Pharmacokinetics of rocuronium bromide in obese female patients

Effects of a single dose of rocuronium in patients with different body fat percentages: A randomised controlled trial

The pharmacodynamics in patients with high body fat percentage might be similar to those in obese patients. This randomised controlled clinical trial observed the effects of rocuronium in patients with different percent body fats (PBFs). Fifty-four patients who underwent elective urological or pelvic surgery under general anaesthesia at Shanghai General Hospital were included in the present study; 51 patients were included for data analysis. Patients with normal PBF (<25%) were given a single dose of rocuronium calculated based on total body weight (N-TBW, control group). Patients with a higher PBF (≥25%) were given a single dose of rocuronium calculated based on total body weight (H-TBW). Patients with higher PBF and rocuronium were dosed based on fat-free mass (H-FFM). A train of four (TOF)-Watch acceleromyography monitor was used to measure the effects of the rocuronium. H-TBW (91.9 ± 28.8 s) had significantly shorter onset time than N-TBW and H-FFM (p = 0.003). H-TBW had significantly longer clinical duration time and pharmacological duration time than the other groups (p = 0.000 and 0.000, respectively); the TOF ratio0.25-0.9 time was significantly different among the three groups (p = 0.005). There were no significant differences in the recovery time (p = 0.103) or recovery index (p = 0.159) among the three groups. The effects of rocuronium dosed based on FFM in patients with high PBFs are similar to those in normal patients. A single dose of rocuronium calculated based on TBW might shorten the onset time, prolong the clinical and pharmacological duration times, and prolong the recovery time.

Child and Adolescent Bariatric Surgery in an Urban Tertiary Center: Special Anesthetic Considerations for Obesity

Children and adolescents with obesity who present for weight loss surgery are a unique subset of patients. A thorough understanding of the perioperative needs of these individuals is essential to avoid deleterious complications. This review illustrates the necessity for specialized care, including the continued need of specified drug dosing and a systematic approach in the management of the pediatric bariatric patient.

A review on the anesthetic management of obese patients undergoing surgery

There has been an observed increase in theprevalence of obesity over the past few decades. The prevalence of anesthesiology related complications is also observed more frequently in obese patients as compared to patients that are not obese. Due to the increased complications that accompany obesity, obese patients are now more often requiring surgical interventions. Therefore, it is important that anesthesiologists be aware of this development and is equipped to manage these patients effectively and appropriately. As a result, this review highlights the effective management of obese patients undergoing surgery focusing on the preoperative, perioperative and postoperative care of these patients.

The Real-Time and Patient-Specific Prediction for Duration and Recovery Profile of Cisatracurium Based on Deep Learning Models

During general anesthesia, how to judge the patient’s muscle relaxation state has always been one of the most significant issues for anesthesiologists. Train-of-four ratio (TOFR) monitoring is a standard method, which can only obtain static data to judge the current situation of muscle relaxation. Cisatracurium is a nondepolarizing benzylisoquinoline muscle relaxant. Real-time prediction of TOFR could help anesthesiologists to evaluate the duration and recovery profile of cisatracurium. TOFR of cisatracurium could be regarded as temporal sequence data, which could be processed and predicted using RNN based deep learning methods. In this work, we performed RNN, GRU, and LSTM models for TOFR prediction. We used transfer learning based on patient similarity derived from BMI and age to achieve real-time and patient-specific prediction. The GRU model achieved the best performance. In transfer learning, the model chosen based on patient similarity has significantly outperformed the model chosen randomly. Our work verified the feasibility of real-time prediction for TOFR of cisatracurium, which had practical significance in general anesthesia. Meanwhile, using the patient demographic data in transfer learning, our work could also achieve the patient-specific prediction, having theoretical value for the clinical research of precision medicine.

Dosing of neuromuscular blocking agents in patients with obesity: A narrative review

There is no consensus on which weight clinicians should use for weight-based dosing of neuromuscular blocking agents (NMBAs), as exemplified by differing or absent recommendations in clinical practice guidelines. The purpose of this paper is to review studies that evaluated various size descriptors for weight-based dosing of succinylcholine and non-depolarising NMBAs, and to provide recommendations for the descriptors of choice for the weight-based dosing of these agents in patients with obesity. All of the studies conducted to date involving depolarising and non-depolarising NMBAs in patients with obesity have assessed single doses or short-term infusions conducted in perioperative settings. Recognising that any final dosing regimen must take into account patient-specific considerations, the available evidence suggests that actual body weight is the size descriptor of choice for weight-based dosing of succinylcholine and that ideal body weight, or an adjusted (or lean) body weight, is the size descriptor of choice for weight-based dosing of non-depolarising NMBAs.

Anesthetic management of a morbidly obese patient with endometrial cancer during robot-assisted laparoscopic surgery

Background

The number of robot-assisted surgeries being performed has increased in recent years, even in patients with risk factors, such as obesity, owing to advancements in medical technologies. We here report the anesthetic management of a morbidly obese woman who underwent robot-assisted surgery.

Case presentation

A 44-year-old woman (height, 165 cm; weight, 147 kg; body mass index, 54 kg/m²) was scheduled to undergo robot-assisted laparoscopic hysterectomy for endometrial cancer. Preoperative weight loss and rehearsal of positioning during induction of anesthesia and surgical procedures greatly contributed to the surgical success. Monitoring of oxygen reserve index in combination with SpO₂ was useful for appropriate airway and respiratory management. During anesthesia induction, the ramp position using a special commercially available cushion facilitated manual mask ventilation and tracheal intubation. Lung-protective ventilation using a limited tidal volume with moderate PEEP was applied during the robot-assisted surgical procedure.

Conclusion

We successfully managed anesthesia without any complications.

Relationship between the muscle relaxation effect and body muscle mass measured using bioelectrical impedance analysis: A nonrandomized controlled trial

Objective

The dose of neuromuscular blocking drugs is commonly based on body weight, but using muscle mass might be more effective. This study investigated the relationship between the effect of neuromuscular blocking drugs and muscle mass measured using bioelectrical impedance analysis.

Methods

Patients who were scheduled for elective surgery using a muscle relaxant were screened for inclusion in this study. Under intravenous anaesthesia, 12 mg or 9 mg of rocuronium was administered to males and females, respectively; and the maximal relaxation effect of T1 was measured using a TOF-Watch-SX® acceleromyograph.

Results

This study enrolled 40 patients; 20 males and 20 females. For both sexes, the maximal relaxation effect of T1 did not correlate with the body weight-based dose of neuromuscular blocking drugs (males, r² = 0.12; females, r² = 0.26). Instead, it correlated with the dose based on bioelectrical impedance analysis-measured muscle mass when injected with the same dose of rocuronium (males, r² = 0.78, female, r² = 0.82).

Conclusions

This study showed that the muscle relaxation effect of rocuronium was correlated with muscle mass and did not correlate with body weight when using the same dose. Therefore, a muscle mass-based dose of neuromuscular blocking drugs is recommended.

Fiberoptic intubation of severely obese patients through supraglottic airway: A prospective, randomized trial of the Ambu® AuraGain™ laryngeal mask vs the i-gel™ airway

INTRODUCTION

Airway management in severely obese patients remains a challenging issue for anaesthetists and may lead to life-threatening situations. Supraglottic airway devices, such as the i-gel™ or the AuraGain™, were developed, with the possibility to ventilate the patient or use them as a conduit for endotracheal intubation.

METHODS

In our randomized prospective trial, we hypothesized a 10 seconds faster fiberoptic trans-device intubation time through the AuraGain™ laryngeal mask compared to the i-gel™ laryngeal mask in severely obese patients. We randomly assigned 44 patients to the AuraGain or i-gel group and measured trans-device intubation time after 5 minutes of successful ventilation through the device. Secondary parameters relating to the trans-device intubation success, oropharyngeal leak pressure, and parameters regarding insertion of the supraglottic airway devices were measured. Postoperative airway morbidity was determined 5 hours after surgery.

RESULTS

Mean (SD) intubation time was 55.7 (5.8) seconds for the AuraGain™ vs 54.1 (8.5) for i-gel™ mask (95% CI -2.7 to 5.9; P = 0.474), respectively, on a mean body mass index (BMI) of 39.4 kg/m² in the AuraGain™ group vs 38.9 kg/m² in i-gel™ group. No difference could be found in the other studied parameters.

CONCLUSIONS

Time for intubation through both supraglottic airway devices was similar. Attributed to fast possibility of securing the airway with both supraglottic airway devices, we believe that both, AuraGain™ and i-gel™, can be a good alternative in the airway management in obese patients.

Perioperative Pharmacologic Considerations in Obesity

Obesity has increased in incidence worldwide. Along with the increased number of obese patients, comorbid conditions are also more prevalent in this population. Obesity leads to changes in the physiology of patients along with an altered response to pharmacologic therapy. Vigilant perioperative physicians must be aware of the unique characteristics of administered agents in order to appropriately provide anesthetic care for obese patients. Because of the variability in tissue content in obese patients and changes in pharmacokinetic modeling, a one-size-fits-all approach is not justified and a more sophisticated and prudent approach is indicated.

Gaps in Drug Dosing for Obese Children: A Systematic Review of Commonly Prescribed Emergency Care Medications

PURPOSE

Approximately 1 of 6 children in the United States is obese. This has important implications for drug dosing and safety because pharmacokinetic (PK) changes are known to occur in obesity due to altered body composition and physiologic mechanisms. Inappropriate drug dosing in an emergency setting can limit therapeutic efficacy and increase drug-related toxic effects for obese children. Few systematic reviews examining PK properties and drug dosing in obese children have been performed.

METHODS

We identified 25 emergency care drugs from the Strategic National Stockpile and Acute Care Supportive Drugs List and performed a systematic review for each drug in 3 study populations: obese children (2-18 years of age), normal weight children, and obese adults (aged >18 years). For each study population, we first reviewed a drug's Food and Drug Administration label and then performed a systematic literature review. From the literature, we extracted drug PK data, biochemical properties, and dosing information. We then reviewed data in 3 age subpopulations (2-7 years, 8-12 years, and 13-18 years) for obese and normal weight children and by route of drug administration (intramuscular, intravenous, oral, and inhaled). If sufficient PK data were not available by age and route of administration, a data gap was identified.

FINDINGS

Only 2 of 25 emergency care drugs (8%) contained dosing information on the Food and Drug Administration label for obese children and adults compared with 22 of 25 (88%) for normal weight children. We found no sufficient PK data in the literature for any of the emergency care drugs in obese children. Sufficient PK data were found for 7 of 25 emergency care drugs (28%) in normal weight children and 3 of 25 (12%) in obese adults.

IMPLICATIONS

Insufficient information exists to guide dosing in obese children for any of the emergency care drugs reviewed. This knowledge gap is alarming, given the known PK changes that occur in the setting of obesity. Future clinical trials examining the PK properties of emergency care medications in obese children should be prioritized.

Drug Dosing and Pharmacokinetics in Children With Obesity: A Systematic Review

IMPORTANCE

Obesity affects nearly one-sixth of US children and results in alterations to body composition and physiology that can affect drug disposition, possibly leading to therapeutic failure or toxic side effects. The depth of available literature regarding obesity's effect on drug safety, pharmacokinetics, and dosing in obese children is unknown.

OBJECTIVE

To perform a systematic literature review describing the current evidence of the effect of obesity on drug disposition in children.

EVIDENCE REVIEW

We searched the MEDLINE, Cochrane, and EMBASE databases (January 1, 1970-December 31, 2012) and included studies if they contained data on drug clearance, volume of distribution, or drug concentration in obese children (aged ≤18 years). We compared exposure and weight-normalized volume of distribution and clearance between obese and nonobese children. We explored the association between drug physicochemical properties and clearance and volume of distribution.

FINDINGS

Twenty studies met the inclusion criteria and contained pharmacokinetic data for 21 drugs. The median number of obese children studied per drug was 10 (range, 1-112) and ages ranged from newborn to 29 years (1 study described pharmacokinetics in children and adults together). Dosing schema varied and were either a fixed dose (6 [29%]) or based on body weight (10 [48%]) and body surface area (4 [19%]). Clinically significant pharmacokinetic alterations were observed in obese children for 65% (11 of 17) of the studied drugs. Pharmacokinetic alterations resulted in substantial differences in exposure between obese and nonobese children for 38% (5 of 13) of the drugs. We found no association between drug lipophilicity or Biopharmaceutical Drug Disposition Classification System class and changes in volume of distribution or clearance due to obesity.

CONCLUSIONS AND RELEVANCE

Consensus is lacking on the most appropriate weight-based dosing strategy for obese children. Prospective pharmacokinetic trials in obese children are needed to ensure therapeutic efficacy and enhance drug safety.

Anesthetic Pharmacology and the Morbidly Obese Patient

Anesthesiologists are increasingly being faced with treating obese patients. Physiologic and anthropometric associated with obesity-most notably increases in cardiac output, changes in tissue perfusion and increases in total body weight (TBW), lean body weight (LBW), and fat mass affect the pharmacokinetics (PK) of anesthetic agents. In addition, redundancy of airway tissue, obstructive and central sleep apnea and CO2 retention affect the pharmacodynamics (PD) of anesthetics and narrow the therapeutic window of numerous anesthetic drugs. Safe and effective pharmacologic management of the obese patient requires a thorough understanding of how obesity affects the PK and PD of anesthetics.

Anesthesia for bariatric surgery

BACKGROUND

Bariatric surgery has a lot of problems in anesthesia. We retrospectively compared anesthesia for bariatric surgery in yellow race with that in normal weight patients.

METHODS

Twenty patients who received bariatric surgery and 20 normal body weight patients who received abdominal surgery in Japan were enrolled. Induction condition, depth of epidural space, dose of anesthetics, duration of the effects of muscle relaxants, ventilation, and fluid management in bariatric surgery were analyzed and compared with those in normal body weight patients.

RESULTS

An epidural catheterization was successful under ultrasound guide in the bariatric group. The depth epidural space was significantly larger in the bariatric group. Cormack and Lehane classification and the number of intubation attempt were not different between the two groups, while one bariatric case was once awakened to intubate blindly. Pressure-controlled ventilation was used in the bariatric group. Four bariatric patients were continuously ventilated after surgery. The doses of anesthetics and fluid infusion rate were not different between the two groups when calculated by ideal body weight in the bariatric group. The duration of the effects of rocuronium and pancuronium were shorter in the bariatric group.

CONCLUSIONS

For anesthesia of yellow race patients undergoing bariatric surgery, intravenous anesthetics and acetate Ringer's solution with 1% glucose could be administered per ideal body weight, the effects of muscle relaxants lasted shorter, pressure-controlled ventilation could keep oxygenation with adequate carbon dioxide, and ultrasound assist was useful in epidural catheterization in the bariatric patients.

Anesthesia for a 228-kg patient (body mass index, 90.6) undergoing laparoscopic sleeve gastrectomy

We undertook anesthesia of a 40-year-old woman with body weight of 228 kg and body mass index (BMI) of 90.6 kg/m(2) who was undergoing laparoscopic sleeve gastrectomy. This case may be the largest known patient undergoing general anesthesia in our country. Anesthesia was induced in a 30° head-up position with midazolam, fentanyl, droperidol, and inhalation of sevoflurane and nitrous oxide without muscle relaxants, and maintained with propofol, remifentanil, and pancuronium under pressure-controlled ventilation. The Airway Scope could not be inserted into her mouth, but her trachea was successfully intubated with a Macintosh laryngoscope. Dosages of anesthetics and fluid infusion rate were calculated first per ideal body weight. Then, infusion of propofol and remifentanil and administration of muscle relaxant were controlled by bispectral index, hemodynamics, and train-of-four response, respectively. Postoperative 12-h pressure-controlled ventilation and pain management by subcutaneous infusion of fentanyl and droperidol were successful. Subcutaneous heparin 5,000 units twice per day postoperatively did not induce thromboembolism.

Effect of obesity on the pharmacokinetics of drugs in humans

The prevalence of obesity has dramatically increased in recent years and now includes a significant proportion of the world's children, adolescents and adults. Obesity is linked to a number of co-morbidities, the most prominent being type 2 diabetes mellitus. While many agents are available to treat these conditions, the current knowledge regarding their disposition in the obese remains limited. Over the years, both direct and indirect methodologies have been utilized to assess body composition. Commonly used direct measures include underwater weighing, skinfold measurement, bioelectrical impedance analysis and dual-energy x-ray absorptiometry. Unfortunately, these methods are not readily available to the majority of clinicians. As a result, a number of indirect measures to assess body composition have been developed. Indirect measures rely on patient attributes such as height, bodyweight and sex. These size metrics are often utilized clinically and include body mass index (BMI), body surface area (BSA), ideal bodyweight (IBW), percent IBW, adjusted bodyweight, lean bodyweight (LBW) and predicted normal weight (PNWT). An understanding of how the volume of distribution (V(d)) of a drug changes in the obese is critical, as this parameter determines loading-dose selection. The V(d) of a drug is dependent upon its physiochemical properties, the degree of plasma protein binding and tissue blood flow. Obesity does not appear to have an impact on drug binding to albumin; however, data regarding alpha(1)-acid glycoprotein binding have been contradictory. A reduction in tissue blood flow and alterations in cardiac structure and function have been noted in obese individuals. At the present time, a universal size descriptor to describe the V(d) of all drugs in obese and lean individuals does not exist. Drug clearance (CL) is the primary determinant to consider when designing a maintenance dose regimen. CL is largely controlled by hepatic and renal physiology. In the obese, increases in cytochrome P450 2E1 activity and phase II conjugation activity have been observed. The effects of obesity on renal tubular secretion, tubular reabsorption, and glomerular filtration have not been fully elucidated. As with the V(d), a single, well validated size metric to characterize drug CL in the obese does not currently exist. Therefore, clinicians should apply a weight-normalized maintenance dose, using a size descriptor that corrects for differences in absolute CL between obese and non-obese individuals. The elimination half-life (t((1/2))) of a drug depends on both the V(d) and CL. Since the V(d) and CL are biologically independent entities, changes in the t((1/2)) of a drug in obese individuals can reflect changes in the V(d), the CL, or both. This review also examines recent publications that investigated the disposition of several classes of drugs in the obese--antibacterials, anticoagulants, antidiabetics, anticancer agents and neuromuscular blockers. In conclusion, pharmacokinetic data in obese patients do not exist for the majority of drugs. In situations where such information is available, clinicians should design treatment regimens that account for any significant differences in the CL and V(d) in the obese.

Should dosing of rocuronium in obese patients be based on ideal or corrected body weight?

BACKGROUND

Pharmacokinetic studies in obese patients suggest that dosing of rocuronium should be based on ideal body weight (IBW). This may, however, result in a prolonged onset time or compromised conditions for tracheal intubation. In this study, we compared onset time, conditions for tracheal intubation, and duration of action in obese patients when the intubation dose of rocuronium was based on three different weight corrections.

METHODS

Fifty-one obese patients, with a median (range) body mass index of 44 (34-72) kg/m2, scheduled for laparoscopic gastric banding or gastric bypass under propofol-remifentanil anesthesia were randomized into three groups. The patients received rocuronium (0.6 mg/kg) based on IBW (IBW group, n = 17), IBW plus 20% of excess weight (corrected body weight [CBW]20% group, n = 17), or IBW plus 40% of excess weight (CBW40% group, n = 17). Propofol was administered as a bolus of 200 mg and an infusion at 5 mg x kg(-1) x h(-1) and remifentanil was administered at 1.0 microg x kg(-1) x min(-1), both according to CBW40%. Neuromuscular function was monitored with train-of-four nerve stimulation and acceleromyography. The primary end point was duration of action, defined as time to reappearance of the fourth twitch in train-of-four.

RESULTS

The median (range) duration of action was 32 (18-49), 38 (25-66), and 42 (24-66) min in the IBW, CBW20%, and CBW40% groups, respectively (P = 0.001 for comparison of the IBW and CBW40% group). There were no significant differences in onset time (85 vs 84 vs 80 s) or in intubation conditions 90 s after administration of rocuronium.

CONCLUSIONS

In obese patients undergoing gastric banding or gastric bypass, rocuronium dosed according to IBW provided a shorter duration of action without a significantly prolonged onset time or compromised conditions for tracheal intubation.

[Evaluation of tracheal intubation conditions in morbidly obese patients: a comparison of succinylcholine and rocuronium]

OBJECTIVE

To compare tracheal intubation conditions in morbidly obese patients 60 seconds after administration of succinylcholine or rocuronium doses based on real weight or ideal weight.

METHOD

We evaluated patients with a body mass index (BMI) of 40 kg x m(-2) or more but no other indications of difficult-intubation risk. Induction was performed under fentanyl and propofol at doses calculated based on real weight. Patients were assigned to 1 of 4 groups for tracheal intubation. Group 1 received 1 mg of succinylcholine per kilogram of ideal weight, group 2 received 1 mg of succinylcholine per kilogram of real weight, group 3 received 0.6 mg of rocuronium per kilogram of ideal weight, and group 4 received 0.6 mg of rocuronium per kilogram of real weight. Tracheal intubation was performed 60 seconds later and intubation conditions were recorded using a clinical scoring system.

RESULTS

Eighty patients with a mean BMI of 47.5 kg x m(-2) were enrolled. The difficult intubation rate was 3.75%. All patients were intubated. Laryngoscopy conditions and position and movement of vocal cords were similar in all 4 groups. Reaction to cuff inflation revealed intergroup differences; group 3 presented slight limb movements, diaphragm movement, and sustained cough for more than 10 seconds.

CONCLUSION

These results suggest that administration of succinylcholine calculated based on real weight or ideal weight and rocuronium based on real weight can provide clinically acceptable conditions for tracheal intubation in morbidly obese patients with no other difficult-intubation criteria.

Anesthesia in the obese patient: Pharmacokinetic considerations

The prevalence of obesity has increased 15% up to 20% and represents an important challenge for the anesthesiologist in drug-dosing management. The aim of this work is to provide an overview on physiological changes and pharmacokinetic implications of obesity for the anesthesiologist. Obesity increases both fat and lean masses; however, the percentage of fat tissue increases more than does the lean mass, affecting the apparent volume of distribution of anesthetic drugs according to their lipid solubility. Benzodiazepine loading doses should be adjusted on actual weight, and maintenance doses should be adjusted on ideal body weight. Thiopental sodium and propofol dosages are calculated on total body weight (TBW). The loading dose of lipophilic opioids is based on TBW, whereas maintenance dosages should be cautiously reduced because of the higher sensitivity of the obese patient to their depressant effects. Pharmacokinetic parameters of muscle relaxants are minimally affected by obesity, and their dosage is based on ideal rather than TBW. Inhalation anesthetics with very low lipid solubility, such as sevoflurane and desflurane, allow for quick modification of the anesthetic plan during surgery and rapid emergence at the end of surgery, hence representing very flexible anesthetic drugs for use in this patient population. Drug dosing is generally based on the volume of distribution for the loading dose and on the clearance for maintenance. In the obese patient, the volume of distribution is increased if the drug is distributed both in lean and fat tissues whereas the anesthetic drug clearance is usually normal or increased.

The Effects of Cisatracurium on Morbidly Obese Women

There is conflicting evidence on the duration of action of atracurium in obese patients. Cisatracurium is one of the stereoisomers of atracurium. We investigated the neuromuscular effects of cisatracurium in morbidly obese patients. Twenty obese female patients (body mass index >40) were randomized in two groups. Group I (n = 10) received 0.2 mg/kg of cisatracurium on the basis of real body weight (RBW), whereas in Group II (n = 10) the dose was calculated on ideal body weight (IBW). In a control group of 10 normal weight female patients (body mass index 20-24), the dose of cisatracurium was based on RBW. Neuromuscular transmission was monitored using acceleromyography of the adductor pollicis, and anesthesia was induced and maintained with remifentanil and propofol. Onset time was comparable between Group I and the control group (132 s versus 135 s; P = ns). The duration 25% was longer in Group I than in the control group (74.6 min versus 59.1 min; P = 0.01) and in the control group compared with Group II (45.0 min; P = 0.016). In conclusion, the duration of action of cisatracurium was prolonged in morbidly obese patients when dosed according to RBW compared with a control group of normal weight patients. Duration was also prolonged in the control group patients compared with morbidly obese patients to whom the drug was administered on the basis of IBW.

The Pharmacodynamic Effects of Rocuronium When Dosed According to Real Body Weight or Ideal Body Weight in Morbidly Obese Patients

We investigated the pharmacodynamic effects of rocuronium on morbidly obese patients. Twelve morbidly obese female patients (body mass index >40 kg/m(2)) admitted for laparoscopic gastric banding were randomized into two groups. Group 1 (n = 6) received 0.6 mg/kg of rocuronium based on real body weight, whereas Group 2 (n = 6) received 0.6 mg/kg of rocuronium based on ideal body weight. In a control group of six normal-weight female patients admitted for laparoscopic surgery, rocuronium was dosed on the basis of their real body weight. Neuromuscular transmission was monitored by using acceleromyography of the adductor pollicis; anesthesia was induced and maintained with remifentanil and propofol. The onset time tended to be shorter in Group 1 and the control group compared with Group 2, but this did not achieve statistical significance. Duration of action to 25% of twitch tension was more than double in Group 1 (55 min) compared with the other two groups (22 and 25 min; P < 0.001). Duration of action was similar between Group 2 and control. Recovery index tended to be longer in Group 1, but without a significant difference. In conclusion, in morbidly obese patients, the duration of action of rocuronium is significantly prolonged when it is dosed according to real body weight. Therefore, the dosage should be assessed on the basis of ideal rather than on real body weight in clinical practice.

Resuscitation of the morbidly obese patient

Obesity is a major health care problem in the United States. The body mass index (BMI) is the standard measure of obesity. A BMI >25 kg/m2 is defined as overweight and obesity as a BMI > 30 kg/m2. Recent surveys indicate that 54% of adults, or roughly 97 million people, are overweight. Given the incidence of obesity in the general population, it is likely that EM physicians will be involved in the emergency care of critically ill or injured obese patients. The objective of this article is to present the clinical problems associated with the resuscitation of the critically ill or injured obese patient and their potential solutions.

Dosing of medications in morbidly obese patients in the intensive care unit setting

OBJECTIVE

To derive recommendations for the dosing of commonly used medications in the morbidly obese patient in the ICU.

DATA SOURCES

Articles were obtained through computerized searches involving MEDLINE. The bibliographies of retrieved publications and textbooks were reviewed for additional references.

STUDY SELECTION

All studies involving the pharmacokinetics or pharmacodynamics of medications in obese subjects or patients.

DATA EXTRACTION

The emphasis was on studies involving morbidly obese patients but, in the absence of such data, investigations involving lesser forms of obesity were extracted.

DATA SYNTHESIS

There is a paucity of data upon which to make recommendations for dosing commonly used medications in the morbidly obese patient in the ICU, although recommendations were provided based on the available information.

CONCLUSIONS

There is clearly a need for more investigations involving dosing regimens of medications in the morbidly obese population. Until such studies are available, the clinician must try to derive the best dosing regimens for medications based on the limited pharmacokinetic data available for some agents and clinical judgement.

The relationship between rate of administration of an intubating dose of rocuronium and time to 50% and 90% block at the adductor pollicis muscle

OBJECTIVE

To determine the relationship between the rate of rocuronium injection and the onset time of neuromuscular block.

METHODS

After intravenous induction, 60 female patients (ASA I-II) were assigned randomly into 3 groups for rocuronium administration within 1-15, 15-30 or 30-60 seconds. Acceleromyography of the thumb was performed using train-of-four (TOF) stimulation. Times to 50% and 90% twitch depression of the first twitch of the TOF stimulation (T1) were recorded.

RESULTS

Injection time significantly influences time to 50% relaxation, but not time to 90% relaxation. Body mass index is negatively correlated with time to 50% and 90% relaxation.

CONCLUSIONS

We conclude that rate of injection influences only the initial phase of development of the block and that slower injection times do not significantly affect time to 90% relaxation at the adductor pollicis muscle.