Anaesthesia for Shoulder Surgery in the Sitting Position. Dr Con Kolivas Staff Anaesthetist Box Hill Hospital Tuesday, 27 May 2008

Transcription

1 Anaesthesia for Shoulder Surgery in the Sitting Position Dr Con Kolivas Staff Anaesthetist Box Hill Hospital Tuesday, 27 May 2008

2 Introduction History Variations Physiology Surgical Features Advantages Disadvantages Technique Personal Perspective Conclusions

3 History Open shoulder surgery Semi-sitting Arthroscopic Lateral Sitting Steep upright

4 Semi Sitting "Beach chair"

5 Semi Sitting Classic position Used for open shoulder surgery Airway access minimal Physiological disturbance small Pressure points Eyes Elbows Wrists Securing head Theoretical Venous Air Embolism

6 Lateral Shoulder arthroscopic surgery Classic lateral + Finger trap Least physiological disturbance Airway access possible Pressure points Elbows Knees Axillae

7 Sitting Neuro

8 Sitting Evolution of semi-sitting Steep upright 80 more than neuro Dedicated operating table Spyder Physiological disturbance greatest Pressure points Elbows Wrists Eyes Sciatic n. Head securing Airway Access

9 Sitting

10 Physiology GRAVITY Exaggerated position cf neurosurgery 30 cm between heart->head 1.3mmHg per cm water Relative cerebral hypoperfusion Venous return Stroke risk? Bezold-Jarish Reflex Vaso-vagal in awake Blunted sympathetic nervous system response of anaesthesia Venous Air Embolism PAE with PFO (Right to Left Shunt) Airway Obstruction Risk of Venous obstruction causing significant decrease in CPP

11 Physiology 2 Relative Contraindications to neurosurgical sitting position Cerebral ischaemia upright awake Minor?Cardiac instability?age extremes Ventriculoatrial shunt in place and open Left Atrial Pressure < right atrial pressure Platypnoea-orthodeoxia Preoperative demonstration of patent foramen ovale or right-to-left shunt Little relevance to shoulder surgery struck through

12 Surgical Features Axillary plexus damage in lateral position Surgical Exposure Arm positioning Less tissue retraction and damage Predates finger trap Arthroscopy relevance? Less bleeding More hypotension?

13 Anaesthesia advantages 1 Better respiratory function?

14 Anaesthesia advantages 2

15 Anaesthesia advantages 3

16 Anaesthesia advantages Respiratory function Less bleeding Less cranial n. damage Head security with spyder Pressure care Challenge?

17 Anaesthesia Disadvantages Haemodynamic Hypotension routine Bradycardia 25-40% Arrhythmias Rare Venous Air Embolism No reported cases Cerebrovascular Hypoperfusion Correlation with BIS Paradoxical Air Embolism Not reported

18 Disadvantages 2 Airway Access Obstruction Securing Positioning Complexity Pressure points Eyes Elbows Wrists Buttocks

19 Technique Regional vs General Regional Blockade Usual Generic Regional concerns Interscalene block High success rate Usually misses small section of innervation Unpleasant surgical procedure requiring sedation Cardiovascular complications Blunted but not ablated Hypotension uncommon Bradycardia 25% Sedation blunts compensation further

20 Technique 2 General Anaesthesia Usual Generic issues with GA Cardiovascular complications more common Hypotension almost routine Bradycardia more common Reflexes further blunted Regional blockade abolishes any sympathetic response exaggerating CVS issues

21 Technique 3 Extra Management Pre-op Patient suitability?consent issues Large bore IV access Arterial Line Regional Block if desired Vasopressors prepared TED stockings

22 Technique 4 Monitoring Routine + Arterial Line BIS?ECG 5 lead Theoretical: Brain ischaemia monitoring Doppler Ultrasound Trans-Oesophageal Echo Pulmonary Artery Catheter Neck Tourniquet Emergency practice drill

23 Technique 5 Induction/Technique Relaxant ETT Controlled Ventilation Achieve haemodynamic stability in supine position before sitting Fluid loading

24 Technique 6 Maintenance? Preemptive anticholinergics Move arterial transducer with head position Raise position incrementally Adjust vasopressor as required Observe pressure care

25 Personal Perspective Regional + General Teaching opportunity Reliability Patient/Anaesthetist/Surgeon satisfaction Trainees may go on to perform procedure under regional once they master the block Haemodynamic consequences of General are greatest post induction, so avoiding block to rely on painful stimulus for BP is unhelpful. Single shot blockade covers vast majority of pain of the first day which is mostly due to capsular distension, then oral analgaesia satisfactory.

26 Personal Perspective 2 Pre-op Consent issue is impossible to tackle? Full length TED stockings Note venous congestion 16g IV access No fluid loading (TED stockings and vasopressor fill vessels and diuresis post-op common). Premed with midazolam 40µg/kg Interscalene block Reverse trendelenburg (Venous congestion) Single shot n. stimulator >0.2mA <0.4mA +/- Ultrasound guidance 30ml 0.75% levobupivacaine 75µg clonidine (note hypotensive effect) Block lasts hours

27 Personal 3 Induction Fentanyl 3µg/kg Propofol 1mg/kg Rocuronium 0.6mg/kg Maintenance Air/Oxygen FiO2 0.8 Desflurane BIS monitoring

28 Personal 4 Positioning Preempt with 0.2mg Glycopyrrolate Start phenylephrine with induction Move arterial transducer to ear level Adjust vasopressor to maintain BP minimum of 10mmHg below acceptable heart level pressures ( in nonhypertensive patient). Elevate legs Elevate head till 45 degrees then reassess 5mg/hour and titrate to effect Use mean BP as endpoint and keep >= 75% of preinduction value Most data supports no BP changes <=45 degrees Usually adjusting BP prior to elevation smooths transition

29 Personal 5 BIS monitor Valuable added information Minimise anaesthetic depth safely thereby minimising vasopressor requirement. Indirect monitor of perfusion Falls to zero when brain profoundly hypoperfused.

30 Pictures

31 Pictures 2

32 Pictures 3

33 Pictures 4

34 Pictures 5

35 Conclusions Risk transferred from surgical positioning to one of Anaesthesia monitoring Can be safely conducted with significant extra effort Worldwide experience confirms relative safety Worldwide experience also confirms relative danger when conducted without deference to physiological issues Familiarity with position is paramount to safety Communication and not surprise

36 Conclusions 2 Outstanding concerns How do we consent for the relative risk of a position? What don't we know or can't quantify? Cardiovascular risk Cerebrovascular risk Vasopressor use Fluid challenges Subtle neurological deficits What constitutes a contrainidication? How would you have your shoulder operated on?