UBP 1.2 (Long Form): Endocrine – Obesity Flashcards
Secondary Subject -- OSA/Ambulatory Center Case Selection/ Bronchospasm/Difficult Airway
Intra-Operative Management:
How will you monitor this patient?
Is an arterial line indicated?
Can you obtain reliable noninvasive blood pressure measurements?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
Since this is a relatively low risk case, I would use standard ASA monitors, giving special attention to correct placement of a noninvasive blood pressure cuff.
This can be challenging in extremely obese patients and I would ensure that the bladder of the cuff encircled at least 75% of the upper arm.
If the cuff were too small, the blood pressure measurements may be falsely elevated;
if it were necessary to place the cuff on the forearm, the measurements may not prove accurate.
In the event that I was unable to obtain an accurate blood pressure with a cuff, I would consider placing an arterial line.
Clinical Note:
- The overestimation of blood pressure with a cuff that is too small can be significant (i.e. 50 mmHg).
- A cuff that is too large underestimates blood pressure, but to a lesser degree.
Intra-Operative Management:
What type of anesthetic will you employ?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
Given this patient’s increased risk for –
- difficult airway management (obesity),
- aspiration (obesity, diabetes, GERD), and
- respiratory depression (OSA patients often exhibit an increased sensitivity to the respiratory depressant effects of pain medications),
my preference would be to perform the case under local or regional anesthesia.
Either one of these techniques would make it possible to avoid airway instrumentation and reduce or eliminate the perioperative requirements for opioids and other respiratory depressants.
If I were to provide a neuraxial anesthetic, I would use straight local anesthetic without opioids to further reduce the risk of opioid-induced respiratory depression.
Intra-Operative Management:
She refuses local or regional anesthesia and you decide to proceed with general anesthesia.
How will you induce this patient?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
- (Online UBP – “commentary on intraop” 01:34)*
- (4 critical components – sample phrasing: “Given (A,B,C), I would ___, However, I recognize that __(risks)__, therefore, I may consider ___. – Mock Exam: 16:27-17:09)*
- —*
Given this patient’s obesity, diabetes, asthma, and history of gastric reflux, my goal would be to safely secure her airway while avoiding hypoxia, bronchospasm, and aspiration.
Therefore, assuming that after a careful history and exam I was not concerned about difficult airway management (despite her weight), I would:
- ensure the availability of difficult airway equipment;
- provide aspiration prophylaxis with an H2-receptor antagonist, metoclopramide, and a nonparticulate antacid;
- administer a B2-agonist to optimize her asthmatic condition;
- place the patient in the reverse trendelenburg position (improves respiratory mechanics, reduces the risk of passive regurgitation, and facilitates rapid intubation of the trachea);
- denitrogenate with 100% oxygen;
- apply cricoid pressure;
- administer intravenous lidocaine to blunt the response to laryngoscopy;
- perform a rapid sequence induction; and
- rapidly secure her airway with a cuffed endotracheal tube.
However, since a rapid sequence induction does not reliably provide an adequate depth of anesthesia to prevent bronchospasm,
I would be prepared to treat this complication during the induction and intubation of this asthmatic patient.
Intra-Operative Management:
Would you plan change if she were a Mallampati III on airway exam?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
Although a Mallampati score is only one part of the airway exam, this would be concerning, especially when combined with her super morbid obesity.
Therefore, I would perform a complete airway examination and, if I remained concerned, talk to the patient about an awake intubation to reduce the risk of significant hypoxia and/or aspiration.
If she agreed to this plan, I would minimize sedation
(risk of respiratory depression in this patient with OSA) and
adequately anesthetize the airway to prevent any stimulation that could result in bronchospasm (asthmatic patient).
Intra-Operative Management:
Assume her airway is not concerning.
How would you position the patient for induction and intubation?
What happens to the patient’s closing capacity when you move her into the supine position?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
Considering the increased risk of aspiration associated with her obesity, diabetes, and history of GERD, I would position the patient in the –
slightly head-up position to reduce the risk of passive regurgitation and facilitate rapid intubation.
Moreover, the reverse-trendelenburg position may improve this obese patient’s respiratory mechanics.
–
Although the closing capacity is unaffected when moving from the upright to the supine position, its relationship with functional residual capacity is worsened resulting in early airway closure and shunting.
Should I be faced with a “can’t intubate and can’t ventilate” scenario, pulmonary shunting secondary to early airway closure would decrease the time I had to reestablish ventilation and oxygenation before significant desaturation occurred.
Intra-Operative Management:
How should you adjust your propofol induction dosing in the obese patient?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
- (06:12 – online UBP “commentary on intra-op”)*
- Xtra Q – Why is propofol maintenance dose based on TBW?*
- –*
The induction dose of propofol in the obese patient should be based on ideal body weight,
while maintenance dosing should be based on total body weight.
Theoretically, lipophilic drugs (propofol, benzodiazepines, opioids, barbiturates, etc.) have a larger volume of distribution in obese patients secondary to increased deposition into body fat, making an initial loading dose based on total body weight (TBW) reasonable.
In practice, however, the pharmacologic effects of obesity on anesthetic drugs are extremely complicated and do not always mirror expectations.
Therefore, a reasonable approach is to calculate your initial dose based on IBW and titrate additional dosing to clinical effect.
Clinical Notes:
-
Specific Drugs
- Propofol – Induction: IBW; Maintenance: TBW
- Pentothal – Induction: TBW; Maintenance: TBW
- Midazolam – Loading dose: TBW: Maintenance: TBW
- Succinylcholine – Induction: TBW; Maintenance: TBW
- Vecuronium/Rocuronium – Induction: IBW; Maintenance: IBW
- Atracurium/Cisatracurium – Induction: TBW; Maintenance: TBW
- Fentanyl/Sufentanil – Loading Dose: TBW; Maintenance: IBW
- Remifentanil – Induction: IBW; Maintenance: IBW
-
Ideal Body Weight:
- Males IBW = 50 kg + 2.3 kg/inch over 5 feet
- Females IBW = 45.5 kg + 2.3 kg/inch over 5 feet
Intra-Operative Management:
Are you going to use narcotics at induction?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
- (online UBP – Commentary on intra-op 07:30 – great answer by Dr. George –*
- – may consider ketamine)*
While the use of narcotics at induction would help to achieve the depth of anesthesia necessary to avoid bronchospasm during laryngoscopy of this asthmatic patient,
I would use minimal amounts of short-acting opioids for this patient with moderate-to-severe OSA, in order to
avoid opioid-induced post-operative respiratory depression.
Intra-Operative Management:
Which muscle relaxant would you use and
how would you adjust dosing?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
I would feel comfortable using many of the muscle relaxants, depending on the goals of the case.
However, given the patient’s asthma, muscle relaxants have the potential to cause significant histamine release, such as atracurium and mivacurium, should be avoided, if possible.
Also, given this patient’s obesity, the initial loading dose of most lipophilic durgs*, such as atracurium and cisatracurium, should be based on total body weight (TBW) due to a relatively increased volume of distribution.
On the other hand, hydrophilic medications, such as vecuronium and rocuronium, are more appropriately dosed according to ideal body weight (IBW).
In either case, redosing should be titrated to maintain the desired level of neuromuscular blockade.
*Exceptions include – digoxin, procainamide, and remifentanil.
Intra-Operative Management:
Does it matter which inhalational agent you use?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
It shouldn’t matter.
However, obese patients metabolize volatile agents more extensively and, therefore, it may be wise to avoid Halothane due to the increased risk of Halothane hepatitis (Halothane is no longer available – a little out of date).
There has also been the widespread belief that the large fat stores of obese patients may result in delayed wakening when using more soluble agents like isoflurane as compared to less soluble agents like sevoflurane.
However, with the exception of very long cases (> than 4 hours), this concern has not been supported by the evidence.
Intra-Operative Management:
During the case the pulse-oximeter shows her oxygen saturation gradually decreasing to the high 80’s.
What will you do?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
- (Commentary on Intra-Op 10:27 – Think of DDx… Then go through ABC’s)*
- –*
I would immediately switch to 100% oxygen, hand ventilate, auscultate the chest, ensure proper ETT placement, check airway pressures, and check the circuit and machine.
If the patient were in trendelenburg position, I would level her out or even place her in reverse-trendelenburg position to improve respiratory dynamics.
I would also consider administering a B2-agonist through the endotracheal tube to optimize her asthmatic condition.
If everything, including ETT positioning, seemed ok, I would then adjust my ventilatory settings, starting with the optimization of PEEP.
Intra-Operative Management:
You listen and hear expiratory wheezing.
What will you do?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
(Commentary on Intra-Op 11:23)
–
Expiratory wheezing and oxygen desaturation are consistent with bronchospasm secondary to her asthma and/or aspiration – (could be pulmonary edema, too.)
Therefore, I would switch to 100% oxygen, increase the concentration of my inhalational agent (aka.. deepen my anesthetic), and administer albuterol through the ETT.
My goals are to achieve bronchodilation and ensure an adequate depth of anesthesia to prevent any further stimulation-induced bronchospasm.
If these interventions failed, I would administer a small dose of epinephrine.
Intra-Operative Management:
You treat the bronchospasm and it resolves.
How will you extubate this patient?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
- (Commentary on Intra-Op 12:52 – great answer by Dr. George – uses 4 critical components)*
- –*
Given her history of asthma and recent bronchospasm,
I would extubate the patient under a deep plane of anesthesia to prevent any further bronchospasm.
However, recognizing that she is at increased risk for aspiration due to her obesity, diabetes, and history of acid reflux,
I would do my best to empty her stomach with an orogastric tube and be prepared to quickly take action should any regurgitation of stomach contents occur.
Intra-Operative Management:
How would you transport this patient to the PACU?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
Given her obesity and obstructive sleep apnea, I would –
attempt to improve her respiratory mechanics and prevent upper airway obstruction by –
- providing supplemental oxygen,
- applying CPAP, and
- transporting her to postop in the head up position.
Post-Operative Management:
You are called to the post-op area to evaluate the patient. Her pulse-oximeter reading is 83%.
What do you think might be going on?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
Given her obesity, OSA, asthma, and increased risk for aspiration, there are a number of things that I would consider as possible causes of her hypoxia including:
- airway obstruction secondary to sleep apnea;
- bronchospasm;
- respiratory depression secondary to narcotics;
- aspiration (hypoxia often occurs secondary to edema, atelectasis, and/or bronchospasm); and
- atelectasis with significant pulmonary shunting (the latter might occur secondary to aspiration or the use of inadequate intra-operative tidal volumes).
- Moreover, I would consider the possibility that her hypoxia is the result of – Pulmonary embolism, a condition that occurs more commonly in the morbidly obese.
Post-Operative Management:
The post-op nurse says the patient was doing fine until she gave her 4 mg of Morphine for pain control.
What will you do?
- (A 36-year-old, 188 kg, 5’4” female is scheduled for open umbilical hernia repair.*
- PMH: The patient is an insulin dependent diabetic for the past 6 years, has hypertension that is well controlled, and has moderate-to-severe obstructive sleep apnea. She uses her albuterol inhaler 2-3 times per week and was last in the emergency room with an asthmatic attack over a year ago.*
- PE: VS: BP = 148/89 mmHg, P = 78, T = 37 °C, R = 22*
- Airway: Mallampati I, good neck range of motion, adequate thyromental distance*
- CV: RRR*
- Lungs: Clear to auscultation*
- Stress Test: Negative)*
Since this history is most consistent with narcotic-induced airway obstruction or respiratory depression, I would –
- position the patient in the head-up position,
- apply 100% oxygen, and
- apply CPAP.
I would then –
- consider administering narcan to reverse the depressant effects of the morphine,
- while at the same time providing non-opioid analgesics such as ketorolac to maintain pain control.
Finally, since the relatively short half-life of narcan places the patient at risk of reoccurring airway obstruction or respiratory depression, I would –
- ensure close monitoring for an extended period of time and administer additional doses of narcan as necessary.
Clinical Note:
- Drug 1/2 life:
- IV Narcan: 1/2 life in adult = 30 - 60 minutes
- IM Narcan: 1/2 life = 80 minutes - 6 hours
- Morphine: 1/2 life = 2 - 3 hours
