Pharmacotherapy in the critically ill obese patient

Association of Obesity With Sedative Dosing, Sedative Response, and Clinical Outcomes in Mechanically Ventilated Critically Ill Children

OBJECTIVES

This study aimed to investigate the impact of obesity on the use of analgesics and sedatives, rates of iatrogenic withdrawal syndrome (IWS), and outcomes in mechanically ventilated pediatric patients. Additionally, it sought to assess whether a nurse-implemented sedation protocol would be equally effective for children with and without obesity.

DESIGN

Secondary analysis of the Randomized Evaluation of Sedation Titration for Respiratory Failure (RESTORE) pediatric multicenter clinical trial.

SETTING

Thirty-one U.S. PICUs.

PATIENTS

Children 1-17 years old, categorized as with or without obesity according to World Health Organization and Centers for Disease Control and Prevention criteria.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The study assessed various factors including medication exposure, adequacy of pain and sedation management, IWS rates, and clinical outcomes. Obesity occurred in 22% of patients. Obesity did not influence choice of opiate, but it led to extended exposure to these medications. There were no differences in dosing per kilogram of admission weight, resulting in significantly higher daily and cumulative doses in those with obesity. In the protocolized sedation arm, patients with obesity received significantly higher median opiate doses compared with the nonobesity protocolized sedation group. IWS rates did not differ; however, protocolized sedation obesity patients experienced more instances of inadequate sedation, longer time to extubation readiness, longer duration of mechanical ventilation and PICU stay, and higher 28-day in-hospital mortality than the protocolized sedation nonobesity group. These weight-based differences were not noted in the usual care arm.

CONCLUSIONS

This study underscores the significance of accounting for body habitus when selecting and dosing opiates in children with acute respiratory failure. Obesity had substantial impact on medication exposure and clinical outcomes, particularly within a structured, protocolized sedation regimen. Further research is warranted to explore the intricate relationship between medication dosing and clinical outcomes in children with obesity.

Evaluation of clinical outcomes of anidulafungin for the treatment of candidemia in hospitalized critically ill patients with obesity: A multicenter, retrospective cohort study

OBJECTIVES

To evaluate the clinical outcomes of anidulafungin for candidemia treatment in critically ill patients with obesity.

METHODS

A multicenter, retrospective cohort study was conducted in Saudi Arabia for critically ill adults with candidemia who received anidulafungin. Patients with obesity have a body mass index ≥30 kg/m2. The primary outcome was the clinical cure rate.

RESULTS

A total of 146 patients were included, 64 of whom were obese. There were no statistically significant differences in the clinical cure rate (P = 0.63), microbiological cure rate (P = 0.27), or the median time for a clinical cure (P = 0.13) for patients with obesity compared to non-obese patients. The median time for a microbiological cure was longer in non-obese patients than in patients with obesity (P = 0.04). The median hospital length of stay and the median mechanical ventilation durations were numerically longer in patients with obesity.

CONCLUSIONS

Clinical and microbiological cure rates and time for clinical cure were statistically similar for both groups. Considering the study's limitations (especially with a small sample size), it is uncertain if patients with obesity have similar effectiveness to non-obese patients. Future studies with larger sample sizes are warranted to evaluate if obesity negatively impacts anidulafungin's clinical outcomes for candidemia.

Echinocandin exposures in obese patients: A scoping review and clinical perspectives

PURPOSE

Echinocandins are favored drugs for the treatment of fungal infections. There is growing evidence that obese patients treated with echinocandins have lower exposures due to pharmacokinetic (PK) alterations. We conducted a scoping review to characterize, evaluate, and summarize the available evidence on echinocandins exposures in obese patients.

SUMMARY

A comprehensive search of PubMed, Embase, and Cochrane Library for studies on echinocandins published from database inception to October 28, 2022, was conducted using PRISMA-ScR methodology. A total of 25 studies comprising more than 3,174 subjects (8 micafungin studies, 7 caspofungin studies, 9 anidulafungin studies, and 1 rezafungin study) were included in this review. Seventeen studies reported lower echinocandins exposures in overweight and obese individuals compared with normal-weight individuals; the authors of these studies recommended dose adjustments. Conversely, 8 studies did not find significant differences in echinocandin exposure among subjects in varying body weight categories. Clinicians may consider dose adjustments of echinocandins in obese patients; however, there is limited evidence on the ideal dose adjustment strategy to overcome the low echinocandins exposures in obese patients.

CONCLUSION

This scoping review shed light on a growing body of evidence indicating that obese patients have lower echinocandin exposures relative to targeted PK indices, which may lead to negative therapeutic implications. Currently, a lack of high-quality evidence impedes reaching consensus on recommendations for echinocandin dosing adjustment in obese patients. Future research evaluating the optimal echinocandin dosing strategy for obese patients is needed.

Impact of guided weight-based medication dosing in pediatric patients with obesity

BACKGROUND

Obesity is a common disease state within pediatrics, with 19.7% of children in the United States classified as obese. Medication dosing in this population is a challenge not commonly examined in clinical drug trials. Dosing based on total body weight may not always be appropriate; therefore, ideal body weight (IBW) and adjusted body weight (AdjBW) may provide more effective dosing.

OBJECTIVE

The goal was to implement a dosing protocol for pediatric patients with obesity to improve adherence. The primary endpoint was to evaluate adherence to evidence-based dosing recommendations and the secondary endpoints included cost saving analysis for immune globulin and accurate charting of IBW and AdjBW.

METHODS

This was a single center, quality improvement project composed of pre- and post-implementation groups. An IBW and AdjBW calculator were implemented in our electronic health record, as customized enhancements, along with specific weight ordering options. A literature search of pharmacokinetic and pharmacodynamic dosing recommendations based on IBW and AdjBW was conducted. For both groups, patients were included if they were 3-18 years old, had a body mass index greater than or equal to the 95th percentile, and if they received a specified medication.

RESULTS

A total of 618 patients were identified with 24 and 56 patients included for the pre- and post-implementation groups. There were no statistically significant differences in baseline characteristics of the comparator groups. The usage of correct body weight increased from 1.2% to 24.2% after implementation and education (P < 0.001). Cost savings was analyzed for immune globulin with the potential for a net savings of $9423 ± 3626.92.

CONCLUSION

Dosing medications for our pediatric patients with obesity improved with the implementation of calculated dosing weights in the electronic health record, provision of an evidence-based dosing chart, and education of providers.

Utilization of Resources by Patients Who Are Morbid and Super Obese Admitted to a Tertiary Care Center

OBJECTIVES

Data regarding the characteristics of patients who are morbidly and super obese, and the resources they use in nonbariatric hospital settings are limited. The aims of our study were to explore the frequency of inpatient admissions of patients who are morbid (body mass index [BMI] ≥ 40 kg/m) and super obese (BMI ≥ 50 kg/m), their specific characteristics, and to identify their utilization of hospital services and resources, 30-day readmission rates, safe patient handling equipment, and patient clinical outcomes.

METHODS

We conducted a retrospective chart review of adult patients hospitalized at our institution (n = 1670) who are morbidly obese or super obese. We collected and compared data regarding the characteristics of patients, the services and resources used, the use of any special handling equipment, and patient clinical outcomes.

RESULTS

After accounting for confounding variables, wound care and occupational therapy services were more likely to be required for the patients who are super obese (odds ratio [OR] = 1.49, P = 0.04) than for those who are morbidly obese (odds ratio [OR] = 1.36, P = 0.02). Use of safe patient handling devices was twice as likely for the super obese group (OR = 2.09, P < 0.01). There was no difference in mortality rates between the two patient groups (P = 0.81); patients who are super obese had higher odds of prolonged hospital stay by 32% (P = 0.009).

CONCLUSIONS

This study provides an understanding of the characteristics of patients with BMI of 40 kg/m or greater who are admitted to the hospital, the resources and services use, and their clinical outcomes. There is also a need to develop an organizational protocol to ensure safe handling using the right devices and activation of appropriate consult services.

The Association Between Obesity and Risk of Acute Kidney Injury After Cardiac Surgery

OBJECTIVE

To determine the relationship between obesity and the risk of AKI after cardiac surgery (CS-AKI) in a cohort study.

METHODS

A total of 1,601 patients undergoing cardiac surgery were collected and their incidence of CS-AKI was recorded. They were divided into underweight, normal weight, overweight, and obese groups. Logistic regression was used to estimate the association between BMI (body mass index) and CS-AKI risk. Then, a meta-analysis of published cohort studies was conducted to confirm this result using PubMed and Embase databases.

RESULTS

A significant association was observed in this independent cohort after adjusting age, gender, hypertension and New York Heart Association classification (NYHA) class. Compared with normal BMI group (18.5 ≤ BMI < 24.0), the individuals with aberrant BMI level had an increased AKI risk (OR: 1.68, 95% CI: 1.01-2.78) for BMI < 18.5 group and (OR: 1.43, 95% CI: 0.96-2.15) for BMI ≥ 28.0. Interestingly, the U-shape curve showed the CS-AKI risk reduced with the increasing of BMI when BMI ≤ 24.0. As BMI increases with BMI > 24.0, the risk of developing CS-AKI increased significantly. In the confirmed meta-analysis, compared with normal weight, overweight group with cardiac surgery had higher AKI risk (OR: 1.28, 95% CI: 1.16-1.41, P_{heterogeneity} = 0.49). The similar association was found in obesity subgroup (OR: 1.79, 95% CI: 1.57-2.03, P_{heterogeneity} = 0.42).

CONCLUSION

In conclusion, the results suggested that abnormal BMI was a risk factor for CS-AKI independently.

Evaluation of Time to Therapeutic Anticoagulation and Associated Outcomes in Critically Ill, Obese Patients With Pulmonary Embolism Receiving Unfractionated Heparin

BACKGROUND

Delays in time to therapeutic activated partial thromboplastin time (aPTT) have been associated with poor outcomes in patients with acute pulmonary embolism (PE).

OBJECTIVE

To investigate the relationship between time to therapeutic anticoagulation and in-hospital mortality in critically ill, obese patients with acute PE.

METHODS

This study examined 204 critically ill patients with a body mass index (BMI) ≥30 kg/m² receiving unfractionated heparin (UFH) for PE treatment. Patients achieving therapeutic anticoagulation within 24 hours of UFH initiation (early) were compared to those in >24 hours (delayed). Additional end points included 30-day mortality, median time to therapeutic aPTT, proportion of therapeutic and supratherapeutic aPTT values, hemodynamic deterioration, thrombolytic therapy after UFH initiation, length of stay, and bleeding.

RESULTS

No difference in in-hospital or 30-day all-cause mortality was seen (odds ratio [OR]: 1.33, confidence interval [CI]: 0.647-2.72; OR: 1.003, CI: 0.514-1.96). Patients in the early group had a greater proportion of therapeutic aPTT values (66.7% vs 50%, P < .001) and higher percentage of supratherapeutic aPTT values (20.9% vs 11.3%, P < .001); however, no increase in clinically significant bleeding was evident (15.2% vs 10.9%, P = .366).

CONCLUSION

In this population, a shorter time to therapeutic aPTT was not associated with improved survival.

Development and validation of quick Acute Kidney Injury-score (q-AKI) to predict acute kidney injury at admission to a multidisciplinary intensive care unit

AKI is associated with increased risk of death, prolonged length of stay and development of de-novo chronic kidney disease. The aim of our study is the development and validation of prediction models to identify the risk of AKI in ICU patients up to 7 days. We retrospectively recruited 692 consecutive patients admitted to the ICU at San Bortolo Hospital (Vicenza, Italy) from 1 June 2016 to 31 March 2017: 455 patients were treated as the derivation group and 237 as the validation group. Candidate variables were selected based on a literature review and expert opinion. Admission eGFR< 90 ml/min /1.73 mq (OR 2.78; 95% CI 1.78–4.35; p<0.001); SOFAcv ≥ 2 (OR 2.23; 95% CI 1.48–3.37; p<0.001); lactate ≥ 2 mmol/L (OR 1.81; 95% CI 1.19–2.74; p = 0.005) and (TIMP-2)•(IGFBP7) ≥ 0.3 (OR 1.65; 95% CI 1.08–2.52; p = 0.019) were significantly associated with AKI. For the q-AKI score, we stratified patients into different AKI Risk score levels: 0–2; 3–4; 5–6; 7–8 and 9–10. In both cohorts, we observed that the proportion of AKI patients was higher in the higher score levels.

Obesity, acute kidney injury and mortality in patients with sepsis: a cohort analysis

Although the prognostic effect of obesity has been studied in critically ill patients its impact on outcomes of septic patients and its role as a risk factor for acute kidney injury (AKI) is not consensual. We aimed to analyze the impact of obesity on the occurrence of AKI and on in-hospital mortality in a cohort of critically ill septic patients. This study is retrospective including 456 adult patients with sepsis admitted to the Division of Intensive Medicine of the Centro Hospitalar Lisboa Norte (Lisbon, Portugal) between January 2008 and December 2014. Obesity was defined as a body mass index of 30 kg/m² or higher. The Kidney Disease Improving Global Outcomes classification was used to diagnose and classify patients developing AKI. AKI occurred in 87.5% of patients (19.5% with stage 1, 22.6% with stage 2 and 45.4% with stage 3). Obese patients developed AKI more frequently than non-obese patients (92.8% versus 85.5%, p = .035; unadjusted OR 2.2 (95% CI: 1.04–4.6), p = .039; adjusted OR 2.31 (95% CI: 1.07–5.02), p = .034). The percentage of obese patients, however, did not differ between AKI stages (stage 1, 25.1%; stage 2, 28.6%; stage 3, 15.4%; p = .145). There was no association between obesity and mortality (p = .739). Of note, when comparing AKI patients with or without obesity in terms of in-hospital mortality there were also no significant differences between those groups (38.4% versus 38.4%, p = .998). Obesity was associated with the occurrence of AKI in critically ill patients with sepsis; however, it was not associated with in-hospital mortality.

Clinical Outcomes of Weight-Based Norepinephrine Dosing in Underweight and Morbidly Obese Patients: A Propensity-Matched Analysis

BACKGROUND

Weight-based dosing strategy for norepinephrine in septic shock patients with extremes of body mass index has been lesser studied.

METHODS

This historical study of adult septic shock patients was conducted from January 1, 2010, to December 31, 2015, at all intensive care units (ICUs) in Mayo Clinic, Rochester. Patients with documented body mass index were classified into underweight (body mass index <18.5 kg/m²), normal weight (18.5-24.9 kg/m²), and morbidly obese (≥40 kg/m²) patients. Patients with repeat ICU admissions, ICU stay <1 day, and body mass index 25 to 39.9 kg/m² were excluded. The primary outcome was in-hospital mortality, and secondary outcomes included cumulative norepinephrine exposure acute kidney injury, cardiac arrhythmias, and 1-year mortality. Two-tailed P < .05 was considered statistically significant.

RESULTS

From 2010 to 2015, 2016 patients met inclusion-145, 1406, and 466 patients, respectively, in underweight, normal weight, and morbidly obese cohorts. Underweight patients used the highest peak dose and absolute exposure was greatest for morbidly obese patients. In-hospital mortality decreased with increasing log₁₀ body mass index: 41.4% (underweight), 28.4% (normal weight), and 24.7% (morbidly obese), respectively (P < .001); however, this relationship was not noted at 1 year. Unadjusted log₁₀ norepinephrine cumulative exposure (mg) was associated with higher in-hospital mortality, acute kidney injury, cardiac arrhythmias, and 1-year mortality. After adjustment for demographics, body mass index, comorbidity, and illness severity, log₁₀ norepinephrine exposure was an independent predictor of in-hospital mortality (odds ratio 2.4 [95% confidence interval, 2.0-2.8]; P < .001) and 1-year mortality (odds ratio 1.7 [95% confidence interval, 1.5-2.0]; P < .001). In a propensity-matched analysis of 1140 patients, log₁₀ norepinephrine was an independent predictor of in-hospital mortality (odds ratio 2.2 [95% confidence interval, 1.8-2.6]; P < .001).

CONCLUSIONS

Morbidly obese patients had lower in-hospital mortality but had higher 1-year mortality compared to normal weight and underweight patients. Cumulative norepinephrine exposure was highest in morbidly obese patients. Total norepinephrine exposure was an independent mortality predictor in septic shock.

Appropriate Antibiotic Therapy

Prescribing antibiotics is an essential component of initial therapy in sepsis. Early antibiotics are an important component of therapy, but speed of administration should not overshadow the patient-specific characteristics that determine the optimal breadth of antimicrobial therapy. Cultures should be drawn before antibiotic therapy if it does not significantly delay administration. Combination antibiotic therapy against gram-negative infections is not routinely required, and combination therapy involving vancomycin and piperacillin/tazobactam is associated with an increase in acute kidney injury. Emergency practitioners should be aware of special considerations in the administration and dosing of antibiotics in order to deliver optimal care to septic patients.

Impact of Norepinephrine Weight-Based Dosing Compared With Non–Weight-Based Dosing in Achieving Time to Goal Mean Arterial Pressure in Obese Patients With Septic Shock

Background: Currently, a lack of standardization exists in norepinephrine dosing units, the first-line vasopressor for septic shock. Timely achievement of goal mean arterial pressure (MAP) is dependent on optimal vasopressor dosing. Objective: To determine if weight-based dosing (WBD) of norepinephrine leads to earlier time to goal MAP compared with non-WBD in obese patients with septic shock. Methods: This was a retrospective, multicenter cohort study. Patients had a body mass index (BMI) ≥30 kg/m2 and received norepinephrine for septic shock with either a non-WBD strategy (between December 2009 and January 2013) or WBD strategy (between January 2013 and December 2015). The primary outcome was time to goal MAP. Secondary outcomes were norepinephrine duration, dose requirements, and development of treatment-related complications. Results: A total of 287 patients were included (WBD 144; non-WBD 143). There was no difference in median time to goal MAP (WBD 58 minutes, interquartile range [IQR] = 16.8-118.5, vs non-WBD 60 minutes, IQR = 17.5-193.5; P = 0.28). However, there was a difference in median cumulative norepinephrine dose (WBD 12.6 mg, IQR = 4.9-45.9, vs non-WBD 10.5 mg, IQR = 3.9-25.6; P = 0.04) and time to norepinephrine discontinuation (WBD 33 hours, IQR = 15-69, vs non-WBD 27 hours, IQR = 12-51; P = 0.03). There was no difference in rates of atrial fibrillation (WBD 15.3% vs non-WBD 23.7%; P = 0.07) or mortality (WBD 23.6% vs non-WBD 23.1%; P = 0.92). Conclusion: WBD of norepinephrine does not achieve time to goal MAP earlier in obese patients with septic shock. However, WBD may lead to higher norepinephrine cumulative dose requirements and prolonged time until norepinephrine discontinuation.

Biochemical characterization of a factor X activator protein purified from Walterinnesia aegyptia venom

Factor X of blood coagulation cascade can be activated by both intrinsic and extrinsic activating complex, trypsin and some kind of snake venom. A factor X activator protein is reported in Elapidae snake venom. The aim of this study was to evaluate biochemical properties of factor X activator protein because of its prospective application in biochemical research and therapeutics. Crude venom was fractionated on a HPLC system Gold 126/1667 using a combination of Protein PAK 125 and Protein PAK 60 Columns. Molecular weight was determined using SDS-PAGE. Walterinnesia aegyptia venom was fractionated into several protein peaks, but procoagulant and factor X activation activity coexisted into peak no.6. It appeared as single band on native PAGE and molecular weight was 60,000 ± 3. Purified up to 37-fold over crude venom. It shortened recalcification time, effect was dose-dependent and strictly Ca(2++)-dependent. Factor X activator seems to be able to activate factor X specifically because it showed no activation activity on human prothrombin, plasminogen, or protein C. It did not hydrolyze factor Xa substrate S-2222, thrombin substrate S-2238, plasmin substrate S-2251 or S-2302 and kalikrein substrate S-2266. It did not hydrolyze synthetic ester benzoyl arginine ethyl ester. Procoagulant activity was completely inhibited by irreversible serine protease inhibitors phenylmethylsulphonyl fluoride and N-p-tosylphenylalanine chloromethyl ketone. This study illustrates that factor X activator from W. aegyptia is though different in many aspects from factor X activators of Viperidae and Crotalidae venoms, but shows several properties identical to factor X activators from Elapidae venoms.

Cefoxitin Plasma and Subcutaneous Adipose Tissue Concentration in Patients Undergoing Sleeve Gastrectomy

PURPOSE

Antibiotic dosing in obese surgical patients has not been adequately evaluated. The objective of this study was to identify whether currently prescribed doses of cefoxitin achieve adequate and sustained plasma and tissue concentrations in obese patients undergoing sleeve gastrectomy.

METHODS

A prospective evaluation of plasma and tissue cefoxitin concentrations in patients undergoing sleeve gastrectomy was performed. On the day of the surgical procedure, venous blood samples (5 mL) were collected just before cefoxitin administration and then at 5, 30, 60, 120, and 240 minutes after dose administration. In addition, subcutaneous adipose tissue was collected from the surgical site at the time of surgical incision and at closure. Cefoxitin concentrations in the collected samples were quantified by using an HPLC-ultraviolet method. A standard noncompartmental analysis was performed for each individual cefoxitin plasma concentration-time profile. In addition, the ratio of tissue to plasma concentration was calculated for all patients.

FINDINGS

Plasma and tissue pharmacokinetics of cefoxitin were evaluated in 6 patients undergoing sleeve gastrectomy. The mean age and BMI were 48.7 (6.2) years and 42.8 (7.1) kg/m(2), respectively. At the time of surgical closure, subcutaneous adipose tissue concentrations of cefoxitin were subtherapeutic (<8 µg/mL) in all evaluated patients.

IMPLICATIONS

Current dosing strategies for cefoxitin in obese surgical patients may be inadequate, and there is an urgent need to define the appropriate dosage.

Pharmacokinetic considerations for drugs administered in the critically ill

Significant physiological changes are common among critically ill patients. This case-based review describes the consequences of these changes on the selection and dosing of medications.

Physiological and management implications of obesity in critical illness

Obesity is highly prevalent in the United States and is becoming increasingly common worldwide. The anatomic and physiological changes that occur in obese individuals may have an impact across the spectrum of critical illness. Obese patients may be more susceptible to hypoxemia and hypercapnia. During mechanical ventilation, elevated end-expiratory pressures may be required to improve lung compliance and to prevent ventilation-perfusion mismatch due to distal airway collapse. Several studies have shown an increased risk of organ dysfunction such as the acute respiratory distress syndrome and acute kidney injury in obese patients. Predisposition to ventricular hypertrophy and increases in blood volume should be considered in fluid management decisions. Obese patients have accelerated muscle losses in critical illness, making nutrition essential, although the optimal predictive equation to estimate nutritional needs or formulation for obese patients is not well established. Many common intensive care unit medications are not well studied in obese patients, necessitating understanding of pharmacokinetic concepts and consultation with pharmacists. Obesity is associated with higher risk of deep venous thrombosis and catheter-associated bloodstream infections, likely related to greater average catheter dwell times. Logistical issues such as blood pressure cuff sizing, ultrasound assistance for procedures, diminished quality of some imaging modalities, and capabilities of hospital equipment such as beds and lifts are important considerations. Despite the physiological alterations and logistical challenges involved, it is not clear whether obesity has an effect on mortality or long-term outcomes from critical illness. Effects may vary by type of critical illness, obesity severity, and obesity-associated comorbidities.

Unfractionated heparin dosing for therapeutic anticoagulation in critically ill obese adults

PURPOSE

Research evaluating unfractionated heparin (UFH) dosing in obese critically ill populations is limited. This study aimed to determine optimal weight-based and total therapeutic infusion rates of UFH in this population.

METHODS

This retrospective cohort study compared adults on UFH infusions in intensive care units from May 2011 through October 2013 across 3 weight strata: 95 to 104 kg (control), 105 to 129 kg (high weight), and greater than or equal to 130 kg (higher weight). Primary outcomes included total and weight-based infusion rates for therapeutic anticoagulation.

RESULTS

To achieve therapeutic activated partial thromboplastin times, higher weight patients had higher mean infusion rates compared with control (2017 vs 1582 U/h; P = .002). Mean weight-based therapeutic infusion rate was lower in the higher weight group compared with control (13.1 vs 15.8 U kg(-1) h(-1); P = .008). Post hoc analyses indicated mean weight-based infusion rate to achieve therapeutic anticoagulation was 15 U kg(-1) h(-1) in patients less than 165 kg and 13 U kg(-1) h(-1) in patients greater than 165 kg.

CONCLUSIONS

Patients greater than or equal to 130 kg have lower weight-based heparin requirements compared with patients 95 to 104 kg. This difference appears to be driven by patients greater than 165 kg. Patients greater than 165 kg have lower weight-based heparin requirements, whereas patients from 105 to 164 kg have weight-based requirements similar to a normal-weight patient population. Initiating heparin at appropriate weight-based doses for obese patients may optimize anticoagulation.

Antibiotic dosing in obesity: the search for optimum dosing strategies

Global obesity has nearly doubled and is now a common occurrence in high-income and developing countries. The World Health Organization estimates that more than 1.4 billion adults are obese. Although the prevalence of obesity is increasing over the last decades, pharmacokinetic evaluations are still conducted in individuals with a body weight of approximately 70 kg. Morbid obesity is associated with several pathophysiological changes that can profoundly affect drug distribution and clearance. There are currently no specific dosing recommendations for antibiotics in obese patients, making dosing suggestions primarily based on pharmacokinetic characteristics of the medications and dosing recommendations in other disease states. Understanding of the pharmacokinetic alterations and maximum doses of antibiotics safely used is paramount to appropriate treatment in the obese population.

Pharmacokinetic changes and dosing modification of aminoglycosides in critically ill obese patients: a literature review

The objective of the paper is to review the literature and provide recommendations for use of aminoglycoside antibiotics in critically ill obese patients. Literature search in PubMed for all articles on the use of aminoglycosides in critically ill obese patients was conducted, and all articles related to pharmacokinetics in obesity were reviewed. Bibliographies of all searched manuscripts were also reviewed in an attempt to find additional references. Although aminoglycoside pharmacokinetics have been described in detail, data on aminoglycoside use and appropriate dose modification in critically ill obese patients are very limited. Knowledge on aminoglycoside pharmacokinetics and use in critically ill obese patients is incomplete. Pathophysiologic changes in obesity can result in sub- or supra-therapeutic aminoglycoside plasma concentrations, especially in the presence of sepsis. Rigorous clinical studies are needed to establish aminoglycoside dosing guidelines in critically ill obese patients with sepsis.

Comparison of heparin dosing based on actual body weight in non-obese, obese and morbidly obese critically ill patients

Background:

Obesity is endemic in the United States and obese patients are at increased risk of thromboembolism but little data are available for dosing unfractionated heparin (UFH). We evaluated the relationship between obesity and UFH efficacy during critical illness by examining UFH infusions in non-obese, obese, and morbidly obese critically ill patients.

Materials and Methods:

Retrospective review of UFH infusions in non-obese, obese, and morbidly obese critically ill patients. Heparin was initiated without a bolus at 16 units/kg/h or 12 units/kg/h in obese and morbidly obese patients. Demographics, UFH dosage/therapy duration, laboratory values, and bleeding events were reviewed for patients receiving UFH for >24 h. Steady state (SS) was defined as the dosage that resulted in three consecutive activated partial thromboplastin times (aPTT) within target range.

Results:

Sixty-two patients were analyzed including 21 non-obese (mean body mass index (BMI) 24.2 ± 2.3); 21 obese (BMI 34.1 ± 3.1); and 20 morbidly obese (mean BMI 55.3 ± 13.7). Patients had otherwise similar demographics. Although 92% had at least one therapeutic aPTT, only 55% of patients reached SS. Six patients developed minor bleeding, but no major hemorrhagic complications. The dosing of heparin based on actual body weight (units/kg/h) and time to first therapeutic aPTT was similar between groups, but dose was statistically higher at steady state in the non-obese (16.3 ± 5.3 non-obese, 11.6 ± 5.5 obese and 11.1 ± 1.2 obese, P = 0.01) with similar times to steady state.

Conclusions:

Dosing of UFH in morbidly obese and obese critically ill patients based on actual body weight and a reduced initial dose was associated with similar time to first therapeutic aPTT and steady state.

Subtherapeutic linezolid concentrations in a patient with morbid obesity and methicillin-resistant Staphylococcus aureus pneumonia: case report and review of the literature

OBJECTIVE

To report a case of subtherapeutic linezolid concentrations in a patient with morbid obesity.

CASE SUMMARY

A 34-year-old male with morbid obesity (265 kg, body mass index 82 kg/m(2)) was admitted for severe sepsis due to respiratory failure requiring emergent intubation and treatment of community-acquired pneumonia. Admission tracheal aspirate culture revealed methicillin-resistant Staphylococcus aureus (MRSA) for which vancomycin was prescribed. Therapy subsequently was changed to linezolid, because the patient's clinical status worsened, with significant hypoxia (partial pressure of arterial oxygen/fraction of inspired oxygen [PaO2/FiO2] ratio 145), increasing leukocytosis (white blood cell count from 10,800/μL on admission to 15,400/μL on hospital day 6), and persistent fever (38.3 °C). After 48 hours of linezolid monotherapy, the patient remained febrile with continued leukocytosis, worsening hypoxemia, and a persistently positive MRSA culture from a repeat endotracheal aspirate. Linezolid serum concentrations were obtained and vancomycin was reinstituted, after which the patient began to improve (afebrile, improving PaO2/FiO2 ratio, decreasing leukocytosis). On hospital day 12, the patient removed his endotracheal tube, and a sputum sample was obtained for culture. The patient's clinical status subsequently declined, prompting addition of cefepime to his antibiotic regimen. This sputum culture revealed not only MRSA, but also quinolone-resistant Escherichia coli. After completing treatment for both organisms the patient was discharged home.

DISCUSSION

Limited data on linezolid dosing in the morbidly obese population show lower serum drug concentrations than those in nonobese patients, but no clinical failure has been reported when treating MRSA skin and soft tissue infections or MRSA tracheitis. In our patient, low steady-state linezolid serum concentrations (peak 4.13 μg/mL [reference 15-27] and trough 1.27 μg/mL [reference 2-9]) were thought to contribute to his poor clinical response.

CONCLUSIONS

To our knowledge, this is the first report of subtherapeutic linezolid concentrations correlated with decreased clinical effectiveness when during treatment of MRSA pneumonia in a patient with morbid obesity.