Outcome of anesthesia in elective surgical patients with comorbidities.

BACKGROUND: Presence of comorbidity in surgical patients may be associated with adverse perioperative events and increased the risk of morbidity and mortality. This audit was conducted to determine the frequencies of comorbidities in elective surgical patients and the outcome of anesthesia in a Tertiary Hospital in Nigeria.
MATERIALS AND METHODS: Observational study of a cross-section of adult patients scheduled for elective surgery over a 6-month period. A standardized questionnaire was used to document patients' demographics, the presence of comorbidity and type, surgical diagnosis, anesthetic technique, intraoperative adverse events, and outcome of anesthesia. The questionnaire was administered pre- and post-operatively to determine the effects of the comorbidities on the outcome of anesthesia.
RESULTS: One hundred and sixty-five adult patients aged between 18 and 84 years were studied. There were 89 (53.9%) females and 76 (46.1%) males. Forty-five (27.3%) have at least one comorbidity. Hypertension was the most common (48.8%) associated illness. Other comorbidities identified include anemia (17.8%), asthma (8.9%), diabetes mellitus (6.7%), chronic renal disease (6.7%), and others. The perioperative period was uneventful in majority of patients (80.6%) despite the presence of comorbidities. Intraoperative adverse events include hypotension, hypertension, shivering, and vomiting. No mortality was reported.
CONCLUSION: Hypertension was the most common comorbidity in this cohort of patients. The presence of comorbidity did not significantly affect the outcome of anesthesia in elective surgical patients.

Introduction

The presence of comorbidities in surgical patients is significant factors in preoperative morbidity and mortality risk assessment.[12] The current trend in anesthesia practice includes evaluation of risks in order to compare outcomes, control costs, allocate resources, and postpone surgery until interventions improve risk.[134] The aim of this prospective audit was to determine the frequencies of comorbidities in elective surgical patients treated in our institution and its effects on the outcome of anesthesia so as to fill the knowledge gap and identify variables that may require further studies.

Materials and Methods

An observational study of a cross-section of adult patients aged 18 years and above scheduled for elective surgery at our institution between January and June 2013 was carried out. All patients were reviewed preoperatively. The usual routine of treating patients with comorbidities was observed to ensure they were controlled and fit for anesthesia and surgery. There was no cancelation of scheduled surgery. Data on patients’ demography, presence and type of comorbidity, medication and American Society of Anesthesiologists (ASA) status were recorded in a standardized questionnaire. The perioperative clinical information was retrieved from the patients’ medical record. Antihypertensive were continued until the morning of surgery, and diabetic patients were commenced on glucose-potassium-insulin (GKI) infusion on the morning of surgery. However, amlodipine was omitted on the morning of surgery because some authors have reported a significant drop in blood pressure when this antihypertensive is continued until the morning of surgery. Intraoperative and immediate postoperative complications were recorded in a separate data collection form. Patients had different anesthetic techniques administered. However, all patients were monitored using the Dash 4000® multi-parameter monitors (GE Healthcare, United States of America). The monitored parameters include a continuous electrocardiogram, heart rate, noninvasive blood pressure, and arterial oxygen saturation. The outcome variables of interest included high blood pressure (defined as diastolic pressure >110 mmHg or systolic pressure >140 mmHg); hypotension (defined as systolic arterial blood pressure of 80 mmHg or less);[5] occurrence of adverse events such as vomiting, shivering, and others as deemed appropriate. The patients were also follow-up for 24 h postoperative to document any anesthetic related adverse events. The data were analyzed using SPSS version 13 (SPSS Inc, 233 South Wacker Drive, Chicago, United States of America). Results are presented in means ± standard deviation, proportions, and using tables. Fisher's exact test was used to determine the association between the presence of comorbidity and the incidence of adverse events. P ≤ 0.05 was regarded as being significant.

Results

A total of 430 patients had elective surgery during the period; however, data from 165 (38.4%) patients was found to be complete and were analyzed. Poor documentation and incomplete data entries into questionnaires were responsible for the low data retrieval rate. Demographic and clinical characteristics of patients are presented in Table 1. Overall, 45 (27.3%) patients had, at least, one comorbidity while 120 (72.7%) had no comorbidity. Of the 45 patients that have comorbidities, hypertension (48.8%) was the most common comorbidity, the type of comorbidity; the age of the patient and the ASA status are shown in Table 1. Of the 22 patients who were on medication for hypertension, four also had diabetes mellitus in addition. Other documented comorbidity include anemia (17.8%) which were corrected before the elective surgeries, asthma (8.9%) and chronic renal disease (6.7%) as shown in Table 1. There is a preponderance of comorbidity among the male patients and in the middle age group as shown in Table 1 though this was not statistically significant (P = 0.6). Variability in the ASA scoring for the patients was observed as shown in Table 1. Some of the patients who were scored as ASA II or III in the category labeled as “all patients” in Table 1 had no systemic diseases, and the ASA score was based on the severity of the surgical pathologies. Over half (50.9%) of the patients studied had general anesthesia for the surgical procedures while other had spinal anesthesia, combined spinal, and epidural anesthesia or peripheral nerve block as shown in Table 2. The most frequently performed surgery were general surgical procedures (36.4%) followed by orthopedic procedures (18.2%) as shown in Table 2. Of the 120 patients who had no comorbidities, 99 (82.5%) had uneventful anesthesia while adverse events occurred in 17.5% and in patient with one form of comorbidity adverse events occurred in 24.4% as shown in Table 3. Of the 11 patients with comorbidities who had adverse events, 7 (63.6%) have more than one form of comorbidities. There was no significant association between the presence of comorbidity and occurrence of adverse events (P = 0.4). No mortality was recorded in these patients during the 24-h follow-up period.

Table 1

Demographic and clinical characteristics of patients

Variable	All patients (n=165)	Patient with comorbidities (n=45)
Age: Mean±SD	43±18	55±16
Gender: Male:female	76:89	25:20
ASA
I	85	-
II	74	36
III	6	9
Comorbidities		n (%)
Hypertension	-	22 (48.8)
Anemia	-	8 (17.8)
Asthma	-	4 (8.9)
Diabetes mellitus	-	3 (6.7)
Chronic renal disease	-	3 (6.7)
Heart disease	-	2 (4.4)
Others (hemoglobin S [2], seizure disorders [1])	-	3 (6.7)

SD=Standard deviation, ASA=American Society of Anesthesiologists

Table 2

Surgical procedure and anesthetic technique

Variable	Patients without comorbidities (n)	Patients with comorbidities (n)	Total n (%)
Surgical procedure
General surgery	42	18	60 (36.4)
Orthopedics	26	4	30 (18.2)
Gynecological	20	4	24 (14.5)
Neurosurgical	12	2	14 (8.5)
Plastic	10	3	13 (7.9)
Urological	9	10	19 (11.5)
Thoracic	-	4	04 (2.4)
Oral and maxillofacial	1	-	01 (0.6)
Total	120	45	165
Anesthesia technique
General anesthesia	59	25	84 (50.9)
Spinal anesthesia	37	13	50 (30.3)
Combined spinal and epidural anesthesia	13	6	19 (11.5)
Peripheral nerve block	11	1	12 (7.3)

Table 3

Intraoperative adverse events

Parameter	Patients without comorbidities (n)	Patients with comorbidities (n)
None	99	34
Hypertension	1	4
Hypotension	1	5
Tachycardia	4	2
Nausea and vomiting	4	-
Shivering	3	-
Delayed recovery	3	-

Discussion

The frequency of comorbidities associated with surgical pathologies in this study was found to be 27.3% compared to 9.2% from a previous audit from our institution[6] and 19.6% reported by Edomwonyi and Imarengiaye.[7] The reasons for this observation can be attributed to the increasing prevalence of intercurrent illnesses particularly hypertension among adult Nigerians. In a recent review, the pooled prevalence of hypertension in Nigerians was observed to have increased from 8.6% of the 1970–1979 to 22.5% in the period 2000–2011.[8]

Hypertension was the most common comorbidity in this study similar to the previous report from Nigeria,[67] and other authors who observed that uncontrolled hypertension was the most common medical reason for postponing surgery.[9] In this study, there was no cancelation of surgery because patient were well controlled with appropriate medications. In addition, the routine practice in our center was such that elective patients were medically reviewed on an outpatient basis before admission into hospital for elective surgical procedures. In a recent review of hypertension and anesthesia by James and Rayner, it was observed that once treatment is established for hypertension with good response, the perioperative risk is reduced.[10] The goal of preanesthetic review in these patients is to ensure good quality blood pressure control, evaluation of body systems and appropriate investigations such as electrolyte, urea, creatinine, an electrocardiogram to exclude end-organ damage.

In this audit, minor and transient adverse events including hypotension, hypertension, and tachycardia were observed in some of the patients with comorbidities. However, a limitation of this study is the low data retrieval rate, unavailability of the trends in blood pressure and heart rate changes during anesthesia and limited follow-up period. Further studies aiming to study hemodynamic changes during anesthesia for the patient with hypertension is thus required. In the course of anesthetic management of patients with hypertension, the established principle of continuation of antihypertensive medication throughout the perioperative period must be adhered to as was the case in this study. However, some authors have reported incidences of severe postoperative hypotension with use of amlodipine, a commonly prescribed calcium channel blocker antihypertensive agent.[1112] In this study, amlodipine was omitted on the morning of surgery to prevent its undesirable hypotensive effect.

Diabetes mellitus is another comorbidity identified in this study and is not uncommon for diabetes mellitus to be found in association with hypertension as observed in 4 of the patients in this study. Diabetes mellitus present unique challenge to anesthetist because of the metabolic management required to counteract the effects of the stress responses to anesthesia and surgery which are often exaggerated in these patients. In this study, intravenous GKI infusion was commenced on the morning of surgery for diabetic patients including those on oral hypoglycemic agents as well those on insulin to effectively control the perioperative blood sugar level. Perioperative glycemic control was achieved when the GKI infusion was coupled with blood sugar monitoring. The GKI have been reported to be useful in low-resource setting such as Nigeria[13] while some authors have argued that it is laborious as the fresh solution has to be made each time there is a need to adjust the insulin requirement.[14]

Anemia of chronic illness is not uncommon in the surgical patient; in this study anemia was associated with the surgical illness in 8.9% of patients with comorbidities. In a previous study from our institution anemia was very common among our emergency surgical patients though no significant adverse events[15] were recorded similar to the findings in this current study. Some authors have shown that patients with preoperative anemia are at risk of postoperative infection and longer hospital stay.[1617]

We observed that most of the patients with adverse events also had general anesthesia, although this is also the most frequently employed technique of anesthesia. Some authors have recommended the use of regional anesthesia in patients with comorbidity in order to avoid the polypharmacy of general anesthesia.[1819] However, regional anesthesia is not without its complications which include hypotension and possibility of allergic reactions or systemic toxicity of local anesthetic agents.

Conclusion

Hypertension remains the most common comorbidity in our community; the presence of comorbidity did not influence the outcome of anesthesia in this study population. Further studies are required to determine the impact of comorbidity in patients presenting for emergency surgical procedures.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.