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Year : 2016 | Volume : 4 | Issue : 2 | Page : 106 - 110  


Original Articles
Study of autonomic functions in normal pregnancy and preeclamptic pregnancy

Dhanasree Naidu VS1, Sandhya Manohar W 2, Sudhir Reddy P 3, Anudeepti Neelagiri4, Sai Sankalp Naidu VS5

1Professor of Physiology, Malla Reddy Institute of Medical Sciences, Hyderabad,

2AssociateProfessor of Forensic Medicine, Kamineni Institute of Medical Sciences, Narketpalli, Nalgonda Dist.,3, 4 & 5 PG Scholars

Corresponding Author:

Dr. Dhanasree Naidu VS

Email: drvsdnaidu@yahoo.co.in

Abstract:

Background: After due analysis World Health Organisation (WHO) has determined that hypertensive disorders in pregnancies are the major cause of mortality. In spite of its prevalence and severity, no comprehensive theory or single factor has been suggested to explain the pathophysiology of this multi system disorder of pregnancy, with the only therapies being bad rest, pharmacological symptomatic management and if necessary early delivery.

Objective: To Study autonomic functions in normal pregnancy and preeclamptic pregnancy

Methods: The present study was carried out in the department of Physiology, Obstetrics & Gynaecology outpatient department (OPD) & ward. The study design is cross-sectional study conducted on two groups of subjects. Thus the total no of 100 subjects were included in the study. A detailed recording of medical, obstetric, personal and family history and clinical examination of the subjects was carried out and the subjects who met the criteria were accordingly selected for the study. The consent of subjects was taken before doing clinical examinations.

Results: The systolic blood pressure of Group - I and Group - II was noted as 131.9 and 154.8 respectively and is found to be extremely significant. The diastolic Blood Pressure of Group – I, was recorded as 70.72 and Group - II was recorded as 100.4 and the P value was found as extremely significant.

Conclusion: The normal pregnant (group - I), has significantly lower diastolic pressure and mean arterial pressure, significantly higher resting heart rate. Rise in SBP & DBP, to cold stimuli and handgrip is significantly increased in preeclamptic pregnant (group - II).

Key words: Autonomic functions, pregnancy, preeclampsia

INTRODUCTION:

After due analysis World Health Organisation (WHO) has determined that hypertensive disorders in pregnancies are the major cause of mortality. In spite of its prevalence and severity, no comprehensive theory or single factor has been suggested to explain the pathophysiology of this multi system disorder of pregnancy, with the only therapies being bad rest, pharmacological symptomatic management and if necessary early delivery. (1) Many studies on the pathophysiologic mechanisms of this disorder described that preeclampsia is characterised by low circulating volume and high vascular resistance. This is exactly opposite of the hemodynamic changes that occur in normal pregnancy i.e. decrease in mean arterial pressure and systemic vascular resistance and marked increase in circulating volume, heart rate and cardiac output (2).

It has been proposed that autonomic nervous system bring about these hemodynamic changes, but the exact role of autonomic control mechanism in pregnancy is poorly understood (3). Cardio vascular adaptions during pregnancy are triggered by decrease in systemic vascular resistance, which in turn results into a feedback response of increase in cardiovascular sympathetic drive to meet the higher circulatory demands of pregnancy. In short the marked increase in sympathetic activity in later months of pregnancy help to return the arterial pressure to non-pregnant levels, but when there is excessive increase in sympathetic activity, hypertension develops (4). In particular the studies by Hans P. Schobel (1) indicate that the increase in peripheral vascular resistance and blood pressure seen in preeclampsia, was mediated by substantial increase in sympathetic vasoconstrictor activity. A high cardiac output was observed early in pregnant woman developing preeclampsia compared to those who remained healthy throughout their pregnancy. The hemodynamic alterations occur in normal pregnancy and these alterations are impaired in preeclampticpregnancy resulting into a definite risk to the foetal wellbeing. It may also result in dysfunction of various organs in the mother i.e. kidneys, central nervous system and heart. The autonomic nervous system plays an important role on adopting the circulation to these alterations. As the autonomic nervous system also has an important adaptive influence on the circulation, it has been decided to evaluate autonomic nervous function in preeclampsia, using standard non-invasive and cardiovascular reflex test i.e. cold pressure test and standard handgrip test for evaluation of sympathetic activity whereas standard ratio, standing to lying ratio, deep breathing ratio and Valsalva ratio for parasympathetic activity (4) and these non-invasive methods does have the advantage of minimal risk for the mother and foetus and repeated measurements can be possible in case of any error in values during the procedure (2). Present study was undertaken to assess the sympathetic function by cold pressure test in normal pregnant and preeclamptic pregnant women and compare the values among them.

MATERIAL AND METHODS

The present was carried out in the department of Physiology, Obstetrics & Gynaecology outpatient department (OPD) & ward. The study design is cross-sectional study conducted on two groups of subjects:

Group I - Normotensive pregnant women (n = 50)

Group II - Preeclamptic pregnant women (n = 50)

Thus the total no of 100 subjects were included in the study. A detailed recording of medical, obstetric, personal and family history and clinical examination of the subjects was carried out and the subjects who met the criteria were accordingly selected for the study. The consent of subjects was taken before doing clinical examinations.

Preeclamptic pregnant women (Group II): Diagnosed cases of preeclamptic pregnant women (n = 50) in third trimester of pregnancy in the age group of 18 to 30 years, visiting Obstetrics & Gynaecology, antenatal clinic at the OPD were selected for study. Preeclampsia defined as pregnancy - specific disorder occurring after 20 weeks of gestation characterised by blood pressure of 140/90 mmHg or higher and proteinuria of at least 03g per 24 hours in a previously normotensive and non proteineuria patient (5). All subjects selected were primigravida with no other complication of pregnancy.

Normal normotensive pregnant woman (Group I): A group of normal normotensive pregnant women (n = 50) in third trimester of gestation, all primigravida belonging to the same age group. (18-30 years), with similar height, built, dietary habits and ethnicity as the above were selected.

Exclusion criteria:

  1. Subjects other than age group of 18-30 years
  2. Diagnosed cases of or women with symptoms suggestive of essential hypertension, hypotension, diabetes mellitus, chronic renal failure, liver disease, cardiovascular disease, thyrotoxicosis, obesity, familial hyperlipodemia or dyslipidemia and idiopathic epilepsy & vascular disease.
  3. In case of pregnant subjects in Group I & Group II, multigravida, those < 28 weeks of gestation, multiple pregnancy (twins), known cases of intrauterine growth retardation and eclampsia.
  4. Subjects suffering from any other diseases likely to affect autonomic nervous system (ANS) like hyperthyroidism, multiple myeloma, and amyloidosis.
  5. The exclusion criteria does exclude the subjects with habits of smoking, alcohol and drug abuse.
  6. These exclusion criteria was applied for both groups, in order to exclude direct and indirect effects of the above mentioned factors on the parameters assessed.

Procedure:

Subjects were asked to refrain from ingesting beverages containing caffeine and alcohol and not to exercise during 24 hours preceding each test. The subjects were asked to report in the department. Anthropometric parameters and recordings of different cardiovascular tests were taken in the morning hours between the breakfast and recording observations (6).

Before starting the tests, details of proceedings and need of history was described to each subject so that the subject is in the state of calmness without anxiety and cooperates at the time of the tests. Written consent was taken from each subject and rested 10-15 minutes in quiet room to ensure full relaxation before starting the tests.

Baseline ECG, Heart Rate, Systolic and Diastolic blood pressure (SBP & DBP) of all the subjects were recorded. Then the autonomic function tests were conducted to evaluate the integrity of both sympathetic and parasympathetic innervation of heart i.e. integrity of entire autonomic reflex arc in both the groups (7).

RESULTS

There was no significant difference in the mean age, the weights, BMI and gestational age of Group I and Group II

Table 1: Comparison of blood pressure of the pregnant subjects

 

Group I

Normal pregnant women

Group II

Preeclamptic pregnant women

Group I

vs

Group II

Systolic blood pressure

(mm Hg)

131.9 +7.655

154.8 + 4.675

p>0.001

ES

Diastolic blood pressure

(mm Hg)

70.72 +6.058

100.4 + 9.510

p>0.001

ES

Mean arterial pressure

(mm Hg)

85.12 +4.392

118.8 + 6.410

p>0.001

ES

Both Group I and Group II has shown extremely significant (ES) difference of p>0.001 in Systolic blood pressure, Diastolic blood pressure and Mean arterial pressure.

Table 2: Comparison of Resting Heart Rate the pregnant subjects

 

Group I

Normal pregnant women

Group II

Preeclamptic pregnant women

Group I

vs

Group II

Resting Heart Rate

(mm Hg)

87.3 + 14.01

91.3 + 5.79

p>0.05

NS

Both Group I and Group II has not shown any significant (NS) difference i.e. p>0.001 in Hear Beat Rate.

Table 3: Comparison of the Sympathetic Function of the subjects in both groups

Response to Sympathetic Function Tests

Group I

Normal pregnant women

Group II

Preeclamptic pregnant women

Group I

Vs

Group II

Increase in SBP

during CBT

(mm Hg)

13.52 + 4.908

15.92 + 5.450

p>0.05

S

Increase in DBP

during CPT

(mm Hg)

9.040 + 3.574

10.96 + 3.923

p>0.05

S

Increase in SBP

during HG

(mm Hg)

13.4 + 4.005

14.96 + 4.106

p>0.05

NS

Increase in DBP

during HG

(mm Hg)

11.68 + 3.733

13.96 + 4.703

p>0.05

S

The table shows significant increase in both SBP and DBP during Cold Pressure Test (CPT). During Hand Grip Test SBP has not shown any significant increase, whereas DBP has shown significant increase.

Table 4: Comparison of Parasympathetic Function of the subjects in both groups

Response to Parasympathetic Function Tests

Group I

Normal pregnant women

Group II

Preeclamptic pregnant women

Group I

Vs

Group II

30/15 ratio

1.206 + 0.157

1.110 + 0.133

p>0.01

VS

S/L ratio

0.948 + 0.184

0.862 + 0.154

p>0.01

VS

E/I ratio

1.263 + 0.114

1.211 + 0.111

p>0.05

S

Valsalva

1.533 + 0.1969

1.479 + 0.1180

p>0.05

NS

30/15 ratio and S/L ratio of Group I and Group II has shown very significant p>0.01 (VS). E/I ratio has shown significant whereas Valsalva has shown no significance.

Table 5: Correlation of rise of SBP & DBP during CPT with results of Parasympathetic Function Tests in Preeclampsia

 

Correlation of rise of SBP during CPT

30/15 ratio

S/L ratio

E/I ratio

Valsalva Ratio

Person’s Correction Coefficient (r)

-0.1198

-0.0099

-0.1173

-0.0490

P value

0.4073 - NS

0.9451 - NS

0.4174 - NS

0.7351 - NS

 

 

Correlation of rise of DBP during CPT

30/15 ratio

S/L ratio

E/I ratio

Valsalva Ratio

Person’s Correction Coefficient (r)

-0.1198

-0.0099

-0.1173

-0.0490

P value

0.4073 - NS

0.9451 - NS

0.4174 - NS

0.7351 - NS

There is a rise in correlation of all the parameters - 30/15 ratio, S/L ratio, E/I ratio and Valsalva Ratio in the Group II. However, all the P values of correlation were found to be not significant.

Table 6: Correlation of rise of SBP & DBP during Hg with results of Parasympathetic Function Test in Preeclampsia

 

Correlation of rise of SBP during HG

30/15 ratio

S/L ratio

E/I ratio

Valsalva Ratio

Person’s Correction Coefficient (r)

-0.1401

-0.0446

-0.0366

-0.2466

P value

0.7819 - NS

0.7580 - NS

0.8006 - NS

0.0843 - NS

 

 

Correlation of rise of DBP during HG

30/15 ratio

S/L ratio

E/I ratio

Valsalva Ratio

Person’s Correction Coefficient (r)

-0.1907

-0.2223

-0.1720

-0.0832

P value

0.1847 - NS

0.1208 - NS

0.2324 - NS

0.56561 - NS

There is a rise in correlation in SBP and DBP of all the parameters during Handgrip with regard to 30/15 ratio, S/L ratio, E/I ratio and Valsalva Ratio in the Group II. However, all the P values of correlation were found to be not significant.

DISCUSSION:

The mean age in the Group - 1 was 23.08 and Group - II was 23.58. There is no significant difference in the mean heights of the Group - 1 and Group - II. The mean weight of the Group - 1 and Group - II was calculated at 59.68 kgs and 60.52 kgs respectively and was found there is no significance. The mean of the BMI of the Group - 1 and Group - II was 24.69 Kg/m2 and 25.41 Kg/m2 respectively and is found to be not significant. The gestational age of Group - I and Group - II was 31.62 and 31.92 respectively and mean is found to be not significant. The systolic blood pressure of Group - I and Group - II was noted as 131.9 and 154.8 respectively and is found to be extremely significant. The diastolic Blood Pressure of Group – I, was recorded as 70.72 and Group - II was recorded as 100.4 and the P value was found as extremely significant. During normal pregnancy, peripheral vascular resistance decreases by around 21% due to smooth muscle relaxing effect of progesterone, nitric oxide (NO) prostaglandins and ANP. The fall in peripheral vascular resistance is reflected in the diastolic blood pressure (8).

Mean Arterial Pressure is found at 85.12 mm Hg and 118.8 mm Hg respectively and is of very high significance. The preeclamptia is associated with significant rise of systolic, diastolic and mean arterial pressure. The resting Heart Rate is not significant between both groups i.e. Group - I and Group - II Increase in hear rate in Kapoor N (2011) Group - I is explained by the Bainbridge reflex occurring due to the increase in the end diastolic volume caused by hemodilution (6).

The rise in systolic blood pressure (SBP) and diastolic blood pressure (DBP) during cold pressure test in Group – I and Group – II shows the increase in mean i.e. 13.52 & 15.92 and 9.040 & 10.96 respectively. The finding of the present study is in accordance with the findings of earlier studies by Schebel Hans P (9), Woisetschlarger (10), Rang SA (2). The Cold Pressure Test (CPT) is a measure of response, indicates increased vascular reactivity in preeclampsia. As the vascular reactivity is vasoconstriction (11), which reflects increased blood pressure response during the test and as such CPT is an index of vascular reactivity (11). A significantly increased vasoconstructive response to a cold stimulus is seen in women compared to normal pregnant women i.e. significant blood pressure determined by sympathetic activity (10), it can be said the preeclamptic women shows increased sympathetic activity as compared to the normal pregnant women.

Handgrip test: (Table-7): The study indicates the rise in systolic blood pressure (SBP) and diastolic blood pressure (DBP) respectively during handgrip test in both Group - I and Group - II subjects. The mean rise in SBP and DBP was 13.4 mmHg & 11.68 mmHg in Group - I and 14.96 mmHg & 13.96 mmHg in Group - II respectively. There is no significant difference in systolic blood pressure in Group - I and Group - II subjects, but there is significant increase in diastolic blood pressure in Group - I subjects, when compared to Group - II subjects. The finding of the present study is in conformity with the findings of Degani S (12), Baker PN (13), Rang SA (2002) (2). Blood pressure response to handgrip test, a measure of cardiac sympathetic activity (2), is significantly increased in preeclampsia as compared to normal pregnancy and it indicates increased sympathetic activity in preeclampsia as compared to normal pregnancy.

Standing Ratio (30/15 ratio): (Table-8): The mean 30/15 of the Group - I and Group - II was 1.206 & 1.110 and is very significant (p<0.01). The finding of the study is in conformity with the finding of the studies of Bachlaus N (6), Rang SA (10).

Deep breathing: (Table-8): The mean E/I ratio of the Group - I and Group - II was 1.203 & 1.211 and is significant p<0.05. The results of the present study is similar to that of the earlier study undertaken by Eeva Ekholm (14), Rang SA (2).

Valsalva ratio: (Table-8): The Valsalva ratio of the Group - I and Group - II was 1.533 & 1.479 and is not significant p<0.05. The findings of the present study is in accordance with the earlier studies made by Rang SA (2), Hans schoble (9), Eeva ekholm (14),

CONCLUSION:

The normal pregnant (group - I), has significantly lower diastolic pressure and mean arterial pressure, significantly higher resting heart rate. Rise in SBP & DBP, to cold stimuli and handgrip is significantly increased in preeclamptic pregnant (group - II).

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  4. Ghai CL A textbook of practical Physiology. 7th edition. New Delhi: Jaypee Brothers; 2007. Chapter 36, Autonomic nervous system (ANS) tests; p. 242-7.
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  10. Woisetschlager , Waldenhofer U, Bur A, Herkner H, Kiss H, Binder M, Laggner AN, Hirschl MM. Increased blood pressure response to the cold pressue test in pregnant woman developing preeclampsia. Journal of Hypertension 2000 Apr;18(4):399-403.
  11. Godden JO, Roth GM, Hines EA, Schlegal JF. The changes in the intra-arterial pressure during immersion of the hand in ice-cold water. Circulation 1955 Dec;XII;963-73.
  12. Degani S, Abinader E, Eibschitz I, Oettinger M, Shapiro I, Sharf M. Isometric exercise test for predicting gestational hypertension. Obstet Gyecol 1985 May;65(5):652-4.
  13. Baker PN, Johnson IR. The use of the hand-grip test for predicting pregnancy-induced hypertension. Europion Journal of Obstetrics & Gynecology and Reproductive Biology 1994;56:169-72.
  14. Ekholm EMK, Erkkola RU. Autonomic cardiovascular control in pregnancy. Europ J Obstet Gynec Reprod Biol 1996 Jan; 64(1):29-36.




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