Low Dose Ketamine Infusion for Analgesia in the Emergency Department to Reduce Side Effects

Inclusion criteria: * Patients aged 18 or older * Primary complaint of acute moderate to severe pain on VAS/ numeric pain scale (a score of ≥5cm which corresponds to 50mm). * Pain described as abdominal, flank, back, musculoskeletal, or traumatic chest pain * Must be alert and oriented times three * Able to provide consent Exclusion criteria: * Pregnant * Breastfeeding * Altered mental status * Known or reported allergy, hypersensitivity or intolerance to ketamine * Unstable vital signs (systolic blood pressure \<80 or \>180mmHg, heart rate \<50 or \>150 beats per minute, and respiratory rate \<10 or \>30 breaths per minute) * History of unstable heart disease, such as arrhythmias, congestive heart failure, or coronary heart disease. * History of untreated or uncontrolled thyroid disease * Acute head or eye injury * Active or current use of alcohol or drugs * Known intracranial hypertension * Hepatic or renal insufficiency * Current active manic phase of bipolar disorder * Active delusions, hallucinations, or schizophrenia * Patients who have recent fentanyl use within 60 minutes or other analgesic use (opiates) within 4 hours of study enrollment (signing of consent) * Patients who have enrolled in the study during a previous ED encounter * Chronic use of opiates (i.e.: fentanyl patch, SR opiates)