AJA Asian Journal of Anesthesiology

Advancing, Capability, Improving lives

Research Paper
Volume 59, Issue 2, Pages 58-68
Jui-Ying Chung 1.2.3 , Pei-Chi Ting 1.2.3 , Chia-Ling Wu 4 , Huang-Ping Yu 2.3
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Abstract

Background: Surgical outcomes and complications in geriatric patients may be affected due to their increased number of underlying diseases. This study was conducted to evaluate the risk factors for postoperative complications and their effects on hospital stay in geriatric surgical patients (aged ≥ 80 years).

Methods: A total of 404 geriatric patients (aged ≥ 80 years) who underwent noncardiac surgery were enrolled in this study. Their preoperative, perioperative, and postoperative data were collected and subjected to univariate and multivariate analyses to calculate the odds ratio of risk factors. The risk of discharge was analyzed by calculating the hazard ratio to evaluate their relationship with postoperative complications.

Results: Approximately three-fourths (76.0%) of the patients had hypertension preoperatively, and 5.9% of them developed at least one postoperative complication. Respiratory disorders were the most frequent postoperative complications. Multivariate analysis revealed emergency surgery, preoperative renal diseases, preoperative anemia, and nonextubation as risk factors for postoperative respirator complications. Intraoperative estimated blood loss of > 500 mL and intraoperative low blood pressure were identifi ed as risk factors for postoperative neurological complications. Intraoperative hypothermia was found to be a risk factor for postoperative renal complications. Postoperative respiratory complications, postoperative neurological complications, and infection statistically signifi cantly prolonged the length of hospital stay. The in-hospital mortality rate was 1.0%.

Conclusion: Patients aged ≥ 80 years under certain conditions need more attention to prevent the development of different types of postoperative complications. Those who did develop postoperative respiratory complications, postoperative neurological complications, and infection might require prolonged hospitalization. Physicians must pay more attention preoperatively to the risk factors that increase postoperative complications.

Keywords

geriatric surgical patient, postoperative complication, risk factor


Introduction

With the improvement in medical quality and health care system, life expectancy has been increasing in most of the countries. Surgeons and anesthesiologists are now encountering an increasing number of geriatric surgical patients.1 Previous studies have demonstrated that surgical outcomes and complications in geriatric patients may be affected due to their reduced physical reserve and increased number of underlying diseases.2-6

Tang et al. analyzed 7,479 adult surgical patients in Australia7 and found that geriatric surgical patients accounted for 14.5% of all adult patients and were at increased risk for adverse postoperative outcomes under emergent procedures. The possible development of these postoperative complications might have strong relationships with the American Society of Anesthesiologists Physical Status Classification, which is based on the preoperative condition of patients.8 Since the past several years, there have been similar studies investigating the relationship between preoperative comorbidities and postoperative outcomes.9-15 Also, a prospective cohort study on the relationship between perioperative variables and length of hospital stay was conducted in 2001.16 However, till date, there have been limited studies exploring the relationships between perioperative variables and postoperative outcomes in the Taiwanese geriatric population. A better understanding of the effect of perioperative conditions on postoperative conditions might help in reducing the rate of certain postoperative complications by improving anesthesia care during surgery. A previous study conducted by St-Louis et al. on patients undergoing acute care surgery showed that patients aged ≥ 80 years had a higher risk of developing complications and had longer hospital stay than younger patients.9 It is known that longer hospital stay may cause additional clinical costs to the hospital. Hence, identifying the relationship between each complication and its effect on the length of hospital stay could help understand more about the different complications in detail, which could consequently aid in improving the efficacy of the entire medical care.

Therefore, the aim of the present study was to analyze the postoperative complications of Taiwanese geriatric patients aged ≥ 80 years who underwent anesthesia for noncardiac surgeries. Moreover, the mechanism through which these postoperative complications affected the length of hospital stay in these patients was examined.

Methods

The study protocol was evaluated and approved by the ethics committee of Chang Gung Memorial Hospital (202001839B0). The authors assured and certified that this research has been conducted in accordance with all of the ethical standards required by the Declaration of Helsinki issued in 2013. The records of patients aged ≥ 80 years who underwent anesthesia for a noncardiac surgery from January 1, 2019, to June 31, 2019, were selected from our anesthesia quality assurance (QA) database. This database was constructed using a number of database cards and provided the surgery-associated variables required for the present study. When an anesthesiologist performs anesthesia, he or she will register a database card in the database in a computer in the operating room. A nurse anesthetist confirms the data during the time of care. The database contained the following data: patients’ demographics, anesthetic technique, preoperative comorbidities, perioperative management details, and intraoperative complications. Each of the perioperative monitoring data such as blood pressure, oxygen saturation, temperature, or end-tidal carbon dioxide will be captured automatically into the computer to form an electronic anesthesia record. On the next day, an anesthesia staff will visit these patients to check their postoperative conditions to look for any complication or discomfort. Surgeons document the postoperative conditions on electronic charts during their postoperative care in wards or intensive care units. We obtained the postoperative data by reviewing these documents, completing the entire QA protocol. A quality-improvement coordinator from the QA committee in the anesthesia department checks the electronic anesthesia records, reviewing electronic charts, and database data to ensure our database is validated and ascertained.

Preoperative data consisted of patients’ demographics, which included age, sex, body weight, elective or emergency surgery, and comorbidities. Comorbidities included cardiovascular diseases, pulmonary diseases, hepatic diseases, renal diseases, cerebrovascular accidents, diabetes, anemia, cardiac arrhythmia, malignancy, psychiatric disorders, and morbid obesity. Cardiovascular diseases included hypertension and coronary artery disease (CAD). Pulmonary diseases consisted of asthma, pneumonia, chronic obstructive pulmonary disease, and restrictive lung disease. Patients with a body mass index of ≥ 40 kg/m2 were defined as having morbid obesity. Any abnormalities in hepatic function and renal function or mental illness were also evaluated.

Perioperative data consisted of the types of surgery, types of anesthesia, blood pressure variation, body temperature, saturation, fluid infused, end-tidal carbon dioxide, and surgical duration. Anesthesia types were categorized into general anesthesia (with endotracheal intubation or a supraglottic device), regional anesthesia, and intravenous general anesthesia (IVG) without endotracheal intubation or a supraglottic device. The types of surgery were categorized into general, neurological, orthopedic, ear, nose, and throat, proctologic, thoracic and vascular, urological, obstetrics and gynecological, and others (ophthalmic, dermatological, dental, and plastic surgeries). Abnormal intraoperative conditions that were assumed to affect mortality and morbidity were selected, which included low perioperative body temperature (body temperature < 35.9°C), hypothermia (body temperature < 35°C), abnormal blood pressure (> 180/110 or < 80/40 mmHg), arrhythmia, and nonextubation at the end of surgery. The presence of abnormal blood pressure or hypothermia was defined by whether the data was captured by the monitoring computer or not. Since the computer system was designed to record the patients’ perioperative vital signs automatically every 5 minutes in our hospital, the duration of abnormal blood pressure or hypothermia must be at least close to 5 minutes long for the computer to capture. If abnormal blood pressure or hypothermia did happen but recovered in just such a short time without the noticing of the monitoring computer, we would not be able to count them in. Patients undergoing local anesthesia or receiving cardiac surgery were excluded.

Postoperative data included 6 types of complications, length of hospital stay, and death. Postoperative complications were classified into the following 6 types: respiratory complications, renal complications, cardiovascular complications, neurological complications, infection, and shock. Respiratory complications included chest radiography–confirmed pneumonia, pulmonary edema, and respiratory failure. Renal complications included acute renal failure or acuteon-chronic renal failure. Cardiovascular complications consisted of myocardial infarction, documented arrhythmia, and heart failure. Neurological complications included intracranial hemorrhage, seizure, stroke, and transient ischemic attack. Infection was confirmed by positive postoperative culture documentation. If the abovementioned diagnoses were present before the surgery, we did not count them as postoperative complications. The duration of hospitalization was also analyzed.

All the collected data were input into a Microsoft Excel spreadsheet (Microsoft Corporation, Redmond, WA, USA). SAS 9.4 (SAS Institute Inc., Cary, NC, USA) was used for the statistical analysis of our preoperative, perioperative, and postoperative variables. We used frequency tables for categorical variables and descriptive statistics for mean and standard deviation of continuous variables. Variables that were significantly associated with postoperative complications in the univariate analysis were then entered into a multivariate logistic regression model. In this manner, each variable was evaluated for its association with postoperative complications by controlling all other confounding variables. Variables with P < 0.05 were considered to be statistically significant. We then summarized the odds ratios and 95% confidence intervals of these variables. Moreover, because the final outcome of each patient was either discharge or death in the end, we used competing risk analysis to check how these postoperative complications affected the patients’ risk of discharge or mortality. SAS 9.4 was also used to analyze the hazard ratio and cumulative incidence rates.

Results

A total of 404 patients aged ≥ 80 years who underwent noncardiac surgeries were enrolled in this study. The demographic data and preoperative comorbidities are presented in Table 1. The mean age of the patients was 85.74 ± 4.30 years (range 80–106 years). The mean body weight was 58.38 ± 11.32 kg (range 35–90 kg). There were 229 men (56.7%) and 175 women (43.3%). Only 38 patients (9.4%) received emergent surgeries, and the remaining majority of them received elective surgeries. Among preoperative comorbidities, the most frequently observed preoperative comorbidity was hypertension (76.0%), followed by diabetes (29.2%) and CAD (17.3%). The least frequent 2 preoperative comorbidities were morbid obesity (1.0%) and psychiatric disorders (0.7%).

Table 1. Demographic Data, Preoperative Comorbidities, Perioperative Variables, and Postoperative Data of Patientsa
Table 1.
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Table 1. Demographic Data, Preoperative Comorbidities, Perioperative Variables, and Postoperative Data of Patientsa (continued)
Table 1.
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Table 1 also shows the perioperative and postoperative variables. General anesthesia (75.0%) was the most common method for these patients compared with regional anesthesia (15.8%) and IVG anesthesia (9.2%). Almost half of the surgeries were orthopedic (44.6%), followed by urological (18.6%) and neurological (11.6%) surgeries. These 3 specialties accounted for almost three-fourths (74.7%) of the surgeries in our study.

Regarding intraoperative abnormalities, almost half of the geriatric patients (47.8%) developed a low perioperative body temperature (< 35.9°C), and some of them (39 patients, 9.7%) even developed perioperative hypothermia (body temperature < 35°C). Other intraoperative abnormalities were as follows: low blood pressure (100 patients, 24.8%), high blood pressure (99 patients, 24.5%), bradycardia (32 patients, 7.9%), and tachycardia (6 patients, 1.5%). Regarding perioperative management, 94.6% (382 patients) of the patients had an estimated blood loss of < 500 mL, whereas only 5.5% (22 patients) had an estimated blood loss of > 500 mL. Only a few patients (11 patients, 2.7%) required crystalloid infusion of > 1500 mL, and 34 patients (8.4%) required colloid (Voluven) infusion perioperatively.

Regarding postoperative outcomes, only 21 patients (5.2%) were not extubated in the operating room. Respiratory complications occurred in the majority (24 patients, 6.0%) of patients. Other postoperative complications were as follows: infection (22 patients, 5.5%), neurological complications (9 patients, 2.2%), renal complications (5 patients, 1.2%), cardiac complications (2 patients, 0.5%), and shock (2 patients, 0.5%). As there were only 2 patients with postoperative cardiac complications and shock, respectively, we did not proceed with further analyses about their relationship with preoperative comorbidities and perioperative variables. The remaining 4 types of postoperative complications were then analyzed by univariate analysis and multivariate analysis. We examined their correlation among preoperative comorbidities and perioperative variables. The results are shown in Tables 2–5.

Table 2. Relationship Between Perioperative Characteristics and Postoperative Respiratory Complication
Table 2.
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Table 3. Relationship Between Perioperative Characteristics and Postoperative Neurological Complication
Table 3.
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Table 4. Relationship Between Perioperative Characteristics and Postoperative Renal Complication
Table 4.
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Table 5. Relationship Between Perioperative Characteristics and Postoperative Infection
Table 5.
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For respiratory complications, we found that emergency surgery, preoperative renal diseases, preoperative anemia, and nonextubation were statistically significant risk factors for increased postoperative respiratory complications. Patients undergoing emergent surgeries were 6.13 times more associated with postoperative respiratory complications than those undergoing regular surgeries. Patients with preoperative renal diseases were 16.84 times more associated with postoperative respiratory complications than those without preoperative renal diseases. Patients with preoperative anemia had 6.64 times of the risk of developing postoperative respiratory complications compared with patients without anemia. Patients who were not extubated in the operating room immediately after their surgeries were 34.18 times more associated with postoperative respiratory complications than those who were extubated successfully in the operating room. These results are presented in Table 2.

Regarding neurological complications, we found that an intraoperative estimated blood loss of > 500 mL and low intraoperative blood pressure were statistically significant risk factors for increased postoperative neurological complications. Patients with an estimated blood loss of > 500 mL were 6.47 times more associated with postoperative neurological complications than those with less estimated blood loss. Patients suffering from low intraoperative blood pressure were 5.1 times more associated with postoperative neurological complications than those who were not. These results are shown in Table 3.

Regarding renal complications, we detected that intraoperative hypothermia was a statistically significant risk factor for increased postoperative renal complications. Patients developing intraoperative hypothermia were 14.09 times more associated with postoperative renal complications than those who had a rather higher perioperative body temperature. These results are presented in Table 4. Regarding postoperative infection, no statistically significant correlation was observed between the factors we selected for this study. These results are shown in Table 5.

Postoperative complications may result in extended hospital stay of the patient. Combined with the length of hospital stay, we investigated the cumulative incidence of the risk of discharge using univariate and multivariate analyses. Our results demonstrated that postoperative neurological complications, respiratory complications, and infection affected the incidence of discharge. Patients developing postoperative respiratory complications were more unlikely (0.13 times) to get discharged from the hospital than patients without those complications. Postoperative neurological complications and infection also affected the risk of discharge with different levels of statistical significance (Table 6).

Table 6. Relationship Between Postoperative Complications and Discharge Risks Using Competing Risks Analysis
Table 6.
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Discussion

In the present study, hypertension was found to be the most frequent preoperative abnormality, which was detected in more than three-fourths (76.0%) of the geriatric patients. This finding was consistent with a previous study,14 although the prevalence of hypertension in that study was only around 50%. Hence, hypertension prevalence was much higher in Taiwan, indicating that blood pressure control has become a serious issue among the geriatric population. The second and third frequently detected preoperative abnormalities were diabetes (29.2%) and CAD (17.3%), respectively. Interestingly, although there were a large number of patients with these preoperative comorbidities, all these three topmost prevalent abnormalities did not statistically significantly affect the rate of developing postoperative complications. Other studies have also shown that preoperative hypertension and diabetes were not significant risk factors for postoperative morbidity and mortality in elderly patients.13-15 In our study, only two preoperative abnormalities (i.e., preoperative renal disease and anemia) were found to significantly affect the rate of developing postoperative complications. Patients having these 2 preoperative abnormalities were more likely to develop postoperative respiratory complications (16.84 times for preoperative renal diseases and 6.64 times for anemia), which were the most frequent postoperative complication, resulting in prolonged hospital stay for the patients. A recent study conducted by National Taiwan University Hospital also showed that chronic renal failure was the leading comorbidity contributing to 30-day mortality after anesthesia.15 Therefore, due to a large number of patients under hemodialysis, it might be necessary to emphasize the importance of preoperative renal problems before performing surgery for the geriatric population.

Three perioperative variables were found to significantly affect the development of postoperative complications. In this study, we identified an intraoperative estimated blood loss of > 500 mL and intraoperative hypotension as the 2 risk factors for postoperative neurological complications. Mashour et al. discussed the risk factors for perioperative stroke and indicated that risk factors such as anemia, hypotension, and dehydration did increase the rate of stroke in patients undergoing noncardiac surgeries.17 Our result was consistent with their study. The variables associated with blood loss tend to play some role in neurological complications. Although the estimated blood loss for patients may be uncontrollable, we can still help patients control their blood pressure and fluid infusion in the perioperative period whenever we encounter a situation of increasing blood loss.

Another interesting finding in our study was that intraoperative hypothermia was the risk factor for postoperative renal complications (acute renal failure or acute-on-chronic renal failure). Hypothermia is defined as a core body temperature of < 35°C, which could be a life-threatening situation. Patients with advanced age are susceptible to developing accidental hypothermia because of their impaired ability to control body temperature.18 It has been reported that hypothermia is related to acute kidney injury in > 40% of cases.19 Yoon et al. reported a case of a geriatric patient who suffered from hypothermia-induced acute kidney injury, which also resulted in changes in electrocardiography during the initial phase.20 Fortunately, the patient recovered due to rapid rewarming therapy and supportive care provided by the clinicians. Moreover, a recent study conducted in Brazil on intraoperative hypothermia-related complications demonstrated that intraoperative hypothermia did statistically significantly (P < 0.05) increase the duration of hospitalization, nausea, pain, evacuation, and surgical wound secretion21 Intraoperative hypothermia appeared to have more influence on the patients than we had believed. Today, in Taiwan, an increasing number of patients and physicians are becoming aware of the importance of the qualities of anesthesia, one of which is perioperative body temperature control. Several methods for maintaining perioperative core body temperature such as resistive heating and forced-air warming are now widely applied to surgical patients.22

For the risk factors we found developing postoperative complications in our study, most of them were pre-existing comorbidities or surgical-related conditions, which anesthesiologists might not be able to change effectively or to control efficiently. However, we did find 2 risk factors that could be manageable by anesthesiologists, which were intraoperative hypotension and hypothermia. These were the risk factors found causing postoperative neurological complications and postoperative renal complications separately in this study. Hypotension may be prevented through several means such as adjusting hypertensive medications properly before surgery, adequate fluid infusion, or wrapping of legs with elastic bandages in patients of certain surgical positions and so on. Hypothermia may be prevented through warm fluid infusion, resistive heating, or forced-air warming system. All these details may not only help patients reduce postoperative complications but also improve the whole quality of anesthesia easily. As for those risk factors, anesthesiologists may not be able to change or control effectively, optimizing patients’ condition as possible and fully communicating with patients and families prior to surgery become important.

In the present study, postoperative infection showed no correlation with any of the preoperative or perioperative variables. This might be due to the fact that the variables we selected were not related to the actual cause of infection. As there were 22 patients (5.5%) who developed postoperative infection, thus rendering their hospital stay longer, the associated variables may still need to be identified to prevent this situation. Nutrition parameters and infectious diseases are well known to be related to each other.23 In our study, there was a lack of data on the nutrition profile for these patients, due to which the relationship between nutrition and infection could not be evaluated.

In recent years, studies have been conducted on variables affecting postoperative mortality rates. Some studies have focused on the relationship between postoperative complications and postoperative mortality, and others have focused on the relationship between preoperative comorbidities and postoperative mortality.4,8,13,15 However, not many studies have focused on the aspects of the length of hospital stay in surgical patients especially in Taiwan, considering that longer hospital stay may cause more medical costs for the hospital or to the health care system. The median and interquartile range of length of hospital stay in our study was 3.0 and 4.5 days. An earlier study reported that the average length of hospital stay was 7.00 ± 6.66 days (mean ± standard deviation) for the same age group of patients (aged ≥ 80 years).24 In our study, the length of hospital stay was affected by three postoperative complications, including neurological complications, respiratory complications, and infection. This might help us to provide patients with answers regarding the entire length of hospital stay after their surgery and allow us to gain a better understanding of the medical cost for patients with certain risk factors requiring surgical treatments.

The in-hospital mortality rate of our study patients was 1.0%. Comparatively, previous data have reported in-hospital mortality rates of patients aged > 80 years as 0.54% in Poland in 2019,24 and 0.8% in another study conducted in 2020.13 However, besides the in-hospital mortality rate, the 30-day postsurgical mortality rate is another way to evaluate the surgical outcomes of geriatric patients. A study conducted in 2005 reported a 30-day all-cause mortality rate of 8% in surgical patients aged > 80 years.4 In a previous review from the American College of Surgeons National Surgical Quality Improvement Program database in 2006, the 30-day mortality rate of surgical patients aged > 80 years was reported as 7%.6 Other previous studies have mortality rates ranging from 5% to 10%.14,16 Hence, there exists an obvious difference between in-hospital mortality rate and 30-day postoperative mortality rate, indicating the poor recovery condition of these geriatric patients after their surgeries. Although they survived through their surgeries and were discharged from the hospital, they may suffer from fatal conditions occurring during their postoperative 30 days of recovery, which increases their mortality rate, i.e., from an in-hospital mortality rate of < 1% to a post-anesthesia mortality rate of 5–10%.

Several studies have also indicated that emergency surgery affected the mortality rate of patients. Merani et al. showed that emergency surgery conducted between 2008 and 2010 had a 14.7% in-hospital mortality rate.12 Khan-Kheil and Khan conducted a study in 2016 and reported that the overall 30-day surgical mortality rate for emergency surgery was 19%.10 In our study, we found that emergency surgery increased the rate of developing postoperative respiratory complications, which were the most frequently detected complications and also prolonged the patients’ hospital stay. Therefore, emergency surgery did have some effects on these geriatric patients, all the way from postoperative respiratory complications and postoperative length of stay to postoperative mortality rates.

There were some limitations in our study. The sample size (404 patients) is relatively small for an observational study. Also, though Chang Gung Memorial Hospital is a relatively large medical center in Taiwan, the majority of patients are still limited near the Taoyuan city and New Taipei City area. Our study data may not represent the entire geriatric population in Taiwan. Multicenter studies with larger patient sample sizes may be required to obtain the whole profile of the relationships between geriatric patients and surgeries. Furthermore, some outcome events are small, such as neurological complications (9 patients, 2.2%), renal complications (5 patients, 1.2%), cardiac complications (2 patients, 0.5%), and shock (2 patients, 0.5%). Due to too few sample cases, we did not proceed with further analyses in cardiac complications and shock on their relationship with preoperative comorbidities and perioperative variables. The 95% CI of odds ratio for neurological complications and renal complications are relatively large due to the same reason.

Another limitation is that the complication and mortality rate estimated in our study included only the in-hospital data. Postoperative conditions may still change after the patients’ discharge. When any complications or emergent situations occur in these patients after their discharge, they might re-enter the hospital for management, for which data will not be available in our database. If these geriatric patients were followed up for a long term after their surgeries by conducting studies for postoperative 30 and 90 days or even 1 year, we could better analyze their outcomes.

In conclusion, our study findings provide a better understanding of surgical geriatric patients. Physicians must focus more on the risk factors that increase postoperative complications and mortality rates whenever they encounter surgical patients with these risk factors preoperatively. Detailed explanations and better communication may also be done more easily with their families to improve the doctor–patient relationship on the whole.

Acknowledgments

The authors thank the statistical assistance and wish to acknowledge the support of the Maintenance Project of the Center for Big Data Analytics and Statistics (Grant CLRPG3D0048) at Chang Gung Memorial Hospital for study design and monitor, data analysis and interpretation.

Disclosure

The authors report no conflicts of interest in this work.


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