The effect of clonidine pretreatment on epidural resiniferatoxin in a neuropathic pain rat model.

Resiniferatoxin (RTX) is an ultrapotent synthetic TRPV1 (transient receptor potential vanilloid subtype 1) agonist with significant initial transient hyperalgesia followed by a prolonged analgesic effect in response to thermal stimulus. Using a rat model of neuropathic pain, we evaluated the effect of pretreatment with clonidine-which has been shown to relieve intradermal capsaicin-induced hyperalgesia-on the initial hyperalgesic response and the thermal analgesic property of RTX. Thirty-six male rats were divided into 6 treatment groups (n=6 each):RTX 500 ng, RTX 1 µg, clonidine 20 µg (Cl), Cl＋RTX 500 ng, Cl＋RTX 1 µg, or normal saline 20 µL (control). We evaluated the short-term (180 min) and long-term (20 days) analgesic effects of RTX after thermal stimulation and mechanical stimulation. RTX had significant initial transient hyperalgesia followed by a prolonged analgesic effect in response to the thermal stimulus, but the RTX 500 ng and RTX 1 µg groups showed no initial short-term thermal hyperalgesic responses when pretreated with clonidine. The Cl＋RTX 1 µg rats' behavior scores indicated that they were more calm and comfortable compared to the RTX 1 µg rats. Even though we cannot precisely confirm that pretreatment with clonidine potentiates or adds to the analgesic effect of RTX, clonidine pretreatment with epidural RTX eliminated the initial RTX-associated hyperalgesic response and systemic toxicity in this neuropathic pain rat model.

Pain relief scale is more highly correlated with numerical rating scale than with visual analogue scale in chronic pain patients.

The pain relief scale (PRS) is a method that measures the magnitude of change in pain intensity after treatment. The present study aimed to evaluate the correlation between PRS and changes in pain determined by the visual analogue scale (VAS) and numerical rating scale (NRS), to confirm the evidence supporting the use of PRS. Sixty patients with chronic spinal pain that had a VAS and NRS recorded during an initial examination were enrolled in the study. One week later, the patients received an epidural nerve block, then VAS, NRS, and PRS assessments were performed. Differences between VAS and NRS were compared to the PRS and scatter plots and correlation coefficient were generated. The differences and magnitude of decrease in the VAS and NRS raw data were converted to percentile values, and compared to the PRS. Both VAS and NRS values exhibited strong correlations (> 0.8) with PRS. Further, the differences between the VAS-PRS R (0.859) and NRS-PRS R (0.915) were statistically significant, (P = 0.0259). Compared to PRS, the VAS and NRS percentile scores exhibited higher correlation coefficients than scores based on the raw data differences. Furthermore, even when converted to a percentile, the NRS%-PRS R (0.968) was higher than the VAS%-PRS R (0.904), P = 0.0001. The results indicated that using the PRS together with NRS in pain assessment increased the objectivity of the assessment compared to using only VAS or NRS, and may have offset the limitations of VAS or NRS alone.

Comparison of emergence agitation between sevoflurane/nitrous oxide administration and sevoflurane administration alone in children undergoing adenotonsillectomy with preemptive ketorolac.

BACKGROUND: Sevoflurane anesthesia commonly causes emergence agitation (EA) in children. One previous study has reported that the use of nitrous oxide (N2O) during the washout of sevoflurane may reduce EA by decreasing the residual sevoflurane concentration, while many animal studies suggest that N2O poses a potential risk to children. The present study was designed to compare EA in children assigned to receive sevoflurane with N2O (group N) or sevoflurane alone (group S). METHODS: We enrolled 80 children aged 3-10 years. Anesthesia was induced with 5 mg/kg thiopental sodium, 0.6 mg/kg rocuronium and 0.5 mg/kg ketorolac, and was maintained with 50% N2O and sevoflurane in group N or with sevoflurane alone in group S. The sevoflurane concentration was adjusted with a bispectral index (BIS) of 40-60. After completion of the surgery, N2O and sevoflurane were simultaneously discontinued and replaced with oxygen (O2) at 6 L/min. End-tidal sevoflurane concentration (Et Sevo) (%), BIS at the end of surgery, Et Sevo at recovery of self-respiration and emergence profiles were recorded. EA occurrence, pain score and rescue fentanyl consumption were assessed in the postanesthesia care unit. RESULTS: Et Sevo was significantly lower in group N (1.9%) than in group S (2.3%) at the end of surgery. However, there were no differences in Et Sevo at recovery of self-respiration, emergence times, the incidence of EA, pain score or dose of rescue fentanyl between the groups. CONCLUSIONS: In children undergoing adenotonsillectomy with preemptive ketorolac, anesthetic maintenance using sevoflurane alone does not affect the incidence of EA or emergence profiles compared to anesthetic maintenance using sevoflurane with N2O.

The inhibitory effects of bupivacaine, levobupivacaine, and ropivacaine on K2P (two-pore domain potassium) channel TREK-1.

PURPOSE: Bupivacaine, levobupivacaine, and ropivacaine are amide local anesthetics. Levobupivacaine and ropivacaine are stereoisomers of bupivacaine and were developed to circumvent the bupivacaine's severe toxicity. The recently characterized background potassium channel, K(2P) TREK-1, is a well-known target for various local anesthetics. The purpose of study is to investigate the differences in inhibitory potency and stereoselectivity among bupivacaine, levobupivacaine, and ropivacaine on K(2P) TREK-1 channels overexpressed in COS-7 cells. METHODS: We investigated the effects of bupivacaine, levobupivacaine, and ropivacaine (10, 50, 100, 200, and 400 µM) on TREK-1 channels expressed in COS-7 cells by using the whole cell patch clamp technique with a voltage ramp protocol ranging from -100 to 100 mV for 200 ms from a holding potential of -70 mV. RESULTS: Bupivacaine, levobupivacaine, and ropivacaine showed reversible inhibition of TREK-1 channels in a concentration-dependent manner. The half-maximal inhibitory concentrations (IC(50)) of bupivacaine, levobupivacaine, and ropivacaine were 95.4 ± 14.6, 126.1 ± 24.5, and 402.7 ± 31.8 µM, respectively. IC(50) values indicated a rank order of potency (bupivacaine > levobupivacaine > ropivacaine) with stereoselectivity. Hill coefficients were 0.84, 0.93, and 0.89 for bupivacaine, levobupivacaine, and ropivacaine, respectively. CONCLUSION: Inhibitory effects on TREK-1 channels by bupivacaine, levobupivacaine, and ropivacaine demonstrated stereoselectivity: bupivacaine was more potent than levobupivacaine and ropivacaine. Inhibition of TREK-1 channels and consecutive depolarization of the cell membrane by bupivacaine, levobupivacaine, and ropivacaine may contribute to the blockade of neuronal conduction and side effects.

Reducing the pain of microemulsion propofol injections: a double-blind, randomized study of three methods of tourniquet and lidocaine.

BACKGROUND: Although the new formulation of lipid-free microemulsion propofol (MP) has some advantages over the lipid emulsion, it reportedly produces more injection pain than lipid-based propofol. Intravenous lidocaine with application of a rubber tourniquet before administration of propofol is considered to be the best method for reducing injection pain; however, this technique is not perfect. OBJECTIVE: The goal of this study was to evaluate the effect of different methods of tourniquet application and lidocaine administration on MP injection pain. METHODS: This single-center, randomized controlled clinical trial was conducted in 140 patients aged 18 to 65 years. Patients were randomly divided into 4 groups (n = 35 each). Group A received MP (2 mg/kg) after lidocaine (0.6 mg/kg) with a tourniquet with arm down (venous engorgement); group B received MP after lidocaine with a tourniquet with arm up (venous gravity drainage); group C received MP with a tourniquet with arm down; and group D (control group) received MP only (with no tourniquet). In groups A and C, the tourniquet was released after MP; in group B, the tourniquet was released before MP. Injection pain was evaluated by using a verbal pain score (VPS). The bispectral index, the time from the beginning of drug injection to the loss of eyelash reflex, and time to the lowest bispectral index value were recorded. RESULTS: Group A showed significantly less incidence of pain than the control group when MP was injected. The mean VPS was significantly lower in groups A, B, and C than in group D (the control group). The VPS of group A was significantly lower than that in group B. Other observed values were not significantly different. CONCLUSIONS: We concluded that intravenous retention of lidocaine with the application of a rubber tourniquet under venous engorgement of the arm reduces the incidence and intensity of MP injection pain. CLINICAL TRIAL REGISTRY: UMIN000010725.

Right upper lobe tracheal bronchus: anesthetic challenge in one-lung ventilated patients -A report of three cases-.

Tracheal bronchus (TB) is an aberrant, accessary or ectopic bronchus arising almost exclusively from the right side of the tracheal wall above the carina. In our center, 673 bronchoscopic examinations were performed from 2009 to 2011 in patients undergoing one lung ventilation (OLV) and 3 TB were found. The incidence of a TB at bronchoscopy was 0.45% in our research, which is consistent with the reported incidence range from 0.1-5%. The clinician should consider the possibility of anomalous right upper lobe bronchus and perform bronchoscopy prior to the right bronchial blocker insertion, when left-sided OLV using bronchial blocker is planned. Also, for the patient with TB, a double lumen tube insertion is recommended than a blocker insertion to achieve OLV completely.

Comparison of bispectral index (BIS) and entropy in patients with cerebral palsy during sevoflurane induction.

BACKGROUND: Demand of anesthesia for patients with cerebral palsy is more increasing. But there is still lacking in clinical research regarding how BIS and entropy reflect well on sedative and hypnotic state in patients with cerebral palsy. METHODS: Fifteen patients with cerebral palsy (Group CP) and fifteen patients without cerebral palsy (Group NL) scheduled for elective orthopedic surgery were included in the study. Induction of anesthesia was done by having the patient inhale 1 vol% sevoflurane and 100% oxygen using a total fresh gas flow of 8 L/min. Simultaneously BIS, state entropy (SE), response entropy (RE), end-tidal sevoflurane concentration were recorded every 15 seconds till there was no self respiration. When end-tidal sevoflurane concentration had not risen any more for 30 seconds, we increased inhaled sevoflurane concentration in 1 vol% increments. End point of recording was when self respiration was lost or the time sevoflurane concentration reached 8 vol%. RESULTS: No significant differences in RE, SE, BIS at baseline and end point were found between the two groups. No significant difference in the time reach end point was found between the two groups. BIS, SE and RE correlated with end-tidal sevoflurane concentration in the two groups. CONCLUSIONS: The authors found no significant difference in the entropy values between patients with CP and normal patients. Also, the entropy values could be interpreted like BIS in patients with CP. And BIS showed a stronger correlation with end tidal sevoflurane concentrations than entropy.