Morbid Obesity: Multi system Considerations for Acute Care

Transcription

1 Morbid Obesity: Multi system Considerations for Acute Care BRENDA ENGLER, MSN, ACNP BC, CCRN GEISINGER MEDICAL CENTER Disclosures None 1

2 Obesity Statistics 30 % of the adult population of Pennsylvania is classified as obese Increased from 20.3 % in 2000 and increased from 13.7 % in 1990 Pennsylvania is among the 25 states in the US with 30 % or greater percentage of the population with obesity Objectives Describe the pathophysiologic effects of morbid obesity on the multiple organ systems of the body List adjustments which must be made for acute care procedures for morbidly obese patients Discuss the changes in pharmacokinetics for multiple drug classes in morbidly obese patients and how to adjust medication orders to obtain appropriate therapeutic effect Definition Obese BMI > 30 Morbidly Obese BMI > 40 or BMI > 35 with comorbidity Super obesity BMI > 50 2

3 Cardiovascular System High incidence of hypertension Increased circulating blood volume Increased cardiac output (Increased stroke volume) Left ventricular hypertrophy and dilation High incidence of pulmonary hypertension Higher risk of heart failure (5 7% increase risk for each 1% increase in BMI) Decreased mortality in acute events Pulmonary System Decreased chest wall and lung compliance Decrease in functional residual capacity and expiratory reserve volume Increased airway resistance Para pharyngeal fat deposition Inflammatory changes to smaller airways due to opening and closing trauma Pulmonary System Obstructive sleep apnea Functional airway collapse during sleep Increases risk of pulmonary hypertension, cardiovascular complications, and metabolic disturbances Obesity hypoventilation syndrome Awake alveolar hypoventilation Increases risk of pulmonary hypertension, cardiovascular complications, and metabolic disturbances 3

4 Gastrointestinal System Increased incidence of GERD Increased baseline intra abdominal pressure and risk for abdominal compartment syndrome Double the incidence of non alcoholic fatty liver disease compared to the general public Increased risk of cholelithiasis with cholesterol stones Endocrine System High incidence of diabetes mellitus, usually related to obesity induced metabolic syndrome Adipose tissue produces adipokines (cytokines and chemokines) Pro inflammatory state Endothelial damage Insulin resistance Check for hypothyroidism Urinary system Higher rate of chronic kidney disease and risk for acute kidney injury Pre renal azotemia and acute tubular necrosis Contrast nephropathy Acute oxalate nephropathy Rhabdomyolysis Intra abdominal hypertension and abdominal compartment syndrome 4

5 Urinary system Calculated glomerular filtration rate (GFR) may not accurately assess renal function Baseline increased GFR and renal plasma flow Higher rate of creatinine production due to body composition Catheter positioning and replacement fluid volume may be challenging if renal replacement therapy needed Hematologic Considerations Double relative risk of deep vein thrombosis and pulmonary embolus in obese patients Mobility issues Ineffective prophylaxis Pro thrombotic effects of adipokines Higher circulating blood volume Acute Care Procedures Airway Management Vascular Procedures Lumbar Puncture 5

6 Airway Management May be more likely to have a difficult airway Thyromental distance Mallampati score Cervical spine extension Interincisor distance Upper lip bite test Neck circumference BMI Airway Management High risk of rapid onset of hypoxemia Pre oxygenation Passive oxygenation Mask ventilation may be difficult due to body habitus and airway obstruction with adipose tissue Back up plan Increased risk of regurgitation and aspiration due to increased intra abdominal pressure Consider gastric decompression 6

7 Vascular Procedures Anatomic concerns Difficulty identifying landmarks Variable anatomy due to adipose tissue Patient preparation Positioning May need increased amount of local anesthesia Higher risk to bend guidewire Insertion depth may need to be 2 cm or more deeper than non obese patient Vascular Procedures Ultrasound guidance suggested Central venous catheters / Peripherally Inserted Central Catheters Arterial catheters Peripheral venous catheters Introducer central venous catheter may be inadequate length to remain in vessel Endovascular cooling catheters may be superior to surface cooling for targeted temperature management after cardiac arrest Vascular Procedures Arterial lines often more accurate than ill fitting non invasive blood pressure cuff measurements Intraosseous access may be challenging depending on the amount of adipose tissue at the insertion site 7

8 Lumbar Puncture Positioning may be challenging If lateral decubitus attempt to get spine horizontal Consider increased amount of local anesthetic Longer needle required for access Ultrasound guidance doubles success rates Pharmacotherapy Most drugs trials include very few morbidly obese patients Some retrospective studies of pharmacokinetics of drugs Drug absorption unchanged unless gastric restrictive or malabsorptive surgery Drug excretion often increased because of baseline increased GFR unless kidney disease present Pharmacotherapy Volume of distribution determines the dosing weight Lipophilic drugs have higher volumes of distribution Drug dosing is usually based on actual or total body weight Hydrophilic drugs have lower volumes of distribution Drug dosing is usually based on either ideal body weight or adjusted body weight Adjusted body weight accounts for the increased blood volume in the blood vessels and discounts the adipose tissue weight 8

9 Anticoagulation Heparin Therapeutic dosing IV infusion via weight based nomogram Monitoring functional heparin assay (anti factor Xa activity) is preferred Anticoagulation Heparin Chemoprophylaxis Dosing 5000 Units subcutaneous Q 8 hours for BMI up to 50 kg/m Units subcutaneous Q 8 hours for BMI greater than 50 kg/m 2 Anticoagulation Enoxaparin dosed by total body weight up to 144 kg or 150 kg Therapeutic dosing 1 mg/kg every 12 hours Monitored goal heparin Xa assay of 0.6 to 1 Units/mL drawn 4 hours after the third or any subsequent dose 9

10 Anticoagulation Enoxaparin dosed by total body weight up to 144 kg No standard for prophylactic dose 40 mg Q 12 hours (generally BMI < 50) 60 mg Q 12 hours (generally BMI > 50) 0.5 mg/kg Daily May consider monitoring heparin Xa assay after the third or subsequent dose with goal of 0.2 to 0.4 Units/mL Anticoagulation Tinzaparin dosed by total body weight up to 165 kg Dalteparin dosed by total body weight up to 190 kg Fondaparinux Prophylaxis dose of 2.5 mg daily with no adjustment for weight Treatment dose is increased from 7.5 mg daily to 10 mg daily for total body weight > 100 kg Antibiotics to be dosed at the high end of the recommended dose Cephalosporins One study suggested doubling dose or possibly dose adjust to body surface area Cefazolin 2 gram every 8 hours Penicillins Piperacillin tazobactam 4.5 grams Q 6 hours (usual dose Q 8 hours) Clindamycin Up to 4.8 grams daily in divided doses Doses of less than 10 mg/kg per 24 hours have lead to treatment failures 10

11 Antibiotics based to total body weight Vancomycin Initial loading dose of mg/kg in critically ill patients Scheduled dosing of mg/kg every 8 12 hours Monitor trough levels Daptomycin 4 mg/kg daily for complicated skin and soft tissue infection without staph aureus bacteremia 6 mg/kg daily for infective endocarditis or complicated skin and soft tissue infection associated with staph aureus bacteremia Antibiotics based on Adjusted Body Weight or specific dosing weight Aminoglycosides (gentamycin, tobramycin, amikacin) Based on adjusted body weight = ideal body weight x (total body weight ideal body weight) Larger once daily dosing regimen has not been studied in the obese population Monitor trough levels Quinolones Recommend dosing weight = ideal body weight x (total body weight ideal body weight) Dose of 4 5 mg/kg/dose every 8 12 hours for ciprofloxacin Voriconazole Based on adjusted body weight Antibiotics requiring no dose adjustment Carbapenems (although standard dose may not be effective in organisms with higher minimum inhibitory concentration) Linezolid Metronidazole 11

12 Sedatives Benzodiazepines Initial boluses based on total body weight Bolus dosing based on symptoms preferred over continuous infusions Dose requirements decrease over time when on an infusion Significantly prolonged elimination half life Propofol No dose adjustment based on total body weight Paralytics Succinylcholine and rocuronium No change in pharmacokinetics compared to non obese Dose by actual body weight Atracurium and vecuronium Prolonged duration of action if dosed according to actual body weight Dose by ideal body weight Other selected drugs Immunoglobulin Use either ideal body weight or dosing weight = Ideal body weight + [0.4 x (actual body weight ideal body weight)] Rounded to the nearest vial size Phenytoin Loading dose based on dosing weight = Ideal body weight + [1.33 x (actual body weight ideal body weight)] Load of mg/kg up to a maximum dose of 2 grams Maintenance dose of 5mg/kg total daily Check levels 12

13 Other selected drugs Amiodarone Standard dosing Digoxin Should be based on ideal body weight Lidocaine Suggested to base on adjusted body weight, but may need supplement bolus doses Only one small powered study which suggested total body weight, but better to start out low to decrease risk of toxicity Questions 13