[CG] GTN Nitroglycerin (Glyceryl Trinitrate) for emergency cervico-uterine relaxation

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Rapid and transient relaxation of the cervix and uterus is occasionally required to allow obstetric manoeuvres during emergencies.

A number of case reports and trials have shown nitroglycerin (Glyceryl Trinitrate) to provide rapid and transient cervico-uterine relaxation (albeit unlicensed).

The therapeutic effect is seen within 1-2 minutes of administration and lasts for 3-5 minutes.

Indications:

  • Fetal head entrapment during vaginal breech delivery.
  • When uterine relaxation is required during a difficult caesarean section.
  • Management of uterine inversion

Administration:

Maternal IV cannula requires to be sited prior to administration of GTN (the drug may cause profound drop in BP)

Sublingual via metered pump:

Nitrolingual pump spray should be primed before using it by pressing the nozzle once.

1-2 sprays (400-800 micrograms) administered as spray droplets beneath the tongue (do not inhale). Ask woman to close her mouth after spray administered.

Repeat after 5 minutes if hypertonus sustained.

Cautions:

  • Nitrates may increase intraocular pressure and so should be used with caution in glaucoma.

Contraindications:

  • Uncorrected hypovolaemia
  • Severe anaemia (Hb<60 g/L)
  • Increased intracranial pressure
  • Constrictive pericarditis / pericardial tamponade
  • Hypersensitivity to GTN. Nitrates, coconut oil, ethanol, glycerol monocaprylocaproate, peppermint oil

Side-effects:

Due to vasodilating effects –

Headache
Hypotension
Reflex tachycardia or bradycardia 
Rarely nausea, vomiting,flushing

(For complete list cautions,contraindications and side-effects see BNF)

Haemodynamic monitoring, a rapidly running I.V. infusion and immediately available ephedrine and phenylephidrine are mandatory prior to the use of Nitroglycerin (Glyceryl Trinitrate).

Once the third stage is complete, a Syntocinon infusion should be commenced. 

 

References

Smith GN & Brien JF. Use of nitroglycerin for uterine relaxation. Obstet Gynecol Survey 1998; 53:9:559-65.

Oxford Handbook Anaesthesia 2016

Last reviewed: 24 November 2021

Next review: 29 November 2026

Author(s): Dr Julie Murphy

Version: 4

Approved By: Dr Catrina Bain, Clinical Director, Obstetrics GGC; Obstetric Guideline Group

Document Id: 492