Devita, Hellman, and Rosenberg's Cancer

LWBK1006-45 LWW-Govindan-Review December 13, 2011 15:32

570 DeVita, Hellman, and Rosenberg’s CANCER: Principles and Practice of Oncology Review

Answer 45.18. The answer is D.

Development of tolerance to opioids is not well understood but is gener-

ally suspected when patients on a previously stable dosage begin to require

more frequent doses. Often, there is simultaneous disease progression,

complicating the issue of tolerance. However, incomplete cross-resistance

among opioids often allows for “opioid rotation” and achievement of

effective analgesia. Methadone is known to bind to NMDA receptors in

the brain, in addition to opioid receptors. This may be one of the mecha-

nisms that explain dramatic dose reductions when a patient’s medication

is switched from morphine or hydromorphone to methadone.

Answer 45.19. The answer is D.

In addition to commonly used classes, such as antidepressants and anti-

convulsants, the use of local anesthetics has demonstrated some efficacy

in the management of chronic neuropathic pain. Mexiletine is the oral

local anesthetic for which there is pilot data to support analgesic efficacy.

The starting dose is low, at 150 mg/d, with gradual titration. Epidural

local anesthetics (lidocaine and bupivacaine) have been widely used to

manage refractory neuropathic pain, either alone or with opioid.

Answer 45.20. The answer is B.

Continuous epidural low-dose infusion of local anesthetic via a pump is

associated with development of tolerance within days to weeks, limiting

long-term use. It is most useful in patients who experience acute pain cri-

sis or in patients in whom the use of spinal opioids is considered but who

have developed tolerance from large doses of systemic opiates. Temporary

use of this technique allows for reducing systemic opioids doses, there-

fore partially reversing tolerance. Celiac ganglion block is reported to be

effective in 70% to 85% of appropriately selected patients. Cordotomy is

associated with a 10% to 20% risk of ipsilateral motor weakness, which

results from inadvertent extension of the lesion anteriorly to involve cor-

ticospinal tract.

Answer 45.21. The answer is D.

This patient is nearing the end of life. The goal is to control any symptoms

that he is experiencing. Possible causes of his dyspnea include anxiety,

tumor infiltration, and other cardiac and pulmonary conditions. Patients

with continuous dyspnea benefit from opioids; if the patient is no longer

able to take pills, opioid drips can be very effective. For patients with

perceived anxiety, anxiolytics should be added. Haldol can also be useful

to control symptoms of agitated delirium.

Answer 45.22. The answer is D.

Among the many metabolic abnormalities seen in patients with cachexia,

the total body water and serum free lipids are increased and there is insulin

resistance.