Biomedical subjects

Lok-Hi Chow

Publications and source records attributed to Lok-Hi Chow.

9 recordsLinked to original sources

PubMed2006

Urinary catheterization may not be necessary in minor surgery under spinal anesthesia with long-acting local anesthetics.

BACKGROUND: This prospective study was designed to compare the incidence of urinary retention after spinal anesthesia between 0.5% hyperbaric bupivacaine and 0.5% hyperbaric tetracaine in patients who underwent minor orthopedic and general surgeries. METHODS: Eighty patients aged 18-40 were randomly assigned to receive either hyperbaric bupivacaine or tetracaine for spinal anesthesia. Intravenous fluids were administered for maintenance of basal requirement, replacement of blood loss and prevention of hypotension. The highest level of analgesia, regression time of sensory block to L5 level, length of time from spinal injection to spontaneous urinary voidance, and volume of perioperative fluid administered were recorded. RESULTS: Of the 80 patients who received either hernioplasty, fistulectomy, hemorroidectomy or orthopedic surgery, two were catheterized (2.5%) because of urinary retention. They were administered less than 800 mL of fluid intraoperatively. Intraoperative blood loss was less than 100 mL in all cases. There were no statistical differences in demographic data, types of surgery, sensory blockade and perioperative fluid administration between the two groups. Although the regression time of sensory blockade with tetracaine (means +/- SD, 259.3 +/- 39.6 min) was significantly longer than that of bupivacaine (225.0 +/- 38.6 min, P < 0.01), the time elapsing from the spinal injection to the first spontaneously voiding after surgery did not show statistical difference between two groups (433.9 +/- 89.1 vs. 411.0 +/- 98.3 min, P = 0.286). CONCLUSIONS: Our results show that, in younger surgical patients who did not receive large amount of fluid intraoperatively, the incidence of urinary retention was low, although prolonged sensory blockade by both long-acting local anesthetics was evident. Thus, urinary catheterization should not be a routine must for every patient undergoing minor surgery with long-acting spinal local anesthetics. From the viewpoint of financial expense, avoidance of complication and annoyance of urinary catheterization, careful observation of urinary bladder fullness in the form of lower abdominal distension, discomfort, bradycardia, or vomiting after surgery is superior to routine retention urinary catheterization just for ease with work in younger patients under-going minor surgery under long-acting spinal local anesthetics.

Adult↗

PubMed2005

Dextromethorphan differentially affects opioid antinociception in rats.

Opioid drugs such as morphine and meperidine are widely used in clinical pain management, although they can cause some adverse effects. A number of studies indicate that N-methyl-D-aspartate (NMDA) receptors may play a role in the mechanism of morphine analgesia, tolerance and dependence. Being an antitussive with NMDA antagonist properties, dextromethorphan (DM) may have some therapeutic benefits when coadministered with morphine. In the present study, we investigated the effects of DM on the antinociceptive effects of different opioids. We also investigated the possible pharmacokinetic mechanisms involved. The antinociceptive effects of the mu-opioid receptor agonists morphine (5 mg kg(-1), s.c.), meperidine (25 mg kg(-1), s.c.) and codeine (25 mg kg(-1), s.c.), and the kappa-opioid agonists nalbuphine (8 mg kg(-1), s.c.) and U-50,488H (20 mg kg(-1), s.c.) were studied using the tail-flick test in male Sprague-Dawley rats. Coadministration of DM (20 mg kg(-1), i.p.) with these opioids was also performed and investigated. The pharmacokinetic effects of DM on morphine and codeine were examined, and the free concentration of morphine or codeine in serum was determined by HPLC.It was found that DM potentiated the antinociceptive effects of some mu-opioid agonists but not codeine or kappa-opioid agonists in rats. DM potentiated morphine's antinociceptive effect, and acutely increased the serum concentration of morphine. In contrast, DM attenuated the antinociceptive effect of codeine and decreased the serum concentration of its active metabolite (morphine). The pharmacokinetic interactions between DM and opioids may partially explain the differential effects of DM on the antinociception caused by opioids.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed2004

Effects of morphine and endomorphins on the polysynaptic reflex in the isolated rat spinal cord.

At the spinal level, mu-opioids exert their actions on nociceptive primary afferent neurons both pre- and postsynaptically. In the present study, we used an in vitro isolated neonatal rat (11-15 days old) spinal cord preparation to examine the effects of morphine and the endogenous mu-opioid ligands endomorphin-1 (EM-1) and endomorphin-2 (EM-2) on the polysynaptic reflex (PSR) of dorsal root-ventral root (DR-VR) reflex. The actions of mu-opioids on spinal nociception were investigated by quantification of the firing frequency and the mean amplitude of the PSR evoked by stimuli with 20 x threshold intensity. EM-1 decreased the mean amplitude of PSR, whereas EM-2 and morphine decreased the firing frequency. The pattern of the effects elicited by morphine was the same as that for EM-2, except at high concentration. Naloxonazine, a selective mu(1) opioid receptor antagonist, had no significant effect on PSR by itself, but blocked the inhibition of PSR firing frequency or amplitude induced by EM-1, -2 and morphine. This may suggest that EM-1, EM-2 and morphine modulate spinal nociception differently and act mainly at the mu(1)-opioid receptors. Although they all act via mu(1)-opioid receptors, their different effects on the PSR may suggest the existence of different subtypes of the mu(1)-opioid receptor. The present data is also consistent with a further hypothesis, namely, that morphine and EM-2 activate a subtype of mu(1)-opioid receptor presynaptically, while EM-1 acts mainly through another subtype postsynaptically. However, since other reports indicate that EM-2, but not EM-1, could stimulate the release of enkephalins or dynorphin, presynaptic delta and kappa receptors may be also involved indirectly in the different regulation by mu-opioids at the spinal level.

Analgesics, Opioid↗

PubMed2004

Dextromethorphan potentiates morphine antinociception at the spinal level in rats.

PURPOSE: Morphine is an effective analgesic, but adverse effects limit its clinical use in higher doses. The non-opioid antitussive, dextromethorphan (DM), can potentiate the analgesic effect of morphine and decrease the dose of morphine in acute postoperative pain, but the underlying mechanism remains unclear. We previously observed that DM increases the serum concentration of morphine in rats. Therefore, we investigated the effects of drugs administered at the spinal level to exclude possible pharmacokinetic interactions. As DM has widespread binding sites in the central nervous system [such as N-methyl-D-aspartate (NMDA) receptors, sigma receptors and alpha(3)ss(4) nicotinic receptors], we investigated whether the potentiation of morphine antinociception by DM at the spinal level is related to NMDA receptors. METHODS: We used MK-801 as a tool to block the NMDA channel first, and then studied the interaction between intrathecal (i.t.) morphine and DM. The tail-flick test was used to examine the antinociceptive effects of different combinations of morphine and other drugs in rats. RESULTS: DM (2-20 microg) or MK-801 (5-15 microg) showed no significant antinociceptive effect by themselves. The antinociceptive effect of morphine (0.5 microg, i.t.) was significantly enhanced by DM and reached the maximal potentiation (43.7%-50.4%) at doses of 2 to 10 microg. Pretreatment with MK-801 (5 or 10 microg, i.t.) significantly potentiated morphine antinociception by 49.9% or 38.7%, respectively. When rats were pretreated with MK-801, DM could not further enhance morphine antinociception (45.7% vs 50.5% and 43.3%). CONCLUSION: Our results suggest that spinal NMDA receptors play an important role in the effect of DM to potentiate morphine antinociception.

Analgesics, Opioid↗

PubMed2003

Fatal gas embolism during transurethral incision of the bladder neck under spinal anesthesia.

UNLABELLED: We report a case of fatal gas embolism during transurethral incision of the bladder neck under spinal anesthesia in a 76-yr-old man. We confirmed the diagnosis of venous gas embolism by aspiration of frothy blood through the double-lumen central venous catheter and by observation on the transesophageal echocardiogram of a massive gas embolism in the right atrium and right ventricle with obstruction of right ventricle outflow. This report is presented in an attempt to remind anesthesiologists of this unusual but potentially fatal complication that may occur during common transurethral surgery. IMPLICATIONS: We report a patient undergoing transurethral incision of the bladder neck who developed a fatal gas embolism. This report is presented in an attempt to remind anesthesiologists of this unusual but potentially fatal complication that may occur during common transurethral surgery.

Aged↗

PubMed2002

Gender and pain upon movement are associated with the requirements for postoperative patient-controlled iv analgesia: a prospective survey of 2,298 Chinese patients.

PURPOSE: To investigate prospectively the influence of patient characteristics upon, and the association of postoperative measurements with, the requirements for postoperative morphine and the assessment of resting pain and pain upon movement in Chinese patients. METHODS: From January 1998 to December 1999, patients receiving patient-controlled iv morphine subsequent to general anesthesia and surgery at our institute (Kaohsiung Veterans General Hospital), were enrolled in the study. Demographic data (such as gender, age, weight, height and education level) and postoperative measurements, including pain scores at rest or during movement, sedation scores and morphine consumption, were recorded. RESULTS: In total 2,298 patients were recruited. Females consumed significantly less morphine via patient-controlled analgesia (PCA) in the first three postoperative days than was the case for males (P <0.05). Gender was the strongest predictor for postoperative morphine requirements. Postoperative pain upon movement was another effective predictor for morphine requirement (P <0.05). Age, body height, body weight, education and operation sites were not associated with morphine consumption. CONCLUSION: Gender and postoperative pain upon movement are the major factors influencing morphine requirement for patient-controlled iv morphine analgesia during the first three postoperative days in Chinese patients.

Adult↗

PubMed2002

Oral clonidine reduces myocardial ischemia in patients with coronary artery disease undergoing noncardiac surgery.

BACKGROUND: To access the clinical effect of clonidine on reduction of myocardial ischemia events in patients with history of coronary artery disease undergoing noncardiac surgeries. METHODS: Sixty ASA class III patients with coronary artery disease were allotted at random to two groups in a prospective, double-blind study to receive either clonidine (3 micrograms/kg) or placebo (control group) 90 minutes before arrival at the operating room. Continuous EKG monitoring (Holter monitor) was performed to analyze the ST segment in lead II, V2 and V5 during the preoperative (since late hours the night before operation), intraoperative and early postoperative periods (total monitoring time = 24 hours). The episode of myocardial ischemia defined as the magnitude of ST segment depression of at least 1 mm, occurring 60 ms after the J point and persisting for three minutes or more was recorded. Perioperative hemodynamic data were analyzed with two-way ANOVA with repeated measures. Student's t-test for unpaired data was used for analysis of demographics. Chi-square test was used for ST segment changes. Results are expressed as mean +/- SD and P < 0.05 was considered to be statistically significant. RESULTS: In the control group, 9 patients (30%) were noted to have episodes of ischemia preoperatively, 7 patients (23.3%) intraoperatively, and 12 patients (40%) postoperatively. The occurrence of myocardial ischemia peaked in the early postoperative period (P < 0.05). On the contrary, in the clonidine group, 10 patients (33.3%) saw ischemic episodes preoperatively, 3 patients (10%) intraoperatively and 5 patients (16.7%) postoperatively. The incidence of myocardial ischemia in clonidine group was significantly lower than that in placebo group in intraoperative and postoperative periods. The mean arterial pressure was significantly lower in some clonidine-treated patients during perioperative periods (P < 0.05). A number of patients in clonidine group suffered from drowsiness (66.7%) after operation (P < 0.05), but they could be easily aroused. In regard to dryness of mouth, nausea and vomiting clonidine and control groups did not differ much (P > 0.05). Demerol consumption was significantly lower in clonidine group (43.7 +/- 4.6 mg) than in control group (76.3 +/- 3.7 mg, P < 0.05). CONCLUSIONS: We conclude that premedication with oral clonidine can significantly reduce the incidence of perioperative myocardial ischemia in patients with CAD undergoing noncardiac surgeries. The incidence of myocardial ischemia in these patients is rather high during perioperative period, which deserves our exceptional caution.

Administration, Oral↗

PubMedDate not supplied

Dextromethorphan potentiates morphine-induced antinociception at both spinal and supraspinal sites but is not related to the descending serotoninergic or adrenergic pathways.

Morphine is a strong and widely used opioid analgesic in pain management, but some adverse effects limit its clinical use at high doses. The clinically available non-opioid antitussive, dextromethorphan (DM) can potentiate the analgesic effect of morphine and decrease the dose of morphine in acute postoperative pain. However, the mechanism underlying this synergistic phenomenon is still not clear. To examine if the potentiation by DM occurs through the descending pain-inhibitory pathways, ketanserin (a 5-HT2 receptor antagonist) and yohimbine (an alpha2-adrenergic receptor antagonist) were employed and found to have no significant effect on the potentiation by DM. Using local delivery of drugs in rats in the present study, potentiation of morphine-induced antinociception by DM was observed via both intrathecal and intracerebroventricular routes, suggesting that both spinal and supraspinal sites are involved. This suggests that the potentiation of morphine-induced antinociception by DM is not mediated by the serotoninergic or adrenergic descending pain-inhibitory pathways. The present results are consistent with findings in clinical studies, which showed that DM can effectively decrease the consumption of morphine in patients suffering from pain. Since DM has excellent clinical potential as a synergistic agent with morphine, further investigating and clarifying the possible pharmacological mechanism of DM are of great importance for future studies.

Adrenergic Agents↗

PubMedDate not supplied

Does postoperative pain induce emesis?

OBJECTIVE: The aim of this prospective, controlled study was to evaluate the risk factors for postoperative emesis in patients undergoing gynecologic surgery and receiving patient-controlled analgesia for three days. METHODS: Six hundred twenty-five gynecologic patients with an American Society of Anesthesiologists physical status of I to III undergoing lower-abdominal surgeries were enrolled. A standard, general anesthetic technique was used. Postoperative pain was treated by a patient-controlled analgesia device with bolus intravenous doses of 1 mg morphine. For 3 days after surgery patients were assessed for occurrence of emesis, sedation, and pain intensity when at rest and during movement. RESULTS: The incidence of emesis was 26% on postoperative day 1, 13% on day 2, and 4% on day 3. On all 3 days, patients' pain scores when at rest and when coughing were higher for those with emesis than for those without. During the first 2 postoperative days the patients with and those without emesis consumed similar amounts of morphine daily, but on the third day the patients with emesis consumed significantly more morphine than did those without emesis ( <0.05). Further logistic regression analysis showed that incident pain was the main risk factor for postoperative emesis on all 3 days. CONCLUSIONS: The results suggested that postoperative pain was an associative risk factor to increase the incidence of emesis in these female patients.

Female↗