Effects of Halothane, Enflurane, and Isoflurane in Nitrous Oxide on Multilevel Somatosensory Evoked Potentials

Intraoperative control by somatosensory evoked potentials in the treatment of cervical myeloradiculopathy. Results in 210 cases

“…For example, as little as 0.8°C of hypothermia increases latency [28]. This can be caused by a deeper level of anaesthesia [4, 10,32,33,44] or by haemodynamic disturbances such as hypotension, tachycardia or bradycardia, and also by local vascular abnormalities such as arterial occlusions or spasms, or external compression of vessels by a haematoma, bone graft, screw or bone or disk fragment [15,19,30]. It could be argued that we are testing the function of the posterior cord (sensory pathway) and not the more important and interesting anterior motor pathway.…”

“…In bilateral conditions, the traces show the different functional deterioration of each lateral nerve. We generally used subcortical SEPs, which for the upper extremities produce a response within the first 20 ms of the stimulation and provide very stable information from their anatomic generators in the presence of anaesthetic drugs and gases (halotane, isofluorane and N20 ) [7,32,33,35,44]. The subcortical SEP response consists of a se- quence of waves termed N-9, N-11, N-13/14 complex and N-20.…”

Evoked potential monitoring in anaesthesia and analgesia

“…In addition, early waves (brainstem) are affected less by drugs than are late potentials (cortical). With inhalational agents, the spinal and subcortical waves are affected less than the cortical potentials [78,79].…”

“…The effects of currently used volatile agents on SSEPs are dose-dependent increases in latency and conduction times and decreases in amplitude [78,79,110,111]. The relative effects are somewhat controversial: some evidence suggests that halothane has a greater impact on SSEPs than either isoflurane or enflurane [79], other evidence supports a greater effect by enflurane and isoflurane than halothane [78].…”

“…The relative effects are somewhat controversial: some evidence suggests that halothane has a greater impact on SSEPs than either isoflurane or enflurane [79], other evidence supports a greater effect by enflurane and isoflurane than halothane [78]. Up to 0.5-1 MAC isoflurane in the presence of nitrous oxide is compatible with adequate monitoring of cortical SSEPs [78,79,[110][111][112].…”