Neurology Advisor · February 13, 2018
Parkinson disease (PD) affects an estimated 1 million people in the United States and 10 million individuals worldwide. PD develops in more than 80% of patients after the age of 60 years, and it is anticipated that the prevalence will increase as the elderly population continues to expand.
PD has been linked with increased rates of perioperative morbidity and mortality, with one study finding more than twice the 3-month mortality rate among patients with PD compared with patients without PD after hip fracture surgery. “Complications commonly arise from the impact of disease on the respiratory, cardiovascular, and neurological systems, with rates of postoperative aspiration pneumonia, bacterial infections, urinary tract infections, and falls significantly increased in this population,” wrote the authors of a recent review published in the Journal of Clinical Neuroscience.
Anesthetic medications have been identified as a potential cause of morbidity in this population because of their interaction with the drugs used to manage PD. As such, there are special considerations regarding the risk of anesthesia in these patients when undergoing surgery. First, to avoid symptom exacerbation and other adverse effects, it is recommended that the usual drug regimen continue until just before the induction of anesthesia. This is especially critical in patients taking levodopa because of the drug’s short half-life. During procedures requiring extended anesthesia, levodopa can be administered by means of a nasogastric tube.
The commonly used anesthetic drug propofol has been reported to demonstrate dyskinetic effects in individuals with and without movement disorders, including PD. Propofol increases striatal levels of gamma-aminobutyric acid (GABA), and “increased concentrations of GABAA receptors have been observed postmortem in the globus pallidus internus of parkinsonian patients prone to dyskinesia, indicating that these patients may be more sensitive to the effects of GABA,” according to the review.
Other research has found that propofol inhibits neuronal activity in the subthalamic nucleus, and that “lesions of the [subthalamic nucleus] can result in disorders of excessive movement such as ballism and chorea, potentially implicating this mechanism of action as underlying the ‘choreic’ movements observed in a patient with PD after administration of propofol.”
Nonetheless, propofol is often used in patients with PD undergoing surgery because of its favorable anesthetic properties. However, clinicians should remain aware of the increased risk for propofol-induced dyskinesia in this group, especially in those with advanced disease. As described in a report published in 2006, dexmedetomidine was found to manage propofol-induced dyskinesia successfully in a patient with PD undergoing deep brain stimulator placement.
For short-term treatment of sialorrhea caused by impaired swallowing, which may worsen during anesthesia, glycopyrrolate by mouth and ipratropium spray have been shown to be effective.
Several general anesthetic agents may influence dopamine transmission, including halothane and isoflurane, which may “increase the concentration of extracellular dopamine and its metabolites in the rat striatum, possibly by inhibiting the action of the dopamine transporter,” as stated in the review.
In addition, halothane has been reported to increase cardiac sensitivity to catecholamines and should not be used in patients taking levodopa. Sevoflurane, enflurane, and isoflurane have been suggested as safer alternatives to halothane.
To glean the top takeaways on this topic, Neurology Advisor spoke with one of the authors of the review, Simon JG Lewis, MBBCh BSc MRCP FRACP, professor of cognitive neuroscience at the University of Sydney and Royal Prince Alfred Hospital in Australia.
Neurology Advisor:What is the overall message regarding the use of anesthesia in patients with PD?
Dr Lewis: Most patients will tolerate general anesthesia very well, but it is clear that in more advanced cases of PD, special consideration will need to be given to the timing of medications pre- and post-surgery [and] the potential for neuropsychiatric problems such as psychosis and confusion. [There should also be] a clear plan for [safe] rehabilitation of the patient.
NA:When anesthesia is necessary in these patients, how can complications be minimized?
Dr Lewis: Information is power. The more the [patient’s care] team knows about the patient, the better the outcomes will be. Many of the problems around general anesthetic are predictable. For example, if the patient is likely [not to receive nutrition] by mouth for a few days postoperatively, clinicians will need to think about managing the administration of PD medications.
In contrast, if preoperatively a patient is known to have neuropsychiatric features like cognitive impairment and hallucinations, the [person is] very likely to have postoperative delirium with agitation. Agreeing on a management plan across the specialties involved prior to surgery [is strongly advised].
NA:What should be the focus of future research in this area?
Dr Lewis: While patients understand the need for surgery, it would be good to be able to offer them more rigorous reassurances. Prospectively constructed, multicenter trials with well-documented outcome data focusing on both the short- and long-term consequences of general anesthesia on motor and non-motor aspects of PD would be highly beneficial.