KNOWN SECRETS!-PREANESTHETIC CHECK

Y1. Two cardinal symptoms of cardiac illness are exercise intolerance and chest pain
2.Systemic illness in : ASA 2- not incapacitating , ASA 3- incapacitating, ASA 4- life threatening
3. Take history of syncope, seriously, as it may point towards undetected significant CVS issues.
4. Cardiac catheterisation is indicated in whom, a non invasive test is strongly positive or whose symptoms are unequvivocal.
5. Postponing of surgery is considered, ONLY IF, BP is consistently >180/110 mm of Hg
6. Preoperative administration of bronchodilators and topical application of local anesthetics , are some strategies practiced to reduce bronchospasm at induction, in asthmatic patients.
7.  TOTAL LUNG CAPACITY: reduced in RLD and increased in OLD
FORCED VITAL CAPACITY(4-5L): reduced in both OLD and RLD
FEV1(75% of FVC): reduced in both OLD and RLD
FEV1/FVC(>75%): reduced in OLD
PEFR(450-650L/min):<120L/min if severe obstruction
MVV(70-100L/min): index of total cardiorespiratory function
(OLD-Obstructive Lung Disease, RLD-Restrictive Lung Disease, F-Fibrosis)
8. Mallampati score
G1-all structures visible
G2-uvula obscured by base of tongue
G3-only soft palate
G4-only hard palate
Thyro Mental Distance >6.5cm is normal
Mallampati score + TMD provides a positive predictive value of upto 100%
9. Volatile agents other than halothane also may cause jaundice
10. Non Alcoholic Steato Hepatitis (NASH-comprises obesity, T2 DM and elevated blood lipids) is an advanced form of Non Alcoholic Fatty Liver Disease (NAFLD). Incidence of NAFLD is rising in the western world.
11. Child Pugh Grade B patients should be optimised preoperatively. Grade C patients should not undergo elective surgery if possible.
12. Look for the development of Hepatorenal syndrome in the jaundiced patient, document it, and consider prophylactic measures like mannitol administration.
13. Cirrhotic patients are at risk of hypovolemia and so, consider CVP monitoring.
14. Anticipate higher incidence of PONV in E.N.T. and Gynecological surgeries. If more than one among the following risk factors is present, a prophylactic antiemetic should be administered: 1) female gender 2) non smoker 3) h/o PONV or motion sickness 4) predicted opioid use
15. The obese patient is at risk of perioperative hypoxia, because of (a) hypoventilation and (b) restriction of diaphragmatic excursion. Volume of epidural space will be less, reducing drug requirement. NIBP cuff may overestimate BP; so consider IBP, if required.
16. If planning to give transfusion, complete it 24 hours prior to surgery
17. DVT PROPHYLAXIS :
Low risk- Compressive stockings/ Pneumatic Compression Device
Medium risk- +LMWH (e.g.20-40 mg ENOXOPARIN s/c )
High risk- +LMWH. Maintain anticoagulation with Warfarin.
18. Patients of African or Afro-Caribbean descent should be screened for Sickle cell disease, using a Sickledex test.
19. Malignant hyperthermia, is a preventable cause of anesthetic death. Ask for family history; the standard test is the in vitro sensitivity of striated muscle to caffiene and halothane.
20. Clonidine reduces requirements for volatile anesthetics.
21. The amnesia produced by benzodiazepines is anterograde and lasts for about 10 mins,  if given i.v. , but much longer after oral doses
22. Benzodiazepines potentiate propofol.
23. The dose of Flumazenil, the benzodiazepine antagonist, is 100-200 microgram iv, followed by 100-400 microgram/hr. S/E: tachycardia,  hypertension, seizures
24. Lorazepam : Oral dose 1-4 mg (30-50 ug/kg).  Duration : 4-24 hours.  Produces appreciable anterograde amnesia. Abolishes vasoconstriction that accompanies fear.
25. Diazepam: Oral dose : 10-20 mg,  duration : 4-8 hours,  When given in combination with metoprolol, its anxiolytic effect is greatly enhanced.
26. Patients with alcoholic liver disease are very sensitive to promethazine. Promethazine has antihypertensive property.
27. Complete vagal block requires a dose of 3 mg of atropine.
28. Atropine should be avoided in small children with pyrexia or sepsis ; may result in overdose and febrile convulsions can occur
29. Patients with Downs syndrome may show resistance to parenteral atropine
30. Antisecretory effect of atropine,  is much more pronounced, if given as i.m. 1 hour before,  than immediately before induction as i.v.
31. Hyoscine,  glycopyrrolate and atropine increases chances of regurgitation by relaxing cardiac sphinctor of stomach. 
32. Atropine crosses the placenta and can protect foetus from vagal reflexes.
33. Hyoscine butylbromide is a gi or urinary antispasmodic at doses, of 10-30 mg oral/i.v.
34. Hyoscine hydrobromide is a mild respiratory stimulant and an antiemetic at doses of 0.3-0.6 mg im.
35. Glycopyrronium bromide (dose: 0.2-0.4 mg  /  4-8 ug/kg) is a better, antisecretory agent than atropine and emergence is faster, than after giving atropine; is effective in  preventing bradycardia after suxamethonium; but has no antiemetic effect.
36. The treatment of Central anticholinergic syndrome is with Physostigmine salicylate (2mg iv); it can also be used to modify the psychotic side effects of ketamine.
37. For major surgery,  Lithium should be stopped 2 days prior, as it will potentiate NDMR; if case is posted as emergency, may have to consider regional anesthesia or suxamethonium. Hydrate well and take care of fluid, and electrolyte balance.
38. NON SELECTIVE MAO INHIBITORS :
# May react with pethidine, morphine and fentanyl and can cause fits, coma, muscle twitching, hypertension, ataxia and ocular paralysis. Deaths have occurred. Chlorpromazine (25 mg) has found to be effective, in treating this. Regional anesthesia,  NSAIDs and a combination of chorpromazine and codeine are choices for postoperative analgesia. Severe hypertension and even death may occur with administration of vasopressor drugs (even with adrenaline contained in local anesthetic preparations). Treatment is with phentoamine. So non specific MAO inhibitors should be stopped,  2 weeks prior to surgery.
39. SELECTIVE MAO INHIBITORS:
# The specific,  reversible MAO-A inhibitors (moclobemide) and MAO-B inhibitors ( Selegiline,  used in treatment of Parkinsonism) are less dangerous and can be continued upto the day before surgery; but caution is still needed; avoid pethidine and sympathomimetic agents
40. SSRIs may prolong the action of warfarin; fluvoxamine an SSRI, may reduce the metabolism of ropivacaine; otherwise SSRIs are relatively safe in the perioperative period.
41. To avoid the recurrence of severe Parkinsonism, dysphagia and the risk of aspiration pneumonia, antiparkinsonian drugs like levodopa should be continued upto the time of surgery.
42. During the perioperative period, in response to the stress, cortisol secretion from the adrenal cortex may rise upto 500 mg/day from the normal value of ~25 mg/day. This response cannot occur in patients on corticosteroid therapy, due to adrenal suppression. Even a one week course of steroids or inhaled steroids can cause this suppression. But <10 mg prednisone per day or equivalents,  has no effect. For higher dose therapy,  it requires extra hydrocortisone e.g. 25 mg at induction,  followed by 25 mg 6 hourly for 24-48 hours (48 hours for major surgeries). i.m. route gives more sustained release.
43. Combined Oral Contraceptive Pills, if possible,  should be discontinued 4 weeks before major elective surgery or leg surgery, and started again at the first menstrual period, following an interval of 2 weeks after the surgery, if the patient is fully mobile. If this is not feasible, prophylactic heparin/LMWH should be considered. Risk for DVT is higher in case of pelvic/cancer/orthopaedic surgeries, old age, smoking, obesity and factor V Leiden mutation.