Near-fatal air embolism: fibrin sheath as the portal of air entry.

Abstract: Complications of central venous catheters occur in less than 1% of all insertions. Of these, pulmonary air embolism is a rare though often fatal complication. Possible mechanisms include opening of the line to the atmosphere during use and poor technique during insertion or removal. There has also been speculation that the presence of a fibrin sheath after removal might be a mechanism for air entry. We present a case of a near-fatal pulmonary air embolus with documentation of air in the pulmonary outflow trunk and a residual air-filled fibrin tract seen on computed tomography.

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Venous air embolism from central venous catheters has been described. The most common mechanism is inadvertent opening of the line to the atmosphere. Less commonly, air embolism can occur with insertion or after the catheter has been removed. The syndrome ranges in severity from mild respiratory distress to cardiopulmonary collapse. Mortality may reach 50%. (1) The development of fibrin sheaths around indwelling central catheters has been previously described. There has been speculation that fibrin sheaths might provide a channel for air embolism after removal of a catheter, though proof has been inadequate. (2) We report a case of near-fatal pulmonary air embolism after removal of a central venous catheter, with radiologic documentation of a fibrin sheath as the portal for air entry.

Discussion

Serious complications of central lines occur in less than 1% of all catheter insertions. Venous air embolism is a rare complication that may occur during insertion, during use if the infusion tubing is disconnected and opened to the air, or after removal if there is air entry through a formed catheter tract. (1) After a catheter is removed, normal hemostatic processes usually close the SC tract. It is possible that inadequate hemostasis of the catheter tract (3) or dislodgment of a thrombus plug by high positive pressure from straining or coughing might delay closure of the SC tract or actually reopen it and thus predispose to air embolus. (4,5) In fact, most authors believe that a residual SC catheter tract is responsible for the rare cases of air embolism that occur after removal of a central venous catheter. (5-9) Another complication of central venous catheters is a fibrin sheath or sleeve that commonly forms on indwelling catheters, often within 24 hours of insertion. (8) These fibrin sheaths are usually benign and lyse spontaneously, but they may be a nidus for thrombus formation. There has been speculation that a fibrin sheath might provide a portal for air entry into the circulation, but that has not been previously well documented. Chest CT scanning in our case was performed shortly after the episode of air embolism and showed a tubular air-filled structure (fibrin sheath) leading through the SC tissue into the central veins.

[FIGURE 1 OMITTED]

Some authors hold that the SC tract from a central venous catheter always collapses immediately after it is removed, negating any need for special positioning or occlusive dressings. (10) The experience of our patient argues for a more careful approach. No specific data support various techniques used to prevent air embolism, but we believe that Trendelenburg positioning for catheter removal and occlusive dressings after removal are common-sense items that might prevent this potentially fatal complication. Our surgical/trauma/neuroscience unit has a procedure guideline for nurses removing central venous catheters. It includes Trendelenburg positioning, catheter removal at end-inspiration while holding pressure over the SC tunnel, and application of an occlusive dressing that remains in place for 24 hours. Ely et al (11) documented low physician awareness of the risks of venous air embolism during catheter removal but found that through education they could increase appropriate positioning. In a nursing survey, Dumont (12) found that Trendelenburg position was used all or most of the time in only 17.2% of all central venous catheter removals, and an occlusive dressing was used 82% of the time. Rarely was there any attempt to time the catheter removal with patient respiration.

[FIGURE 2 OMITTED]

Conclusions

Complications of central venous access include pulmonary air embolism, which is rare, but may be serious. In our patient, positioning and timing of catheter removal were appropriate, but the dressing was not air occlusive. Ultimately, an inappropriate dressing when combined with deep inhalation through pursed lips led to an almost fatal complication. We believe that diligence in all steps of catheter removal is important to prevent this potentially fatal complication. Education of persons responsible for removal of central venous catheters may help to decrease the incidence of this totally avoidable complication.

Measure wealth not by the things you have, But by the things you have for which you would not take money

-Author unknown

From the Department of Surgery, Hennepin County Medical Center, Minneapolis, MN.

Reprint requests to Shawn Roberts, MD, Department of Surgery, Hennepin County Medical Center, 701 Park Avenue, Minneapolis, MN 55415. Email: [e-mail]

Accepted April 24, 2002.

Copyright [c] 2003 by The Southern Medical Association 0038-4348/03/9610-1036

References

1. Kashuk J, Penn I. Air embolism after central venous catheterization. Surg Gynecol Obstet 1984;159:249-252.

2. Hoshal V. Ause R, Hoskins P. Fibrin sleeve formation on indwelling subclavian central venous catheters. Arch Surg 1971;102:353-358.

3. Boer W, Hene R. Lethal air embolism following removal of a double lumen jugular vein catheter. Nephrol Dial Transplant 1999;14:1850-1852.

4. Hanley P, Click R, Tancredi R. Delayed air embolism after removal of venous catheters. Ann Intern Med 1984;101:401-402.

5. Turnage S, Harper J. Venous air embolism occurring after removal of a central venous catheter. Anesth Analg 1991;72:559-560.

6. Madden B, Paruchuru P. Kunst H. Sucking noise and collapse after central venous catheter removal. J R Soc Med 2000;93:592-593.

7. Phifer T, Bridges M, Conrad S. The residual central venous catheter track: An occult source of lethal air embolism-Case report. J Trauma 1991;31:1558-1560.

8. McCarthy PM, Wang N, Birchfield F, Mehta AC. Air embolism in single-lung transplant patients after central venous catheter removal. Chest 1995;107:1178-1179.

9. Mennim P, Coyle C, Taylor J. Venous air embolism associated with removal of central venous catheter. BMJ 1992;305:171-172.

10. Sing RF, Thomason MH, Heniford BT, Miles WS, Huynh TT, Jacobs DG, et al. Venous air embolism from central venous catheterization: Under-recognized or over-diagnosed? Crit Care Med 2000;28:3377-3378 (letter).

11. Ely EW, Hite RD, Baker AM, Johnson MM, Bowton DL, Haponik EF. Venous air embolism from central venous catheterization: A need for increased physician awareness. Crit Care Med 1999;27:2113-2117.

12. Dumont C. Procedures nurses use to remove central venous catheters and complications they observe: A pilot study. Am J Crit Care 2001;10:151-155.

RELATED ARTICLE: Case Report

A 20-year-old man was admitted to the hospital after an altercation because of headache and decreased level of consciousness. A computed tomographic (CT) scan of the head showed an epidural hematoma, and he was taken to the operating room for neurosurgical evacuation of the blood. Postoperatively, a 7-Fr triple-lumen central venous catheter was placed in the left subclavian vein for IV access and hemodynamic monitoring. The patient had an excellent neurologic recovery, and by hospital Day 6 he was transferred to the ward. On Day 7, anticipating discharge, the nursing staff removed the central catheter and applied a gauze dressing secured with paper tape. Within 30 minutes, the patient left his room, accompanied by family members, for a smoke outside the building. As related by his mother, he took one long, deep inhalation of a cigarette and immediately had severe substernal chest pain and extreme shortness of breath. He was brought back to his hospital room and the surgical house staff were called for urgent evaluation. On initial examination, he was tachypneic and diaphoretic. Initial vital signs were blood pressure 105/45 mm Hg, pulse rate 125 beats/min, respiratory rate 36 breaths/min, and oxygen saturation 92% on 100% oxygen by face mask. The patient was taken immediately to the surgical intensive care unit, where resuscitation was begun and he was intubated. Arterial blood gas values on high-flow oxygen during preparation for intubation were P[O.sub.2] 80 mm Hg, PC[O.sub.2] 101 mm Hg, and pH 7.06. Because air embolus was suspected, the patient was placed in the Trendelenburg position and an occlusive dressing was placed over the left subclavian puncture site. New central access was obtained via the right subclavian vein, and aspiration of air was attempted, without success. Electrocardiographic findings were consistent with right atrial enlargement and right axis deviation but showed no signs of ischemia. Chest radiograph showed a lucency in the pulmonary artery outflow trunk (Fig. 1). Echocardiogram showed the right side of the heart to be dilated with poor right ventricular function but no evidence of intracardiac air. A spiral CT angiogram obtained within an hour of the chest radiograph showed no pulmonary embolus and resolution of the air that had been seen on the plain film in the central pulmonary artery. The CT angiogram did reveal a fibrin sheath filled with a column of air extending from the subclavian vein into the superior vena cava (Fig. 2). The patient's shock improved quickly with ventilatory support and IV fluids. Subsequent chest radiographs showed diffuse pulmonary edema consistent with acute lung injury, but the acidosis totally resolved over 10 hours and the patient was extubated within 3 days.

RELATED ARTICLE: Key Points

* Portal air embolism is a rare though often fatal complication of central lines.

* Pulmonary air embolism is an underrecognized complication of central line placement or removal.

* Fibrin sheaths play a role in the pathophysiology of air embolism after central line removal.

* All steps in catheter removal are important in preventing pulmonary air embolism.

Shawn Roberts, MD, Michelle Johnson, MD, and Scott Davies, MD