Improvement of Mortality of Ruptured Abdominal Aortic Aneurysm Patients over 12 Years and Its Relationship with Tracheostomy

Article Outline

• Abstract
• INTRODUCTION
• PATIENTS AND METHODS
  • Comparison of Hospital Mortality and Pre-, Peri-, and Postoperative Features between the First and Second Groups
  • Identification of Prognostic Factors for Survival in rAAA Patients
• RESULTS
  • Comparison of Hospital Mortality and Pre-, Peri-, and Postoperative Features between the First and Second Groups
  • Identification of Prognostic Factors for Survival
• DISCUSSION
• CONCLUSIONS
• Acknowledgment
• REFERENCES
• Copyright

Cardiopulmonary complication after ruptured abdominal aortic aneurysm (rAAA) repair is an important cause of mortality. Early tracheostomy promotes patient recovery from respiratory morbidities. A policy of routine immediate tracheostomy was adopted in 1999 at our institution. This study investigates the trend of hospital mortality of rAAA patients over 12 years with particular reference to immediate tracheostomy. Consecutive rAAA patients operated during 1993-2004 were divided into two groups (first group, 1993-1998; second group, 1999-2002). Intra- and postoperative care was the same for all patients except that immediate tracheostomy was performed routinely in the second group and only selectively in the first. Hospital mortality of the two groups was examined. Patient characteristics, biochemical parameters, aneurysm feature, operative details, and clinical outcomes of the two groups (excluding 48 hr perioperative mortalities) were compared to identify prognostic factors of hospital mortality. Sixty-three patients were operated during the study period. The overall hospital mortality for the first and second groups was 62.5% (20/32) and 22.6% (7/31) (p = 0.001), respectively. Excluding the 48 hr mortalities, 57.1 % (12, n = 21) of patients in the first group and 85.7% (24, n = 28) of those in the second group survived to be discharged from hospital (p = 0.048). The pre-, intra-, and postoperative parameters were comparable between the two groups. Immediate tracheostomy was performed for all patients in the second group and only 52.4% (11) in the first group. Male gender, high creatinine level on presentation, postoperation cardiac morbidity, renal failure, and bowel ischemia were found to be associated with a higher mortality. Immediate tracheostomy is a significant factor associated with improved survival. In conclusion, a significant improvement of rAAA patients' in-hospital mortality was achieved during the study period. Tracheostomy performed immediately following rAAA repair is associated with better hospital survival.

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INTRODUCTION 

Ruptured abdominal aortic aneurysm (rAAA) is an emergency in vascular surgery which carries a high mortality. Earlier reports suggested that mortality for rAAA patients remained unchanged,¹, ², ³ whereas some suggested that mortality improves with time.⁴ Cardiopulmonary complications and multiorgan failure are the commonest causes of hospital mortality.⁵ In our institution, we observed that rAAA patients with tracheostomy performed immediately after aneurysm repair overcame respiratory and related complications better as they were more tolerant of mechanical ventilation and frequent bronchoscopic toilet. A policy of routine immediate tracheostomy was adopted from January 1999 onward for all rAAA patients. We aimed to investigate the survival trend of rAAA patients in our institution over 12 years (1993-2004) and to determine the effect of routine tracheostomy on hospital mortality.

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PATIENTS AND METHODS 

The study population consisted of consecutive patients presented with rAAA who had received open aneurysm repair in a single university hospital from January 1993 to December 2004. Patients with ruptured thoracoabdominal aneurysm, suprarenal aortic aneurysm, iliac artery aneurysm, or aortic dissections were excluded. All the operations were performed by a single vascular surgeon (S. W. K. C.) using a standard long midline incision and transperitoneal approach.

Emergency operation is offered to all patients presented with rAAA and admitted to Queen Mary Hospital unless no recordable blood pressure can be obtained on arrival. Patients decide whether to accept the operation or not. If a patient is not fully conscious, a relative will make the decision for operation. This policy has remained the same throughout the 12-year study period.

Concomitant immediate tracheostomy was performed at the conclusion of aneurysm repair in the operating theater on selected patients with known chronic cardiac [congestive heart failure, chronic rheumatic heart disease, atrial fibrillation, recent (6 months) myocardial infarction] or respiratory (chronic obstructive airway disease, bronchiectasis) comorbidities before 1999. Since January 1999, a policy of routine immediate tracheostomy has been carried out in all rAAA patients in the operating theater after aneurysm repair (except if a patient develops cardiac arrest and cannot be rescued during operation). The time of commencement of this policy is used to divide the rAAA patients into first (1993-1998) and second (1999-2004) groups. Tracheostomy was performed using the open technique with the neck extended immediately after closure of the abdominal wound. A tracheostomy tube of size 7.5 or 8 will be used depending on the body build of the patient.

Patients' demographics, blood pressure, biochemical data (hemoglobin, platelet, and creatinine level) on presentation, medical comorbidities, aneurysm characteristics, procedural details, postoperative course, and surgical outcome were recorded prospectively in a computer database.

Comparison of Hospital Mortality and Pre-, Peri-, and Postoperative Features between the First and Second Groups 

The end point of assessment was the hospital mortality of rAAA patients. Hospital mortality was further broken down into perioperative (48 hr) mortality and hospital mortality beyond 48 hr and compared between the two groups using Fisher's exact test. In this study, more emphasis was put onto hospital mortality beyond 48 hr.

Patient demographic data, preoperative condition, aneurysm features, operation details, and postoperative course were compared between the first and second groups (excluding 48 hr perioperative mortalities). Electrocardiogram changes suggesting myocardial ischemia or infarction, congestive heart failure causing pulmonary congestion, left heart failure in the absence of hypovolemia (ejection fraction <50%), and fast atrial fibrillation developed after operation were classified as major cardiac morbidities. Postoperation pneumonia or sputum retention that required bronchoscopic toilet or prolong ventilation for longer than 3 days, pneumothorax, pleural effusion that required tapping, and chest X-ray changes indicating adult respiratory distress syndrome were considered major pulmonary complications. Derangement of renal function together with oligouria that necessitated temporary or long-term renal dialysis was classified as a major renal complication. Bowel ischemia was diagnosed based on sigmoidoscopic or colonoscopic findings of mucosal ischemia. Wound infection with positive bacterial culture was considered a wound complication. The Mann-Whitney U-test was applied for continuous variables. Categorical variables of the two groups were compared using the chi-squared test and Fisher's exact test.

Identification of Prognostic Factors for Survival in rAAA Patients 

All patients (including both groups) who survived more than 48 hr after operation were analyzed for prognostic factors of survival. The associations of patients' pre-, intra-, and postoperative variables with hospital mortality were determined using the univariate analysis.

All statistical calculations were performed using SPSS version 10.0.1 (SPSS, Chicago, IL) and a two-tailed p value of <0.05 was considered significant.

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RESULTS 

Seventy-eight patients with rAAA were admitted from January 1993 to December 2004. Fifteen patients (19.2%, seven in the first group and eight in the second) did not receive operation due to moribund condition or refusal of surgery. The median age of patients operated was 75 years (range 49–90). Thirty-two rAAA patients were operated between 1993 and 1998 and 31 patients between 1999 and 2004. rAAA patients' treatment and surgical outcomes are listed in Figure 1.

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• Fig. 1. 

  Management and outcome of rAAA patients 1993–2004.

Comparison of Hospital Mortality and Pre-, Peri-, and Postoperative Features between the First and Second Groups 

A significant improvement of hospital mortality was observed during the study period. Twenty patients (62.5%) died among the first group and only seven (22.6%) died in the second group (p = 0.001). Eleven (34.4%) and three (9.7%) patients succumbed within the first 48 hr after operation in the first and second groups, respectively (p = 0.005).

Excluding 48 hr mortality, 12 (57.1%, n = 21) and 24 (85.7%, n = 28) patients survived in the first and second groups, respectively (p = 0.048). Immediate tracheostomy was done for all patients in the second group and only 52.4% (11 out of 21 patients) in the first group (p < 0.001). Patient demographics are shown in Table I. Comparing the patient characteristics of the first and second groups, the mean age, medical comorbidities, and biochemical parameters checked on presentation were similar. There was no significant difference in the size of aneurysm, aortic clamp time, operative time, as well as blood loss between the two groups (Table II). The volume of blood transfusion during operation was lower in the second group (p = 0.044). Immediately after operation, all rAAA patients required mechanical ventilation and inotropic support. Postoperation, pulmonary, cardiovascular, and renal complications were the most common morbidities; and their incidences were similar between the two groups. Both groups of patients required a similar duration of mechanical ventilation (Table III). The specific systemic complications of each patient in the first and second groups are listed in Table IV, Table V.

Table I. Demographic data, comorbidities, and biochemical parameters on presentation of rAAA patients (excluding 48 hr mortality)

Chi-squared test for categorical variables and Mann-Whitney U-test for continuous variables.

ASA, American Society of Anesthesiologists.

Table II. Aneurysm feature and procedural details of rAAA patients

Table III. Postoperative course of rAAA patients

Table IV. Listing of intra- and postoperative systemic complications of first-group rAAA patients

DIC, disseminated intravascular coagulopathy; AF, atrial fibrillation.

Table V. Listing of intra- and postoperative systemic complications of second-group rAAA patients

DIC, disseminated intravascular coagulopathy; AF, atrial fibrillation; MI, myocardial infarction.

Identification of Prognostic Factors for Survival 

Univariate analysis showed male gender (p = 0.047), elevated creatinine level on presentation (p = 0.002), and presence of major cardiac complication (p = 0.031), renal failure (p = 0.017), or bowel ischemia (p = 0.002) after operation were associated with a higher hospital mortality (Table VI). Immediate tracheostomy is a significant factor associated with better survival (p = 0.006).

Table VI. Univariate analysis of prognostic factors of rAAA patient hospital mortality

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DISCUSSION 

rAAA without operation carries 100% mortality. Even with prompt emergency operation, high mortality remains one of the unresolved problems in vascular surgery. Kantonen et al.⁶ studied the correlation between the patient volume of a vascular surgery center and hospital mortality and found an inverse relationship between the two. Cassar et al.⁷ showed a decrease in hospital mortality related to increasing distance traveled to hospital. Recent reports on hospital mortality of rAAA patients ranged 23.5–63.3%.⁴, ⁶, ⁷, ⁸, ⁹, ¹⁰ In a meta-analysis of operative mortality of rAAA, the overall mortality was 48% over a study period of 50 years.⁴ An improving trend of mortality at about 3% reduction per decade was noted. We also observed an improvement of rAAA patient hospital mortality in our institution over the recent 12 years. The time of survival improvement coincides with the time of starting routine immediate tracheostomy. A comparative study with historical controls using prospective data was performed to determine the association between immediate tracheostomy and survival instead of a prospective randomized trial because informed consent is impossible to obtain in an emergency situation.

Hospital mortality of rAAA patients after surgery can be classified into perioperative (usually during or within 48 hr after operation) and subsequent mortality. The causes of death in these two types of mortality are different.¹¹ Patients having perioperative mortality usually are those who presented late or with a very poor premorbid medical condition. They usually died of cardiac arrhythmia or persistent hemorrhagic shock and would not have been salvageable no matter what surgical treatment or postoperative care was provided. Patients who survived the initial 48 hr after operation usually died of other systemic complications or multiorgan failure, and those mortalities are more likely to be amendable by improvements in peri- and postoperative care. Therefore, we excluded 48 hr mortality in the comparison of the first and second groups and the analysis of prognostic factors for mortality in the present study.

Univariate analysis was applied to identify significant associated factors of hospital mortality for rAAA patients. Multivariate analysis was not performed because of the relatively small number of patients in both subgroups. Among the six identified risk factors for hospital mortality, patient gender and preoperative creatinine level are preoperative predictive factors that cannot be altered. The presence of major cardiac morbidities, renal failure, and bowel ischemia are ominous postoperative features for survival. Immediate tracheostomy is the only factor that a surgeon can actively use to improve the outcome of patients with rAAA.

As a result of the catastrophic effect of massive bleeding in rAAA, significant wound pain from a long midline incision, oozing around the retroperitoneum due to coagulopathy, or ileus of the bowel, all patients required mechanical ventilation support after surgical repair. Respiratory complication was one of the commonest postoperative morbidities⁵ observed. Cardiovascular and renal complications may lead to fluid accumulation in the lung and further impair respiratory function. The incidence of major respiratory, cardiac, and renal complications was comparable between the first and second groups despite a higher percentage of immediate tracheostomy in the second group. However, patients having immediate tracheostomy probably can overcome the respiratory complications eventually through easier sputum suction and lesser discomfort with mechanical ventilation. With the presence of tracheostomy, a more gradual ventilator-weaning program can be adopted to ensure that the patient has adequate strength of ventilation and coughing effort. Ventilator support can also be easily reapplied if the patient deteriorates again. Indeed, we believe the beneficial effect of immediate tracheostomy for rAAA patients will probably be the same if tracheostomy is performed very early after aneurysm repair during the postoperative period. Nonetheless, in our institution, performing tracheostomy right after aneurysm repair is the most efficient way to establish a secure airway and facilitate bronchoscopic toilet in the early postoperative period. Thus, the policy of routine immediate tracheostomy has been in place since 1999. According to our experience, complications associated with immediate tracheostomy are uncommon and usually minor. We encountered one patient with subcutaneous emphysema in the first group and two with subcutaneous emphysema together with one wound edge bleeding in the second group.

The overall mortality of patients operated in 1999–2004 (22.6%) was significantly lower than that of those operated in 1993–1998 (62.5%) (p = 0.001). Both 48 hr mortality (p = 0.005) and subsequent in-hospital mortality (p = 0.048) were reduced over the 12 years, signifying that there was improvement in preoperative diagnosis or patient transferal as well as peri- and postoperative treatment and support.

Other possible factors to explain the decrease in hospital mortality that could not be assessed in this study include (1) improvement in surgeon's technique of operation, (2) improvement of population's general health condition, (3) improvement of community patient referral and transportation to hospital, (4) better disease diagnosis in the emergency department, (5) change in patient selection criteria for operation, (6) advances in anesthetic technique and care, and (7) improvement of postoperative care in the intensive care unit.

Forbes et al.¹² noted that the mortality rate after surgery of rAAA patients with a particular surgeon improved with increasing experience. However, the improvement of mortality rate in our patients occurred during the seventh year of the study, and that is unlikely to be explained by one's learning curve. Moreover, the aortic clamp time and the total operation time were comparable between the two groups. The volume of blood transfusion during operation was lower for the second-group patients (p = 0.044). However, blood transfusion was usually required even after the operation in the intensive care unit; therefore, whether the total volume of blood transfusion was different between the two groups was uncertain. Volume of blood transfusion was also not found to be associated with survival in the univariate analysis. The average age, gender ratio, and pre-morbidities of patients in the first and second groups were comparable. Therefore, improved surgical technique and better general population health could not explain the improvement in survival.

The reduction of perioperative mortality of rAAA patients suggests that fewer nonsalvageable patients were operated. This may be related to earlier patient presentation to hospital, the emergency room medical staff diagnosing the disease without delay, or a change of patient selection. The availability of an ultrasound machine¹³ in the emergency room as well as the training of medical staff operating it do facilitate early accurate diagnosis of patients presenting with back or abdominal pain harboring an rAAA. The criteria for offering surgery to rAAA patients were the same throughout the 12 years. Whether there was any subtle change in patient selection is difficult to assess. Nonetheless, the percentage of rAAA patients who did not receive surgery was similar during the two periods.

Anesthesia for rAAA patients was provided by on-call anesthetists in hospital and not a particular assigned anesthetist, and there was no specific anesthetic protocol used. Thus, whether the technique of anesthesia affected rAAA patients survival is difficult to determine.

The beneficial effect of immediate tracheostomy cannot be achieved without proper ventilation support. Unfortunately, in our prospective data, the details of intensive care provided (mode of mechanical ventilator, frequency of bronchoscopic toilet, type and dosage of vasopressors, use of invasive monitoring device, etc.) were not included. Nevertheless, we do believe the quality of intensive care during the postoperation period has an important impact on rAAA patients' outcome. Also, those parameters will be recorded in our future prospective data collection.

With prompt surgical treatment, immediate tracheostomy after aneurysm repair, and proper postoperative care, the prognosis of patients suffering this deadly disease is much improved. The survivors of rAAA were also proven to enjoy similar life expectancy¹⁴ and quality of life¹⁵ as the age- and sex-adjusted general population. To achieve further reduction of mortality, the advancing technique of endovascular treatment might provide some clues,¹⁶, ¹⁷ and more evidence is anticipated.

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CONCLUSIONS 

The hospital mortality of rAAA patients has reduced from 62.5% to 22.6% over 12 years. Routine tracheostomy immediately following open repair of rAAA is associated with a better survival and is recommended

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We thank Ms. Grace C. Y. Cheung and Ms. Christine K. Y. Cheung for their data keeping and secretarial support and Dr. C. M. Lam for his help in collection of hospital data.

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