Clinical pharmacology of the neuromuscular blocking agents

Evaluation of the three different doses of cisatracurium during general anaesthesia: A prospective randomized study

Background and Aims

The present study was conducted to determine the optimal dose of cisatracurium for intubating conditions and onset and offset of neuromuscular blockade. Data in Indian population are scarce, and hence, the present study was planned to evaluate different doses of cisatracurium.

Material and Methods

The prospective randomized double-blind study was conducted on 180 patients of either sex in the age group of 20-60 yrs., having physical status class I to III, scheduled for surgery under general anesthesia. After exclusion 154 patients were randomly divided into three groups comprising 52, 51, and 51, respectively, in Group A, Group B, and group C. They received 0.1 mgkg-1, 0.2 mgkg-1, and 0.3 mgkg-1 of cisatracurium, respectively, to facilitate endotracheal intubation. Time of onset, intubating conditions, hemodynamic parameters, signs of histamine release, and recovery time were noted.

Results

Mean time to onset was maximum in group A (4.37 ± 0.48 minutes) and minimum in group C (2.33 ± 0.43 minutes). Intubating conditions were found excellent in 88% patients in group. Change in HR was found to be non-significant at all time periods, but decrease in MAP was found between 2 and 10 minutes in group C. Duration of action was longest in group C.

Conclusion

We conclude that cisatracurium in dose of 0.2 mgkg-1 and 0.3 mgkg-1 provides good-to-excellent intubating conditions within less than 3 minutes.

Phonomyography on Perioperative Neuromuscular Monitoring: An Overview

Complications related to neuromuscular blockade (NMB) could occur during anesthesia induction, maintenance, and emergency. It is recommended that neuromuscular monitoring techniques be utilized perioperatively to avoid adverse outcomes. However, current neuromuscular monitoring methods possess different shortcomings. They are cumbersome to use, susceptible to disturbances, and have limited alternative monitoring sites. Phonomyography (PMG) monitoring based on the acoustic signals yielded by skeletal muscle contraction is emerging as an interesting and innovative method. This technique is characterized by its convenience, stable signal quality, and multimuscle recording ability and shows great potential in the application field. This review summarizes the progression of PMG on perioperative neuromuscular monitoring chronologically and presents the merits, demerits, and challenges of PMG-based equipment, aiming at underscoring the potential of PMG-based apparatuses for neuromuscular monitoring.

Effects of neuromuscular blocking agents on the clinical performance of i-gel® and surgical condition in elderly patients undergoing hand surgery: a prospective randomized controlled trial

Background: The effects of neuromuscular blocking agents on the clinical performance of supraglottic airway devices and surgical condition in elderly patients undergoing hand surgery have not been established. We evaluated the effects of rocuronium on the clinical performance of an i-gel^® supraglottic device and surgical condition in elderly patients undergoing orthopedic hand surgery. Methods: Patients aged 65-85 years were randomized to receive either rocuronium (rocuronium group) or saline (control group). We compared the rates of successful insertion of the i-gel on the first attempt as a primary outcome and also assessed the adequacy of i-gel maintenance during controlled ventilation, anesthetic requirement, surgical condition, and recovery time. Results: The rates of successful insertion of the i-gel on a first attempt were 93.1% in the rocuronium group versus 82.1% in the control group (P = 0.423). Peak inspiratory pressure (PIP) was lower in the rocuronium group than in the control group (15.2 vs. 17.9 cmH₂O, respectively, P = 0.028). Spontaneous breathing was less common in the rocuronium group (24.1% vs. 57.1%, respectively, P = 0.011). The requirement of additional fentanyl to suppress spontaneous breathing or patient movement was less in the rocuronium group than in the control group (24.1% vs. 50.0%, respectively, P = 0.043). Surgical condition did not differ between the two groups. Recovery time was shorter in the rocuronium group than in the control group (8.4 vs. 9.9 min, respectively, P = 0.030). Conclusions: Rocuronium did not enhance the success rate of inserting the i-gel^® or the surgical condition in elderly patients. However, using rocuronium reduced PIP, the frequency of spontaneous breathing, the requirement for additional fentanyl and patients' recovery time.

Evaluation of pain scoring and free cortisol levels of postoperative analgesic methods in cardiac surgery: A new perspective

Background

This study aims to evaluate the most appropriate analgesic method of minimizing postoperative pain to prevent complications in patients scheduled for cardiac surgery.

Methods

Between January 2016 and June 2016, a total of 60 patients with the American Society of Anesthesiologists Physical Status Class III (27 males, 33 females; mean age 63 years; range, 49 to 77 years) with an ejection fraction of above 50% who underwent elective coronary artery bypass grafting were included. The patients were divided into two groups following admission to the intensive care unit. Group 1 (n=30) was administered intravenous fentanyl citrate with patient-controlled analgesia protocol, while Group 2 (n=30) was administered 0.1% bupivacaine hydrochloride analgesia protocol with catheter placed between the sternum and subcutaneous tissue.

Results

In Group 1, pain intensity scores at two h and visual analog scale scores except at 24, 36, and 48 h were higher than Group 2 (p<0.05). The length of intensive care unit stay and urine cortisol levels were higher in Group 1 than Group 2 (78±12 h and 631±505 ?g at 24 h vs. 66±13 h and 401±297 ?g at 24 h, respectively p<0.05). Partial pressure of oxygen levels at 10 and 16 h during the postoperative intensive care unit stay were lower, while partial pressure of carbon dioxide levels at 24 h was higher in Group 1 than Group 2 (p<0.05).

Conclusion

The bupivacaine protocol is a relatively more useful analgesic method which produces improved results in blood gas analysis by reducing the effects of pain and shortens the length of intensive care unit stay. Low levels of free cortisol also confirm this finding.

Quantitative analysis of motor evoked potentials in the neonatal lamb

Evoking motor potentials are an objective assessment method for neuromotor function, yet this was to our knowledge never done in neonatal lambs. There is neither a method for standardized quantification of motor evoked potentials (MEPs). We first aimed to evaluate the feasibility of MEP recording in neonatal lambs and test its validity. Second we aimed to develop an algorithm for its quantification and test its reliability since manual input is required. We recorded myogenic MEPs after transcranial motor cortex stimulation in 6 lambs aged 1–2 days. MEPs were also measured in one lamb undergoing Neuro-Muscular Blockade (NMB) and another undergoing lumbar spinal cord (SC) transection, both serving as controls. We computed 5 parameters using a custom-made algorithm: motor threshold, latency, area-under-the-curve, peak-to-peak amplitude and duration. Intra- and inter-observer reliability was analyzed. MEPs could be easily recorded, disappearing after NMB and SC transection. The algorithm allowed for analysis, hence physiologic readings of the parameters in all 4 limbs of all lambs were obtained. Our method was shown to have high intra- and inter-observer ( ≥70%) reliability for latency, area-under-the-curve and peak-to-peak amplitude. These results suggest that standardized MEP recording and analysis in neonatal lambs is feasible, and can reliably assess neuromotor function.

Rocuronium is more hepatotoxic than succinylcholine in vitro

BACKGROUND

The development of liver failure is a major problem in critically ill patients. The hepatotoxicity of many drugs, as one important reason for liver failure, is poorly screened for in human models. Rocuronium and succinylcholine are neuromuscular blocking agents used for tracheal intubation and for rapid-sequence induction.

OBJECTIVE

We used an in-vitro test with a permanent cell line and compared rocuronium and succinylcholine for hepatotoxicity.

DESIGN

In-vitro study.

SETTING

A basic science laboratory, University Hospital Rostock, Germany.

MATERIAL/(PATIENTS)

The basic test compound is the permanent human liver cell line HepG2/C3A. In a standardised microtitre plate assay the toxicity of different concentrations of rocuronium, succinylcholine and plasma control was tested.

INTERVENTIONS

After two incubation periods of 3 days, the viability of cells (XTT test, lactate dehydrogenase release and trypan blue staining), micro-albumin synthesis and the cytochrome 1A2 activity (metabolism of ethoxyresorufin) were measured.

MAIN OUTCOME MEASURES

Differences between rocuronium and succinylcholine were assessed using the Kruskal-Wallis one-way test and two-tailed Mann-Whitney U test.

RESULTS

Rocuronium, but not succinylcholine, led to a significant dose-dependent decrease of viability, albumin synthesis and cytochrome 1A2 activity of test cells.

CONCLUSION

An in-vitro test with a cell line showed hepatotoxicity of rocuronium that was dose-dependent. Further studies are needed to investigate the underlying mechanisms of the effects of rocuronium on hepatic cellular integrity.

TRIAL REGISTRATION

Not suitable.

Drug absorption, distribution, metabolism and excretion considerations in critically ill adults

INTRODUCTION

All critically ill patients require medication to treat organ dysfunction. However, the pharmacokinetics of drugs used to treat these patients is complex due to frequent alterations in drug absorption, distribution, metabolism, and excretion (ADME).

AREAS COVERED

This review examines pharmacokinetic aspects of drug administration for adult intensive care unit (ICU) patients. Specifically, the authors examine the ADME changes that occur and which should be considered by clinicians when delivering drug therapy to critically ill patients.

EXPERT OPINION

Dosage pharmacokinetics determined from single-dose or limited-duration administration studies in healthy volunteers may not apply to critically ill patients. Organ dysfunction among these patients may be due to pre-existing disease or the effects of a systemic or locoregional inflammatory response precipitated by their illness. Alterations in pharmacokinetics observed among the critically ill include altered bioavailability after enteral administration, increased volume of distribution and blood-brain barrier permeability and changes in P-glycoprotein and cytochrome P450 enzyme function. However, the effect of these changes on clinically important outcomes remains uncertain and poorly studied. Future investigations should examine not only pharmacokinetic changes among the critically ill, but also whether recognition of these changes and alterations in drug therapy directed as a consequence of their observation alters patient outcomes.

Rapid tracheal intubation with atracurium: the timing principle

The "Timing Principle" utilises a single bolus of non-depolarising neuromuscular blocking drug followed by thiopentone given at the onset of clinical weakness. The purpose of this study was to compare the intubating conditions after succinylcholine and after atracurium used according to the "timing principle." Eighty patients were randomly assigned to four groups of 20. Three study groups were given atracurium 0.5, 0.75 or 1 mg.kg-1 (Groups I, II and III respectively) and the control group (Group IV) received succinylcholine 1.5 mg.kg-1. The study groups received fentanyl 1 microgram.kg-1, atracurium three minutes later, followed by thiopentone 4-6 mg.kg-1 at the onset of ptosis. The control group had a defasciculating dose of atracurium (0.025 mg.kg-1) and fentanyl (1 microgram.kg-1) followed by thiopentone (4-6 mg.kg-1) and succinylcholine three minutes later. The trachea was intubated one minute after thiopentone was given. The intubating conditions were then graded by a laryngoscopist who was unaware of the induction sequence. All patients were interviewed on the day after surgery. Intubation scores of patients in Group I were worse than in Groups II, III and IV (P < 0.005) but there were no differences between Groups II, III and IV. The technique was not associated with severe haemodynamic changes. All patients, except one were able to cough well after administration of atracurium, before induction of anaesthesia with thiopentone. Patients were generally satisfied with this method of induction. It is concluded that atracurium, when used according to the timing principle, can be an alternative to succinylcholine during rapid-sequence induction.