Caudal Epidural Block: An Updated Review of Anatomy and Techniques.

Caudal epidural block is a commonly used technique for surgical anesthesia in children and chronic pain management in adults. It is performed by inserting a needle through the sacral hiatus to gain entrance into the sacral epidural space. Using conventional blind technique, the failure rate of caudal epidural block in adults is high even in experienced hands. This high failure rate could be attributed to anatomic variations that make locating sacral hiatus difficult. With the advent of fluoroscopy and ultrasound in guiding needle placement, the success rate of caudal epidural block has been markedly improved. Although fluoroscopy is still considered the gold standard when performing caudal epidural injection, ultrasonography has been demonstrated to be highly effective in accurately guiding the needle entering the caudal epidural space and produce comparative treatment outcome as fluoroscopy. Except intravascular and intrathecal injection, ultrasonography could be as effective as fluoroscopy in preventing complications during caudal epidural injection. The relevant anatomy and techniques in performing the caudal epidural block will be briefly reviewed in this article.

The association between frequent alcohol drinking and opioid consumption after abdominal surgery: A retrospective analysis.

AIMS: It is perceived that patients with a history of frequent alcohol consumption require more opioids for postoperative pain control and experience less postoperative nausea and vomiting than patients without such a history. However, there is scarce evidence supporting this notion. The aim of this study was to assess association between frequent alcohol consumption and opioid requirement for postoperative pain control and occurrence of postoperative nausea and vomiting. METHODS: The medical records for 4143 patients using intravenous patient-control analgesia with opioids after abdominal surgery between January 2010 and September 2013 were obtained, and associations were sought between the cumulative opioid consumption (in intravenous morphine equivalence) per body weight (mg/kg) in the first 2 days after abdominal operation and several demographic and clinical variables by multiple regression analysis. The association between the occurrence of postoperative nausea and vomiting and several demographic and clinical variables was also sought by multiple logistic regression analysis. RESULTS: Frequent alcohol drinking, among other previously reported factors, was associated with increased opioid consumption for postoperative pain control (p < 0.001). The estimate effect of frequent alcohol drinking was 0.117 mg/kg. Frequent alcohol drinking was also associated with decreased risks of postoperative nausea (odds ratio = 0.59, p = 0.003) and vomiting (odds ratio = 0.49, p = 0.026). CONCLUSIONS: Frequent alcohol drinking was associated with increased opioid consumption for postoperative pain control and decreased risks of postoperative nausea and vomiting after abdominal surgery.

Effects of Interscalene Nerve Block for Postoperative Pain Management in Patients after Shoulder Surgery.

OBJECTIVES: Shoulder surgery can produce severe postoperative pain and movement limitations. Evidence has shown that regional nerve block is an effective management for postoperative shoulder pain. The purpose of this study was to investigate the postoperative analgesic effect of intravenous patient-controlled analgesia (PCA) combined with interscalene nerve block in comparison to PCA alone after shoulder surgery. METHODS: In this study, 103 patients receiving PCA combined with interscalene nerve block (PCAIB) and 48 patients receiving PCA alone after shoulder surgery were included. Patients' characteristics, preoperative shoulder score and range of motion, surgical and anesthetic condition in addition to visual analog scale (VAS) pain score, postoperative PCA consumption, and adverse outcomes were evaluated. RESULTS: The results showed that PCA combined with interscalene nerve block (PCAIB) group required less volume of analgesics than PCA alone group in 24 hours (57.76 ± 23.29 mL versus 87.29 ± 33.73 mL, p < 0.001) and 48 hours (114.86 ± 40.97 mL versus 183.63 ± 44.83 mL, p < 0.001) postoperatively. The incidence of dizziness in PCAIB group was significantly lower than PCA group (resp., 1.9% and 14.6%, p = 0.005). VAS, nausea, and vomiting were less in group PCAIB, but in the absence of significant statistical correlation. CONCLUSION: Interscalene nerve block is effective postoperatively in reducing the demand for PCA analgesics and decreasing opioids-induced adverse events following shoulder surgery.

A long noncoding RNA contributes to neuropathic pain by silencing Kcna2 in primary afferent neurons.

Neuropathic pain is a refractory disease characterized by maladaptive changes in gene transcription and translation in the sensory pathway. Long noncoding RNAs (lncRNAs) are emerging as new players in gene regulation, but how lncRNAs operate in the development of neuropathic pain is unclear. Here we identify a conserved lncRNA, named Kcna2 antisense RNA, for a voltage-dependent potassium channel mRNA, Kcna2, in first-order sensory neurons of rat dorsal root ganglion (DRG). Peripheral nerve injury increased Kcna2 antisense RNA expression in injured DRG through activation of myeloid zinc finger protein 1, a transcription factor that binds to the Kcna2 antisense RNA gene promoter. Mimicking this increase downregulated Kcna2, reduced total voltage-gated potassium current, increased excitability in DRG neurons and produced neuropathic pain symptoms. Blocking this increase reversed nerve injury-induced downregulation of DRG Kcna2 and attenuated development and maintenance of neuropathic pain. These findings suggest endogenous Kcna2 antisense RNA as a therapeutic target for the treatment of neuropathic pain.

Absence of µ opioid receptor mRNA expression in astrocytes and microglia of rat spinal cord.

Cumulating evidence has demonstrated that µ opioid receptor (MOR) agonists promote spinal glial activation, lead to synthesis and release of proinflammatory cytokines and chemokines, and contribute to opioid-induced hyperalgesia and development of opioid tolerance and dependence. However, whether these MOR agonists directly or indirectly act on spinal cord astrocytes and microglial cells in vivo is unclear. In the present study, by combining the techniques of in-situ hybridization of MOR mRNA with immunohistochemistry of glial fibrillary acidic protein (GFAP; an astrocyte marker) and Iba1 (a microglial marker), we examined expression and distribution of GFAP, Iba1, and MOR mRNA in the spinal cord of rats under chronic morphine tolerance conditions. Intrathecal injections of morphine twice daily for 7 days reduced morphine analgesic effect and increased both GFAP and Iba1 immunostaining densities in the spinal cord. Surprisingly, neither GFAP nor Iba1 colocalized with MOR mRNA in spinal cord cells. Our findings indicate that MOR expression is absent from spinal cord astrocytes and microglia, suggesting that these cell types are indirectly activated by MOR agonists under chronic opioid tolerance conditions.

Spinal cord NMDA receptor-mediated activation of mammalian target of rapamycin is required for the development and maintenance of bone cancer-induced pain hypersensitivities in rats.

UNLABELLED: Mammalian target of rapamycin (mTOR) controls mRNA translation and is critical for neuronal plasticity. However, how it participates in central sensitization underlying chronic pain is unclear. Here, we show that NMDA receptors are required for the functional role of spinal cord mTOR in bone cancer pain induced by injecting prostate cancer cells (PCCs) into the tibia. Intrathecal rapamycin, a specific mTOR inhibitor, dose dependently attenuated the development and maintenance of PCC-induced mechanical allodynia and thermal hyperalgesia. Rapamycin alone did not affect locomotor activity and acute responses to thermal or mechanical stimuli. Phosphorylation of mTOR and p70S6K (a downstream effector) was increased time dependently in L(4-5) dorsal horn and transiently in L(4-5) dorsal root ganglions on the ipsilateral side after PCC injection, although total expression of mTOR or p70S6K was not changed in these regions. The increases in dorsal horn were abolished by intrathecal infusion of DL-AP5, an NMDA receptor antagonist. Moreover, NMDA receptor subunit NR1 colocalized with mTOR and p70S6K in dorsal horn neurons. These findings suggest that PCC-induced dorsal horn activation of the mTOR pathway participates in NMDA receptor-triggered dorsal central sensitization under cancer pain conditions. PERSPECTIVE: The present study shows that inhibition of spinal mTOR blocks cancer-related pain without affecting acute pain and locomotor function. Given that mTOR inhibitors are FDA-approved drugs, mTOR in spinal cord may represent a potential new target for preventing and/or treating cancer-related pain.

Inflammation alters trafficking of extrasynaptic AMPA receptors in tonically firing lamina II neurons of the rat spinal dorsal horn.

Peripheral inflammation alters AMPA receptor (AMPAR) subunit trafficking and increases AMPAR Ca(2+) permeability at synapses of spinal dorsal horn neurons. However, it is unclear whether AMPAR trafficking at extrasynaptic sites of these neurons also changes under persistent inflammatory pain conditions. Using patch-clamp recording combined with Ca(2+) imaging and cobalt staining, we found that, under normal conditions, an extrasynaptic pool of AMPARs in rat substantia gelatinosa (SG) neurons of spinal dorsal horn predominantly consists of GluR2-containing Ca(2+)-impermeable receptors. Maintenance of complete Freund's adjuvant (CFA)-induced inflammation was associated with a marked enhancement of AMPA-induced currents and [Ca(2+)](i) transients in SG neurons, while, as we previously showed, the amplitude of synaptically evoked AMPAR-mediated currents was not changed 24 h after CFA. These findings indicate that extrasynaptic AMPARs are upregulated and their Ca(2+) permeability increases dramatically. This increase occurred in SG neurons characterized by intrinsic tonic firing properties, but not in those exhibited strong adaptation. This increase was also accompanied by an inward rectification of AMPA-induced currents and enhancement of sensitivity to a highly selective Ca(2+)-permeable AMPAR blocker, IEM-1460. Electron microcopy and biochemical assays additionally showed an increase in the amount of GluR1 at extrasynaptic membranes in dorsal horn neurons 24h post-CFA. Taken together, our findings indicate that CFA-induced inflammation increases functional expression and proportion of extrasynaptic GluR1-containing Ca(2+)-permeable AMPARs in tonically firing excitatory dorsal horn neurons, suggesting that the altered extrasynaptic AMPAR trafficking might participate in the maintenance of persistent inflammatory pain.

Difficult oral endotracheal intubation in an acromegalic patient receiving transsphenoidal surgery--a case report.

Patients suffering from acromegaly are associated with increased risks of difficult airway management. We report a case of acromegaly scheduled for transsphenoidal resection of pituitary adenoma under general anesthesia in whom all possible means failed us in the insertion of the endotracheal tube (ET) through the mouth, a procedure essential for transsphenoidal surgery. The operation was called off and for securing his compromised airway a nasal ET was placed under fiberoptic bronchoscopy. Five days later, awake oral fiberoptic intubation was successful under topical anesthesia. We suggest that oral endotracheal intubation performed awake under topical anesthesia with the aid of a fiberoptic bronchoscope is a choice approach in acromegalic patients with predicated difficult airway who are to receive surgery.

Desflurane used in a patient with congenital insensitivity to pain with anhidrosis during septic shock.

Congenital insensitivity to pain with anhidrosis (CIPA) is a rare autonomic recessive disorder characterized by congenital analgesia, absence of sweating and mental retardation. Because of these abnormalities, the anesthetic managements in patients with CIPA deserve special attention. Here we report a 22-year-old man with CIPA receiving left above-knee amputation due to severe lower extremity infection. General anesthesia was maintained with desflurane, an intervention that has never been reported, and the whole course of operation was uneventful. This is also the first reported case of CIPA in Taiwan.

Unusual cause of esophageal perforation during intraoperative transesophageal echocardiography monitoring for cardiac surgery--a case report.

Although esophageal perforation after transesophageal echocardiographic (TEE) examination is rare yet the occurrence of this life-threatening complication is increasing. We report an unusual esophageal perforation occurring 4 days after coronary artery bypass graft surgery and Bentall's procedure. The perforation was due to inadvertent injury of the esophagus that was deformed and distorted by a large calcified lymph node in the mediastinum during intraoperative TEE instrumentation. We suggest that careful preoperative radiological examination of the mediastinum should be done to recognize the anatomical pathology in patient whose routine chest X-ray has disclosed a large calcified lymph node in the mediastinum, if he happens to undergo TEE, so as to avoid disastrous esophageal perforation.

General anesthesia for patient with homocystinuria--a case report.

Homocystinuria is an autosomal recessive disease with multiple systemic disorders. Here we report a 15-year-old lad suffering from homocystinuria who required an ocular surgery including lentectomy and implant of plastic lens, OS and anterior retinal cryotherapy, OD under general anesthesia because of lens subluxation and lattice degeneration. It is the elective ocular procedure most commonly performed for homocystinuric children. Proper precautions should be taken during anesthetic management since this condition inspires some particular anesthetic complications that could be prevented by careful consideration and understanding of its pathophysiology. Providentially our patient stood the operation well and was discharged without subsequent thromboembolism or other complication as an aftermath.

Lateral medullary syndrome after prone position for general surgery.

IMPLICATIONS: We describe postoperative lateral medullary syndrome with myoclonic spasm. Improper head rotation during positioning in the anesthetized patient might obstruct the flow of the vertebral artery at the neck and result in diminished perfusion of the associated regions in patients with a history of cervical spinal trauma.