CCP 331 Bariatrics π© Flashcards
How to dose paralytics in obesity
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- Roc = ideal body weight (IBW)
2. Suxx = total body weight (TBW)
Overweight definition (BMI)
BMI 25-30
obesity definition
BMI of β₯30
severe obesity definition
BMI β₯40 (or β₯35 in presence of comorbidities)
Define Body mass index
- simple calculation using a personβs height and weight
2. BMI = kg/m2 (weight in kg / height in metres squared)
prevalence of obesity in Canada
- 40% adults overweight
- 30% adults obese
- 3% adults βmorbidly obeseβ
- 27% adults normal/healthy
Vital Signs in Obesity Emergency Management
πππMEGA PEARLπππ
- NIBP readings can be falsely elevated in obese patients as improperly placed small cuff size often overestimates BP
- A βnormalβ NIBP could represent a shock state in an obese adult
- Consider placing an early arterial line to obtain and trend accurate BP readings over time
- The Shock Index can be helpful in making a diagnosis of occult shock in obese and non-obese patients. Shock Index = HR/SBP; Any number > 1 suggests occult shock
ECG Alterations in Obesity Emergency Management
- Low voltages β d/t size of their chest wall
- Longer QT intervals sometimes >500ms as a result of obesity alone
- Signs of LVH β (consider obesity-associated cardiomyopathy)
Important Pulmonary Physiology changes in Obesity
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- β respiratory reserve is 2Β° to β total lung capacity and β FRC. The β reserve compromises an obese patientβs ability to tolerate respiratory insults such as pneumonia
- β airway pressures are a result of β airway resistance (heavier chest walls, β abdominal girth, atelactatic lung bases). The β pressures lead to: Smaller oxygen reserves at baseline, β WOB, Shorter time to desaturation during induction and a shorter Safe Apnea Time
- β incidence of hypoxemia and hypercapnia at baseline
- β risk of aspiration pneumonitis
- More difficult to ventilate with BMV
V.A.P.O.R.S mnemonic for factors that need to be considered in planning and executing a safe and successful intubation for critically ill obese patients
Ventilation (can you bag mask this patient?)
Acidosis
Pressures (BP, peak pressures, plateau pressures etc)
Oxygenation (safe apnea time)
Regurgitation
Shock Index (see above)
Pharmacologic Adjustments in Obesity Emergency Management
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- Lipophilic drugs (eg. Propofol) need to be dosed based on TBW
- Hydrophilic drugs (eg. Ketamine) are dosed based on IBW
- ABX also have different dosing profiles based on their class
Radiology/Imaging in Obesity Emergency Management
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- The FAST scan may be indeterminate or falsely negative given the depth of penetration required to visualize Morrisonβs pouch
- The chest x-ray will be under-penetrated
- CT images will be more difficult for the radiologist to interpret and as a result, injuries are more often missed.
describe βrampingβ in Obesity Emergency Management
- Build a big ramp behind the patientβs head and torso to achieve an ear-to-sternal-notch configuration with towels/blankets or commercially available products
- position the patient in reverse Trendelenburg to take the weight of the panus off the chest
ANATOMIC changes to the airway/respiratory system of the obese patient
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- β neck circumference d/t excess cervical adipose tissue β upper airway collapse
- β soft tissue deposition in the relatively closed space of the oropharyngeal cavity β pharyngeal airway narrowing
- β neck circumference + dorsocervical fat deposition β limited neck extension
- Fat, obese neck β difficult access for a surgical airway
PHYSIOLOGIC changes to the airway/respiratory system of the obese patient
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- obese patients have markedly β lung volumes
- for each unit β in BMI, FRC, expiratory reserve volume, VC, TLC, and residual capacity β 0.5% to 5%
- β FRC β closure of small airways and an β in airway resistance β under-ventilated areas of lung, atelectasis, and intrapulmonary shunting β decreased safe apnea time
- obese patients develop VQ mismatch d/t their upper lung zones aerated preferentially, with lower lung zones perfused preferentially
- chest wall compliance is β d/t increase in adipose tissue in the thoracic cage
- Oxygen consumption is ~1.5x higher in the obese patient than in non-obese patient
- d/t the β in O2 consumption and WOB, obese patients CO2 production is also increased
- β pulmonary reserve β rapid onset of hypoxemia during RSI β potential peri-intubation cardiac arrest πππ
discuss Preoxygenation in the bariatric RSI
π§π§π§ ESOTERIC WISDOM π§π§π§
- obese patients have β cardiopulmonary reserve and desaturate rapidly during intubation
- Often, traditional methods of preoxygenation using a NRB or BVM are insufficient in the critically ill obese patient
- NIV is the preferred preoxygenation method. CPAP at 10cmH2O has been shown to β atelectasis, β oxygenation, and β safe apnea time in the obese patient
- BiPAP can also be used to preoxygenate obese patients, but is less well studied than CPAP
- CPAP or BiPAP should be maintained for at least five minutes during the preoxygenation period
- HFNC provides minimal CPAP, no evidence of benefit in preoxygenation prior to RSI for obesity
discuss Patient Positioning in the bariatric RSI
- d/t alterations in respiratory physiology, positioning is critical for success in both preoxygenation and intubation of the obese patient.
- obese patients should be placed in either a HOB 45Β° or sitting position during preoxygenation
- patients should be placed in a head up/ramped position to optimize laryngoscopic view during intubation. patientβs sternal notch should align with his or her external auditory meatus
discuss medication dosing in the bariatric RSI
- obese patients often receive inappropriate doses of sedative and paralytic medications during RSI
- Rocuronium should be dosed according to the patientβs ideal body weight (IBW)
- Succinylcholine should be dosed according to the patientβs total body weight (TBW)
- Lipophilic drugs (eg. Propofol) need to be dosed based on TBW. Therefore these doses will be much higher than in average adults (BE CAREFUL THOUGH DONβT GIVE A MASSIVE FUCK OFF DOSE OF PROPOFOL OR YOUβLL KILL THE PATIENT).
- Hydrophilic drugs (eg. Ketamine) are dosed based on IBW
discuss mechanical ventilation in the bariatric patient
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- Vt must be calculated using IBW rather than TBW.
- This is important for the intubated obese patient, for whom the use of TBW to determine the Vt can lead to injurious lung volumes, barotrauma, and VILI
- obese patients produce β amounts of CO2 d/t β metabolic demand, β oxygen consumption, and β WOB. D/t this, they adopt a rapid, shallow breathing pattern and have a baseline RR that ranges from 15β21 bpm. You must account for this altered physiology and set a higher RR than for the non-obese patient.
- Obese patients demonstrate improved respiratory mechanics and alveolar recruitment when provided PEEP. PEEP reverses airflow limitations and helps to prevent alveolar derecruitment caused by the β in FRC
Challenges in ventilating the morbidly obese patient
- Lung volumes (eg. FRC) are decreased.
- Work of breathing, O2 consumption and CO2 production are increased
- Airway resistance is β (until you β the FRC with PEEP)
problems with lung mechanics in morbid obesity
- Expiratory reserve volume is decreased
- FEV1 to FVC ratio is increased.
- VC, TLC and FRC are decreased.
- Work of breathing is increased
- The weight of the chest wall contributes to a decreased respiratory compliance
- Airway resistance is β (until you β the FRC with PEEP)
discuss the balance of oxygen supply and demand in the bariatric patient
- O2 consumption and CO2 production is β (more tissue metabolising), thus ventilatory needs are β
- Because of their β abdominal and chest wall mass, morbidly obese patients βdedicate a disproportionately high percentage of total VO2 to conduct respiratory work, even during quiet breathingβ
- The amount of additional O2 / CO2 flux to be expected is something like 150% of the normal values.
Discuss strategies for Invasive mechanical ventilation in morbid obesity
- no difference between PCV and VCV in terms of outcome data.
- some sources recommended PCV d/t benefits of the constant pressure (better flow distribution and βtime under the curveβ) and decelerating flow pattern (better patient-vent compliance, lower sedation requirements, better flow distribution)
- Calculate tidal volume based on patientβs height (IBW). JUST BECAUSE THEY ARE FAT DOESNβT MEAN THEIR LUNGS ARE ANY BIGGER
- A higher PEEP and Paw is generally required
- keep the Pplat under 30-35 cmH2O, using driving pressure as a backup surrogate of safety
- Esophageal balloon may help to calculate the actual Ptp and account for the resistive contribution from the chest wall
- You need a higher PEEP than you think.
- Post-intubation recruitment manoeuvre may be necessary to β oxygenation and maintain lung volume
- You need a higher RR than you think d/t their inherent β in VO2, and β CO2 production d/t β basal metabolism from being fat
cardiovascular changes in the bariatric patient
- Cardiac output is β
- Total blood volume is β
- LV contractility is impaired
- LV size and wall thickness are β
- Hypertension is common
- LV diastolic pressure is β, and fluid loading is poorly tolerated
- The RV is likely failing or completely decompensated.
hematologic changes in the bariatric patient
- polycythaemia, associated with chronic hypoxia β hyperviscosity, and β risk of thrombosis
- chronic immobility leads to β risk of DVT/PE
Pharmacokinetic changes in the bariatric patient
- Volume of distribution is β for many lipophilic drugs
- Hepatic clearance may be β
- Renal clearance may be β
- It is unclear whether all drugs (or most?) must be dosed to IBW
- Drugs dosed to TBW may easily achieve toxic doses (propofol!!)
- Fatty acids may compete with drugs for protein binding, displacing free drug into the circulation.
- Conversely, Ξ±1-acid glycoprotein levels may β, leading to β protein binding
- Metabolism of some pathways (eg. Phase 1 hepatic reactions such as oxidation, reduction and hydrolysis) are consistently β in the morbidly obese.
Metabolic changes in the bariatric patient
- β resting energy expenditure
- A chronic proinflammatory state
- Insulin resistance β DM1/DM2
- β fatty acid mobilization, and hypetriglyceridaemia
- Accelerated protein degradation
- More rapid depletion of lean body mass
changes in the bariatric patient leading to Difficulty in physical examination
- Respiratory examination is limited d/t difficult auscultation: you canβt hear anything, nor is it easy to get behind the patient to listen to their back.
- Cardiovascular examination is limited by difficult auscultation (heart sounds may be inaudible) and difficult palpation.
- Abdominal examination (eg. for organomegaly) is frustrating
weight limit of Helijet stretcher (Sikorsky S-76)
500lbs
Weight limit AND device weight for Bariatric #9 (Ferno #9B)
what are the implications of this
Ferno #9B is rated for 227kg/500lbs
Ferno #9B device weighs 22lbs
What this means is if your LifePort system is rated to 450lbs, your TOTAL PACKAGE WEIGHT is 450lbs. This includes patient weight, weight of #9 (22lbs), and gear/equipment weight (fully loaded CCP tray can be ~45lbs)
Eg: Add ~70lbs for #9B + tray and you are now only rated for a ~380lb patient
weight limit of LifePort Sled System (Beechcraft Super King Air B350 and Cessna Citation C560 Jet)
what are the implications of this
450lbs
What this means is if your LifePort system is rated to 450lbs, your TOTAL PACKAGE WEIGHT is 450lbs. This includes patient weight, weight of #9, and gear/equipment weight.
Beechcraft King Air B350 maximum allowable loading width (patient/equipment)
26in/66cm
Cessna Citation C560 Jet maximum allowable loading width (patient/equipment)
29in/73.5cm
Ferno CCP βTrayβ weight (empty)
10lb/4.5kg
Average weight of fully loaded CCP βtrayβ with vent/pumps/monitor/meds
45lb/ 20.5kg
Weight of LTV 1200
14.5lbs/6.5kg
Standard Ferno #9 Weight limit AND device weight
Load Limit 350lb/159kg
Device Weight 17lb/8kg
common Radiology problems associated with the bariatric patient
- Chest Xrays may be of poor quality
- some patients are too fat to fit into CT or MRI scanners.
- Ultrasonography is limited by thick abdominal / chest wall / leg fat
- CT/MRI table weight restrictions are typically 160-180kg when fully extended
What is BMI calculated from?
Height and weight
What is a normal BMI?
18.5 to 25
