Sat27November0556PM 38

Some anaesthetic agents and analgesics modulate the immune system and may have some effect on tumour recurrence following cancer surgery.

Which one of the following drugs is most likely to suppress natural killer (NK) cell function in the postoperative period?

(Please select 1 option)

Morphine This is the correct answer

Tramadol

Propofol

Parecoxib

Lidocaine Incorrect answer selected

Explanation

Natural killer (NK) cells are lymphocytes (CD32 CD562+) are components of the innate immune response and play an important role in the defence against cancer cells.

In recent years from animal and human studies, it has become apparent that:

Suppression of NK cell activity increases the risk of metastatic cancer

Surgery suppresses NK cell activity through mechanisms not yet defined but the choice of analgesic or anaesthetic agents may contribute to these changes. These changes can last several days after surgery.

Pain and stress suppress NK cell activity

Morphine causes suppression of NK cell activity and T cell differentiation promotes lymphocyte apoptosis and decreases toll-like receptor-4 (TLR4) expression on macrophages. Likewise, fentanyl, alfentanil, sufentanil and remifentanil decrease NK cell activity but increase the numbers of regulatory T cells. Tramadol, however, does not suppress the immune function. It differs by increasing NK cell activity and facilitate the production of interleukin 2 (IL-2).

COX2 inhibitors are thought to attenuate NK cytotoxicity. Preoperative treatment with non-steroidal anti-inflammatory drugs increases infiltration of activated immune cells into colorectal cancer tissue.

Propofol is thought to inhibit cancer cell invasion, proliferation and the potential for metastatic growth. Propofol also influences cancer cell apoptosis in tumours such as non-small cell lung cancer, colon cancer, breast and ovarian cancers. Unlike propofol, halothane sevoflurane, ketamine and thiopentone suppress NK cell activity, whereas isoflurane attenuate experimental NK cell numbers.

Lidocaine is a membrane stabiliser. Clinical concentrations can directly inhibit epidermal growth factor (EGF) receptors and the proliferation of tumour cells. It can also reduce the invasiveness of cancer cells. In vitro experiments found that ropivacaine can inhibit the growth of tumour cells.

Answer Statistics

1

36%

2

6%

3

16%

4

31%

5

14%

Times answered: 236