MEOPA
With nitrous oxide and oxygen , an equimolar mixture of gas is oxygen and nitrous oxide (N 2 O, nitrous oxide) indicates that as a short anesthesia may be used for smaller painful invasive procedures. There is no German name for the French abbreviation MEOPA (Mélange équimolaire oxygène-protoxyde d'azote), but it is available in compressed air bottles under the trade names Entonox and Livopan from Linde or as Kalinox from Air Liquide / Carbagas. In the field of paediatrics , MEOPA is sometimes referred to as “magic air”.
history
Laughing gas was discovered by Joseph Priestley as early as 1772 , the anesthetic effect was recognized by Horace Wells in 1844 and used for the first time. The mixture of equal parts with oxygen was developed in 1961 and introduced in 1965. It was initially used in Anglophone countries primarily in non-medical areas, in obstetrics and in nursing outpatient departments. From the 1990s onwards, MEOPA was increasingly used in pediatric oncology in France, where it has been approved under pharmaceutical law in inpatient areas and on ambulances since 2001.
effect
The anxiety-relieving, pain-relieving (analgesic) and amnestic effect is due to the nitrous oxide and is related to the concentration ratio to the oxygen. Below 40% nitrous oxide there is only mild to moderate analgesia, and only between 40 and 60% nitrous oxide is deep analgesia without impaired consciousness. The fixed mixing ratio at MEOPA prevents nitrous oxide overdosing, because from 60–70% consciousness is clouded with drowsiness, and from 80% (with less than 20% oxygen) it comes to heart failure due to hypoxia .
MEOPA is a transparent, colorless, non-irritating, slightly smelling, flammable gas.
With MEOPA with 50% nitrous oxide, breathing and protective reflexes are preserved. It leads to a sedation with full consciousness, the patient usually feels deeply relaxed and "withdrawn", but without falling asleep.
Since laughing gas is very volatile with little binding in the blood, the effect sets in very quickly within three minutes and the effect is completely reversible within a very short time.
indication
MEOPA is best suited for slightly to moderately painful interventions lasting up to 10–15 minutes. An increased rate of side effects has been reported when used for more than 15 minutes.
MEOPA is particularly suitable for changing dressings, especially for burn wounds, removing / applying plaster of paris, suturing, removing suture material, removing a wound drain, removing a foreign body and minor superficial surgical interventions, but also for taking blood, opening a port catheter or creating an arterial access. There have also been positive experiences with lumbar punctures, bone marrow punctures and the closed establishment of a bone fracture (fracture reduction) or a peripheral joint dislocation (dislocation).
MEOPA is also used in dental interventions and in obstetrics.
application
The application is carried out on a doctor's order, usually by trained non-medical staff according to a precisely defined scheme. The patient doesn't have to be sober. Clinical monitoring without a pulse oximeter is sufficient . If the MEOPA application is combined with an opioid or benzodiazepine (often midazolam ), however, monitoring by EKG and pulse oximeter and a doctor's presence are required.
The application takes place via a face mask with balloon and one-way valve; The mask must be adapted to the size of the face. For children, perfumed masks are often used for better acceptance, and a small plastic plane is often installed over the exhalation valve, so that the children can control and observe their breathing well.
The effect of MEOPA can be even less in children under five years of age. As a rule, MEOPA is used from the age of six months.
After three minutes of ventilation, the intended therapeutic or diagnostic intervention can be carried out.
Once the procedure is over, MEOPA can be switched off and the effect will dissipate within a few minutes. A follow-up period of around three to five minutes is therefore sufficient.
Side effects
The reported side effects are rare, mild and in all cases reversible upon termination of MEOPA application. Up to 4% of complications are reported, particularly panic attacks, headaches, hallucinations, and nausea / vomiting. On the other hand, dreams, euphoria and exhilaration were very common.
In an overview of the application in 155 interventions in children, 77% were calm and relaxed during the operation, 8% cried, 5% had “facial expressions distorted by pain”, 4% were aroused and in 5% the child had to be held. Only in two cases was there a defensive reaction from the child. In 94% parents and nurses were satisfied with the use of MEOPA. In children under five years of age, pain relief was inadequate in 30%, whereas in older children it was only 9%.
There is no risk for the nursing staff. In animal experiments, nitrous oxide was shown to be teratogenic , but no teratogenic effects are known to date in humans.
Contraindications
The use of MEOPA is limited to interventions of up to a maximum of 15 minutes, as more side effects are observed afterwards. Likewise, the analgesic effect is occasionally insufficient for very severe pain.
Contraindications include head trauma , increased intracranial pressure and an altered state of consciousness, as well as pathological accumulations of air such as pneumothorax or emphysema, as well as pulmonary hypertension , gas embolism , barotrauma , unstable circulatory conditions and a facial bone fracture.
MEOPA must not be used in the first three months after an ophthalmic surgery in which an ophthalmic gas was used and a residual amount of gas may still remain in the vitreous humor.
A vitamin B-12 deficiency must be substituted in advance.
There is no contraindication in the last trimester of pregnancy, during childbirth and during breastfeeding.
literature
- ^ A b Colette Bourgois, Henri Kuchler: Use of MEOPA for painful interventions in pediatrics. In: Pediatrica. 14, 2003, ISSN 0254-3354 , pp. 18-21, online (PDF; 94 kB) .
- ^ Kalinox - protocole d'administration pour le personnel soignant hospitalier . 04/2011. Air Liquide, Tour Ariane, 5, place de la Pyramide, 92800 Puteaux.
