Diffusive pulmonary embolism with bone fragments during spinal surgery
Editor—We would like to report a case of diffusive pulmonary embolism (PE) with bone fragments during spinal surgery. The patient was a 69-yr-old man (height, 174 cm; weight, 75 kg), with ossification of the posterior longitudinal ligament (OPLL) of the thoracic area and he has a history of essential hypertension. Extensive surgery involving resection of the OPLL from T3–T9 was planned. During general anaesthesia his arterial pressure was maintained at 130–140/60–70 mm Hg. In addition to standard monitors, a radial artery catheter was placed percutaneously but a central venous catheter was not inserted. The patient was placed in the prone position onto a Hall's frame and surgery was performed. After laminectomy, the resection of OPLL was initiated by posterior approach using surgical drill. Controlled hypotension by continuous injection of nitroglycerine at 0.5 µg kg–1 min–1 was performed at a range of 80–90/40–45 mm Hg. The blood gas analysis during the operation revealed progressive oxygen desaturation and carbon dioxide retention (Table 1). Five hours after the start of resection of OPLL, the patient's arterial pressure suddenly decreased from 88/45 to 55/30 mm Hg and the ECG showed sinus rhythm at a rate of 70 beats min–1. Severe hypotension (systolic arterial pressure <35 mm Hg) and bradycadia (30–40 beats min–1) was observed despite the administration of epinephrine and the end-tidal carbon dioxide partial pressure was noted to decrease to 14 mm Hg. The surgical procedure was discontinued and the patient was turned to supine position to carry out a cardiac massage. Despite a cardiac massage the ECG revealed a standstill in electrical activity. Two hours and forty minutes later, resuscitation was discontinued.
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An autopsy revealed microscopic diffusive PEs of bone fragments, which were confirmed by calcium stain, in the pulmonary capillary vasculature of all lobe segments in the lungs. However, neither thrombosis nor any air embolism was detected. The pathologist diagnosed the cause of death as microscopic diffusive PE of bone fragments. Vessel occlusion by bone fragments was detected in every section of lung and were more extensive than is found following cardiac resuscitation.
An animal model of experimental PE shows that impairment of oxygenation was less significant after divided bolus of microemboli than single bolus of equal quantity.1 It is likely in this case that the redistributed pulmonary blood flow might prevent gas change abnormality against the pulmonary vessel occlusion by bone fragments.
The use of a Hasting's frame, or other devices, increases a gravitational gradient between the right atrium and the vertebrae in spinal surgery.2 These devices decrease both caval pressure and perivertebral venous pressure, and consequently the patients are placed at risk of venous embolism. In cases of extensive spinal surgery, a central venous catheter should be placed to assist in fluid therapy to maintain central venous pressure beyond the gravitational gradient during operation.
Transoesophageal echocardiography (TEE) is a useful device for evaluating cardiac function and effective to diagnose PE showing typically the enlarged RV and left-sided septal shift.3 4 TEE could reflect ventricular diastolic volume for fluid therapy and qualitative assessment of ventricular function when severe haemodynamic change occurs. Cardiac monitoring with TEE should be considered for extensive spinal surgery.
Takatsuki, Japan
*E-mail: ane024{at}poh.osaka-med.ac.jp
References
1 Kay JC, Noble WH, Kadiri YZ. Single versus multiple pulmonary emboli: different haemodynamic and blood gas results. Can Anaesth Soc J 1981; 28:550–5[Web of Science][Medline]
2 Albin MS, Ritter RR, Pruett CE, Kalff K. Venous air embolism during lumbar laminectomy in the prone position: report of three cases. Anesth Analg 1991; 73:346–9
3 Chen HL, Wong CS, Ho ST, et al. A lethal pulmonary embolism during percutaneous vertebroplasty. Anesth Analg 2002; 95:1060–2
4 Gouldhaber S. Echocardiography in the management of pulmonary embolism. Ann Intern Med 2002; 136:691–700
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