Pain after ambulatory surgery is an important problem in daily clinical anesthesia. It is one of the major reasons for readmission. Therefore steps should be taken to minimize pain after ambulatory surgery.
Combining paracetamol with a NSAID is considered standard practice. Often an opioid is added. Whereas earlier mostly tramadol was chosen, patients often complained about dizziness and nausea. Now there is a trend towards oxycodon. A high oral bioavailability makes it a good choice as a tablet with a long acting and a fast acting version to choose of or to combine. This easy application is also a disadvantage with the potential for inappropriate use also if described postoperatively.
This approach of combining paracetamol with a NSAID and a (weak) opioid is in accordance with the WHO pain ladder. But unfortunately it does not solve all problems of postoperative pain management after ambulatory surgery.
In the following, additional options will be described including regional anesthesia, methadone, enhanced intraoperative multimodal regimens en enhanced postoperative multimodal regimens.
It is important to realise that one of the main problems is that we are not yet able to reliably identify the patients with severe postoperative pain after ambulatory surgery. That makes it more difficult to decide when to go for the enhanced options (and when not).
Regional anesthesia One point of interest is the prolongation of peripheral nerve blocks in the ambulatory settings. Addition of substances like dexamethasone or dexmedetomidine have been described to prolong peripheral nerve blocks. Recently, choosing a liposomal local anesthetic like liposomal bupivacaine became also an option. Whereas a single shot technique with additives or with liposomal bupivacaine is technically the easier option, some centers are working with catheter techniques also in the ambulatory setting. Elastomeric disposable pumps, removal of the catheter by the patients themselves and easy trouble shooting for example via smart apps are important parts of this approach.
When no pure regional anesthesia approach is chosen or available for a specific surgery, the addition of a regional technique for improved postoperative analgesia should always be considered. The infiltration of the incision site with local anesthetics is nearly always possible. For the ambulatory setting often a very distal technique like posterior tibial nerve block for foot surgery or a block of the distal upper limb nerves, i.e. median, radial, ulnar or musculocutaneous nerve are advantageous and easily learned and performed with ultrasound guidance.
Recently described thoracic wall blocks like PECs block II or serratus plane block and abdominal wall blocks like quadratus lumborum block are a welcome addition for ambulatory surgery. The erector spinae block is a relative simple option (nearly) without the risk of pneumothorax and can be chosen as a substitute for the traditional paravertebral block for thoracic wall surgery when the processus transversus at level Th3/Th4 is targeted or for abdominal surgery when the processus transversus at level Th7/Th8 is targeted.
Historic books about regional anesthesia like ‘Regional Anesthesia (Victor Pauchet’s Technique)’ by B. Sherwood-Dunn, 1920, are incredible sources of inspiration for the dedicated regional anesthesiologist searching for the re-invention of regional techniques for ambulatory surgery.
Methadone Methadone is a synthetic opioid with unique properties as it combines a very long-acting pharmacology with acting not only on opioid receptors but also on NMDA receptors (like e.g. ketamine or magnesium). Whereas it is a standard part of the care for drug addictives and for chronic pain patients and it is less known for perioperative analgesia.
Due to its long acting properties, a single bolus at induction is often sufficient. Problems like cumulation and respiratory depression as described with repetitive administrations are less a problem (or no problem) with a single bolus at induction of anesthesia. Whereas a single bolus at induction of 0,2 mg/kg has been suggested, for ambulatory surgery often a smaller bolus like 0,1 – 0,15 mg/kg is sufficient.
Komen at al. published the following study very recently in Anesth Analg (2019; 128:802–810): ‘Intraoperative methadone in same-day ambulatory surgery: A randomized, double-blinded, dose-finding pilot study.’ They concluded: ‘In same-day discharge surgery, this pilot study identified a single intraoperative dose of methadone (0,15 mg/kg ideal body weight), which decreased intraoperative and postoperative opioid requirements and postoperative pain, compared with conventional intermittent short-duration opioids, with similar side effects.’ Interestingly they found also a very long-lasting effect: in the 30 days after discharge patients who received methadone 0,15 mg/kg had less pain at rest and used fewer opioid pills than controls.
Enhanced intraoperative multimodal regimen Gabapentinoids, dexamethasone, ketamine and magnesium are seen as common parts of an enhanced intraoperative multimodal regimen. For ambulatory surgery, some anesthesiologists are relatively reluctant concerning gabapentinoids as dizziness and sedation are common (unwanted) side effects which are especially unwanted in ambulatory patients.
Dexamethasone has been described to prolong peripheral nerve blocks (not only if applied perineurally but also if applied intravenously) and reduce pain scores after spinal anesthesia. As multimodal analgetic component a dose of 0,1 mg/kg has been recommended. Therefore, for this purpose a standard dose of 4 or 5 mg dexamethasone as used for PONV prophylaxis is not sufficient.
Due to its action on the NMDA receptor, ketamine is traditionally part of many multimodal analgetic regimens. Discussions remain about the optimal dose. The actual 2018 Cochrane review ‘Perioperative intravenous ketamine for acute postoperative pain in adults’ states: ‘No analysis by dose was possible.’ In contrast, a previous version of this Cochrane review stated: ‘Interestingly there seemed to be no increased morphine-sparing effect on increasing the ketamine dose above an estimated dose of 30 mg/24 hours.’ Therefore a reasonable dosing in ambulatory patients may be to limit the ketamine dose to 30 mg racemic ketamine or 15 mg esketamine. As there are doubts in the literature about the effectivity of a single bolus ketamine, some anesthesiologists split this amount of ketamine in two parts, giving one part at induction and one part e.g. 30 minutes after incision. Interestingly, for depressive patients this ketamine dose has been shown to have a mood enhancing effect.
Magnesium iv has been less often used in the past. But there is evidence for its analgetic properties as magnesium is also acting on the NMDA receptor. Commonly a dosing scheme with a bolus of 40–50 mg/kg (given over about 15 minutes) followed by a continuous infusion has been used. Avoiding hypomagnesemia which is often present after surgery seems to be correlated with lower postoperative pain. Therefore in ambulatory surgery simplified dosing schemes with a single bolus of 2g magnesium administered in the infusion drip chamber may be sufficient.
For abdominal surgery infusion scheme of lidocaine iv has been described for better postoperative analgesia. This can be used for many laparoscopic surgeries which are done as ambulatory surgery. 1,5 mg/kg slow bolus lidocaine iv followed by 1,5 mg/kg/h seems to be a reasonable dosing scheme.
Esmolol as a short acting beta blocker has been described to lower postoperative pain scores. Whereas it is possible to perform opioid free ambulatory anesthesia with esmolol, mostly esmolol is combined with low-dose opioids for more stable anesthesia. Whereas the above named components are easily introduced in clinical practice, the use and dosing of esmolol demand a bit more attention and experience of the anesthesiologist.
Enhanced postoperative multimodal regimens Interestingly most of the above named concepts are tailored to intraoperative not to postoperative use. This connects to the above stated sentences: ‘It is important to realise that one of the main problems is that we are not yet able to reliably identify the patients with severe postoperative pain after ambulatory surgery. That makes it more difficult to decide when to go for the enhanced options (and when not).’
For example, when the ambulatory patients awake with severe postoperative pain, it is too late for intraoperative use of esmolol of lidocaine iv (and iv application of ketamine (psychomimetic effects) or magnesium (local pain or global feeling of body heat) are not always appreciated by the patients).
Interestingly, recent studies have shown a significant analgetic effect of dexamethasone repeated on day 1 (or even day 1 and 2) postoperatively. Therefore it may be an option to discharge the patient with a 20 mg (taking in account the lesser oral bioavailability) tablet of dexamethason to be taken if severe postoperative pain appears to be present at home.
Recently, there also arose an increasing interest in antioxidative substances, like vitamine C, as a postoperative analgetic additives, which can also be easily administered orally at home (eg. in a single dose of 2 g).
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