Pre-operative evaluation for diabetic cardiac autonomic neuropathy and their behavior during regional anesthesia

Abstract

INTRODUCTION: Cardiovascular autonomic neuropathy (CAN), a common form of autonomic dysfunction found in patients with diabetes mellitus, causes abnormalities in heart rate control, as well as defects in central and peripheral vascular dynamics. Individuals with parasympathetic dysfunction have a high resting heart rate most likely because of vagal neuropathy that results in unopposed increased sympathetic outflow. Persons with a combined parasympathetic/sympathetic dysfunction have slower heart rates. With advanced nerve dysfunction, heart rate is fixed. Thus, it is apparent that the determination of heart rate itself is not a reliable diagnostic sign of CAN. Reduction in variability of heart rate is the earliest indicator of CAN. Cardiovascular autonomic neuropathy occurs in ~17% of patients with type 1 diabetes and 22% of those with type 2. An additional 9% of type 1 patients and 12% of type 2 patients have borderline dysfunction. In a review of several epidemiological studies among individuals with diabetes, the 5-year mortality rate is five times higher for individuals with cardiovascular autonomic neuropathy than for individuals without cardiovascular autonomic involvement. The autonomic nervous system, which includes the parasympathetic and sympathetic systems, plays an important role in the regulation of myocardial function, heart rate, and myocardial blood flow. The sympathetic system innervates the myocardium via sympathetic nerve fibers that traverse the subendocardium along the path of the coronary vessels, from the base to the apex of the heart. Extended increased stimulation of cardiac adrenergic receptors results in desensitization and downregulation of the receptors, as well as increased receptor degradation and decreased receptor synthesis. In diabetes, CAN is ultimately the result of complex interactions among degree of glycemic control, disease duration, age-related neuronal attrition, and systolic and diastolic blood pressure. Hyperglycemia plays the key role in the activation of various biochemical pathways related to the metabolic and/or redox state of the cell, which, in concert with impaired nerve perfusion, contribute to the development and progression of diabetic neuropathies. Experimental data implicate a number of pathogenic pathways that may impact autonomic neuronal function in diabetes including: formation of advanced glycation end products, increased oxidative/nitrosative stress with increased free radical production, activation of the polyol and protein kinase C pathways, activation of poly ADP ribosylation, and activation of genes involved in neuronal damage. AIM OF THE STUDY: This study aimed on Pre-operative evaluation for diabetic autonomic neuropathy using CANS 504 (cardiac autonomic neuropathy system analyzer) and their behavior during regional anesthesia. Inclusion criteria: Case: 1. Age: 40- 60 years, 2. Sex: both male and female, 3. Diabetes mellitus > 3 years, 4. PS II & III. Control: 1. Age: 40- 60 years, 2. Sex: both male and female, 3. Not a known diabetes mellitus, 4. PS I Exclusion criteria: 1. age 60 years, 2. PS IV. Equipments required: 1. CANS 504 – cardiac autonomic neuropathy system analyzer, 2. ECG monitor, 3. Sphygmomanometer, 4. pulse oxymeter. METHODOLOGY: A randomized controlled, prospective comparative study was done to compare the behavior of diabetic patient with cardiac autonomic neuropathy and non-diabetic patient without cardiac autonomic neuropathy during spinal anesthesia. The study was conducted after approval by the hospital ethical committee and an informed written consent was obtained from all. The sympathetic nervous system is stimulated in the early stages of diabetes and extended exposure of the adrenergic receptors to increased cathecalomines level together with hyperglycemic and insulin deficiency is believed to cause diabetic CAN. An imbalance of sympathetic and parasympathetic control of cardiac function can lead to silent myocardial ischemia, sudden cardiac death due to lethal arrhythmias, orthostatic hypotension, resting tachycardia, decreased baroreceptor sensitivity, exercise intolerance diastolic dysfunction and B.P invariability (sztajzel, 2004). There is a 2-3 fold increase in cardiovascular morbidity and mortality intra-operatively for patient with diabetes. Noninvasive diagnostic methods assessing autonomic function allow identification of at risk patient pre-operatively and better prepare the anesthesiologist for potential hemodynamics. This study aimed to evaluate the diabetic patient and control group pre-operatively for cardiac autonomic neuropathy with CANS – 504 (cardiac autonomic neuropathy system analyzer). A total number of 50 ASA II & III patients belonging to age group of 40 –60 years were divide into three groups 20 ,10, 20 respectively. Group I – patients with diabetic mellitus having cardiac autonomic neuropathy, group II –diabetic patient without cardiac autonomic neuropathy and group III –control patients non-diabetic without cardiac autonomic neuropathy. Those patients 60 years & those of ASA IV were excluded from the study. Both male and females with diabetes mellitus more than 3 years are included in the case study. Along with routine investigations, pre operative evaluation for cardiac autonomic neuropathy is done with CANS 504 (cardiac autonomic neuropathy system analyzer). CANS 504 is an important tool to measure and diagnose autonomic dysfunction using ECG R-R interval and automatic B.P measurement. Understanding controls: 1. 3 lead ECG, 2. B.P cuff, 3. valsalva probe, 4. spring loaded hand grip device. RESULTS: In group I, during spinal anesthesia, the fall in B.P was more frequent (75%) and they need more doses of inj. Ephedrine (42%) and 33 % patient in group I are non reactive to inj. Ephedrine and they need inotropic support for B.P stability. 5 patients in group I have abnormal results i.e grade II in all five test of autonomic function study. Those five patients were non responsive to inj. ephedrine during hypotensive reactions .They need inotropic support for hemodynamic stability. The occurrence of bradycardia (50%) during hypotensive reaction is also frequent and need atropine (40%).In group II ,fall in B.P was frequent (40%) but less than group I and more frequent than group III. In group III fall in B.P was less frequent (18%) and need less doses of inj. Ephedrine (15%). Fall in B.P can be managed even with i.v fluids in most cases .hypotensive reactions are less frequently accompanied with bradycardia (10%). From the ANOVA and POST HOC test we can find a significant difference in systolic and diastolic B.P between group I and GROUP III. But there was less significant difference in B.P between group I and group II ,group II and group III. From ANOVA we find significant difference in pulse rate between group I, II, III at various time interval during intra – operatively. CONCLUSION: 1. We found a significant correlation between degree of autonomic dysfunction and largest drop in B.P variability in heart rate and rhythm. 2. These results prove atypical hemodynamic behavior and extreme B.P instability in diabetes patients with cardiac autonomic neuropathy. 3. Therefore we consider it to be very helpful to check the cardiovascular reflectory status of diabetes patient pre-operatively ,so that we can anticipate the risk during anesthesia in such patients.