Inguinal hernia repair is one of the most performed surgical procedure worldwide [17]. Innovations in surgical and anesthetic techniques have allowed to significantly decrease the impact on the patient, permitting to perform the procedures in an ambulatory setting [5]. Local anesthesia seems to be the most recommended anesthetic choice in term of cost-effectiveness [18], but some problems still remain: it is proved to be effective for small and reducible hernias, and depends on surgeon experience [19]. Sometimes could be insufficient and intraoperative sedation may be required [20].
Patients’ comfort and pain control would be guaranteed with spinal anesthesia, even if it is affected by potential complications, such as hypotension, post-dural puncture headache (PDPH), urinary retention, and, the most feared in the ambulatory setting, prolonged lower limbs paralysis. Those negative features are commonly related to long acting local anesthetic agents, such as bupivacaine or ropivacaine. Nevertheless, short acting agents such as lidocaine and mepivacaine are not recommended because of their high correlation with transient neurological symptoms (TNS).
Hyperbaric prilocaine is a short acting drug, not associated with TNS, that allows selective unilateral spinal anesthesia with lower incidence of complications.
With this study, we compared the use of selective, unilateral spinal anesthesia with hyperbaric prilocaine, with local anesthesia with mepivacaine performed by the surgeon, in 132 patients who underwent open inguinal hernia surgical repair.
Our data showed how in spinal anesthesia group (group A), patients had significantly less pain than local anesthesia group (group B), both intraoperatively and post-operatively, enhancing patients’ comfort and surgical experience. Group A patients required neither intraoperative opioids nor sedation. On the contrary, almost half of the group B patients required intraoperative opioids and over 40% of them had to be deeply sedated. Similar results arises in another study from Palumbo et al [21]. On the other hand, data from a review by Prakash et al. [22], including 10 RCTs and 1379 patients, are strongly in support of local anesthesia, showing higher intraoperative pain, higher failure rate as well as higher urinary retention rate in spinal groups. Other studies revealed a higher rate of similar complications with spinal anesthesia [22,23,24], but those results usually match with low, bilateral, neuraxial blocks and use of long acting agents, and none of the studies included were carried out with hyperbaric prilocaine. In our study, there was no complications described, and we reported only one case of bradycardia rapidly regressed after atropine administration.
Low dosage prilocaine use, combined with the right puncture level, the kind and size of the needle, the injection technique, and the experience of the anesthetist, surely contributed to reach these results. A wrong injection technique might be sufficient to affect the block effectiveness. We performed all the injections very slowly with the bevel of a 27-G Whitacre point needle oriented downward in order to obtain a complete lateralization of the block [16]. Furthermore, we administered the agent with the patients in Trendelemburg position, avoiding drug pooling in the lower dural sac (potential cause of block failure and urinary retention) and enhancing its cranial distribution to the thoracic roots, prolonging abdominal analgesia. We found neither cases of urinary retention, nor other complications that could prolong time to discharge (groups A and B, respectively 74 ± 5 and 75 ± 4.1min p = 0.5625). Ultimately, the advantageous pharmacokinetic of the prilocaine made the rapid recovery possible. The rapid recovery we obtained in our study is consistent with the data published in a review by Boublik et al. [9], who analyzed the use of prilocaine for ambulatory surgery in 5486 cases. Dosage between 30 and 60 mg appears to be the safest in terms of unilateral anesthetic success and time to recovery [9, 25, 26]. Differently, in several other studies which compared local anesthesia with spinal anesthesia performed with other drugs [23, 24, 27], recovery time and subsequently time to discharge has been found significantly longer in spinal groups.
In our research, time to discharge is measured from the end of the surgery to the exit from the hospital. Fundamental criteria for readiness to discharge included voiding and ambulation. Most of the group A patients were ready to ambulate and were discharged home approximately 30 min after the end of surgery. A large proportion of the group B patients needed to recover from a deep sedation, prolonging the time to discharge.
Regarding the surgery time, in their review, Prakash et al. found no difference between the groups.
Moreover, most of the available literature shows no differences in surgical time [8, 22, 27] or even a shorter surgical time for the local anesthesia patients [23, 24]. The contrast of this results with our finding is probably related to the extreme variability in local anesthesia methodology between different authors, either for technique and time required or for its efficacy and need for further intraoperative infiltrations and time wasting. In our research, local anesthesia technique was not standardized. As a result, effectiveness of local anesthesia might have been influenced by operator experience and personal methodology and, being local anesthesia time included in surgery time, surgery time could have changed accordingly. Conversely, spinal anesthesia time is not part of the surgery time, being the neuraxial block performed before the surgery, outside the operating room. This is a major bias of our study. Differences in local anesthesia mixtures and patients’ variability in pain tolerance, may also explain these discrepancies between literature’s data and ours.
Beyond all these considerations, in our facility spinal anesthesia with prilocaine has proven to be more effective and efficient than local anesthesia. Considering our standard surgical session of 6 h (8 a.m.–2 p.m.) for 5 procedures scheduled, a time saving of 17 min per procedure, resulted in a total saving of about 90 min that perfectly fit 2 extra procedures, resulted in a great improvement of the workflow and of the efficiency of the operating room increasing cost-effectiveness of the procedure. It has to be said that, in differently organized units, where performing spinal anesthesia outside the operating room before the intervention is not feasible, including the time for spinal anesthesia would make the operative time longer, perhaps negating the benefit on surgical time for spinal anesthesia.
Another bias of our study is the fact that neither the operator nor the patient could be blinded. Additionally, we have evaluated post-operative pain just at 60 min after surgery, which is a quite short time to evaluate post-operative analgesia, especially considering that local anesthesia may give a longer lasting benefit than spinal anesthesia; a home readiness scoring every half-hour and a long-term observation of post-operative pain would have returned even more interesting data. Although our data suffers from these limitations, they encourage us to further investigate and better define whether unilateral spinal anesthesia with prilocaine should be placed or not beside local anesthesia in the open inguinal hernia management guidelines. More randomized controlled trials are needed to confirm this hypothesis.
