Shivering can cause a significant disruption of therapeutic hypothermia by generation of heat, leading to increased core body temperature and oxygen consumption (10,55). The European and Australian studies used vecuronium infusion as a paralytic, with IV midazolam as an accompanying sedative (8,9) . The initiation of pharmacologic paralysis with sedation will require full mechanical respiratory support. Total paralysis will also make clinical neurologic assessment very limited. Therefore, a detailed neurologic assessment is essential prior to the start and at the completion of pharmacologic paralysis and sedation. The neurologic evaluation must consist of not only the GCS, but also a careful evaluation of cranial nerve function, and sensory motor responses. A decline in neurologic function merits emergent diagnostic evaluation (such as brain imaging) and neurophysiologic assessment (such as an electroencephalography or somatosensory-evoked potential testing).
Another concern related to shivering is that the discomfort associated with shivering might also be a problem for those patients who are emerging from coma. Although no comparison studies exist that address the degree of shivering in the different methods of hypothermia, more patients have been noted to shiver with rapid surface-cooling systems (60). In studies of cases of hypothermia in other conditions, such as stroke and postoperative states without total pharmacologic paralysis and sedation, the shivering threshold was lowered by the use of meperidine (64-67). The synergistic effect of buspirone with meperidine in controlling shivering has also been reported (64). Other agents that might be helpful in controlling shivering are clonidine, ketanserin, and doxapram (67).
The induction of hypothermia in post CA patients by means of an endovascular catheter has also been reported to be safe (68,69). The endovascular catheters are inserted percutane-ously into large veins, such as the femoral and subclavian, to induce hypothermia. As this is an invasive procedure, technical expertise is warranted to attenuate complications. Other concerns include venous thrombosis, infection, and bleeding.
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