[Analgesia and sedation in patients with head-brain trauma]

The goal of therapy in patients with severe head injury is to avoid secondary brain damage. Analgesia and sedation are an essential part of the therapy, and several drugs are in current use. However, few controlled clinical trials have been performed so far, and none of these drugs has proved to be superior. Although in the past the therapy has been focused on controlling elevated intracranial pressure (ICP), many authors emphasize the role of cerebral ischaemia in the prognosis of patients. Therefore, cerebral perfusion pressure (CPP) i.e. the difference between ICP and mean arterial pressure (CPP = MAP-ICP), seems to be more important than ICP alone. Analgesics and sedatives reduce the cerebral metabolic rate (CMR), and the consequent decrease in cerebral oxygen uptake might prevent ischaemic damage in regions with low perfusion. Moreover, a decrease in CMR is often associated with a decrease of cerebral blood flow (CBF) in regions with normal perfusion and, as a result, ICP is also reduced. Basically, the cerebral effects (on ICP, CMR, and CBF) and the haemodynamic effects with respect to maintenance of a sufficient CPP are most important in the selection of drugs for analgosedation. In addition, the effects on general intensive care management must be considered (pulmonary function, immunreactivity bowel motility). The purpose of this paper is to describe drugs commonly used for analgosedation in severe head injury. Barbiturates bring about the most pronounced decrease of CMR and ICP. In the past these drugs were used routinely in high doses ("barbiturate coma"). However, no improvement in outcome was demonstrable, and vitally dangerous side effects, such as infection, pulmonary dysfunction, arterial hypotension, and renal failure often occurred. High-dose barbiturate therapy is therefore only indicated in exceptional cases, such as refractory increase in ICP with preserved CO2 response of cerebral vessels. The effect is dependent on CMR at the start of this therapy. Benzodiazepines are frequently used in patients with head injury. They cause only a moderate decrease of CMR and ICP. In general, side effects are negligible. However, a possible decrease of MAP by reduced central sympathetic drive has to be taken into account. Opioids are also frequently used in patients with head trauma. The observed cerebral effects are inconsistent. Some authors have described increases in ICP, CBF, and CMR, but in most studies no influence on these values, or a decrease, has been observed. In any case, cautious titration of these drugs and cerebral monitoring are therefore desirable. As with benzodiazepines, a decrease in MAP due to central effects is possible. In addition, opioids inhibit bowel motility. Ketamine is generally used because of its favourable circulatory effects, bronchodilatation and absence of inhibition of bowel motility. In patients with increased ICP, however, it is often considered contraindicated, since it can be associated with cerebral vasodilation and ICP increase. Other studies did not confirm an increase of ICP when controlled ventilation and additional sedation were applied. More recent studies have demonstrated the role of neuroexcitatory NMDA-receptors in ischaemic and traumatic brain damage. Since ketamine exerts an antagonistic effect on N-methyl-D-aspartate receptors (NMDA) and studies in animals have demonstrated a protective effect of ketamine against ischaemic and traumatic brain damage, controlled clinical studies in patients with head injury are desirable. Propofol results in a profound decrease of CMR and a significant decrease of ICP, but often also in haemodynamic depression. Few results obtained during long-term administration are available, but it seems to be beneficial. More clinical studies are warranted. Gamma-hydroxybutyrate (GHB) is a physiological substance, which has only sporadically been investigated for sedation in patients with head trauma. The few available studies show beneficial res