Previous studies have demonstrated that an experienced ultrasound operator is able to efficiently perform radial arterial puncture on patients where an initial operator failed to puncture arteries via simple palpation.

The objective of this study is to compare "difficult-to-puncture" patients randomized into two groups: one group where ultrasound is used to aid artery localisation, and one group where only palpation is used.

test

Inclusion Criteria:

• The patient must have given his/her informed and signed consent
• The patient must be insured or beneficiary of a health insurance plan
• The patient's health status necessitates an arterial blood sample AND his/her radial arteries are deemed unpalpable OR two previous attempts at radial arterial puncture by a nurse resulted in failure

Exclusion Criteria:

• The patient is participating in another study
• The patient is in an exclusion period determined by a previous study
• The patient is under judicial protection, or any kind of guardianship
• The patient refuses to sign the consent
• It is impossible to correctly inform the patient
• The patient is pregnant, parturient, or breastfeeding
• Arterial puncture is required on femoral, humeral or axillary arteries
• The patient is in cardiac arrest
• The patient has known circulatory problems, ischemia, local infection
• The patient has a severe bleeding or hemostasis disorder (hemophilia, hypoprothrombinemia, platelets <50,000)
• The patient is an upper limb amputee, or his/her arm is in a cast
• The patient has known allergies to methyl or propylbenzoate, propylene glycol or chlorexhidine gluconate