Kimitian, Stephen MD; Aguilar, David MD; Rudy, Sally RN, BSN; Henry, Jody BS; Sinz, Elizabeth H MD
SECTION 1: DEMOGRAPHICS
Patient Name: Bolivia, Ephraim
Scenario Name: Simulation of Intraoperative Venous Air Embolism
Date Of Development: March 5, 2004
Appropriate for following learning groups:
Targeted Specialties: Anesthesiology, Nurse Anesthesia, Surgery
—With some modification: Critical Care, Emergency Medicine, Obstetrics
Residents (PGY): 1 2 3 4 5 6 7
Medical Students (yr): 1 2 3 4
Nursing Students (yr): 1 2
SECTION 2: CURRICULAR INFORMATION
Venous air embolism (VAE) is an uncommon, potentially lethal complication of many procedures. The purpose of this simulation is to demonstrate methods for recognition of VAE and practice intraoperative management when it occurs.
Based on ACGME Core Competencies:
1. Medical Knowledge
Trainee will correctly answer multiple-choice questions to quickly assess fund of knowledge about the etiology and pathophysiology of VAE. Trainee will correctly diagnose and treat VAE in a simulated operating room scenario. Trainee will explain the implications of a patent foramen ovale in the patient who has a VAE.
2. Patient Care
Trainee will recognize deteriorating physiology in a simulated operative setting and properly manage the simulated patient’s hemodynamic instability. The trainee will list an appropriate differential diagnosis for hypotension with decreased end-tidal carbon dioxide;
3. Practice-based Learning and Improvement
Trainee will self-assess performance following completion of simulation. Trainee will identify various procedures associated with the risk of VAE and identify areas of clinical practice where this experience can be applied. Trainee will be provided with resources for further study.
4. Interpersonal and Communication Skills
Trainee will demonstrate appropriate “turnover” of patient when accepting the case, including informing the operating room (OR) team that the care is being transferred. During the simulated crisis the trainee will promptly and effectively communicate with other OR personnel, assuming the position of CRM team leader.
Trainee will demonstrate appropriate professional behavior during simulation. Trainee will maintain composure during crisis without engaging in conflict with the surgical staff. Trainee will appropriately self-reflect during debriefing and appropriately accept feedback.
6. Systems-based Practice
Trainee will appropriately request assistance and use available resources when needed during simulated crisis. Trainee will correctly identify other procedures and situations that put patients at risk for VAE and will propose methods to reduce this risk.
* Power Point presentation (available online)
* VAE summary handout by Keith Ruskin, MD (http://anestit.unipa.it/gta/vae.html)
* Similar published case report1
* Available recent review articles (See bibliography)
Trainee assessment during simulated case is based on:
1. Identification and communication of patient’s deteriorating physiologic state
2. Rapid identification and treatment of venous air embolism including:
a. Changing patient position: surgical site is below the level of the heart or left lateral tilt
b. Request that surgeon flood the surgical field with saline
c. Nitrous oxide is discontinued and 100% FiO2 is initiated
d. Aspiration of air from the central line
3. Appropriate communication and leadership of team during resuscitation
4. Active participation in debriefing following simulation and genuine interest in performance improvement
5. Written test assessment for knowledge: trainee should answer all questions correctly
Although there is no “pass” or “fail” grading upon completion of the simulation, if the trainee requires excessive prompting by the surgeon/actor, this would indicate the need for further remediation/educating.
SECTION 3: PREPARATION
1. Doppler recording – normal (Appendix C)
2. Doppler recording – embolism (Appendix D)
3. Patient’s preoperative assessment (Appendix E)
4. Anesthesia record with normal induction and course
2. Circulating nurse
Our simulated patient is a 62-year-old male for posterior fossa craniotomy for tumor. His past medical history that includes hypertension controlled with losartan (Cozaar) and chlorothiazide (Diuril) as well as gastroesophageal reflux disease, moderately controlled with ranitidine (Zantac). He also takes one baby aspirin per day, but this has been held for the past 2 weeks. He recently began experiencing progressively worsening headaches over the last 2 months, with no vision changes, no changes in mental status, and no loss of consciousness. CT imaging demonstrates a mass in his posterior fossa. He was started on prednisone following diagnosis. On physical examination, he is awake, alert, and oriented to person, place, and time, no headaches since starting prednisone. Airway, cardiac, and pulmonary exams were normal. No neurologic deficits were elicited.
Prior to arrival to the operating room, an 18-g peripheral intravenous line was placed in the left upper extremity. Two milligrams of Midazolam was given. Upon arrival to the operating room, standard monitors were placed and the patient was preoxygenated with 100% O2. Induction agents were fentanyl, sodium thiopental, and vecuronium. Direct laryngoscopy with a Miller no. 2 blade was performed, revealing a grade 2 view. A 7.5-endotracheal tube (ETT) was placed easily, and end-tidal carbon dioxide (ETCO2) and bilateral breath sounds were confirmed. A mixture of oxygen, nitrous oxide, and isoflurane was used for maintenance of anesthesia. A left radial intra-arterial catheter was placed. A multiorifice catheter was placed in the right subclavian vein and positioned using electrocardiogram (ECG) observation. The tip of the catheter is in the right atrium. The patient was placed in the sitting position and pressure points were padded. There was no physiologic response surgical skin incision. Per the surgeon’s request, 50 g of mannitol was administered at the time of skin incision. The patient has been stable and urine output has been brisk.
Background And Briefing Information for Facilitator/Coordinator’s Eyes Only
We used the Medical Education Technologies (METI) Human Patient Simulator (HPS) in the sitting position completely draped, including intravenous (IV) access. One may consider placing a picture of an open brain between the drapes to mimic the surgical field. On transfer of patient information, mention the IV access in passing, in the middle of sign out. (Dan Raemer’s rule: People only listen for the first one and a half sentences.) This provides an opportunity for the trainee to request clarification and determine how they would get to the access if needed. Prior to trainee’s arrival into simulation area, the HPS should already be anesthetized, mechanically ventilated, and paralyzed. Surgery is already underway. The normal precordial Doppler sounds should be playing continuously. Have syringes already labeled with pertinent drugs if desired. Once the trainee appears settled, the surgeon will request an additional bolus dose of 12.5 g mannitol. If air embolism sounds are coordinated with request for mannitol, this will provide an additional distractor. Subsequently, air embolus simulation should be initiated.
There should be four endpoints for completion of the simulation: 1) change position of the patient so incision site is below the level of the heart; 2) flood the surgical field with saline; 3) discontinue nitrous oxide (N2O), and modify anesthetic; and 4) aspiration of air from central line (may consider injecting approximately 10 mL or more of air into central line that has connections to permit greater than 20 mL within the “venous system” that ends in a small bucket filled with red-colored water for realism.). Our central line simulation consisted of a hyperalimentation “Y” set by Walrus, connected to extension tubing (20 mL volume within tubing) resting in small bucket filled with red-colored water. After completion of the 4 endpoints, recovery should occur.
This is followed by a debriefing session.
PATIENT DATA BACKGROUND AND BASELINE STATE
This is a 62-year-old male with a past medical history that includes hypertension controlled with losartan and chlorothiazide, as well as gastroesophageal reflux disease, moderately controlled with ranitidine. He was also taking one baby aspirin per day, but this was held for the past 2 weeks. He began experiencing progressively worsening headaches over the last 2 months, with no vision changes, no changes in mental status, and no loss of consciousness. Computed tomography imaging demonstrated a mass located in the posterior fossa. He was placed on prednisone following diagnosis. He now is undergoing a craniotomy in the sitting position to excise and diagnose the intercranial mass.
Review of Systems
CNS: Frequent headaches until starting prednisone. No neurologic deficits noted.
Cardiovascular: Walks a few miles 3 times a week. Sleeps supine. Patent is able to climb a flight of stairs without chest pain or shortness of breath.
Pulmonary: Patient has no complaints of shortness of breath, dyspnea, or hemoptysis.
Renal/hepatic: No problems noted.
Endocrine: No problems noted.
Heme/coag: No problems noted.
Current Medications and Allergies
Aspirin 81 mg PO qd: held for 2 weeks prior to surgery
The patient has no known drug allergies.
General: Awake, alert, and oriented to person, place, and time, in no apparent distress
Weight, height: 70 kg; 5 feet 10 inches
Vital signs: BP 136/83, HR 76, Resp 16, Temperature 36.3, SpO2 99
Airway: Airway examination demonstrated a four finger-breath mouth opening, intact dentition with a chip on the #9 incisor, Mallampati class II airway, a four finger-breath thyromental distance, a mobile mandible and trachea, and full range of motion of his neck
Lungs: All lung fields were clear to auscultation
Heart: A regular rate and rhythm was noted on precordial examination with no murmurs, gallops or rubs noted
Laboratory, Radiology, and Other Relevant Studies
CXR: No acute cardiopulmonary abnormalities
EKG: Sinus rhythm at 74 beats/min, no areas of ischemia noted
Teacher/operator must use appropriate judgment regarding successful completion of all endpoints. Trainees may perform maneuvers in different order or may miss key maneuvers. Decision to provide “assistance” to the trainee or to allow the patient to continue to deteriorate or die will be at the instructor’s discretion.
This scenario can be modified to mimic VAE from other sources such as a patient in the intensive care unit or emergency department with a central venous access catheter that becomes detached as he is repositioned upright, perhaps for a chest x-ray, thereby allowing air entrainment into his venous system as he takes a deep breath. The physiology will be the same as will the treatment. It is unlikely that there would be a precordial doppler in this circumstance. The event can also be described in the context of a Cesarian section. For this case, it would be uncommon to have a precordial Doppler or central venous access. The treatment would therefore not include withdrawal of air; however, the physiology and other therapies would be the same.
Other patient simulators, such as the Simman by Laerdal, could be used targeting the same physiology as described above.
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Multiple Choice Questions
A. If only 1, 2, and 3 are correct
B. If only 1 and 3 are correct
C. If only 2 and 4 are correct
D. If only 4 is correct
E. If all are correct
Question 1: Immediate manifestations of venous air embolism include:
1. Alteration in heart sounds detected by precordial Doppler
2. Decrease in expired carbon dioxide by capnography
3. Increase in expired nitrogen measured by massspectroscopy
4. Decrease in oxygen saturation indicated by oximetry
Question 2: The degree of compromise to the patient with venous air embolism is related to the:
1. Amount of air entrained
2. Site of air entry
3. Rate of air entry
4. Type of procedure
Question 3: Procedures associated with a very high incidence of clinically significant venous air embolism include:
1. Sitting craniotomy
2. Burr Hole
3. Cesarian section
4. Laparoscopic cholecystectomy
Single Best Answer
Question 4: Which of the following has the highest sensitivity detecting VAE?
B. Arterial blood pressure
C. Central venous pressure
D. Precordial Doppler
E. Transesophageal echocardiography
F. Transesophageal stethoscope
Question 5: Benefits of a precordial Doppler for detecting air embolus include all of the following EXCEPT:
A. Sensitive for detecting air
D. Specific for amount of air
E. Easy to use
Question 6: Most venous air emboli go to which vascular bed:
Question 7: Measures to reduce the chance of venous air embolism include all of the following EXCEPT:
B. Lowering the level of the operative site
C. Volume loading
D. Controlled ventilation
E. Meticulous technique
Question 8: Given the following tracing, which portion shows the tip of the multiorifice catheter in optimal position for extraction of air when venous air embolism is suspected?
CHOOSE ALL THAT ARE CORRECT
Question 9: Which of the following maneuvers are appropriate in the initial management of significant VAE?
Initiate 100% oxygen
Request that the surgeon pack the wound withgauze
Administer fluid bolus
Withdraw air from arterial catheter
Apply cold compresses to neck veins
Answers: A, B, D
Question 10: Other pathophysiology to rule out when considering a possible venous air embolism includes:
Answers: A, B, D, E
Appendix Table 1. Pa...Image Tools
1. Sharma, A, Uppal, R. Catastrophic presentation of venous air embolism – a case report. Indian Journal of Anesthesia 2002;46:403-404