Meeting Reviews

Acute Pain and Regional Anesthesia

By Franklin Chiao, MD and Sophie Pestieau, MD

L-R: R. Scott Dingeman, MD, FAAP; Doralina Anghelescu, MD; Franklin B. Chiao, MD; Rosalie Tassone, MD, MPH; Peter Marhofer, MD; Stefan J. Friedrichsdorf, MD

This year's acute pain and regional anesthesia component of the SPPM Annual Meeting featured four engaging speakers discussing a variety of topics from anesthetic drug impacts on cancer, innovative regional anesthesia for reducing opioid consumption and a nitrous oxide for procedural pain management pro/con debate. 

Doralina Anghelescu, MD from St. Jude Children's Research Hospital spoke about how anesthetic agents impact oncology.  Opioids, alpha-2 agonists, ketamine, volatile anesthetic gases, local anesthetics, and propofol have been studied.  Outcomes are divided into animal studies, clinical studies, and cellular studies.  Confounders in clinical studies are surgical stress, blood transfusions, hypothermia, and postoperative pain. 

Immune function is invariably affected by surgery. Surgery itself causes immunosuppression as well as all anesthetic drugs besides local anesthetics which can actually be immunoprotective.  Immunosuppression mechanisms stem from activation of the hypothalamic-pituitary-adrenal axis and sympathetic nervous system. 

Anesthetic drugs also cause immunosuppresion.  In a paper by Melamed 2003, ketamine was shown to increase metastasis most potently.  Not all opioids immunosuppress through the same mechanisms.  Hydromorphone for example, does not decrease NK cell activity, but morphine does.  Alpha-2 agonists have had mixed results.  Clonidine decreased lung metastases in all non-operated animals, but other studies have shown increased tumors. 

Local anesthetics are immunoprotective through several mechanisms. NK cell numbers increase, cancer cell apoptosis occurs, lung adenocarcinoma cell invasion is inhibited, and lower metastatic progression in breast tumor cells occurs.  Lidocaine infusions have shown attenuated immune changes, lower inflammation, and improved pain control.  Regional anesthesia is largely a method that is more beneficial than general anesthesia for oncology patients.  The majority of studies show either lower or unchanged cancer rates. 

Some other anesthetic drugs have benefits in cancer patients.  Ketorolac and cox-2 inhibitor patients have lower rates of breast and colorectal cancer.  Methadone inhibits lung cancer cell proliferation and induces necrotic-like cell death in neuroblastoma. 
Peter Marhofer, MD from the Medical University of Vienna, Austria, subsequently showed us how to customize regional anesthesia procedures for inimizing opioid administration post-operatively. He discussed in depth how the use of ultrasound in pediatrics has evolved and how it can improve our daily clinical practice. By performing specific regional anesthesia techniques tailored to the surgical procedure, practitioners can selectively block nerve territories, and therefore minimize the need for general anesthesia or sedation.

Stefan Friedrishdorf, MD from Children's Minnesota, and Rosalie Tassone, MD from Palm Beach Children's Hospital, gave an exhilarating pro-con debate about nitrous gas and procedural pain management.  In the pro argument, there was first a discussion about how much children fear needles and pain.  Using restraints is never supportive and makes children feel powerless.  In addition, lack of analgesia for procedures diminishes the impact of analgesia at subsequent procedures.  Continuous pain can also cause post-traumatic stress disorder and some organizations claim pain management is a human right.  Several studies show the effectiveness of nitrous oxide for pain management.  40-70% nitrous lacks risks of moderate sedation.  Nurse- administered programs exist across the country.  Children also do not need to be NPO.

Dr. Tassone discussed several side effects of nitrous oxide.  It decreases myocardial contractility, increases pulmonary vascular resistance, increases renal vascular resistance, decreases GFR, increases cerebral glucose metabolism, increases cerebral blood flow, blocks synthesis of folate, increases pneumothorax, increases pneumoencephalus, increases gas in bowel, and increases middle ear pressure.  The ENIGMA trials also show it increases nausea and vomiting.  Of note, it is a greenhouse gas and destroys the ozone layer. 

The speakers concluded with some highlights of their discussion.  Analgesic treatment is mandatory for children when they undergo painful procedure. Be aware of nitrous side effects - scavenging is paramount.  Nitrous gas analgesia and sedation outside OR can be offered - but for low risk patients only.  Nurse- administered programs can function well.  In resource-rich countries the decision for lumbar puncture analgesia will be increasingly between moderate-deep sedation using propofol and mild sedation using nitrous gas plus topical anesthesia.  Future prospective studies need to explore the benefits and risks of propofol anesthesia versus N2O sedation for children (especially with malignancies undergoing lumbar punctures and other painful procedures).