Shou-Zen Fan

Effect of combining dexmedetomidine and morphine for intravenous patient-controlled analgesia

BACKGROUND Perioperative use of dexmedetomidine is associated with reduction in postoperative analgesic requirements. This study examined whether dexmedetomidine added to i.v. patient-controlled analgesia (PCA) morphine could improve analgesia while reducing opioid-related side-effects. METHODS In this double-blinded, randomized, controlled study, 100 women undergoing abdominal total hysterectomy were allocated to receive either morphine 1 mg ml(-1) alone (Group M) or morphine 1 mg ml(-1) plus dexmedetomidine 5 microg ml(-1) (Group D) for postoperative i.v. PCA, which was programmed to deliver 1 ml per demand with a 5 min lockout interval and no background infusion. Cumulative PCA requirements, pain intensities, cardiovascular and respiratory variables, and PCA-related adverse events were recorded for 24 h after operation. RESULTS Compared with Group M, patients in Group D required 29% less morphine during the 0-24 h postoperative period and reported significantly lower pain levels from the second postoperative hour onwards and throughout the study. Whereas levels of sedation were similar between the groups at each observational time point, decreases in heart rate and mean blood pressure from presurgery baseline at 1, 2, and 4 h after operation were significantly greater in Group D (by a range of 5-7 beats min(-1) and 10-13%, respectively). The 4-24 h incidence of nausea was significantly lower in Group D (34% vs 56.3%, P<0.05). There was no bradycardia, hypotension, oversedation, or respiratory depression. CONCLUSIONS The addition of dexmedetomidine to i.v. PCA morphine resulted in superior analgesia, significant morphine sparing, less morphine-induced nausea, and was devoid of additional sedation and untoward haemodynamic changes.

Low dose of intrathecal hyperbaric bupivacaine combined with epidural lidocaine for cesarean section--a balance block technique.

The present study was designed to develop a combined spinal/epidural anesthetic technique for cesarean section. We compared the effects of different doses of intrathecal hyperbaric bupivacaine (0.5%) combined with epidural lidocaine (2%). We attempted to interrupt somatosensory pathways with spinal anesthesia but to avoid acute high thoracic sympathetic block. The visceral afferent pathways were to be blocked relatively slowly with epidural lidocaine. Eighty term parturients were randomly divided into four groups. In Group A, 2.5 mg of bupivacaine intrathecally combined with 22.2 +/- 4.6 mL of lidocaine epidurally provided insufficient muscle relaxation. In Group B, 5 mg of bupivacaine with 10.1 +/- 2.0 mL of lidocaine resulted in satisfactory anesthesia with rapid onset and minimum side effects. Anesthesia in Group C (7.5 mg of bupivacaine) and Group D (10 mg of bupivacaine) was mostly due to spinal block. Complications included hypotension, nausea, and dyspnea. The combined spinal/epidural technique, using 5 mg of bupivacaine and with sufficient epidural lidocaine to reach a T4 level, had the advantages of both spinal and epidural anesthesia with few of the complications of either.

Propofol concentration monitoring in plasma or whole blood by gas chromatography and high-performance liquid chromatography.

We compared the measurement of propofol concentrations in plasma or whole blood by high-performance liquid chromatography (HPLC) to that of gas chromatography (GC). Blood samples were collected from patients who had received bolus injection or continuous infusion of propofol. The results showed that the two methods correlated well both in plasma and whole blood samples. However, significant biphasic differences of propofol concentrations between plasma and whole blood specimens were observed in the bolus injection group. Differences were larger in the infusion group. This discrepancy in concentrations resulted from the infusion or clearance of propofol, and the lag of redistribution across blood cell membranes. In conclusion, monitoring of propofol concentrations by the methods of GC and HPLC gives equivalent results. For propofol concentration monitoring, plasma samples are preferred, but immediate centrifugation is needed. (Anesth Analg 1995;81:175-8)

Human heart beat analysis using a modified algorithm of detrended fluctuation analysis based on empirical mode decomposition.

How to quantify the complexity of a physiological signal is a crucial issue for verifying the underlying mechanism of a physiological system. The original algorithm of detrended fluctuation analysis (DFA) quantifies the complexity of signals using the DFA scaling exponent. However, the DFA scaling exponent is suitable only for an integrated time series but not the original signal. Moreover, the method of least squares line is a simple detrending operation. Thus, the analysis results of the original DFA are not sufficient to verify the underlying mechanism of physiological signals. In this study, we apply an innovative timescale-adaptive algorithm of empirical mode decomposition (EMD) as the detrending operation for the modified DFA algorithm. We also propose a two-parameter scale of randomness for DFA to replace the DFA scaling exponent. Finally, we apply this modified algorithm to the database of human heartbeat interval from Physiobank, and it performs well in identifying characteristics of heartbeat interval caused by the effects of aging and of illness.

Adaptive Computation of Multiscale Entropy and Its Application in EEG Signals for Monitoring Depth of Anesthesia During Surgery

Entropy as an estimate of complexity of the electroencephalogram is an effective parameter for monitoring the depth of anesthesia (DOA) during surgery. Multiscale entropy (MSE) is useful to evaluate the complexity of signals over different time scales. However, the limitation of the length of processed signal is a problem due to observing the variation of sample entropy (S E ) on different scales. In this study, the adaptive resampling procedure is employed to replace the process of coarse-graining in MSE. According to the analysis of various signals and practical EEG signals, it is feasible to calculate the S E from the adaptive resampled signals, and it has the highly similar results with the original MSE at small scales. The distribution of the MSE of EEG during the whole surgery based on adaptive resampling process is able to show the detailed variation of S E in small scales and complexity of EEG, which could help anesthesiologists evaluate the status of patients.

Analgesic Effect of Lidocaine Patch 5% in the Treatment of Acute Herpes Zoster: A Double-Blind and Vehicle-Controlled Study

Background and Objectives: Although lidocaine patch 5% has been widely used for postherpetic neuralgia, its analgesic effect on the intense pain associated with acute herpes zoster has not been investigated because of its potential hazard to damaged skin. Methods: Forty‐six patients suffering from moderate to severe pain caused by acute herpes zoster infection (within 4 weeks of onset) were enrolled in a randomized, double‐blind, vehicle‐controlled, parallel study. Lidocaine patch 5% or vehicle patch were applied to the intact portion of the painful skin area without blisters at 12‐hour intervals twice a day for 2 consecutive days. Analgesic efficacy and side effect profiles were assessed before and 48 hours after patch application. Results: We found that both groups of patients experienced significant pain relief during rest and movement. Differences of mean reduction of pain intensity between the two groups were 14.7 (4.7‐24.8, P = 0.005) during rest and 10.4 (1.6‐19.3, P = 0.007) during movement, favoring the lidocaine patch. The lidocaine patch produced a greater percentage change in a patients global impression than the vehicle patch. The incidence and severity of adverse events were low with both treatments. Conclusions: This study demonstrates that lidocaine patch 5%, applied twice a day, could serve as a well tolerated and effective modality to relieve moderate to severe pain associated with acute herpes zoster presumably through its pharmacological action and physical barrier effect on sensitized skin.

Application of Multivariate Empirical Mode Decomposition and Sample Entropy in EEG Signals via Artificial Neural Networks for Interpreting Depth of Anesthesia

EEG (Electroencephalography) signals can express the human awareness activities and consequently it can indicate the depth of anesthesia. On the other hand, Bispectral-index (BIS) is often used as an indicator to assess the depth of anesthesia. This study is aimed at using an advanced signal processing method to analyze EEG signals and compare them with existing BIS indexes from a commercial product (i.e., IntelliVue MP60 BIS module). Multivariate empirical mode decomposition (MEMD) algorithm is utilized to filter the EEG signals. A combination of two MEMD components (IMF2 + IMF3) is used to express the raw EEG. Then, sample entropy algorithm is used to calculate the complexity of the patients’ EEG signal. Furthermore, linear regression and artificial neural network (ANN) methods were used to model the sample entropy using BIS index as the gold standard. ANN can produce better target value than linear regression. The correlation coefficient is 0.790 ± 0.069 and MAE is 8.448 ± 1.887. In conclusion, the area under the receiver operating characteristic (ROC) curve (AUC) of sample entropy value using ANN and MEMD is 0.969 ± 0.028 while the AUC of sample entropy value without filter is 0.733 ± 0.123. It means the MEMD method can filter out noise of the brain waves, so that the sample entropy of EEG can be closely related to the depth of anesthesia. Therefore, the resulting index can be adopted as the reference for the physician, in order to reduce the risk of surgery.

Dexmedetomidine prevents alterations of intestinal microcirculation that are induced by surgical stress and pain in a novel rat model.

BACKGROUND: Anesthesia can become inadequate inadvertently or by misjudgment during surgery or emergence, and the surgical stress and pain stimulation will increase without adequate treatment. Overt stimulation may activate the sympathetic nervous system, increase the blood level of catecholamines, and lead to splanchnic arterial vasoconstriction. METHODS: We divided 30 male Wistar rats into the following 3 groups: control, surgical stress and pain (SSP), and surgical stress and pain + dexmedetomidine (SSP + Dex). The rats received midline laparotomy to exteriorize a segment of terminal ileum for microcirculation examination by a full-field laser perfusion imager and sidestream dark-field video microscope on mucosa, muscle, and Peyer patch. The inspired concentration of isoflurane was decreased from 1.2% to 0.7% in SSP and SSP + Dex groups. In the SSP + Dex group, the rats received an initial loading dose of dexmedetomidine (0.5 &mgr;g/kg) and a maintenance infusion (0.5 &mgr;g · kg−1 · h−1). RESULTS: Dexmedetomidine prevented surgical stress and pain-related tachycardia and hypertension, and it attenuated the reduction of the microcirculatory blood flow intensity in intestinal mucosa (1100 ± 185 perfusion units [PU] vs 800 ± 105 PU, P = 0.001) and muscle (993 ± 208 PU vs 713 ± 92 PU, P < 0.001). Dexmedetomidine restored perfused small vessel density in intestinal mucosa and muscle. CONCLUSIONS: We established a promising rat model to investigate the effect of surgical stress and pain stimulation on the intestinal microcirculation during light anesthesia. Using this rat model, we found that dexmedetomidine can normalize global hemodynamics and prevent the alteration of intestinal microcirculation.

Dental anesthesia for patients with special needs

To offer individualized dental treatment to certain patients who cannot tolerate dental treatment, sedation or general anesthesia is required. The needs could be either medical, mental, or psychological. The most common indications for sedation or general anesthesia are lack of cooperation, multiple morbidities, and pediatric autism. In adults, cognitive impairment and multiple morbidities are most commonly encountered indications. Because of suboptimal home care, incomplete medical history, poor preoperative management, lack of cooperation, and developmental abnormalities, it is a challenge to prepare anesthesia for patients with special needs. The American Society of Anesthesiology (ASA) has proposed guidelines for office-based anesthesia for ambulatory surgery. In patients with ASA physical status IV and V, sedation or general anesthesia for treatment in the dental office is not recommended. The distinction between sedation levels and general anesthesia is not clear. If intravenous general anesthesia without tracheal intubation is chosen for dental procedures, full cooperation between the dentist, dental assistant, and anesthesiologist is needed. Teamwork between the dentist and healthcare provider is key to achieve safe and successful dental treatment under sedation or general anesthesia in the patient with special needs.

The effect of 3,3-di-pyridyl-methyl-1-phenyl-2-indolinone on the nerve terminal currents of mouse skeletal muscles

The effects of 3,3-dipyridyl-methyl-1-phenyl-2-indolinone (DPMPI), a new cognition enhancer, on perineural waveforms were assessed on triangularis sterni nerve-muscle preparations in the mouse. The perineural waveforms were recorded with extracellular electrodes placed in the perineural sheaths of motor nerves. At 64.5 microM, DPMPI decreased the fast potassium current of the nerve terminal. The sodium current, calcium currents and calcium-dependent potassium current of the nerve terminal were not affected. At a greater concentration (215 microM), DPMPI decreased all of the components of the waveforms associated with sodium, potassium and calcium currents. It is concluded that DPMPI affects potassium, as well as sodium currents in the nerve terminal. The effect may contribute to its pharmacological actions on synaptic transmission.