BANG BANG

What is OSA? Why does OSA matter? And does STOP BANG help us truly identify OSA?

OSA is:

  • cessation of airflow >10sec, 5+x/hr + 4% desat in SaO2
  • definitions vary, but >15x /hr is diagnostistic
  • dx by polysomnography
  • Apnea/hypopnea index (AHI), which is derived from the total number of apneas and hypopneas divided by the total sleep time (mild up to 15, severe >30)

 

Obstructive Sleep Apnea (OSA) matters because:

  • harder to intubate, harder to ventilate
  • increased prevalance of cardiac disease: Afib, arrhythmias, stroke, CHF, cardiomyopathy, pulmonary hypertension, CAD
  • periop complications higher, including airway obstruction, hypoxemia, atelectasis, pneumonia
  • more sensitive to respiratory depressant effect of opioids and hypnotics

Source: http://www.ncbi.nlm.nih.gov/pubmed/18339794

Is STOP BANG Helpful?

The literature shows…

“The sensitivities of the STOP questionnaire with apnea-hypopnea index greater than 5, greater than 15, and greater than 30 as cutoffs were 65.6, 74.3, and 79.5%, respectively. When incorporating body mass index, age, neck circumference, and gender into the STOP questionnaire, sensitivities were increased to 83.6, 92.9, and 100% with the same apnea-hypopnea index cutoffs.”

See: http://www.ncbi.nlm.nih.gov/pubmed/18431116

And what are these complications?

Mostly pulmonary, with a few possible cardiac events mixed in as noted in this study in Chest, cited in Miller’s 8th edition( http://journal.publications.chestnet.org/article.aspx?articleid=1085863#t4)

 

Variables ODI4% Age, yr Sex BMI, kg/m2 Type of Surgery Complication
ODI 4%< 5 0.2 27 F 46.7 Laparoscopic gastric bypass surgery Transient episodes of unspecified tachyarrhythmia during the first 3 postoperative days
3.0 52 F 59.4 Laparoscopy with conversion to open ventral herniorrhaphy and adhesiolysis Hypoxemia treated with supplemental oxygen and BPAP
ODI 4%≥ 5 5.5 49 F 26.2 Total abdominal hysterectomy and right salpingoophorectomy cystoscopy with placement of ureteral catheters Hypoxemia was observed on postoperative day 3 and treated with oxygen supplementation; atelectasis was noted
6.0 49 F 39.1 Total abdominal hysterectomy and bilateral oophorectomy Intraperitoneal bleeding was treated with embolization
6.2 39 F 44.9 Laparoscopic gastric bypass surgery Intraperitoneal bleeding which resolved without surgery
7.6 61 M 33.5 Sigmoid colon resection Hypoxemia and hypotension.
12.9 64 M 37.0 Mitral valve replacement Hypotension and junctional escape rhythm
13.0 57 M 38.9 Laparoscopic colonic polypectomy Atelectasis
14.5 58 F 41.6 Total abdominal hysterectomy and bilateral oophorectomy Atelectasis
18.6 62 M 37.3 Left inguinal herniorrhaphy Wheezing observed which required treatment with bronchodilators
24.6 49 F 28.1 Total abdominal hysterectomy and bilateral oophorectomy Pneumonia
26.3 53 F 47.9 Gastric bypass surgery GI bleeding
31.9 50 M 29.6 Radical prostatectomy Hypoxemia treated with CPAP
34.1 62 F 31.4 Total abdominal hysterectomy and bilateral oophorectomy Atelectasis
34.2 69 M 36.9 Laparoscopic right hemicolectomy Pulmonary embolism; superior mesenteric vein thrombosis
36.4 55 F 49.5 Exploratory laparotomy, adhesiolysis, small bowel resection, partial hepatic resection, gastric bypass Chest pain (MI was ruled out)
82.4 66 F 46.8 Total abdominal hysterectomy and bilateral oophorectomy Hypoxemia treated with CPAP

*

F = female; M = male; BPAP = bilevel positive airway pressure. See Table 1 for abbreviation not used in the text.

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Dose Adjustment for Obese patients

From Ingrade, et al. Dose Adjustment of anesthetics in the morbidly obeseBr. J. Anaesth. (2010) 105 (suppl 1): i16-i23.doi: 10.1093/bja/aeq312 

Drug Dosing scalar Comments
Thiopental Induction: LBW

Maintenance: TBW

Simulations showed a 60% decrease in peak plasma concentration in MO subjects compared with lean subjects after a 250 mg dose.26 Induction dose adjusted to LBW results in same peak plasma concentration as dose adjusted to CO.26 Volumes and clearances increase proportionally with TBW.25
Propofol Induction: LBW

Maintenance: TBW

MO subjects given an induction dose based on LBW required similar amounts of propofol and similar times to loss of consciousness compared with lean subjects given propofol based on TBW.29 Volume of distribution and clearance at steady state increases with increasing TBW.28
Fentanyl LBW Clearance increases linearly with ‘PK mass’, an arbitrary scalar highly correlated to LBW.46
Remifentanil LBW An infusion based on LBW results in similar plasma concentrations as normal weight subjects were given an infusion based on TBW.51
Succinylcholine TBW Administration of 1 mg kg−1 based on TBW resulted in a more profound block and better intubating conditions compared with doses based on IBW or LBW.67
Vecuronium IBW Doses based on TBW result in a prolonged duration of action in obese vs non-obese subjects.69 70
Rocuronium IBW There is an increased duration of action when the drug is given based on TBW vs IBW.71
Atracurium, Cisatracurium IBW The duration of action is prolonged in obese subjects when given on the basis of TBW vs IBW.73 74

 

 

Anesthesia for patients with opioid abuse and tolerance

From Anesthesiology News: http://www.anesthesiologynews.com/download/Opioid_AN0613_WM.pdf

Eval

-try to ask most use in a day, rather than average, more objective
-time of last dose, who is prescribing
-single questions alternative to CAGE-AID: How many times have you used illegal drugs in the past year?

Long term opioid therapy

Methadone
-opioid agonists, with some NMDA antagonism
-typically 30-40mg qd

Buprenorphine
-parital opioid agonist
-no high

Suboxone
-combo of buprenorphine and naloxone
-when injected, only naloxone works

Vivitrol
-extended release naltrexone
-opioid antagonist
-for etoh and opioid abuse
-monthly injection

I/O management

3 areas: manage intox, prevent/tx withdrawal, achieve effective analgesia

Antagonist reserved for life-threatening resp depression, as precipitating w/d can make management harder
If not receiving agonist therapy:
-take long-standing Rx as directed before surgery
-clonidine to tx withdrawal sx, 0.1mg bid, also tx specific sx as they arise

Multimodal pain relief
-iv tylenol, exparel
-ketamine, a2 agonists
-nsaids, regional
-pregalbin and gabapentin good for neuropathic pain

P/o

comfort and safety

opioid tolerant pts requires 2-3x more than naive patients
but still at risk from resp depression

Withdrawal happens 2/2 bolus nature of pain relief
combine long acting and pca for pain
make sure to restart methadone, divide into 3x/d dose to take advantage of analgesic properties

Post-op for Suboxone
-more complicated, buprenorphine has a celing effect (partial u agonist)
-so increasing dose intial helps, but tops out so side effects also top out, making it safer for long term management, but tought post-op
-Buprenorphine has 1000x affininty for u than morphine
–>longer half life, so persists on receptor
–>only partial agonist, so analgesia not complete
4 recs:
1. maintenance therapy continue, short-acting opioids titrate to effect
2. divide bupre into TID (if surgery not that invasive/painful)
3. d/c bupre and treat with full opioids, remember bupre can be present for up to 5 days after d/c. Be aware of withdrawal sx from bupre.
4. convert to methadone 30-40mg/day, must be written as rx for pain not withdrawal (illegal).

Post-Op for Naltrexone once monthly
-naltrex is competetive antagonist
-opioid admin is tough to predict
-depends if pt missed a dose, at end of dosing cycle etc.
-postpone elective surgery if possible until tx complete
-otherwise, multimodal with opioids