Pain physician最新文献

Background: Paresthesia-based spinal cord stimulation (SCS) depends upon dorsal column (DC) fiber activation to engage pain-relieving neural mechanisms. However, the mechanisms for 10-kHz paresthesia-free SCS have not been fully elucidated. Preclinical work has shown selective drive of inhibitory dorsal horn neurons, while other hypotheses suggest that DC fibers may be activated. To provide clinical data for guiding mechanism work, we analyzed paresthesia perception thresholds (PPT) over a range of low to high kHz frequency and compared those values to the stimulation parameters from the therapeutic 10-kHz SCS programs used by patients.

Objective: The goal of this study was to provide clinically relevant stimulation parameters for translational mechanism work.

Study design: Retrospective chart review of technical data collected during baseline evaluation from two prospective clinical studies.

Setting: Acute outpatient follow-up.

Methods: Data were extracted from study files of enrolled patients who had used fully implanted SCS for at least 3 months with leads positioned in the epidural space at the T8-T11 vertebral levels to treat their chronic intractable back and/or leg pain. PPTs had been measured using a bipole program at 10 kHz at pulse width (PW) = 30 µs, and at 50 Hz, 500 Hz, 1 kHz, and 5 kHz at PW = 80 µs. Therapeutic stimulation amplitudes for 10 kHz at 30 µs were obtained from patients' IPG log files at the time of study enrollment.

Results: PPTs were obtained from 23 patients with failed back surgery syndrome (11 M/ 12 F; 60 ± 15 years old). PPTs at PW = 80 µs were PPT (50 Hz) = 7.9 (5.7 - 9.7) mA, PPT (500 Hz) = 7.0 (5.2 - 9.1) mA, PPT(1 kHz) = 7.0 (5.5 --8.5) mA, and PPT (5 kHz) = 6.1 (4.1- 7.9) mA; all higher frequencies had statistically significantly lower PPTs than PPT(50 Hz at 80 µs). For 10 kHz at 30 µs, the PPT was higher than 15 mA for 13 (56%) of the subjects; for the remaining 44%, the PPT =  8.3  ± 4.0 mA was statistically significantly larger than the therapeutic stimulation pulse amplitudes = 2.4 ± 0.4 mA.

Limitations: Retrospective chart review, small number of patients.

Conclusions: Therapeutic 10-kHz SCS uses stimulation amplitudes far lower than the PPT, providing evidence that therapeutic 10-kHz SCS does not activate dorsal column axons.  Additionally, the PPT decreases with increasing kHz frequency, suggesting that a presumed asynchronous pattern of activation from kHz stimulation does not raise the threshold at which sensation occurs.

Background: The thoracodorsal artery perforator (TDAP) flap has been developed to improve the postoperative aesthetic and psychological states of patients who receive breast-conserving surgery (BCS); nonetheless, the TDAP flap exacerbates the pain that occurs at 2 surgical sites.

Objectives: This trial aimed to compare the efficacy of the rhomboid intercostal block (RIB) and the serratus anterior plane block (SAB) as postoperative analgesics for BCS.

Study design: Prospective randomized controlled clinical trial.

Setting: This clinical trial was conducted at Zagazig University Hospitals.

Methods: Eighty-four patients scheduled for BCS followed by a TDAP flap were randomly divided into 3 groups (of 28 patients each). Group C received general anesthesia, and groups SAB and RIB received SAB and RIB blocks, respectively, followed by general anesthesia. The cumulative tramadol consumption within 24 hours after the operation was the primary outcome. The postoperative pain score, first-rescue analgesic time, and sensory block coverage were the secondary outcomes.

Results: The 24-hour cumulative tramadol consumption and duration of the first rescue analgesic were significantly lower and longer, respectively, in the RIB group, than in the SAB group or the control group. The VAS score was lower in the RIB group than in the SAB or control group at all measurement times, except at 24 hours postoperatively, and the values among the groups were not significantly different. Dermatomal coverage of the anterior and posterior hemithorax extended from T2-T9 in the RIB group and from T2-T10 in the anterior hemithorax only in the SAB group.

Limitations: Both block procedures were applied as single shots, and their impact on chronic postoperative pain was not assessed; the observation may therefore be drawn that a continuous local anesthetic (LA) infusion catheter could be used to extend the period of analgesia.

Conclusion: Because of its ability to block both the anterior and posterior hemithorax, the RIB, is more efficient than the SAB at controlling acute pain and reducing opioid consumption in patients undergoing BCS followed by TDAP flaps; thus, the RIB can be employed as a potential alternative in these surgeries.

Background: Sevoflurane causes emergence agitation (EA) in up to 80% of pediatric patients.

Objectives: Using midazolam, dexmedetomidine (DEX), and gabapentin, this work aimed to assess the prophylactic effect of oral premedication on EA incidence experienced by pediatric patients during recovery from sevoflurane anesthesia.

Study design: Randomized controlled trial.

Setting: Kafrelsheikh University, Kafrelsheikh, Egypt.

Methods: This study was performed on 240 men and women aged 3 to 10 years who were scheduled for adenotonsillectomy. Patients were randomized into 4 equal-sized groups. Thirty minutes before general anesthesia, oral premedication was applied in the form an apple-flavored sugary fluid plus 0.5 mg/kg of midazolam in Group M, 4 µg/kg of DEX in Group D, 10 mg/kg of gabapentin in Group G, or no drugs whatsoever in Group P (placebo).

Results: The incidence of EA was reduced more greatly in the M, D, and G groups than in the P group, and the D group's incidence of EA was lower than that of the M or G groups. The severity of EA exhibited a more significant reduction in the M, D, and G groups than in Group P. Similarly, the time until extubation was more prolonged in the M, D, and G groups than it was in the P group. Hemodynamics measurements were significantly lower in Groups M, D, and G than in Group P, and the D group had a lower hemodynamics measurement than did the M or G groups. Sedation scores were greater in the D and G groups than in the P group, and the D group had a higher sedation score than did Group M.

Limitations: This study used a small sample, took place at a single center, and had a short follow-up period.

Conclusion: Premedication using oral midazolam, DEX, or gabapentin reduced the incidence of EA, and DEX provided the best sedation and hemodynamics of all.

Background: Evidence of the efficacy of spinal cord stimulation (SCS) has been well demonstrated as a method of pain control for patients who exhibit failed back surgery syndrome (FBSS), complex regional pain syndrome (CRPS), and inoperable peripheral vascular diseases (PVD) ("usual indications"). However, a long-term study comparing the usual indications for which SCS is employed with those of other intractable painful conditions is still lacking.

Objectives: To assess the long-term effectiveness of SCS treatment for both usual and unusual indications.

Study design: Observational study and original research.

Setting: This work was conducted at the Faculty of Medicine Siriraj Hospital, Mahidol University, Thailand.

Methods: We recruited patients undergoing SCS treatment for chronic refractory pain caused by various conditions and followed up on those patients for up to 36 months. The patients were divided into usual indications for SCS, including FBSS, CRPS, and PVD; and unusual indications for SCS, including chronic refractory neuropathic pain of various etiologies. Pain intensity, pain-related interference, and health-related quality of life (HRQOL) were collected at the baseline, 6 months, and one, 2, and 3 years after SCS implantation, and the values seen at each time point were compared to the baseline values.

Results: Forty-six patients were recruited, 30 of whom underwent successful SCS implantation (24 usual and 6 unusual indications). The overall pain intensity was significantly lower than it was at the baseline, decreasing from 6 to 3, 5, 4, 4 out of 10 at 6, 12, 24 and 36 months after implantation, respectively (P < 0.01). Pain-related interference and HRQOL tended to improve over time after implantation. Patients with usual indications had a significantly higher rate of trial-per-implant ratio than those with unusual indications, with an odd ratio of 5.14 (95% CI 1.36-19.50). Furthermore, patients with usual indications tended to see greater improvement and more constancy in pain intensity, pain-related interference, and HRQOL than those with unusual indications.

Limitations: This analysis was a single-center prospective study with a nonrandomized design and a relatively small sample size.

Conclusions: Overall, SCS is an effective long-term treatment for chronic refractory pain. However, patients with usual indications for SCS have a higher success rate in SCS trials and a trend toward better outcomes after SCS implantation than do patients with unusual indications.