Anaesthesia in the Beach Chair Posi0on NEURO SIG Mee0ng Queenstown 7-2013 Mark Hayman MBBS, MPH, FANZCA
Outline 1. Incidence of strokes during beach chair posi0oning (BCP) 2. Physiology of CBF in upright posi0on 3. Monitoring for inadequate CBF 4. Management sugges0ons 5. Conclusions
None! Disclosures
Case Report: NSW 2011 50yo former rugby player died of a massive stroke during arthroscopic shoulder surgery in beach- chair posi0on...caused by a failure to es0mate and maintain an appropriate level of mean arterial pressure in the blood supply of the brain (NSW coroner) recommenda/on that all anaesthe0c departments develop guidelines for the appropriate adjustment for the hydrosta0c gradient by anaesthe0sts when calcula0ng MAP for beach- chair surgery.
Other case reports 4 cases reported by Pohl & Cullen in 2005, ages 47-57 3 recent cases from France with GA & interscalene block, ages 54-58 Common features: young pa0ents, minor comorbi0es & periods of intra- op hypotension. Morbidity presumed to be result of ischaemic stroke due to cerebral hypoperfusion. Pohl & Cullen, J Clin Anesth, 2005 Villevieille, Ann Fr Anesth, 2012
Case: Incomplete Circle of Willis 50yo male, 180cm tall, smoker, Pre- op BP 110/75 SBP @ arm = 95-100mmHg, lowest MAP=61mmHg ( 35-40mmHg @ Head)? ACom? PCom CTA: incomplete circle of willis. MRI @ 2 months: Lei Anterior & Middle Cerebral Artery territory infarct Drummond, A&A, 2012
Incidence of Brain Injury following surgery in N=5177 Retrospec1ve Series Shoulder Surgery Neuro Cases Beach Chair Posi0on? BP Measureme nt A Line (heart) n=682 NIBP n=3545 A line (heart) n=422 A Line (head) n=528 Av. Mean BP Average BP Drop % % Pa1ents >1 episode BP Drop >40% from baseline 75 14.4 51% 74 19.3 48% 78 17.6 75 19.7 No immediate postopera0ve catastrophic outcomes occurred, upper 95% CI = 7 per 10000 Average Hypotensio n Time per episode 16.6min 52% 16.7min Pin- On & Munis, A&A 2013
Incidence of Intraopera0ve Stroke Survey of orthopaedic surgeons, cases > 200K Es0mated stroke rate: 0.004% All events occurred in pa0ents in the BCP Friedman, Orthopaedics, 2009 And yet hypotension is common in the BCP posi0on. Pin- On, 2013, Friedman 2009, Yadeau 2011, Rohrbaugh 2013 So is hypotension the cause? Perhaps Lam & Baldwin, Blood Pressure & Adverse Periopera/ve Neurologic Outcomes: An Uncomfortable Posi/on, A&A 2012
What is Hypotension? BP while asleep: drop 30% from baseline SBP MAP Soo et al, Anaesthesia, 2011
Blood Pressure what is baseline? Pre- op baseline MAP mmhg Day0me median - 9.5% Sleep median - 19.5% Sleep nadir Intra- op nadir - 33.4% - 35.2% Soo et al, Anaesthesia, 2011
Siphon Model of CBF Head? A V Flow α A - V
Does a Siphon exist in upright humans? CVP IJV CVP EJV IJVP=Internal Jugular Venous Pressure @ Base of skull Dawson et al, Standing up to the challenge of standing: a siphon does not support CBF in humans, ajpregu, 2004.
& in Giraffa camelopardalis MAP = 118 Cranial VP = - 4 5m MAP = 200 CVP = 4 Brondum, Jugular venous pooling during lowering of the head affects blood pressure of the anesthe/zed giraffe, AmJPhysiolRegulIntegrCompPhsiol, 2009.
Monitoring NIRS BP TCD?EEG
Cerebral Oximetry (SctO2) OXIPLEX Con0nuous wave technology: interpret photon scaver & absorp0on Frequency domain systems differen0ate scaver & absorp0on. Davie et al, Anesthesiology, 2012
NIRS in Sixng versus Lateral Posi0on Cerebral Desatura0on Events (CDEs) LDP = 0% BCP = 80% Murphy, A&A, 111(2), 2010
SctO 2 & Upright posi0on N=20 SctO2 LeN SctO2 Right MAP @ Head Awake 69 68 76 Supine 79 79 67 Upright Min Value 57* 59* ~30 * p < 0.05 comapred to awake & compared to supine asleep Decrease of >20% in SctO 2 in >80% pa0ents. Decreases in SctO 2 correlated with BP drops (R= 0.6) & EtCO 2 (R = 0.47) Moerman et al, Eur J Anaesthesiology, 2012
Influence of BP on Cerebral Perfusion & Oxygena0on SctO2 vs MAP MCAv mean vs MAP Change in MAP (mmhg) Change in MAP (mmhg) Lucas, Blood Pressure & Cerebral Autoregula/on, Hypertension, 2010
SctO2 with phenylephrine & head up posi0on? N=34 RCT Saline Phenylephrine SCO2% MAP MCAv SCO2% MAP MCAv Rm Air 68 94 66 101 Pre- O2 74 94 73 101 Post Induc0on 79 68 31.5 77 68 27.3 Post Infusion 76 71 30.1 67 102 32.7 Upright Posi0on 68 53 26.8 59 91 33.9 MAP: transducer @ level of head Soeding et al, BJA 2013
Sct0 2 & SjVO 2 SctO 2 SjVO 2 Brassard, BJA, 2009
Cerebral Oximetry & SjvO2% SctO2% SjvO2% Jeong et al, Anesthesiology, 2012
NIRS & Extracranial Contamina0on % change from baseline of SctO2 Davie & Grocoa, Anesthesiology, 2012
Theore0cal explana0on for SctO2 changes seen with phenylephrine. Modified from Meng & Gelb, BJA, 2012
Transcranial Doppler (TCD) Hypercapnia used to validate TCD against Xenon. Correla0on: R = 0.849 MCAv Reac0vity (Doppler) CBF Reac0vity (Xenon) Bishop et al, Stroke, 1986.
TCD & Hypotension with Beach Chair Posi0oning Possible mechanisms for reduced MCAv: 1. Impaired autoregulatory response 2. Cerebral arterial pressure may have been below lower limit of autoregula0on MAP @ head <50mmHg in 11 of 19 pa0ents. McCulloch et al, AAIC, 2010
Components of Autoregulatory response azfp McCulloch et al, AAIC, 2010
Influence of BP on MCAv Lucas, Blood Pressure & Cerebral Autoregula/on, Hypertension, 2010
The impact of Cardiac Output on MCAv? MCAv Cardiac Output l/min Ogoh, et al, J Physiol, 2005
Management Sugges0ons
Avoid Sixng Posi0on US Survey of Shoulder Surgeons Low rate of stroke reported rate in the beach chair posi0on 0.00382% - 0.00461% But.. All cerebrovascular events were associated with surgeries in the beach chair posi0on. Friedman, Orthopedics, 2009, 32(4)
Avoid GA? Koh & Murphy et al, J Shoulder Elbow Surg, 2013
Maintain a Normal BP Supine with 20% BP drop @ level of heart Beach Chair with 20% BP drop Awake
Maintain or augment Cardiac Output MAP CO SctO2 Supine pa0ents, controlled ven0la0on, propofol/remi. Meng, BJA, 2011
Head Posi0on Toole J, Arch Neurol, 1960
Vola0le vs Propofol? Jeong et al, 2012
Other Monitors: Cerebral Oximtery or TCD? Interpret Cerebral Oximetry with cau0on. Future studies may provide clinical outcome data. TCD probably more robust but less convenient and unlikely to become a standard monitor.
Summary Incidence of stroke in BCP: seems to be low. Mechanism is likely to be hypoperfusion in these cases. Cerebral Oximetry as monitor of cerebral oxygena0on in BCP is problema0cal, par0cularly following vasopressor use. TCD is a more robust but less convenient monitor of CBF BP measurement or calcula0on at level of head should be standard of care (there is no siphon) Maintenance of pre- op BP is probably reasonable approach. Consider augmen0ng CO rather than simply BP support. Consider use of regional & seda0on rather than GA. Maintain neutral head posi0on. If GA used aim for mild hypercapnia & perhaps use vola0le rather than propofol based GA.
Discouraging data on the anti-depressant