Morbidity and mortality in elderly trauma patients

Futility of resuscitation criteria for the "young" old and the "old" old trauma patient: a national trauma data bank analysis

BACKGROUND

Increasing geriatric trauma is producing disproportionate use of resources. In burn victims, age and burn extent correlate with mortality, yielding the establishment of criteria for futile resuscitation. Such criteria would be useful to trauma patients and their families in making withdrawal-of-care decisions while reducing resource use. Our objective, therefore, was to identify injury and physiologic parameters that would indicate a high probability of futile resuscitation among geriatric trauma patients.

METHODS

Data pertaining to patients greater than or equal to 65 years of age within the National Trauma Databank from 1994 to 2001 were analyzed. Multivariate logistic regression-with mortality as the outcome variable and head, chest, and/or abdominal injury; base deficit; gender; comorbidities; and admission systolic blood pressure (SBP) as covariates-was performed to develop a stratification scheme providing criteria indicative of a high probability of futile resuscitation.

RESULTS

There were 76,304 patients with a mean age of 79.4 years. Head, thoracic, and abdominal injury; age; gender; comorbidities; admission SBP; and base deficit were associated with mortality. Patients with severe chest and/or abdominal injury, moderate to severe head injury, admission SBP less than 90 mm Hg, and significant base deficit had mortalities approaching 100%. Older patients with modest shock and mild to moderate head injury admitted with severe chest and/or abdominal injury had a less than 5% chance of survival.

CONCLUSION

Geriatric trauma patients with severe chest and/or abdominal trauma with moderate shock and mild to moderate head injury have an exceedingly low probability of survival. These data support early withdrawal of care in these individuals.

Skeletal injury patterns in older females

Injury patterns in elderly patients are different from those in younger patients. With recent emphasis on osteoporosis and its effects, we looked at a continuous series of patients from one Level 1 trauma center regarding injury patterns by gender. For all patients older than 65 years, and including all mechanisms, older women were more likely to sustain forearm and wrist fractures than were older men. For the individual mechanism of motor vehicle collision there was a significant increase in the extremity Abbreviated Injury Scores in older women compared with older men. Similarly, older women were more likely to sustain lower leg fractures and distal upper extremity fractures than were older men. This raises the possibility that increased bone loss, as seen in older women, may be reflected in the injury patterns they sustained given the same mechanism. More work is warranted in this region to potentially diminish these effects.

Age, Blood Transfusion, and Survival after Trauma

Blood transfusion affects outcomes after trauma, but whether elderly patients are disproportionately affected remains unknown. To determine the possible interaction between age, packed cell transfusion volume (PCTV), and mortality after injury, we designed a 6-year retrospective review (January 1995 through December 2000) of patients ≥16 years of age who received blood transfusion within the first 24 hours after injury. One thousand three hundred twelve patients ≥16 years of age admitted to our trauma center received packed red blood cells in the initial 24 hours after admission. Of the 1312 patients, 1028 (78%) were ≤55 years and 284 (22%) were >55 years of age, and overall mortality was 21.2 per cent. Age, Injury Severity Score (ISS) Glasbow Coma Scale (GCS), and PCTV emerged as independent predictors of mortality. PCTV for elderly survivors (4.6 units) was significantly less than that of younger survivors (6.7 units). Furthermore, mean PCTV for all survivors decreased progressively with advancing age. No patient >75 years with a PCTV > 12 units survived. Age and PCTV act independently, yet synergistically to increase mortality following injury.

Variations in injury patterns, treatment, and outcome for spinal fracture and paralysis in adult versus geriatric patients

STUDY DESIGN

Retrospective cohort analysis of hospital discharge and mortality data for spinal fracture and spinal cord injury patients in a single state from 1990 to 1995.

OBJECTIVES

Population-based review of preinjury patient factors, injury and treatment patterns, and in-hospital versus 60-day mortality in adult and geriatric spinal injury patients.

SUMMARY OF BACKGROUND DATA

While population-based analyses of hospitalized injured patients indicate that geriatric patients are at higher risk for adverse outcome, less is known about the specific subset of patients with spinal fracture and spinal cord injury. A specific knowledge gap exists regarding factors that influence survival after hospital discharge of spine-injured patients.

METHODS

Patients with cervical, thoracic, or lumbar spinal fracture were identified by ICD-9-CM discharge diagnosis codes. Age, gender, preexisting conditions, and injury severity were determined, and patients were divided into adult (ages 16-64 years; n = 6,029) and geriatric (ages >or=65 years; n = 3,973) groups. In-hospital and 60-day mortality rates and odds ratios of 60-day mortality were calculated relative to patient and injury characteristics, level of treating hospital, and surgical treatment.

RESULTS

Increased 60-day mortality was associated with preexisting medical conditions, increased injury severity, and paralysis but reduced with surgical treatment. Geriatric patients had fewer cervical injures, lower force injuries, less severe overall injuries, decreased paralysis, increased preexisting conditions, decreased treatment at level 1 and 2 treatment centers, and decreased odds of surgical treatment. Geriatric patients also had increased 60-day versus in-hospital mortality and increased mortality associated with cervical spine injury.

DISCUSSION

Differences exist in preinjury patient factors, injury and treatment patterns, and mortality between adult and geriatric patients following spinal injuries. The increased 60-day versus in-hospital mortality for the geriatric population suggests that 60-day mortality may be a better measure of outcome for these patients. While the possibility of selection bias exists, both geriatricand adult patients had reduced 60-day mortality associated with surgical intervention.

Effect of acute lung injury and acute respiratory distress syndrome on outcome in critically ill trauma patients

OBJECTIVE

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are known to be associated with increased mortality and costs in trauma patients. We estimated the independent impact of these conditions on mortality and cost, beyond the severity of injury with which they are correlated.

DESIGN

One-year prospective cohort.

PATIENTS AND SETTING

All trauma patients admitted to the intensive care unit in a level I center were evaluated daily for ALI/ARDS using the American-European Consensus Conference definition.

MEASUREMENTS AND MAIN RESULTS

The main outcome measures were hospital mortality and costs. Logistic regression was used to model hospital mortality in relation to the presence of ALI and ARDS, adjusting for trauma severity (Injury Severity Score), Acute Physiology Score, and age. Hospital costs were modeled using multivariable linear regression. Of the 1,296 trauma patients surviving beyond the first day, 4% experienced ALI (defined as Pao2/Fio2 of 201-300 mm Hg) and 12% had ARDS (Pao2/Fio2 < or = 200 mm Hg). The crude relative risk of mortality was 2.24 (95% confidence interval, 0.92-5.45) in patients with ALI and 3.84 (95% confidence interval, 2.41-6.13) in patients with ARDS compared with those without ALI/ARDS. However, there was no association of mortality with ALI (relative risk, 0.99; 95% confidence interval, 0.29-3.36) or with ARDS (relative risk, 1.23; 95% confidence interval, 0.63-2.43) after adjustment for age, Injury Severity Score, and Acute Physiology Score. Among patients of comparable age, severity score, and length of stay, median cost was 20% to 30% higher for those with ALI/ARDS.

CONCLUSIONS

There is no additional mortality associated with ALI/ARDS above and beyond the factors that can be measured at intensive care unit admission. Therefore, mortality in trauma patients is explained by injury severity at admission and is not affected by the subsequent occurrence of ALI/ARDS. Nonetheless, ALI/ARDS was associated with increased intensive care unit stay and hospital cost, independent of trauma severity.

The status of the Glasgow Coma Scale

The Glasgow Coma Scale (GCS) was first introduced in the 1970s to provide a simple and reliable method of recording and monitoring change in the level of consciousness of head injured patients. Since its introduction, the GCS has been widely utilized in the trauma community and its use expanded beyond the original intentions of the score. In the context of traumatic injury, this paper discusses the use of the GCS as a predictor of outcome, the limitations of the GCS, the reliability of the GCS and potential alternatives through a critical review of the literature. The relevance to Australian trauma populations is also addressed.

Functional outcomes in octogenarian trauma

BACKGROUND

Outcome data on geriatric trauma patients (GTPs) (age >or= 65) focus on mortality and resource use. We examined mortality and outcome in GTPs and octogenarian trauma patients (OTPs) (age >or= 80). We hypothesized that OTPs would have worse functional outcomes than GTPs as defined by functional independence measurement (FIM) scales.

METHODS

Our study was a 13-year retrospective analysis of a statewide trauma database. Isolated hip fractures and intubation with Glasgow Coma Scale scores of 3 at admission were excluded. Demographic data, preexisting conditions, complications, discharge destination, mortality, and FIM were analyzed.

RESULTS

OTPs constituted 17742 (40.9%) of 43297 GTPs admitted to trauma centers. Falls (64.4%) and motor vehicle collisions (24.5%) were predominant. Average Injury Severity Score (ISS) was higher in GTPs (11.5 +/- 9.2 vs. 10.8 +/- 8.3, p = 0.001). Cardiac disease was the most common preexisting condition. Diabetes, obesity, and pulmonary disease were more common in GTPs than in OTPs (p = 0.001). Dementia, congestive heart failure, and hematologic disease were more common in OTPs than in GTPs (p = 0.001). Pulmonary and infectious complications were most common and occurred with equal frequency in OTPs and GTPs. Mortality rates were higher (10.0% vs. 6.6%, p = 0.001) for OTPs overall and when stratified into low (<10), moderate (11-20), and high (>20) ISS subgroups (p = 0.001). Discharge destination was most often home (53.3% vs. 28.8%, p = 0.001) or a rehabilitation facility (20.0% vs. 17.4%, p = 0.001) for GTPs versus OTPs. OTPs were discharged to skilled nursing facilities (37.2% vs. 14.9%, p = 0.001) far more often than GTPs. FIM at discharge was lower in all categories for OTPs. Modified dependence in locomotion and transfer was seen for OTPs but not GTPs overall and when stratified by ISS subgroups (p = 0.001). Some dependence in feeding was seen for OTPs but not GTPs with high injury severity (p = 0.001). Otherwise, feeding, expression, and social independence were preserved for both OTPs and GTPs.

CONCLUSION

Functional outcomes after blunt trauma are worse for OTPs; however, functional independence in feeding and social interaction are preserved in OTPs even with moderate injury severity.

Endpoints for fluid resuscitation in hemorrhagic shock

Vigorous intravenous fluid resuscitation has become widely accepted as the optimum management of hemorrhagic shock in trauma. There is now, however, sufficient evidence for this position to be reviewed. Hypotensive or delayed resuscitation has been postulated as a means by which the mortality associated with treatment can be reduced. It has been suggested that overresuscitation with intravenous fluids may worsen hemorrhage. This article discusses the possible adverse effects of "conventional" resuscitation and examines the evidence to support alternative treatment modalities.

Morbidity from rib fractures increases after age 45

BACKGROUND

Recent studies have demonstrated increased morbidity in elderly patients with rib fractures after blunt trauma. As a first step in creating a multidisciplinary rib fracture clinical pathway, we sought to determine the relationship between increasing age, number of rib fractures, and adverse outcomes in blunt chest trauma patients, without major abdominal or brain injury.

STUDY DESIGN

We performed a retrospective cohort study involving all blunt patients greater than 15 years old with rib fractures, excluding those with Abbreviated Injury Scores (AIS) greater than 2 for abdomen and head, admitted to an urban Level I trauma center during 20 months. Outcomes parameters included the number of rib fractures, Injury Severity Score (ISS), intrathoracic injuries, pulmonary complications, number of ventilator days, length of stay in the intensive care unit (ICU), hospital stay, and type of analgesia.

RESULTS

Of the 6,096 patients admitted, 171 (2.8%) met the inclusion criteria. Based on an analysis of increasing age, number of rib fractures, and adverse outcomes variables, patients were separated into four groups: group 1, 15 to 44 years old with 1 to 4 rib fractures; group 2, 15 to 44 years old with more than 4 rib fractures; group 3, 45 years or older with 1 to 4 rib fractures; and group 4, 45 years or more with more than 4 rib fractures. The four groups had similar numbers of pulmonary contusions (30%) and incidence of hemopneumothorax (51%). Ventilator days (5.8 +/- 1.8), ICU days (7.5 +/- 1.8), and total hospital stay (14.0 +/- 2.2) were increased in group 4 patients compared with the other groups (p < 0.05). Epidural analgesia did not affect outcomes. Overall mortality was 2.9% and was not different between groups.

CONCLUSIONS

Patients over the age of 45 with more than four rib fractures are more severely injured and at increased risk of adverse outcomes. Efforts to decrease rib fracture morbidity should focus not only on elderly patients but those as young as 45 years. Based on these data we have initiated a multidisciplinary clinical pathway focusing on patients 45 years and older who have more than four rib fractures.

The role of cardiac morbidity in short- and long-term mortality in injured older patients who survive initial resuscitation

BACKGROUND

Elderly patients are an increasingly larger group of injured trauma care patients. Comorbidities influence outcome. Little is known of short- and long-term mortality in the elderly who survive initial resuscitation.

METHODS

Short- and long-term mortality was retrospectively analyzed in 363 consecutively injured patients (Injury severity score >15) surviving more than 3 days after admission to a level 1 trauma center (including 197 patients >60 years). Cardiac morbidity was the focus.

RESULTS

Survival to hospital discharge was similar comparing older patients with the entire group. Mortality increased incrementally with age. In older patients, cardiac morbidity was observed in 28% (fatal in 7); 2-year mortality was 36% (older group) and 60% (patients sustaining cardiac complications). Most elderly (80%) were discharged to long-term care.

CONCLUSIONS

Elderly who survive initial resuscitation are as likely to survive to discharge as younger patients, but long-term survival is significantly lower as age increases. Cardiac morbidity is associated with higher long-term mortality. Most elderly are discharged to long-term care.

Intensive Care Unit Outcome of Vehicle-Related Injury in Elderly Trauma Patients

Vehicle-related trauma is a common mechanism of injury in elderly (age ≥65 years) trauma patients. Several hospital-based studies have shown that patients with pedestrian injury have a higher mortality compared with those with motor vehicle collision (MVC) injury partially because of older patients found in the former group. In addition the injury patterns also differ significantly between these two mechanisms of vehicle-related trauma. The purpose of the present study is to compare the demographics, injury severity, injury patterns, and outcomes of elderly patients with pedestrian injury admitted to a surgical intensive care unit (SICU) of a Level I trauma center between January 1, 1994 and December 31, 2000 with those admitted with MVC injury. During the study period there were 187 elderly patients admitted to the surgical intensive care unit with vehicle-related injury. Fifty-one per cent of the patients had MVC injury. Patients were divided into two groups based on their mechanisms of injury (pedestrian vs MVC) for comparison. There was no difference in the mean age and gender between the two groups. Injury Severity Score, admission Simplified Acute Physiology Score, and mortality were significantly higher in the pedestrian group compared with the MVC group. Using logistic regression analysis three factors were found to be independently predictive of mortality: Simplified Acute Physiology Score, intracranial hemorrhage with mass effect on CT scan, and cardiac complications.

Survey of trauma patients requiring maxillofacial intervention, ages 56 to 91 years, with length of stay analysis

PURPOSE

The purpose of this study was to analyze trauma patients, ages 55 and older, sustaining multiple injuries including maxillofacial trauma. Factors influencing length of intensive care unit stay (ICUS) and length of total hospital stay were delineated and examined to determine if specific causes of increased length of stay could be elucidated, and, once known, if these causes could translate into recommendations tailored to the oral and maxillofacial surgery trauma practice.

PATIENTS AND METHODS

One hundred ninety-six patients, 55 years of age or older, who received either consultation alone, or consultation with surgical treatment, by oral and maxillofacial surgeons, from January 1991 to August 1998 were included in this study. Variables of interest included location of traumatic event, mechanism of injury, patient age and gender, comorbidities on presentation, Injury Severity Score (ISS), specific injuries incurred, ICUS, length of hospital stay (LOS), surgical interventions, and disposition.

RESULTS

Complications were the statistically significant factor determining length of ICU stay. ICUS, complications incurred, and ISS were the important predictors of total LOS. The significant complications affecting LOS were infectious, respiratory, and hematologic complications.

CONCLUSION

The number of complications the patient incurs after an injury can predict length of ICUS. Length of ICUS, ISS, and number of complications incurred were the strongest predictors for total length of hospital stay. Other variables, including age, gender, living or dead, blunt versus penetrating injury, ISS, fracture site (skull, midface, or lower face), and comorbidities on presentation were not statistically significant in this patient population. Infectious, respiratory, and hematologic complications were the complications most closely correlated with increasing length of ICUS and total hospital stay.

The geriatric heart: nurses need to be aware of how aging and disease affect the myocardium

Improved treatment for diabetes and cardiovascular disease have made it possible for elderly patients to remain active as well as mobile, but with a greater chance of sustaining traumatic injury.

Clinical Rib Fractures: Are Follow-Up Chest X-Rays A Waste of Resources?

Rib fractures (RFs) are estimated to be present in 10 per cent of all traumatic injuries. However, up to 50 per cent of all fractures go undetected on the screening chest X-ray (CXR). The purpose of this study was to identify the incidence of clinical (CRFs) and objective rib fractures (ORFs) as well as to examine the utility of the routine follow-up CXR with regard to patient recovery and healthcare cost. We identified patients sustaining RF in addition to other traumatic injuries with an Injury Severity Score (ISS) ≤15 and RF as the primary pathology. Five hundred fifty-two patients sustained blunt thoracic trauma with resultant RF. Two hundred nine patients had RFs and an ISS ≤15. The average ISS was 8. Follow-up films illustrated that 93 per cent of CRFs had resolution of any pathology, 4 per cent had persistent X-ray findings, and 4 per cent were lost to follow-up. Ultimately 93 per cent of patients with CRF were able to resume daily activities without disability and 3 per cent incurred lifestyle changes at home or work, which was significantly better than those with ORFs ( P < 0.05). Follow-up films produced no change in clinical management and cost approximately $2000/year. The prognosis for CRFs is excellent if treatment consists of appropriate pain management and pulmonary rehabilitation. We do not advocate routine follow-up CXRs in addition to physical examination for the evaluation of CRFs unless clinical deterioration is evident.

Rate of and risk factors for acute inpatient mortality after orthopaedic surgery

BACKGROUND

Orthopaedic surgeons operate on a diverse group of patients, and many of these patients have concomitant medical problems. The purpose of this study was to identify the rate of mortality and to evaluate the risk factors associated with mortality after orthopaedic surgery.

METHODS

Data from the National Hospital Discharge Survey, a nationwide sample of hospital admissions, were obtained for the years 1995 through 1997. The study was limited to hospital admissions. Univariate and multivariate analyses were performed.

RESULTS

The 43,215 inpatient orthopaedic operations that we evaluated were associated with a mortality rate of 0.92%. Seventy-seven percent of all deaths occurred after procedures performed for patients who were more than seventy years old, and 50% of all deaths occurred after operations performed for the treatment of hip fractures. The independent preoperative medical risk factors for death included chronic renal failure, congestive heart failure, metastasis to bone, atrial fibrillation, chronic obstructive pulmonary disease, and osteomyelitis. The risk factors of diabetes, coronary artery disease, peripheral vascular disease, septic arthritis, and rheumatoid arthritis did not achieve significance. Among orthopaedic subspecialty categories, operations for tumors, trauma, and infection were associated with elevated mortality rates. In a predictive model, five critical risk factors were identified as most helpful in identifying patients at risk for death: chronic renal failure, congestive heart failure, chronic obstructive pulmonary disease, hip fracture, and an age of greater than seventy years. The mortality rate was 0.25% for patients with no critical risk factors. A linear increase in mortality was seen with increasing numbers of critical risk factors (p < 0.005).

CONCLUSION

Death is rare after orthopaedic operations. In the United States, the rate of acute mortality after inpatient orthopaedic surgical procedures is approximately 1% for all patients, 3.1% for patients with a hip fracture, and 0.5% for patients without a hip fracture. These data will aid orthopaedic surgeons in predicting operative mortality for their patients.

Impact of discontinuing a hospital-based air ambulance service on trauma patient outcomes

BACKGROUND

The clinical benefit of aeromedical transportation of injured patients in the civilian population has been debated. The purpose of this study was to examine the effects of discontinuing a hospital-based helicopter transport program on trauma patient outcomes, with the hypothesis that the loss of an air ambulance would result in increased transport time and increased mortality among severely injured patients.

METHODS

Data on injury severity and patient outcomes were collected prospectively for the 12 months immediately preceding and 24 months following discontinuation of the helicopter ambulance service. Transport time, mortality rate, and hospital length of stay was compared.

RESULTS

The number of trauma patient admissions decreased 12%, with a 17% decrease in admissions of severely injured patients. Transport time decreased, with no change in mortality.

CONCLUSION

Discontinuation of a hospital-based air ambulance service did not increase transport time or increase mortality for trauma patients.

When is an elder old? Effect of preexisting conditions on mortality in geriatric trauma

BACKGROUND

As the U.S. population ages, the number of geriatric trauma victims will continue to grow. Outcomes are known to be worse for these patients, in large part because of preexisting conditions (PECs). The specific impact of various PECs on outcome in geriatric trauma has not been well studied because of heterogeneous data sets and sample sizes.

METHODS

We sought to define the impact of clinical variables and PECs on mortality in geriatric trauma by analyzing a large statewide trauma database. We defined geriatric trauma patients as those age > or = 65. Isolated hip fractures were excluded. We used multiple logistic regression to determine the effect of 21 different PECs on 30-day in-hospital mortality.

RESULTS

Data were abstracted from 33,781 patient records. Overall mortality was 7.6%. For each 1-year increase in age beyond age 65, odds of dying after geriatric trauma increased by 6.8% (95% confidence interval, 6.1-7.5%). When presenting vital signs, Glasgow Coma Scale score, and ISS were controlled, PECs with the strongest effect on mortality were hepatic disease (odds ratio [OR], 5.1), renal disease (OR, 3.1), and cancer (OR, 1.8). Chronic steroid use increased the odds of death after geriatric trauma (OR, 1.6), whereas Coumadin therapy did not.

CONCLUSION

Considered independently, these data are insufficient to allow withdrawal of care, but this information may be a useful component to help in guiding families faced with difficult decisions after geriatric trauma.

Geriatric trauma: special needs for a special population

Pediatric patients are not just "little adults" and elderly patients are not just "old adults." The elderly patient experiences physiologic and anatomic changes that affect all body systems. Providing trauma care for the elderly presents a particular challenge. Muscle atrophy, osteoporosis, and decreased subcutaneous tissue make the elderly patient more prone to a greater severity of injury. Alterations in the cardiovascular and respiratory systems limit the physiologic reserve the elderly need to respond to hypoxia and shock. Preexisting health conditions further complicate the picture. This article highlights some of the important differences in caring for an elderly trauma patient from resuscitation to rehabilitation.

Trauma in the very elderly: a community-based study of outcomes at trauma and nontrauma centers

BACKGROUND

Little research has examined trauma outcomes in the very elderly (>80 years), the fastest growing subset of our geriatric population. Our objective was to describe demographics, mechanism of injury and injury severity of very elderly trauma patients and examine the association between trauma center (TC) verification and hospital mortality in this age group.

METHODS

Retrospective cohort study. Database consisted of a 1996 countywide trauma registry. Subjects consisted of patients > 80 years of age. The setting consisted of Level I (TCI) and Level II (TCII) trauma centers, and acute care (AC) hospitals. The z score analysis was performed using the Major Trauma Outcome Study and a county-specific risk/outcome equation. In addition, a logistic regression model examined hospital mortality (outcome variable) using age, ISS, arrival GCS, and TC verification as predictor variables. Statistical analysis included descriptive statistics; ANOVA; and forward stepwise logistic regression model (OR; 95% CI).

RESULTS

Four hundred fifty-five patients with a mean age of 85.9 (+/-4.8) years (range 80-101). Overall mortality was 9.9%. Using z score analysis, survival at TCII performed as predicted (-1.59), while AC performed less than predicted (-3.41). In the regression model, GCS (OR 0.68; CI 0.57-0.79), ISS (OR 1.1; CI 1.05-1.2) and AC setting (OR 3.2; CI 1.1-9.5) predicted hospital mortality. TCs had significantly better outcomes than AC hospitals in a subset of severely injured patients (ISS 21-45) (56% v 8% survival; p < 0.01).

CONCLUSION

Risk-adjusted outcomes, in this population, differed between TC and AC settings. Head injury, injury severity, and lack of TC verification are associated with hospital mortality in very elderly trauma patients.

The effect of hypertension on the response to blood loss in a rodent model

OBJECTIVE

Hypertensive patients having higher baseline peripheral resistance and sympathetic tone than normotensive patients may have aberrant responses to hemorrhage. In an attempt to further characterize this clinical observation, the authors compared the hemodynamic and metabolic responses to hemorrhage between spontaneously hypertensive rats (SHR) and normotensive rats (NTR).

METHODS

Twenty adult rats (10 NTR and 10 SHR) were anesthetized with althesin via the intraperitoneal route. Femoral arteries were cannulated by cutdown. Twelve (6 SHR and 6 NTR) rats underwent controlled catheter hemorrhage of 25% of their total blood volumes. Eight rats (4 SHR and 4 NTR) served as nonhemorrhage controls. Mean arterial pressure (MAP) and base excess (BE) were measured prehemorrhage and then every 15 minutes for the next 120 minutes. Data were reported as mean +/- standard error of the mean (SEM). Group comparisons were analyzed by ANOVA with repeated values post-hoc by Bonferroni. Statistical significance was defined by an alpha = 0.05.

RESULTS

Immediately after hemorrhage, the SHR group experienced a significantly (p < 0.001) greater drop in MAP of 70 +/- 4% in the SHR vs 40 +/- 6% in the NTR. Blood pressure in the NTR returned to control values 15 minutes after hemorrhage, but the SHR remained relatively hypotensive for the entire length of the experiment. Base excess in the SHR decreased significantly (p < 0.004) by 8.2 +/- 2 mmol/L from control values, as compared with no changes in BE for the NTR.

CONCLUSIONS

The authors observed significant differences in the response to hemorrhage between hypertensive and normotensive rats. Hypertensive rats experienced a more profound hemorrhagic shock insult than normotensives for the same degree of blood loss.