New oral anticoagulants and regional anaesthesia.

The new oral anticoagulants are approved for a variety of clinical syndromes, including the prevention of stroke in atrial fibrillation, acute coronary syndromes, treatment of venous thromboembolism (VTE), and prevention of venous thrombosis after total joint surgery or hip fracture. Published guidelines have differing recommendations on the safe interval between discontinuation of the anticoagulant and performance of neuraxial procedures and between the interventional procedure and redosing of the drug. While two to three half-life intervals might be acceptable in patients who are at high risk for VTE or stroke, an interval of four to six half-lives between discontinuation of the drug and neuraxial injections is probably safer in most patients at low risk of thrombosis. In those with renal disease, the interval should be based on creatinine clearance. After a neuraxial procedure or removal of an epidural catheter, anticoagulants can be resumed within 24-48 h in most patients, but they can be taken sooner in patients who are at higher risk for VTE or stroke, that is, 24 h minus the time to peak effect of the drug. The new antiplatelet drugs prasugrel and ticagrelor should be stopped 7 or 5 days, respectively, before a neuraxial injection and can be restarted 24 h later. In selected situations, laboratory monitoring of the anticoagulant effect is appropriate, and reversal agents are suggested when there is a need to rapidly restore haemostatic function.

Determination of residual antiplatelet activity of clopidogrel before neuraxial injections.

BACKGROUND: Guidelines recommend discontinuation of clopidogrel for 7 days before a neuraxial injection, while other directives suggest that 5 days might be adequate. We examined the time course of antiplatelet activity after clopidogrel discontinuation in patients undergoing epidural injections. METHODS: Thirteen patients were studied at baseline, 3, 5, and 7 days after discontinuation of clopidogrel. P(2)Y(12) determinations were performed using the VerifyNow(®) assay (Accumetrics, San Diego, CA, USA), and clot closure times with stimulation by collagen/epinephrine and collagen/adenosine diphosphate using the PFA-100(®) (Platelet Function Analyzer, Siemens Diagnostics, Deerfield, IL, USA). Repeated-measures ANOVA was used to evaluate P(2)Y(12) platelet reaction units, PFA-100 closure times, and per cent P(2)Y(12) inhibition values. Wilcoxon's signed-rank test was used to compare the frequencies of ≥30%, 11-29%, and ≤10% platelet inhibition between the baseline and subsequent sampling points after discontinuation of clopidogrel. RESULTS: On day 3 after clopidogrel discontinuation, two subjects had ≥30%, seven subjects had 11-29%, and four subjects had ≤10% platelet inhibition; the corresponding numbers were 0, 3, and 10 subjects on day 5 (P=0.04). There were no differences between the ≥30%, 11-29%, and <10% platelet inhibition groups between days 5 and 7 (0, 0, and 13 subjects, P=1.0). PFA-ADP closure times were normal throughout the study period except in one patient. CONCLUSIONS: These findings support the recommendation that discontinuation of clopidogrel for 5 days allows >70% of platelet function and might be adequate before a neuraxial injection is performed.

Epidural steroid injections: update on efficacy, safety, and newer medications for injection.

The best evidence for epidural injection appears to be in the setting of radicular pain with epidural steroid and non-steroid injections more efficacious than non-epidural injections. Studies showed the efficacy of non-particulate steroid to approach the efficacy of particulate steroid and very limited comparisons demonstrated no significant difference between epidural steroid and epidural non-steroid (local anesthetic) injection. Preliminary studies evaluating epidural injection of disease modifying anti-rheumatic drugs such etanercept and tocilizumab showed conflicting results and had significant limitations. Randomized studies support better efficacy of transforaminal injection due to greater incidence of ventral epidural spread of injectate when compared to interlaminar injection. Thus, the transforaminal approach is recommended when unilateral radicular pain is limited to one nerve root. However, the transforaminal approach is associated with greater incidence of central nervous system injury, including paraplegia, attributed to embolization of the particulate steroid. Recent studies showed that non-particulate steroids potentially last as long as particulate steroids. Therefore non-particulate steroid should be used in initial transforaminal epidural injection. Future studies should look into the role of adjunct diagnostic aids, including digital subtraction angiography, in detecting intravascular injection and the ideal site of needle placement, whether it is the safe triangle or the triangle of Kambin. Finally, the role of epidural disease -modifying antirheumatic drugs in the management of back pain needs to be better elucidated.

Cerebrospinal fluid leak treated by aspiration and epidural blood patch under computed tomography guidance.

BACKGROUND AND OBJECTIVES: Cerebrospinal fluid (CSF) leakage secondary to surgery of the spine is usually treated by drainage of CSF through a subarachnoid catheter or surgical repair of the dural tear. We present 2 cases in which the pseudomeningocele was treated by aspiration of the leaked CSF and blood patch under computed tomography (CT) guidance. CASE REPORT: Two patients had headache after spine surgery. Physical examination showed a bulging accumulation of fluid at the laminectomy site. Aspiration of the fluid followed by injection of the patients' blood was performed aseptically under CT guidance. The patients had resolution of their headache, and follow-up showed no recurrence of the CSF leak. CONCLUSIONS: CSF leak secondary to a surgical tear of the dura can be successfully treated by aspiration of the fluid followed by injection of the patient's blood. CT guidance is recommended to assess the extent of the CSF leakage, determine the degree of evacuation of the leaked CSF, and to confirm the injection of the blood into the epidural space and the space created by the pseudomeningocele.

Pain on intramuscular injection of bupivacaine, ropivacaine, with and without dexamethasone.

BACKGROUND AND OBJECTIVES: We wished to determine which long-acting local anesthetic would produce the least pain on injection for treatment of myofascial pain disorders. We compared the pain on intramuscular injection of bupivacaine, ropivacaine, bupivacaine with dexamethasone, ropivacaine with dexamethasone, and needle placement alone. METHODS: Thirty volunteers received 5 injections each: (1) needle only, (2) bupivacaine 0.5%, (3) ropivacaine 0.5%, (4) bupivacaine 0.5% with dexamethasone 0.13 mg/mL, and (5) ropivacaine 0.5% with dexamethasone 0.13 mg/mL. The injections were made in the volunteers' upper trapezius muscles; there was a 15-minute interval between injections. The sequence of injections was randomized by Latin square design. The intensity of pain was rated on a 0 to 10 cm visual analogue scale (VAS) score. Neither the investigator nor the volunteer was aware of the nature of the injectate. The pH of the injected solutions was checked to determine if differences in the intensity of pain on injection were due to differences in the pH of the solutions. RESULTS: The VAS pain scores were 3.1 +/- 2.4 for needle only, 4.4 +/- 2.8 for bupivacaine, 2.5 +/- 2.0 for ropivacaine, 4.7 +/- 2.7 for bupivacaine/dexamethasone, and 3.7 +/- 2.2 for ropivacaine/dexamethasone. The pain on injection of ropivacaine was significantly less than the pain on injection of bupivacaine or bupivacaine/dexamethasone. The pH values of the solutions were as follows: (1) bupivacaine, 5.50; (2) ropivacaine, 5.57; (3) bupivacaine/dexamethasone, 6.64; and (4) ropivacaine/dexamethasone, 6.60. CONCLUSIONS: The pain on intramuscular injection of bupivacaine is significantly more intense than with ropivacaine. The difference in the intensity of the pain on injection between bupivacaine and ropivacaine does not appear to be related to differences in pH. The results of our study have implications on the choice of the local anesthetic used in trigger point injections.

Pulsed radiofrequency: a critical review of its efficacy.

Pulsed radiofrequency is a growingly popular pain treatment modality. However, its clinical efficacy remains controversial. In this review, the available literature on pulsed radiofrequency is critically analysed to determine its clinical efficacy. Our search of the literature for pulsed radiofrequency yielded 341 citations; after reviewing the abstracts we found 51 relevant articles. There were 4 review articles: 44 articles pertained to the application of pulsed radiofrequency by an electrode placed in the vicinity of a neural structure. Of these only two were randomised controlled trials. Of the remaining 42 articles, one was a non-randomised controlled trial, three were prospective uncontrolled trials: there were six retrospective studies, 11 case reports, eight laboratory studies, two position papers, five editorials and seven items of correspondence, while one publication reported two studies. Three articles pertained to transcutaneous application of pulsed radiofrequency. Of the two randomised controlled trials, one reported efficacy of the pulsed radiofrequency while the other reported it to be ineffective. The majority of the uncontrolled and observational studies reported clinical efficacy of pulsed radiofrequency, however many of these studies had limitations. Further randomised controlled clinical trials are recommended in order for the practising pain physician to clearly understand the role of pulsed radiofrequency in the treatment of various chronic pain syndromes.

Clinical experience with the peribulbar block for ophthalmologic surgery.

BACKGROUND AND OBJECTIVES: The peribulbar block is a safe and reliable alternative to the retrobulbar block. In this clinical report, we describe the anatomy of the orbit and the technique involved in performing the block. METHODS: The technique is not new, and modifications from the original paper by Mandel and Davis are few but significant. Complications include peribulbar hemorrhage, perforation of the globe and intravascular injection. RESULTS: In our experience of 2600 peribulbar blocks, we have seen five patients with minor peribulbar hemorrhage. CONCLUSIONS: Supplementation of the block was required in 3% of the patients.

Delayed onset of epidural anesthesia in patients with back pain.

Onset and completeness of anesthesia were compared in 15 patients with back pain or sciatica and in 10 patients without back pain given lumbar epidural anesthesia with 20 to 25 ml of 1.5% mepivacaine, 80 mg of methylprednisolone, and 1:200,000 epinephrine. Sensory block was complete within 30 minutes in patients without back pain. Eleven of 15 (73%) patients with back pain had delayed onset of anesthesia ranging from 35 to 95 minutes. The difference between the two groups was statistically significant (p less than 0.001). When there was a delay, the affected nerve roots were blocked 10 to 70 minutes after the contralateral unaffected roots. Differences in time of onset between affected nerves and contralateral nerves were also significant (p less than 0.01). The nerve roots involved, as determined from the myelogram or the electromyogram, or those adjacent to them, were the roots with delayed onset of block. Any effect of the steroid on nerve blockade was ruled out as there was solid anesthesia in patients without back pain.

Postdural puncture headache in patients with chronic pain.

The incidence of headache after dural puncture in patients being treated for chronic pain was studied prospectively. Dural punctures were performed in 142 patients and headache developed in 13 (9.2%). Four of 32 patients (12.5%) who underwent diagnostic differential spinal and nine of 110 patients (8.2%) given intrathecal steroid injection developed headache. There was a 10.7% incidence of headache when a 22-gauge needle was used as compared to 5% with a 25-gauge needle. This difference was not statistically significant. The incidence decreased with increasing age. The incidence of postdural puncture headache in chronic pain patients does not differ significantly from that previously reported for surgical patients. All patients who developed headache responded to treatment which consisted of intravenous and oral fluids, analgesics, bed rest, and, if necessary, epidural blood patch.

Sign of complete sympathetic blockade: sweat test or sympathogalvanic response?

The sensitivity, specificity, and accuracy of the cobalt blue and ninhydrin sweat tests were compared with the sympathogalvanic response (SGR) in assessment of complete sympathetic blockade. Patients were randomly assigned to receive epidural administration of either preservative-free physiologic saline solution and 80 mg methylprednisolone (group I, control group, 9 patients) or 1.5% lidocaine with 80 mg methylprednisolone (group II, sympathetic blocked group, 10 patients). In group I, there was one false positive SGR (absence of SGR) before the block and there were four false positive SGRs after the block. In comparison, there were no false positive sweat tests (absence of sweating) before and after injection in group I. In group II, there were three false positive SGRs and no false positive sweat test before injection. After injection, one patient with an upper level of sensory blockade at T5 had persistent SGRs and positive sweat tests (false negative results). The study showed the sensitivity of the SGR and the sweat tests to be 90%. The specificity of the SGR was 56% compared to 100% for the sweat tests. The accuracy of the SGR was 74% compared to 95% for the sweat tests.

The effect of low-dose bupivacaine on postoperative epidural fentanyl analgesia and thrombelastography.

We performed a prospective, randomized, double-blind study to determine the effect of bupivacaine on postoperative epidural fentanyl analgesia and thrombelastography in 120 patients who underwent extensive gastrointestinal or genitourinary surgery. The patients were randomized into four groups, 30 patients per group: Group I = epidural fentanyl (EF), 10 micrograms/mL in saline; Group II = EF with 0.1% bupivacaine; Group III = EF with 0.15% bupivacaine; and Group IV = EF with 0.2% bupivacaine. Pain relief was evaluated by a visual analog scale (VAS), both at rest and during coughing, and by a visual rating scale (VRS). The VAS, VRS, degree of sedation, and side effects (nausea, vomiting, and pruritus) were evaluated every 2 h from 8:00 AM to 6:00 PM, for 24 h after surgery. Forced vital capacities (FVCs) were determined before surgery and at 24 h after surgery. Blood was withdrawn for thrombelastography (TEG) measurements preoperatively, in the recovery room (PARR), and 24 h postoperatively. The VAS, VRS, sedation scores, changes in postoperative FVCs, and the incidence of side effects were not statistically different among the four groups. The 24-h total volumes of infusion in the four groups (146 +/- 40 mL, 140 +/- 38 mL, 142 +/- 40 mL, 124 +/- 21 mL, respectively) were not statistically different from each other. There were no significant differences in the TEG values [reaction time (R), coagulation time (K), angle (alpha), and maximum amplitude (mA)] among the four groups at anytime nor was there any difference between the baseline, PARR, and 24-h TEG values within any group.(ABSTRACT TRUNCATED AT 250 WORDS)

Somatosensory evoked potential quantification of ulnar nerve blockade.

We investigated the appropriateness of the somatosensory evoked potentials (SSEPs) as an objective monitor of sensory blockade of the ulnar nerve by comparing the effects of saline and lidocaine infiltration of the ulnar nerve at the elbow, with and without epinephrine. The four treatments were administered in random order to each of eight volunteers who were asked to assess the intensity of sensory blockade on a 10-cm visual analogue scale (SVAS). Concomitantly, ulnar nerve SSEPs were recorded at the Erb's point, over the posterior spine at or rostral to C-7, and over the sensory cortex. All 16 of the saline and saline with epinephrine infiltrations resulted in SVAS scores of 1 or less. In contrast, all the lidocaine and lidocaine with epinephrine injections were associated with SVAS scores in excess of 8. With lidocaine this lasted 83 +/- 22 min, and the duration of lidocaine with epinephrine was 248 +/- 82 min. SSEP responses were considered abnormal when there were 15 min or more of a decrease in amplitude by 50% or more and an increase in latency by 15% or more. After plain lidocaine injection, all the amplitude measurements showed depression over 50%, with the exception of cortical measurements in one subject. Similarly, there were increased latencies at Erb's point and C-7 with lidocaine blocks. In contrast, change in cortical latency was seldom seen. Variable selection by multiple linear regression analysis of the six SSEP measurements gave a statistical model that sensory block duration (SVAS greater than or equal to 8) could be specified by the duration of the reduced C-7 amplitude (r = 0.96).(ABSTRACT TRUNCATED AT 250 WORDS)

Onset, intensity of blockade and somatosensory evoked potential changes of the lumbosacral dermatomes after epidural anesthesia with alkalinized lidocaine.

The onset and intensity of blockade of the lumbosacral dermatomes after epidural anesthesia with alkalinized lidocaine were investigated in a randomized, double-blind study in 26 patients. Control subjects (n = 13) received 20 mL of 1.37% lidocaine (1.5% lidocaine plus 1 mL saline per 10 mL lidocaine) with added 1:200,000 epinephrine; the solution pH was 6.20 +/- 0.08. Patients in the alkalinized lidocaine group (n = 13) were given 20 mL of 1.37% lidocaine plus added bicarbonate (1 mL sodium bicarbonate per 10 mL 1.5% lidocaine) and 1:200,000 epinephrine; the solution pH was 7.18 +/- 0.10. Posterior tibial nerve (PTN) somatosensory evoked potentials (SSEPs) and L5 and S1 dermatomal SSEPs of both lower extremities were done before and after the epidural. Alkalinization of lidocaine resulted in a significantly shorter time to block the L2, L4, L5, and S1 dermatomes. Motor blockade was significantly more profound in the alkalinized lidocaine group. Thirteen of 78 PTN and L5 and S1 dermatomal SSEPs were abolished in the alkalinized lidocaine group compared to 4 of 78 SSEPs in the nonalkalinized group. Alkalinization of lidocaine is recommended to shorten the time to block the L5-S1 dermatomes when epidural anesthesia is planned for lower extremity surgery.

Developmental neurophysiology of mammalian peripheral nerves and age-related differential sensitivity to local anaesthetic.

Using an in vitro nerve preparation, we have studied the relative electrophysiological properties of myelinated and unmyelinated nerve fibres in the vagus nerve of 1-, 9- and 36-month-old rabbits and their sensitivity to local anaesthetic. The baseline (values before infusion of local anaesthetic) mean amplitude and conduction velocity (CV) of the compound action potential (APc) were recorded and the nerve was exposed to a range of concentrations (0.5-4.0 mmol litre-1) of lignocaine for periods sufficient to attain equilibrium block. There was an increase in the amplitude of the A fibre elevation from the 1-month to the 9- and 36-month-old rabbits. The CV of the A and B fibres increased significantly with age, while the CV of the C fibres did not change. The ED50 values of lignocaine for reduction of the A fibre elevation in the 1-, 9- and 36-month-old rabbits were 0.66, 0.94 and 0.85 mmol litre-1, respectively. The respective values for the B fibres were 0.74, 1.21 and 0.82 mmol litre-1, while those of the C fibres were 1.50, 2.44 and 2.07 mmol litre-1. In general, nerves from young and old rabbits were more sensitive to local anaesthetic-induced conduction blockade, suggesting that smaller doses of local anaesthetic are required clinically for anaesthesia in paediatric and older age groups.

The effect of polyethylene glycol on mammalian nerve impulses.

Polyethylene glycol (PEG) is a polymeric compound used as a vehicle for depot steroid preparations such as methylprednisolone acetate and triamcinolone diacetate injected into the epidural or intrathecal space to relieve low back pain. There have been reports of neurodysfunction associated with these injections, and it has been postulated that the PEG vehicle is the offending agent. Studies supporting such a possibility have, however, relied upon concentrations of PEG higher than those used clinically (3%) or have used PEG in combination with other drugs. Using an in vitro rabbit sheathed-nerve preparation, we investigated the effects of a 1-hr exposure to different concentrations (3-40%) of PEG in Liley solution on the transmission of impulses of the A, B, and C nerve fibers. The 3% and 10% PEG had no effect on mean amplitudes of the compound action potentials (CAPs) nor did they significantly decrease conduction velocity. Twenty percent PEG slightly depressed and 30% markedly decreased CAPs. Both 20% and 30% PEG significantly slowed the conduction velocities of A, B, and C nerve fibers. Forty percent PEG abolished CAPs. With washout CAPs recovered to at least 80% of their baseline levels, and conduction velocities returned toward baseline levels. The pH of the Liley solution decreased with an increasing concentration of PEG, from 7.4 in the control Liley solution to 6.45 in the solution of 40% PEG.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation between evoked motor response of the sciatic nerve and sensory blockade.

BACKGROUND: Incomplete sensory blockade of the foot after sciatic nerve block in the popliteal fossa may be related to the motor response that was elicited when the block was performed. We investigated the appropriate motor response when a nerve stimulator is used in sciatic nerve block at the popliteal fossa. METHODS: Six volunteers classified as American Society of Anesthesiologists' physical status I underwent 24 sciatic nerve blocks. Each volunteer had four sciatic nerve blocks. During each block, the needle was placed to evoke one of the following motor responses of the foot: eversion, inversion, plantar flexion, or dorsiflexion. Forty milliliters 1.5% lidocaine was injected after the motor response was elicited at < 1 mA intensity. Sensory blockade of the areas of the foot innervated by the posterior tibial, deep peroneal, superficial peroneal, and sural nerves was checked in a blinded manner. Motor blockade was graded on a three-point scale. The width of the sciatic nerve and the orientation of the tibial and common peroneal nerves were also examined in 10 cadavers. RESULTS: A significantly greater number of posterior tibial, deep peroneal, superficial peroneal, and sural nerves were blocked when inversion or dorsiflexion was seen before injection than after eversion or plantar flexion (P < 0.05). Motor blockade of the foot was significantly greater after inversion. Anatomically, the tibial and common peroneal nerves may be separate from each other throughout their course. The sciatic nerve ranged from 0.9-1.5 cm in width and was divided into the tibial and common peroneal nerves at 8 +/- 3 (range, 4-13) cm above the popliteal crease. CONCLUSIONS: Inversion is the motor response that best predicts complete sensory blockade of the foot. Incomplete blockade of the sciatic nerve may be a result of the size of the sciatic nerve, to separate fascial coverings of the tibial and common peroneal nerves, or to blockade of either the tibial or common peroneal nerves after branching from the sciatic nerve.

A randomized double-blind comparison of epidural fentanyl infusion versus patient-controlled analgesia with morphine for postthoracotomy pain.

The authors conducted a prospective, randomized, double-blind comparison of an epidural fentanyl infusion versus patient-controlled analgesia (PCA) with morphine in the management of postthoracotomy pain. Thirty-six patients were randomized into one of two groups. The epidural group received an epidural fentanyl infusion, 10 micrograms/mL, and saline through their PCA machine. The PCA group received an epidural saline infusion and morphine, 1.0 mg/mL, through their PCA device. The infusions were escalated according to a study protocol when pain relief was deemed inadequate by the patients. Pain relief was evaluated by a visual analog pain scale (VAS), both at rest and during coughing, and by verbal rating scores (VRS) of pain relief. Degree of sedation and the frequency of nausea, vomiting, and pruritus were also noted. The VAS, VRS, degree of sedation, and side effects were evaluated every 2 h from 7 AM to 7 PM, for 72 h after surgery. Forced vital capacities were determined before surgery and at 24, 48, and 72 h after surgery. The VAS were significantly lower (P = 0.001), and the Total Pain Relief scores higher (P < 0.02) in the epidural group, signifying better analgesia. There were no differences in postoperative forced vital capacity between the two groups. More patients in the PCA group had greater degrees of sedation on postoperative day 1 (P = 0.005), whereas pruritus was more frequent (P < 0.02) in the epidural group. We conclude that an epidural fentanyl infusion is superior to that of PCA with morphine in the management of pain after thoracotomy.

Changes in venous blood lactate, venous blood gases, and somatosensory evoked potentials after tourniquet application.

The effects of inflation of a 7-cm tourniquet applied to the upper arm of eight volunteers on venous lactate, venous blood gases, and ulnar nerve somatosensory evoked potentials (SSEPs) were investigated. The inflation pressure was 100 mmHg over the systolic pressure. Venous blood samples for lactate and blood gas determinations were withdrawn before tourniquet inflation; immediately and at 2, 5, 10, 15 min after tourniquet deflation; and additionally at 30, 45, and 60 min after deflation in the last four volunteers. SSEP stimulating surface electrodes were placed over the ulnar nerve at the wrist. Recording electrodes were placed over the ipsilateral ulnar groove of the elbow, Erb's point, and on the contralateral cortex. Averaged responses were acquired before inflation of the tourniquet, every 5-10 min during tourniquet inflation, and every 5-10 min for 45-60 min after tourniquet deflation. The tourniquet was inflated for 36 +/- 11 min. After deflation of the tourniquet, postdeflation pain and paresthesias were felt by five volunteers; these occurred at 30-120 s after deflation and lasted for 75-120 s. The postdeflation pains were characterized as burning, cramping, paresthesias, buzzing, or severe expansion of the hand. The venous blood lactate levels were significantly elevated for 10 min, and the time course of its change did not correlate with reperfusion pain. The PO2 and O2Hb saturation in venous blood were significantly elevated for 10-15 min after deflation. The elevated lactate and PO2 levels in the presence of a restored blood flow probably result from continued anaerobic muscle metabolism secondary to capillary closure from the tourniquet-induced ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)