ANAESTHESIA C (26) Flashcards
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CVC LENGTHS AT SKIN?
- Both SC and IJ are the same at
- R = 16cm
- L = 20cm
WHAT GAUGE ARE TRIPLE LUMEN CVC LINES?
- The brown lumen is 16g, the other 2 are 18g
IDEAL POSITION OF A CVL
- in the SVC, with the tip 2cm proximal to the RA
WHAT IS ABDOMINAL COMPARTMENT SYNDROME?
- 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
DERMATOMES
- C2 = collar
- C3 = above clavicles
- C4 = below clavicles
- C5678T1 = arms
- T2 = interaxillary
- T4 = nipple
- T6 = xiphoid
- T10 = umby
- T12 = belt
- L1 = groin crease
SPINAL DOSES USING 0.5% HEAVY MARCAIN
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
WHAT LA TO USE FOR PERIPHERAL NERVE CATHETERS?
- ROPIVACAINE 0.2%, 5-10 ml/h
MAXIMUM LA DOSES
- LIGNOCAINE = 5mg/kg, 7 with Adrenaline
- BUPIVACAINE = 2mg/kg, 3 with Adrenaline
- ROPIVACAINE = 3mg/kg
HEPARIN WITHOLDING TIMES FOR INSERTING SPINALS/EPIDURALS
Coags must be normal for insertion, so hold:
- IV HEPARIN: 4h
- S/C HEPARIN/CLEXANE: 12h
WHEN CAN YOU GIVE HEPARIN AFTER SITING A SPINAL/EPIDURAL
- It is generally safe to give SC Heparin immediately, and IV 1h after atraumatic insertion
VASCULAR STENTS : BARE METAL vs DRUG ELUTING AND SURGERY
- 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:
- Acutely stopping antiplatelet Drugs perioperatively is DOUBLY RISKY because:
- Surgery is a pro-coagulant state
- ‘rebound stickiness’ occurs …. so
- defer elective surgery 3/12 for BMS and 12/12 for DES
- stop PLAVIX but continue Aspirin preop
- Acutely stopping antiplatelet Drugs perioperatively is DOUBLY RISKY because:
*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
PACEMAKERS AND ICDS AND SURGERY
The main issue is that diathermy noise may be interpreted as either
- appropriate cardiac activity : causing inhibition of pacing, or
- 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
ANAPHYLAXIS BLOODS
- Take MAST CELL TRYPTASE at 1, 4 & 24 hours
TROPONIN esp TROPONIN-T
- 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
NORMAL RENAL FUNCTION =
- Urine output of 0.5 ml per kg per hour
- N electrolytes
- Urea 3-8 mmol/l
- Creat 50-120 umol/l
HYPERKALEMIA : EFFECTS AND TREATMENT
- 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%
WHY IS CA CHLORIDE PREFERRED OVER CA GLUCONATE?
Because:
- CaCl contains 3x more Ca than CaGluconate
- Ca Gluconate needs to be hepatically metabolised before the Ca becomes available
pO2 vs SpO2
50/60/70 mmHg = 85/90/95 % saturated
WTF IS BASAL BOLUS INSULIN?
the BASAL BOLUS INSULIN regime is a more physiological way of giving Insulin than the Actrapid SS, dividing the daily insulin prescription into
- a long acting BASAL insulin dose (LANTUS) given nocte
- 3 equal short acting BOLUS doses given with meals (NOVORAPID)
METHOD
- write “Insulin : see basal bolus chart” in drug orders
- estimate daily Insulin requirements as either
- 0.4u/kg/d if not previously on Insulin
- usual 24h units if already on Insulin
- give 1/2 the units as LANTUS at 2100, and 1/2 as 3x equal mealtime doses of NOVORAPID
- check BSL before each dose and consider adjusting previous or pending dose
SGLT2 INHIBITORS, EUGYLCAEMIC DKA AND PERIOPERATIVE MANAGEMENT
- 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’
WHAT IS SITAGLIPTIN?
- 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.
WHAT IS DIABETES INSIPIDUS, AND HOW TO MANAGE?
- 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
VASOPRESSIN vs DDAVP
-
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
WHAT IS SIADH?
- 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
100mmHg = x cm H2O?
- 100 mmHg = 130 cm of water (or blood)
WHAT IS THE HEARTS NORMAL EJECTION FRACTION?
- The Normal EF = 50 - 75%
