Why can't intravenous (IV) diphenhydramine be administered during a sickle cell crisis?

From the Guidelines

Intravenous (IV) diphenhydramine should not be administered during a sickle cell crisis due to its potential to worsen the crisis by causing dehydration and respiratory depression, among other complications. The management of sickle cell disease, as outlined in the guidelines from the Association of Anaesthetists 1, emphasizes the importance of meticulous peri-operative care, including avoiding dehydration and maintaining adequate oxygenation. Diphenhydramine, with its anticholinergic properties, can lead to dehydration, which increases blood viscosity and can exacerbate the sickling of red blood cells. Furthermore, its potential to cause respiratory depression could reduce oxygen levels, triggering further sickling. Additionally, diphenhydramine may mask important symptoms that healthcare providers need to monitor during a crisis.

Key Considerations in Sickle Cell Crisis Management

• Adequate hydration is crucial to prevent dehydration, which can worsen the crisis.
• Oxygen therapy should be considered if necessary to maintain adequate oxygen levels.
• Appropriate pain management, using medications like NSAIDs and opioids, is essential.
• Consultation with a hematologist is recommended when managing medications for patients with sickle cell disease, especially during an acute crisis.

Alternatives to IV Diphenhydramine

If an antihistamine is absolutely necessary during a sickle cell crisis, non-sedating alternatives with fewer anticholinergic effects should be considered. The primary focus should remain on the core principles of sickle cell crisis management, as supported by the most recent and highest quality studies 1.

Importance of Recent and High-Quality Evidence

The guidelines from the Association of Anaesthetists 1 provide a comprehensive approach to the peri-operative management of patients with sickle cell disease, highlighting the need for careful planning, assessment of comorbidities, and multidisciplinary team working to mitigate complications. These guidelines, being the most recent and of high quality, prioritize the management strategies that focus on reducing morbidity, mortality, and improving the quality of life for patients with sickle cell disease.

From the Research

Administration of Intravenous Diphenhydramine

• The use of intravenous (IV) diphenhydramine in patients with sickle cell vaso-occlusive crisis is associated with a higher incidence of oversedation compared to oral diphenhydramine therapy 2.
• A retrospective study found that 29% of patients in the IV diphenhydramine group experienced oversedation, compared to 13% in the oral diphenhydramine group 2.
• The study also found that patients who received IV diphenhydramine had more frequent admissions and a longer length of stay compared to those who received oral diphenhydramine 2.

Considerations for Administration

• Clinicians may consider oral diphenhydramine preferentially in appropriate patients over IV administration due to the potential risks associated with IV diphenhydramine 2.
• The decision to administer IV diphenhydramine should be made on a case-by-case basis, taking into account the individual patient's needs and medical history.
• There is no direct evidence to suggest that IV diphenhydramine cannot be administered during a sickle cell crisis, but the potential risks and benefits should be carefully considered 2.

Lack of Direct Evidence

• There is limited research directly addressing the administration of IV diphenhydramine during a sickle cell crisis, and more studies are needed to fully understand its effects 3, 4, 5, 6.