Abstract
Background Orthostatic hypotension (OH) is prevalent in hospitalized elderly patients. It is defined as a reduction in systolic blood pressure (SBP) of at least 20 mmHg and/or diastolic blood pressure (DBP) of at least 10 mmHg within 3 minutes of standing from a lying position. This observational cohort study describes the prevalence, association with symptoms, and risk factors for OH in medical, surgical, and trauma wards in a tertiary hospital and the differences in hemodynamic behaviors between OH-positive (OHP) and OH-negative (OHN) patients.
Methods All 76 patients who were hemodynamically stable and able to stand from 4 hospital wards had noninvasive supine and orthostatic blood pressures (BPs) and pulse rates (PRs) measured over 4 days.
Results Mean age of the 76 patients included in the study was 67.8 ± 19.6 years. Overall prevalence of OH was 23.7% (95% CI: 14.7%-34.8%) with 21.2% (95% CI: 9.0%-38.9%) in medical, 31.8% (95% CI: 13.9%-54.9%) in surgical, and 19.0% (95% CI: 5.4%-41.9%) in trauma wards. OH had no association with symptoms (P = .53). We found no differences in age, number of comorbidities, and medication use between the OHN and OHP groups.
The two groups displayed very different hemodynamic responses. The OHN group demonstrated a statistically significant compensatory rise in BP and PR over time to orthostatic challenge, while the OHP group displayed the opposite effect with BP. There was no statistically significant compensatory increase in PR over time to standing in the OHP group.
Conclusions OH is common and mostly asymptomatic. Routine measurements are recommended to detect cases in the hospital setting. Our study did not identify any significant risk factors for OH but rather confirmed the previous finding that underlying impairment in autonomic responses in individuals may have instead contributed to the development of OH.
INTRODUCTION
The definition of orthostatic hypotension (OH) has not changed from its first introduction in 1996 by the American Autonomic Society. It is defined as a reduction in systolic blood pressure (SBP) of at least 20 mmHg and/or diastolic blood pressure (DBP) of at least 10 mmHg within 3 minutes of standing from a lying position.1 It is a physical sign and is not always associated with symptoms.2-4
The reported prevalence of OH ranges from 6% in healthy elderly community dwellers to 68% in hospitalized geriatric patients.5 The prevalence of OH across emergency department presentations is about 3% to 25%.6-8 OH can contribute to syncope, falls, and related injuries in elderly patients. In addition, OH has also been shown to carry significant risks for cardiovascular morbidity and mortality.9-12
Even though OH is a common medical condition among the hospitalized elderly population, the literature focuses mainly on medical and geriatric ward patients. Prevalence data for acute surgical and trauma patients are limited despite a high frequency of elderly patients in these wards with additional risk factors for OH, such as hypovolemia and prolonged postsurgery immobilization.13 Furthermore, the literature regarding risk factors (including medications) for the development of OH has been inconclusive, with various studies yielding different results.2,12,14
This descriptive observational cohort study was conducted with the primary aim to identify the spot prevalence of OH in the medical, surgical, and trauma wards of an acute tertiary hospital using routine noninvasive blood pressure (BP) monitoring methods available in the ward setting.
The secondary aims of this study were to (1) identify the association between OH and typical symptoms, defined as orthostatic dizziness, lightheadedness, presyncope, or syncope upon standing; (2) identify the underlying risk factors in OH-positive (OHP) patients; and (3) establish the differences in hemodynamic responses to orthostatic challenge between the OHP and the OH-negative (OHN) patient groups.
METHODS
This study was conducted over a period of 4 days at the Alfred Hospital in Melbourne, Australia. The Alfred Hospital is a major university teaching hospital providing a statewide adult trauma service in addition to adult general and specialist medical and surgical services.
All patients across the acute medical, surgical, trauma, and general medical wards were assessed for eligibility and recruited over 4 consecutive days. The investigators utilized the computer-generated ward list each day to ensure that no patient on these wards was left unconsidered for the study. All patients were deemed eligible for recruitment unless they met the exclusion criteria: (1) hemodynamic instability, defined as supine SBP of ≤90 mmHg and/or supine DBP of ≤50 mmHg; (2) clinical evidence of active bleeding and/or hemoglobin concentration of <90 g/L; (3) nonweightbearing status at the time of the study for any reason; (4) likelihood of remaining bedbound after discharge because of underlying medical conditions such as severe dementia or disability; and (5) refusal or noncompliance with instructions because of underlying cognitive impairment.
We obtained the hospital ethics committee's approval prior to the study and received verbal consent from each patient regarding study participation. Patients who were unable to consent were excluded from the study.
Data were collected from all patients with regard to age; sex; admitting unit and ward; duration of admission; admission diagnoses; last available hemoglobin, creatinine, and urea results; medical comorbidities; and medications administered on the day of BP measurements.
All noninvasive BP measurements were performed using automated BP machines (Philips IntelliVue MP5T and Philips SureSigns VS3, Philips Healthcare, Guildford, UK; and models from Welch Allyn, Skaneateles Falls, NY) because their use reflected routine nursing practice on the wards. Manual BP measurements were instituted on a few occasions when automated BP machines failed to record any reading. The investigators (AA and VN) conducted all measurements with the help of 3 medical students who received adequate training prior to the study.
On the day of the study, recruited patients were requested to remain in a supine position in their beds at a <30° angle for at least 5 minutes before measurement of a single supine BP. Three sets of standing BPs were further recorded at the 1st, 2nd, and 3rd minutes of standing. Supine and standing pulse rates (PRs) were also recorded. All measurements were conducted between 8:30 a.m. and 2:30 p.m. each day.
Any spontaneously reported symptoms in response to orthostatic stress were noted. If no symptom was voiced, patients were asked at the end if they experienced any typical symptoms during standing.
Statistical Analysis
All data were analyzed using SAS software version 9.2 (SAS Institute Inc., Cary, NC). Continuous data were assessed for normality and expressed as mean ± standard deviation, and categorical data were expressed as count and proportions. Ordinal data were presented as median with an interquartile range. OH prevalence was estimated and reported with 95% confidence intervals (CIs). A comparison between the groups (OHP vs OHN) was performed using student t tests, chi-square tests for equal proportions, or nonparametric tests as appropriate. Changes in SBP, DBP, and PR over time were assessed using repeated measures' analysis of variance, and results are presented as adjusted means with 95% CIs. A 2-sided P value of 0.05 was considered statistically significant.
RESULTS
A total of 119 patients in 4 wards were considered for the study. A total of 43 (36.1%) patients were excluded, and 76 (63.9%) patients were recruited for the study. Recruited patients' mean age was 67.8 ± 19.6 years. Twenty-five (58.1%) of the 43 excluded patients were unable to assume a standing position on the day of the study for various reasons, including severe pain and spinal precautions. Only 1 (2.3%) patient met the criteria for hemodynamic instability. Other reasons for exclusion were patient refusal or noncompliance (9.3%), status in the operating room or immediate postoperative period (16.3%), palliation (7.0%), discharge (2.3%), and other reasons (4.7%).
Of the 76 patients included, 18 (23.7%) met the definition for OH (95% CI: 14.7%-34.8%). The prevalence of OH was 4/21 (19.0%, 95% CI: 5.4%-41.9%) in the trauma ward, 7/22 (31.8%, 95% CI: 13.9%-54.9%) in the surgical ward, and 7/33 (21.2%, 95% CI: 9.0%-38.9%) in the medical wards. Five (27.8%) of the 18 patients meeting the criteria for OH had isolated systolic OH, while 7 of 18 (38.9%) had isolated diastolic OH and 6 of 18 (33.3%) had mixed OH. OH had no association with symptoms. The majority of the OHP patients remained asymptomatic, while a significant proportion of OHN patients complained of orthostatic dizziness on standing (Table).
Comparison of Symptoms, Demographics, Comorbidities, Admission Diagnoses, Laboratory Results, and Medication Use Between the Orthostatic Hypotension–Positive and Orthostatic Hypotension–Negative Groups
We did not find significant differences in the OHP and OHN groups with regard to baseline patient characteristics, comorbidities, admission diagnoses, laboratory results, medication use, and the length of stay (Table), except for a statistically significant difference in the number of patients with gastrointestinal bleed as the admission diagnosis in the OHP group. The mean age of OHP gastrointestinal bleeders was 82.8 ± 9.0 years, while the mean age of OHP nonbleeders was 65.1 ± 20.8 years.
The OHN and OHP groups displayed very different patterns of physiological responses to orthostatic challenge that persisted over time (Figures 1 and 2). At supine baseline, the OHP group displayed higher resting SBP, DBP, and PR than the OHN group. Overall, the OHN group showed a statistically significant compensatory rise in SBP, DBP, and PR over time from the supine baseline to standing whereas the OHP group showed a statistically significant fall in both SBP and DBP. We found no statistically significant compensatory increase in PR over time to standing in the OHP group.
Differences in physiological behaviors between the orthostatic hypotension–negative (OHN) and orthostatic hypotension–positive (OHP) groups in terms of blood pressure (BP) responses to 3 minutes of standing. (*) indicates statistically significant increases in values compared to the supine baseline, whereas (**) indicates statistically significant decreases in values compared to the supine baseline. Values are mean, and error bars represent standard error.
Differences in physiological behaviors between the orthostatic hypotension–negative (OHN) and orthostatic hypotension–positive (OHP) groups in terms of pulse rate (PR) responses to 3 minutes of standing. (*) indicates statistically significant increases in values compared to the supine baseline. Values are mean, and error bars represent standard error.
DISCUSSION
Although OH is prevalent in the acute medical and geriatric settings,4,15 we expected it to be equally common in the acute surgical and trauma settings because of the additional risk factors of hypovolemia and immobility postsurgery.16 Our study demonstrated that the prevalence of OH was at least as common in the surgical and trauma wards as in the medical wards.
Many of our surgical and trauma patients did not participate in the study because of nonweightbearing status from underlying injuries and/or operations. This group consisted of a significant proportion of elderly patients who sustained fall injuries from presyncope and syncope events at home. According to the literature, up to 28% of syncope events could have been caused by OH.8,17-19 Hence, it is possible that by excluding this elderly trauma patient population, we might have underestimated the true prevalence of OH in the trauma ward.
Our study also demonstrated no differences with regard to symptoms between the OHP and OHN groups, raising the key message that OH is mostly asymptomatic and that symptoms are not a reliable discriminator. Previous studies have found similar results that suggested that only 30% to 40% of patients with OH would manifest typical symptoms while the others remained asymptomatic or had atypical symptoms.2-4 This makes the diagnosis of OH difficult, and thus routine measurements are required to vigilantly detect cases.
OH has been shown to be associated with neurodegenerative disorders such as primary autonomic dysfunction or Parkinson disease, leading to autonomic instability.7,20 None of our patients in the OHP group had known primary autonomic dysfunction or Parkinson disease; yet, the hemodynamic responses displayed by the OHP and OHN patients were distinctly different. Our study mirrored the previous findings that the OHP patients have higher supine BP compared to the OHN patients.2 The OHN group displayed normal physiological responses by having compensatory rises in BP and PR to the gravitational effects of standing, and this effect was sustained over time. However, OHP patients lacked this expected compensatory rise in BP. Instead, BP to standing fell, and this negative effect was sustained over time. In addition, the compensatory rise in PR was statistically significant only for the 1st minute of standing and was not sustained over time, thus suggesting inappropriately blunted homeostatic responses in the OHP group. Overall, these findings suggest that OHP patients display some degree of impaired intrinsic autonomic responses to orthostasis.
Similar to other studies,21 this study detected no differences in age, sex, presenting medical conditions, and comorbidities to satisfactorily explain the differences in hemodynamic behaviors between the OHN and OHP groups. This study also failed to find an association between the diagnosis of hypertension and OH, although some of the studies suggested a strong association between the two conditions.12,14,22 An exception was the incidental finding of a statistically significant number of patients with gastrointestinal bleed as an admission diagnosis in the OHP group. However, all of these patients had adequate supine BPs and volume replacement with blood transfusion (all had hemoglobin concentrations of >90 g/L) on the day of the study.
The recent British Women's Heart and Health Study (BWHHS)14 further supported our findings of lack of association between OH and individual chronic diseases other than hypertension. The BWHHS researchers reported that after adjusting for age and medication use, they found an association between OH and the number of chronic diseases per patient. Having multiple comorbidities is thus a strong predictor for the development of OH in older women. Therefore, we carried out post-hoc analysis to detect this association in our cohort of patients but failed to find any significant relationship between the number of comorbidities and OH (Table).
Medications are potentially modifiable risk factors for OH. However, the evidence on the relative contribution of each class of medication to the development of OH remains controversial and inconclusive as mentioned previously.4,8,14,16,18,23,24 Our study did not find any association between medication use and the presence of OH, further suggesting that the differences in hemodynamic responses between the OHN and OHP groups were more likely to be intrinsic and not attributable to any individual medications or clinical conditions.
Limitations and Strengths
We acknowledge that our study design contained a small sample size. Despite that fact, we detected meaningful physiologic differences between the two groups of patients and drew clinically useful conclusions. We recognize that large numbers of participants are necessary to more confidently detect true differences in risk factors between the two groups.
Our second weakness was that some of the BP measurements were conducted late in the morning and past noon when the likelihood of detecting OH was much lower.25 However, our study protocol for BP measurements simulated the day-to-day nursing practice in a busy hospital ward environment with constraints on time and resources as well as patient factors, because of which individual prescriptions for orthostatic BP measurements could not be executed in a timely manner.
CONCLUSIONS
This observational cohort study found that OH is a common occurrence in hospitalized elderly medical, surgical, and trauma patients. This study also found significant differences in hemodynamic responses to orthostatic challenge between OHP and OHN patients. The differences could not be readily accounted for by patient risk factors such as age, sex, comorbidities, presenting diagnoses, and medications, suggesting that OHP patients may have intrinsically impaired autonomic responses.
Our study challenges the current understanding of OH with the suggestion that OHP patients have the condition because of impairment in their autoregulatory mechanisms. We further propose that risk factors including medications and underlying medical conditions may exacerbate OH in patients intrinsically predisposed to it, rather than being the primary cause. Larger and more detailed physiological studies are needed for more in-depth understanding of these differences in hemodynamic responses, their causes, and the clinical implications in order to manage OH more effectively.
Because this study also demonstrated that a large number of patients with OH were asymptomatic, we recommend routine measurements in hospital settings to detect OH cases. Although we suggest this general approach, the current evidence is still unclear regarding the impact on clinical outcomes by preemptively identifying and treating asymptomatic and unsuspected OH positive cases.
This article meets the Accreditation Council for Graduate Medical Education and the American Board of Medical Specialties Maintenance of Certification competencies for Patient Care and Medical Knowledge.
ACKNOWLEDGEMENTS
We would like to thank medical students Jason Chapman, Aaron Bloch, and Wee Long Ong for their invaluable help in the project.
- Academic Division of Ochsner Clinic Foundation
