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Mercury embolization during arterial pressure monitoring
Mercury embolization during arterial pressure monitoring Robert L. Berger, M.D.,* Irving M. Madoff, M.D.,** and Thomas J. Ryan, M.D.,*** Boston, Mass.
J_-/irect recording of arterial pressure has become a routine feature of open-heart procedures and is gaining widespread use in the monitoring of other critically ill patients. The pressure in a cannulated artery can be recorded in several different ways. One widely employed method is the utilization of a strain-gauge transducer connected to a galvanometer or oscillographic recording system. In addition to being delicate and expensive, this equipment requires trained personnel and frequent flushing to avoid clotting and obstruction of the conduit. For these reasons the simpler mercury manometer has been selected for routine use in many centers. A recent publication in this JOURNAL described such a unit.1 The simplicity and apparent safety of the design led us to adopt it for routine use over the past 2 years. The present report deals with a serious complication arising from the use of such a mercury manometer which to our knowledge has not been previously reported. From the Departments of Surgery and Medicine, St. Elizabeth's Hospital, and Tufts University School of Medicine, Boston, Mass. Address: St. Elizabeth's Hospital, 736 Cambridge Street, Boston, Mass. Received for publication June 7, 1966. ♦Director of Cardiac Surgery and Surgical Research Laboratory, St. Elizabeth's Hospital; Assistant Professor of Surgery, Tufts University School of Medicine. ** Visiting Surgeon, St. Elizabeth's Hospital; Associate Clinical Professor of Surgery, Boston University School of Medicine. ***Director of Cardiopulmonary Laboratory, St. Elizabeth's Hospital; Assistant Professor of Medicine, Tufts University School of Medicine.
Case report A 54-year-old house painter entered St. Elizabeth's Hospital with incapacitating cardiac symptoms. Physical examination indicated the presence of mitral regurgitation and this was confirmed by cardiac catheterization. Prior to thoracotomy for open repair of the lesion, the left brachial artery was exposed and cannulated with an 18-gauge polyvinyl catheter. This was attached to a mercury manometer (Fig. 1). Total cardiopulmonary bypass was carried out from iliac artery to vein.2 An asymmetrical mitral valvuloplasty was performed. The postoperative course was uneventful until the second day when the patient suddenly experienced severe pain in the left hand. The palmar surface of the hand was blotchy purple and the distal phalanges of all digits were deeply cyanotic and cold. Both radial and ulnar pulses were palpable and of good quality. There had been no difficulties with the manometer and the catheter system was obviously patent. Notwithstanding, in the face of such ischemic changes the arterial cannula was immediately removed. During the next 12 hours the discoloration and temperature changes progressed and the viability of the medial four digits appeared threatened. A roentgenogram of the left forearm and hand was obtained. The distal digital vessels and the volar arch contained a radiopaque material (Fig. 2). Radiologic survey of the entire body revealed no additional deposits. It was assumed that the radiopacities repre285
2 86
Journal of
Berger et al.
Thoracic and Cardiovascular Surgery
Fig. 1. The mercury manometer described in a previous report and used in our patient. A saline manometer used for venous pressure measurements is to the right.
sented mercury spillover from the manometer. Repeated stellate blocks on the left were administered and a course of Cuprimine therapy was instituted in order to reduce absorption of the mercury by the tissues. Urinary excretion of the mercury is depicted in Table I. Four days after mercury embolization, the ischemic changes began to become demarcated. Two weeks later the dry gangrene was limited to the distal phalanges of the four medial fingers. At this time the Cuprimine therapy was discontinued. The patient was discharged during the third hospital week only to be readmitted 2 weeks later for amputation of the four distal phalanges. Discussion Embolization of mercury from a manometer into the arterial tree may take place in two ways. With the need to position the manometer tray sideways, the mercury can gravitate into a dependent position and slip
directly through the arterial line into the cannulated vessel. The second mechanism is aspiration of the metallic mercury into the central tubing through the three-way stopcocks during blood sampling. Since the rubber tubing is not transparent, the mercury may remain undetected and will migrate farther into the vascular tree uninfluenced by the force of the arterial pressure. The results, of course, are catastrophic. The type of mercury manometer described by Boyd and used in our unit has many attractive features. It is simple, inexpensive, pressures can be read instantaneously, and the need for frequent flushing is eliminated by to-and-fro motion of the mercury in the system. Arterial samples are easy to obtain. The risk of mercury embolization, however, outweighs all these advantages and we have abandoned the use of this monitoring method in favor of a more complex transducer system. The true incidence of embolization from
Volume 53
Mercury embolization
Number 2 February, 1967
Fig. 2. Roentgenogram of the left hand obtained 12 hours after the onset of pain.
T a b l e I. Urinary
excretion
of
mercury
Time after embolization (days)
Urinary Ilg (mgJL.)
1 3 4 5 7 12 21 50 88 109
0.32 0.46 0.50 0.68 1.13 0.33 0.21 0.14 0.34 0.26
a mercury manometer is not known, mainly because the source of the embolus is frequently not recognized. Following our experience, we became aware of a similar event in another institution. Furthermore, we have learned of several instances in which ischemia of an extremity developed while an indwelling arterial cannula attached to a mercury manometer was employed. In these cases the possibility of mercury embolization
28 7
was not entertained, roentgenograms were not obtained and no definitive diagnoses were possible. In the absence of any report on embolization from a mercury manometer, it is easy to understand why the cause of this complication may remain undetected. There are, however, several papers on embolization from the use of mercurysealed syringes for blood sampling. 3 ' 4 The site of final migration was variable and included almost every organ of the body. Ionization of intravascular metallic mercury is slow and systemic toxicity is, therefore, uncommon. The major problem is interruption of blood flow to the target organs. On the basis of the measured urinary excretion of mercury, the use of chelating agents may not be necessary. It is possible to reduce the dangers of embolization by insertion of a trap bottle into the circuit but this is difficult to do without sacrificing the accuracy of the pressure measurement. It would seem far safer to abandon the use of mercury manometers in patients and substitute less dangerous devices. Summary
A case of mercury embolization from a pressure manometer is reported in a patient being monitored after successful open-heart repair of mitral valve disease. The complication resulted in surgical amputation of four distal phalanges. We extend our appreciation to Dr. Harriet L. Hardy for her advice in the management of this patient and to W. Boylan of Massachusetts Institute of Technology for the urinary mercury determination. REFERENCES 1 Boyd, T . F . : Direct Measurement of Arterial Blood Pressure, J. THORACIC & CARDIOVAS. SURG.
45: 240, 1963. 2 Berger, R. L., and Barsamian, E. M.: Iliac or Femoral Vein-to-Artery Total Cardiopulmonary Bypass. An Experimental and Clinical Study, Ann. Thor. Surg. 2: 281, 1966. 3 Buxton, J. T., Jr., Hewitt, J. C , Gadsden, R. H., and Bradham, G. B.: Metallic Mercury Embolism, J. A. M. A. 193: 573, 1965. 4 Schultz, E., and Beskind, H.: Systemic Deposition of Metallic Mercury, J. Pediat. 5 7 : 733, 1960.
J_-/irect recording of arterial pressure has become a routine feature of open-heart procedures and is gaining widespread use in the monitoring of other critically ill patients. The pressure in a cannulated artery can be recorded in several different ways. One widely employed method is the utilization of a strain-gauge transducer connected to a galvanometer or oscillographic recording system. In addition to being delicate and expensive, this equipment requires trained personnel and frequent flushing to avoid clotting and obstruction of the conduit. For these reasons the simpler mercury manometer has been selected for routine use in many centers. A recent publication in this JOURNAL described such a unit.1 The simplicity and apparent safety of the design led us to adopt it for routine use over the past 2 years. The present report deals with a serious complication arising from the use of such a mercury manometer which to our knowledge has not been previously reported. From the Departments of Surgery and Medicine, St. Elizabeth's Hospital, and Tufts University School of Medicine, Boston, Mass. Address: St. Elizabeth's Hospital, 736 Cambridge Street, Boston, Mass. Received for publication June 7, 1966. ♦Director of Cardiac Surgery and Surgical Research Laboratory, St. Elizabeth's Hospital; Assistant Professor of Surgery, Tufts University School of Medicine. ** Visiting Surgeon, St. Elizabeth's Hospital; Associate Clinical Professor of Surgery, Boston University School of Medicine. ***Director of Cardiopulmonary Laboratory, St. Elizabeth's Hospital; Assistant Professor of Medicine, Tufts University School of Medicine.
Case report A 54-year-old house painter entered St. Elizabeth's Hospital with incapacitating cardiac symptoms. Physical examination indicated the presence of mitral regurgitation and this was confirmed by cardiac catheterization. Prior to thoracotomy for open repair of the lesion, the left brachial artery was exposed and cannulated with an 18-gauge polyvinyl catheter. This was attached to a mercury manometer (Fig. 1). Total cardiopulmonary bypass was carried out from iliac artery to vein.2 An asymmetrical mitral valvuloplasty was performed. The postoperative course was uneventful until the second day when the patient suddenly experienced severe pain in the left hand. The palmar surface of the hand was blotchy purple and the distal phalanges of all digits were deeply cyanotic and cold. Both radial and ulnar pulses were palpable and of good quality. There had been no difficulties with the manometer and the catheter system was obviously patent. Notwithstanding, in the face of such ischemic changes the arterial cannula was immediately removed. During the next 12 hours the discoloration and temperature changes progressed and the viability of the medial four digits appeared threatened. A roentgenogram of the left forearm and hand was obtained. The distal digital vessels and the volar arch contained a radiopaque material (Fig. 2). Radiologic survey of the entire body revealed no additional deposits. It was assumed that the radiopacities repre285
2 86
Journal of
Berger et al.
Thoracic and Cardiovascular Surgery
Fig. 1. The mercury manometer described in a previous report and used in our patient. A saline manometer used for venous pressure measurements is to the right.
sented mercury spillover from the manometer. Repeated stellate blocks on the left were administered and a course of Cuprimine therapy was instituted in order to reduce absorption of the mercury by the tissues. Urinary excretion of the mercury is depicted in Table I. Four days after mercury embolization, the ischemic changes began to become demarcated. Two weeks later the dry gangrene was limited to the distal phalanges of the four medial fingers. At this time the Cuprimine therapy was discontinued. The patient was discharged during the third hospital week only to be readmitted 2 weeks later for amputation of the four distal phalanges. Discussion Embolization of mercury from a manometer into the arterial tree may take place in two ways. With the need to position the manometer tray sideways, the mercury can gravitate into a dependent position and slip
directly through the arterial line into the cannulated vessel. The second mechanism is aspiration of the metallic mercury into the central tubing through the three-way stopcocks during blood sampling. Since the rubber tubing is not transparent, the mercury may remain undetected and will migrate farther into the vascular tree uninfluenced by the force of the arterial pressure. The results, of course, are catastrophic. The type of mercury manometer described by Boyd and used in our unit has many attractive features. It is simple, inexpensive, pressures can be read instantaneously, and the need for frequent flushing is eliminated by to-and-fro motion of the mercury in the system. Arterial samples are easy to obtain. The risk of mercury embolization, however, outweighs all these advantages and we have abandoned the use of this monitoring method in favor of a more complex transducer system. The true incidence of embolization from
Volume 53
Mercury embolization
Number 2 February, 1967
Fig. 2. Roentgenogram of the left hand obtained 12 hours after the onset of pain.
T a b l e I. Urinary
excretion
of
mercury
Time after embolization (days)
Urinary Ilg (mgJL.)
1 3 4 5 7 12 21 50 88 109
0.32 0.46 0.50 0.68 1.13 0.33 0.21 0.14 0.34 0.26
a mercury manometer is not known, mainly because the source of the embolus is frequently not recognized. Following our experience, we became aware of a similar event in another institution. Furthermore, we have learned of several instances in which ischemia of an extremity developed while an indwelling arterial cannula attached to a mercury manometer was employed. In these cases the possibility of mercury embolization
28 7
was not entertained, roentgenograms were not obtained and no definitive diagnoses were possible. In the absence of any report on embolization from a mercury manometer, it is easy to understand why the cause of this complication may remain undetected. There are, however, several papers on embolization from the use of mercurysealed syringes for blood sampling. 3 ' 4 The site of final migration was variable and included almost every organ of the body. Ionization of intravascular metallic mercury is slow and systemic toxicity is, therefore, uncommon. The major problem is interruption of blood flow to the target organs. On the basis of the measured urinary excretion of mercury, the use of chelating agents may not be necessary. It is possible to reduce the dangers of embolization by insertion of a trap bottle into the circuit but this is difficult to do without sacrificing the accuracy of the pressure measurement. It would seem far safer to abandon the use of mercury manometers in patients and substitute less dangerous devices. Summary
A case of mercury embolization from a pressure manometer is reported in a patient being monitored after successful open-heart repair of mitral valve disease. The complication resulted in surgical amputation of four distal phalanges. We extend our appreciation to Dr. Harriet L. Hardy for her advice in the management of this patient and to W. Boylan of Massachusetts Institute of Technology for the urinary mercury determination. REFERENCES 1 Boyd, T . F . : Direct Measurement of Arterial Blood Pressure, J. THORACIC & CARDIOVAS. SURG.
45: 240, 1963. 2 Berger, R. L., and Barsamian, E. M.: Iliac or Femoral Vein-to-Artery Total Cardiopulmonary Bypass. An Experimental and Clinical Study, Ann. Thor. Surg. 2: 281, 1966. 3 Buxton, J. T., Jr., Hewitt, J. C , Gadsden, R. H., and Bradham, G. B.: Metallic Mercury Embolism, J. A. M. A. 193: 573, 1965. 4 Schultz, E., and Beskind, H.: Systemic Deposition of Metallic Mercury, J. Pediat. 5 7 : 733, 1960.