OBESITY ANESTHESIA Flashcards
When performing a spinal anesthetic on a morbidly obese individual, you know that you should
use a lower volume of local anesthetic
What is the most reliable test for detecting an inadvertent intrathecal or intravascular epidural catheter placement in a laboring parturient?
Negative aspiration for CSF or blood
**What is the only ventilator adjustment shown to improve respiratory function consistently in obese individuals? WAS on SEE EXAM
PEEP
If a drug distributes primarily to lean tissues, then its loading dose should be based upon the patient’s
Lean body weight
The recommended tidal volume for an obese patient should be estimated as
Predicted body weight
Tubular renal tubular reabsorption and GFR in obesity
Increased
Sodium excretion with obesity is
Decreased/ impaired
Increase in direct proportion to body weight
Plasma cholinesterase activity
FRC and obesity
Decreases exponentially as BMI increases
2 warning sings of diminished cardiovascular reserve amd CV complications in OBESES PATIENTS.
ORTHOPNEA
Paroxysmal nocturnal apnea.
2 preop interventions for Obesity : HOB and consideration for OSA
Head up 30 degrees
CPAP prior to induction if OSA
Airway that is very helpful to achieve if difficult ventilation of the obese
LMA
3 Most important intraoperative consideration for obesity: comment on TV, PEEP and fiO2. Why do you want FiO2 that you mentioned?
TV 6-8 ml/kg of IBW (to avoid overdistention)
PEEP 10-12 cm H2O
FIO2 less than 0.8 because INCREASED FIO2, accelerates atelectasis.
3 Most important POST-operative consideration for obesity:
CPAP or BIPAP
O2
Head up
Intestinal mobility and regioonal
Early recovery of intestinal mobility
This medication is not suitable for bariatric surgery and why?
ketorolac; increased chance of GI bleed.
The most severe post op complications for bariatric surgery
Anastomotic leaks and strictures
PE
Sepsis
Gastric prolapse and bleeding
Most common signs and symptoms of anastomotic leaks from most common to least
Tachycardia
Fever
Abdominal pain
What is the most sensitive sign of an anastomotic leak?
Tachycardia (HR >120)
Mortality of Roux en Y bypass
0.5-1%
Most serious metabolic complication of bariatric surgery
Severe malnutrition ; red meat poorly tolerated
Associated with biliopancreatic conversion?
Fat soluble vitamin malabsorption
FAT soluble vitamins are
ADEK
Ideal gas for obese patients
Low solubility
You can use all 3 MRs for obese patients but which one is preferred and why?
Vec, roc, cis
cis preferred because organ-independent mechanism (HOFFMAN)
When blood loss is replaced , the ____ratio
3:1
3 mL of cristalloid for 1 ml blood loss.
Any advantage of Large TV for obese patients?
NO
Anatomical issues with the obese patients when in comes to regional anesthesia
Obscured bony landmarks
LA requirements in ______in the obese patients? why?
Decrease; because of the fatty infiltration and vascular engorgement caused by intra-abdominal pressure, which decreases the volume of the epidural space.
Extubation criteria for obese patients as far as RR and SPO2
RR >10 and < 30
SPO2 > 95% on < 0.4 FiO2
Extubation criteria for obese patients as far as TV and VC
TV 5ml/kg IBW
VC 10-15 ml/kg IBW
Supine position for obese: parameters affected
FRC and oxygenation are decreased
Position preferred and why?
Lateral decubitus positiion; better diaphragmatic excursion
What provides the safest safe apnea period during induction of anesthesia?
HEAD up position (Reverse trendelenburg)
CUFF with a bladder that encircles
75% of the UPPER ARM CIRCUMFERENCE
How is preoxygenation during induction in obese different from regular patients?
4 vital capacity breaths with 100% oxygen for 30 seconds, are superior to the 3 minutes of 100% preoxygenation.
The object of patient position for the intubation is to position the
chin at HIGHEST LEVEL than the chest.
Stacking for intubation is to
placing towels or folded blankets under the shoulder and head to compensate for the exaggerated flexed position of posterior cervical fat.
BEYOND STACKING step is the
HELP (Head elevated Laryngoscopy position)
HELP significantly
Elevates the patient’s head, upper body and shoulder above the chest.
What is the most common mononeuropathy after bariatric surgery?
CARPAL TUNNEL SYNDROME
Regular OR tables have a MAX weight limit of approximately
200 kg
A difficult airway relation to BMI
NOT CLOSELY correlated with BMI/
What is the single major predictor of problematic intubation in morbidly obese patients?
Patient’s neck circumference.
What is a normal neck circumference for a 70 kg male?
about 35 cm
Probability of difficult intubation for a male with a neck circumference of 40cm
5%
Probability of difficult intubation for a male with a neck circumference of 60cm
35%
my mnemonic AMTOMA difficult intubation
Age (increase age) Male TMJ pathology OSA Mallampati III or IV Abnormal upper teeth
Anatomic changes associated with obesity that contribute to difficult airway: JOINTs
Limited movement Atlanto-axial joint and CERVICAL SPINE by upper and lower cervical fat pads
Anatomic changes associated with obesity that contribute to difficult airway: Mouth and pharynx changes
EXCESSIVE Tissue folds in mouth and pharynx
Anatomic changes associated with obesity that contribute to difficult airway: NeCk changes
Short THICK neck
VERY thick submental fat (double chin)
Anatomic changes associated with obesity that contribute to difficult airway: Cervical
Suprasternal, presternal, posterior cervical fat.
Obesity and medication on DOS, except
Continue all except oral and oral hypoglycemics.
Medications. that must be discontinued?
Anorexiant drugs and herbal supplements for 14 days
Increased risk of infection in the obese necessitates
ABT prophylaxis
Medication to be considered for anxiolysis for the obese patients? why?
Dexmedetomidine ; low resp depressant effects
Effective at reversing low BP in the obese
Phenylephrine.
3 main system to assess during the preop of an obese patients/
CV
RESP
Hepatic function
ECG evidence of RV failure; 2
Right axis deviation
TALL PRECORDIAL R WAVES
What is the most useful confirmation of pulmonary HTN?
TRICUSPID REGURGITATION on ECHO
Increase probability of OS is
NECK CIRCUMFERENCE > 40 cm
Common deficiencies in obese patients
CaFIB Calcium Folate Iron B12
What can lead to ACUTE POST-GASTRIC REDUCTION SURGERY NEUROPATHY?
Vitamin and nutritional deficiencies
Initial doses for obese patients are based on ____
LBW (Lean body weight)
Why are initial doses for obese patients based on Lean body weight (LBW) ?
Because LBW is HIGHLY CORRELATED with CO and drug clearance
Subsequent doses for obese patients based on
responses to initial dosing
Propofol dosing : Loading , Maintenance
Loading: TBW ; Maintenance: LBW
Midazolam dosing is based on
TBW
Thiopental dosing is based on
LBW
CIS- ATRACURIUM and ATRACURIUM dosing : Loading , Maintenance
Loading: TBW ; Maintenance: LBW
3 drugs with different dosing TBW then LBW
Propofol
Atracurium
Cis-atracurium
Succinylcholine dosing is based on
TBW
Fentanyl remifentanil, sufentanil dosing is based on
LBW
ROC and VEC dosing is based on
LBW
Pancuronium dosing is basd on
TBW
TBW dosing summary :
T- MI-SU-CI- A- PANDENE
What are the 2 pharmacokinetics principles to keep in mind when determining drug dosing for OBESE patients?
Vd and Clearance
What is the key to the administration of the loading dose:
Volume of distribution