1. Adult patients 18 years or older 2. Individuals undergoing either a mastectomy or mastectomy with tissue expander for which the anesthetic plan includes a serratus anterior plane block. 1. Any known sensory deficit of the anterolateral chest wall. 2. Any local disorder of the skin or otherwise where blockade is to be performed which would prevent safe performance of the block 3. Pregnancy 4. American Society of Anesthesiology classification greater than 3 5. Allergy to amide local anesthetic medications 6. Chronic pain conditions 7. Preoperative opioid use greater than 20 oral morphine equivalents per day 8. Any coagulation abnormality which would be a contraindication for block placement 9. Preoperative chronic renal dysfunction requiring renal replacement therapy or a serum creatinine greater than 1.4 mg/dL 10. Body mass index >50 11. Incarceration 12. Inability to understand study procedures including inability to understand the English language 13. Inability to provide adequate informed consent 14. Refusal to participate in the study

• Adult subjects aged 18 years or older
• Scheduled for elective posterior lumbar spinal fusion surgery between 1 and 3 levels
• Baseline cognitive deficits sufficient to make objective pain self-assessments unreliable in the estimation of the Study Investigators.
• Immunocompromised subject
• Coagulopathy
• Severe liver and renal dysfunction
• Preoperative neurological deficits
• The dura damage during surgery
• Inability to follow directions or comprehend the English language.
• Females who are pregnant as determined by positive pregnancy test on or before the day of surgery.
• Prisoners.
• Patient refusal to provide informed consent.
• Allergy to amide local anesthetics (lidocaine, bupivacaine, ropivacaine) or opioid (fentanyl) allergy if patient assigned epidural analgesia.
• Hydromorphone allergy if patient assigned IV PCA

• 18-75 years old
• ASA 1-2
• BMI 19-35 kg/m2
• Patients undergoing surgery with general anesthesia with sevoflurane- fentanyl
• Planned abdominal or spinal surgery lasting 1-3 hours
• Willing and able to consent in English or Spanish
• No current history of advanced pulmonary or cardiovascular disease
• Age less than 18 or older than 75
• Patient does not speak English or Spanish
• Patient refusal
• Monitored anesthesia care (MAC) or regional anesthesia planned
• Pregnant or nursing women
• "Stat" (emergent) cases
• ECG rhythm other than regular sinus rhythm
• Implanted pacemakers
• On antimuscarinic agents, alpha 2 agonists, antiarrhythmics, or beta blockers
• Presence of pacemaker
• Autonomic nervous system disorder
• Use of chronic opioids

1. Is male or female <2 years of age at the time of surgery. 2. Must weigh at least 3 kg. 3. Is scheduled to have a surgical procedure for which opioid analgesia will be needed to manage postoperative pain for at least 18 hours following intraoperative and/or postoperative IV analgesia. 4. Is generally healthy as documented by medical history; physical examination (including, but not limited to, the cardiovascular, gastrointestinal, respiratory, and central nervous systems); vital sign assessments; 12-lead electrocardiograms (EKGs); clinical laboratory assessments; and general observations. Any abnormalities or deviations from the acceptable range that might be considered clinically relevant by the study physician or investigator will be evaluated on a case-by-case basis, agreed upon by the Principal Investigator (or sub-investigator), and documented in study files before enrolling the subject in the study. 5. The subject's parent or guardian has been informed of the nature of the study and has provided written informed consent. Postoperative: 6. Is anticipated to require an analgesic regimen using a short-acting opioid (non-oxycodone and non-oxymorphone) analgesic after surgery (according to standard of care (SOC) as defined in the protocol). 7. Is an inpatient expected to be hospitalized for 24 hours after dosing with study drug. 8. Has an indwelling access catheter for blood sampling. 9. Has demonstrated the ability to tolerate clear fluids following surgery according to the SOC at each institution. All infants and children should be able to demonstrate strong suck and swallow reflexes and neurologic alertness and stability sufficient to handle oral secretions. The ability to tolerate small amounts (1 to 2 oz.) of clear liquids without emesis (over 30 to 60 minutes) would support readiness for study participation and oral intake once the physician has ordered the diet advanced to clear liquids and the subject has ingested fluids by mouth without nausea or vomiting. 1. Has the presence or history of a clinically significant disorder involving the cardiovascular, respiratory, renal, gastrointestinal, immunologic, hematologic, endocrine, or nervous system(s) or psychiatric disease that would contraindicate participation, as determined by the Investigator. 2. Has any clinical laboratory test result outside the accepted range that has been confirmed upon re-examination and deemed to be clinically significant. 3. Has a clinically significant illness or condition any time before dosing with study drug that would contraindicate participation, as determined by the Investigator. 4. Has a life expectancy <8 weeks. 5. For age groups A and B: Has a malabsorption, gastroenterologic, or abdominal condition that would interfere with the absorption of study drug. 6. Has evidence of increased intracranial pressure. 7. Has a respiratory condition requiring intubation or resulting in active bronchiolitis, asthma, stridor, or difficulty breathing due to congestion and increased nasal secretions, including oxygen (O2) saturation ≤92%. 8. Has a history of seizures. 9. Subject (and/or mother if subject is nursing) has used medications with actions characteristic of monoamine oxidase inhibitors (MAOIs) within 14 days before the start of the study drug is prohibited. Standard daily pediatric multivitamins may be taken until enrollment into the study but will be restricted during the study. 10. Subject (and/or mother if subject is nursing) has received preoperative opioids for more than 72 consecutive hours. 11. Subject (and/or mother if subject is nursing) has received oxycodone or oxymorphone within 48 hours prior to screening. 12. Subject (and/or mother if subject is nursing) has ingested caffeine- or xanthine-containing products (eg, theophylline) within 48 hours before dosing. These products are also prohibited during periods when blood samples are collected. 13. Has a history of relevant drug allergies, food allergies, or both (ie, allergy to oxymorphone or other opioid analgesics) that could interfere with the study. 14. Parent or legal guardian is unable to provide consent for any reason (eg, mental or physical disabilities, language barriers, or is unavailable). 15. Subject (and/or mother if subject is nursing) has participated in a clinical study of an unapproved drug within the previous 30 days. 16. Is not suitable for entry into the study in the opinion of the Investigator.

• Younger than 2 years (chronological age)
• Scheduled for anaesthesia that is expected to last at least 2 hours (and/or total operating room time is scheduled to be at least 2.5 hours)
• Has a legally acceptable representative capable of understanding the informed consent document and providing consent on the participant's behalf.
• Known neurologic, chromosomal or congenital anomaly which is likely to be associated with poor neurobehavioural outcome
• Existing diagnosis of behavioural or neurodevelopmental disability
• Prematurity (defined as < 36 weeks gestational age at birth)
• Birth weight less than 2 kg.
• Congenital cardiac disease requiring surgery
• Intracranial neurosurgery and intracranial craniofacial surgery (isolated cleft lip is not an exclusion)
• Previous cumulative exposure to general anaesthesia exceeding 2 hours
• Planned future cumulative exposure to anaesthesia exceeding 2 hours before the age of 3 years.
• Any specific contra-indication to any aspect of the protocol
• Previous adverse reaction to any anaesthetic
• Circumstances likely to make long term follow-up impossible
• Living in a household where the primary language spoken at home is not a language in which we can administer the Wechsler Preschool and Primary School Intelligence Scale
• Planned postoperative sedation with any agent except opioids (e.g. benzodiazepines, dexmedetomidine, ketamine, barbiturates, propofol, clonidine, chloral hydrate, and other non-opioid sedatives). For example if such sedation is planned for post-operative ventilation

• 18-70 years old
• ASA physical status classification 1 to 3
• Personal history of cocaine abuse
• Scheduled for a non-emergent operation that requires general anesthesia
• Vital signs within generally accepted ranges for normal [HR 60-100, RR 12-20, SpO2 > 96% on room air, BP 90-140/60-90 unless a diagnosis of hypertension is present, T 36-38 degrees)
• Willing and able to consent in English or Spanish
• Age less than 18 or older than 70
• Unable to give informed consent for participation in the study
• Patient refusal
• Monitored anesthesia care (MAC) or regional anesthesia planned
• Pregnant or lactating
• Emergent surgery
• Acute cocaine intoxication based on clinical symptomatology (hypertension, tachycardia, agitation, delirium, hyperthermia)
• History of cardiac disease including coronary artery disease (CAD) and cardiac dysrhythmia
• History of stroke
• History of seizure disorder
• ESRD
• Prison patient

Inclusion Criteria 1. Males or females age 0 to <12 months. 2. Scheduled for non-cardiac surgery or procedure lasting longer than 30 minutes under general anesthesia where oral endotracheal intubation will be performed by an anesthesiology clinician. 3. Subject/Parental/guardian permission (informed consent). Inclusion for clinician participants: 1) Pediatric anesthesia attending, pediatric anesthesia fellows, and anesthesia resident Exclusion Criteria 1. History of difficult intubation 2. History with abnormal airway 3. Predictive of difficult intubation upon physical examination 4. Parents/guardians who, in the opinion of the investigator, may be unable to understand or give informed consent