Pain Pearls – Nitrous Oxide

Nitrous Oxide


Introduction to Nitrous in the ED

  • Tasteless colorless gas administered in combination with oxygen
    • Maximum concentration 70% N20
  • Absorbed via pulmonary vasculature and does not combine with hemoglobin or other body tissues
  • Rapid onset and elimination
    • <60 seconds
  • Analgesic and anxiolytic agent
    • Use along with local anesthetic or other non-opioid pain medications
  • Administered via facemask
  • Only monitoring needed is pulse oximetry
  • No NPO requirements, patient can drive after administration, no IV line needed, no RN necessary at bedside
  • Nitrous is NOT procedural sedation and should be thought of as a pain medication
  • Studies show it is similar to morphine 10 mg IM
  • It works only when the patient is breathing it in and stops working immediately when the gas is off

Contraindications

  • Severe COPD or asthma
  • Active Otitis Media/Sinusitis
  • Active Bowel Obstruction
  • 1st -2nd trimester pregnancy
  • Altered level of consciousness
  • Severe Psychiatric disease
  • EtOH
  • Head Injury
  • Complex Advanced Active Cardiac Disease

Indications (really any procedural pain)

  • Laceration repair
  • Incision & Drainage
  • Wound Care
  • Foreign body removal
  • Central Venous Access
  • Peripheral venous access
  • Fecal Disimpaction
  • Adjunct for
    • Dislocations
    • Splinting

Nitrous as an adjunct

  • If using nitrous to try and reduce a joint
    • Use IN ketamine
    • Intra-articular lidocaine
  • Concomitant admin of nitrous with opioids, benzos, or propofol is considered PSA
  • If giving an IV opioid you should wait 30-45 minutes before using nitrous to avoid excessive sedation or airway issues

What do we have?

Porter Standard Flowmeter

  • Stored in the trauma bay
    • Extra tank rack across from peds resus bed
  • Must use disposable breathing circuit
    • Located next to desk in trauma bay
    • There are adults small, youth medium, and peds small
Safety Features
  • Nitrous oxide flow stops if oxygen is shut off or supply becomes limited
    • Can never supply more than 70% nitrous oxide
  • Exhaled gas is scavenged away to avoid unnecessary exposure to providers

Getting started

  • Wheel to bedside
  • Plug green oxygen tube into oxygen port in the wall (may have to remove Christmas tree)
  • The gray tube scavenging tube plug into to the suction port in the wall
  • Breathing circuit only fits one way, push big lumen tube into top (by gray bag) and the clear little tube below breathing bag

Positioning

  • Position the patient comfortably
  • Bring unit close to the patient so you can reach the dials
  • Make sure pulse oximetry is connected and you can see the waveform
  • Once the mask is on…
  • Set oxygen flow rate then titrate nitrous oxide to desired percentage
  • Watch gray breathing bag as a guide to adjust flow (titrate flow)
    • If bag is fully collapsing, increase overall flow
    • If bag is not moving, decrease overall flow
    • Once nitrous oxide percentage is set, regardless of flow rate, percentage stays the same

During The Procedure

  • Titrate nitrous oxide up and down as needed for “desired analgesia”, watch breathing bag to determine overall flow
  • Once procedure is complete, turn off nitrous oxide, allow patient to breath oxygen only for 60 seconds
    • Continue to watch breathing bag
  • Then remove mask completely

Your Done!!

  • Patient can be discharged with no driving or work restrictions
  • Throw away the breathing circuit
  • Return it to the trauma bay

REFERENCES:
  • Becker 2008
  • Babl 2015
  • Zhang 1999
  • Champman 1979
  • Jastek 1991

Special thanks to Dr. Alexis LaPietra for her contribution! Watch out for next times pain pearls…….. Haldol as an analgesic!!!

Case of the week COW #11

CC: Can’t see for 2 months

HPI: 10 year old male with no significant past medical history presents to the Emergency Dept. complaining of painless vision loss in the right eye for 2-3 months. Patient states he has been having difficulty seeing out of his right eye for 2 months despite changing positions in class, taking on and off his glasses and using eye drops. Vision loss has become progressively worse and now he can only distinguish whether lights are on or off. Mother states she did not do anything about this problem because she thought he was kidding and she didn’t’ have money or health insurance to seek medical attention. Patient has been wearing Bifocals for myopia since the age of 6, with corrective vision lenses at age 5. Denies associated trauma. Patient moved to the U.S from Nigeria 5 years ago. He lives with his mother and sister. Vaccines are up to date.

PMH/Birth History: NSVD at 39 weeks, 1 day. Birth took place in Nigeria and mother denies any infection during or after pregnancy. Following birth, patient did not have any complications such as pneumonia, eye infections or rashes.

Social History: Denies drug abuse. Denies exposure to chemicals. Denies contact with dirt, dogs or pigs. Patient did not live on a farm. As per mother, there was no domestic abuse in the family

PHYSICAL EXAM 

Vitals within normal Limits

General: In no acute distress, appears stated age.

Head: Atraumatic, normocephalic. No deformities.

Eye: Right (OD): pupil non-reactive and remains white in color and approximately 2mm. Afferent reflex is present CN II; efferent reflex is absent. There is a complete visual field defect on the right side. Visual Acuity: Can only distinguish between light and dark. Unable to count fingers at any distance or visual objects even in motion. On Fundoscopic exam, the fundus is gray/dull, with no retina visualized. ALL CONSISTENT WITH LEUKOCORIA

Respiratory: Lungs CTA bilaterally.

Cardiac: +S1/S2, no MRG, regular rate and rhythm

Abdomen: soft NT ND

Neuro exam: CN III –XII intact. No motor, sensory, vibratory, temperature or pain deficits. Gait is steady and normal, without any difficulty. Cerebellar function intact, no dysmetria bilaterally.

Extremities: Full ROM in all extremities. 5/5 strength in all extremities

Skin: No edema, rashes, lacerations, or abrasions. Skin is warm, pink, moist and intact.

LABS

CBC: Unremarkable with        WBC: 7.1     Hemoglobin: 13.5       Platelets 211.

CMP: WNL       CRP and ESR = WNL

Tonometry: IOP approx. 17-18 x 3 times

Wood lamp: No corneal abrasion, dendritic ulcers, lesions or depositions OU

Bedside U/S: Completed within 10 minutes of arrival ( Only Right eye is shown)

Working Differential Diagnosis:

  • Retinoblastoma
  • Intraocular Mass
  • Cataract
  • Syphilis
  • Parasitic infiltrate
  • Posterior Infarct

CT Max/Facial w/o Contrast to rule out intracranial pathologies: Negative for masses; positive for homologous material in the right lobe. MRI was recommended for further evaluation

ED/Hospital course:  Ophthalmologist on call was consulted, and said there was nothing more to do. Unfortunately because his vision loss was > 2 months, no life saving surgery was imminent as the retina was already detached causing ischemia to the rods and cones within it.  Patient was to follow up in ophthalmology clinic the following day. Patient’s Pediatrician was also contacted and he referred the patient to a Pediatric Ophthalmic specialist in University Hospital, with a scheduled appointment within the same week. Approximately one week ago, patient underwent surgery and the leading diagnosis was Toxocariasis as per MRI. Biopsy results to follow. As per mother, the patient is still without vision in his right eye.

LEUKOCORIA, UNILATERAL, 10 YO MALE DIFFERENTIALS

Coats disease is an exudative retinal vascular disorder characterized by retinal telangiectasias and subretinal exudation leading to serous retinal detachment. Presenting complaints include decreased visual acuity, strabismus, or leukocoria. The leukocoria in Coats disease is generally more yellow than white due to the presence of subretinal lipid. Coats disease is almost always unilateral and the vast majority of cases occur in boys. The majority of cases presenting with leukocoria are diagnosed between five and nine years of age, which is older than the majority of retinoblastoma patients.

Clinical examination: subretinal lipid and abnormal telangiectatic vessels US: demonstrates complete retinal detachment with massive subretinal lipid. Intraocular calcification is almost never present in Coats disease, another feature that helps to distinguish it from retinoblastoma.

The retinal photograph depicts bullous retinal detachment in the Left eye of a 1-year-old child with Coat’s disease simulating retinoblastoma. The magnetic resonance images confirm the diagnosis of retinal detachment and exclude retinoblastoma because of the absence of intraocular mass.

 

Toxocariasis — Toxocariasis, or visceral larva migrans, is an infection caused by the dog ascarid Toxocara canis or, less commonly, the cat ascarid Toxocara catis. There may be a history of living in an underdeveloped country, and exposure to dirt or undomesticated dogs. It occurs most commonly in children one to five years of age. Common presenting signs of toxocariasis are strabismus and poor vision. The ocular lesion is caused by the inflammatory response to the second-stage larva, which may localize in the one eye or both eyes

Chorioretinitis characteristic of toxoplasmosis. A pigmented scar is seen with an adjacent area of active chorioretinitis. The diagnosis of toxoplasmosis is based primarily on the appearance of the chorioretinal lesion rather than serologic studies. Courtesy of James T Rosenbaum, MD.

 Retinopathy of prematurity (ROP) — developmental vascular proliferative disorder that occurs in the incompletely vascularized retina of preterm infants and can lead to retinal detachment and permanent blindness. The most important risk factor for developing ROP is prematurity. There needs to be a history of prematurity, and/or mother mentions patient was on O2 for awhile.

Vitreous hemorrhage — Vitreous hemorrhage causes leukocoria when there is extensive organization of the blood into a clot before degradation. With time, the reddish hue of the blood is lost and the hemorrhage transforms into “whitish debris.” Etiology includes advanced ROP,  trauma (MOST common), leukemia or hemorrhagic disease of newborn

Retinablastoma– Retinoblastoma is the most common primary intraocular malignancy of childhood and accounts for 10 to 15 percent of cancers that occur within the first year of life. Retinoblastoma typically presents as leukocoria in a child under the age of two years. Untreated retinoblastoma is a deadly disease; however, with advances in treatment, survival in the contemporary era is >95 percent. Most common age group is birth- 2 years. Very uncommon in children over the age of 5, although 1-2 case reports have occurred in 18 year old males

 Pearls & Takeaways:

  • Leukocoria Requires further investigation – On exam, History and Diagnostic
  • The use of tonometry, fundoscopy and ocular ultrasound are an easy, noninvasive way to add to your ophthalmic exam. Slit-lamp exam could have been considered here
  • Ocular ultrasound is really cool and fun!
  • Advocate for your patients!  Make sure they have proper follow up with a specialist
  • If any abuse or neglect is suspected, be sure to turn on “Sherlock Holmes” senses and investigate.

 

Case presented by Dr. Sarah Bolan