Study of Anesthesia Techniques to Reduce Nausea and Vomiting After Jaw Corrective Surgery

Post-operative and post-discharge nausea and vomiting (PONV and PDNV) plague post-anesthesia and surgical care. This fact remains especially true for the orthognathic surgery (OS) population undergoing procedures involving the maxilla. Current data estimate that the incidence of PONV for OS patients undergoing surgery involving the maxilla is between 44% and 68% as compared to 8% to 30% in general surgical populations, despite application of conventional therapies. No one has accounted for or addressed this difference in clinical outcomes.

The implications of PONV for both individual health and overall health care system function are considerable. For individual patients, PONV can result in dehydration, wound dehiscence, intra-oral bleeding with continued swallowing of blood, significant anxiety and agitation (particularly for OS patients who often have heavy elastics closing their jaws together after surgery), and, in extreme cases, esophageal damage or the risk of pulmonary aspiration. Evidence shows fear of PONV overshadows concerns about pain in surgical patients. At the health care system level, evidence suggests PONV can significantly increase health care costs through prolonged post-anesthesia care unit (PACU) stays and unplanned hospital admissions following outpatient procedures. In one seminal study the odds ratio for unplanned admission due to vomiting after intended outpatient surgery was 3.4, an alarmingly high figure exceeded only by the odds ratios for readmission due to pain or bleeding.

Established patient-related risk factors for PONV include female gender, tobacco abstinence, and history of prior PONV or motion sickness; additional patient factors may include younger age, low American Society of Anesthesiologists Physical Status Classification System status, anxiety, and a migraine headache history. Known anesthesia technique-related risk factors include volatile anesthetic and nitrous oxide use as well as excessive IV opioid administration. High dose neuromuscular blockade reversal agents have also been implicated. Surgery-related factors include duration of surgery and type of surgery, with OS ranking among the high-risk types.

Because PONV (and PDNV) prevention and treatment for the OS population remain under-investigated domains of clinical care, the investigators seek to address this deficiency through multi-modal prophylactic therapy. As more OS procedures are performed, many on an ambulatory basis, tactics to reduce the high incidence of PONV in this surgical population become important to maximize patient safety and satisfaction and to contain costs.

The investigators' protocol will synthesize several recommendations to reduce risk of PONV. Volatile anesthetics and nitrous oxide will be avoided in favor of a total intravenous (IV) anesthetic involving propofol, neostigmine will be minimized, hydration goals will be set, and opioid sparing analgesics will be utilized. It is recommended that patients at high risk for PONV receive combination therapy with prophylactic agents from multiple classes. Among those shown to reduce PONV are 5-HT3 receptor antagonists (such as ondansetron), droperidol, and dexamethasone. Transdermal (TD) scopolamine is another effective adjunctive therapy to reduce PONV. Additionally, the investigators posit that the constant swallowing of small amounts of oozing blood and its retention in the stomach following OS contribute to the high incidence of PONV and PDNV in the OS population. Thus sub-bacteriostatic doses of erythromycin, capitalizing on erythromycin's established properties as a motilin agonist and thus a pro-kinetic, will be added to the evidence-based multi-modal regimen. Erythromycin has been chosen over metoclopramide due to safety profile and its well-characterized impact on gastric motility and even PONV.

Rescue anti-nausea and anti-emetic therapy will be chosen from several options at the discretion of the treating physician. Options that work through several mechanisms have been selected based on the Society of Ambulatory Anesthesia Guidelines and on data from a randomized, double-blind, placebo-controlled study of over 2000 subjects.

Anesthesia variables as well as post-operative analgesic regimens are the primary targets of the investigators' multimodal regimen. Multimodal therapy has been shown to be superior to single agent therapy. One particularly compelling example showed a 98% response rate (no PONV) vs 76% among those receiving mono-therapy and 59% receiving routine anesthesia with placebo. Despite these reported successes, PONV remains a major problem for patients undergoing OS and many other procedures. This study represents one step towards understanding and addressing this significant peri-operative problem.

This proposed study will compare a cohort receiving a multimodal regimen with a retrospective control cohort reviewed in an IRB-approved study at the same institution. The investigators' re-use of the data adds no risk of harm or disclosure to the control subjects. Utilization of this retrospective control has an important advantage over a concurrent control: It allows comparison to a group treated at the same institution without the potential introduction of bias by alerting practitioners to the extent of the PONV problem in OS. The investigators believe that, as the under-recognition of the OS group as high-risk likely contributes to the high rate of PONV these patients experience, education of the anesthesia community introduces a potential confounding variable. Further, comparing practice "as is" to the proposed protocol maximizes generalizability to other institutions. If, as anticipated, significant reductions in PONV and PDNV experience are found, prospective randomized trials to tease out nuances of contributing factors could be undertaken.

Potential influencing patient- and surgery-related variables will be collected to allow comparison of the two cohorts using logistic regression analyses.

Even less well understood than PONV is PDNV; additional studies are needed to deepen understanding of the risk factors and treatment options for PDNV. A prior study from the investigators' institution demonstrated a high incidence of PDNV in the OS population - 43% experienced nausea and 23% vomited after discharge in contrast to general reported rates of 17% PDN and 8% PDV. This study should offer additional insight into PONV's less understood counterpart through diary review of patient's self-reported experience of PDNV following discharge from direct medical supervision.