FATAL AIR EMBOLISM DURING ENDORESECTION OF CHOROIDAL MELANOMA James C. Rice, FCOphth (SA),* Linda Liebenberg, MMedPath (Foren),† Raoul P. Scholtz, FCOphth (SA), Gregory Torr, FCA
Purpose: To describe a case of intraoperative mortality because of air embolism during resection of a choroidal melanoma by pars plana vitrectomy. Methods: Retrospective interventional case report. Results: A 69-year-old man died unexpectedly at the time of pars plana vitrectomy. The operative technique involved the use of high-pressure air (60 mmHg) in the presence of traumatically exposed choroidal vasculature. Autopsy revealed a large air embolus in the right ventricle, which resulted in sudden cardiovascular collapse. Conclusion: Air embolism is a rare complication of ophthalmic surgery. Infusion of air in the presence of traumatically exposed choroidal vasculature exposes the patient to the risk of air embolism. Ophthalmic surgeons and anesthetists should be aware of the possibility of air embolism during certain ophthalmic procedures, and appropriate intraoperative monitoring should be considered. RETINAL CASES & BRIEF REPORTS 8:127–129, 2014
From the Departments of *Ophthalmology, and †Forensic Pathology, Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa.
nosis of peripheral vascular disease and a high body mass index of 39, he was considered to be in an optimized condition for surgery and had no electrocardiogram (ECG) or stress ECG features of myocardial ischemia. Anesthetic induction was uneventful, and maintenance was achieved with sevoflurane, nitrous oxide, and oxygen. One and a half hours into the procedure, the patient’s end-tidal carbon dioxide and oxygen saturation dropped precipitously (Figure 3). A slow ventricular rhythm turned into ventricular
Case Report A 69-year-old man with a choroidal melanoma of the right eye underwent elective general anesthesia for the purpose of transvitreal resection of the tumor and intended brachytherapy consolidation of the tumor bed. The tumor was 12.57 mm high with a base of 10.60 mm · 10.76 mm located inferonasal to the optic disk (Figure 1). It had a typical collar-stud configuration on ultrasound (Figure 2). Phacoemulsification and lens implantation was followed by 20 gauge, 3 port, pars plana vitrectomy. The tumor had invaded the overlying retina, and a localized retinectomy was therefore performed as part of the resection. Intraoperative hemorrhage made visualization difficult. To improve visualization, the resection was continued under an air infusion at pressures of up to 60 mmHg. This maintained the optics of the globe and helped tamponade the sites of hemorrhage. The patient was known to have controlled hypertension and noninsulin-dependent diabetes mellitus for 6 years. Despite a diagNone of the authors have any financial/conflicting interests to disclose. Reprint requests: James C. Rice, FCOphth (SA), Department of Ophthalmology, Groote Schuur Hospital, University of Cape Town, Observatory, Cape Town 7925, South Africa; e-mail: [email protected]
Fig. 1. Fundus photograph of the inferonasal tumor.
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Fig. 2. B-scan ultrasound demonstrating typical “collar-stud” appearance.
fibrillation, and resuscitation was unsuccessful. Pulmonary embolus or myocardial infarction was initially suspected. Lodox x-ray (Lodox Systems, Johannesburg, South Africa) before autopsy revealed the presence of air in the right ventricle of the heart (Figure 4). At autopsy, the heart was buoyant, and when opened under water, released a large number of air bubbles from the right ventricle. No air was found in the left ventricle. The fossa ovale was closed, and there was no ventricular septum defect. No pulmonary thromboembolism or features of myocardial infarction could be found. There were no air bubbles in the infusion line, and a diagnosis of air embolism from the ocular surgical site was made.
Discussion Vascular air embolism (VAE) may be defined as the entrainment of air or gas from the operative field into
Fig. 3. Intraoperative graphs demonstrating precipitous drop in end-tidal CO2 (Figure 3A) and oxygen saturation (Figure 3B).
the venous or arterial vasculature producing systemic effects.1 A review article on this topic was recently published by Gordy and Rowell.2 The condition is more commonly described in procedures, in which the surgical field is above the level of the heart, such as neurosurgical procedures performed in a sitting position. The resultant gravitational gradient facilitates entrainment of air into the vasculature. Modern operative procedures, in which gas is used under pressure such as laparoscopic surgery or gastrointestinal endoscopy, provide an alternative pathophysiology of entrainment. Air–fluid exchange, in which the vitreous compartment is filled with air under pressure, is a common technique in vitreoretinal surgery and under certain circumstances may increase the risk of VAE. Intraoperative VAE is rare during eye surgery but has been suspected as the possible cause of cardiovascular instability during the pars plana vitrectomy for retinal detachment in a 55-year-old man3 and during the removal of a posterior intraocular foreign body in a 17-month-old child.4 Both patients recovered uneventfully. An ultimately fatal case was reported by Dermigny et al5 after removal of an intraocular foreign body. In all cases, air was infused under pressure. In the retinal detachment case, the report of an “abnormally swollen” choroid suggests that the infusion line lay within the choroidal compartment, and infusion occurred into the choroidal circulation. In the other cases (and ours), the air was most likely entrained into the traumatically exposed vasculature. The surgical technique of endoresection involves removal of all choroidal tissue in the region of the tumor, ideally resecting down to bare sclera. Open choroidal and tumor vasculature are potentially exposed to infused air. Ampulliform dilatation of the vortex veins occurs just before the vessels enter the sclera and widens the vascular access. Attachment to
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Fig. 4. Preautopsy Lodox x-ray showing air within the heart shadow.
the scleral opening may also prevent collapse of these vessels. In addition, a reduction in vessel wall elasticity with age6 may contribute to maintaining vessel patency during surgery. This setting may therefore pose a particular risk for entrainment of air. The diameter of the choroidal veins varies from 300 mm to 2 mm at the ampulla. Ledowski et al3 have calculated that, according to the Hagen–Poisseuille law, potentially lethal air flow of 1,600 mL/minute into the choroidal circulation is theoretically possible with a 20-gauge infusion cannula and an air infusion pressure of 40 mmHg. Although the assumptions in this model are not all met, it is still likely that a significant volume of air may be entrained. The lethal volume of air for an adult has been estimated at 200 mL to 300 mL,7 but the rate of entrainment is also critical because larger volumes may be tolerated if entrained over long periods.1 We used infusion pressures of up to 60 mmHg. It is also likely that the use of nitrous oxide in our case exacerbated the hemodynamic effects of the embolus.8,9 The pathophysiological effect of the VAE largely depends on the volume of gas that accumulates in the right ventricle. A large embolus (as occurred in our patient) results in a complete outflow obstruction from the right ventricle, rapid right-sided heart failure, and immediate cardiovascular collapse,1 as evidenced by the precipitous decrease in end-tidal CO2 and arterial oxygen saturation (Figure 3). The main aim of this report is to raise awareness of the possibility of VAE during eye surgery, where the choroidal vascular is exposed, and air infusion is used either to improve visualization or as part of fluid removal before the insertion of silicone oil. Longer
exposure and high infusion pressures are likely to increase the risk of VAE. Endoresection of choroidal melanoma is a rare procedure, and the authors are not aware of other cases of VAE in this setting. As a preventative measure, we would suggest considering ligation of the vortex vein(s) draining the excision site. Although vortex vein ligation may precipitate an acute choroidal hemorrhage, we believe it may prove effective at preventing VAE without compromising the outcome of the procedure. Methods of intraoperative detection of VAE are discussed in detail by Mirski et al.1 High levels of vigilance and awareness are always required. Transoesophageal echocardiography is the most sensitive monitoring technique but is invasive and requires a high level of expertise. It can detect as little as 0.02 mL/kg of air. The most sensitive noninvasive monitor is precordial Doppler, which is able to detect as little as 0.25 mL (0.05 mL/kg) of air. This device produces a characteristic “mill-wheel” murmur indicating cardiovascular decompensation. Mirski et al suggest that precordial Doppler can be used in cases of open vasculature in the presence of air or gas infusion (e.g., laparoscopic procedures), and we suggest that these monitoring techniques also be considered in certain cases of ophthalmic surgery. Key words: air embolism, choroidal melanoma, endoresection. References 1. Mirski MA, Lele AV, Fitzsimmons L, Toung TJ. Diagnosis and treatment of vascular air embolism. Anesthesiology 2007;106: 164–177. 2. Gordy S, Rowell S. Vascular air embolism. Int J Crit Illn Inj Sci 2013;3:73–76. 3. Ledowski T, Kiese F, Jeglin S, Scholz J. Possible air embolism during eye surgery. Anesth Analg 2005;100:1651–1652. 4. Ruest P, Aroichane M, Cordahi G, Bureau N. Possible venous air embolism during open eye surgery in a child. Can J Anaesth 2007;54:840–844. 5. Dermigny F, Daelman F, Guinot P, et al. Fatal air embolism during open eye surgery [in French]. Ann Fr Anesth Reanim 2008;27:840–842. 6. Bron AJ, Wolff E, Tripathi RC, Tripathi BJ, eds. Wolff’s Anatomy of the Eye and Orbit. 8th ed. London, United Kingdom: Chapman & Hall; 1998:405–410. 7. Toung TJ, Rossberg MI, Hutchins GM. Volume of air in a lethal venous air embolism. Anesthesiology 2001;94:360–361. 8. Kyttä J, Tanskanen P, Randell T. Comparison of the effects of controlled ventilation with 100% oxygen, 50% oxygen in nitrogen, and 50% oxygen in nitrous oxide on responses to venous air embolism in pigs. Br J Anaesth 1996;77:658–661. 9. Junghans T, Böhm B, Meyer E. Influence of nitrous oxide anesthesia on venous gas embolism with carbon dioxide and helium during pneumoperitoneum. Surg Endosc 2000;14: 1167–1170.
Purpose: To describe a case of intraoperative mortality because of air embolism during resection of a choroidal melanoma by pars plana vitrectomy. Methods: Retrospective interventional case report. Results: A 69-year-old man died unexpectedly at the time of pars plana vitrectomy. The operative technique involved the use of high-pressure air (60 mmHg) in the presence of traumatically exposed choroidal vasculature. Autopsy revealed a large air embolus in the right ventricle, which resulted in sudden cardiovascular collapse. Conclusion: Air embolism is a rare complication of ophthalmic surgery. Infusion of air in the presence of traumatically exposed choroidal vasculature exposes the patient to the risk of air embolism. Ophthalmic surgeons and anesthetists should be aware of the possibility of air embolism during certain ophthalmic procedures, and appropriate intraoperative monitoring should be considered. RETINAL CASES & BRIEF REPORTS 8:127–129, 2014
From the Departments of *Ophthalmology, and †Forensic Pathology, Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa.
nosis of peripheral vascular disease and a high body mass index of 39, he was considered to be in an optimized condition for surgery and had no electrocardiogram (ECG) or stress ECG features of myocardial ischemia. Anesthetic induction was uneventful, and maintenance was achieved with sevoflurane, nitrous oxide, and oxygen. One and a half hours into the procedure, the patient’s end-tidal carbon dioxide and oxygen saturation dropped precipitously (Figure 3). A slow ventricular rhythm turned into ventricular
Case Report A 69-year-old man with a choroidal melanoma of the right eye underwent elective general anesthesia for the purpose of transvitreal resection of the tumor and intended brachytherapy consolidation of the tumor bed. The tumor was 12.57 mm high with a base of 10.60 mm · 10.76 mm located inferonasal to the optic disk (Figure 1). It had a typical collar-stud configuration on ultrasound (Figure 2). Phacoemulsification and lens implantation was followed by 20 gauge, 3 port, pars plana vitrectomy. The tumor had invaded the overlying retina, and a localized retinectomy was therefore performed as part of the resection. Intraoperative hemorrhage made visualization difficult. To improve visualization, the resection was continued under an air infusion at pressures of up to 60 mmHg. This maintained the optics of the globe and helped tamponade the sites of hemorrhage. The patient was known to have controlled hypertension and noninsulin-dependent diabetes mellitus for 6 years. Despite a diagNone of the authors have any financial/conflicting interests to disclose. Reprint requests: James C. Rice, FCOphth (SA), Department of Ophthalmology, Groote Schuur Hospital, University of Cape Town, Observatory, Cape Town 7925, South Africa; e-mail: [email protected]
Fig. 1. Fundus photograph of the inferonasal tumor.
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Fig. 2. B-scan ultrasound demonstrating typical “collar-stud” appearance.
fibrillation, and resuscitation was unsuccessful. Pulmonary embolus or myocardial infarction was initially suspected. Lodox x-ray (Lodox Systems, Johannesburg, South Africa) before autopsy revealed the presence of air in the right ventricle of the heart (Figure 4). At autopsy, the heart was buoyant, and when opened under water, released a large number of air bubbles from the right ventricle. No air was found in the left ventricle. The fossa ovale was closed, and there was no ventricular septum defect. No pulmonary thromboembolism or features of myocardial infarction could be found. There were no air bubbles in the infusion line, and a diagnosis of air embolism from the ocular surgical site was made.
Discussion Vascular air embolism (VAE) may be defined as the entrainment of air or gas from the operative field into
Fig. 3. Intraoperative graphs demonstrating precipitous drop in end-tidal CO2 (Figure 3A) and oxygen saturation (Figure 3B).
the venous or arterial vasculature producing systemic effects.1 A review article on this topic was recently published by Gordy and Rowell.2 The condition is more commonly described in procedures, in which the surgical field is above the level of the heart, such as neurosurgical procedures performed in a sitting position. The resultant gravitational gradient facilitates entrainment of air into the vasculature. Modern operative procedures, in which gas is used under pressure such as laparoscopic surgery or gastrointestinal endoscopy, provide an alternative pathophysiology of entrainment. Air–fluid exchange, in which the vitreous compartment is filled with air under pressure, is a common technique in vitreoretinal surgery and under certain circumstances may increase the risk of VAE. Intraoperative VAE is rare during eye surgery but has been suspected as the possible cause of cardiovascular instability during the pars plana vitrectomy for retinal detachment in a 55-year-old man3 and during the removal of a posterior intraocular foreign body in a 17-month-old child.4 Both patients recovered uneventfully. An ultimately fatal case was reported by Dermigny et al5 after removal of an intraocular foreign body. In all cases, air was infused under pressure. In the retinal detachment case, the report of an “abnormally swollen” choroid suggests that the infusion line lay within the choroidal compartment, and infusion occurred into the choroidal circulation. In the other cases (and ours), the air was most likely entrained into the traumatically exposed vasculature. The surgical technique of endoresection involves removal of all choroidal tissue in the region of the tumor, ideally resecting down to bare sclera. Open choroidal and tumor vasculature are potentially exposed to infused air. Ampulliform dilatation of the vortex veins occurs just before the vessels enter the sclera and widens the vascular access. Attachment to
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Fig. 4. Preautopsy Lodox x-ray showing air within the heart shadow.
the scleral opening may also prevent collapse of these vessels. In addition, a reduction in vessel wall elasticity with age6 may contribute to maintaining vessel patency during surgery. This setting may therefore pose a particular risk for entrainment of air. The diameter of the choroidal veins varies from 300 mm to 2 mm at the ampulla. Ledowski et al3 have calculated that, according to the Hagen–Poisseuille law, potentially lethal air flow of 1,600 mL/minute into the choroidal circulation is theoretically possible with a 20-gauge infusion cannula and an air infusion pressure of 40 mmHg. Although the assumptions in this model are not all met, it is still likely that a significant volume of air may be entrained. The lethal volume of air for an adult has been estimated at 200 mL to 300 mL,7 but the rate of entrainment is also critical because larger volumes may be tolerated if entrained over long periods.1 We used infusion pressures of up to 60 mmHg. It is also likely that the use of nitrous oxide in our case exacerbated the hemodynamic effects of the embolus.8,9 The pathophysiological effect of the VAE largely depends on the volume of gas that accumulates in the right ventricle. A large embolus (as occurred in our patient) results in a complete outflow obstruction from the right ventricle, rapid right-sided heart failure, and immediate cardiovascular collapse,1 as evidenced by the precipitous decrease in end-tidal CO2 and arterial oxygen saturation (Figure 3). The main aim of this report is to raise awareness of the possibility of VAE during eye surgery, where the choroidal vascular is exposed, and air infusion is used either to improve visualization or as part of fluid removal before the insertion of silicone oil. Longer
exposure and high infusion pressures are likely to increase the risk of VAE. Endoresection of choroidal melanoma is a rare procedure, and the authors are not aware of other cases of VAE in this setting. As a preventative measure, we would suggest considering ligation of the vortex vein(s) draining the excision site. Although vortex vein ligation may precipitate an acute choroidal hemorrhage, we believe it may prove effective at preventing VAE without compromising the outcome of the procedure. Methods of intraoperative detection of VAE are discussed in detail by Mirski et al.1 High levels of vigilance and awareness are always required. Transoesophageal echocardiography is the most sensitive monitoring technique but is invasive and requires a high level of expertise. It can detect as little as 0.02 mL/kg of air. The most sensitive noninvasive monitor is precordial Doppler, which is able to detect as little as 0.25 mL (0.05 mL/kg) of air. This device produces a characteristic “mill-wheel” murmur indicating cardiovascular decompensation. Mirski et al suggest that precordial Doppler can be used in cases of open vasculature in the presence of air or gas infusion (e.g., laparoscopic procedures), and we suggest that these monitoring techniques also be considered in certain cases of ophthalmic surgery. Key words: air embolism, choroidal melanoma, endoresection. References 1. Mirski MA, Lele AV, Fitzsimmons L, Toung TJ. Diagnosis and treatment of vascular air embolism. Anesthesiology 2007;106: 164–177. 2. Gordy S, Rowell S. Vascular air embolism. Int J Crit Illn Inj Sci 2013;3:73–76. 3. Ledowski T, Kiese F, Jeglin S, Scholz J. Possible air embolism during eye surgery. Anesth Analg 2005;100:1651–1652. 4. Ruest P, Aroichane M, Cordahi G, Bureau N. Possible venous air embolism during open eye surgery in a child. Can J Anaesth 2007;54:840–844. 5. Dermigny F, Daelman F, Guinot P, et al. Fatal air embolism during open eye surgery [in French]. Ann Fr Anesth Reanim 2008;27:840–842. 6. Bron AJ, Wolff E, Tripathi RC, Tripathi BJ, eds. Wolff’s Anatomy of the Eye and Orbit. 8th ed. London, United Kingdom: Chapman & Hall; 1998:405–410. 7. Toung TJ, Rossberg MI, Hutchins GM. Volume of air in a lethal venous air embolism. Anesthesiology 2001;94:360–361. 8. Kyttä J, Tanskanen P, Randell T. Comparison of the effects of controlled ventilation with 100% oxygen, 50% oxygen in nitrogen, and 50% oxygen in nitrous oxide on responses to venous air embolism in pigs. Br J Anaesth 1996;77:658–661. 9. Junghans T, Böhm B, Meyer E. Influence of nitrous oxide anesthesia on venous gas embolism with carbon dioxide and helium during pneumoperitoneum. Surg Endosc 2000;14: 1167–1170.
