1. Detection of stroke during cardiac operations with somatosensory evoked responses 
Mark M. Stecker, MD, PhDa, Albert T. Cheung, MDb, Terry Patterson, PhDa, Joseph S. Savino, MDb, Stuart J. Weiss, MD, PhDb, Rafael M. Richards, MSb, Joseph E. Bavaria, MDc, Timothy J. Gardner, MDc 
The Journal of Thoracic and Cardiovascular Surgery 
Volume 112, Issue 4, Pages (October 1996)
DOI: /S (96)70096-X
Copyright © 1996 Mosby, Inc. Terms and Conditions

2. Fig. 1
A, SEP recording obtained at baseline from patient 20. This tracing demonstrates the "normal" morphology of the SEP during cardiac surgery. B, SEP recorded after the initiation of cardiopulmonary bypass and active cooling. In comparison with A, the N20-P22 complex arising from stimulation of the left arm and representing activity in the left thalamus and cortex has disappeared whereas that arising from stimulation of the right arm remains intact. There is a prolongation in the latency of the responses owing to cooling. Note that the spinal (N13) and brain stem (N18) potentials remain present bilaterally. With continued cooling (C), the latency of all waves increases but the N20-P22 complex from stimulation of the left arm remained absent. By the end of the operation (D), the amplitude of the N20-P22 complex from stimulation of the left arm has recovered somewhat, but continues to be of much lower amplitude than at the beginning of the case. In this figure, left and right refer to the ulnar nerve that was stimulated. T, Temperature; Rerb, right Erb point; Lerb, left Erb point.
The Journal of Thoracic and Cardiovascular Surgery  , DOI: ( /S (96)70096-X)
Copyright © 1996 Mosby, Inc. Terms and Conditions

3. Fig. 2
A, Changes in amplitude asymmetry during the operation in patient 6, who did not have an intraoperative stroke. The largest values of the amplitude asymmetry occurred during rapid temperature changes and were of short duration. B, The time course of the amplitude asymmetry in patient 20, who did have an intraoperative stroke. The acute increase in amplitude asymmetry during the initiation of cardiopulmonary bypass indicates the onset of cerebral ischemia. The labels A-D on this figure refer to the corresponding evoked potential tracings shown in Fig. 1. COOL, Time of active cooling; CPB, time of cardiopulmonary bypass; STERN, time of sternotomy from opening to closure; A o Can, time of aortic cannulation.
The Journal of Thoracic and Cardiovascular Surgery  , DOI: ( /S (96)70096-X)
Copyright © 1996 Mosby, Inc. Terms and Conditions

4. Fig. 2
A, Changes in amplitude asymmetry during the operation in patient 6, who did not have an intraoperative stroke. The largest values of the amplitude asymmetry occurred during rapid temperature changes and were of short duration. B, The time course of the amplitude asymmetry in patient 20, who did have an intraoperative stroke. The acute increase in amplitude asymmetry during the initiation of cardiopulmonary bypass indicates the onset of cerebral ischemia. The labels A-D on this figure refer to the corresponding evoked potential tracings shown in Fig. 1. COOL, Time of active cooling; CPB, time of cardiopulmonary bypass; STERN, time of sternotomy from opening to closure; A o Can, time of aortic cannulation.
The Journal of Thoracic and Cardiovascular Surgery  , DOI: ( /S (96)70096-X)
Copyright © 1996 Mosby, Inc. Terms and Conditions

5. Fig. 3
Summary of SEP measurements in the group of patients with normal results of preoperative and postoperative examinations and those with intraoperative strokes. From each of the 1768 SEP recordings made, all available measurements for each variable are plotted using a separate column for each patient. Data for each variable are shown on separate plots: A, Amplitude asymmetry; B, amplitude variability; C, P22 latency asymmetry; D, N20 latency asymmetry; E, N13 latency asymmetry; F, Erb point latency asymmetry.
The Journal of Thoracic and Cardiovascular Surgery  , DOI: ( /S (96)70096-X)
Copyright © 1996 Mosby, Inc. Terms and Conditions

6. Fig. 3
Summary of SEP measurements in the group of patients with normal results of preoperative and postoperative examinations and those with intraoperative strokes. From each of the 1768 SEP recordings made, all available measurements for each variable are plotted using a separate column for each patient. Data for each variable are shown on separate plots: A, Amplitude asymmetry; B, amplitude variability; C, P22 latency asymmetry; D, N20 latency asymmetry; E, N13 latency asymmetry; F, Erb point latency asymmetry.
The Journal of Thoracic and Cardiovascular Surgery  , DOI: ( /S (96)70096-X)
Copyright © 1996 Mosby, Inc. Terms and Conditions

7. Fig. 3
Summary of SEP measurements in the group of patients with normal results of preoperative and postoperative examinations and those with intraoperative strokes. From each of the 1768 SEP recordings made, all available measurements for each variable are plotted using a separate column for each patient. Data for each variable are shown on separate plots: A, Amplitude asymmetry; B, amplitude variability; C, P22 latency asymmetry; D, N20 latency asymmetry; E, N13 latency asymmetry; F, Erb point latency asymmetry.
The Journal of Thoracic and Cardiovascular Surgery  , DOI: ( /S (96)70096-X)
Copyright © 1996 Mosby, Inc. Terms and Conditions

8. Fig. 3
Summary of SEP measurements in the group of patients with normal results of preoperative and postoperative examinations and those with intraoperative strokes. From each of the 1768 SEP recordings made, all available measurements for each variable are plotted using a separate column for each patient. Data for each variable are shown on separate plots: A, Amplitude asymmetry; B, amplitude variability; C, P22 latency asymmetry; D, N20 latency asymmetry; E, N13 latency asymmetry; F, Erb point latency asymmetry.
The Journal of Thoracic and Cardiovascular Surgery  , DOI: ( /S (96)70096-X)
Copyright © 1996 Mosby, Inc. Terms and Conditions

9. Fig. 3
Summary of SEP measurements in the group of patients with normal results of preoperative and postoperative examinations and those with intraoperative strokes. From each of the 1768 SEP recordings made, all available measurements for each variable are plotted using a separate column for each patient. Data for each variable are shown on separate plots: A, Amplitude asymmetry; B, amplitude variability; C, P22 latency asymmetry; D, N20 latency asymmetry; E, N13 latency asymmetry; F, Erb point latency asymmetry.
The Journal of Thoracic and Cardiovascular Surgery  , DOI: ( /S (96)70096-X)
Copyright © 1996 Mosby, Inc. Terms and Conditions

10. Fig. 3
Summary of SEP measurements in the group of patients with normal results of preoperative and postoperative examinations and those with intraoperative strokes. From each of the 1768 SEP recordings made, all available measurements for each variable are plotted using a separate column for each patient. Data for each variable are shown on separate plots: A, Amplitude asymmetry; B, amplitude variability; C, P22 latency asymmetry; D, N20 latency asymmetry; E, N13 latency asymmetry; F, Erb point latency asymmetry.
The Journal of Thoracic and Cardiovascular Surgery  , DOI: ( /S (96)70096-X)
Copyright © 1996 Mosby, Inc. Terms and Conditions

11. Fig. 4
The effects of the stimulation current on the amplitude asymmetry for the 21 patients with normal results of preoperative and postoperative neurologic examinations. The amplitude asymmetry is smaller at 25 mA stimulus currents than with 8, 12, or 16 mA stimulus currents. The small amplitude asymmetry values at stimulation currents less than 8 mA is the result of the fact that, for such low-amplitude stimuli, the amplitude of the evoked response has fallen below the level of background noise.
The Journal of Thoracic and Cardiovascular Surgery  , DOI: ( /S (96)70096-X)
Copyright © 1996 Mosby, Inc. Terms and Conditions