Effects of continuous fascia iliaca compartment blocks for postoperative analgesia in patients with hip fracture

BACKGROUND: Effective analgesia is essential for the postoperative care of orthopedic patients. OBJECTIVES: To evaluate the efficacy of continuous fascia iliaca compartment block (FIB) as postoperative analgesia after hip fracture surgery, and to compare FIB with patient-controlled intravenous analgesia (PCIA) using fentanyl for 48 h postoperatively. METHODS: Patients with hip fractures who were scheduled for open reduction and internal fixation surgery using the antirotation proximal femoral nail technique were randomly assigned to the FIB or PCIA groups. Postoperative pain was assessed using a numeral rating scale at 2 h, 4 h, 6 h, 12 h, 24 h and 48 h after analgesia was started. Delirium, postoperative nausea and vomiting (PONV), and pruritus were also monitored. RESULTS: Patients in the FIB group reported less pain than those in the PCIA group (P=0.039, d=-0.3). The change in pain scores over time was similar between the two groups. There were six patients with PONV and five patients with pruritus in the PCIA group, while no PONV or pruritus was noticed in the FIB group (P=0.013). Ten (19.6%) patients in the FIB group and three (5.7%) patients in the PCIA group developed postoperative delirium (P=0.032, d=0.77). CONCLUSION: Continuous FIB is a safe and effective technique for postoperative analgesia after hip fracture surgery, making it an option for pain management in elderly patients with hip fractures.

Pain and cognitive dysfunction are the risk factors of delirium in elderly hip fracture Chinese patients.

AIMS: To observe the incidence of delirium in elderly hip fracture patients and search for the potential risk factors. METHODS: Patients over 60 years were included in this study. Gender, age, education level, fracture type, organic dysfunction, cognitive dysfunction, comorbidity, medication, time from admission to surgery, and pain intensity were collected and analyzed, together with laboratory assessments and surgery including surgery type, time in surgery and blood loss in surgery. RESULTS: 16 in 123 patients developed delirium. The incidence rate of delirium was 13% in the period of 6 days after surgery. Pain intensity and cognitive dysfunction were the risk factors. CONCLUSION: Pain intensity and cognitive impairment after hip fracture were found as the risk factors for development of delirium in elder Chinese patients. Prevention and management of delirium needs pain management pre- and post-operatively.

Local pain and spreading hyperalgesia induced by intramuscular injection of nerve growth factor are not reduced by local anesthesia of the muscle.

OBJECTIVES: Injections with local anesthesia for therapeutic and diagnostic purposes are common clinical practice. This double-blind placebo controlled study explores the rational of local anesthetic blocks for the detection of muscle pain as the primary generator in spreading hyperalgesic conditions. METHODS: Experimental muscle pain was induced by injections of nerve growth factor (NGF) in the left and right supraspinatus muscle of 11 healthy volunteers. One day later ropivacaine and saline were administered with ultrasound guidance in the left or right supraspinatus muscle in a randomized double-blind manner. Assessments before NGF, day 1 (before and after ropivacaine/saline), and day 7 included: visual analog scale (VAS) pain scores at rest and during shoulder shrugging, time until exercise interruption owing to pain, cutaneous pain sensitivity, pressure pain thresholds, and pain VAS during tonic pressure stimulation. Cutaneous and pressure pain sensitivity were assessed over the supraspinatus, infraspinatus, and deltoideus muscles, and at the web space between first and second finger. RESULTS: Increased VAS pain scores and increased pressure pain sensitivity of the supraspinatus and infraspinatus muscles were found in both sides one day after the NGF injection compared with baseline. One day after NGF injections, the time until participants stopped exercising was reduced compared with baseline. The increased muscle pain sensitivity was not normalized by intramuscular ropivacaine. Saline caused increased VAS pain scores compared with ropivacaine. DISCUSSION: Muscle pain and spreading hyperalgesia induced by NGF is maintained despite anesthesia of the primary nociceptive locus. This indicates that intramuscular injection of local anesthetics may not be a valid diagnostic method for primary muscle pain.

The inter- and intra-individual variance in descending pain modulation evoked by different conditioning stimuli in healthy men.

Background and purpose Conditioned pain modulation (CPM) is a phenomenon in which pain is inhibited by heterotopic noxious stimulation. It is not known how the experimental condition affects the magnitude of the CPM response and the inter-and intra-individual variations. It is important to get the information of the test-retest reliability and inter-individual variations of CPM to apply CPM as a diagnostic tool or for screening analgesic compounds. This study evaluated (1) the magnitude of CPM, (2) the inter-individual coefficient of variation (inter-CV) and (3) the intra-individual coefficient of variation (intra-CV) to (A) different stimulus modalities to evoke CPM and (B) different assessment sites. Methods Twelve healthy men (age 19-38 years) participated in this study. Cold pressor pain (CPP) (immersing the hand into cold water), tourniquet pain (cuff around the upper arm) and mechanical pressure pain (craniofacial region) were used in randomized order as conditioning stimuli (CS). The test stimulus (TS) was pressure pain applied to the right masseter muscle, left forearm and leg (bilateral tibialis anterior: TA). The responses were pressure pain thresholds (PPT), pressure pain tolerance (PPTol) thresholds and the pain intensity which was assessed on a visual analogue scale (VAS, 0-10 cm) following 1.4 and 1.6 × PPT applied to TA. The TS was applied before, during and 10 min after the CS. The intra-individual CV was estimated between different days. Results CPP induced the most powerful CPM on PPT (66.3 ± 10.0% increase), VAS ratings (41.5 ± 5.3% reduction) and PPTol (32.6±4.6% increase), especially at TA, and resulted in the smallest inter-CV (41.4-60.1%). Independently of the CS, the inter-CV in general showed that the recordings from the orofacial region and the forearm had smaller values than from the leg. The smallest intra-CV value was obtained in pain ratings with CPP (27.0%). Conclusions This study suggests that (1) the CPP evokes the largest CPM, (2) the leg as the assessment site results in the largest CPM responses and (3) the CPP causes the smallest inter- and intra-CV. Implication The present investigation implicates that the CPP is the most efficient conditioning stimulus to induce CPM when assessed by pressure pain thresholds.

Sensitization in patients with painful knee osteoarthritis.

Pain is the dominant symptom in osteoarthritis (OA) and sensitization may contribute to the pain severity. This study investigated the role of sensitization in patients with painful knee OA by measuring (1) pressure pain thresholds (PPTs); (2) spreading sensitization; (3) temporal summation to repeated pressure pain stimulation; (4) pain responses after intramuscular hypertonic saline; and (5) pressure pain modulation by heterotopic descending noxious inhibitory control (DNIC). Forty-eight patients with different degrees of knee OA and twenty-four age- and sex-matched control subjects participated. The patients were separated into strong/severe (VAS>or=6) and mild/moderate pain (VAS<6) groups. PPTs were measured from the peripatellar region, tibialis anterior (TA) and extensor carpi radialis longus muscles before, during and after DNIC. Temporal summation to pressure was measured at the most painful site in the peripatellar region and over TA. Patients with severely painful OA pain have significantly lower PPT than controls. For all locations (knee, leg, and arm) significantly negative correlations between VAS and PPT were found (more pain, more sensitization). OA patients showed a significant facilitation of temporal summation from both the knee and TA and had significantly less DNIC as compared with controls. No correlations were found between standard radiological findings and clinical/experimental pain parameters. However, patients with lesions in the lateral tibiofemoral knee compartment had higher pain ratings compared with those with intercondylar and medial lesions. This study highlights the importance of central sensitization as an important manifestation in knee OA.

Contribution of the local and referred pain from active myofascial trigger points in fibromyalgia syndrome.

The generalized hypersensitivity associated with fibromyalgia syndrome (FMS) may in part be driven by peripheral nociceptive sources. The aim of the study was to investigate whether local and referred pain from active myofascial trigger points (MTrPs) contributes to fibromyalgia pain. FMS patients and healthy controls (n=22 each, age- and gender-matched) were recruited. The surface area over the upper trapezius muscle on each side was divided into 13 sub-areas (points) of 1cm in diameter for each point. Pressure pain threshold (PPT) and the local and referred pain pattern induced by manual palpation at 13 points bilaterally in the upper trapezius were recorded. Results showed that PPT levels at all measured points were significantly lower in FMS than controls. Multiple active MTrPs (7.4+/-2.2) were identified bilaterally in the muscle in FMS patients, but no active MTrPs were found in controls. The mid-fiber region of the muscle had the lowest PPT level with the largest number of active MTrPs in FMS and with the largest number of latent MTrPs in controls. The local and referred pain pattern induced from active MTrPs bilaterally in the upper trapezius muscle were similar to the ongoing pain pattern in the neck and shoulder region in FMS. In conclusion, active MTrPs bilaterally in the upper trapezius muscle contribute to the neck and shoulder pain in FMS. Active MTrPs may serve as one of the sources of noxious input leading to the sensitization of spinal and supraspinal pain pathways in FMS.

Temporal summation of pressure pain during muscle hyperalgesia evoked by nerve growth factor and eccentric contractions.

Nerve growth factor (NGF) has a key role in the generation and potentiation of pain. Its centrally sensitizing effects may facilitate pain responses to noxious stimulus. This study assessed (1) the influence of NGF on delayed onset muscle soreness (DOMS) in shoulder muscles; and (2) the temporal summation of pressure pain during hyperalgesia induced by NGF and DOMS. In a blinded design, 10 healthy subjects were injected with NGF in the trapezius muscle on one side and with isotonic saline on the contralateral side as control. The subjects undertook shoulder eccentric exercise to induce DOMS in the shoulder muscles 3h after the injections. The soreness intensity to muscle contraction, pressure pain thresholds (PPT), and pain intensity to sequential stimuli (i.e. temporal summation at 1 and 30s inter-stimulus interval (ISI)) were assessed before injections - 3, 24h, and 4, 7, and 21 days after injections. The soreness intensity to muscle contraction significantly increased at 3 and 24h in both shoulders (P<0.05) and went back to baseline levels at day 7. The same development was seen in PPT as reduced thresholds (P<0.05). The NGF injected side had higher pain ratings during temporal summation at 1s ISI compared with the contralateral side 24h after injections. Intramuscular administration of NGF intensified the DOMS responses, evoking facilitated temporal summation. Central as well as peripheral sensitization mechanisms may play a role in the facilitation.

Spatial and temporal summation of pain evoked by mechanical pressure stimulation.

Chronic pain patients often suffer from widespread and long lasting pain. The integrative effect of combined spatial and temporal summation on pain intensity has not been quantitatively tested. The present study was designed to investigate: (1) if the size of the stimulation area would facilitate the temporal summation of pain to repetitive pressure stimulation, and (2) if temporal summation is effective when stimulating separated sites, repetitively. Twenty healthy male subjects participated in this study. The test sites were located on the bilateral upper trapezius and tibialis anterior muscles. The ten stimuli (each with a duration of 1s) were applied to a single site at three inter-stimulus intervals (ISI: 1, 5, 30s) using five different probe sizes (0.5, 1, 2, 4 and 8cm(2)). The stimulation intensity was equal to the pressure pain threshold (PPT) determined for each probe size. Similar repetitive stimulations at two inter-stimulus intervals (5s and 30s) using two sizes of probes (0.5cm(2) and 2cm(2)) were applied to ten separate sites. The PPT at the trapezius muscle decreased significantly with the increase in stimulus area from 0.5cm(2) to 8cm(2) (P<0.001) due to spatial summation. Temporal summation of pain was evoked by repetitive pressure stimuli on the same site for all ISI and was more pronounced at 5s and 30s ISI with larger probe areas (2, 4, and 8cm(2)) compared to smaller probe areas. There was no temporal summation of pain to stimuli with ISI 5 and 30s when stimulating the separated sites. The current study indicated that spatial summation facilitated the temporal summation of pain for stimuli given at 5s and 30s ISI. The combination of temporal and spatial integration of nociceptive input facilitates the pain intensity, suggesting that temporal summation is clinically relevant in conditions with widespread pain.

Gender effects on trapezius surface EMG during delayed onset muscle soreness due to eccentric shoulder exercise.

The purpose of this study was to investigate gender-specific motor control strategies during eccentric exercise and delayed onset muscle soreness (DOMS) in the shoulder region. Twelve healthy males and females participated in the study. Eccentric shoulder exercises were conducted on the dominant shoulder while the other side served as control. The exerted force, range of shoulder elevation, rating of perceived exertion, pain intensity, and surface electromyography (EMG) from the trapezius muscles were recorded and analyzed. A significant decrease in exerted force during exercise was only found in males despite similar rating of perceived exertion among genders. During eccentric exercise: males showed increasing root mean square (RMS) of the EMG while a decrease occurred for females, no difference between genders in mean power frequency of the EMG were seen. During static and dynamic contractions: no differences between genders in pain intensity or RMS were observed; RMS of the exercised side were lower than that of the control side (P<0.05) at 24 h after exercise. The results indicated a more prominent muscle fatigue resistance in females compared with males and mobilization of different muscle activation strategies during eccentric exercise. A protective adaptation to DOMS, i.e. decrease in RMS values was found with no gender differences.

Enhanced temporal summation of pressure pain in the trapezius muscle after delayed onset muscle soreness.

Temporal summation of muscle pain is an important factor in musculoskeletal pain as central integration of repetitive nociceptive input can be facilitated in musculoskeletal pain patients. The aim of this study is to evaluate changes in temporal summation of pressure pain after induction of delayed onset muscle soreness (DOMS) of the trapezius muscle. Sixteen healthy volunteers participated in the study. Temporal summation of pain was induced by sequential pressure stimulation by a computer-controlled algometer. Sequential stimulation consisting of ten stimuli (at pressure pain threshold intensity) was applied over the trapezius muscle. Stimulus duration was 1 s and inter-stimulus intervals (ISI) were 1, 5, 10, and 30 s, respectively. The pain was rated on a continuous visual analogue scale (VAS, 10 cm) after each stimulus and normalised to the VAS score from the first stimulus. DOMS was induced in the right trapezius muscle by eccentric shoulder exercises while the left trapezius muscle served as control. Temporal summation of pressure evoked pain was measured before and 24 h after the exercise. At 24 h after exercise, soreness intensity during shoulder elevation was 3.7+/-0.2 cm, while no soreness was observed on the control side. When sequential pressure stimulation was applied to the DOMS muscle, VAS scores for 1 s ISI progressively increased to a higher level than before exercise (VAS increase for the last stimulus: 0.8+/-0.2 cm vs. 0.6+/-0.1 cm, P<0.05), while VAS scores for ISI 5, 10, and 30 s were not increased. On the control side, significant increases in VAS scores was observed for all ISIs but not affected by contralateral DOMS. Facilitation of temporal summation for 1 s ISI indicated that DOMS may increase the central excitability besides involving peripheral sensitisation. During DOMS there was no potential for further nociceptor sensitisation by repeated noxious pressure stimuli, which may account for the diminishment of temporal summation evoked by pressure stimuli with ISI 5, 10, and 30 s. These data indicate that muscle soreness might facilitate the central components of temporal summation to mechanical stimulation.

Dynamic shoulder dynamometry: a way to develop delay onset muscle soreness in shoulder muscles.

A dynamic shoulder dynamometer has been designed to develop a vertical downward force over a measured range of motion, i.e. scapular elevation. The dynamometer is force-controlled to apply a required force within the range of motion. Calibration procedures were performed to assess the reliability of the force and displacement measurements. The system is designed to operate in isometric or eccentric conditions. For eccentric exercise the dynamometer has, for the first time, provided possibilities to elicit delay onset muscle soreness in shoulder muscles. In future, the apparatus will enable investigations of sensory-motor interactions in the shoulder region.

Delayed onset muscle soreness in neck/shoulder muscles.

The aim of the present study is to: (1) induce delayed onset muscle soreness (DOMS) in the neck and shoulder muscles; (2) compare the pressure pain sensitivity of muscle belly with that of musculotendinous tissue after DOMS; (3) examine the gender differences in the development of DOMS. An eccentric shoulder exercise was developed to induce DOMS on neck/shoulder muscles using a specially designed dynamometer. Eccentric shoulder contraction consisted of 5 bouts, each bout lasted 3min, with 3min rest period between each bout. The right shoulder was elevating against a downward pressure force of 110% maximal voluntary contraction force exerted by the dynamometer. Pressure pain thresholds (PPT) of 11 sites (seven sites measured were muscle belly and four sites were myotendinous area) on neck/shoulder region were measured before, immediately after, 24 and 48h after exercise. Pain intensity, pain area and index of McGill pain questionnaire were assessed and all were increased after exercise. DOMS was induced in the shoulder muscles. PPT was significantly decreased and reached lowest values at 24h. The muscle belly sites are more sensitive to pain than the musculotendinous sites. No gender differences were found in any of the parameters used to assess the development of DOMS. DOMS did not distribute evenly in the neck/shoulder region. Soreness after exercise in the neck and shoulder seems not to be among the conditions that produce predominant musculoskeletal pain in females.

Temporal summation of pain evoked by mechanical stimulation in deep and superficial tissue.

UNLABELLED: Temporal summation of deep tissue pain has been suggested to be facilitated in chronic musculoskeletal pain syndromes. This study aimed to test whether temporal summation of mechanical induced pressure pain is (1) more pronounced at short (1 second) interstimulus intervals (ISIs) compared with long ISI (30 seconds), (2) more potent than summation elicited by pure skin stimulation, and (3) attenuated in women compared with men. Twelve age-matched men and 12 women were included. A computer-controlled pressure stimulator with a probe surface of 1 cm2 was used to give 10 stimulations to the tibialis anterior, tibia periosteum, and the first web of the hand. Sequential stimulation at pressure pain threshold intensity was applied with different ISIs (1, 3, 5, 10, and 30 seconds). The pain intensity was assessed on a visual analog scale (VAS) after each individual stimulus. The VAS scores after the 10th stimulation with 1-second ISI were increased (P < .05) by 418% +/- 77%, 378% +/- 89%, and 234% +/- 66% compared with the first stimulation for tibia, tibialis anterior, and web, respectively. Temporal summation of pain was observed for all ISIs in tibialis anterior and tibia, eg, 30-second ISI evoked a VAS increase of 192% +/- 71 % (tibia) and 117% +/- 42% (tibialis anterior) compared with the first stimulation. The VAS score after the 10th web stimulation was smaller (P < .05) than that of the 10th tibialis anterior or tibia stimulation. A regression analysis between stimulation number and VAS score showed that the pain intensity increased progressively (1) more for 1-second ISIs compared with longer ISIs (P < .01) and (2) faster in deep tissue compared with skin (P < .01). No gender difference was observed. The temporal summation might be related to both central and peripheral mechanisms. PERSPECTIVE: Pain originating in deep tissue influences central pain processing systems more than superficial tissue. This might be of importance in patients with musculoskeletal pain.