Open AAA

 

Pre-op issues:

Assessment

Problems:

·     IHD, cardiomyopathy, HTN
Cardiac patient undergoing non-cardiac surgery

·     Smoking, COPD

·     T2DM

·     CKD

Investigations:

·     Blood: FBE, UEC, LFT, coag, HbA1c

·     Cardiac: ECG, TTE, ±stress test

Review:

·     PMU

·     Specialty team

Optimisation

Lifestyle:

·     Stop smoking

·     Diet

·     Exercise (not sure)

Medication to start:

·     Aspirin

·     Statin

Medications to withhold:

·     Antiplatelets (except aspirin)

·     Anticoagulants (± reversal)

·     ACE-inhibitor

·     Hypoglycaemics (SGLT 72h, metformin 48h, sulfonylurea 24h)

Discussion

Major risks:

·     AMI

·     Stroke

·     Renal failure

·     Spinal cord infarction

·     Death

Response:

·     Explore patient’s values

·     Stratify risk: RCRI, NSQIP, etc.

·     Discuss goals of care

·     Book ICU bed

 

Intra-op issues:

Aneurysm rupture

Critical moments:

·     Laryngoscopy

·     Incision

Plan: preserve transmural pressure

·     ±Thoracic epidural

·     Opioid

·     Antihypertensive

·     Topicalise glottis

Bleeding

Preparation:

1.    Access: PIVC + RIC line + A-line + CVC + pump set

2.    Warming: upper body warmer + rapid fluid infuser

3.    Products: cell salvage + cross-match 10 units

Monitoring:

·     Volume: PPV, IDC, ABG

·     Clotting: ABG + viscoelastic + plt + coags

·     Heat: nasal temp probe

Goals:

1.    Stop bleeding: surgery + permissive hypotension

2.    Promote clotting: reversal + products + TXA + calcium + heat

3.    Replace losses: 2L crystalloid + cell saver + bank (1:1:1 ratio)

4.    Preserve vital organs: mAP >50, PaO2 >100, pH >7.2, lactate <4

Clamping

Main things:

·      Communication ++

·      Preparation ++

·      Request slow clamping

↑↑Afterload / ↑↑Preload

·      ∝ proximity to heart

·      Risk of AMI, APO

·      Before: hypovolaemia + vasoconstriction (norad)

·      After: vasodilatation (GTN)

Ischaemia:

·      ∝ duration

·      Can’t do much about it

·      Turn off lower limb forced air warmer

Unclamping

Main things:

·     Communication ++

·     Preparation ++

·     Request slow un-clamping

↓↓Afterload / ↓↓Preload

·     ∝ proximity to heart

·     Risk of organ ischaemia

·     Before: euvolaemia + vasodilatation (GTN)

·     After: vasoconstriction (norad)

Reperfusion:

·     ∝ duration

·     Risk of myocardial depression, vasoplegia

·     Before: hyperventilation + CaCl infusion

·     After: vasoconstrictor (norad infusion) ± inotrope (adrenaline bolus)

·     Turn on lower limb forced air warmer

Renal protection

Risk factors:

·     Patient: CKD, heart failure, T2DM, renovascular disease

·     Surgery: clamp height, clamp time

·     Anaesthesia: ↓DO2, nephrotoxins, massive transfusion

Preserve the vessels:

·     Fenestrated graft

·     Re-anastomosis

Preserve DO2:

·     ↑mAP: volume + pressor

·     ↑SpO2

·     ↑Hb

Reduce VO2:

·     Cold perfusate = kidney-plegia
(warm ischaemic time only 30 mins)

Long list of things that don’t work:

·     Dopamine (renal dose 1-3mcg/kg/min)

·     Mannitol

·     Frusemide

·     NAC

·     Methylprednisolone

Spinal protection

Risk factors:

·     Surgery: TAA, clamp height, clamp time

·     Anaesthesia: inadequate DO2

Monitoring:

·     MEP

·     SSEP

Preserve the vessels:

·     Fenestrated graft

·     Re-anastomosis

Preserve DO2:

·     ↑mAP: volume + pressor

·     ↓CSF pressure: lumbar drain if high risk

·     ↑SpO2

·     ↑Hb

Lumbar drain:

·     Indicated if high risk (e.g. complex TEVAR)

·     Transducer at level of insertion

·     Max 10cmCSF

·     Max 30mL/h drainage (risk of SDH, coning)

·     Keep in situ 72 hours (high risk period)

·     Monitor in ICU

·     Prophylactic antibiotics

 

Post-op issues:

 

Pain

Neuraxial:

·     ±Thoracic epidural

·     ±ITM

Regional:

·     Bilateral rectus sheath catheters

Parenteral:

·     Ketamine infusion

·     Opioid infusion in ICU -> PCA on the ward

Monitoring:

·     APS review q12h

·     Test platelets + coags before removal of epidural catheter

Organ failure

Mitigation and prevention:

·     Vasoplegia: CVC + noradrenaline

·     Renal failure: fluid status + perfusion pressure

·     Coagulopathy: viscoelastic + warmth + products + adjuvants

·     Liver failure: volume + pressor

·     Spinal cord ischaemia: ±lumbar drain

 

 

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