Ping-Wing Lui

Involvement of coerulospinal noradrenergic pathway in fentanyl-induced muscular rigidity in rats

Unilateral, site-specific microinjection of fentanyl (2.5 micrograms/50 nl) into the locus coeruleus (LC) in Sprague-Dawley rats anesthetized with ketamine evoked a significant increase in the electromyographic activity recorded from both caudal lateral extensor and gastrocnemius muscles. This correlate of opiate-induced muscular rigidity was appreciably antagonized by a pretreatment with the specific alpha 1-adrenoceptor blocker, prazosin (250 micrograms/kg, i.v.). On the other hand, an equimolar dose (0.65 mumol/kg) of the specific alpha 2-adrenoceptor blocker, yohimbine (0.23 mg/kg, i.v.) failed to prevent the occurrence of fentanyl-induced EMG activation. We suggest that the coerulospinal noradrenergic pathway may be directly involved in the elicitation of muscular rigidity by fentanyl, possibly via alpha 1-adrenoceptors in the spinal cord.

Involvement of locus coeruleus and noradrenergic neurotransmission in fentanyl-induced muscular rigidity in the rat

Whereas muscular rigidity is a well-known side effect that is associated with high-dose fentanyl anesthesia, a paucity of information exists with regard to its underlying mechanism(s). We investigated in this study the possible engagement of locus coeruleus of the pons in this phenomenon, using male Sprague-Dawley rats anesthetized with ketamine. Under proper control of respiration, body temperature and end-tidal CO2, intravenous administration of fentanyl (50 or 100 micrograms/kg) consistently promoted an increase in electromyographic activity recorded from the gastrocnemius and abdominal rectus muscles. Such an induced muscular rigidity by the narcotic agent was significantly antagonized or even reduced by prior electrolytic lesions of the locus coeruleus or pretreatment with the alpha-adrenoceptor blocker, prazosin. Microinjection of fentanyl (2.5 micrograms/50 nl) directly into this pontine nucleus, on the other hand, elicited discernible electromyographic excitation. It is speculated that the induction of muscular rigidity by fentanyl may involve the coerulospinal noradrenergic fibers to the spinal motoneurons.

Inhibition of the cyclic adenosine monophosphate pathway attenuates neuropathic pain and reduces phosphorylation of cyclic adenosine monophosphate response element-binding in the spinal cord after partial sciatic nerve ligation in rats

BACKGROUND:Recent reports have identified a role for cyclic adenosine monophosphate (cAMP) transduction in nociceptive processing. Spinal activation of the cAMP induced gene transcription through the activation of protein kinase A and cAMP response element-binding protein (CREB). Intrathecal injection of protein kinase A inhibitor reversed the mechanical hyperalgesia, whereas injection of CREB antisense attenuated tactile allodynia caused by partial sciatic nerve ligation (PSNL) in rats. In the present study, we aimed to assess the effects of spinal cAMP transduction on the nociceptive processing in a chronic neuropathic pain model. METHODS:PSNL was performed in male Sprague-Dawley rats 1 wk after intrathecal catheterization. Nociception to mechanical and thermal stimuli was assessed at the hindpaw 2 h, 3, 7, and 14 days after PSNL. The effects of adenylate cyclase inhibitor, SQ22536 (0.7 &mgr;mol, intrathecal) on these nociceptions were evaluated. Changes in the expression and immunoreactivity of CREB and its phosphorylated proteins (CREB-IR and pCREB-IR) in the dorsal horn of the spinal cord were also measured. RESULTS:The expression of CREB-IR and pCREB-IR proteins was shown to increase for 2 wk after PSNL. The increase in pCREB was partially reversed by the blockade of the cAMP pathway in the early 3 days, with a parallel increase in mechanical and thermal withdrawal thresholds. CONCLUSION:These results revealed the possible contribution of an increase in pCREB to the PSNL-induced tactile allodynia and thermal hyperalgesia. Modulation of the cAMP pathway may be clinically relevant if early intervention can be achieved in patients with chronic neuropathic pain.

Inadvertent knotting of a thoracic epidural catheter.

We report a case of corrosive injury of upper gastrointestinal and respiratory tracts scheduled for feeding jejunostomy under thoracic epidural anesthesia. An epidural catheter was inserted at the T8–T9 intervertebral space and threaded 7 cm beyond the tip of the Tuohy needle in a rostral direction. Resistance was noticed during attempts to inject the local anesthetic. As resistance could not be relieved by changing the position of the patient, kinking of the epidural catheter was suspected. Following informing the patient of the associated risks, the catheter was retrieved successfully by gentle and steady pulling. A tight double‐knot of catheter was found. No neurological sequelae to the procedure were noticed.

Exogenous granulocyte colony-stimulating factor exacerbate pain-related behaviors after peripheral nerve injury

Previous studies have demonstrated that inflammatory cells produce several mediators that can effectively counteract pain. This study was designed to test the hypothesis that exogenous administration of recombinant mouse granulocyte-colony-stimulating factor (rmG-CSF) to enhance the recruitment of inflammatory cells to painful inflamed sites could attenuate pain in a chronic neuropathic pain model in mice. Our results indicate that treatment with rmG-CSF increased several cytokines and opioid peptides content; however, it did not attenuate but exacerbate neuropathic pain. Our study highlights the potent pro-inflammatory potential of G-CSF and suggests they may be targets for therapeutic intervention in chronic neuropathic pain.

Incidence and risk factors of guidewire-induced arrhythmia during internal jugular venous catheterization: Comparison of marked and plain J-wires

STUDY OBJECTIVES To compare the incidence and risk factors of guidewire-induced arrhythmia (GIA) during internal jugular venous catheterization (IJV). DESIGN Prospective study. SETTING Operating rooms at a medical center. PATIENTS 303 ASA physical status I, II, III, and IV patients undergoing elective surgery. INTERVENTIONS All patients were cannulated with the central venous catheters placed via the right internal jugular vein after induction of anesthesia. They were randomly divided into two groups. In one group, we used a marked J-wire and inverted up to, but not beyond 20 cm (Group M, n = 127). In the other group, a plain unmarked J-wire was used and inserted at will (Group UM, n = 176). All IJV catheterizations were performed by residents, and the length of J-wire inserted was then measured. MEASUREMENTS AND MAIN RESULTS Types of arrhythmia [eg, premature atrial contraction (PAC) or premature ventricular contraction (PVC)] were interpreted by attending anesthesiologists on lead II ECG. Patients in Group UM had a significantly greater incidence of GIA than those in Group M (28.4% vs. 3.9%; p < .005). However, in both groups, PAC occurred more frequently than PVC. Factors such as the inserted length of guidewire longer than 20 cm, body height less than 170 cm, and female gender were significantly associated with GIA (p < 0.005). CONCLUSIONS Limiting the length of the guidewire insertion to less than or equal to 20 cm for right IJV catheterization by using a marked J-wire will reduce the incidence of GIA. We recommend the use of a marked J-wire for IJV catheterization.

Spectral analysis of arterial pressure variability during induction of propofol anesthesia

We studied the effect of continuous infusion of propofol on spectral components in systemic arterial pressure (SAP) signals in 35 consenting patients undergoing abdominal surgery.Anesthesia was induced with intravenous bolus administration of propofol (2.0 mg/kg), followed by infusion at either 5 mg centered dot kg-1 centered dot h-1 (Group 1, n = 18) or 10 mg centered dot kg-1 centered dot h-1 (Group 2, n = 17). Tracheal intubation was facilitated by administration of vecuronium (0.1 mg/kg). The SAP signal was subjected to offline spectral analysis to obtain changes in power of the very low frequency (VLF; 0.00-0.08 Hz), low frequency (LF; 0.08-0.15 Hz), high frequency (0.15-0.25 Hz), and very high frequency (VHF; 0.80-1.60 Hz) components. Venous blood for the measurement of plasma concentration of propofol was collected at 5 min before bolus injection of propofol; at 5, 10, and 15 min after infusion of propofol; and immediately after endotracheal intubation. Infusion of propofol significantly decreased the total power of SAP spectrum in both groups, especially the VLF, LF, and VHF components at all intervals except postintubation. Immediately after tracheal intubation, patients in Group 1 showed a significant increase in mean arterial pressure when compared with those in Group 2 (118 +/- 5 mm Hg vs 102 +/- 5 mm Hg, P < 0.05). Similar change was also seen in the VLF component (7.4 +/- 0.7 mm Hg2 vs 4.4 +/- 0.5 mm Hg2, P < 0.05). After tracheal intubation, patients in Group 1 showed 15.7-, 3.3-, and 4.4-fold increase in the VLF, LF, and VHF components, respectively. There were 14.4-, 2.8-, and 2.8-fold increases in the respective components of the SAP signal in Group 2. At all intervals, the spectral components of SAP, however, did not correlate well with the plasma concentration of propofol in either group. These results suggest that spectral analysis of SAP signals may provide an alternative for assessing autonomic activities, such as the sympathetic response, to tracheal intubation during propofol anesthesia. (Anesth Analg 1996;82:914-9)

Modification of tonic-clonic convulsions by atracurium in multiple-monitored electroconvulsive therapy

STUDY OBJECTIVE To determine the effect of two different doses of atracurium on the modification of tonic-clonic convulsions in multiple-monitored electroconvulsive therapy (MMECT). To compare recovery time and adverse reactions of these doses. DESIGN Clinical study. Anesthesiologist was blinded in the evaluation of post-electroconvulsive therapy (ECT) myalgia and other side effects. SETTING University-affiliated veterans general hospital. PATIENTS Two groups of twelve psychiatric inpatients who suffered from major depression or catatonic-type schizophrenia that failed to respond to tricyclic antidepressant therapy. INTERVENTIONS Under single-channel, prefrontal electroencephalographic (EEG) monitoring, patients were given either 0.3 mg/kg or 0.5 mg/kg of atracurium intravenously (IV) after anesthetic induction with methohexital 1 mg/kg i.v. MEASUREMENTS AND MAIN RESULTS Evoked electromyographic responses of the adductor pollicis muscle was obtained by train-of-four stimulation of the ulnar nerve at the wrist every 20 seconds. The first twitch depression (T1) of neuromuscular blockade was maintained within 11% to 25% (atracurium 0.3 mg/kg) or 0% to 10% (atracurium 0.5 mg/kg) of control during the entire session of MMECT. Patients pretreated with atracurium 0.5 mg/kg had significantly fewer ECT-induced moderate and vigorous convulsions when compared with patients receiving atracurium 0.3 mg/kg (16.7% vs. 78.4%, moderate; 0% vs. 8.3%, vigorous). However, patients pretreated with atracurium 0.5 mg/kg took a longer time to attain a T4 ratio of 0.5 than did patients receiving atracurium 0.3 mg/kg (9.2 +/- 0.8 minutes vs. 4.3 +/- 0.4 minutes). There was no significant difference between the two groups with respect to cumulative seizure duration or frequency of bradycardia, sialorrhea, postseizure myalgia, nausea, headache, or confusion. No patient in either group recalled any event concerning electroconvulsive shock. CONCLUSIONS Whereas full neuromuscular blockade by atracurium 0.5 mg/kg i.v. is very effective in the modification of tonic-clonic convulsions induced by ECT, we suggest that a lower dose of atracurium (0.3 mg/kg i.v.) be used if one needs to ascertain the occurrence of ECT-induced seizures as indicated by minimum peripheral muscle activity at the time of EEG recording during MMECT.

Thoracic Epidural Analgesia with Morphine Does Not Prevent Postthoracotomy Pain Syndrome: A Survey of 159 Patients

BACKGROUND This retrospective study sought to determine the incidence of postthoracotomy pain syndrome (PTPS), and whether epidural morphine for the postoperative analgesia could prevent the development of PTPS. METHODS We reviewed the charts of 372 patients who had undergone thoracotomy. The majority underwent general anesthesia (GA) combined with thoracic epidural analgesia (TEA). Of the 372 patients, only 159 (42%) were available for interview. Patients were divided into two groups based on the duration of pain, i.e., pain group (pain > 3 months, n = 65) and pain-free group (pain < 3 months, n = 94). RESULTS Both groups were comparable regarding sex, age, weight, height, smoking, alcohol ingestion, education, marital status, duration of surgery, and the number of patients either receiving GA plus TEA or GA alone. About 41% of the patients experienced PTPS that persisted for 21 +/- 12 mon (follow-up: 28 +/- 12 mon). Most pain was mild or moderate and was usually described as being only a discomfort. Only 6.2% suffered severe pain with shooting, aching, burning or numbness. Patients with PTPS suffered more depression and insomnia. The incidence of PTPS was not different in patients who received GA alone or GA plus TEA (39% vs. 42%). CONCLUSIONS Epidural morphine for postoperative analgesia that continued for 3 days appeared to have no effect in the prevention of PTPS.

Chemical Burn Caused by Providone-iodine Alcohol Solution-A Case Report

Burns associated with chemical disinfectants for skin preparation are rare. Skin irritation and maceration associated with pressure factors may contribute to its occurrence. We report a 24-year-old female with thyroid tumor who was admitted for subtotal thyroidectomy. After anesthetic induction, the patient was placed in the supine position with the trunk elevated to 20 degree. The skin over the anterior neck was sterilized with 10% Povidone-iodine (PI) alcohol solution. After a 3-hour surgery, the patient complained of burning pain over the back at the recovery room. Physical examination revealed a 9 x 11 cm area of skin lesion partially thickened amid on the middle of the back suggestive of chemical burn. After conservative treatment, she was discharged uneventfully 4 days later. Upon follow-up, the wound was seen to heal with minimal scarring within 3 weeks.