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Print version ISSN 0034-7094On-line version ISSN 1806-907X
Rev. Bras. Anestesiol. vol.54 no.4 Campinas July/Aug. 2004
Silent myocardial ischaemia in patients undergoing transurethral resection of prostate - comparison of spinal versus epidural anaesthesia*
Isquemia miocárdica silenciosa en pacientes sometidos a prostatectomia transuretral - comparación entre anestesia subaracnóidea y peridural
Parshotam Lal Gautam, M.D.I; Sunil Katyal, M.D.I; Gurpreet Singh Wander, M.D.II; Harpreet Kaur, M.D.III
IReader, Dept. of Anaesthesia
IIProfessor, Dept. of Cardiology
IIIPG Student, Dept. of Anaesthesia
BACKGROUND AND OBJECTIVES:
In the recent past, silent myocardial ischaemia has been found to be associated
with increased perioperative cardiac morbidity and mortality. As many as 41
% of patients with either known coronary artery disease or with cardiac risk
factors, undergoing a non-cardiac surgery, develop perioperative ischaemia.
Various authors have compared regional techniques with general Anaesthesia in
selected groups but no one has compared the impact of different techniques of
centroneuraxial block on incidence and duration of silent myocardial ischaemia.
Thus we compared two different techniques of centroneuraxial block (Spinal versus
Epidural block) in aged patients selected randomly undergoing TURP surgery.
We took TURP patients as they belong to geriatric age group and often have silent
or apparent coexistent coronary artery disease. Secondly, TURP surgery related
volume overload and shivering in these patients lead to further oxygen demand
METHODS: Forty patients undergoing transurethral resection of prostate were monitored for perioperative silent myocardial ischaemia with the aid of a Holder device. Holter monitoring was started 1 hour prior to surgery and then continued during and after surgery the for next 24 hours. Holter data was analyzed using DSM model 300.
RESULTS: The overall incidence of silent myocardial ischaemia in our study was 30%. No relationship could be established between silent myocardial ischaemia and type of centroneuraxial block. Most of the episodes of myocardial ischaemia occurred in preoperative period and, these had no correlation with hemodynamic fluctuations. However the incidence and load of silent myocardial ischaemia was higher in-patients with high Detsky scoring, hypertension and anaemia. None of the patient had any adverse cardiac outcome.
CONCLUSIONS: Type of centroneuraxial block has no effect on incidence of silent myocardial ischaemia.
Key Words: ANESTHETIC TECHNIQUES, Regional: epidural, spinal block; DISEASES: myocardial ischaemia; SURGERY: tansurethral resection prostate
JUSTIFICATIVA Y OBJETIVOS: La
isquemia miocárdica silenciosa fue recientemente relacionada al aumento
de morbi-mortalidad cardíaca peri-operatoria. Hasta 41% de los pacientes
con enfermedad coronariana conocida o con factores de riesgo cardíaco,
sometidos a cirurgías no cardíacas, presentan isquemia peri-operatoria.
Varios autores compararon las técnicas de anestesia regional y general,
más ninguno comparó el impacto de diferentes técnicas de anestesia
del neuro-eixo en la incidencia y duración de la isquemia miocárdica
silenciosa. El objetivo de este estudio fue la de comparar dos técnicas
diferentes de anestesia en el neuro-eixo (subaracnóideo versus. peridural)
en pacientes edosos aleatoriamente seleccionados y sometidos a prostatectomia
transuretral. Optaou-se por pacientes idosos por frecuentemente presenta enfermedad
coronariana silenciosa o aparente. Outro factor importante que influenció
la escoja, fue la sobrecarga de volumen y tremores causados por prostatectomia
transuretral en esos pacientes promovendo desequilibrio entre el consumo y oferta
MÉTODO: Participaron de este estudio 40 pacientes sometidos a prostatectomia, fueron estudiados en relación a la isquemia miocárdica silenciosa con la ayuda de un equipamiento Holter. La monitorización se inició 1 hora antes de la cirugía y prosiguió durante la misma y después por las próximas 24 horas. Los datos del Holter fueron analizados por un DSM modelo 300.
RESULTADOS: La incidencia general de isquemia miocárdica silenciosa en este estudio fue de 30%. No fue establecida ninguna relación entre isquemia miocárdica silenciosa y tipo de anestesia. La mayor parte de los episodios de isquemia miocárdica ocurrió en el período pre-operatorio y no tuvieron relación con alteraciones hemodinámicas. No obstante, la incidencia y la gravidad de isquemia miocárdica silenciosa fue más alta en pacientes con altos contajes de Detsky, hipertensión arterial y anemia. Ningún paciente presentó efectos cardíacos adversos.
CONCLUSIONES: El tipo de anestesia no influenció la incidencia de isquemia miocárdica silenciosa.
Adverse cardiac events are a major cause of morbidity and mortality after non-cardiac surgery in geriatric patients. Many authors have studied the perioperative risk factors and scoring systems to assess the populations at risk. In the recent past, silent myocardial ischaemia has been found to be associated with increased perioperative cardiac morbidity and mortality1. As many as 41% of patients with either known coronary artery disease or with cardiac risk factors, undergoing a non- cardiac surgery, develop perioperative ischaemia1-4. In addition to the preoperative cardiac risk factors, type of anaesthesia, hemodynamic fluctuations and surgical stress have their impact in causing myocardial oxygen demand supply mismatch and cardiac morbidity in these patients.
Most of the authors have compared regional techniques with general anaesthesia in selected group of patients suffering from coronary artery disease for silent myocardial ischaemia5,6. None of the author has compared the impact of type of regional block on the occurance of silent myocardial ischaemia. Patients undergoing transurethral resection of prostate (TURP) surgery have been reported to experience high incidence of myocardial ischaemia. This is probably due to geriatric age group and coexistent coronary artery disease in these patients. Secondly, TURP surgery related volume overload and shivering in these patients lead to further oxygen demand supply mismatch. Thus, we proposed to compare two different techniques of centroneuraxial block in randomly selected aged patients undergoing TURP surgery. Knowledge of perioperative myocardial ischaemia in these patients undergoing a routine surgery like TURP might help to estimate the medical and economic implication of preventive strategies. We used Holter monitoring starting from preoperative period and extending post operatively for 24 hours.
Forty male patients (age > 50 years) undergoing elective TURP surgery under centroneuroaxial anaesthesia were prospectively studied for perioperative myocardial ischaemia using ambulatory ECG for 24 hours. After approval by hospital ethics committee, a written informed consent was obtained from all patients. Patients were randomly allocated into two groups of 20 each on the basis of anaesthetic technique:
Group I patients received centroneuraxial block by subarachnoid block with 2 mL heavy 0.5% bupivacaine;
Group II patients received centroneuraxial block by epidural block using 15 mL of lidocaine 1.5%.
A through preanesthetic checkup was conducted to evaluate the patients for coronary artery disease and other associated risk factors. Routine investigations like haemogram, urine examination, fasting blood sugar, serum urea; serum creatinine; serum electrolytes, X-ray chest and ECG were done in all patients and recorded. Detsky scoring was done to stratify cardiac risk.
Patients with preoperative interventricular conduction block, left ventricular strain pattern, resting abnormal ST segment in ECG and on digoxin therapy were not included in the study. Patients who had either any contraindication to or refused the method, as well as those with inadequate or failed regional block were also excluded from the study. All patients were premedicated with tablet diazepam 10 mg a night before and 5 mg on the morning of surgery with a sip of water.
Patients were kept fasting for 6 hours prior to surgery. Morning doses of antihypertensive and antianginal drugs were continued with a sip of water, if any three leads Holter monitoring was started preoperatively on the morning of surgery and was continued perioperatively for a total period of 24 hours. After shifting the patients on operation table, intravenous catheter was inserted in the veins on the dorsum of hand and connected to free running saline infusion. Heart rate, non-invasive blood pressure, ECG and oxygen saturation were monitored continuously intraoperatively.
Group I patients received subarachnoid block with 23G L.P. needle in sitting position at L2-L3 or L3-L4 intervertebral spaces with 2 mL heavy 0.5% bupivacaine injection. Patients were made to lie supine and levels of maximum sensory block and duration were recorded. Group II patients received epidural block with 16G Touhy's needle using loss of resistance technique at L2-L3 or L3-L4 intervertebral spaces. Epidural catheter was placed in epidural space. Lidocaine 1.5%, 15 mL was injected as a bolus after a test dose of 3 mL through epidural catheter. Epidural catheter was secured and patients were placed in supine positions. Maximum level and duration of sensory block were recorded. Incremental dose of lidocaine 1.5% 3 mL was administered in case of inadequate effect and top up of 6 mL was repeated as and when required.
Intraoperative complications like hypotension (systolic blood pressure < 90) were treated with intermittent mephenteramine 3 mg I.V. injection and bradycardia with atropine 0.6 mg I.V injection. After completion of surgery, patients were referred to recovery room. After 24 hours, record of events on Holter monitoring was obtained and analyzed. Perioperative cardiac events, like episodes of hypotension, arrhythmia, chest paint etc. were recorded. Weaning of sensory block was monitored and recorded. Parameters recorded on Holter monitoring were observed and analyzed using DSM model 300. ST segment depression greater than 1mm were considered as significant silent myocardial ischaemia. Statistical analysis was performed using Student's t test, Z-test i.e. test of proportions and multivariate logistic regression analysis.
Demographic data and clinical profile were comparable among two groups as shown (Table I). There was no significant difference in the incidence of cardiovascular risk factors in both the groups (p value, < 0.10). Duration of sensory block and resection times were also similar in both the groups.
In most of the cases, resection time was approximately 20 minutes, except for four patients (two in each group), where resection time crossed one hour. Out of these four patients, one patient of Group I had silent myocardial ischaemia. There was no significant difference in incidence of myocardial ischaemic episodes in both the groups. Twelve patients (30%) with six in each group (Table II), were found to have silent myocardial ischaemia. The ischaemic load in group I varied from 3 minutes to 470 minutes, with mean duration of 84 minutes, and in group II varied from 20 minutes to 479 minutes, with mean duration of 201 minutes. Mean ischaemic load was observed to be higher in group II.
It was also observed that most of myocardial silent ischaemic episodes occurred in preoperative period (i.e. 5 out of 6 in group I and 4 out of 6 in-group II). Postoperative silent ischaemia occurred in one patient in spinal group and two patients in epidural group. One patient had ST segment depression on Holter monitoring as late as 18 hours after surgery in study group II. That patient had the highest Detsky score. Also, high Detsky scores were found to be associated with longer silent ischaemic episodes. Most of the patients with silent myocardial ischaemic changes were found to have concomitant hypertension (i.e. 4 out of 6 in each group or 66.66%) Diabetes mellitus was seen to be poorly related with perioperative silent myocardial ischaemia. Intraoperative changes in the heart rate and blood pressure were also not significantly linked with episodes of ST depression. Patients with silent ischaemia were analysed using multivariate analysis for significance of various factors i.e. age, arterial hypertension, diabetes mellitus, lipid profile, Detsky score, anaemia, resection time, beta-blocker treatment and smoking. From this analysis, it was found that in patients showing ST depression in group I, anaemia followed by hypertension were the most significant factors (Table III, p < 0.05).
In patients showing silent ischaemia in group II, Detsky scoring (p < 0.01) followed by anaemia (p < 0.05) and arterial hypertension (p < 0.05) were found to be statistically significant.
Rest of the factors was observed to be non-significant in both groups.
The interest in the monitoring for perioperative myocardial ischaemia reflects the possibility of using this as a predictor of adverse cardiac outcomes such as myocardial infarction, heart failure or cardiovascular death in early postoperative period or as a long-term prognostic indicator. A number of risk factors have been identified to stratify risk in selected population groups undergoing mainly major vascular surgeries. However, as hard adverse reaction are rare in routine general surgeries, those results of major vascular surgeries can not be applied to patients undergoing non-vascular surgeries. Detection of silent myocardial ischaemia in these population groups selected at random may help to identify the patient at risk of developing subclinical myocardial ischaemia. In general surgical population, number of authors have found relationship between silent myocardial ischaemia and adverse cardiovascular complications and their outcome1-3. Various modalities have been used in different studies to detect early silent myocardial ischaemia.
These include ECG7, Holter monitoring1,6,8-10, cardiac enzyme levels like Troponin I and T, CPK MB11-13, pulmonary artery catheter14, transesophageal echocardiography15 and myocardial electrical impedance monitor16.
In our study, we studied perioperative silent myocardial ischaemia in geriatric population selected randomly undergoing TURP surgery under two types of centroneuraxial block using Holter ambulatory ECG we found an overall silent ischaemia incidence of 30%. None of the patient had any major untoward event. The incidence of postoperative adverse cardiac events following perioperative ischaemia has been found to be related to silent ischaemia in various studies. Different authors have reported incidence varying between 18%-60% after regional anaesthetic techniques in previous studies. Mangano et al1 in 1990 and Windsor et al6 in 1996 compared two anaesthetic techniques (spinal and general anaesthesia) for incidence of silent myocardial ischaemia and demonstrated no significant difference between them. In our study, we compared two regional anaesthetic techniques: spinal and epidural Anaesthesia. The incidence of silent myocardial ischaemia was similar in both groups. No significant correlation could be established between the hemodynamic fluctuations and silent myocardial ischaemia. Duration and level of blockade were also comparable between the two study groups. The average duration of block was 1½ hours and average level up to T10 with maximum level up to T8.
In most of the studies researchers have found silent myocardial ischaemia in the postoperative period which coincided with the cessation of sympathetic block. The shifting of fluids in the central compartment, changes in adrenergic activity, plasma cholinesterase levels, body temperature, shivering, pulmonary function and perception of pain are found to be the contributing factors1,8. Contrary to these authors, we found that silent myocardial ischaemia occurred more often in preoperative period in our patients. This could be due to preoperative anxiety because of inadequate premedication as per our protocol. We found that most of our patients were wide-awake while being wheeled in the operation theatre.
In our study, we also studied various risk factors associated with silent myocardial ischaemia. These included age, diabetes mellitus, arterial hypertension, lipid profile, Detsky score, anaemia, resection time, beta-blocker therapy and smoking. Out of these, anaemia and arterial hypertension were found to be most significant in group I patients while Detsky score followed by anaemia and arterial hypertension were found to be most significant in group II patients.
As it is established that perioperative myocardial ischaemia is a product of oxygen demand supply mismatch, probably patient with anaemia and hypertension failed to maintain adequate myocardial oxygen supply in stressful perioperative conditions. In our study, patients in both study groups showed significant variations in heart rate as well as in mean arterial pressure in early postoperative period, with higher values of these in patients under epidural anaesthesia. However, no statistical significance was found. However, to elucidate conclusively whether haemodynamic drifts have poor correlation with myocardial ischaemia and role of various contributing factors, a substantially large planned study is required.
In summary, we conclude that the geriatric patients with or without evident coronary artery disease had overall incidence of silent myocardial ischaemia in range of 30%. The type of regional Anaesthesia (spinal or epidural) did not influence the incidence or load of silent myocardial ischaemia. Most of the ischaemic events were found to occur preoperatively. Secondly, whether these short episodes of silent ischaemia have been significant in the prognostic prediction needs further longitudinal supervised trials. Merely the presence of myocardial ischaemic episodes have questionable role to cause significant cardiac morbidity as reported earlier by Windsor et al. Various risk factors for perioperative ischaemia include high Detsky score, hypertension and anaemia.
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Parshotam Lal Gautam, M.D.
Address: 61 Ashok Vihar, Rishi Nagar
Submitted for publication August
Accepted for publication December 4, 2004
* Received from do Departamento de Anestesiologia do Dayanand Medical College & Hospital, Ludhiana, Punjab, India