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Opioids are important for postoperative analgesia but their use can be associated with numerous side effects. Transcutaneous electrical nerve stimulation (TENS) has been used for acute pain treatment and has dose-dependent analgesic effects, and therefore presents an alternative to intravenous (iv) opioids for postoperative pain relief. The aim of this meta-analysis was to compare high-frequency, high-intensity (HFHI or intense) TENS to iv opioids with regard to postoperative pain intensity, recovery time in the Post Anesthesia Care Unit (PACU) and opioid consumption after elective gynecological surgery.

Opioids are important for postoperative analgesia but their use can be associated with numerous side effects. Transcutaneous electrical nerve stimulation (TENS) has been used for acute pain treatment and has dose-dependent analgesic effects, and therefore presents an alternative to intravenous (iv) opioids for postoperative pain relief. The aim of this meta-analysis was to compare high-frequency, high-intensity (HFHI or intense) TENS to iv opioids with regard to postoperative pain intensity, recovery time in the Post Anesthesia Care Unit (PACU) and opioid consumption after elective gynecological surgery. We searched Medline, Embase, Web of Science, Cochrane, Amed and Cinahl for RCTs and quasi-experimental studies (2010–2022), and WHO and ClinicalTrials.gov for ongoing/unpublished studies. Meta-analysis and subsequent Trial Sequential Analysis (TSA) was performed for all stated outcomes. Quality of evidence was assessed according to GRADE. Only three RCTs met the inclusion criteria (362 participants). The surgical procedures involved surgical abortion, gynecologic laparoscopy and hysteroscopy. The applied TENS frequency was 80 Hz and intensity 40–60 mA. There was no difference in pain intensity according to Visual Analogue Scale (VAS) at discharge from PACU between the TENS and opioid group (MD VAS −0.15, 95 % CI −0.38 to 0.09) (moderate level of evidence). Time in PACU was significantly shorter in the TENS group (MD −15.2, 95 % −22.75 to −7.67), and this finding was manifested by TSA (high-level of evidence). Opioid consumption in PACU was lower in the TENS group (MD Morphine equivalents per patient mg −3.42, 95 % −4.67 to −2.17) (high-level of evidence). There was no detectable difference in postoperative pain relief between HFHI TENS and iv opioids after gynecological surgery. Moreover, HFHI TENS decreases recovery time and opioid consumption in PACU. HFHI TENS may be considered an opioid-sparing alternative for postoperative pain relief after gynecological surgery. PROSPERO CRD42021231048. [ABSTRACT FROM AUTHOR]

Posture has an effect on gastric emptying. In this study, we investigated whether posture influences the delay in gastric emptying induced by opioid analgesics. Ten healthy male subjects underwent 4 gastric emptying studies with the acetaminophen method. On two occasions the subjects were given a continuous infusion of remifentanil (0.2 microg. kg(-1). min(-1)) while lying either on the right lateral side in a 20 degrees head-up position or on the left lateral side in a 20 degrees head-down position. On two other occasions no infusion was given, and the subjects were studied lying in the two positions. When remifentanil was given, there were no significant differences between the two postures in maximal acetaminophen concentration (right side, 34 micromol. L(-1); versus left side, 16 micromol. L(-1)), time taken to reach the maximal concentration (94 versus 109 min), or area under the serum acetaminophen concentration time curve from 0 to 60 min (962 versus 197 min. micromol. L(-1)). In the control situation, there were differences between the postures in maximal acetaminophen concentration (138 versus 94 micromol. L(-1); P < 0.0001) and area under the serum acetaminophen concentration time curves from 0 to 60 min (5092 versus 3793 min. micromol. L(-1); P < 0.0001), but there was no significant difference in time taken to reach the maximal concentration (25 versus 47 min). Compared with the control situation, remifentanil delayed gastric emptying in both postures. We conclude that remifentanil delays gastric emptying and that this delay is not influenced by posture.