Cannulation Complications and Clinical Negligence: A Medico-Legal Case Study

Cannulation is one of the most routine interventions carried out in acute hospital settings. For clinicians, it is often performed quickly, pragmatically, and with limited fanfare. For patients, however, complications, even relatively minor ones, can be distressing, uncomfortable, and frightening. When concerns arise after discharge, the line between an unfortunate complication and an actionable clinical negligence claim can become blurred.

This case study illustrates how the courts, and medical expert witnesses, approach cannula-related allegations in practice. It also highlights a recurring theme in clinical negligence litigation: the law does not require perfection, but it does require reasonable care judged against real-world standards.

Background to the case

The patient presented to Accident and Emergency with symptoms of a urinary tract infection, dehydration, and ongoing vomiting. She was clinically unwell and required intravenous fluids and antibiotics. A peripheral cannula was inserted into the antecubital fossa (ACF) to facilitate treatment.

Following a short admission and subsequent discharge, the patient developed discomfort in the arm where the cannula had been sited. Imaging identified a small thrombus, and anticoagulation therapy was commenced. While the thrombus resolved, the patient later brought a claim alleging negligent cannula placement and inadequate post-procedure care.

Specifically, it was alleged that:

• The antecubital fossa was an inappropriate site for cannulation

• No proper cannula assessment or monitoring had taken place

• Documentation of the insertion and ongoing care was inadequate

An experienced cannula placement expert witness was instructed to provide an opinion on breach of duty and causation.

The clinical negligence framework

As with all claims of this nature, the assessment of liability centred on well-established legal principles.

Under Bolam v Friern Hospital Management Committee [1957], a clinician will not be negligent if their actions accord with a responsible body of medical or nursing opinion. Bolitho v City and Hackney Health Authority [1998] adds that such opinion must also withstand logical scrutiny.

In other words, the question was not whether the cannula could have been sited elsewhere, or whether documentation could have been better, but whether the care provided fell below a reasonable standard when judged against everyday clinical practice.

Site selection: what actually happens in A&E

One of the central allegations was that the antecubital fossa should not have been used and that a distal site, such as the hand or wrist, ought to have been preferred.

The expert witness strongly rejected this criticism.

Drawing on over 30 years of frontline nursing experience, the expert explained that the ACF is one of the most commonly used cannulation sites, particularly in acutely unwell or dehydrated patients. In such circumstances, veins in the hand or wrist are often collapsed, fragile, or difficult to access, leading to repeated attempts and increased patient discomfort.

In contrast, veins in the antecubital fossa are frequently:

• More visible and palpable

• Easier to cannulate successfully on first attempt

• Less painful for the patient

• More reliable for rapid fluid administration

The suggestion that the ACF should be avoided except in extreme emergencies was described as "detached from the realities of clinical practice", particularly in a busy emergency department environment.

Crucially, there was no evidence that the choice of site caused or materially contributed to the development of the thrombus.

Cannula-related complications and causation

Cannula-associated thrombosis, phlebitis, and discomfort are recognised complications, even when cannulation is performed competently. The expert emphasised that the occurrence of a complication does not, in itself, imply negligence.

In this case, the thrombus was small, promptly identified, and appropriately treated. There was no evidence of infection, extravasation, or prolonged cannula dwell time. Nor was there evidence that an alternative cannulation site would have avoided the outcome.

From a legal perspective, this distinction is critical. Even where a technical breach of duty can be identified, a claimant must still establish causation - that the breach caused the injury complained of. On the evidence available, that link could not be made.

Documentation: imperfect, but not negligent

The second strand of the claim related to documentation. It was accepted that the initial A&E cannula insertion was not formally recorded in the contemporaneous notes.

The expert acknowledged that this was suboptimal. Best practice would ordinarily include a record of cannula insertion, noting the site and time. However, the absence of a note did not equate to negligent care, nor did it result in harm.

Importantly:

• The cannula was subsequently identified and recorded by the admitting ward via electronic systems

• Ongoing ward-based observations noted no concerns with the cannula site

• There was no evidence that the lack of an A&E insertion note affected monitoring, escalation, or decision-making

As the expert succinctly explained:

"It is not standard practice to document the rationale for vein selection. We do not note why we chose the ACF over the hand unless there is an incident - and there wasn’t. This is normal, reasonable practice.”

This evidence aligned squarely with Bolam principles, reflecting what actually happens in busy clinical settings rather than what might appear ideal in hindsight.

Cannula monitoring and post-discharge advice

The claimant also alleged inadequate monitoring and poor post-discharge advice.

In reality, the evidence demonstrated that the cannula site was observed during the inpatient stay and found to be unproblematic, no adverse signs requiring escalation or removal were documented, on discharge the patient was advised to use a cold compress and monitor symptoms, and she sought further medical attention the following morning, which was appropriate and timely.

From both a clinical and legal standpoint, this sequence of events was entirely reasonable. The advice given was proportionate to the symptoms observed at the time, and the patient acted sensibly when discomfort persisted.

What an expert expects to see in cannulation cases

The expert outlined what a nursing expert would typically expect when assessing cannula-related allegations, including:

• A record of cannula insertion where practicable, noting site and time

• Use of relevant monitoring tools

• Site selection based on vein quality, patient condition, and clinical urgency

• Escalation or removal only where symptoms or adverse signs indicate

• Clear, practical discharge advice aligned with the patient’s presentation

While the absence of an A&E insertion note fell short of best practice, the overall care pathway met these expectations.

Common practice, not hindsight criticism

Ultimately, the expert concluded that the care provided was clinically defensible. The choice of cannulation site was logical and widely accepted in practice. The complication, while unfortunate, was not caused by negligent care. The documentation lapse, though acknowledged, was not causative.

The case was therefore consistent with both Bolam and Bolitho standards, and the claim could not be sustained.

Why this matters

Cannula-related claims are increasingly common, often driven by patient discomfort rather than clear evidence of substandard care. This case serves as a reminder that the courts assess clinicians against reasonable, real-world practice - not retrospective ideals.

For healthcare providers, it reinforces the importance of good documentation where possible, without losing sight of clinical realities. For claimants and their advisors, it underlines the need for robust expert evidence on both breach and causation.

And for those instructing or defending claims of this nature, early input from experienced medico-legal experts, particularly those with genuine frontline experience, can be decisive in identifying whether a case is truly viable.