Anesthetic premedication: new horizons of an old practice

The practice of anesthetic premedication embarked upon soon after ether and chloroform were introduced as general anesthetics in the middle of the 19(th) century. By applying opioids and anticholinergics before surgery, the surgical patients could achieve a less anxious state, and more importantly, they would acquire a smoother course during the tedious and dangerous induction stage. Premedication with opioids and anticholinergics was not a routine practice in the 20(th) century when intravenous anesthetics were primarily used as induction agents that significantly shorten the induction time. The current practice of anesthetic premedication has evolved into a generalized scheme that incorporates several aspects of patient care: decreasing preoperative anxiety, dampening intraoperative noxious stimulus and its associated neuroendocrinological changes, and minimizing postoperative adverse effects of anesthesia and surgery. Rational use of premedication in modern anesthesia practice should be justified by individual needs, the types of surgery, and the anesthetic agents and techniques used. In this article, we will provide our readers with updated information about premedication of surgical patients with a focus on the recent application of second generation serotonin type 3 antagonist, antidepressants, and anticonvulsants.

Pharmacokinetics of sevoflurane elimination from respiratory gas and blood after coronary artery bypass grafting surgery

PURPOSE

Sevoflurane, with a relative low blood-gas partition coefficient, is an ideal anesthetic to achieve rapid offset and recovery from general anesthesia. This study will determine the profiles of four concentration-time curves to characterize the pharmacokinetics of sevoflurane elimination.

METHODS

Eight patients (aged 54-76 years) undergoing coronary arterial bypass grafting surgery were enrolled in this study. At the end of surgery, anesthetic gas and blood were sampled 20 min before and after stopping sevoflurane administration, with prior maintenance of a fixed 5% inspired sevoflurane (CIsev) in 6 L/min oxygen flow for 60 min before the cessation of sevoflurane administration for the subsequent 20 min elimination. An infrared analyzer was used to determine both CIsev and end-tidal sevoflurane (CEsev). The sevoflurane concentrations in the internal jugular-bulb (Jsev), arterial (Asev) and pulmonary arterial blood (PAsev) were analyzed by gas chromatography, and cardiac output was measured using an Opti-Q pulmonary artery catheter.

RESULTS

A bi-exponential decay function was the best fit for the CEsev,Jsev, Asev, and PAsev time curves. There were two distinct components, the initial 5-min fast or distribution phase and the subsequent 15-min slow or elimination phase. Before cessation of the sevoflurane supplement, the step-down concentration of sevoflurane was listed in the following order: CIsev > CEsev > Asev ≧ Jsev > PAsev. During the elimination phase, the fastest decay occurred in CEsev, followed by Jsev, Asev and PAsev. Therefore, a reverse step-down pattern was observed (PAsev > Asev ≧ Jsev > CEsev) after 20 min. The ratio of Asev to CEsev was 89% at baseline before stopping sevoflurane administration, but the ratio of Asev to CEsev increased to 128% at the twentieth min of the sevoflurane elimination phase.

CONCLUSIONS

During elimination, the initial washout of sevoflurane from the functional residual capacity of the lungs was reflected in the fast component of the CEsev, Jsev, Asev, and PAsev time curves. In contrast, the slow component was dominated by the tangible effects of the physiological membrane barriers, such as the alveoli-pulmonary capillary and blood-brain barriers.

Efficacy of intramuscular nalbuphine versus diphenhydramine for the prevention of epidural morphine-induced pruritus after cesarean delivery

BACKGROUND

Pruritus is the most common side effect of epidural morphine analgesia. Diphenhydramine is a widely used agent for the treatment of urticarial pruritus. Nalbuphine is a mixed opioid agonist-antagonist and has been reported to be effective in treating opioid-induced pruritus. We compared the effectiveness of intramuscular diphenhydramine and nalbuphine for the prevention of epidural morphine-induced pruritus after cesarean section.

METHODS

One hundred and fifty, American Society of Anesthesiologists physical status I or II, women undergoing cesarean section with epidural anesthesia were randomly assigned to three groups. Group S, group D, and group N received intramuscular normal saline (1 ml; n = 50), diphenhydramine (30 mg/1 ml; n = 50), and nalbuphine (10 mg/1 ml; n = 50), respectively, after delivery of the baby. The occurrence and the severity of pruritus were assessed at 1, 4, 12, and 24 hours after surgery.

RESULTS

The overall incidence of pruritus during the 24 hr follow-up period was 72%, 68%, and 44% for group S, group D, and group N, respectively. Pruritus occurred less frequently in group N than group D (p = 0.027). At 4 and 12 hrs postoperatively, the pruritus severity was significantly different (p = 0.003 and p = 0.002) and was significantly less in group N than group D in the intergroup comparison (p = 0.013 and p = 0.012).

CONCLUSION

Nalbuphine proved better than diphenhydramine for prevention of epidural morphine-induced pruritus in patients who underwent cesarean section. Prophylactic intramuscular nalbuphine (10 mg) is effective in decreasing the incidence and severity of pruritus and does not affect analgesia.

Efficacy of mirtazapine in preventing intrathecal morphine-induced nausea and vomiting after orthopaedic surgery*

Nausea and vomiting are frequent complications of intrathecal morphine. In this randomised, double-blind trial, we tested the efficacy of mirtazapine, an antidepressant that blocks receptors associated with vomiting, on the incidence of nausea and vomiting after intrathecal morphine. One hundred patients receiving spinal anaesthesia for lower limb surgery were assigned equally to take either an orally disintegrating form of 30 mg mirtazapine or matching placebo 1 h before surgery. Spinal anaesthesia was performed by injection of 15 mg isobaric bupivacaine 0.5% along with 0.2 mg preservative-free morphine. Nausea and vomiting were evaluated 3, 6, 12, 18 and 24 h after intrathecal morphine administration. The incidence of nausea and vomiting was significantly lower in patients receiving mirtazapine compared with placebo (26.5% vs 56.3%, respectively; p = 0.005). The mean (SD) onset time of postoperative nausea and vomiting was significantly delayed in mirtazapine patients: 9.4 (2.5) vs 5.2 (1.8) h, respectively; p < 0.0001. The severity of nausea and vomiting was also decreased after mirtazapine at the 3-6 h and 6-12 h periods. Our data indicate that pre-operative mirtazapine decreases the incidence, delays the onset and reduces the severity of nausea and vomiting induced by intrathecal morphine in patients undergoing spinal anaesthesia.

Prophylactic mirtazapine reduces intrathecal morphine-induced pruritus

BACKGROUND

Activation of the serotonergic system is an important factor in the pathogenesis of intrathecal morphine-induced pruritus. Mirtazapine is a new antidepressant that selectively blocks 5-HT(2) and 5-HT(3) receptors. We therefore tested the hypothesis that preoperative mirtazapine would reduce the incidence of intrathecal morphine-induced pruritus.

METHODS

One hundred and ten ASA I patients undergoing lower limb surgery under spinal anaesthesia were randomly allocated into two equal groups and received either mirtazapine 30 mg or an orally disintegrating placebo tablet 1 h before operation in a prospective, double-blinded trial. All patients received an intrathecal injection of 15 mg of 0.5% isobaric bupivacaine and 0.2 mg preservative-free morphine. The occurrence and the severity of pruritus were assessed at 3, 6, 9, 12, and 24 h after intrathecal morphine.

RESULTS

Pruritus was significantly more frequent in the placebo group compared with the mirtazapine group (75% vs 52%, respectively; P=0.0245). The time to onset of pruritus in the two groups was also significantly different. The patients who experienced pruritus in the placebo group had a faster onset time than that in the mirtazapine group [mean (sd): 3.2 (0.8) vs 7.2 (4.1) h, P<0.0001].

CONCLUSIONS

Mirtazapine premedication prevents pruritus induced by intrathecal morphine in patients undergoing lower limb surgery with spinal anaesthesia.

Epidural Clonidine for Postoperative Pain After Total Knee Arthroplasty: A Dose–Response Study

BACKGROUND

Combinations of epidural clonidine, local anesthetics, and opioids have improved postoperative analgesia after total knee arthroplasty. In this study we sought to determine the optimal epidural bolus dose of clonidine, which provides the best analgesia and fewest side effects.

METHODS

Eighty ASA I-III patients, who underwent total knee arthroplasty were randomly assigned to one of four groups of 20 patients each. Identical epidural anesthesia procedures were used for all groups. After surgery, groups C0, C1, C2, and C4 received patient-controlled epidural analgesia (PCEA) with clonidine (0, 1.0, 2.0, or 4.0 mug/mL, respectively) and morphine (0.1 mg/mL) in 0.2% ropivacaine. The analgesia effect was estimated by PCEA consumption volume and visual analog pain scale at rest and with movement at 1, 2, 4, 12, 24, 48, and 72 h after surgery. Systolic blood pressure, heart rate, sedation, and sensory and motor blockade were also recorded for 72 h after surgery.

RESULTS

The PCEA consumption volume for groups C0, C1, C2, and C4 were 71.8 +/- 19.5 mL, 49.6 +/- 12.3 mL, 48.1 +/- 9.3 mL, and 39.4 +/- 9.0 mL, respectively. The clonidine groups experienced less postoperative pain (P = 0.002). In the C4 group, four patients had prolonged sensory blockade and one patient had both severe sedation and prolonged sensory motor blockade. No significant statistical difference in analgesic consumption (P = 0.78) and pain intensity (P = 0.66) between groups C1 and C2 were noted.

CONCLUSIONS

The optimal amount of epidural clonidine in a solution of morphine and ropivacaine for postoperative pain management is 1.0 microg/mL.

Premedication with intravenous low-dose ketamine suppresses fentanyl-induced cough

STUDY OBJECTIVE

To evaluate the effect of low-dose ketamine on fentanyl-induced cough.

DESIGN

Prospective, randomized, double-blind, placebo-controlled clinical trial.

SETTING

Medical center hospital.

PATIENTS

360 ASA physical status I-II patients aged 18 to 65 years, weighing between 40 and 80 kg, and scheduled for elective surgery during general anesthesia.

INTERVENTIONS AND MEASUREMENTS

Patients were randomly assigned to receive either ketamine 0.15 mg/kg or placebo (equal volume of 0.9% saline) given intravenously over 10 seconds, one minute before administration of fentanyl (1.5 microg/kg IV, injected within 5 seconds), during induction of general anesthesia. Any episode of cough was classified as coughing and the onset time of cough (the time of the first episode of cough) was observed for one minute after fentanyl administration by a blinded observer. Severity of coughing was graded based on the number of episodes of coughing (mild, 1-2; moderate, 3-5; and severe, >5). Blood pressure, heart rate, and pulse oximetry oxygen saturation (Spo2) were recorded before giving ketamine or 0.9% saline and 1 minute after fentanyl injections.

MAIN RESULTS

After the intravenous injection of fentanyl bolus, patients in the placebo group showed significantly higher frequency cough than those in the ketamine pretreatment group (21.6% vs 7.2%, P<0.05), and onset time of the ketamine group was significantly longer than that of the control group (20+/-8 vs 15+/-10 seconds, P<0.01). However, no difference in cough severity was observed between the two groups.

CONCLUSION

Low-dose ketamine (0.15 mg/kg IV) effectively reduces fentanyl-induced cough and delays the onset time of cough.

Gabapentin relieves post-dural puncture headache--a report of two cases

Post-dural puncture headache (PDPH) is a vexing problem of the patients following spinal anesthesia or a complication relative to inadvertent dural puncture in epidural anesthesia. The prevention and management of PDPH contain a laddered forestallment and therapy with varying results. The anticonvulsant gabapentin has been reported to be effective in prophylaxis and treatment of headaches. We report here two cases of PDPH, who failed to respond to traditional analgesics, but had good response to gabapentin. After treatment with gabapentin 400 mg three times daily, the headache was relieved remarkably in 24 hr. Discussions of the pathophysiology of PDPH, pharmacological actions of gabapentin, and possible mechanisms of action of gabapentin on PDPH are brought forward in the text.

Comparison of the effects of thoracic epidural analgesia and i.v. infusion with lidocaine on cytokine response, postoperative pain and bowel function in patients undergoing colonic surgery

BACKGROUND

Both thoracic epidural analgesia (TEA) and i.v. lidocaine were able to decrease postoperative pain and duration of ileus. We compared TEA and i.v. lidocaine (IV) regarding their effects on cytokines, pain and bowel function after colonic surgery.

METHODS

Sixty patients were randomly allocated to one of the three groups. TEA group had lidocaine 2 mg kg(-1) followed by 3 mg kg(-1) h(-1) epidurally and an equal volume of i.v. normal saline. The IV group received the same amount of lidocaine i.v. and normal saline epidurally. The control group received normal saline via both routes. These regimens were started 30 min before surgery and were continued throughout. Blood cytokines were measured at scheduled times within 72 h.

RESULTS

Both TEA and IV groups had better pain relief. The total consumptions using patient-controlled epidural analgesia were 81.6 (6.5), 55.0 (5.3) and 45.6 (3.9) ml (P<0.01) and the times of flatus passage were 50.2 (4.9), 60.2 (5.8) and 71.7 (4.7) h (P<0.01) in the TEA, IV and control groups, respectively. The TEA group exhibited the best postoperative pain relief and the least cytokine surge. The IV group experienced better pain relief and less cytokine release than the control group.

CONCLUSIONS

The TEA lidocaine had better pain relief, lower opioid consumption, earlier return of bowel function and lesser production of cytokines than IV lidocaine during 72 h after colonic surgery; IV group was better than the control group.

Comparing the effects of minimal low-flow desflurane with that of semi-close high flow desflurane on perioperative cytokine response in patients undergoing gastrectomy

BACKGROUND

Anesthetic techniques may influence the perioperative cytokine response. We investigate two anesthetic techniques: minimal low-flow anesthesia (LFA) and semi-closed high flow anesthesia (HFA) with desflurane on the effect of cytokine response in gastrectomy.

METHODS

Forty patients scheduled to undergo elective gastrectomy were randomly allocated to LFA (0.3 mL/min) or HFA (2 L/min) group. Blood was sampled for measurement of tumor necrosis factor (TNF), interleukin (IL)-6, IL-8, and IL-1 receptor antagonist (RA) at scheduled intervals. Hemodynamic responses, desflurane concentrations, numbers of patient using cardiovascular agents, and frequency of vaporizer manipulations were recorded during the operation.

RESULTS

For patients in the LFA group, production of IL-8 was significantly less increased at the end of the surgical procedure; however there was no significant difference in total production between groups. There was no significant difference in TNF, IL-6, and IL-1RA production throughout the observed period. The desflurane vaporizer was adjusted more frequently (4 [13-6] versus 2 [1-3] times) for patients in the HFA group, and more patients in this group required the use of cardiovascular agents (10 versus 4) than patients in the LFA group during the operation.

CONCLUSIONS

The current study demonstrates that smaller increase in cytokine production in the LFA than HFA with desflurane for the patients receiving gastrectomy.