-The effect of ondansetron on intracranial pressure and cerebral perfusion pressure in neurosurgical patients-

Anesthetic management of labor and delivery in patients with elevated intracranial pressure

The anesthetic management of labor and delivery in patients with elevated intracranial pressure is complex. This review discusses the etiologies of diffuse and focal pathologies which lead to elevated intracranial pressure in pregnancy. The role of neuraxial and general anesthesia in the management of labor and delivery is also examined. Finally, a comprehensive review of strategies to minimize increases in intracranial pressure during general anesthesia for cesarean delivery is presented.

Remifentanil-induced cerebral blood flow effects in normal humans: dose and ApoE genotype

BACKGROUND

Opioids have been linked to limbic system activation and, in animals, to neurotoxicity. Limbic system nonpharmacologic activation patterns have been linked to the Apolipoprotein E (ApoE) allelic distribution. We tested the hypothesis that, in the absence of surgery, small doses of remifentanil produce limbic system activation in humans which varies with dose and ApoE genotype.

METHODS

Twenty-seven ASA I-II volunteers received a remifentanil (Ultiva) infusion at four sequentially increasing doses: 0, 0.05, 0.1, and 0.2 microg x kg(-1) x min(-1) while receiving 100% oxygen. Cerebral blood flow (CBF) was measured at each dose globally and in the amygdala, cingulate, hippocampus, insula, and thalamus regions by pulsed arterial spin labeling magnetic resonance imaging. ApoE single nucleotide polymorphisms were determined in each subject.

RESULTS

Significant dose-related CBF increases, without correction for Paco(2), were detected in all areas. After normalizing for global CBF to correct for Paco(2) effects, the remifentanil-mediated increased CBF in the cingulate persisted, with decreased flow occurring in the hippocampus and amygdala. All these Paco(2)-corrected effects were reversed in the presence of the ApoE4 polymorphism.

CONCLUSION

Remifentanil at sedative doses produces both activating and depressing effects in various limbic system structures. The cingulate cortex seems to have the most susceptibility to remifentanil activation, and ApoE4 seems to produce relative activation of the hippocampus and amygdala.

Awakening management after neurosurgery for intracranial tumours

PURPOSE OF REVIEW

Major complications after intracranial surgery occur in 13-27% of patients. These complications may have multiple causes, but a body of arguments suggests that the haemodynamic and metabolic changes of anaesthesia recovery may be responsible for intracranial complications. The aim of this review is to explain the rationale of this hypothesis and analyse the recent studies relevant to neuroanaesthesia recovery.

RECENT FINDINGS

Rapid recovery and extubation after intracranial tumour surgery is desirable in order to make an early diagnosis of intracranial complications. Since light pharmacological sedation may worsen a neurological deficit, short-acting anaesthetics are preferable intraoperatively. Extubation in the operating room, however, may be associated with agitation, increased oxygen consumption, catecholamine secretion, hypercapnia and systemic hypertension. This may exacerbate cerebral hyperaemia observed even during an uneventful recovery, leading to cerebral oedema or haemorrhage.

SUMMARY

Pain, hypothermia, hypercapnia, hypoxia, hypoosmolality, hypertension, and anaemia should be avoided during emergence. Early emergence is associated with minimal haemodynamic and metabolic changes. If there is any doubt as to whether the patient should be extubated in the operating room, a gradual emergence in the intensive care unit makes it possible to decide whether or not extubation can be performed safely.

Randomized, double-blind, crossover, placebo-controlled trial of intravenous ondansetron for the prevention of intrathecal chemotherapy-induced vomiting in children

BACKGROUND

The purpose of this study was to determine the effectiveness of intravenous ondansetron in preventing vomiting after the administration of intrathecal chemotherapy in children.

PATIENTS AND METHODS

Twenty-six children (ages 18 mo to 15 y) receiving intrathecal chemotherapy with either methotrexate or the combination of methotrexate, hydrocortisone, and Ara-C for the prophylactic treatment of central nervous system leukemia were randomly assigned to receive an infusion of normal saline or ondansetron at one of two doses (0.15 or 0.45 mg/kg) 30 minutes before undergoing the procedure. One hundred forty-six infusions were administered (51 placebo, 47 at the lower ondansetron dose, and 48 at the higher dose). Each patient acted as his or her own control, and each patient was studied at least three times.

RESULTS

Twenty-three of 26 patients (88.5%) had postprocedural vomiting on at least one occasion. At least one episode of vomiting occurred during the 24 hours after the procedure in fifty-two of the procedures (35.6%). The incidence of vomiting was significantly greater after infusion of placebo than after either low-dose or high-dose ondansetron. The likelihood of severe vomiting was even more significantly reduced by the preadministration of ondansetron. Almost all of the intrathecal treatments associated with severe vomiting occurred after the infusion of placebo.

CONCLUSIONS

Vomiting induced by intrathecal chemotherapy can be greatly reduced by the intravenous administration of ondansetron before the procedure, and severe vomiting can be virtually eliminated.

Randomized prospective double-blind placebo-controlled trial of effect of intravenous ondansetron on intraocular pressure during ophthalmic surgery

The effect of i.v. ondansetron, before induction of anaesthesia, on intraocular pressure (IOP) in patients undergoing cataract surgery was investigated. Forty patients (two groups of 20) received either ondansetron 4 mg (treatment group) or 0.9% saline (placebo group) in a double-blind controlled manner. There were no significant differences in IOP between the groups. Ondansetron had no significant effect on IOP during the study period.

Monitoring in neuroanaesthesia: update of clinical usefulness

The aim of specific monitoring in neuroanaesthesia is to detect, as quickly as possible, intraoperative ischaemic insults so that the brain and the spinal cord may be protected from harmful and frequently inevitable events due to the type of surgery, patient positioning, haemodynamic changes or any intercurrent event. New monitors are being introduced into the operating theatre, but only a few are considered to be an absolute standard of care in neurosurgery, e.g. facial nerve monitoring for surgery of acoustic neuromas and recording of evoked potentials during repair of scoliosis. In the past decade, new monitoring devices have moved from the experimental stage to the operating theatre and although most are still in a phase of technological development and/or definition of their field of applicability they are being used as guides for clinical practice in those instances where cerebral well-being might be impaired. The metabolic consequences of hyperventilation, pharmacological electroencephalogram burst suppression, hypothermia, etc. can now be assessed in the operating theatre. Non-invasive monitoring is being rapidly integrated into our daily work because of its lack of secondary effects. Nevertheless, each new development is regarded as an addition rather than as a substitute for existing equipment. The perfect combination of monitors to provide essential information during an individual surgical procedure to influence a better patient outcome, is still uncertain and needs extensive clinical research.