European Journal of Cardiovascular Medicine

Spinal anesthesia is a convenient and cost-effective technique that provides excellentanesthesia and post-operative analgesia, mainly used for lower abdominal, pelvic, and lower limb surgeries¹.The most common complication with spinal anesthesia is bradycardia and hypotension caused by the blockade of the sympathetic nervous system².

During surgery, hypotension is associated with a higher risk of causing myocardial ischemia and stroke. But hypertension being a risk factor on its own for conditions like coronary heart disease, congestive heart failure, and cerebrovascular diseases, implies that the adverse effects of hypotension may be more pronounced in hypertensive individuals^3,4.The intra operative hemodynamic variations in hypertensive patients indicate both the response to antihypertensive medications and the cardiovascular reaction to anesthetic drugs.This risk can be reduced by effectively controlling blood pressure before surgery and continuation of pre-operative antihypertensive therapy⁵.

Changes in the structure of arteries are a significant factor in how the body responds to anesthesia, leading to more pronounced alterations in systemic vascular resistance and blood pressure in individuals with hypertension. This study aims to compare the Spinal Anesthesia-induced hemodynamic changes in Normotensive and Hypertensive patients on antihypertensive Medications.

Thisobservational studywas conducted in the Department of Anaesthesiology from January 2014 to October 2015, inGovernment Medical College & Hospital. Approval was received from the institutional ethics committee.Written informed consent was taken from 60 patients between 20 -70 years,who were elective cases of Inguinal Hernia (Unilateral / bilateral) and Hydrocoele (Unilateral / bilateral) posted for surgery.

Inclusion criteria:

• Consent for the study
• Age group: 20 - 70 years
• ASA Grade I & II
• Patients posted for Elective surgery (Inguinal hernia and hydrocoele)
• Hypertensive patients irrespective of status of control of blood pressure. Patients with co-morbid conditions e.g. ischemic heart disease, Old myocardial infarction > 6 months old, Diabetes mellitus etc.

Exclusion criteria:

• Not given consent
• Age < 20 years &> 70 years
• ASA grade III & IV
• Emergency surgical patients of Obstructed inguinal hernia &Pyocoele.
• Patients with neurological diseases e.g. Paraplegia, hemiplegic etc.
• Patients with LBBB, Complete heart block, Bypass surgery.
• Patient of Valvular heart disease/ old myocardial infarction within 6 months.

Pre anaesthetic checkup was done 24 – 48 hours before surgery. The patients were asked to continue the same antihypertensive & other medicationstill the day of operation, irrespective of type of drugs used for control of hypertension & co morbid disease management.

Pre operative investigations (Haemoglobin%, Complete blood count, Bleeding time & Clotting time, Blood sugar- Fasting & Post meal, Blood urea, Serum Creatinine, Chest X- Ray and ECG)were done. Tab. Diazepam- 10 mg. & Tab. Pantoprazole- 20 mg was given the previous night orally.

On the day of surgery, the patients were counselled individually for 5-10 minutes and recorded the baseline preoperative systolicblood pressure, diastolic blood pressure and pulse rate. The Multiparamonitor was attached for monitoring the hemodynamic parameters and ECG variations. Through the intravenous access established using 20 G intracatheter, preload fluid (Ringer’s lactate - 500ml) was administered10-15 minutes before spinal anaesthesia. The patient was given left or right lateral position on a horizontal table. Under all aseptic precautions, sterile 23 G (disposable) spinal needle was used to perform lumbar puncture at L3-L4 or L4-L5 inter-vertebral space. After confirming the needle location, Inj. Levo-bupivacaine 3.5ml (0.5%) was administered slowly. Then the patient was made supine and waited for 15 minutes before the surgeon prepare the area to operate.

After injection of spinal drug in to subarachnoid space, Heart Rate, Systolic & Diastolic Blood Pressure was noted intraoperatively- every 5 minute till first 30 minute. Later on, every 10 minutes till the end of surgery and thereafter at 24 hours, 48hours and 72 hours these parameters were again monitored.

When the systolic blood pressure falls >20% from baseline or if or systolic blood pressure drops to< 70 mm/ Hg it was termed as hypotension and when the Heart rate is < 60 beats/ min it was considered as Bradycardia^6,7.

       STATISTICAL ANALYSIS:

       Continuous variables were expressed as mean ± standard deviation (S.D.), while categorical variables were presented as actual numbers and percentages. Statistical analysis was conducted using STATAsoftware, version 13.0.Data comparison was done by application of specific statistical tests such as Z test and ANOVA to find out the statistical significance, wherever it is applicable. P< 0.05 was considered as statistical significance.

       A total of 60 participants fulfilling inclusion criteria were enrolled in the study among which 26 participants were hypertensive and 34 normotensives. The mean age was 48.46 ± 13.25 years and all the participants were males. Out of 60 participants posted for surgery, 20 patients were diagnosed for hydrocoele and 40 patients for inguinal hernia.Out of 26 hypertensive participants, 7 were taking Calcium channel blockers, 4 participants each were on ARBs and Beta blockers, 2 of them on ACE inhibitors, and 9 were receiving combination therapy.

       The mean heart rate of both hypertensives and normotensive patients showed a raise from the base line value (74.5±10.58 in hypertensives and 77.21±7.29 in normotensives) till the end of surgery (80.69±7.25in hypertensives and 84±8.55in normotensives), and showed a slight decline after 24 hrs of surgery. (figure 1). The mean heartrate among hypertensives and normotensives were not statistically significant. (Table 1).

Figure 1: Variation in heart rate in hypertensive and Normotensive patients

The baseline value of mean SBP was higher in hypertensive patients (141.15 ±15.76mmHg) compared to normotensive patients (123.18 ±8.93 mmHg).A gradual fall in systolic BP was noted after administering spinal anesthesia, with a maximum fall at 25 minutes(117.92 ± 17.07in hypertensives and 117.06 ± 9.45 in normotensives). There after the systolic BP raised among both the groups. (Figure 2).

Figure 2: Variation in Systolic Blood Pressure at Different Time Point

Similarly, mean DBP at baseline was higher in hypertensives patients (83±6.23mmHg) compared to normotensives (81.47±8.37 mmHg). In hypertensive patients the maximum fall in DBP after spinal anesthesia was noted at 20 minutes (79 ±9.35 mmHg) whereas in normotensives the same was recorded at 40 minutes (77.35 ± 9.94) (Figure 3). The mean systolic and diastolic BP among both the groups were statistically significant. (Table 1)

Figure 3: Variation in Diastolic Blood Pressure at Different Time Point

            Table 1: Mean values of Hemodynamic parameters among hypertensives and normotensives

*Z test applied, P value <0.05 is statistically significant

Age wise variation in mean blood pressure was noted separately for hypertensives and normotensives among which the systolic blood pressure among hypertensives showed a statistically significant decline from 30years to 70 years. (Table 2)

Table 2: Age Wise Variations in Blood Pressure

*ANOVA test applied, P value <0.05 is statistically significant.

Most common side effect of Spinal anaesthesia is hypotension and bradycardia which leads to inadequate blood supply to the heart and brain, which can result in ischemia. Previous literatures suggest that the intra operative hypotension was more pronounced among hypertensives and regular use of antihypertensive medication could prevent it⁸.  The class of anti-hypertensive medications taken by the hypertensive group of participants includes Angiotensin receptor blocker (n=4), Angiotensin converting enzyme inhibitors (n=2), Calcium channel blockers(n=7), Beta Blockers (n=4) and Combination therapy(n=9).

In our study, the incidence of bradycardia was 25%.The variations in mean heart rates among hypertensives and normotensive were statistically significant from 10 minutes to 72 hrs (p – value < 0.0001, HS).Christian Glaser et.al⁹ in his study to evaluate the anaesthetic potencies and haemodynamics of intrathecal Levobupivacaine compared with racemic bupivacaine, a slight decrease in mean heart rates over 30 min after anesthesia was noted, which was not associated with significant inter-group differences in haemodynamics.

The incidence of hypotension among hypertensive patients in our study was 34.6% whereas it was 11.7% among normotensives The hypertensive patients showed a higher baseline systolic blood pressure compared to normotensives, but post spinal anesthesia fall in blood pressure was noted for both the groups. The mean systolic blood pressure among hypertensives and normotensives from 10 minutes to 72 hours were found to be statistically significant.In a prospective Cohort Study by Gebrargs L et al,. themean SBP betweenthe controlled hypertensive and normotensive groups was statistically significant at 15 min,20 min, 25 min, and 30 min¹⁰. Panda A et al,. in his research among 3 groups: hypertensives on calcium channel blockers, hypertensives receiving calcium channelblockers with beta-blockers and normotensives noted significant declines inSBP post spinal anesthesia.The fall in systolic BP were observed in group 1, group 2, and group 3 at 15 minutes, 90 minutes, and 120 minutes after SAB, respectively¹¹.

In this research we noted a maximum fall in DBP post spinal anesthesia at 20 minutes and 40 minutes for hypertensives (79 ±9.35 mmHg) and normotensives (77.35 ± 9.94) respectively.Also, the variations in diastolic blood pressure were significant at 10, 25, 30, 50, 70, 80 and 90 minutes in both hypertensive and normotensive patients.The diastolic blood pressure should either remain stable or increase slightly and the exactdiastolic blood pressurethreshold is a subject of much debate. Additionally, there is ongoing discussion about whether this threshold should be different for patients with obstructive coronary disease, as they may be more susceptible to decreased coronary perfusion during diastole¹².

The systolic blood pressure among hypertensives in the current study showed a statistically significant decline (from 134.45 ± 7.37 to 119.46 ± 4.40) from 30years to 70 years. Chinachoti T and Tritrakarn Tfound that, age more than 50 years was a non-modifiable risk factor in relation to incidence and risk factors of hypotension and bradycardia during spinal anesthesia¹³.A prospective study by Randall L.Carpenteret.alfound that variablesconferringincreased oddsofdevelopinghypotensionincluded  age~40 year¹⁴.

The intra-operative hypotension& bradycardia was treated with titrated doses of Inj. Mephentermine (3 - 6 mg IV bolus) & Inj. Atropine (0.2 mg IV bolus) every 5- 10 min. till the systolic blood pressure was returned to 80 mm/ Hg or above & Heart rate was 60/ min. or above respectively. Preoperative or intraoperative sedation/ analgesia drugs were not administered to patient so as to avoid confusion of observations of the drug effects of drug under study.

In the present study, post spinal anesthesia,the occurrence of hypotension among hypertensives on medication was higher than the normotensive group. Similar observations were found in a prospective cohort study by Yousaf MU et al,¹.

The higher incidence of hypotension in patients with hypertension may be due to elevated sympathetic activity and norepinephrine levels, along with reduced parasympathetic activity and continuous sympathetic stimulation. This can also lead to a loss of arterial wall elasticity and structural changes, which, when combined with the sympathetic blockade induced by spinal anesthesia, result in a significant decrease in blood pressure¹⁵.

The incidence of hypotension was more among hypertensive participants on antihypertensive medications and as the age increases the systolic blood pressure showed a declining trend among hypertensives.Therefore, we advise taking essential precautions when administering spinal anesthesia to elderly hypertensive patients, as the increased risk of hypotension can cause severe cardiovascular effects, end organ damage and even sudden death.

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