ANAESTHESIA C (26)

Question 1

CVC LENGTHS AT SKIN?

Answer 1

• Both SC and IJ are the same at
  
  • R = 16cm
  • L = 20cm

Question 2

WHAT GAUGE ARE TRIPLE LUMEN CVC LINES?

Answer 2

• The brown lumen is 16g, the other 2 are 18g

Question 3

IDEAL POSITION OF A CVL

Answer 3

• in the SVC, with the tip 2cm proximal to the RA

Question 4

WHAT IS ABDOMINAL COMPARTMENT SYNDROME?

Answer 4

• Normal Intra-Abdominal pressure is <10mmHg, and can be easily measured with a sensor in a bladder catheter
• Systemic increases in capillary permeability, eg in trauma, sepsis or large burns, can cause massive oedema fluid accumulations in the peritoneal cavity, mesentery, gut wall and retroperitoneum
• this can cause increases in Intra-Abdominal pressure, or ‘Abdominal Hypertension’, which, if >20mmHg, progressively impairs ventilation, cardiac output and renal function
• MANAGEMENT
  
  • address the cause
  • dont over resuscitate
  • consider decompressive laparotomy

Question 5

DERMATOMES

Answer 5

• C2 = collar
• C3 = above clavicles
• C4 = below clavicles
• C5678T1 = arms
• T2 = interaxillary
• T4 = nipple
• T6 = xiphoid
• T10 = umby
• T12 = belt
• L1 = groin crease

Question 6

SPINAL DOSES USING 0.5% HEAVY MARCAIN

Answer 6

There are 2 does, high and low

• for a high (T4) block :
  
  • 2.5 mls for LSCS
  • 4.0 mls other
• for a low (T10) block (hips/urology)
  
  • 2.5 mls

Question 7

WHAT LA TO USE FOR PERIPHERAL NERVE CATHETERS?

Answer 7

• ROPIVACAINE 0.2%, 5-10 ml/h

Question 8

MAXIMUM LA DOSES

Answer 8

• LIGNOCAINE = 5mg/kg, 7 with Adrenaline
• BUPIVACAINE = 2mg/kg, 3 with Adrenaline
• ROPIVACAINE = 3mg/kg

Question 9

HEPARIN WITHOLDING TIMES FOR INSERTING SPINALS/EPIDURALS

Answer 9

Coags must be normal for insertion, so hold:

• IV HEPARIN: 4h
• S/C HEPARIN/CLEXANE: 12h

Question 10

WHEN CAN YOU GIVE HEPARIN AFTER SITING A SPINAL/EPIDURAL

Answer 10

• It is generally safe to give SC Heparin immediately, and IV 1h after atraumatic insertion

Question 11

VASCULAR STENTS : BARE METAL vs DRUG ELUTING AND SURGERY

Answer 11

• Traditionally, stents were BARE METAL (BMS), which epithelialised rapidly, but had poor long term patency.
• Newer stents are DRUG ELUTING (DES), which epithelialise more slowly, giving better long term patency, but require long term antiplatelet* therapy.
• PERIOPERATIVE MANAGEMENT:
  
  1. Acutely stopping antiplatelet Drugs perioperatively is DOUBLY RISKY because:
     
     • Surgery is a pro-coagulant state
     • ‘rebound stickiness’ occurs …. so
  2. defer elective surgery 3/12 for BMS and 12/12 for DES
  3. stop PLAVIX but continue Aspirin preop

*NOTE: it is ANTI-PLATELET therapy that is needed for stents, - remember this as the platelet is the FIRST part of clot formation. Anticoagulants like HEPARIN/CLEXANE have little protective benefit

Question 12

PACEMAKERS AND ICDS AND SURGERY

Answer 12

The main issue is that diathermy noise may be interpreted as either

1. appropriate cardiac activity : causing inhibition of pacing, or
2. VT/VF : causing inappropriate shock

Previously we used to switch devices to a non sensing ‘SAFE’ mode preoperatively, but modern units now discriminate so well we generally just have a pacemaker magnet available intra-operatively

Question 13

ANAPHYLAXIS BLOODS

Answer 13

• Take MAST CELL TRYPTASE at 1, 4 & 24 hours

Question 14

TROPONIN esp TROPONIN-T

Answer 14

• TROPONIN is a contraction regulating protein found in both cardiac and skeletal muscle.
• Assay of one variant, MYOCARDIAL TROPONIN-T (Trop-T) is a sensitive and specific test for myocardial injury, but
  
  • it rises slowly : may take 12h
  • interpretation of modest rises is uncertain in CRF
• [Trop-T] > 100 is Positive

Question 15

NORMAL RENAL FUNCTION =

Answer 15

• Urine output of 0.5 ml per kg per hour
• N electrolytes
• Urea 3-8 mmol/l
• Creat 50-120 umol/l

Question 16

HYPERKALEMIA : EFFECTS AND TREATMENT

Answer 16

• Normal ECF K+ = 3.5 - 4.5
• Hyperkalemia increases cellular irritability by partly depolarising the cell membrane, producing ECG changes:
  
  • at 7.0 : peaked T
  • at 8.0 : wide QRS and no P
  • at 9.0 : sinusoidal ecg then VF

Rx:

• ultimately need to eliminate excess K+ by RESONIUM/Dialysis,
• but in the interim may SHIFT it back into the cells by giving:
  
  • ACTRAPID 5u IV (+ 50 mls 50%D) or
  • HCO3- : 1mlkg 8.4%
• or STABILISE the cell membrane with CaCl: 10 mls x 10%

Question 17

WHY IS CA CHLORIDE PREFERRED OVER CA GLUCONATE?

Answer 17

Because:

1. CaCl contains 3x more Ca than CaGluconate
2. Ca Gluconate needs to be hepatically metabolised before the Ca becomes available

Question 18

pO2 vs SpO2

Answer 18

50/60/70 mmHg = 85/90/95 % saturated

Question 19

WTF IS BASAL BOLUS INSULIN?

Answer 19

the BASAL BOLUS INSULIN regime is a more physiological way of giving Insulin than the Actrapid SS, dividing the daily insulin prescription into

1. a long acting BASAL insulin dose (LANTUS) given nocte
2. 3 equal short acting BOLUS doses given with meals (NOVORAPID)

METHOD

1. write “Insulin : see basal bolus chart” in drug orders
2. estimate daily Insulin requirements as either
   
   • 0.4u/kg/d if not previously on Insulin
   • usual 24h units if already on Insulin
3. give 1/2 the units as LANTUS at 2100, and 1/2 as 3x equal mealtime doses of NOVORAPID
4. check BSL before each dose and consider adjusting previous or pending dose

Question 20

SGLT2 INHIBITORS, EUGYLCAEMIC DKA AND PERIOPERATIVE MANAGEMENT

Answer 20

• SGLT2 Inhibitors like Dapagliflozin* increase urinary excretion of glucose by inhibiting the ‘Sodium-Glucose Transporter’ pumps which reabsorb filtered glucose from the renal tubule.
• They can cause perioperative ‘euglycaemic DKA’ and should be stopped 2/7 prior, and still require postop blood sugar, pH and ketone monitoring - the wards can now do this.
• Where not held:
  
  • For minor surgery: go ahead.
  • For major surgery: go ahead, provided:
    
    • HbA1C <9 and ketones <0.6
    • Insulin infusion commenced after
    • Endocrinology team notified

* ‘fear the flozins’

Question 21

WHAT IS SITAGLIPTIN?

Answer 21

• Sitagliptin, aka Januvia, increases insulin levels by boosting the insulin releasing hormones secreted by the gut in response to a meal.
• As such, it is relatively self regulating and has a low risk of hypoglycaemia.

Question 22

WHAT IS DIABETES INSIPIDUS, AND HOW TO MANAGE?

Answer 22

• DI = excessive production of DILUTE URINE, usually due to loss of ADH (VASOPRESSIN) secretion from the PITUITARY, eg after head injury
• the result is a dilute polyuria, dehydration and hypernatremia (Na >150)
• Rx : address the dehydration, and replace vasopressin with either:
  
  • DDAVP 6-12 mcg
  • VASOPRESSIN, 20u in 40mls, 1ml stat then 4-0 ml/h

Question 23

VASOPRESSIN vs DDAVP

Answer 23

• VASOPRESSIN is a posterior pituitary hormone which defends the BP by
  
  • Retaining water at the kidney
  • Vasoconstricting
  • Boosting F8 and platelet function
• DDAVP is a modified synthetic vasopressin which retains its antidiuretic and procoagulant effects, but is not vasoconstrictive. Its mainly used for DI and haemophillia

Question 24

WHAT IS SIADH?

Answer 24

• SIADH = the Syndrome of Inappropriate ADH secretion, where VASOPRESSIN is inappropriately secreted from an ectopic focus, eg a lung tumour
• it results in inappropriate water retention by the kidney, with volume overload and dilutional Hyponatremia (<120)

Rx:

• address the cause if possible
• fluid restriction

Question 25

100mmHg = x cm H2O?

Answer 25

• 100 mmHg = 130 cm of water (or blood)

Question 26

WHAT IS THE HEARTS NORMAL EJECTION FRACTION?

Answer 26

• The Normal EF = 50 - 75%