Postural control and trunk stability on sway parameters in adults with and without chronic low back pain.

BACKGROUND: Postural sway changes often reflect functional impairments in adults with chronic low back pain (LBP). However, there is a gap in understanding how these individuals adapt their postural strategies to maintain stability. PURPOSE: This study investigated postural sway distance and velocity, utilizing the center of pressure (COP) and center of gravity (COG), between adults with and without LBP during repeated unilateral standing trials. METHODS: Twenty-six subjects with LBP and 39 control subjects participated in the study. Postural sway ranges, COP/COG sways, and sway velocities (computed by dividing path length by time in anteroposterior (AP) and mediolateral (ML) directions over 10 s) were analyzed across three unilateral standing trials. RESULTS: A significant group interaction in sway range difference was observed following repeated trials (F = 5.90, p = 0.02). For COG sway range, significant group interactions were demonstrated in both directions (F = 4.28, p = 0.04) and repeated trials (F = 5.79, p = 0.02). The LBP group demonstrated reduced ML sway velocities in the first (5.21 ± 2.43 for the control group, 4.16 ± 2.33 for the LBP group; t = 1.72, p = 0.04) and second (4.87 ± 2.62 for the control group, 3.79 ± 2.22 for the LBP group; t = 1.73, p = 0.04) trials. CONCLUSION: The LBP group demonstrated decreased ML sway velocities to enhance trunk stability in the initial two trials. The COG results emphasized the potential use of trunk strategies in augmenting postural stability and optimizing neuromuscular control during unilateral standing.

Normalized stability time analysis within the boundaries between adults with and without fear of falling.

BACKGROUND: The unilateral stance test, measured by the center of pressure (COP), has been widely used to identify balance deficits. However, there is a critical gap in understanding the specific COP thresholds on postural stability in adults with a fear of falling (FOF). AIMS: To investigate the normalized stability time, which was defined as the ratio of time spent within stability boundaries to the total test duration, under different visual conditions and specific thresholds between adults with and without FOF. METHODS: Twenty-one older adults with FOF and 22 control subjects completed the unilateral limb standing test in eyes-open and eyes-closed conditions. Normalized stability times were computed based on five pre-determined COP sway range thresholds: 10 mm, 15 mm, 20 mm, 25 mm, and 30 mm. RESULTS: Receiver operating characteristic analysis determined the diagnostic accuracy of FOF. There were significant differences in the effects of both visual conditions (F = 46.88, p = 0.001) and threshold settings (F = 119.38, p = 0.001) on stability time between groups. The FOF group significantly reduced normalized stability time at the 10 mm COP threshold under eyes-closed conditions (t = - 1.95, p = 0.03). DISCUSSION: The findings highlight the heightened sensitivity of the 10 mm COP threshold in identifying group variances in postural stability when eyes are closed. Moreover, the FOF group displayed a marked reduction in stability duration based on visual scenarios and normalized thresholds. CONCLUSION: The study highlights the need to account for both COP boundaries and visual conditions in adults with FOF. When assessing postural control during unilateral stances, clinicians must also give attention to non-visual cues.

Impact of Remimazolam versus Sevoflurane Anesthesia on Cerebral Oxygenation and Intracranial Pressure during Gynecological Laparoscopy with Mild Hypercapnia.

BACKGROUND Remimazolam has the advantage of better hemodynamic stability compared with other anesthetics. We compared the effects of remimazolam and sevoflurane on cerebral oxygenation, intracranial pressure, and intraoperative hemodynamic parameters during mild hypercapnia in patients undergoing laparoscopy in the Trendelenburg position. MATERIAL AND METHODS Sixty-two patients (20-65 years old) scheduled for gynecological laparoscopy were randomly allocated to either the remimazolam (n=31) or sevoflurane (n=31) group. Respiratory and hemodynamic parameters and regional cerebral oxygen saturation (rSO2) were recorded. Intracranial pressure was measured using the optic nerve sheath diameter (ONSD). RESULTS The change over time in rSO2 did not differ between groups (P=0.056). The change in ONSD over time showed a significant intergroup difference (P=0.002). ONSD significantly changed over time (P=0.034) in the sevoflurane group but not in the remimazolam group (P=0.115). The changes in mean arterial pressure and heart rate over time showed significant intergroup differences (P=0.045 and 0.031, respectively). The length of stay and the use of rescue antiemetics and analgesics in the postanesthetic care unit were significantly lower in the remimazolam group than in the sevoflurane group (P=0.023, 0.038, and 0.018, respectively). CONCLUSIONS Remimazolam can provide a favorable hemodynamic profile and attenuate the increase in ONSD during gynecological laparoscopy compared with sevoflurane anesthesia during lung-protective ventilation with mild hypercapnia. Remimazolam can provide faster and better postoperative recovery than sevoflurane anesthesia.

Postural adaptations within normalized stability between older adults with and without chronic low back pain.

BACKGROUND: Adaptations of dynamic balance performance are related to sway excursions in older adults with chronic low back pain (LBP). However, there is a lack of understanding on postural control within different thresholds of radius from the center of pressure (COP). PURPOSE: This study was conducted to compare the normalized stability based on the time-in-boundary (TIB) during repeated unilateral limb standing trials between subjects with and without chronic LBP. METHODS: There were 26 older adults with LBP and 39 control subjects who completed three trials of repeated unilateral limb standing on a force plat. RESULTS: The TIB based on the seven thresholds was analyzed, and the groups demonstrated a significant interaction on thresholds for TIB (F = 8.76, p = 0.01). The TIB was significantly different in the 10 mm (F = 4.01, p = 0.04), 15 mm (F = 5.21, p = 0.03), and 20 mm (F = 4.48, p = 0.04) radius of thresholds only in the second trial. However, there was no group difference on TIB at the first and third trials due to potential compensatory and/or adaptive reactions to avoid fall risks. CONCLUSION: The LBP group lacked postural stability within the thresholds less than a 20 mm radius at the second trial of unilateral standing. The significant group interaction with the thresholds indicates an adaptation strategy on sway thresholds. This postural reaction from repeated trials should be considered with sway excursion adjustments and fall prevention in older adults with LB.

Comparisons of Mechanical Power and Respiratory Mechanics in Pressure-Controlled Ventilation and Volume-Controlled Ventilation during Laparoscopic Cholecystectomy in Elderly Patients.

We compared the effects of pressure-controlled volume-guaranteed ventilation (PCV) and volume-controlled ventilation (VCV) on respiratory mechanics and mechanical power (MP) in elderly patients undergoing laparoscopy. Fifty patients aged 65-80 years scheduled for laparoscopic cholecystectomy were randomly assigned to either the VCV group (n = 25) or the PCV group (n = 25). The ventilator had the same settings in both modes. The change in MP over time was insignificant between the groups (p = 0.911). MP significantly increased during pneumoperitoneum in both groups compared with anesthesia induction (IND). The increase in MP from IND to 30 min after pneumoperitoneum (PP30) was not different between the VCV and PCV groups. The change in driving pressure (DP) over time were significantly different between the groups during surgery, and the increase in DP from IND to PP30 was significantly higher in the VCV group than in the PCV group (both p = 0.001). Changes in MP during PCV and VCV were similar in elderly patients, and MP increased significantly during pneumoperitoneum in both groups. However, MP did not reach clinical significance (≥12 J/min). In contrast, the PCV group had a significantly lower increase in DP after pneumoperitoneum than the VCV group.

The dynamic postural steadiness and stabilization time between older adults with and without recurrent low back pain.

BACKGROUND: Although postural control measures were reported to identify neuromuscular impairments, postural steadiness and stabilization time were not carefully investigated between subjects with and without recurrent low back pain (LBP). Research QuestionAre there group differences in the stabilization time, direction of sway, and dynamic postural steadiness index (DPSI) during one-leg standing? METHODS: Thirty-four control subjects and 29 subjects with recurrent LBP participated in the study. Each subject stood upright on a single leg with and without visual input. The outcomes were measured for standing duration (sec), direction of sway, and the DPSI, which included the vertical steadiness index (VSI). The VSI assesses fluctuations to standardize the vertical ground reaction forces on the force plate. RESULTS: The control group demonstrated significantly longer standing duration compared to the LBP group during the eyes-open condition (t = 3.55, p = 0.001). The LBP group demonstrated significantly faster stabilization time (t = 2.53, p = 0.01) in the sagittal plane. The DPSI demonstrated an excellent relationship with the VSI without visual input in the control group (r = 0.98, p = 0.001). The directions of sway demonstrated a significant interaction between groups (F = 9.29, p = 0.004). SIGNIFICANCE: Although standing duration in the eyes-open condition decreased in the LBP group, a faster stabilization time in the sagittal plane was evident compared to the control group to adapt postural stability. These results indicated that vertical dynamic steadiness with visual input might be important to enhance compensatory postural control.

Effect of Low or High Pressure Alveolar Recruitment Maneuver on Postoperative Pain and Quality of Recovery in Patients with Obesity Undergoing Laparoscopic Sleeve Gastrectomy.

Background: This study aimed to evaluate whether a low- or high-pressure alveolar recruitment maneuver (ARM) might reduce postoperative pain and improve the quality of recovery after laparoscopic bariatric surgery. Methods: 90 patients with a body mass index > 30 kg/m2 scheduled for laparoscopic sleeve gastrectomy were randomly assigned to control (n = 30), low ARM (n = 30), or high ARM groups (n = 30). For the low and high ARM groups, ARM was repeated five times to hold the peak airway pressure at 30 cmH2O and 60 cmH2O for 5 s, respectively, before removal of the trocar. Conventional methods to reduce post-laparoscopic pain, such as intraperitoneal saline irrigation, hemovac drainage, and gentle abdominal compression were performed in all patients, regardless of the assigned group. Results: Shoulder and surgical site pain scores 24 h postoperatively and rescue meperidine requirement were similar between the groups (p = 0.141, 0.101, and 0.82, respectively). The quality of recovery 40 (QoR40) score 24 h postoperatively was similar between the groups (p = 0.755). Postoperative pulmonary complications were similar between the groups (p = 0.124). Conclusion: Application of a low- or high-pressure ARM in addition to conventional methods to remove remnant peritoneal CO2 gas did not reduce postoperative shoulder or surgical site pain or improve the quality of recovery after laparoscopic sleeve gastrectomy.

Effect of Erector Spinae Plane Block on Postoperative Pain after Laparoscopic Colorectal Surgery: A Randomized Controlled Study.

The erector spinae plane (ESP) block can be used to reduce pain and opioid requirements after abdominal surgery. We evaluated the effect of the ESP block on postoperative pain score, analgesic use, and quality of recovery (QoR) score in patients undergoing laparoscopy. Fifty-nine patients undergoing elective laparoscopic colorectal surgery were randomly assigned to control (n = 30) or ESPB (n = 29) groups after anesthesia induction. In the ESPB group, an ultrasound-guided ESP block was performed immediately after induction using 20 mL of 0.5% ropivacaine bilaterally. The primary outcome was the postoperative pain score, which was evaluated using the 11-point numeric rating scale (NRS) (0 = no pain, 10 = worst imaginable pain), in the recovery room. NRS "at rest" and "on cough" and total dose of fentanyl rescue (in the recovery room) as well as NRS "at rest" and the cumulative administered fentanyl dose of patient-controlled analgesia (24 h post-surgery) were significantly lower in the ESPB group than in the control group. The postoperative QoR score did not differ between the groups. Bilateral ESP block after induction reduced pain scores and opioid requirements for 24 h postoperatively but did not improve the QoR in patients undergoing laparoscopic colorectal surgery.

Simultaneous 10 kHz and 40 Hz spinal cord stimulation increases dorsal horn inhibitory interneuron activity.

Since 1967, spinal cord stimulation (SCS) has been used to manage chronic intractable pain of the trunk and limbs. Low-intensity, paresthesia-free, 10 kHz SCS has demonstrated statistically- and clinically-superior long-term pain relief compared to conventional SCS. 10 kHz SCS has been proposed to operate via selective activation of inhibitory interneurons in the superficial dorsal horn. In contrast, 40 Hz SCS is presumed to operate largely via dorsal column fiber activation. To determine if these mechanisms may be implemented synergistically, we examined the effect of each type of stimulation both independently and simultaneously on putatively inhibitory and putatively excitatory neurons in the superficial dorsal horn. When 10 kHz SCS was applied relatively caudally to the measured spinal segment, simultaneous with 40 Hz SCS applied relatively rostrally to that spinal segment, inhibitory interneurons demonstrated a median increase of 26 spikes/s compared to their baseline firing rates. Median firing rate increases of inhibitory interneurons were 8.7 and 5.1 spikes/s during 40 Hz SCS applied rostrally and 10 kHz SCS applied caudally, respectively. By comparison, the median firing rate of excitatory interneurons increased by 4.1 spikes/s during simultaneous 40 Hz SCS applied rostrally and 10 kHz SCS applied caudally. Median firing rate increases of excitatory interneurons were 13 and 0.8 spikes/s during 40 Hz SCS applied rostrally and 10 kHz SCS applied caudally, respectively. This suggests that simultaneously applying 10 kHz SCS caudally and 40 Hz SCS rostrally may provide greater pain relief than either type of SCS alone by increasing the firing rates of inhibitory interneurons, albeit with greater excitatory interneuron activation.

Low-Intensity 10 kHz Spinal Cord Stimulation Reduces Behavioral and Neural Hypersensitivity in a Rat Model of Painful Diabetic Neuropathy.

Background: Low-intensity 10 kHz spinal cord stimulation (SCS) has been shown to provide pain relief in patients with chronic pain resulting from diabetic peripheral neuropathy (DPN). However to date, there have been no studies of 10 kHz SCS in animal models of diabetes. We aimed to establish correlative data of the effects of this therapy on behavioral and electrophysiological measures in a DPN model. Methods: Twenty-five adult male Sprague-Dawley rats were injected once intraperitoneally with 60 mg/kg streptozotocin (STZ) to induce diabetes over a subsequent 4 w period, while 4 naïve control animals were not injected. After approximately 21 d, 12 of STZ-injected rats had mini epidural SCS leads implanted: 8 received continuous low intensity (~30% motor threshold) 10 kHz SCS, and 4 received sham SCS (0 mA) over 7 d. Behavioral assays (von Frey filament probe of hindpaw) were measured in 18 animals and in vivo dorsal horn electrophysiological studies (receptive field; response to afferent brush, von Frey probe, pinch) were performed in 17 animals. Results: Across behavioral assays of mechanical allodynia and electrophysiological assays of receptive field size and mechanosensitivity, diabetic animals stimulated with 10 kHz SCS showed statistically significant improvements compared to sham SCS. Conclusion: Low-intensity 10 kHz SCS produced several measures associated with a reduction of pain in diabetic rodent models that may help explain the clinical benefits of 10 kHz SCS in patients with painful diabetic neuropathy.

Comparison of kinematic similarity index during gait between adults with and without nonspecific chronic neck pain.

BACKGROUND: Individuals with nonspecific chronic neck pain (NP) walk with a stiffer spine. However, there is a lack of understanding on kinematic similarities on the limbs during gait between individuals with and without NP. RESEARCH QUESTION: Are there differences in gait parameters and the kinematic similarity index (SI) between individuals with and without NP? METHODS: Eighteen individuals with NP and 17 controls participated in this study. A three-dimensional motion capture system and two force plates were utilized to measure kinematic changes of the upper and lower limbs during gait. The gait parameters included cadence, speed, stride length, and step width. The SI calculations were compared based on the response vectors from the NP group and the prototype response vectors from the control participants. The SI values at 5% intervals of the entire gait cycle were compared between groups. RESULTS: Although the gait parameters were not significantly different between groups, the SI values of the control group were significantly higher than the NP group during gait (0.98 ± 0.02 vs. 0.95 ± 0.03), especially at the midstance (10-30 %) and swing (80-90 %) phases. Also, the standard deviation of the SI decreased in the control group when compared to the NP group (0.02 ± 0.01 vs. 0.04 ± 0.02). SIGNIFICANCE: The SI was a useful measure to differentiate similarities between groups in the gait cycle at specific phases. These results indicated that the NP group demonstrated a greater variation of walking patterns during the midstance and swing phases and displayed altered compensatory gait. Clinicians need to consider the similarities of the kinematic changes for the NP group to aid in detection of limb motion differences and the resulting gait dysfunction.

Differential Modulation of Dorsal Horn Neurons by Various Spinal Cord Stimulation Strategies.

New strategies for spinal cord stimulation (SCS) for chronic pain have emerged in recent years, which may work better via different analgesic mechanisms than traditional low-frequency (e.g., 50 Hz) paresthesia-based SCS. To determine if 10 kHz and burst SCS waveforms might have a similar mechanistic basis, we examined whether these SCS strategies at intensities ostensibly below sensory thresholds would modulate spinal dorsal horn (DH) neuronal function in a neuron type-dependent manner. By using an in vivo electrophysiological approach in rodents, we found that low-intensity 10 kHz SCS, but not burst SCS, selectively activates inhibitory interneurons in the spinal DH. This study suggests that low-intensity 10 kHz SCS may inhibit pain-sensory processing in the spinal DH by activating inhibitory interneurons without activating DC fibers, resulting in paresthesia-free pain relief, whereas burst SCS likely operates via other mechanisms.

Comparison of remifentanil concentrations with and without dexmedetomidine for the prevention of emergence cough after nasal surgery: a randomized double-blinded trial.

BACKGROUND: Preventing emergence cough after nasal surgery is critical. Emergence cough can provoke immediate postoperative bleeding, which leads to upper airway obstruction. In the present study, we compared the effect-site concentration (Ce) of remifentanil to prevent emergence cough after propofol anesthesia for nasal surgery when remifentanil was or was not combined with dexmedetomidine. METHODS: Forty-seven patients with propofol-remifentanil anesthesia for nasal surgery were randomly assigned to a dexmedetomidine group (Group D, n = 23) or a saline group (Group S, n = 24). Group D and Group S were infused with dexmedetomidine (0.5 µg/kg) and saline, respectively, for 10 min before the completion of surgery. A predetermined Ce of remifentanil was infused until extubation. Remifentanil Ce to prevent cough in 50 and 95% of patients (EC50 and EC95) was estimated using modified Dixon's up-and-down method and isotonic regression. Hemodynamic and recovery parameters were recorded. RESULTS: The EC50 of remifentanil Ce was significantly lower in Group D than in Group S (2.15 ± 0.40 ng/mL vs. 2.66 ± 0.36 ng/mL, p = 0.023). The EC95 (95% CI) of remifentanil Ce was also significantly lower in Group D [2.75 (2.67-2.78) ng/mL] than in Group S [3.16 (3.06-3.18) ng/mL]. Emergence and recovery variables did not differ between the two groups. CONCLUSION: The remifentanil EC50 to prevent cough after propofol-remifentanil anesthesia was significantly lower (approximately 19%) when a combination of remifentanil and 0.5 µg/kg dexmedetomidine was used than when remifentanil infusion alone was used in patients undergoing nasal surgery. Therefore, the Ce of remifentanil may be adjusted to prevent emergence cough when used in combination with dexmedetomidine. TRIAL REGISTRATION: ClinicalTrials.gov ( NCT03622502 , August 9, 2018).

Trends in opioid prescribing practices in South Korea, 2009-2019: Are we safe from an opioid epidemic?

Opioid prescribing data can guide regulation policy by informing trends and types of opioids prescribed and geographic variations. In South Korea, the nationwide data on prescribing opioids remain unclear. We aimed to evaluate an 11-year trend of opioid prescription in South Korea, both nationally and by administrative districts. A population-based cross-sectional analysis of opioid prescriptions dispensed nationwide in outpatient departments between January 1, 2009, and December 31, 2019, was conducted for this study. Data were obtained from the Health Insurance Review & Assessment Service. The types of opioids prescribed were categorized into total, strong, and extended-release and long-acting formulation. Trends in the prescription rate per 1000 persons were examined over time nationally and across administrative districts. There are significant increasing trends for total, strong, and extended-release and long-acting opioid prescriptions (rate per 1000 persons in 2009 and 2019: total opioids, 347.5 and 531.3; strong opioids, 0.6 and 15.2; extended-release and long-acting opioids, 6.8 and 82.0). The pattern of dispensing opioids increased from 2009 to 2013 and slowed down from 2013 to 2019. The rate of opioid prescriptions issued between administrative districts nearly doubled for all types of opioids. Prescription opioid dispensing increased substantially over the study period. The increase in the prescription of total opioids was largely attributed to an increase in the prescription of weak opioids. However, the increase in prescriptions of extended-release and long-acting opioids could be a future concern. These data may inform government organizations to create regulations and interventions for prescribing opioids.

Effects of deep neuromuscular block with low-pressure pneumoperitoneum on respiratory mechanics and biotrauma in a steep Trendelenburg position.

We hypothesized that deep neuromuscular blockade (NMB) with low-pressure pneumoperitoneum (PP) would improve respiratory mechanics and reduce biotrauma compared to moderate NMB with high-pressure PP in a steep Trendelenburg position. Seventy-four women undergoing robotic gynecologic surgery were randomly assigned to two equal groups. Moderate NMB group was maintained with a train of four count of 1-2 and PP at 12 mmHg. Deep NMB group was maintained with a post-tetanic count of 1-2 and PP at 8 mmHg. Inflammatory cytokines were measured at baseline, at the end of PP, and 24 h after surgery. Interleukin-6 increased significantly from baseline at the end of PP and 24 h after the surgery in moderate NMB group but not in deep NMB group (Pgroup*time = 0.036). The peak inspiratory, driving, and mean airway pressures were significantly higher in moderate NMB group than in deep NMB group at 15 min and 60 min after PP (Pgroup*time = 0.002, 0.003, and 0.048, respectively). In conclusion, deep NMB with low-pressure PP significantly suppressed the increase in interleukin-6 developed after PP, by significantly improving the respiratory mechanics compared to moderate NMB with high-pressure PP during robotic surgery.

Low-intensity, Kilohertz Frequency Spinal Cord Stimulation Differently Affects Excitatory and Inhibitory Neurons in the Rodent Superficial Dorsal Horn.

Since 1967, spinal cord stimulation (SCS) has been used to manage chronic intractable pain of the trunk and limbs. Compared to traditional high-intensity, low-frequency (<100 Hz) SCS that is thought to produce paresthesia and pain relief by stimulating large myelinated fibers in the dorsal column (DC), low-intensity, high-frequency (10 kHz) SCS has demonstrated long-term pain relief without generation of paresthesia. To understand this paresthesia-free analgesic mechanism of 10 kHz SCS, we examined whether 10 kHz SCS at intensities below sensory thresholds would modulate spinal dorsal horn (DH) neuronal function in a neuron type-dependent manner. By using in vivo and ex vivo electrophysiological approaches, we found that low-intensity (sub-sensory threshold) 10 kHz SCS, but not 1 kHz or 5 kHz SCS, selectively activates inhibitory interneurons in the spinal DH. This study suggests that low-intensity 10 kHz SCS may inhibit pain sensory processing in the spinal DH by activating inhibitory interneurons without activating DC fibers, resulting in paresthesia-free pain relief.

Methodology for quantifying excitability of identified projection neurons in the dorsal horn of the spinal cord, specifically to study spinal cord stimulation paradigms.

BACKGROUND: Using in and ex vivo preparations, electrophysiological methods help understand the excitability of biological tissue, particularly neurons, by providing microsecond temporal resolution. However, for in vivo recordings, in the context of extracellular recordings, it is often unclear precisely which type of neuron the tip of the electrode is recording from. This is particularly true in the densely-populated central nervous system, such as the spinal cord dorsal horn at both superficial and deep levels. NEW METHOD: Here, we present a detailed protocol for the identification of superficial dorsal horn spinal cord neurons that receive peripheral input and project to the brain, using multiple surgical laminectomies and the careful placement of electrodes. Once a superficial projection unit was found, quantification to electrical peripheral stimulation was performed using a Matlab algorithm to form a template of projection neuron response to controlled C2 stimulation and accurately match this to the responses from peripheral stimulation. RESULTS: These superficial spinal projection neurons are normally activated by noxious peripheral stimuli, so we adopted a well-characterised wind-up protocol to obtain a neuronal excitability profile. Once achieved, this protocol allows for testing specific interventions, either pharmacological or neuromodulatory (e.g., spinal cord stimulation) to see how these affect the neuron's excitability. This preparation is robust and allows the accurate tracking of a projection neuron for over 3-h. COMPARISON WITH EXISTING METHOD(S): Currently, most existing methods record from dorsal horn neurons that are often profiled based on their excitability to different peripherally-applied sensory modalities. While this is well-established, it fails to discriminate between interneurons and projection neurons, which is important as these two populations signal via distinctly different neuronal networks. Using the approach detailed here will result in studies with improved mechanistic understanding of the signal integration and processing that occurs in the superficial dorsal horn. CONCLUSIONS: The refinements detailed in this protocol allow for more comprehensive studies to be carried out that will help understand spinal plasticity, in addition to many considerations for isolating the relevant neuronal population when performing in vivo electrophysiology.

Effects of ventilatory strategy on arterial oxygenation and respiratory mechanics in overweight and obese patients undergoing posterior spine surgery.

Prolonged inspiratory to expiratory (I:E) ratio ventilation may improve arterial oxygenation or gas exchange and respiratory mechanics in patients with obesity. We performed a randomised study to compare the effects of the conventional ratio ventilation (CRV) of 1:2 and the equal ratio ventilation (ERV) of 1:1 on arterial oxygenation and respiratory mechanics during spine surgery in overweight and obese patients. Fifty adult patients with a body mass index of ≥25 kg/m2 were randomly allocated to receive an I:E ratio either l:2 (CRV; n = 25) or 1:1 (ERV; n = 25). Arterial oxygenation and respiratory mechanics were recorded in the supine position, and at 30 minutes and 90 minutes after placement in the prone position. The changes in partial arterial oxygen pressure (PaO2) over time did not differ between the groups. The changes in partial arterial carbon dioxide pressure over time were significantly different between the two groups (P = 0.040). The changes in mean airway pressure (Pmean) over time were significantly different between the two groups (P = 0.044). Although ERV provided a significantly higher Pmean than CRV during surgery, the changes in PaO2 did not differ between the two groups.

Remifentanil-Sparing Effect of Pectoral Nerve Block Type II in Breast Surgery under Surgical Pleth Index-Guided Analgesia during Total Intravenous Anesthesia.

The pectoral nerve block type II (Pecs II block) can provide adequate perioperative analgesia in breast surgery. The surgical pleth index (SPI) is used to monitor the nociception balance using pulse oximetry. We investigated the remifentanil-sparing effect of Pecs II block under SPI guided analgesia during total intravenous anesthesia (TIVA). Thirty-nine patients undergoing breast surgery under remifentanil-propofol anesthesia were randomly assigned to the intervention (Pecs group, n = 20) or control group (n = 19). Remifentanil and propofol concentrations were adjusted to maintain an SPI of 20-50 and a bispectral index of 40-60, respectively. The Pecs group received an ultrasound-guided Pecs II block preoperatively using 30 mL of 0.5% ropivacaine. Total infused remifentanil during the surgery was significantly less in the Pecs group than in the control group (6.8 ± 2.2 µg/kg/h vs. 10.1 ± 3.7 µg/kg/h, p = 0.001). Pain scores on arrival at the postanesthetic care unit (PACU) (3 (2-5) vs. 5 (4-7)) and the rescue analgesic requirement in the PACU (9 vs. 2) was significantly lower in the Pecs group than in the control group. In conclusion, Pecs II block was able to reduce the intraoperative remifentanil consumption by approximately 30% and improve the postoperative pain in PACU in patients undergoing breast surgery under SPI-guided analgesia during TIVA.

Reliability of the Kinematic Steadiness Index during one-leg standing in subjects with recurrent low back pain.

PURPOSE: To assess the reliability of standing time and the Kinematic Steadiness Index (KSI) in one-leg standing compared with the Timed Up and Go (TUG) test while considering anthropometric factors in subjects with recurrent low back pain (LBP). METHODS: Sixty-six individuals participated in the study. The data were collected on two different days, 1 week apart. The KSI of the core spine, using video motion-capture techniques, was based on the relative standing time and relative standstill time. The intraclass correlation coefficient (ICC2,1) was compared for the reliability between measures. The covariates, such as age, Body Mass Index, and the Oswestry Disability Index (ODI), were analyzed for any interactions based on these measures. RESULTS: The standing time (t = - 1.01, p = 0.32) and the KSI (t = - 1.70, p = 0.09) were not significantly different between measures. The TUG results were not different between measures (t = 1.01, p = 0.32). The Cronbach's alpha for the standing time was 0.84, for KSI was 0.89, and for TUG was 0.76. The standing time and KSI demonstrated an interaction with age, while the TUG demonstrated an interaction with the ODI score. CONCLUSIONS: The KSI during one-leg standing could help to develop a practical tool to justify quantity and quality of balance outcome measures, which identify balance deficits and core spine rehabilitation strategies in subjects with recurrent LBP.