1. Posterior Fossa Tumor With Air Embolus and Intraoperative Cardiac Arrest R. Alexander Schlichter Assistant Professor of Clinical Anesthesiology and Critical Care Perelman School of Medicine University of Pennsylvania

2. Disclosure Dr. Schlichter does not have any relevant financial interest or affiliation with the manufacturer of any products, devices or services to disclose.

3. Introduction Posterior Fossa Tumors require unique surgical conditions with concominant anesthetic accomomdations Postioning, monitoring, and resuscitation bring unique challenges to the neuroanesthesiologist The position, surgical approach, neuromonitoring modalities, and the risk of hemorrhage must be clearly articulated to the anesthesia care team by surgery before the procedure

4. Risks and complications Increased ICP – Decreased Venous drainage from certain positions – Decreased CSF drainage – 4 th Ventricle obstruction Brain Swelling Remote Bleed Venous Air Embolism!

5. Positioning Different positions can be employed to optimize surgical exposure, reduce bleeding, and facilitate tumor removal These include: – Sitting – Prone – Lateral, park bench – Concorde or modified concorde – Supine, retrosigmoid

6. Sitting position: Pros For certain tumors, optimal surgical exposure Less bleeding at normotensive conditions Increased venous and CSF drainage, decreasing ICP and brain swelling Less airway and facial edema post-op Optimal ventilation

7. Sitting Postion: Cons High risk (24%-60%) incidence of Venous Air Embolism Venous pooling leading to orthostatic hypotension, decreased venous return Increased risk of pneumocephalus, tension pneumocephalus with Nitrous Oxide Hypovolemia with inhaled agents may worsen V/Q mismatch (controversial)

8. Sitting Position in Mayfield Frame

9. Decline of the Sitting Position In addition to the risks of the sitting, may centers have decreased or even abandoned it It requires a longer set up – Unique frame – Increased invasive monitors take time (see below) – Institutional knowledge and expertise decrease with less use What are the alternatives?

10. Prone Can also be difficult, especially in obese patients To decrease bleeding, head is still above heart, so risk of VAE is still present Airway not easily accessible, extubation, obstructions, mainstem more difficult to troubleshoot Pressure ulcers and edema can occur for extended cases Post operative Visual Loss (POVL) associated with hypotension

11. Simple prone position

12. Concorde/Modified Concorde For certain tumors (citation) it provides optimal approach and less bleeding In modified, access to left arm allows access to IV, arterial line by anesthesiologist Head is still above the heart, so VAE is risk Can be an awkward position, risk of shoulder or brachial plexus strain in down arm

13. Concorde

14. Modified Concorde

15. Lateral and Park Bench Less cumbersome than sitting or prone Increased risk of bleeding Venous compression if the neck is twisted too much, less drainage Brachial Plexus injury of ipsilateral upper extremity is not padded appropriately

17. Supine Easiest (and quickest) position Access to arm for TIVA, arterial line, pulse ox Not the best surgical exposure Retrosigmoid or neck flexion can decrease venous and CSF drainiage, leading to brain swelling and increased ICP Severe neck twisting can cause sialadenitis

19. The Cheat!!! In order to facilitate a quicker prep time, the supine position is popular Less monitoring, less procedures The surgeon than proceeds to ask for “head up” Either in reverse trendelenburg, or head up 30-45% Venous Embolism insues!

20. Venous Air Embolism: Diagnosis Transesophageal Echo – Cumbersome, impractical, requires constant monitoring Precordial Doppler – Noninvasive very sensitive Right Atrial Catheter End tital N 2 – Requires expensive monitoring End Tital C0 2 – Very effective, although a later finding, usually a sign of decreased cardiac output Pulse Oximetry (Dead)

21. Right Atrial Catheter Placed through antecubital artery (sometimes via subclavian, rarely IJ) CVP/RV wave form and EKG used to guide into the right atrium Goal is a CVP wave form with an isoelectric P wave

23. Case Report 43 male yo male with cerebellopontine angle tumor GA, ETT, A-line, large bore access Right Atrial Catheter not placed (“patient is supine”) Retrosigmoid approach, surgeon requests head up 45 o, precordial doppler placed under drapes 7 windmill sounds on PCD: VAE suspected Pressure to 40/20 several times, epinephrine, fluids given Cardiac Arrest!

24. VAE: Treatment Tell the surgeon, flood the field with saline If possible, head down to neutral position If using, turn off N 2 O, initiate 100% O 2 If present, drawing back on RAC can be diagnostic AND therapeutic PEEP is controversial, risks are thought to outweigh theoretical benefits Jugular compression has shown to decrease air entrainment – Decreases venous drainage – Carotid manipulation can lead to bradycardia, plaque embolism

25. Cardiac Arrest Pressor/ionotropic therapy Intravenous resuscitation, appropriate blood products if there is associated hemorrhage Initiate appropriate pharmocologic code protocols (usually asystole vs. PEA) Defibrillator present for shockable rhythms CPR: fortunately (?) this patient was supine

26. However, CPR in the Prone Position?!?! The first case report of CPR in the prone position was in 1992 Advocates the “reverse precordial compression maneuver” One hand placed on the back of the patient, in the mid-thoracic spine, and the other hand placed on the lower third of the sternum serving as counter- pressure to the compression of the back (especially in open tables such as the Jackson W. Z. Sun et al., “Successful Cardiopulmonary Resuscitation of Two Patients in the Prone Position Using Re- versed Precordial Compression,” Anesthesiology, Vol. 77, No. 1, 1992, pp. 202-204.

27. . Julian Brown, James Rogers, Jasmeet Soar Cardiac arrest during surgery and ventilation in the prone position: a case report and systematic review Resuscitation, Volume 50, Issue 2, 2001, 233 - 238 http://dx.doi.org/10.1016/S0300-9572(01)00362-8

28. Post operative course Patient successfully resuscitated, heart beat returned with epinephrine, fluids, and CPR Surgical resection finished head down, no issues To ICU intubated after a negative CT scan Awake, extubated POD#1 with no neurologic or cardiac sequellae

29. Conclusion Surgery in the posterior fossa comes with risks of bleeding, brain swelling, and most importantly, VAE Communication including surgical approach, positioning, anesthetic, and monitoring is paramount Be prepared to detect, prevent, and treat VAE, including CPR (in any position)