Green or Pink? A Comparison of Pain and Procedural Difficulty With Intravenous Cannulas in the Emergency Department

A Comparison of 18-Gauge and 20-Gauge Intravenous Cannulas in Terms of Pain and Procedural Difficulty: A Randomized Controlled Trial in the Emergency Department

Peripheral intravenous catheter (PIVC) insertion is one of the most frequently performed invasive procedures in both medical and nursing practice. It is essential for blood sampling, intravenous (IV) fluid resuscitation, medication administration, blood product transfusion, and IV contrast-enhanced radiological imaging. In emergency department (ED) settings, where patients may deteriorate rapidly, timely and adequate IV access is of critical importance. Larger-bore cannulas allow faster fluid and contrast delivery and are less prone to occlusion; however, Larger-bore cannulas are often perceived to cause greater pain and procedural difficulty compared to smaller-bore cannulas. This perception may lead clinicians to prefer smaller cannulas, potentially compromising care quality in patients who may unexpectedly deteriorate.

Cannula insertion inherently causes discomfort, pain, and anxiety for patients, and multiple failed attempts further amplify these effects. Patient satisfaction, an important dimension of overall care quality, is directly influenced by pain experience and the number of insertion attempts. Patients requiring two or more attempts for successful cannulation are generally classified as having difficult intravenous access (DIVA). Repeated failed attempts are associated with vascular injury, increased patient distress, delays in diagnosis and treatment, and greater consumption of healthcare resources. The A-DIVA score, developed by Van Loon et al., enables risk stratification for IV access difficulty at triage, classifying patients as low, moderate, or high risk, and facilitating proactive measures such as ultrasound guidance or involvement of experienced personnel for high-risk patients.

This single-center, prospective, single-blind, randomized controlled trial aims to compare 18-gauge (18G) and 20-gauge (20G) PIVCs in terms of patient-reported pain intensity and nurse-reported procedural difficulty in adult ED patients with low-to-moderate A-DIVA risk. The investigators hypothesize that 18G cannulas cause similar pain and procedural difficulty compared to 20G cannulas in this patient population.

The study will be conducted at Marmara University Pendik Training and Research Hospital Emergency Department. Ethics approval has been granted by the Marmara University Faculty of Medicine Clinical Research Ethics Committee. Adult patients (18 years and older) requiring IV access for diagnostic or therapeutic purposes and classified as low or moderate A-DIVA risk will be eligible. Patients with cognitive impairment, altered mental status, or hemodynamic instability (systolic BP less than 90 mmHg or mean arterial pressure less than 65 mmHg) will be excluded.

Eligible consenting patients will be randomized 1:1 using a block randomization method (block size of 4) to either 18G or 20G cannula insertion. Cannula assignment will be delivered to nurses in sealed envelopes. Patients will be blinded to cannula size using blackout goggles. Cannulation will be performed by ED nurses following standard antiseptic and securement procedures, targeting the dorsum of the hand, forearm, or antecubital fossa. If the first attempt fails, at least one additional attempt with the assigned cannula will be required before allowing free choice of cannula and site.

The primary outcomes are patient-reported pain intensity and nurse-reported procedural difficulty, each assessed using a 10 cm Visual Analog Scale (VAS) immediately after the first cannulation attempt and compared between the 18G and 20G cannula groups. Secondary outcomes include the comparison of first-attempt cannulation success rate between the 18G and 20G cannula groups. This comparison will also be performed separately according to cannulation site, operator experience, A-DIVA risk category, patient age, and patient sex.

A total of 204 patients (102 per group) will be enrolled, based on 90% power, 5% type I error, a minimum clinically important difference of 13 mm on the VAS, and a 10% dropout allowance.

Study Overview

• Status: Not yet recruiting
• Conditions: Pain; Veins; Emergency Department Patient; Peripheral Catheterization; Procedural Difficulty
• Intervention / Treatment: Device: 18-gauge peripheral intravenous cannula; Device: 20-gauge peripheral intravenous cannula

• Study Type: Interventional
• Enrollment (Estimated): 204
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Erhan Altunbas; Phone Number: +90 0506 483 29 69; Email: erhnaltnbs@gmail.com
• Study Contact Backup: Name: Emir Unal; Phone Number: +90 0532 776 60 10; Email: emirunal@gmail.com

Study Locations

• Turkey (Türkiye)
  • Istanbul, Turkey (Türkiye)
    • Marmara University Pendik Training and Research Hospital
    • Contact: Erhan Altunbas; Phone Number: +90 0506 483 29 69; Email: erhnaltnbs@gmail.com
    • Contact: Emir Unal; Phone Number: +90 0532 776 60 10; Email: emirunal@gmail.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• 18 years of age or older
• Requiring intravenous access for diagnostic or therapeutic purposes
• Classified as low or moderate risk according to the A-DIVA (Adult Difficult Intravenous Access) score
• Provision of informed consent by the patient, a relative, or a legal guardian

Exclusion Criteria:

• Inability to effectively communicate pain intensity due to cognitive impairment, altered mental status, or visual or language difficulties
• Hemodynamic instability defined as systolic blood pressure less than 90 mmHg or mean arterial pressure less than 65 mmHg

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: 18G Cannula Group; Participants in this arm will undergo peripheral intravenous cannulation using an 18-gauge (18G, green) cannula. Cannulation will be performed by emergency department nurses targeting the dorsum of the hand, forearm, or antecubital fossa following standard antiseptic and securement procedures. If the first attempt fails, at least one additional attempt with the assigned 18G cannula will be made before allowing free choice of cannula and site.	Device: 18-gauge peripheral intravenous cannula; Peripheral intravenous cannulation performed using an 18-gauge (18G, green) cannula inserted into the dorsum of the hand, forearm, or antecubital fossa by an emergency department nurse following standard antiseptic and securement procedures. No local anesthetic agents will be used. Patients will be blinded to cannula size using blackout goggles.
Active Comparator: 20G Cannula Group; Participants in this arm will undergo peripheral intravenous cannulation using a 20-gauge (20G, pink) cannula. Cannulation will be performed by emergency department nurses targeting the dorsum of the hand, forearm, or antecubital fossa following standard antiseptic and securement procedures. If the first attempt fails, at least one additional attempt with the assigned 20G cannula will be made before allowing free choice of cannula and site.	Device: 20-gauge peripheral intravenous cannula; Peripheral intravenous cannulation performed using a 20-gauge (20G, pink) cannula inserted into the dorsum of the hand, forearm, or antecubital fossa by an emergency department nurse following standard antiseptic and securement procedures. No local anesthetic agents will be used. Patients will be blinded to cannula size using blackout goggles.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pain intensity	Patient-reported pain intensity assessed using a 10 cm Visual Analog Scale (VAS) after the first cannulation attempt, compared between the 18G and 20G cannula groups. The VAS score ranges from 0 (no pain) to 10 (worst imaginable pain). The unit of measure is the score on the Visual Analog Scale (0-10 cm).	Immediately after the first cannulation attempt
Procedural difficulty	Nurse-reported procedural difficulty assessed using a 10 cm Visual Analog Scale (VAS) after the first cannulation attempt, compared between the 18G and 20G cannula groups. The VAS score ranges from 0 (no difficulty) to 10 (worst imaginable difficulty). The unit of measure is the score on the Visual Analog Scale (0-10 cm)	Immediately after the first cannulation attempt

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
First-attempt cannulation success rate	The proportion of participants with successful cannulation achieved on the first attempt, compared between the 18G and 20G cannula groups. The unit of measure is the percentage of participants (%).	Immediately after the first cannulation attempt
Comparison of first-attempt cannulation success rate by cannulation site between groups	The first-attempt cannulation success rate at each cannulation site (dorsum of hand, forearm, or antecubital fossa), assessed by procedural documentation, will be compared between the 18G and 20G cannula groups. The unit of measure is the percentage of participants with successful first-attempt cannulation per site (%).	Immediately after the first cannulation attempt
Comparison of first-attempt cannulation success rate by operator experience between groups	The first-attempt cannulation success rate across different levels of operator experience, assessed in years of clinical experience, will be compared between the 18G and 20G cannula groups. The unit of measure is the percentage of participants with successful first-attempt cannulation per operator experience level (%).	Immediately after the first cannulation attempt
Comparison of first-attempt cannulation success rate by A-DIVA score between groups	The first-attempt cannulation success rate across A-DIVA risk categories, assessed using the Adult Difficult Intravenous Access (A-DIVA) scoring tool, will be compared between the 18G and 20G cannula groups. The unit of measure is the percentage of participants with successful first-attempt cannulation per A-DIVA risk category (%). The A-DIVA score ranges from 0 to 5, with scores of 0-1 indicating low risk, 2-3 indicating moderate risk, and 4-5 indicating high risk of difficult intravenous access.	Immediately after the first cannulation attempt
Comparison of first-attempt cannulation success rate by patient age between groups	The first-attempt cannulation success rate across different age groups, recorded in years at the time of enrollment, will be compared between the 18G and 20G cannula groups. The unit of measure is the percentage of participants with successful first-attempt cannulation per age group (%).	Immediately after the first cannulation attempt
Comparison of first-attempt cannulation success rate by patient sex between groups	The first-attempt cannulation success rate by patient sex (male or female), recorded at the time of enrollment, will be compared between the 18G and 20G cannula groups. The unit of measure is the percentage of participants with successful first-attempt cannulation per sex (%).	Immediately after the first cannulation attempt

Collaborators and Investigators

• Sponsor: Marmara University Pendik Training and Research Hospital
• Investigators: Principal Investigator: Erhan Altunbas, Marmara University Scholl Of Medicine

Publications and helpful links

General Publications

• Kelly AM. The minimum clinically significant difference in visual analogue scale pain score does not differ with severity of pain. Emerg Med J. 2001 May;18(3):205-7. doi: 10.1136/emj.18.3.205.
• Hajian-Tilaki K. Sample size estimation in diagnostic test studies of biomedical informatics. J Biomed Inform. 2014 Apr;48:193-204. doi: 10.1016/j.jbi.2014.02.013. Epub 2014 Feb 26.
• Cheung E, Baerlocher MO, Asch M, Myers A. Venous access: a practical review for 2009. Can Fam Physician. 2009 May;55(5):494-6. No abstract available.
• Loon FHJV, Puijn LAPM, Houterman S, Bouwman ARA. Development of the A-DIVA Scale: A Clinical Predictive Scale to Identify Difficult Intravenous Access in Adult Patients Based on Clinical Observations. Medicine (Baltimore). 2016 Apr;95(16):e3428. doi: 10.1097/MD.0000000000003428.
• Rickard CM, Webster J, Wallis MC, Marsh N, McGrail MR, French V, Foster L, Gallagher P, Gowardman JR, Zhang L, McClymont A, Whitby M. Routine versus clinically indicated replacement of peripheral intravenous catheters: a randomised controlled equivalence trial. Lancet. 2012 Sep 22;380(9847):1066-74. doi: 10.1016/S0140-6736(12)61082-4.
• van Loon FHJ, van Hooff LWE, de Boer HD, Koopman SSHA, Buise MP, Korsten HHM, Dierick-van Daele ATM, Bouwman ARA. The Modified A-DIVA Scale as a Predictive Tool for Prospective Identification of Adult Patients at Risk of a Difficult Intravenous Access: A Multicenter Validation Study. J Clin Med. 2019 Jan 26;8(2):144. doi: 10.3390/jcm8020144.
• van Loon FH, Puijn LA, van Aarle WH, Dierick-van Daele AT, Bouwman AR. Pain upon inserting a peripheral intravenous catheter: Size does not matter. J Vasc Access. 2018 May;19(3):258-265. doi: 10.1177/1129729817747531. Epub 2018 Mar 4.
• Fields JM, Piela NE, Ku BS. Association between multiple IV attempts and perceived pain levels in the emergency department. J Vasc Access. 2014 Nov-Dec;15(6):514-8. doi: 10.5301/jva.5000282. Epub 2014 Aug 29.
• Mitra TP, Coulter-Nile S, Jegathees T, Luong J, Shetty A, Lai K. Spiced RCT: Success and Pain Associated with Intravenous Cannulation in the Emergency Department Randomized Controlled Trial. J Emerg Med. 2024 Feb;66(2):57-63. doi: 10.1016/j.jemermed.2023.10.008. Epub 2023 Oct 16.
• Rivera AM, Strauss KW, van Zundert AA, Mortier EP. Matching the peripheral intravenous catheter to the individual patient. Acta Anaesthesiol Belg. 2007;58(1):19-25.

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): August 1, 2026
• Study Completion (Estimated): August 1, 2026

Study Registration Dates

• First Submitted: May 13, 2026
• First Submitted That Met QC Criteria: June 4, 2026
• First Posted (Actual): June 5, 2026

Study Record Updates

• Last Update Posted (Actual): June 5, 2026
• Last Update Submitted That Met QC Criteria: June 4, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Neurologic Manifestations; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Pain
• Other Study ID Numbers: 09.2026.774

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No