Kd. Stuhmeier et al., USE OF THE ELECTROSPINOGRAM FOR PREDICTING HARMFUL SPINAL-CORD ISCHEMIA DURING REPAIR OF THORACIC OR THORACOABDOMINAL AORTIC-ANEURYSMS, Anesthesiology, 79(6), 1993, pp. 1170-1176
Background. To reduce the incidence of misleading assessments, and to
derive criteria for critical spinal cord ischemia during thoracic or t
horacoabdominal aortic aneurysm repair, the authors epidurally stimula
ted and recorded somatosensory evoked potentials (ESEP) below and abov
e, respectively, the spinal segment at risk (electrospinogram). Method
s. Epidural somatosensory evoked potentials were analyzed in 100 conse
cutive patients undergoing resection of aortic aneurysms using two bip
olar catheters (stimulation at the L2 level and recording at the T3 le
vel) for the following criteria: 1) the time until ESEP disappeared co
mpletely after cross clamping, 2) the duration of complete ESEP loss d
uring and after cross clamping, and 3) the time until ESEP recovered a
fter declamping. Postoperatively, neurologic deficits were evaluated b
y a neurologist who was unaware of the ESEP recordings. Results: Three
types of patients could be identified. First, thirty-one patients nei
ther showed ESEP loss nor neurologic deficits. Second, ESEP loss occur
ring later than 15 min after cross clamping was associated with a neur
ologic deficit in 2 of 29 patients (6.9%). And, third, 12 of 40 patien
ts (30%) presented a neurologic deficit when ESEP loss occurred within
15 min after cross clamping. Further indicators of an impending risk
were a total ESEP loss greater than 40 min (sensitivity 100%, specific
ity 68%, positive predictive value [PPV] 35%, and negative predictive
value [NPV] 100%), and a recovery of ESEP later than 20 min after decl
amping (sensitivity 93%, specificity 86%, PPV 52%, and NPV 99%). Concl
usions. Epidural somatosensory evoked potentials appeared to be a reas
onable intraoperative predictor of postoperative neurologic outcome, a
nd informs surgeons and anesthesiologists about the impending danger a
t an early state of the operation.