Gas Embolus
George A. Gregory, MD
University of California
San Francisco
Gas Embolus
• Introduction
• Serious, potentially lethal condition
• Venous or arterial
• Air bubbles block small blood vessels ➜ ischemia
• Most common causes
• Surgery
• Trauma – penetrating wound of chest, skull frcture
• Vascular interventions
• Barotrauma (mechanical ventilation, CPAP)
• SCUBA diving
• Decompression
Gas Embolus
• Mechanism
• Gas enters open vein ➜ vena cava ➜ right heart ➜ pulmonary circulation ➜
obstruction of right ventricle, pulmonary artery ➜ ⬆︎ RA and PA pressures ➜
R➜L shunt of gas ➜ cerebral stroke and/or cardiac ischemia and death
• Prevention and screening
• Aware of potential
• Patent foramen ovale
• ~20-25% or adults
• >30% of infants and children
• Bubble test
Bubble Test for Right-to-Left Shunt
Bubbles too small to cause harm
www.heartviews.org
Gas Embolus
• Mechanism
• Open blood vessel
• Pressure gradient favoring air entry
• Normally intravascular pressure exceeds atmospheric
• Normal or increased intravascular volume
• Gas does not enter
• Gas filtered in lung
• >5 cc/kg gas ➜ R➜L shunt through lungs
• When intravascular pressure is < atmospheric, gas can enter open vessel
• Vein above the heart
• Sitting craniotomy
• Head and neck surgery
• Orthopedic surgery
• Inserting and removing central venous catheters
Potentially Lethal Dose of Venous Gas
Adult Humans
3-5 cc/kg
300-500 cc of gas introduced at 100cc/s
Total volume 100-300 cc (heart size)
≦0.5 cc total if ➜ coronary artery
Infants
0.5cc/kg potentially lethal (epidural space
injection)
3-5 cc/kg (peripheral vein injection)
<0.2 cc if ➜ coronary artery
Potentially Lethal Dose of Venous Gas
Infants
0.5cc/kg potentially lethal (epidural space injection
3-5 cc/kg (peripheral vein injection)
<0.2 cc if ➜ coronary artery
Adverse Effects of Gas Embolism
Anesthesiology.pubs.asahq.org
Anesthesiology.pubs.asahq.or
Gas Embolus
• Catheter related
• Central venous, pulmonary artery, dialysis
• Can occur with insertion or removal
• Catheter related venous air embolism
• Fracture or disconnections
• Not occluding hub during insertion/removal (inhalation)
• Persistence of catheter tract after removal
• Cover with nonpermeable covering
• Deep inspiration during insertion/removal
• Valsalva or exhalation
• Hypovolemia
• Heart lower than vein (upright position during insertion)
Gas Embolism
• Types
• Venous
• Gas enters venous system and ➜ RA ➜ RV ➜ pulmonary circulation
• Arterial
• Produces ischemia of organs
• Requirements for gas embolism
• Direct communication between gas source and vasculature
• Pressure gradient – gas pressure > venous pressure
• Fowler’s position for neuro and ENT surgery, hip higher than heart
• Hypovolemia – subatmospheric pressures in vein
Gas Embolism
• Venous embolism – direct and indirect effects
• Direct
• Small bubbles ➜ pulmonary outflow tract , pulmonary arterioles, ➜obstructed
pulmonary microcirculation ➜ obstructive shock
• Lodge in microcirculation ➜ ⬇︎ blood flow and ⬆︎ vasoconstriction
• ⬆︎ PVR, ⬆︎ PAP, ⬆︎ RAP, ⬆︎ RVP ➜ ⬇︎ CO, myocardial ischemia, hypoxemia and RV failure
• Large bubbles ➜ pulmonary outflow tract obstruction (air lock) ➜ ⬆︎CVP, PBF, and, and
⬇︎ systemic blood pressure
• Indirect
• End organ damage
• In lungs air bubbles ➜ endothelial damage, ⬆︎ neutrophils, platelets, fibrin ➜ pulmonary
edema, bronchoconstriction, hypoxemia, ⬆︎ Vd/Vt, ⬇︎ CL
Gas Embolism
• Clinical features
• Venous air embolism
• History
• More severe
• Dyspnea
• Substernal chest pain
• Lightheadedness or dizziness
• Signs
• Gasping or coughing
• Sucking sound when gas is sucked into intravascular space
• Tachypnea, bradycardia, hypotension, wheezing, crackles, ⬆︎ JVP, hypoxemia, respiratory
failure
Gas Embolus
• Clinical features
• Arterial embolus
• Depends on organ affected
• Brain
• Changes in mental status
• Focal neurologic defect
• Loss of consciousness (severe cases)
• Coma
• Cardiac arrest
• Other signs
• Chest pain, wheezing, crepitus over superficial vessels, bubbles in retinal arteries, livedo
reticularis (skin)
Gas Embolism
• Laboratory
• ECG
• Sinus tachycardia, right heart strain, (peaked ”P” waves, RBBB, R axis deviation) air
embolism
• Non-specific ST-segment and T-wave changes, ST elevation or depression with ischemia
or infarction with arterial embolus
• Arterial blood gases
• Hypoxemia
• Hypercarbia
• Acidosis
• Laboratory tests
• ⬇︎ platelets, elevation of serum creatinine kinase activity
Gas Embolism
• Laboratory
• Imaging
• Chest X-Ray
• Rarely see gas in main PA, PA enlargement, intracardiac or intrahepatic gas
• V/Q scan
• Areas of poor perfusion
• Computed tomography
• Visualized air emboli in central veins (axillary/subclavian), RV, PA, heart. Intraparenchymal gas
and diffuse edema in brain
• MRI
• loculated gas in cerebral arteries and veins
• Pulmonary angiography
• Filling defects or vascular occlusion, evidence of vasoconstriction, delayed emptying of
pulmonary vessels
Gas Embolism
• Other
• Echocardiography
• Intraoperative
• Air in cardiac chambers and great veins
• RV dilation
• PA hypertension
• End-tidal gases
• ⬇︎ ETCO2 , ⬆︎ ET Nitrogen
• Pulmonary artery catheterization
• ⬆︎ in PA pressure
• ⬆︎ CVP
• ⬆︎ RVP
• ⬇︎ cardiac output and MAP
Gas Embolism
• Supportive therapy
• Oxygen
• 100%
• ⬆︎ rate of embolus resorption
• ⬆︎ partial pressure of oxygen
• ⬇︎ partial pressure of N2 in blood
• ⬆︎ diffusion of N2 from bubbles and ⬇︎ bubble size, ⬆︎ bubble resorption
• Mechanical ventilation
• Fluids and Vasopressors
• Give fluids to ⬆︎ CVP and ⬇︎ gas entry
• Maintain normal volume
• Vasopressors as needed to maintain cardiac function and arterial pressure
Gas Embolism
• Patient positioning
• Venous gas embolism
• Trendelenburg, or left lateral decubitus with head down
• RV outflow tract inferior to RV cavity ➜ gas ➜ apex from which gas is less likely to ➜ to lungs
• Arterial gas embolism
• Supine position
• RV pressure propels blood and gas into systemic circulation
• Trendelenburg position ➜ ⬆︎ cerebral edema
Gas Embolism
• Definitive therapy
• Hyperbaric oxygen
• Not readily available
• Appropriate for patients with hemodynamic and or cardiopulmonary compromise
• Initiate within 6 hours of embolization (may be some benefit up to 30 hours)
• Can reduce CNS injury by about 40%
• Partial pressure of oxygen 2000 mmHg
• ⬆︎ nitrogen gradient
• ⬇︎ bubble size and mechanical obstruction
• ⬆︎ oxygenation
• Manual removal of gas with catheter
• Not very effective
• Attempt if have CVP line
Gas Embolism
• Definitive therapy
• Closed chest massage
• Last ditch attempt
• May force gas into PA small vessels and ⬆︎︎ PBF
• Anticoagulation
• Ineffective
• Glucocorticoids
• Ineffective
• Lidocaine
• No proven effect in humans and may cause cardiac toxicity
Gas Embolism
• Prevention
• For patients at risk
• Avoid sitting position
• Avoid having surgery site above the heart if possible
• Avoid N2O
• Transthoracic or TEE
• Chest stethoscope
• Inject shaken saline rapidly
• Use lung protective ventilation
• CV catheter insertion and removal
• Trendelenburg position if possible
• Occlude hub, remove gas before injection of drugs
• Valsalva when removing lines
Gas Embolism
• Differential diagnosis
• Acute pulmonary decompensation
• Pulmonary embolism
• Pneumothorax
• Bronchospasm
• Pulmonary edema
• Acute cardiovascular decompensation
• Hypovolemia, cardiogenic shock, myocardial shock, septic shock, amniotic embolism, fat
embolism
• Acute neurological decompensation
• Cerebral perfusion, stroke, intracranial hemorrhage, hypoxic brain injury, head trauma,
metabolic disorders
Gas Embolism
• Diagnosis
• First administer oxygen, position patient and apply life supportive measures
• 100% oxygen to ⬆︎ oxygenation and reduce size of bubble
• Is made by demonstrating gas in intravascular space or organs
• Gas absorbed, therefore, may miss it
• Then get tests
• CBC, CPK, troponin-I and T
• Blood gases, pH
• Chest X-ray
• ECG
• TEE (cardiac gas), CT, Transcranial doppler (cerebral gas), Capnography (⬆︎CO2,⬇︎ N2)
• DDx – PE, massive blood loss, circulatory arrest, disconnection of circuit
Gas Embolism
• Treatment
• Airway, breathing, circulation stabilization
• High-flow oxygen (100%), MV, volume resuscitation, vasopressors, advanced life support
• Position in left lateral decubitus ± Trendelenburg; supine if arterial embolus
• Hyperbaric oxygen
• Adequate IVs, CVP?
• Vasopressors PRN
• Hemodynamically unstable patients
• Hypotension, fluid,vasopressors
• Aggressive support
• Vasopressors, Hyperbaric oxygen
• Neurologically unstable
• Supportive and definitive therapy (hyperbaric oxygen)
Case
• A 2 month-old baby girl was transferred to Children’s Hospital 2 from Dong Nai
Children’s Hospital on Feb 21st 2019 due to intraventricular hemorrhage.
• The day before admission, the baby had mild fever at 38oC
• At 4am at the day of admission, the baby suddenly cried out while sleeping. She was
fretful, pale, and spastic continuously => went to Dong Nai Children’s Hospital.
• She is a second child, term, vaginal delivery, birthweight 3.2kg. Unknown vitamin K
injection after birth. Nutrition: breast milk and formula milk.
• No history of any disease or trauma.
• Family history: normal.
• At Dong Nai Children’s Hospital: her status: continuously spastic extremities, pale,
warm hands, CRT <2s, pulse 200bpm, RR 100cycles/min, To 40oC, NIBP 106/36
mmHg (109/65/80), MAP 60mmHg, bulging anterior fontanel.
• Hct 20% (fluid given?), WBC 18.4K/uL, Neu 10.7K/uL, PLT 317K/uL, CRP 2mg/L
• PT 16.3s, ApTT 32.6s, Fibrinogen 2.44g/L. Glycemia 116 mg%.
Gas Embolism Case
• Surgical History
• Insertion of ventricular drain
• Attempted embolization of aneurysm
• Scheduled for surgical treatment of aneurysm
• Anesthetic evaluation:
- Increased ICP was reduced with treatment, EVD with 50ml/day, still had brain edema on CT
scan performed on Feb 28th , pupils size was equal and reactive with light, flat fontanel
(EVD).
- Hypertension during stay in ICU, unknown BP during stay in neurosurgery department.
- Hyponatremia had happened few days ago would make brain injury. Seizures
- Pneumonia was on treatment, fever everyday (infection, blood in CSF), however, CRP and
WBC were normal
- ASA III
Risks of surgery:
- Increased ICP again due to ventilation, blood pressure or hemorrhage.
- Bleeding due to surgery or aneurysmal rupture.
- Hyponatremia or hypernatremia
- Acidosis due to hyperchloremia or hypoventilation.
- Hypoglycemia ( small baby).
- Mechanical ventilation after surgery, pneumonia might be severe later.
• Prepare for surgery:
- Order 1 unit of PRBCs
- Management ICP: adequate ventilation, keep MAP during surgery ≧ MAP
when the child arrived the operating room with noradrenaline and fluid, keep
normal serum sodium, Hgb 8-10g/dL
- Fluid: Lactate ringer if Na+ >140mmol/L , NaCl 0.9% if Na+ <140mmol/L
- Adequate analgesia when intubation and surgery
- Keep normothermia with blanket and fluid warmer device, normal glycemia
with glucose solution if needed.
- Monitor: IBP, SpO2, To , EtCO2, ECG, urinary output, check blood gas and
glycemia after induction and after 1-2hrs if needed.
- Blood volume 5.7 kg x 85ml = 485ml, Hctint = 35.3%,
- Blood loss 10%, => Hct= 31.5%, Blood loss 20% => Hct 28%
- Blood loss 30% => Hct= 24.8%
• The child arrived the operating room at 8:30 Mar 8th 2019
• Fasting time 6hrs => fluid deficit= 137ml
- Total time: 5hrs 30mins.
- Fluid: Lactate ringer 500ml, NaCl 0.9% 600ml, transfusion 100ml => 38ml/kg/hr
- Blood loss: 150ml , urine 350ml (total = 500ml (>1 BV), ICP? Did surgeon complain?
- Using noradrenaline after induction to keep high BP, BP at arrival 70/40mmHg, MAP
50mmHg.
- Checked blood gas and blood glucose 3 times, after induction, the end of surgery and before
opening dura.
- After induction: glycemia 131mg%, FiO2 50%, EtCO2 32 mmHg pH 7.43 , pO2 104mmHg
pCO2 39mmHg, BE 0.8mmol/L, HCO3- 25.2mmol/L, AaDO2 213mmHg
Hct 31%, Hgb 10.4g/dL
- After opening dura, SpO2 suddenly decreased from 100% to 80-85% with FiO2 50%, at that
time, MAP ~ 45-50 mmHg, pulse 125-130bpm, EtCO2 decreased from 30 to 24mmHg. ECG
did not show any abnormal, heart sound: did not find any abnormal
managed: FiO2 100%, increased noradrenaline to increase MAP> 50mmHg, check blood
gas.
R ➜ L shunt?
• 2nd blood gas: FiO2 100%, EtCO2 22 mmHg, pH 7.42, pO2 107mmHg, pCO2 37mmHg,
BE -1.2 mmol/L, HCO3- 23.2 mmol/L, AaDO2 583mmHg, SO2 97%, (nitrogen?)
• 2nd glycemia 245 mg%. Hgb 7.3g/dL, Hct 22%, Na+ 143mmol/L, K+ 3.9mmol/L, Ca++
1.3mmol/L
Transfusion with PRBCs, FiO2 100%, keep MAP > 50mmHg with noradrenaline
0.2ug/kg/min.
Low SpO2 happened for 1hrs, then could keep at 100% with FiO2 100%.
At end of surgery, SpO2 could keep at 100% when decreasing FiO2 to 50%.
Suspicion: 1. air embolism
2. low oxygen delivery due to low Hgb 7.4g/dL
• 3rd blood gas ( the end of surgery): FiO2 50%, EtCO2 28mmHg, pH 7.33, pO2 269 mmHg,
pCO2 41 mmHg, BE -4.2mmol/L, HCO3- 21.4 mmol/L, AaDO2 87.5mmHg
• Glycemia: 234mg%, Na+ 142 mmol/L, K+ 3.0mmol/L, Ca++ 1.47 mmol/L
• Hct 32%, Hgb 10.7g/dL
• Surgery: removed the aneurysm with size 2x2 cm. Inserted EVD catheter.
Gas Embolus
• Treatment when embolus suspected
• Interrupt surgery
• Flood field with saline immediately
• Hold 20 cmH2O airway pressure for 5-10 seconds
• Observe for blood from vein (skull) and close with bone wax
• Lower surgical site below heart if possible
• Trendelenburg position
• Support CV system
• Fluid to increase CVP
• Careful of CHF
• Vasopressors
• 20:30 pulse 160bpm, BP 108/60 mmHg, MAP 76mmHg => stopped noradrenaline
• Blood gas: FiO2 40%, pH 7.43, pO2 162mmHg, pCO2 21.5mmHg (about 50%
reduction in CPF), BE -8.9mmol/L, HCO3- 14.8mmol/L, AaDO2 95.9mmHg.
• Na+ 134mmol/L, K+ 3.6mmol/L, Cl- 112mmol/L, Catt 2.05mmol/L (AIG 7)
• PT 18.6s, PT 60%, APTT 126s, INR 1.4, Fibrinogen 1.47g/L => FFP transfusion.
• EVD 0ml/16hr, urine 180ml/ 16hr ( ~2ml/kg/hr), fluid balance (+) 426ml – 25 ml/kg =
143 ml ECFV in 2 y old)
• Day 1st post-operation
- Eyes opened, weak contact, edema, pink, warm, pulse 140-160bpm, MAP 60-77mmHg, flat
fontanel.
- Kept ventilator, fluid with (NaCl 0.9% + CaCl2 10% + KCl 10% + MgSO4 15%) infusion
25ml/hr, antibiotics Levofloxaxin, meropenem, sedation with midazolam
• Kept MAP ≧65mmHg
• Hgb 8g/dL, PLT 239K/uL, WBC 5.14K/uL=> transfusion
• Na+ 134mmol/L, K+ 3mmol/L, Cl- 109mmol/L, Catt 2.02 mmol/L
• FiO2 40%, pH 7.55, pCO2 15.8 mmHg (CBF ⬇︎about 50%), pO2 178mmHg, BE -8.9mmol/L,
HCO3- 13.5mmol/L (AIG 3.3 – albumin)
• 11:30 blood gas: pH 7.478, pCO2 28.5mmHg, pO2 183mmHg, BE-2.9mmol/L, HCO320.7mmol/L
• 14:00, fever 38.6o C=> added vancomycin,
• hypoglycemia several times=> glucose 30% 11ml IV, started milk via oral gastric tube 50ml x
8/day.
• Infusion NaCl 0.9% 10ml/kg/hr for 2hrs when urine output <1ml/kg/hr ( 2 times).
• EVD 77ml/24hrs dark yellow fluid, urine 116ml/hrs (0.9ml/kg/hr), fluid balance (+)122ml
• Day 2nd post-operation
- awaked, moved well, GCS E4M5Ve , flat fontanel => stopped sedation
- 14:00 Na+ 129 mmol/L, K 2.8mmol/L, Cl-108mmol//L, Ca 1.95mmol/L
pH 7.4, pCO2 28.9mmHg, pO2 204mmHg, BE -5.9mmol/L, HCO318.5mmol/L
AaDO2 46.5mmHg. => decreased Pi from 16 to 14 cmH2O.
- Kept fluid, antibiotics the same as the day before, milk 70mlx 8/day.
- 17:00 FiO2 40%, pH 7.4, pCO2 21.5mmHg, pO2 207mmHg, BE—8.7mmol/L
HCO3- 13.9mmol/L => decreased FiO2 30%, Pi 13cmH2O.
- 19:30 MAP 62mmHg, pulse 118bpm => noradrenaline 0.05ug/kg/min
- 22:00 pulse 110 bpm, MAP 69mmHg, FiO2 30%, pH 7.3, pCO2 30mmHg,
pO2 146mmHg, BE -6.9mmol/L, HCO3- 18mmol/L, AaDO2 30mmHg.
- EVD 37ml/24hrs dark red fluid, urine 5ml/kg/hr, fluid balance (+) 100ml
• Day 3rd post-operation
- Awaked E2-3M5Ve, , flat fontanel, pulse 120 bpm, MAP >65mmHg, warm, no fever,
had spontaneous breaths
- Stopped fluid infusion, milk 120ml x8/day, same antibiotics, noradrenaline
0.03ug/kg/min => decreased then stopped. Ventilator: AC mode => SIMV mode.
- 11:00 pH 7.46, pCO2 30.5mmHg, pO2 174mmHg, BE –1.9mmol/L, HCO321mmol/L, Na+ 124mmol/L, K+ 3.3mmol/L. Cl- 99mmol/L => NaCl 3% 44ml/hr.
Correct slowly.
- 18:00 Na+ 130 mmol/L, K+ 3.4 mmol/L, Cl-103mmol/L
- Fluid balance (+) 173ml, urine 7ml/kg/hr, EVD 41ml/24hrs
• Day 4th post-operation
- awaked, GCS 10 points, MAP 82mmHg, many spontaneous breaths => SIMV to
SPONT mode
- Na+ 135mmol/L, K+ 2.9mmol/L, Cl- 112mmol/L
- Treatment: milk 120ml x8/day, antibiotics, phenobarbital.
- EVD 23ml/24hr, urine 5.7ml/kg/hr, fluid balance (+) 150ml.
• Day 5th post-operation
- Awaked, had contact, good movement, GCS 10, MAP 70-90mmHg, pulse 140179bpm,
- , BE -2.1 mmol/L, HCO3- 21.2mmol/L, AaDO2 55mmHg
- 21:00 FiO2 21%, pH 7.49, pCO2 28mmHg, pO2 116mmHg, BE -1.6mmol/L,
HCO3- 21mmol/L
- Na+ 138mmol/L, K+2.9mmol/L, Cl- 119mmol/L, Ca 1.54mmol/L
- Fluid balance -33ml, urine 7.6ml/kg/hr, blocked EVD.
• Day 6th post-operation
- awaked, pink with room air, pulse 140bpm, warm, flat fontanel,
- Na+ 136mmol/L, K+ 3.5mmol/L, Cl- 111mol/L, Catt 1.99mmol/L
- Transferred to neurosurgery department
• Day 7th – 19th post-operation:
- Continued treatment antibiotics for pneumonia and sepsis ( 23days)
- Day 13th : performed DSA again: no new aneurysm found.
- Discharged on day 19th post-operation.