options of preemptive analgesia are used to decrease the postoperative pain perception as well as diminish the rate of PONV by deceasing intraoperative consumption of intravenous narcotic analgesics

Surgical Pleth Index (SPI), General Anaesthesia (GA),, Numerical Rating Scale (NRS), Adequacy of Anaesthesia (AoA), Oculocardiac reflex (OCR), paracetamol, metamizole

in group M patients will receive pre-emptive analgesia using intravenous infusion of metamizol in a single dose of 1,25 gram

in group P patients will receive pre-emptive analgesia using intravenous infusion of metamizol in a single dose of 1,25 gram

in group PM patients will receive pre-emptive analgesia using intravenous infusion of metamizol in a single dose of 1,25 gram and paracetamol in a dose of 1 gram

The investigators will compare the efficacy of analgesia intraoperatively according to used preoperatively intravenous infusions . The investigators will administer a rescue dose of fentanyl intravenously in a dose of 1 mcg per kg of body weight in the case when SPI value increases over 10 points in SPI scale every 5 minutes until SPI value decreases back to baseline value. Additionally, the investigators will analyse rescue fentanyl consumption in abovementioned groups

The investigators will compare the efficacy of analgesia postoperatively according to technique of analgesia used preoperatively: intravenous infusion of either metamizol or paracetamol or both of them. The investigators use NRS and compare it with SPI values.

The investigators will compare the presence of PONV after emergence from GA in studied groups. The investigators will observe patients postoperatively and record any incidence of nausea or vomiting and in the abovementioned case the investigators will administer a standard dose of antiemetic drug.

Inclusion Criteria: written consent to participate in the study written consent to undergo general anaesthesia alone or combined with different techniques of pre-emptive analgesia and vitreoretinal surgery Exclusion Criteria: history of allergy to local paracetamol or metamizole necessity of administration of vasoactive drugs influencing SPI monitoring pregnancy

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