Delayed arousal

Dopamine D1 receptor in the NAc shell is involved in delayed emergence from isoflurane anesthesia in aged mice

BACKGROUND

Delayed emergence after general anesthesia tends to occur in the elderly population, but the mechanism remains unclear. Apart from age-related pharmacokinetic changes, the aging-induced structural and functional alterations in the arousal-promoting neural substrates should be considered. The nucleus accumbens (NAc) is a crucial arousal-related nucleus, in which activating medium spiny neurons (MSNs) expressing dopamine D1 receptor (D1R) could facilitate the arousal from natural sleep. Meanwhile, the dopaminergic systems decline with aging in multiple brain regions. However, whether the age-related decline in D1R in the NAc shell attenuates its arousal-promoting capacity from general anesthesia remains to be elucidated.

METHODS

We first verified the delayed emergence from isoflurane anesthesia and examined the corresponding changes of electroencephalogram (EEG) power in aged mice. In turn, the arousal-modulating capacity of D1R was characterized in the young and aged cohorts by microinjection of D1R agonist/antagonist into the NAc shell. Furthermore, to address the possible mechanism responsible for the attenuated arousal-modulating capacity of the aged NAc, the expression of D1R in the NAc shell was measured and compared between young and aged mice.

RESULTS

Our data indicated that compared with young mice, the emergence time in aged mice was notably longer, while EEG power in δ band (1-4Hz) was significantly higher and power in β band (12-25Hz) was lower. Activating or inhibiting D1R in the NAc shell by microinjection D1R agonist/antagonist promoted or delayed the emergence process in young mice. Nevertheless, this modulation capacity of D1R in the NAc shell declined in aged mice, respectively. Meanwhile, downregulation of D1R expression in the NAc shell was detected in the aged brain.

CONCLUSION

Together, these results suggest that aging attenuates the arousal-modulating capacity of D1R in the NAc shell probably through downregulation of D1R expression therein, which may provide a potential explanation and a therapeutic target for increased sensitivity to anesthetics in the elderly patients.

Remifentanil Requirement for Inhibiting Responses to Tracheal Intubation and Skin Incision Is Reduced in Patients With Parkinson's Disease Undergoing Deep Brain Stimulator Implantation

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disease affecting the quality of life in the elderly. We speculated that PD patients might have abnormal pharmacodynamics due to the degenerative neural system, and the present study was performed to investigate the pharmacodynamics of remifentanil in PD patients.

MATERIALS AND METHODS

Two arms of patients were recruited, including 31 PD patients undergoing pulse generator placement after deep brain stimulator implantation and 31 pair-controlled patients undergoing intracranial surgery without PD (NPD). Patients were anesthetized with target-controlled infusion of propofol and remifentanil. The effective concentration of remifentanil to inhibit responses to intubation and skin incision in 50% and 95% patients (EC50 and EC95) was determined by the up and down method.

RESULTS

Demographic data, bispectral index, and hemodynamic values were similar between the PD and the NPD groups. The average remifentanil concentration used in the PD group for tracheal intubation is significantly lower than in the NPD group (P<0.001). The EC50 for inhibiting the response to tracheal intubation were 1.86 ng/mL (95% confidential interval [CI], 1.77-1.96 ng/mL) in the PD group and 3.20 ng/mL (95% CI, 3.13-3.27 ng/mL) in the NPD group. The average remifentanil concentration used in the PD group for skin incision is significantly lower than in the NPD group (P<0.001). EC50 for inhibiting the response to skin incision were 2.17 ng/mL (95% CI, 2.09-2.25 ng/mL) in the PD group and 3.09 ng/mL (95% CI, 3.02-3.17 ng/mL) in the NPD group.

CONCLUSIONS

The remifentanil concentrations required for inhibiting responses to tracheal intubation and skin incision are reduced markedly in PD patients undergoing pulse generator placement (NCT01992692).

Neurologic complications of anesthesia: A practical approach

Neurologic complications related to anesthesia are infrequent but can be serious. Neurologists are often consulted to evaluate patients with postoperative symptoms and must be ready to discriminate those truly caused by the anesthetic drug or procedure from the more common postoperative complications that are unrelated to the anesthesia itself. This practical review relies on cases to illustrate common reasons for neurologic consultation in the postsurgical setting. It also briefly summarizes what to expect when patients with central or peripheral neurologic disease undergo surgery under general or regional anesthesia.

Neurologic complications of anesthesia

Neurologic complications after anesthesia are relatively uncommon but occasionally severe. Intraoperative intracranial hypertension in patients with brain masses, delayed arousal, and postoperative delirium and cognitive dysfunction are among the main complications of general anesthesia. Neuropathy and transient gluteal and leg pain are the most frequent complications of regional blockade. Seizures are infrequent with both anesthesia modalities. Patients with primary neurologic disorders, such as neurodegenerative or neuromuscular conditions, can be at risk for specific complications, and the anesthesia plan must be cautiously adjusted in these patients. In the neurointensive care unit, the complications from large doses of anesthetic agents used for suppression of seizures or control of intracranial pressure are different from those seen perioperatively. Propofol infusion syndrome can be life-threatening when administered for those indications.