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.
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