1% ropivacaine alone provides suitable intra-, postoperative anaesthesia for vitrectomy
When administering peribulbar anaesthesia, 1% ropivacaine alone is sufficient for patients undergoing pars plana vitrectomy, suggests a recent study. Furthermore, it delivers a satisfactory quality of intraoperative anaesthesia and better postoperative anaesthesia, as well as improves patient comfort compared with bupivacaine, lidocaine and the mixture of lidocaine and bupivacaine (lido+bupi).
“For peribulbar anaesthesia in vitrectomy, 1% ropivacaine alone provides an adequate intraoperative anaesthesia similar to that provided by the bupivacaine, lidocaine and lido+bupi solutions, as well as provides a better quality of postoperative analgesia and decreases postoperative subconjunctival haemorrhage,” researchers said.
The mean time of onset of analgesia was 90.46±30.08 sec for ropivacaine, 94.83±40.72 sec for bupivacaine, 78.31±12.56 sec for lidocaine and 101.51±56.94 sec for lido+bupi (p=0.087). For the onset of akinesia, the mean time was 138.89±62.65 sec for ropivacaine, 151.86±84.78 sec for bupivacaine, 122.66±49.35 sec for lidocaine and 141.54±62.69 sec for lido+bupi (p=0.323). [Br J Ophthalmol 2017;101:1016-1021]
“In our study, there was no significant difference in the time of onset of both analgesia and akinesia among the four groups,” researchers said. “The findings are similar to the results of those of Jaichandran et al and Gioia et al who conducted a study on peribulbar anaesthesia for vitreoretinal surgery.” [Ophthalmology 2015;122:1030–3; Anesth Analg 1999;89:739–42]
Furthermore, there was no significant difference in the number of patients who achieved grade 5 anaesthesia in the four groups (p=0.966).
Based on ordered logit analysis, patients receiving 1% ropivacaine had a significantly lower degree of postoperative pain than those in the other three groups (p=0.017, p=0.001 and p=0.001, respectively). Also, the ropivacaine group had lower incidence of postoperative subjunctival haemorrhage than the other three groups (p<0.001).
While both ropivacaine and bupivacaine are long-acting, amide-type local anaesthetics, the former is sold as a pure S(−)-enantiomer while the latter is a racemate. Lidocaine is a short-acting amide-type local anaesthetic.
“The proton binding affinity (pKa) values determine the penetration time of the solution, and the specific pKa values are 7.7 for lidocaine and 8.1 for both ropivacaine and bupivacaine, which largely determine the onset of local analgesia,” researchers said. [Expert Opin Pharmacother 2000;1:325–36]
“Agents with lower pKa constants provide a more rapid analgesic onset. The plasma binding rate of protein is 94, 95 and 64 percent for bupivacaine, ropivacaine and lidocaine, respectively. The more capable an anaesthetic binds to protein, the longer the duration of action,” they added. [Ophthalmology 2015;122:1030–3; Ophthalmology 1997;104:425–8]
In the current study, researchers compared the intraoperative and postoperative clinical properties of 1% ropivacaine, 0.75% bupivacaine, 2% lidocaine and a mixture of 0.75% bupivacaine and 2% lidocaine administered for peribulbar anaesthesia in 140 patients undergoing pars plana vitrectomy. They measured the time of onset of analgesia and akinesia, as well as recorded the efficacy of anaesthesia, degree of postoperative pain, and intraoperative and postoperative complications.