Hypertension is a major problem that leads to complications in patients' blood vessels, kidneys, heart, brain, and eyes (Saito & Hasebe, 2021; Whelton et al., 2018). The condition affects approximately 1.39 billion people worldwide (Mills et al., 2020). It is the most common cause of hospital admissions and ranks first among the causes of death in the world (Victor, 2020). It is also a risk factor for stroke, myocardial infarction, heart failure, peripheral vascular disease, aortic dissection, atrial fibrillation, end-stage renal failure, and dementia (Sorato et al., 2021; Victor, 2020). Certain complications, such as an intracranial hemorrhage and encephalopathy, may occur if the condition is accompanied by headaches, which is one of the significant symptoms of hypertension (Arca & Singh, 2019). It has been emphasized in the literature that untreated or inadequately treated hypertension-related complications create a great burden on the health system (Lip et al., 2017). Delaying the treatment of hypertension causes significant damage to the brain, heart, kidneys, blood vessels, and eyes. Therefore, it is vital that patients' blood pressure be reduced as soon as possible (Saito & Hasebe, 2021; Sorato et al., 2021). For some hypertensive individuals, failure to start treatment immediately may have fatal consequences (Saito & Hasebe, 2021). It has been reported that a 10 mmHg decrease in systolic blood pressure (SBP) reduces the risk of cardiovascular disease by 20% and mortality by 10–15% (Whelton et al., 2018), while a 20 mmHg decrease in SBP has been found to reduce the risk of cardiovascular disease by 50% (Unger et al., 2020).

Lifestyle adjustments and drug therapies are used for the treatment of hypertension (Van Truong et al., 2021), and nonpharmacological methods are employed to improve the effect of the standard treatment (Lattanzio & Weir, 2020). One such method is cold application, which is an independent nursing intervention (Amaniyan et al., 2020). It has been stated that cold application is a simple, easy, and low-cost approach to lowering blood pressure that does not have any side effects (Mooventhan, 2016). The effects of cold application on the cardiovascular system include a decrease in nerve conduction velocity (Premkumar, 2004), suppression of sympathetic activity (Michael et al., 2019; Mooventhan et al., 2021), vagal stimulation (Capilupi et al., 2020), vasoconstriction (Mugele et al., 2021), and vasodilation (Hall & Guyton, 2011).

The trapezius, splenius capitis, and semispinalis capitis muscles are located in the back of the neck (Vasilios, 2014). In addition, branches from many nerves, such as the vagus nerve, glossopharyngeal nerve, and facial nerve, reach the back of the neck (Hombach-Klonisch et al., 2019). The acupuncture points DU14 (Dazhui), DU15 (Yamen), DU16 (Fengfu), GB20 (Fengchi), and UB10 (Tianzhu) are also located in the back of the neck (Lee, 2016; Stux, 2007).

Certain studies show that cold application and an ice massage to the head and spine reduce blood pressure in healthy individuals and hypertensive patients (Mooventhan, 2016; Mooventhan et al., 2021). Cold application between the vertebrae has been found to reduce blood pressure in patients with hypertension (Michael et al., 2019). In the literature, no studies have evaluated the effect of cold application to the back of the neck on blood pressure. Considering the anatomical structure of the neck and the physiological effects of cold application, this study was planned based on the assumption that cold application to the neck could produce cardiovascular effects. The aim of this study was to analyze the effect of cold application to the back of the neck on blood pressure in hypertensive patients admitted to the emergency department.

The hypothesis of this study is: Applying cold to the back of the neck lowers blood pressure in hypertensive patients.