Cerebrovascular response to nitrous oxide

Effects of remifentanil on in-hospital mortality and length of stay following clipping of intracranial aneurysm: a propensity score-matched analysis

BACKGROUND

Remifentanil is an ultrashort-acting µ-opioid receptor agonist and is especially suitable for neuroanesthesia. We previously reported that general anesthesia with remifentanil for brain tumor resection was associated with lower postoperative mortality and shorter postoperative length of stay (LOS) when compared with surgeries without remifentanil. This phenomenon may also exist during clipping of intracranial aneurysms (ICAs), where brain tissue frequently suffers ischemia and reperfusion injury. We performed a propensity score-matching study to compare in-hospital mortality and postoperative LOS with and without remifentanil in such patients.

METHODS

We used the Diagnosis Procedure Combination inpatient database in Japan that includes 926 acute care hospitals to identify patients who underwent clipping of ICAs under general anesthesia between July and December 2007.

RESULTS

Of the 4502 patients who underwent ICA clipping, 1380 propensity-matched pairs (n=2760) were included for outcome comparison. The remifentanil group had significantly lower in-hospital mortality than the nonremifentanil group (4.2% vs. 7.7%; P<0.001). Use of remifentanil was an independent factor for lower in-hospital mortality (odds ratio=0.52; 95% confidence interval, 0.37-0.74; P<0.001). By contrast, postoperative LOS did not differ significantly between the 2 groups. There was no difference in the occurrence of postoperative complications except for hydrocephalus, which was more common with remifentanil.

CONCLUSIONS

This retrospective observational study demonstrated a possible relationship between the use of remifentanil for neuroanesthesia and reduced mortality of patients undergoing clipping of ICAs with open craniotomy. Prospective interventional studies are necessary to confirm this relationship.

Effect of nitrous oxide use on long-term neurologic and neuropsychological outcome in patients who received temporary proximal artery occlusion during cerebral aneurysm clipping surgery

BACKGROUND

The authors explored the relationship between nitrous oxide use and neurologic and neuropsychological outcome in a population of patients likely to experience intraoperative cerebral ischemia: those who had temporary cerebral arterial occlusion during aneurysm clipping surgery.

METHODS

A post hoc analysis of a subset of the data from the Intraoperative Hypothermia for Aneurysm Surgery Trial was conducted. Only subjects who had temporary arterial occlusion during surgery were included in the analysis. Metrics of short-term and long-term (i.e., 3 months after surgery) outcome were evaluated via both univariate and multivariate logistic regression analysis. An odds ratio (OR) greater than 1.0 denotes a worse outcome in patients receiving nitrous oxide.

RESULTS

The authors evaluated 441 patients, of which 199 received nitrous oxide. Patients receiving nitrous oxide had a greater risk of delayed ischemic neurologic deficits (i.e., the clinical manifestation of vasospasm) (OR, 1.78, 95% confidence interval [CI], 1.08-2.95; P = 0.025). However, at 3 months after surgery, there was no difference in any metric of gross neurologic outcome: Glasgow Outcome Score (OR, 0.67; CI, 0.44-1.03; P = 0.065), Rankin Score (OR, 0.74; CI, 0.47-1.16; P = 0.192), National Institutes of Health Stroke Scale (OR, 1.02; CI, 0.66-1.56; P = 0.937), or Barthel Index (OR, 0.69; CI, 0.38-1.25; P = 0.22). The risk of impairment on at least one test of neuropsychological function was reduced in those who received nitrous oxide (OR, 0.56; CI, 0.36-0.89; P = 0.013).

CONCLUSION

In this patient population, use of nitrous oxide was associated with an increased risk for the development of delayed ischemic neurologic deficits; however, there was no evidence of detriment to long-term gross neurologic or neuropsychological outcome.

Effect of Xenon on elevated intracranial pressure as compared with nitrous oxide and total intravenous anesthesia in pigs

BACKGROUND

Xenon in low concentrations has been investigated in neuroradiology to measure cerebral blood flow (CBF). Several reports have suggested that inhalation of Xenon might increase intracranial pressure (ICP) by increasing the cerebral blood flow and blood volume, raising concerns about using Xenon as an anesthetic in higher concentrations for head-injured patients. A porcine study is presented in which the effects of inhaled 75% Xenon on elevated ICP, cerebral perfusion pressure and the efficacy of hyperventilation for ICP treatment were compared with nitrous oxide anesthesia and total intravenous anesthesia (TIVA).

METHODS

Twenty-one pentobarbital-anesthetized pigs (age: 12-16 weeks) were randomly assigned to three groups to receive either 4 h of Xenon-oxygen ventilation, nitrous oxide-oxygen ventilation or air-oxygen (75%/25%) ventilation, respectively. After instrumentation for parenchymal ICP measurement and ICP manipulation, an epidurally placed 6-F balloon catheter was inflated until a target ICP of 20 mmHg was achieved. After 4 h of anesthesia hyper- and hypoventilation maneuvers were performed and consecutive ICP and CBF changes were investigated.

RESULTS

Intracranial pressure and CBF increased significantly in the nitrous oxide group as compared with the controls. There was no increase of ICP or CBF in the Xenon or control group. Intracranial pressure changed in all three groups corresponding to hyper- and hypoventilation.

CONCLUSIONS

During Xenon anesthesia, elevated ICP is not increased further and is partially reversible by hyperventilation. Our study suggests that inhalation of 75% Xenon seems not to be contraindicated in patients with elevated ICP.