Establishing a Multidisciplinary Cavernous Carotid Injury Simulation to Train Neurosurgical, Otolaryngology, and Anesthesia Residents

Summary

This protocol establishes a multidisciplinary model to train learners on management of cavernous carotid artery injury. Cadaveric heads undergo expanded endonasal approach and injury to the cavernous carotid artery, and perfusion pump simulates blood flow to the injury point. Learners are tasked with medical and surgical management over 3 scenarios.

Abstract

Carotid artery injuries are serious complications of endoscopic endonasal surgery. As these occur rarely, simulation training offers an avenue for technique and algorithm development in resident learners. This study develops a realistic cadaveric model for the training of crisis resource management in the setting of cavernous carotid artery injury. An expanded endonasal approach and right cavernous carotid injury is performed on a cadaveric head. The cadaver's right common carotid artery is cannulated and connected to a perfusion pump delivering pressurized simulated blood. A simulation mannequin is incorporated into the model to allow for vital sign feedback. Surgical and anesthesia resident learners are tasked with obtaining vascular control with a muscle patch technique and medical management over the course of 3 clinical scenarios with increasing complexity. Crisis management instructions for an endoscopic endonasal approach to the cavernous carotid artery and blood pressure control were provided to the learners prior to beginning the simulation. An independent reviewer evaluated the learners on communication skills, crisis management algorithms, and implementation of appropriate skill sets. After each scenario, residents were debriefed on how to improve technique based on evaluation scores in areas of situational awareness, decision-making, communications and teamwork, and leadership. After the simulation, learners provided feedback on the simulation and this data was used to improve future simulations. The benefit of this cadaveric model is ease of set-up, cost-effectiveness, and reproducibility.

Introduction

Internal carotid artery injuries are a serious, albeit rare, complication of endoscopic endonasal approaches that require surgical dissection of tumor or vascular pathology adjacent to the cavernous sinus¹. Techniques and algorithms for managing this type of complication can only be obtained through realistic simulation². Wormald and colleagues have pioneered a training protocol for how to manage carotid injuries using a sheep model simulation³. They used a crush muscle patch with direct pressure over the injury site for hemostasis followed by direct vessel closure. This simulation has successfully improved outcomes in actual practice for multiple surgeons⁴. While beneficial, it has been shown that a cadaveric model of vascular injury is both more clinically relevant and cost-effective than using sheep and can be used for crisis management training⁵. Simulation training provides learners from neurosurgery and otolaryngology residencies the opportunity to develop algorithms for managing complications in real-time settings^5,6. What is important going forward is establishing a replicable model for broad training across institutions, and multidisciplinary collaboration within simulations.

The purpose of this study is to highlight the steps to produce a realistic cadaveric model for cavernous carotid artery injury and how to set up a multidisciplinary crisis management simulation. This model provides a method for neurosurgery and otolaryngology residents, in collaboration with anesthesia residents, to train on medical management of cavernous carotid injury. The benefits of this model are its reproducibility, cost-effectiveness, and ease of set-up. This study utilizes a cadaveric head model with perfusion pumps, which is more transportable and less-expensive than the whole body perfusion model developed by Pham and colleague⁷. It can be used innumerable times to train resident learners over the course of several sessions. The benefit of replication is that different clinical scenarios can be devised to train learners on important clinical considerations in a real-time context and to train residents on important steps for crisis management. The cadaveric head model has been combined with a simulated mannequin body to allow representation of clinical vital signs during the scenarios, and facilitate collaboration with anesthesia residents. The following protocol highlights a step-by-step procedure for how to set up the model.

Protocol

Cadaveric heads used in this protocol were acquired from the Oregon Health & Science University Body Donation Program. All methods described have been approved by the Oregon Health & Science University Institutional Review Board (IRB).

1. Head Preparation

1. Secure the fresh cadaveric head in the sink with the neck facing upwards.
2. Using a 1:100 anti-coagulant citrate dextrose solution, rinse out the jugular veins, vertebral, and carotid arteries bilaterally. Start by inserting a 5mm diameter cannula into the right jugular vein and secure the vessel around the cannula with a 5-inch hemostat clamp. Run the perfusion pump for 15 min. Rotate the tube to the left jugular vein and then carotid arteries and repeat the washout for 15 min at each vessel. Use a 3 mm diameter cannula for the vertebral arteries. The fluid should be clear, not bloody, at the end of the washout.
3. Let the heads dry overnight with the face upwards and the neck positioned at a 45° angle with a block positioned beneath it. Store in a cold room at 5 °C.
4. The following day, embed the head in 2 L of embalming solution and store it in a bucket with formalin fixative.
   Caution: embalming solution and formalin fixative are corrosive. Please wear protective equipment.

2. Tissue Dissection

1. Support the head with a block and position it in the neutral orientation avoiding over flexion or extension.
2. Use a zero degree endoscope of 4 mm diameter and 18 cm length.
3. Lateralize the middle turbinates and perform a bilateral sphenoidotomy. Make the incision at the articulation of the rostrum and vomer.
4. Clear the mucoperiosteum with a cottle elevator and remove the rostral bone bilaterally with a rongeur.
5. Drill flush to the floor of the sphenoid sinus and laterally to the medial orbital walls bilaterally with a high-speed drill and matchstick type drill head.

3. Preparing Cavernous Carotid Injury

1. Visualize the regions of the sella, clival structures, and cavernous carotid arteries. Remove the bone overlying the sella and cavernous carotid artery on the right with a rongeur.
   NOTE: Multiple options can be utilized for the carotid injury. Option 1: use an 11-blade knife to make a 3-mm laceration in the right internal carotid artery at the level of the genu. Option 2: puncture directly into the vessel with a nerve hook to produce a tear. Option 3: take a small piece of the vessel wall with a rongeur.

4. Perfusion Set-up

1. Insert a 5mm diameter cannula into the common carotid artery and secure with a 5-inch hemostat clamp.
2. Connect the cannula to a pressurized perfusion pump.
3. Prepare artificial blood consisting of red food coloring, water, and commercially purchased vampire blood [see Table of Materials]. Make artificial blood of the same relative density of real blood by using a 3:1 ratio of water to vampire blood. Add 2 drops of red food coloring for each 250 mL of water added.
   NOTE: Artificial blood may be reused for multiple simulations. 3 liters of blood should be prepared for each cadaveric head prior to the start of simulation. It can be stored at room temperature, but should be shaken and mixed prior to use.

5. Establish Realistic Bleeding

1. Set up an arterial line via the cannulated carotid artery.
2. Start the perfusion pump and measure actual mean arterial pressure (MAP) delivered to the cadaver head via an arterial line transducer and vital signs monitor. Visualize the realism of the carotid injury via endoscopic examination.
   NOTE: MAPs of 65-110 mm Hg should be used to produce realistic bleeding parameters depending on the clinical simulation scenario. Flow rate can be adjusted on the perfusion pump in order to reach physiologic MAPs.

6. Training Resident Learners

1. Pair one neurosurgery or ENT resident with one anesthesia resident for each of the simulation scenarios.
   1. Give resident teams approximately 10 min to complete each scenario, with a 10 min debrief (5 min specialty specific, 5 min interprofessional) after each scenario.
   2. Provide a specialty-specific debrief for 5 mins.
   3. Deliver interprofessional debrief to residents from both specialties for 5 mins.
2. Surgery residents
   NOTE: The following steps are to be carried out as instructed by the supervising faculty.
   1. Provide each learner with the same bony exposure, location, and size of cavernous carotid injury.
   2. Hold the endoscope and provide instructions to the surgery resident for how to manage vascular control. The residents work with the supervising faculty to manage the vascular injury using the 4-handed approach.
   3. Manage the scenario by 1) giving instructions to anesthesia residents to decrease blood pressure 2) asking for proximal vascular control, 3) using suction to guide the bleeding away from the endoscope, and 4) using a pituitary instrument to place a half cottonoid patty over the bleeding site and apply pressure. The bleeding must be adequately controlled with suction to visualize where to place the cottonoid patty.
   4. Exchange the cottonoid patty for a free muscle graft harvested from the temporalis muscle. Place the muscle directly over the right cavernous carotid artery injury with a good seal over the incision site. Blood should not be flowing into the cavernous cavity when the muscle patch is in place.
3. Anesthesia residents
   1. Connect the anesthesia station to a simulated mannequin that is connected to a laptop, patient monitor, anesthesia cart with drug tray, anesthesia machine, anesthesia monitor, IV poles, IV bag, and two functional IV units.
   2. Setup arterial line with pressure monitor.
   3. Provide anesthesia residents with instructions on use of provided materials, computer, and monitor before starting the simulation.
   4. Task anesthesia residents with medical management and working as a team with the surgical resident during the simulation scenarios.

7. Enhancing realism

1. Give learners different clinical scenarios for patients with varying comorbidities. The comorbid factors will cause changes in bleeding rate and pressure, which should be manually controlled by the faculty by adjusting the perfusion pump settings.
2. Task learners with technical and medical management challenges of catastrophic bleeding, and have learners appreciate the medical ramifications that develop.
3. Incorporate a simulated mannequin with the cadaveric head model to provide realistic feedback about changes in vital signs and patient stability.

8. Crisis management

1. Provide learners with cases of increasing complexity and have them manage multiple changes in vital signs while successfully maintaining vascular control.
   NOTE: Learners should effectively communicate so that team members address worsening patient status in a quick and effective manner.

9. Charting Outcomes

1. Provide learners with post-simulation surveys to assess the value of the simulation.
2. Facilitators should provide focused sessions with the individual learner to discuss ways to improve on communication and technique.
3. Provide pre- and post-simulation anatomy exams to assess knowledge gain.

Results

To successfully set-up the model it is important to select an appropriate perfusion pump and to properly prepare the cadaveric head. The pump should be fed into the internal carotid artery as depicted in Figure 1. Once the perfusion pump is set up, the steps outlined above should be employed to gain exposure to the cavernous carotid artery and to produce a realistic cavernous carotid injury. Visualization of the injury with subsequent placement of the muscle ...

Discussion

Carotid injury is a rare event but does occur in cases that involve the extended transphenoidal approach⁸. This approach is commonly used for pathology of the sella, suprasellar, parasellar, and clival spaces. Most skull base surgeons will face a carotid vascular injury at some point in their career. The expertise and confidence to handle such a dilemma can only be obtained through adequate training and appropriate crisis management simulation³. Valentine and colleagues hav...

Materials

Name	Company	Catalog Number	Comments
Anti-coagulant citrate dextose solution	Pierce Laboratories	117037
Embalming solution	Chemisphere
Formalin fixative	Chemisphere	B2915DR55
Zero degree endoscope (4mm and 18 cm length)	Karl Storz	H3-Z TH100
Penfield 1	Jarit	285-365
Kerrison rongeur	Aesculap	FM823R, 3mm/180 mm
Anspach eMax 2 Plus High Speed Drill	Depuy-Synthes	eMax2 plus
3 mm cutting ball	Depuy-Synthes
11-blade surgical blade	Bard-Parker	371111
Arterial cannula clamp
Arterial cannula	Instrument Design & Mfg. Co.	ART187-2-CT
Perfusion Pump	Belmont Instrument Corporation, Billerica, MA, USA	Belmont Fluid Management System 2000
Vampire blood	Forum Novelties, Inc., Melville, NY, USA	65368
Cottonoid surgical patties	Codman	80-1480
Laerdal SimMan	Laerdal Medical, Wappingers Falls, NY, USA	SimMan 3G
Laerdal SimMan Laptop	Laerdal Medical, Wappingers Falls, NY, USA	SimMan 3G
Pituitary rongeur	Aesculap	FF806R
Bayonet	Aesculap	BD 845
Suction - 7 and 10 FR	V. Mueller
IV poles	Pedigo
IV unit	Care Fusion	Alaris PC Unit
Pump modules	Care Fusion	Alaris Pump Module
Kit Arterial Line	Arrow International	RA-04020
Kit Pressure Monitor	ICU/BMP Inc	426340405
Fluid IV NaCl 0.9 1000CC)	Baxter Healthcare	2B1324X
Fluid IV lactated ringers 1000CC	Baxter Healthcare	2B2324X
Integra SL Anesthesia Machine	DRE	00104RS
AVS2 Remote Ventilator	DRE	409AVS2
Sigma Delta ISO Selectatec Vap Pour Fill	DRE	39001O
MP5 Bedside Monitor	Philips Healthcare	PMS-M8105a