Incidence and factors associated with postoperative hemodynamic change in the postanaesthetic care unit among adult surgical patients at a tertiary care hospital in Ethiopia: a prospective observational study

Abstract

Background

Hemodynamic changes are independent risk factors for long-term patient morbidity and duration of hospital stay. According to the statistics, the three most prevalent complications in the postanaesthesia care unit were airway events, haemodynamic instability, and postoperative nausea and vomiting. Hemodynamic instability in the postanaesthesia care unit can result in serious complications, such as long-term patient morbidity and prolonged hospital stays. This study aimed to determine the incidence and factors associated with haemodynamic changes among adult surgical patients in the postanaesthetic care unit.

Methods

An institution-based observational study was conducted from December 1, 2023, to June 30, 2024. In addition, 409 adult surgery patients participated. We employed consecutive sampling techniques and both analytical and descriptive statistics to explain our findings. Using both bivariable and multivariable logistic regression, we evaluated the strength of the association and determined the crude odds ratio and adjusted odds ratio with a 95% confidence interval. A p value of less than 0.05 was considered statistically significant in the multivariable regression.

Results

The incidence of hemodynamic instability was 53.8% (CI: 45%, 64%). The incidences of hypotension, hypertension, tachycardia, and bradycardia were 24.2%, 17.45%, 31.3%, and 12.6%, respectively. ASA class III, procedures with more than 4 instances of intraoperative haemodynamic instability and neuraxial anaesthesia were significantly associated with haemodynamic instability in the postanaesthetic care unit.

Conclusion

In general, 93 study subjects (22.7%) experienced advanced haemodynamic instability during the intraoperative period. This implies that the incidence of hemodynamic instability was high. Intraoperative haemodynamic instability, American Society of Anaesthesiology class III, postoperative respiratory adverse events, neurologic and gynaecological procedures, use of neuraxial anaesthesia, and prolonged duration of procedures were predictors of haemodynamic instability in the postanaesthesia care unit.

Introduction

Background

Approximately 230 million surgeries are performed annually worldwide [1]. Nearly 18% of patients will develop major postoperative complications after surgery [2]. These incidents or postoperative complications, such as airway events, postoperative nausea vomiting, and postoperative hemodynamic instability, are important predictors of functional recovery and long-term survival [3]. Hypovolemia and cardiac dysfunction are the main causes of perioperative complications and poor outcomes [4, 5].

The term “hemodynamic” refers to a physiological process involved in the movement of blood in an artery or vein. For hemodynamic stability to occur, the body must contain enough blood or fluid for the heart to accept and pump, sufficient heart pressure to overcome systemic vascular resistance and pump the blood throughout the body, and a properly functioning pump to pump the blood that has been received [2, 6].

This process may become unstable because of several factors, such as decreased/increased blood pressure and increased/decreased heart rate, and the presence of comorbid illness may lead to inadequate tissue perfusion, organ failure, and possibly death. Hemodynamic instability is an abnormality of the heart, blood vessels, or other organs [5, 7].

According to statistics, the three most prevalent complications in the post anaesthesia care unit (PACU) are airway events, haemodynamic instability, and postoperative nausea and vomiting [8, 9]. Reintubation and intensive care unit (ICU) admission are the most common problems, accounting for 2.1% of significant PACU complications following noncardiac surgery [9]. The prevalence of cardiovascular complications in the postoperative period after a specific vascular procedure was 81% [10].

Overall, 59.47% of cases of haemodynamic instability were reported (CI: 0.55, 0.64). Tachycardia, bradycardia, hypotension, and hypertension occur in 27.34%, 21.82%, 13.67%, and 15.35% of cases, respectively [1]. The incidence of postoperative hemodynamic complications in the postanaesthesia care unit in Ethiopia is 21.1% [11].

Hemodynamic instability in the postanaesthesia care unit can result in serious complications. It is an independent risk factor for long-term patient morbidity and prolonged hospital stays [12].

A study performed in Libya reported comparable occurrence rates of hypertension (12%), hypotension (8%, tachycardia (25%), and bradycardia (1%) [5].

Serious complications might arise in the postanaesthesia care unit due to haemodynamic instability. Hemodynamic instability might be a risk factor for both extended hospital stays and long-term patient morbidity [2]. Compared with those who did not experience severe hemodynamic changes, individuals who experienced severe hemodynamic changes stayed in the postoperative care unit for an additional hour to days. If left untreated, acute postoperative haemodynamic instability can result in heart failure, arrhythmia, myocardial ischaemia, ruptured vascular anastomoses, postoperative haemorrhage, and cerebrovascular accidents [4, 9].

Hemodynamic instability is expressed by changes in blood pressure and heart rate in the postoperative care unit [1]. Hypotension is a common incident in the postanaesthesia care unit. It is more commonly associated with anaesthetic drugs, intraoperative blood loss, or postoperative haemodynamic instability [13, 14].

Hypertension (HTN) and tachycardia in the PACU are associated with an increased risk of admission to critical care units and postoperative mortality [4]. Pain, excitement during anaesthetic reversal, hypoxemia, hypercarbia, and agitation can cause hypertension [15]. In the postanaesthesia care unit, bradycardia is also common. It could, however, be a physiological response to being asleep, young patients, or sportsmen who do not necessarily require therapy [16].

There are several risk factors for postoperative hemodynamic instability. Risks can be patient-, anaesthesia- or surgery-related variables. Age, history of medicinal drugs, ASA physical reputation, and persistent disease are commonly affected person-associated elements. Anaesthetics, different medications, and intraoperative haemodynamic instability are all anaesthesia-associated elements. Intraoperative blood loss, medical professional understanding, operation type, and urgency can also affect the incidence of postoperative hemodynamic instability. Postoperative nausea and vomiting, agitation, respiration-damaging activities, and postoperative pain may also improve haemodynamic instability inside the postanaesthesia care unit [1, 6].

Numerous hemodynamic instability management strategies can be used, depending on the severity and hospital policies. However, by closely monitoring risk factors throughout the perioperative period, hemodynamic instability can be minimized or possibly avoided [6, 12]. Early detection of HDI in the PACU prompts action, which improves the quality of treatment, reduces the PACU stay, lowers overall hospital costs, and hence improves the short- and long-term outcomes of surgery [17].

Other studies have revealed that the specific processes by which postoperative haemodynamic changes influence long-term survival are still unknown. Postoperative hemodynamic instability can occur despite frequent or even continuous intraoperative hemodynamic monitoring. Avoiding this is a physiologically complex challenge for all professionals.

Currently available evidence suggests that a MAP less than 60 mm Hg sustained for 5 min or more is related to organ dysfunction and increased mortality. Interestingly, a recent study revealed that individualized haemodynamic instability intervention reduces systemic inflammatory response syndrome and organ dysfunction after surgery, although its long-term impact on surgical outcomes has not yet been reported.

With this background in mind, the present study aimed to investigate the hemodynamic changes in the PACU and identify risk factors. To the best of our knowledge, published research that can be used as a reference in this country is limited, which makes this study a baseline for further country-wide studies.

Methods and materials

Study design and setting

The study was conducted at Wachemo University Nigist Elleni Mohammed Memorial Comprehensive Specialized Hospital. It is found in regions of southern nations, nationalities and peoples of Ethiopia. Nigest Elleni Mohammed Memorial Comprehensive Specialized Hospital (NEMMCH) is located in Hosanna town, Central Ethiopia region, Hadiya Zone. Hossana town is located 235 km and 181 km south of Addis Ababa city and from Hawassa city, respectively. Nigest Elleni Mohammed Memorial Comprehensive Specialized Hospital (NEMMCSH) is one of the oldest public hospitals in the country. It was established in 1975 G.C. Currently, it is a teaching and referral hospital in the central region of Ethiopia with a bed capacity of 350 beds that is managed by Wachemo University (WCU). Currently, many departments are running teaching and learning activities in hospitals. Teaching and referral hospitals provide services to nearly 3 million people in the catchment area, and approximately 450–500 patients visit hospitals each day. The hospital currently has 350 beds for patient and emergency activities. Similarly, it delivers 24-h emergency operative activities for general surgery and orthopedic procedures and delivers mothers with cesarean section in six separate theatres.

Study design and period

This was an observational study conducted from December 1, 2023, to June 30, 2024. All patients underwent surgery at Nigist Eleni Mohammed Memorial Comprehensive Specialized Hospital (NEMMCSH) from December 1, 2023, to June 30, 2024.

Source and study population

All adult patients aged 18 years and above who underwent both elective and emergency surgery at this study hospital composed the source population, whereas all adult patients aged 18 years and above who underwent surgery in this study area and fulfilled the inclusion criteria during the study period composed the study population.

Eligibility criteria

Inclusion criteria

All adult fit and stable surgical patients who underwent surgery under anaesthesia in the postanaesthesia care unit during the study period were included in the study. Admission to the PACU was based on the federal Ministry of Health Ethiopia PACU protocol.

Exclusion criteria

Patients who were directly admitted to an ICU or ward after an operation.

Patients admitted to the PACU during the course of transfer to the ICU.

Pregnant patients and patients who experienced postoperative shivering were excluded from the study.

Patient with severe pain.

Patients with unstable vital signs while transferring from the operation theatre.

Patients who refused to give consent for inclusion in the study.

Sample size and sampling technique

The sample size was determined by using a single population proportion formula. A study performed in Ethiopia at the University of Gondar on the incidence of haemodynamic events in the postanaesthesia care unit reported that 59% of patients who underwent surgery had haemodynamic instability and was used to determine the sample size of this study [1].

The sample size for this study was calculated by considering the 95% confidence interval, 5% margin of error, and 59% proportion. Population correction was used since the source population was < 10,000. Situational analysis of surgical patients was performed 3 months before the start of the study, and an average of 360 procedures were performed per month.

The sample size was calculated as follows.

$$n=\frac{{Z}_{\frac{\alpha }{2}}^{2}P(1-P)}{{d}^{2}}$$

$$\frac{{\left(1.96\right)}^{2} 0.59\left(0.41\right)}{{\left(0.05\right)}^{2}}$$

$$\mathrm n=372$$

where n: sample size p: proportion d: absolute precision.

When a 10% nonresponse rate was added, the total number of patients included in the study was 409.

Sampling technique

We used a systematic random sampling technique to select the appropriate participant in a sample at a regular interval is selected on the basis of the sampling fraction (K). K = sampling interval, N = total study population and n = sample number.

According to the hospital analysis, 1080 surgical patients were treated within three months.

N = 360, n = 409

K = N/n………..1080/409 = 2.9≈3, the sampling fraction was three, and the first participant was taken by using the lottery method for daily elective patients.

Study variables

Dependent variables

Postoperative hemodynamic changes (HR, BP).

Independent variables

• Patient-related variables

• ASA physical status

• Medications

• Coexisting diseases

• BMI

• Age

• Diagnosis.

• Baseline blood pressure (BP) and heart rate.

Anaesthesia-related variables

Anaesthesia drugs used

Fluid management strategies

Procedure-related variables

Blood loss during surgery

Duration of surgery

Operational definitions

Hemodynamic instability

If a patient has at least one physiological parameter that changes from baseline, including systemic hypertension, hypotension, tachycardia, or bradycardia alone or in combination, then the patient has experienced hemodynamic instability [1, 18].

• 1. Baseline values were measured before induction [19].

• 2. Hypotension: a decrease in mean arterial pressure by 20% from the baseline mean arterial pressure or MAP < 60 mmHg and SAP < 90 mmHg [13, 20].

• 3. Hypertensive: an increase in mean arterial pressure of 20% from the baseline mean arterial pressure or SAP ≥ 140 mmHg [13, 14].

• 4. Tachycardia: Heart rate ≥ 100 for adults [10, 21].

• 5. Bradycardia: Heart rate ≤ 60 for adults [10, 21]

Data collection tools, methods and procedures

A questionnaire was developed after carefully reviewing different literature (Supplementary file), and data were collected by two anaesthetists and three nurses. A chart review was used to collect the data. The questionnaire was prepared to address the preoperative data of patients, such as age, sex, BMI, NPO hour, history of medical illness, and history of medication usage. Blood pressure, heart rate, temperature, and oxygen saturation were recorded during the intraoperative period. Anaesthetic and surgical variables such as the urgency of surgery, duration of surgery, type of anaesthesia, intraoperative estimated blood loss, timing of surgery, intraoperative fluid administered, and intraoperative haemodynamic instability were recorded in the questionnaire. The patient’s hemodynamic status assessment started within the first 15 min of arrival at the PACU.

Data on hemodynamic variables (HR, BP) were collected every 15 min during the first 1 h of the PACU stay and every 30 min during the second hour of the PACU stay as per PACU monitoring standards [20].

Preoperative fasting protocol (Table 1)

Table 1 ASA fasting protocol

Data quality assurance

To ensure the quality of the data, training on the objectives and relevance of the study and brief orientations on the assessment tools were provided for the data collectors. The questionnaires were prepared in English and pretested on 5% of the study population. The Cronbach’s alpha of the pretest was 0.87. During data collection, each question was revised by the investigator to be complete and appropriate. In the event of missed measurements during the intraoperative period, the electronic data stored by the monitoring equipment were recalled and backtraced, and the data were filled.

Data analysis

Epi Data version 4.6 was used to code, edit, clear and enter the data. The data were then exported to the Statistical Package for Social Sciences (SPSS) software version 26 for further analysis. For both ordinal and nominal categorical variables, a stack bar was used to show the distribution of categorical variables, and nominal logistic regression was used for both ordinal and nominal categorical variables. Socio-demographic and related characteristics of the patients and anaesthetic and surgical-related variables were analysed and presented in texts, tables and graphs.

The normality of the distribution of the data was tested via the Shapiro‒Wilk test. Normally distributed data are presented as means and standard deviations, whereas nonnormally distributed data are presented as medians or interquartile ranges. The crude odds ratio (COR) and adjusted odds ratio (AOR) with the corresponding 95% confidence interval were calculated to determine the strength of the factors associated with hemodynamic instability. Model fitness was checked via the Hosmer–Lemeshow test.

Both bivariable and multivariable logistic regression analyses were performed to assess the associations between the dependent and independent variables. Independent variables with p < 0.2 at the 95% CI in the bivariable analysis were transferred to the multivariable binary logistic regression analysis. In multivariable regression, variables with p values < 0.05 were considered statistically significant predictive factors for haemodynamic instability in the postanaesthesia care unit.

Results

Study participant characteristics

Four hundred nine (409) adult surgical patients were involved in this study. The median age (IQR) of the participants was 40 (27–50) years. Among these patients, 62% were male, and 38% were female. The median NPO hour (IQR) of the participants was 10 (8–13) hours. The analysis was performed with 409 respondents, and a response rate of 100% was reached (Fig. 1) (Table 2).

Fig. 1

Patient requirement diagram

Table 2 Demographic characteristics of adult surgical patients in the postanaesthesia care unit, 2024 (N = 409)

Patient-related factors

Among the study patients, 68.9% were ASA I, 23.4% were ASA II, and 7.4% were ASA III. Most patients (63.55%) had preemptive analgesics, whereas 34.98% had received aspiration prophylaxis preoperatively.

This investigation was carried out in a resource-constrained environment. We used non-invasive monitoring for all surgical patients, with intraoperative and postoperative blood pressure monitoring; however, we couldn’t evaluate invasive monitoring due to, limited availability of invasive monitoring an artery catheter for beat-to-beat blood pressure measurement.

Among the patients who underwent abdominal surgeries, 60.8% and 40.2% were elective and emergency procedures, respectively. Among the patients, 65.23% had received general anaesthesia, and 23% had central neuraxial anaesthesia (Table 3).

Table 3 Patient characteristics of adult surgical patients in the postanaesthesia care unit, 2024. (n = 409)

Blood pressure variability during the perioperative period

The baseline median preoperative systolic blood pressure of the patients was 110 (115 ± 20), and the intraoperative median systolic blood pressure of the patients was 100 (110 ± 35). Among these 34 (8.3%) patients who developed intraoperative hypotension, which was SBP < 90 mmHg from baseline, the lowest intraoperative median systolic blood pressure was 80 (85 ± 9), and 17 (4.2%), 27(6.6%) and 15 (3.6%) patients experienced hypertension, tachycardia, and bradycardia intraoperatively, respectively, according to our operational tool.

The surgical patients’ postoperative blood pressure values and heart rate values were as follows: 241 (58.9%) patients had normal median systolic blood pressure values (IQR, 105 (110 ± 9)). Among these patients, 98 (24%) developed postoperative hypotension, with an SBP < 90 mmHg, and 70 (17%) were considered to have hypertension according to our operational tool. A total of 127 (31%) and 49 (12%) patients developed postoperative tachycardia and bradycardia, respectively. In the present study, 151 (37%) patients experienced hemodynamic instability in the PACU, 79 (19.3%) patients underwent elective surgery, and 79 (19.3%) patients underwent emergency surgery.

Anaesthetics and surgical characteristics of patients

During the intraoperative period, 93 study subjects (22.7%) experienced advanced hemodynamic instability, and 18.3% of patients received 2500 ml to 3500 ml of intraoperative fluid. Between 200 and 400 millilitres of blood were lost intraoperatively, and approximately 58.6% of the patient's 303 procedures (72.57%) were carried out during the day. In terms of analgesic or anaesthetic methods, 65% of patients received opioids, whereas 29.57% underwent peripheral or neuraxial blocks (Table 4) (Fig. 2).

Table 4 Anaesthesia and surgery-related factors and percentage of haemodynamic instability among adult surgical patients in the postanesthesia care unit, 2024, (n = 409)

Fig. 2

Hemodynamic instabilities in the PACU among adult surgical patients in the postanesthesia care unit, 2024 (n = 409)

Factors associated with hemodynamic instability in the PACU

Bivariable and multivariable logistic regression analyses were applied to identify the determinant variables of HDI. In the bivariate logistic regression analysis, age, history of past medical illness, ASA class, surgical speciality, urgency of surgery, history of preoperative medication usage, duration of surgery, type of anaesthesia, intraoperative blood loss and fluid management, intraoperative HDI, postoperative nausea and/or vomiting, postoperative pain, postoperative agitation and respiratory adverse events in the PACU were risk factors associated with haemodynamic instability.

In the multivariable logistic regression analysis, ASA classification, type of anaesthesia, surgical speciality, duration of surgery, intraoperative HDI, and postoperative respiratory adverse events were significant factors associated with haemodynamic instability.

ASA class III patients were 3.5 times more likely to develop HDIs in the PACU than were ASA class I patients. Moreover, the odds of developing hemodynamic instability (HDI) in the PACU after neuraxial anaesthesia were three times greater than those of patients who received general anaesthesia.

Our study revealed that gynecologic and neurologic procedures were strongly associated with postoperative HDI. Patients who underwent gynecologic procedures were 2.5 times more likely to develop postoperative hemodynamic instability than those who underwent other procedures were.

Patients who had developed intraoperative HDIs were 4.1 times more likely to experience postoperative HDIs in the PACU than those who did not develop intraoperative HDIs.

Our study also revealed that postoperative respiratory adverse events were associated with HDIs in the PACU. Patients who experienced respiratory adverse events in the PACU were 2.51 times more likely to develop HDIs than those who did not experience respiratory adverse events (Table 5).

Table 5 Bivariate and multivariate logistic regression analyses of factors associated with haemodynamic instability among adult surgical patients in the anaesthesia care unit. 2024

Postoperative factors

Additional postoperative complications were further assessed. A total of 78.24% of patients had mild to moderate pain, whereas 18% of clients experienced postoperative nausea and vomiting. A total of 165 (40.3%) patients experienced agitation. The majority (73.8%) of patients did not experience any respiratory adverse events in the PACU. Approximately 35.81% of the patients were hypothermic inside the PACU, which was mild to moderate hypothermia.

Discussion

In our study, 220 (53.8%) patients developed haemodynamic instability in the postanaesthesia care unit. Approximately 24.2%, 17.45%, 31.3% and 12.6% of patients had experienced hypotension, hypertension, tachycardia and bradycardia, respectively, in the postanaesthesia care unit. This may be related to the low staff-to-patient ratio in the PACU, which makes it more difficult to identify HDIs and stabilize patients early. This is due to the limited resource area. Like in other developing countries, we have a high-patient-flow postanaesthesia care unit (PACU), which makes it difficult to arrange the PACU according to the established protocol. It is often difficult to distinguish critical patients who require close monitoring from stable patients. This leads to a longer stay in the PACU for both stable and unstable surgical patients, and if patients are kept in a high-stress environment such as the PACU, the risk of HDI increases even for stable surgical patients.

Compared with our findings, a study performed in Ethiopia in Gondar revealed a lower incidence of hypertension (12%), hypotension (8%), tachycardia (25%), and bradycardia (1%) [1].

This discrepancy might be attributed to the study setting or period and could be related to the quality of service in the PACU in both settings.

A study conducted in the UK also revealed different incidences of hemodynamic instability, with 58% of the patients experiencing postoperative HDI and 47% experiencing postoperative hypotension [19]. This difference may be attributed to the frequent use of intra-arterial invasive monitoring, which has a better ability to detect hemodynamic instability in the PACU, however, in our study area, due to the limited availability of invasive monitoring an artery catheter we couldn’t evaluate invasive monitoring for beat-to-beat blood pressure measurement.

Intraoperative HDI was found to be significantly associated with hemodynamic instability in the PACU. Patients who experienced intraoperative hemodynamic instability were 4.1 times more likely to develop postoperative hemodynamic instability in the PACU than those who had not experienced intraoperative hemodynamic instability [1, 22].

According to a study conducted in Addis Ababa, Ethiopia, there is a strong association between surgical duration and adverse outcomes in the PACU [11, 15]. This finding was consistent with our research, which indicated that procedures lasting four hours or more are 3.12 times more likely to produce haemodynamic instability than those lasting less than one hour.

Studies conducted in Libya and Iran all agreed that procedures lasting 4 h or longer result in HDIs in the PACU [20, 23]. The present study revealed that patients who underwent gynecologic and neurologic procedures were 2.5 and 2.1 times more likely to have hemodynamic instability in the PACU, respectively. Similarly, a study performed in Canada on perioperative blood pressure management revealed that gynaecological operations were substantial risk factors for postoperative hypotension [24, 25].

A study performed in Egypt revealed that neuraxial anaesthesia was significantly associated with postoperative haemodynamic instability in the PACU [26, 27]. After neuraxial anaesthesia, patients with unstable physiological characteristics are more likely to develop HDIs [21]. Scientifically, patients who receive neuraxial anaesthesia develop temporary hypotension due to peripheral vasodilation [28].

In resource-constrained environments, standardizing the service becomes even more crucial for improving the quality of care. Certainly, it is desirable to adopt risk factor identification tools in surgical patients when the risk of postoperative complications is high, but the staffing and medical resources of a particular clinical setup should be considered. The development of risk factor identification tools is not enough. It can be used as a baseline source to develop evidence-based clinical pathways. The adopted clinical pathway to improve the quality of the postoperative care unit should be implemented and evaluated.

Conclusion

In general, 93 study subjects (22.7%) experienced advanced haemodynamic instability during the intraoperative period. This implies that the incidence of hemodynamic instability is high. The intraoperative HDI, ASA class III, postoperative respiratory adverse events, neurologic and gynaecological procedures, use of neuraxial anaesthesia and prolonged duration of procedures were associated with hemodynamic instability in the postanaesthetic care unit.

Clinicians should be concerned about postoperative hemodynamic instability in the PACU. Close follow-up of vulnerable patients, early detection and intervention of perioperative risk factors for HDI and adherence to the local protocol for patient handover are recommended to decrease the incidence of postoperative haemodynamic instability in the post-anaesthesia care unit.

Strengths and limitations

Our study had several limitations. First, we conducted our study in the resource-limited setting of a single-centre hospital, which makes it difficult to determine the overall features of the country. Second, this study revealed that hemodynamic instability exclusively occurred in the PACU and failed to detect any types of postoperative complications experienced by patients after being discharged from the PACU.Few studies have been conducted on the haemodynamic instability that occurs in the postanesthesia care unit either in our hospital or in the nation at large. Hence, this finding will benefit and alert clinicians that hemodynamic instability in the postanesthesia care unit is still significant. However, we used a noninvasive monitoring apparatus that may not represent the exact readings of hemodynamic parameters.