, Introduction
Patients with end-stage kidney disease (ESKD) often experience acute complications during hemodialysis (HD), including intradialytic hypotension, muscle cramps, nausea, vomiting, headache, chest pain, itching, vascular access hemorrhage, disequilibrium syndrome, dialyzer reaction, hemolysis, air embolism, and cardiac arrhythmias [1]. Intradialytic hypotension, cramps, nausea, vomiting, and headache occur frequently, which can be debilitating and are associated with poor long-term outcomes. However, some acute complications, such as air embolism, hemolysis, vascular access hemorrhage, venous needle dislodgement, dialysis disequilibrium, and major allergic reactions, rarely occur nowadays because of advances in the safety features of modern HD machines, meticulous treatment and testing of dialysates, adherence to strict safety protocols, and extensive training of dialysis staff to handle medical emergencies [2].
HD unit-based cardiac arrest is the most feared complication of HD and a major concern for patients with ESKD as well as healthcare providers. Even though the incidence of cardiac arrest in dialysis units is only 4.6 to 80 per 100,000 HD sessions, 60% of these patients die within 48 hours of cardiac arrest, and 13% die during dialysis [3–6].
Many countries require that dialysis units be equipped with emergency equipment. In the United States, the Centers for Medicare and Medicaid Services (CMS) issued recommendations for emergency preparedness for providers and suppliers participating in Medicare and Medicaid Final Rules to establish uniform emergency preparedness guidelines for healthcare providers participating in Medicare and Medicaid [7]. The dialysis emergency equipment section of the CMS requires dialysis facilities to have equipment on the premises to assist patients in an emergency, including oxygen, airways, suction, defibrillators or automated external defibrillators, resuscitators, and emergency medications, and to be available for use in the event of an emergency. According to the Hong Kong Renal Dialysis Unit Certification, emergency equipment and supplies include oxygen cylinders, Ambu bags and oxygen masks, oximeters, suction equipment, electrocardiograph (ECG) and ECG monitors, and defibrillators [8]. Guidelines for institutions providing dialysis in Singapore state that emergency equipment, including cardiac monitoring devices with defibrillators, Air-Viva (Yeap Medical Supplies) or respirators, intubation equipment, and oxygen supplies, should always be available in dialysis centers [9]. This means that in many countries, dialysis facilities are required to have oxygen cylinders, suction equipment, intubation sets, ECG, and defibrillators as standard equipment.
In Korea, the provision of emergency equipment in the dialysis unit is not yet mandatory. However, the availability of emergency equipment is included as an evaluation criterion in the HD quality assessment conducted by the Health Insurance Review and Assessment Service (HIRA) [10]. HIRA also suggests that dialysis facilities should have similar categories of emergency equipment as mentioned above. However, no studies have investigated whether the availability of emergency equipment in HD facilities improves patient outcomes. In this study, we aimed to evaluate the impact of preparedness of emergency equipment on mortality in Korean patients undergoing maintenance HD.
Methods
Data source and study population
This study was approved by the Institutional Review Board of the Kangnam Sacred Heart Hospital, Hallym University (approval no. 2021-11-043). Owing to the retrospective nature of the study, the requirement for informed consent was waived.
This study was conducted on patients undergoing maintenance HD who were already on dialysis for ESKD. Demographic and clinical data were retrieved from the HD quality assessment data collected in 2015. HD quality assessment was conducted at facilities with HD equipment and HIRA bills for HD on a biennial basis. For HD quality assessment, patients aged 18 years or older who received HD treatment at least twice a week as outpatients at each dialysis facility were enrolled. Patients who received a kidney transplant before the index date were excluded from the analysis (Fig. 1).
HD quality assessment requires data on dialysis facilities, and data from each dialysis facility were collected using a web-based data collection system [10]. The collected data included 12 measures in three domains (structure, process, and outcome) (Supplementary Table 1, available online). Structural information, including information on medical staff (doctors and nurses), number of HD treatments, number of HD equipment (including isolated HD equipment), number of emergency equipment, and status of water quality testing, was entered into the collection system for each dialysis facility. Patient factors related to the procedures (frequency of monitoring vascular access for stenosis and routine laboratory tests) and the outcomes (frequency of satisfaction with HD adequacy and calcium and phosphorus control) were also analyzed. Data retrieved from web-based databases were compared to those from electronic medical records to ensure accuracy and reliability. Demographic data, including information on age, sex, duration of dialysis, comorbidities, and survival status, were collected. Predialysis body mass index (BMI), as well as systemic and diastolic blood pressure levels, were also measured and reported. Laboratory assessments included analysis of plasma hemoglobin, serum albumin, phosphorus, and total calcium levels.
HD facility star rating system provides useful information regarding HD facilities to patients in a recognizable format in Korea [10]. The five-star rating was determined based on the sum of weighted scores from 12 measures of HD quality. A total score summed up to 100 and the star rating ranged from one-star to five-star based on the absolute sum of weighted scores: one-star, <65; two-star, 65 to 75; three-star, 75 to 85; four-star, 85 to 95; and five-star, ≥95.
Comorbidities in eligible patients were identified using ICD-10 (International Classification of Diseases, 10th Revision) codes based on information obtained from the health insurance claims database of the HIRA between January and December 2015 [11,12]. Comorbidities, including diabetes mellitus, hypertension, heart failure, cerebrovascular disease, ischemic heart disease, and atrial fibrillation, were assessed.
The HD quality assessment tool includes 12 quality measures in three domains including structural, procedural, and outcome (Supplementary Table 1, available online). The five-star rating was determined based on the sum of weighted scores from 12 measures of HD quality (Supplementary Table 2, available online). A total score summed up to 100. The weight was applied from 0.5 to 2.0 based on the importance of the measures. The star rating ranged from one-star to five-star based on the absolute sum of weighted scores: one-star, <65; two-star, 65 to 75; three-star, 75 to 85; four-star, 85 to 95; and five-star, ≥95.
Emergency equipment preparedness and outcomes
The HD quality assessment recommendations included guidelines on emergency equipment and supplies, such as oxygen cylinders, suction equipment, intubation sets, ECG, and defibrillators. Each equipment is defined as follows; oxygen cylinder is a device that stores oxygen and can be supplied to a patient through an oxygen mask or nasal tube. Suction equipment is medical equipment that removes fluids or mucous from a patient’s airway or body, and intubation set includes the airway, laryngoscope, endotracheal tube, Ambu bag, and stylets. ECG and defibrillator are based on commercially available equipment. We assessed the presence or absence of each emergency equipment and defined facilities that had all of the following: oxygen cylinders, suction equipment, intubation sets, ECGs, and defibrillators as emergency equipped facilities, and facilities that did not have any of these as no emergency equipment facilities. The primary endpoint was all-cause mortality based on the readiness of emergency equipment. Patients who received kidney transplants during the follow-up period were censored at the time of kidney transplantation. The mortality data were collected between January 2016 and November 2021.
Statistical analyses
Patients were divided into two groups based on the presence or the absence of emergency equipment. Baseline characteristics were compared using the chi-square test for categorical variables and the independent t test for continuous variables. Continuous variables are expressed as means with standard deviations, and categorical variables are expressed as frequencies and percentages. Kaplan-Meier analysis and the log-rank test were performed to compare the risks of death of patients in different groups. Multivariate-adjusted Cox proportional hazards models were used to determine whether the readiness of emergency equipment was an independent predictor of mortality. Model 1 was adjusted for age, male sex, dialysis vintage, and BMI. Model 2 was adjusted for medical comorbidities (diabetes mellitus, hypertension, ischemic heart disease, heart failure, cerebrovascular accident, and atrial fibrillation) and factors included in model 1. Model 3 was adjusted for all demographic and clinical parameters (levels of plasma hemoglobin, serum albumin, calcium, phosphorus, and single-pool Kt/V). Finally, subgroup analyses were performed to determine the relative risk of death according to the readiness of emergency equipment. Subgroup analyses were performed according to age group (<65 years vs. ≥65 years), sex, dialysis duration (<5 years vs. ≥5 years), comorbidities, as well as levels of serum hemoglobin (<10.0 g/dL vs. ≥10.0 g/dL) and albumin (<3.5 g/dL vs. ≥3.5 g/dL). All statistical analyses were performed using R version 4.0.2 (R Foundation for Statistical Computing). Standardized mean differences were calculated, and statistical significance was set at p < 0.05.
Results
Baseline characteristics of the patients
In this study, 34,950 patients treated at 798 facilities were included (Table 1). The average age of the patients was 60.2 ± 12.8 years, of which 20,543 (58.8%) were male. The average dialysis vintage, BMI, as well as pre-HD systolic and diastolic blood pressure values, were 5.6 ± 5.1 years, 22.4 ± 3.4 kg/m2, as well as 141.2 ± 15.6 and 77.6 ± 9.6 mmHg, respectively. Hypertension (84.9%) and diabetes mellitus (61.5%) were the two most common comorbidities, followed by ischemic heart disease (34.6%), heart failure (14.7%), cerebrovascular disease (8.9%), and atrial fibrillation (5.3%).
The baseline characteristics of the patients according to the preparedness of emergency equipment are shown in Table 1. In total, 33,267 patients (95.2%) were included in the group with emergency equipment, and 1,683 patients (4.8%) were included in the group without emergency equipment. Patients in the group with emergency equipment had lower levels of serum calcium and phosphorus, as well as lower systolic and diastolic blood pressure values, than those in the group without emergency equipment. Single-pool Kt/V was higher in the group with emergency equipment than in the group without emergency equipment.
In the group without emergency equipment, patients were most commonly at a dialysis facility without defibrillators (62.9%), followed by suction equipment (39.0%), intubation sets (28.4%), ECG (19.5%), and oxygen cylinders (8.3%) (Table 1).
In the readiness of emergency equipment, facilities without defibrillators (93.5%) were the most common, followed by those without suction equipment (96.7%), as well as intubation sets and ECG (97.4%). Oxygen cylinders were provided in 99.4% of all facilities. Among medical care facilities, nursing hospitals had the lowest readiness for emergency equipment, whereas tertiary hospitals were fully equipped with all emergency equipment (Supplementary Table 2, available online).
Crude rate of all-cause mortality
During the follow-up period of 53.7 ± 23.0 months, a total of 12,507 deaths (35.4%) occurred. The crude mortality rate was 79.9 per 1,000 person-years (Table 2). The group with emergency equipment had a lower crude mortality rate than the group without emergency equipment (79.2 per 1,000 person-years vs. 95.3 per 1,000 person-years, respectively; p < 0.001). Kaplan-Meier survival curves showed that the group with emergency equipment had a lower risk of death than the group without emergency equipment (Fig. 2).
Preparedness of emergency equipment independently decreased the risk of mortality
Cox proportional hazard models were used to identify risk factors associated with patient mortality (Table 3). In the univariate analysis, old age; male sex; dialysis vintage; low BMI; presence of comorbidities (diabetes mellitus, hypertension, ischemic heart disease, heart failure, cerebrovascular accident, and atrial fibrillation); low levels of plasma hemoglobin, serum albumin, calcium, and phosphorus; as well as low single-pool Kt/V, were associated with the risk of death (Supplementary Table 3, available online). In addition, the group with emergency equipment had a low mortality rate (hazard ratio [HR], 0.83; 95% confidence interval [CI], 0.77–0.89; p < 0.001). Even after adjustment for age, sex, dialysis vintage, and BMI (model 1), the group with emergency equipment remained an independent predictor of patient mortality (HR, 0.84; 95% CI, 0.78–0.91; p < 0.001). With adjustment for comorbidities in addition to the factors included in model 1 (model 2), the group with emergency equipment remained an independent risk factor for patient mortality (HR, 0.83; 95% CI, 0.77–0.90; p < 0.001). After adjustment for demographic and clinical factors that were significantly associated with mortality in the univariate analysis (model 3), the group with emergency equipment remained an independent risk factor for patient mortality (HR, 0.87; 95% CI, 0.79–0.96; p = 0.004). Finally, after adjustment for factor of Medicaid in model 3 (model 4), the group with emergency equipment remained an independent risk factor for patient mortality (HR, 0.88; 95% CI, 0.80–0.96; p = 0.006).
Subgroup analysis for all-cause mortality
The group with emergency equipment had higher patient survival rates than the group without emergency equipment in all subgroups, except for the subgroups of patients without diabetes mellitus, congestive heart failure, cerebrovascular accident, and hypoalbuminemia (Fig. 3).
Discussion
In this study, we found that patients treated in HD units with emergency equipment had better survival rates, lower levels of serum calcium and phosphorus, as well as better blood pressure control, compared to those treated in HD units without emergency equipment. Dialysis adequacy was significantly higher in the group with emergency equipment than in the group without emergency equipment.
Patients undergoing HD have a high burden of cardiovascular disease and a particularly high risk of sudden cardiac death. Cardiac arrest accounts for one-quarter of the deaths in patients undergoing HD in the United States [13]. According to data from the Dialysis Outcomes and Practice Patterns Study, sudden cardiac death in patients undergoing HD is more common in the United States (33% of all deaths) than in other countries, including Italy (23%), Japan (23%), and France (22%) [14]. Sudden cardiac arrest is most commonly caused by hemodynamic collapse owing to ventricular tachyarrhythmia, which usually occurs in patients with coronary heart disease [15]. In addition to coronary heart disease, reduced tolerance to myocardial ischemia, rapid changes in electrolyte levels, and autonomic dysfunction can cause sudden cardiac death [4]. Hypertension, anemia, fluid overload, and vascular calcification, which are common in patients with ESKD, have also been reported to cause heart failure [4].
In previous reports, the incidence of cardiopulmonary arrest during HD has been shown to vary from 4.6 to 80 cases per 100,000 HD sessions [3–6]. Although patients who undergo HD are generally old and have many comorbidities, the incidence of cardiopulmonary arrest is relatively low, which may be related to the fact that the safety of HD has been improved over time [4]. Patients undergoing HD are at a high risk of cardiovascular complications and require special attention as sudden changes can occur, leading to sudden cardiac arrest. While administering HD, the medical staff must carefully observe the patients, ensuring an appropriate monitoring system is in place to prevent cardiac arrest in the HD unit [4].
The U.S. CMS requires medical staff to ensure that emergency equipment necessary for cardiopulmonary resuscitation (CPR), such as oxygen, airways, suction, defibrillators or automated external defibrillators, artificial resuscitators, and emergency medications, is readily available at all times [7]. Although CPR initiated by the staff administering dialysis has been reported to be associated with significantly increased survival rates [16], it is unclear whether the presence of emergency equipment in the dialysis unit reduces patient mortality. In a previous study, Lehrich et al. [17] reported no difference in patient outcomes based on the presence of an automated external defibrillator in the dialysis facility in a study using the U.S. Event Reporting Management System database. This study evaluated the availability of five emergency equipment: oxygen cylinders, suction equipment, intubation sets, ECG, and defibrillators. So this study is significant because it analyzed the prognosis of patients according to the availability of five emergency equipment. In this study, 91.4% of the dialysis units included were fully equipped with emergency equipment, and the percentage of fully equipped dialysis units is steadily increasing [18]. The availability of emergency equipment was an independent predictor of survival in patients undergoing maintenance HD, as it led to reduced mortality by 12%, even after adjustment for demographic and clinical parameters. A well-equipped HD unit can help with the immediate administration of CPR in the event of cardiac arrest. Improvement in control of blood pressure, calcium, and phosphorus levels may also be associated with reduced mortality.
This study has several limitations. First, the actual use of emergency equipment in the HD units was not examined. Second, we did not analyze mortality based on the cause of death or disease. Third, the small number of facilities without emergency equipment in this study requires caution in interpreting the results. Finally, the cost-effectiveness of emergency equipment was not considered. Therefore, further research is required to determine whether emergency equipment is cost-effective.
In conclusion, the preparedness of emergency equipment was associated with a low risk of death in patients undergoing maintenance HD. Patients undergoing HD can experience life-threatening complications such as cardiac arrest during dialysis. A well-equipped HD unit can help provide immediate CPR in the event of cardiac arrest to increase patient survival.
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