Prolongation of succinylcholine block by metoclopramide

Pseudocholinesterase Enzyme Deficiency in Adıyaman City Area

OBJECTIVE

Pseudocholinesterase (PChE) is an enzyme responsible for the hydrolysis of succinylcholine. In case of its deficiency, the effect of succinylcholine that is approximately 5-10 min is prolonged up to few hours. The use of succinylcholine has been declined recently. However, it is still actively used in some special conditions and in developing countries. In this study, incidence of PChE enzyme deficiency around Adiyaman city was investigated and presented with the literature review.

METHODS

After obtaining an approval from the investigational board of our hospital (Adiyaman University Medical School, Biomedical Research Ethics Board, 30.12.2012, Nr: B.30.2.ADY.0.20.00-600/51), patients undergoing any elective operation under general anaesthesia in the Adiyaman University Medical School Hospital between March and December 2013 were recruited for the study. After obtaining the patients' written consents, blood PChE, alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, creatinine, international normalisation ratio (INR) and activated partial thromboplastin time (aPTT) values of the patients were analysed. Possible association of the PChE deficiency with other values was also investigated. The normal value of PChE was taken as 4260-11250 for females aged 16-40 years and 5320-12920 U L(-1) for other patients.

RESULTS

The study was completed with 964 patients, 702 (72.8%) of whom were females. PChE enzyme levels were under the normal in 7.2% of the patients. There were no correlation between patient group, ALT, INR, aPTT and creatinine elevation with PChE deficiency (p>0.05), whereas AST and urea level elevation was significantly associated with PChE deficiency (p<0.05). The risk of PChE deficiency was 4.5 and 9 times higher in the patients with the elevation of AST and urea levels, respectively.

CONCLUSION

Pathological elevations of AST and urea that are a part of normal pre-operative biochemical analysis of blood will indicate the possible deficiency of PChE enzyme.

Clinical conundrums and challenges during geriatric orthopedic emergency surgeries

Despite so many advancements and innovations in anesthetic techniques, expectations and challenges have also grown in plenty. Cardiac, pediatric, obstetric and neuro-anesthesia have perfectly developed to fulfill the desired needs of respective patient population. However, geriatric anesthesia has been shown a lesser interest in teaching and clinical practices over the years as compared with other anesthetic sub-specialties. The large growing geriatric population globally is also associated with an increase number of elderly patients presenting for orthopedic emergency surgeries. Orthopedic emergency surgery in geriatric population is not only a daunting clinical challenge but also has numerous socio-behavioral and economic ramifications. Decision making in anesthesia is largely influenced by the presence of co-morbidities, neuro-cognitive functions and the current socio-behavioral status. Pre-anesthetic evaluation and optimization are extremely important for a better surgical outcome but is limited by time constraints during emergency surgery. The current review aims to highlight comprehensively the various clinical, social, behavioral and psychological aspects during pre-anesthetic evaluation associated with emergency orthopedic surgery in geriatric population.

Reversal of succinylcholine induced apnea with an organophosphate scavenging recombinant butyrylcholinesterase

BACKGROUND

Concerns about the safety of paralytics such as succinylcholine to facilitate endotracheal intubation limit their use in prehospital and emergency department settings. The ability to rapidly reverse paralysis and restore respiratory drive would increase the safety margin of an agent, thus permitting the pursuit of alternative intubation strategies. In particular, patients who carry genetic or acquired deficiency of butyrylcholinesterase, the serum enzyme responsible for succinylcholine hydrolysis, are susceptible to succinylcholine-induced apnea, which manifests as paralysis, lasting hours beyond the normally brief half-life of succinylcholine. We hypothesized that intravenous administration of plant-derived recombinant BChE, which also prevents mortality in nerve agent poisoning, would rapidly reverse the effects of succinylcholine.

METHODS

Recombinant butyrylcholinesterase was produced in transgenic plants and purified. Further analysis involved murine and guinea pig models of succinylcholine toxicity. Animals were treated with lethal and sublethal doses of succinylcholine followed by administration of butyrylcholinesterase or vehicle. In both animal models vital signs and overall survival at specified intervals post succinylcholine administration were assessed.

RESULTS

Purified plant-derived recombinant human butyrylcholinesterase can hydrolyze succinylcholine in vitro. Challenge of mice with an LD100 of succinylcholine followed by BChE administration resulted in complete prevention of respiratory inhibition and concomitant mortality. Furthermore, experiments in symptomatic guinea pigs demonstrated extremely rapid succinylcholine detoxification with complete amelioration of symptoms and no apparent complications.

CONCLUSIONS

Recombinant plant-derived butyrylcholinesterase was capable of counteracting and reversing apnea in two complementary models of lethal succinylcholine toxicity, completely preventing mortality. This study of a protein antidote validates the feasibility of protection and treatment of overdose from succinylcholine as well as other biologically active butyrylcholinesterase substrates.

The potency of succinylcholine in obese adolescents

We constructed a single-dose response curve for succinylcholine in 30 obese adolescents during thiopental-fentanyl anesthesia administration by using 100 microg/kg, 150 microg/kg, or 250 microg/kg IV. The maximal response (percent depression of neuromuscular function) of the adductor pollicis to supramaximal train-of-four stimuli was recorded by using a Datex (Helsinki, Finland) relaxograph. Linear regression and inverse prediction were used to determine doses of succinylcholine to produce 50% (ED(50)), 90% (ED(90)), and 95% (ED(95)) depression of neuromuscular function. The ED(50), ED(90), and ED(95) were 152.8 microg/kg (95% confidence interval: 77.8-299.5), 275.4 microg/kg (95% confidence interval: 142-545.7), and 344.3 microg/kg (95% confidence interval: 175.3-675. 3), respectively. This ED(50) is similar to the dose reported for similarly aged, nonobese adolescents, 147 microg/kg. The previously reported ED(95) for succinylcholine in nonobese adolescents, 270 microg/kg, is within the 95% confidence interval generated for ED(95) in our study.

IMPLICATIONS

The potency estimates for succinylcholine in obese (body mass index > 30 kg/m(2)) adolescents are comparable to those in similarly aged nonobese adolescents when dosing is calculated based on total body mass and not lean body mass. When a rapid sequence induction of anesthesia is considered in an obese adolescent, the dose of succinylcholine should be based on actual (not lean) body mass.

Preoperative assessment of the elderly patient

Organ system functional reserve variability increases progressively with age. In elderly patients, cardiopulmonary, central nervous system, and metabolic functional reserve seem to be the most important predictors of the ability to undergo surgery. Directed testing for the assessment of organ system functional reserve and identification of organs at risk, rather than the diagnosis of disease itself, is the primary goal of preoperative evaluation prior to surgery and is essential to the formulation of an effective anesthetic plan. The risks of adverse drug interaction, already high in the elderly, make a thorough review of the indications and dosage of perioperative medication an important part of the preoperative assessment process.

The reversal of profound mivacurium-induced neuromuscular blockade

PURPOSE

Mivacurium is metabolized by plasma cholinesterase catalyzed ester hydrolysis. Acetylcholinesterase antagonists used in the reversal of muscle relaxation may also inhibit plasma cholinesterase and, therefore, delay the hydrolysis of mivacurium. The clinical interaction between acetylcholinesterase antagonists and mivacurium induced neuromuscular blockade was studied.

METHOD

Intraoperative muscle relaxation was maintained with a mivacurium infusion to achieve a constant intense block (first twitch, T1, 2-3% of control). Patients were randomly divided into three groups. Patients in Group 1 received no anticholinesterase, in Group 2 neostigmine 0.07 mg.kg-1, and in Group 3 edrophonium 1 mg.kg-1. The times between termination of the mivacurium infusion (Group 1) or the administration of the anticholinesterase (Groups 2 and 3) to 25%, 50%, 75% and 95% T1 recovery, and to 50%, 70% and 90% recovery in the ratio, T4/T1 (TR) were recorded.

RESULT

In the neostigmine Group, T1 recovery to 25%, 50% and 75% (2.32 +/- 1.41, 3.90 +/- 1.85 and 6.88 +/- 2.66 min) was accelerated compared with control (3.36 +/- 1.34, 5.78 +/- 2.22, and 8.58 +/- 3.60, and), but recovery to 95% (18.53 +/- 9.09 vs 13.29 +/- 5.24 min) was delayed. Also, TR recovery to 50%, 70%, and 90% was slower (14.47 +/- 8.73, 21.25 +/- 11.06 and 31.37 +/- 12.11 min vs 11.75 +/- 3.74, 13.78 +/- 4.39 and 17.86 +/- 6.44 min). However, all T1 and TR recovery times were decreased in the edrophonium group (0.88 +/- 0.51, 2.00 +/- 1.50, 4.97 +/- 2.96, and 9.35 +/- 5.24 min for T1 and 6.86 +/- 3.93, 9.05 +/- 4.51 and 12.24 +/- 6.66 min for TR).

CONCLUSION

Neostigmine reversal of intense mivacurium neuromuscular block should be avoided, as this may result in prolongation of the block.

Pharmacokinetic drug interactions with gastrointestinal motility modifying agents

Drugs may affect gastrointestinal motility and, therefore, absorption of other concomitantly administered drugs. Gastrointestinal prokinetic agents increase the rate of gastric emptying and also upper intestinal motility. These effects would be expected to increase the initial rate of absorption of orally administered drugs, but reduce total bioavailability of the agents. Metoclopramide has been shown to increase the rate of absorption of several classes of drug, reflected by reduced time taken to achieve maximal plasma concentration (tmax) and increased maximal plasma concentration (Cmax). However, the effect of these agents on the area under the plasma concentration-time curve from zero to infinity (AUC0-infinity), when measured, is not consistent. Cisapride and domperidone appear to have similar effects, but there are relatively less data available regarding these products. Opioids may delay gastric emptying considerably, an effect which will often have significant clinical and therapeutic implications. Most of the data confirming this observation concern oral analgesics, but the effect should be considered when prescribing any oral medication. Drugs with anticholinergic or sympathomimetic activity are likely to have a similar effect and this is confirmed, in the main, by the limited data available. Although many effects reported in the literature are of limited clinical importance, they may be significant when prescribing a drug with a narrow therapeutic index, especially if it is absorbed poorly.

The effect of ondansetron on atracurium-induced neuromuscular blockade

STUDY OBJECTIVE

To determine whether treatment with ondansetron, a new antiemetic drug, affects nondepolarizing neuromuscular blockade.

DESIGN

Randomized, double-blind, prospective study.

SETTING

Operating room at a university medical center.

PATIENTS

30 ASA physical status I and II patients scheduled for elective surgery.

INTERVENTIONS

After the induction of anesthesia with midazolam 2 to 4 mg/kg, sodium thiopental 6 to 8 mg/kg, and fentanyl 4 to 8 micrograms/kg, the ulnar nerve was stimulated at the wrist through subcutaneous needle electrodes at a frequency of 0.15 Hz. The response to stimulation was measured and recorded with a force-displacement transducer applied to the thumb. Patients were randomized to one of three treatment groups. A steady baseline to ulnar nerve stimulation with nitrous oxide-oxygen-opioid-thiopental anesthesia was established. The first study group (Group 1) received a placebo, the second group (Group 2) received 8 mg of ondansetron, and the third group (Group 3) received 16 mg of ondansetron as an intravenous infusion over 5 minutes. Patients were then given incremental doses of atracurium 0.05 mg/kg at 3-minute intervals to establish approximately 95% twitch inhibition so as to construct a dose-response curve. An atracurium infusion was then begun to maintain a constant degree of neuromuscular blockade. At the end of surgery, patients were allowed to recover spontaneously, or pharmacologic antagonism of residual neuromuscular blockade was achieved with neostigmine 0.05 mg/kg and glycopyrrolate 0.01 mg/kg. Mechanomyographic response to train-of-four stimuli (2 Hz for 2 seconds) every 20 seconds was monitored during the atracurium infusion and recovery from neuromuscular blockade.

MEASUREMENTS AND MAIN RESULTS

Log dose-response curves were determined for the study groups and compared using analysis of variance (ANOVA). The 50%, 75%, and 95% effective doses (ED50, ED75, and ED95) were calculated from the equation describing the log dose-response. Maintenance infusion rates were determined, and the neostigmine-accelerated recovery index of 25% to 75% was measured for each group. The results were compared using ANOVA. There were no significant differences among the treatment groups with respect to maintenance infusion rate (7.8 +/- 1.8 micrograms/kg/min for Group 1, 7.7 +/- 2.5 micrograms/kg/min for Group 2, and 7.3 +/- 2.3 micrograms/kg/min for Group 3) or neostigmine-accelerated recovery interval of 25% to 75% (4.5 +/- 2.3 minutes, 4.4 +/- 3.1 minutes, 6.6 +/- 3.9 minutes in Groups 1, 2, and 3, respectively). The log dose-response data for Groups 1, 2, and 3 did not differ significantly (p = 0.068), and the calculated ED95 in each treatment group demonstrated no dose-related change (0.254 +/- 0.022, 0.279 +/- 0.033, and 0.240 +/- 0.022 for Groups 1, 2, and 3, respectively).

CONCLUSIONS

Ondansetron is an antiemetic drug that can be used in the perioperative period without concern for potentiation of nondepolarizing neuromuscular blockade, change in atracurium maintenance dose, or change in rate of neostigmine-induced recovery from neuromuscular blockade with atracurium.