This has been submitted in partial fulfilment of regulations of The Tamil Nadu Dr

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“COMPARISON OF 0.25% BUPIVACAINE WITH 0.375% ROPIVACAINE FOR FIELD BLOCK IN

INGUINAL HERNIA REPAIR”

Dissertation submitted to

The Tamil Nadu Dr.M.G.R. Medical University Chennai – 600032.

In partial fulfilment of the regulations for the Degree of

M.D.ANAESTHESIOLOGY BRANCH – X

Under the guidance of

Dr.R.SELVAKUMAR M.D., D.A., Professor and Head of the Department

DEPARTMENT OF ANAESTHESIOLOGY

K.A.P.VISWANATHAM GOVT. MEDICAL COLLEGE, TRICHY.

APRIL - 2017

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BONAFIDE CERTIFICATE

This is to certify that this dissertation titled “COMPARISON OF 0.25 % BUPIVACAINE WITH 0.375% ROPIVACAINE FOR FIELD BLOCK IN INGUINAL HERNIA REPAIR” is a bonafide work of Dr.J.RAMYA, Post Graduate in M.D.Anaesthesiology, Department of Anaesthesiology, K.A.P.V. Government Medical College, Trichy and has been prepared by her under our guidance. This has been submitted in partial fulfilment of regulations of The Tamil Nadu Dr. M.G.R. Medical University,Chennai-32 for the award of M.D. Degree in Anaesthesiology.

Prof. Dr.S.LILY MARY Dr. R.SELVAKUMAR. M.D, D.A

Dean, Professor and Head of Department,

K.A.P.V. Govt. Medical College, Department of Anaesthesiology

Trichy. K.A.P.V. Govt. Medical College,

Trichy

Place:Trichy Date:

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DECLARATION

I Dr.J.RAMYA, solemnly declare that this dissertation titled

“COMPARISON OF 0.25% BUPIVACAINE WITH 0.375%

ROPIVACAINEFOR FIELD BLOCK IN INGUINAL HERNIA REPAIR”, is a bonafide work done by me at K.A.P.V. Government Medical College, during 2015-2016 under the guidance and supervision of Dr.R.SELVAKUMARM.D.,D.A., Professor and Head Of the department, Department of Anaesthesiology, K.A.P.V. Government Medical College, Trichy.

The dissertation is submitted to The TamilnaduDr. M.G.R. Medical University, towards the partial fulfillment of requirement for the award of M.D. Degree in Anaesthesiology Branch X.

PLACE :TRICHY DATE :

Dr. J.RAMYA,M.B.B.S., Post Graduate Student,

Department of Anaesthesiology, K.A.P.V. GOVT. Medical College, Trichy.

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COPYRIGHT

DECLARATION BY THE CANDIDATE

I hereby declare that The Dr.M.G.R Medical University, Chennai, shall have the rights to preserve, use and disseminate this dissertation in print or electronic format for academic /research purpose.

Dr. J.RAMYA, M.B.B.S., Post Graduate Student,

Place: Trichy Date:

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ACKNOWLEDGEMENT

I thank our DEAN Prof.Dr.S.MARY LILLY, K.A.P.V. Govt.

Medical College, Trichy for permitting me to conduct this study in the Department of Anaesthesiology, K.A.P.V. Government Medical College, Trichy.

My sincere thanks to Prof. Dr.R.SELVAKUMAR,M.D.,D.A., Head of Department of Anaesthesiology, for helping and guiding me during this study.

My heartfelt gratitude to Prof. Dr.G.SIVAKUMAR M.D.,D.A., Prof. Dr.M.SURESH,M.D.,D.A.,and Prof. Dr.P.ElANGO M.D for their esteemed guidance and valuable suggestions.

It is my privileged duty to thank Asst.Prof.DR.L.R.GANESSAN M.Dand DR.BALASUBRAMANIAGUHAN M.D., for their constant help and encouragement in preparing this dissertation.

My sincere thanks to all my Assistant Professors who have put in countless hours in guiding me in many aspects of this study and also in honing my anaesthetic skills.

I thank my fellow Post graduates who helped me in conducting the study.

I am greatly indebted to all my patients without whom this study would not have been a reality.

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I thank all the anaesthesia assistants and staff nurses who cooperated with me at all times.

My sincere thanks to Prof. Jesu raja for his help and advice on statistical methods.

I take this opportunity to thank my family and my friends for their unconditional love and support.

Dr.J.RAMYA, M.B.B.S., Post Graduate Student,

Place: Trichy Date:

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LIST OF ABBREVIATIONS USED (In alphabetical order)

ASA - American Society of Anaesthesiologist ASIS - Anterior superior iliac spine

BP - Blood pressure

CNS - central nervous system CVS - cardiovascular system ECG - electrocardiography

EOA - external oblique aponeurosis GA - general anaesthesia

Gm - grams

HR - heart rate

I.M - Intramuscular

IOA - internal oblique aponeurosis LA - local anaesthesia

Mcg - microgram Min - Minute

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mmHg - Millimeter of mercury

MIL - midpoint of inguinal ligament

MPK - Mitogen activated protein kinase pathway RS - respiratory system

SBP - Systolic blood pressure

Sec - Seconds

TF - transversalis fascia VAS - visual analog scale VRS - verbal rating score % - Percentage

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CONTENTS

S. No Title Page No.

1. INTRODUCTION 1

2. AIMS AND OBJECTIVES 3

3. REVIEW OF LITERATURE 4

4. HISTORICAL REVIEW 9

5. ANATOMY OF INGUINAL FIELD BLOCK 13

6. PHARMACOLOGY 19

7. MATERIALS AND METHODS 33

8. OBSERVATION AND RESULTS 42

9. DISCUSSION 71

10. CONCLUSION 77

11. SUMMARY 78

12. BIBLIOGRAPHY 80

13.

ANNEXURES

A. PROFORMA B. CONSENT FORM C. MASTER CHART

86 89 92

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LIST OF FIGURES

Figure

No. Title Page

No.

1. LUMBAR PLEXUS 11

2. DERMATOMAL INNERVATION 12

3. TECHNIQUE OF FIELD BLOCK 15 4. CHEMICAL STRUCTURE OF

BUPIVACAINE

19 5. BUPIVACAINE HYDROCHLORIDE 19 6. CHEMICAL STRUCTURE OF

ROPIVACAINE

25 7. ROPIVACAINE HYDROCHLORIDE 25

8. VISUAL ANALOG SCALE 37

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LIST OF GRAPHS

Graph

No.

1. COMPARISON OF BMI 43

2. COMPARISON OF ASA 45

3. COMPARISON OF ONSET OF BLOCK 46 4. COMPARISON OF ADEQUACY OF

BLOCK 53

5. COMPARISON OF SIDE EFFECTS 55 6. COMPARISON OF SIDE EFFECTS

OBSERVED 56

7. COMPARISON OF SURGEON

SATISFACTION 58

8. COMPARISON OF TIME REQUIREMENT

FOR FIRST ANALGESIC 60

9. COMPARISON OF MEAN HEART RATE 66 10. COMPARISON OF MEAN SYSTOLIC

BLOOD PRESSURE 69

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LIST OF TABLES Table

No.

1. PAIN SCORE WITH VISUAL ANALOG SCALE 37

2. ADEQUACY OF BLOCK 38

3. VERBAL RATING SCORE 40

4. SURGEON SATISFACTION SCALE 41 5. SURGEON SATISFACTION SCORE 41

6. COMPARISON OF BMI 43

7. COMPARISON OF ASA 45

8. COMPARISON OF ONSET OF BLOCK 46 9. AVERAGE TIME OF ONSET OF BLOCK 51 10. ONSET OF BLOCK IN ACTUAL NUMBER OF

PATIENTS

52 11. COMPARISON OF ADEQUACY OF BLOCK 53 12. COMPARISON OF SIDE EFFECTS 57 13. COMPARISON OF SURGEON SATISFACTION 59 14. COMPARISON OF TIME REQUIREMENT FOR

FIRST ANALGESIC

61 15. AVERAGE DURATION OF POST-OP PAIN

RELIEF

63 16. POST-OP ANALGESIC DURATION IN ACTUAL

NUMBER OF PATIENTS

64 17. COMPARISON OF MEAN HEART RATE 65 18. COMPARISON OF MEAN SYSTOLIC BLOOD

PRESSURE

67

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1

INTRODUCTION

Hernia repair is one of the commonest surgery among worldwide operations. Herniorraphy and Hernioplasty are the techniques for Inguinal hernia repair. Newer technique of laparoscopic mesh repair is also in practice.

Hernia repair can be performed under spinal, epidural, general anaesthesia and inguinal field block. The preferred choice for all reducible Inguinal hernia is local since it inhibits the build up of local nociceptive receptors, hence a longer postoperative pain relief¹. Also it is safe, simple and effective without post anaesthesia side effects.

Compared to other techniques spinal /General anaesthesia (GA), field block does not provide a satisfactory level. But it provides prolonged postoperative analgesia, reduced urinary retention and early ambulation.

Also it is a cost effective method^2,3 in day care surgery warranting a speedy recovery and also the preferred anaesthesia in geriatric patients with underlying systemic pathology.

Postoperative analgesia is now regarded as an integral part of the surgical care. Insufficient analgesia can have significant pathophysiological and psychological effects in post-operative patients⁴. Lack of pain relief may manifest as haemodynamic changes in the form

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of tachycardia and hypertension, tachypnoea and hypoxemia, altered gastrointestinal motility, impaired urinary tract function⁵.

The introduction of Bupivacaine and Ropivacaine , other amide local anaesthetic agents with longer duration of action when compared with lignocaine which has a moderate duration of action⁶ has an added advantage of providing prolonged post op analgesia. Ropivacaine compared with bupivacaine has better cardiac stability with comparable analgesia⁷.

Hence this study of Field block is undertaken to objectively test the efficacy of block , side effects and degree of postoperative pain relief comparing the two drugs Bupivacaine and Ropivacaine.

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AIMS AND OBJECTIVE

To study and compare the The onset of analgesia The adequacy of block

The duration of postoperative pain relief

Side effects if any, that occurs with the usage of the two drugs Haemodynamic changes

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REVIEW OF LITERATURE

A comparative study of 0.5% Bupivacaine and 0.5% Ropivacaine for day case inguinal herniorraphy in a Nigerian tertiary institution was done showing that Ropivacaine and Bupivacaine have comparable onset of actions and adequacy of anaesthesia⁸.

Randomized study of 160 patients conducted by F H Andersen K Nielsen at surgical clinic Charlottenlund, Copenhagen, Denmark- combined ilioinguinal blockade and local infiltration anaesthesia for groin hernia repair, showed median intra-operative pain score reduced with additional ilioinguinal blockade. Study concluded that additional use of a preoperative ilioinguinal field block to well established local infiltration anaesthesia procedure for inguinal hernia repair improves intra-operative pain relief⁹.

Retrospective analysis conducted by P Sanjay, A Woodward, in department of surgery of Ninewells hospital and medical school, revealed tha patient satisfaction is more in local anaesthesia. Also it was seen that local complications like wound hematoma, wound infection, recurrence readmission, postoperative hydrocele is more with local anaesthesia, but there is significant reduction of postoperative urinary retention. Study concluded that use of Local Anaesthesia (LA) results in increased day

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case-rates, lower postoperative analgesic requirements and fewer micturition problems¹⁰.

Prospective study of 454 patients of inguinal hernia repair with local anaesthesia in the outpatient by Flavio Antonio de Sa Ribeiro, Fernanda Padron, et al showed that there were no adverse effect of local anaesthetics and concluded that procedure is feasible and causes no peri- operative pain, safe and has satisfactory patient acceptance¹¹.

Study conducted by Khurram Niaz, Javed Iqbal et.al at Department of general surgery Bahawal Victoria hospital showed mean hospital stay was 3 days in patients operated under spinal anaesthesia as compared to 24 hours in patients operated under local anaesthesia. Patients operated under spinal anaesthesia had higher morbidity such as urinary retention, post spinal back ache, hypotension, pain and delayed mobilization in post-operative period. As compared patients operated under local anaesthesia had increased incidence of wound infection and hematoma.

They concluded that local anaesthesia is a better option for inguinal hernia repair as compared to spinal anaesthesia with respect to postoperative complications and patients comfort in young as well as old aged patients¹².

Prospective study of 72 hernia patients operated under local anaesthesia by Jihad OdehMazenAlomari et al at Prince Ali hospital

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Jordan, showed 83.3% of patients denied any discomforts during operation, 7% experienced mild discomfort, 5.5% experienced slight pain, and 4% required conversion to general anaesthesia due to patient‟s anxiety. The study concluded that preferred choice for all reducible, adult inguinal hernia repairs is local. It is safe simple, effective and economical without post anaesthesia side effects and produces longer post-operative analgesia¹³.

Comparative study of local versus spinal anaesthesia in 100 cases of inguinal hernia repair at Saraswati institute of medical sciences, Srivastava Arati, Sharma Shailja et al. showed that operative analgesia was equally satisfactory in both groups and concluded that augmented LA results in increased day care surgery rates, lower post-operative analgesic requirements and fewer urinary problems¹⁴.

Development in local anaesthetic drugs were studied by J.B Whiteside and J.A Wildsmith in 2001, they found similar onset and extent of both motor and sensory block but slightly longer duration of analgesia with a more concentrated solutions of Ropivacaine. However different concentrations were made in the both obstetric and non-obstetric population but no significant differences in onset and duration of sensory block was found. The motor block was less intense and of shorter duration with Ropivacaine¹⁵.

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J.H.Mcclure in his study on Ropivacaine concluded that Ropivacaine is an effective long acting local anaesthetic. The sensory block produced by Ropivacaine is similar to that produced by an equivalent dose of Bupivacaine for extradural block, but however the motor block is less intense slower in onset and duration when compared to Bupivacaine. This together with lower toxicity compared with Bupivacaine, enables Ropivacaine to be used for surgical anaesthesia in concentrations up to 1%¹⁶.

M.s. Brockway , J.Bannister , J.H.McClure, D.Mckeown and J.A.W.Wildsmith. Comparison of extradural ropivacaine and bupivacaine. Ropivacaine produced slower onset, shorter duration and less intense motor block as compared to same concentration of Bupivacaine¹⁷.

Acute toxicity of Ropivacaine was compared with Bupivacaine by D.Bruce scott Alistair lee et al. They concluded that Ropivacaine caused less neurological symptoms and 25% less toxic than Bupivacaine in regard to dose tolerated. There was no change in cardiac output. Although both drugs caused evidence of depression of conductivity and contractility of heart, these are found at a lesser plasma concentration with Bupivacaine than Ropivacaine¹⁸.

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Pharmacology, toxicology and clinical use of new long acting local anaesthetics Ropivacaine and Levobupivacaine were studied by Stefania leone, Simone di et al on comparing racemic Bupivacaine with Ropivacaine, they found that Ropivacaine showed the clinically relevant advantage of a stronger differentiation between sensory and motor blocks which is particularly useful for early mobilisation. They also found that Ropivacaine is 40-50% less potent than Bupivacaine because of its lower lipid solubility. Equipotency ratio of 1.5:1 (ropivacaine:bupivacaine) gives a good preservation of motor function¹⁹.

Philipp Lirk, Ingridhaller, Hanspeter et al studied in vitro inhibition of mitogen activated protein kinase pathway (MAPK) protect against Bupivacaine and Ropivacaine induced neurotoxicity. They showed that Bupivacaine and Ropivacaine exert their neurotoxic effects by MAPKs, while specific pharmacologic inhibition of these kinases attenuates neurotoxicity in vitro²⁰.

There were no significant differences between groups in pain, need for supplementary analgesic, motor block and ability to walk. Patients in the Ropivacaine group received significantly more ketorolac than patients with Bupivacaine. Time to discharge from hospital was similar with both group²¹.

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HISTORICAL REVIEW

Hernia is the word derived from the Greek word “the herons” an offshoot or bulge. It is defined by Sir Astley Cooper (1840) as protrusion of viscus or any part of viscus through an abnormal opening in the walls of its containing cavity²².

August bier is the father of intrathecal anaesthesia. He theoritized that his technique , called cocainization of the spinal cord, might provide the pain relief necessary for major surgery.

The discovery of local analgesic effect of cocaine by Carl koller in 1884 made possible the vast array of peripheral local and regional analgesic therapy, whereas previously the only major site of pain control was thought to be brain²³.

Cocaine is a naturally occurring compound. It was the first anaesthetic to be discovered and the only naturally occurring local anaesthetic. Introduced into Europe in 1800s, Sigmund freud the noted Austrian psychoanalyst , used cocaine on his patients and became addicted through self experimentation.

In the latter half of 1800s, Koller introduced cocaine to the field of ophthalmology and Hall introduced into the dentistry. Halsted was the

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first to use cocaine in nerve blocks in The United states in 1885 and also became addicted.

The use of cocaine for local and regional anaesthesia rapidly spread throughout Europe and America. The toxic effects of cocaine led to many deaths among both patients and medical staffs. The development of modern organic chemistry led to the synthesis of pure cocaine in 1891.

New amino esters were synthesized between 1891 and 1930 - tropocaine, eucaine, holocaine, orthoform, benzocaine and tetracaine. Amino amides were prepared between 1898 and 1972 nirvaquine, procaine, choloroprocaine, cinchocaine, lidocaine, mepivacaine, prilocaine, efocaine, bupivacaine, etidocaine and articaine.

Procaine was the first synthetic derivative of cocaine introduced in 1904. Later Lofgren developed lignocaine, the most widely used LA during world war II in 1943. Bupivacaine is of special interest due to its long duration of action and wide clinical application. Synthesized in 1957, the introduction of bupivacaine also paralleled reports of neurotoxicity and cardiotoxicity which refined our study in understanding of local anaesthetics.

The study on optically active isomers of mepivacaine family led to the selection of ropivacine , a pure s-(-) enanatiomer, which was extensively studied for toxicity before introducing into market in 1996.

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Figure-1 LUMBAR PLEXUS

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Figure-2 DERMATOMAL INNERVATION

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ANATOMY OF FIELD BLOCK (figure-1)

Nerves of interest for the inguinal field block are the ilio inguinal, ilio hypogastric, genitofemoral and lateral cutaneous nerves of thigh.

The ilio inguinal and ilio hypogastric nerves arise together from the first lumbar nerve L1. The ilio inguinal nerve emerges from the lateral border of the psoas major and passes obliquely across the quadratus lumborum. At a point just medial to the anterior superior iliac spine it pierces the transversus and the internal oblique muscle to enter the inguinal canal and exits through the superficial inguinal ring. It supplies the somatic sensation to the skin of the upper and medial thigh. In males it also innervates base of the penis and the upper scrotum. In females it innervates the mons pubis and the labium majus.

The ilio hypogastric nerve arises from T12 L1. After it pierces the deep abdominal wall it courses between the internal oblique and the transversus abdominis supplying both.

The genitofemoral nerve arises from L1 L2. Courses along the retro peritoneum and emerges on the anterior aspect of psoas. It then divides into genital and femoral branches. The genital branch enters the inguinal canal lateral to inferior epigastric vessels and it courses ventral to iliac vessels and ilio pubic tract. In males it travels through the

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superficial inguinal ring and supplies the ipsilateral scrotum. In females it supplies the ipsilateral mons pubis and labium majus.

The femoral branch courses along the femoral sheath supplying the skin of the upper anterior thigh. The lateral femoral cutaneous nerves arises from L2 L3 emerges lateral to psoas muscle at the level of L4 and crosses the iliacus muscle obliquely towards the anterior superior iliac spine. It then passes inferior to the inguinal ligament where it supplies the lateral thigh.

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Figure-3 FIELD BLOCK

3.a-2cm above and medial from Anterior superior iliac spine

3.b – pubic tubercle

3.c- 0.5cm below midpoint of inguinal ligament

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3.d – midline for blocking crossing over fibres

3.e – skin incsion

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PROCEDURE OF FIELD BLOCK FOR INGUINAL HERNIA REPAIR

The block was done using the technique described by Pinnock et al^24. (fig-3).

The dermatome involved in the block is shown in (fig-2)

1. Under strict aseptic precautions, 40 ml of solution for the block (20ml of LA + 20ml distilled water) was prepared by the researcher who is blinded further in the study.

2. The patient is placed in spine position

3. A skin wheal is made half inch medial and superior to anterior superior iliac spine (ASIS). A 22 G hypodermic needle was fixed to a syringe containing 10 ml of the local anaesthetic, was directed perpendicular to the skin. The needle was placed above the Internal oblique aponeurosis (IOA) piercing the External oblique (EOA) and 2 ml of local anaesthetic was given and 4 ml was given in a fan shaped manner at 45 degree. (Total = 2+2+2ml) (fig-3.a)

4. The Internal oblique aponeurosis pierced and local anaesthetic injected in a fan shaped manner over the Transversalis fascia (TF).

(Total = 2+2+2ml) (fig-3.a)

5. A second wheal was made over the pubic tubercle (PT) and 5 ml of local anaesthetic was injected (fig-3.b)

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6. A third skin wheal was raised 0.5 cm above the midpoint of inguinal ligament (MIL) and 5 ml of local anaesthetic deposited (fig-3.c)

7. Then by using 23 G spinal (quincke) needle a subcutaneous infiltration was done along the midline to block the crossing over fibres. (8ML) (fig-3.d)

8. A 5 ml of local anaesthetic was infiltrated along the line of incision (fig-3.e)

So a total of 35ml was given for the block and 5ml was reserved to be given at the neck of the sac , if needed during the traction.

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PHARMACOLOGY

Figure -4 CHEMICAL STRUCTURE OF BUPIVACAINE

Figure-5 BUPIVACAINE HYDROCHLRIDE

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BUPIVACAINE HYDROCHLORIDE^25,26

It was synthesised in 1957 by BOAFEKEMSTAN and was clinically first used in 1963 in L.J.TELIVUO.

Structural formula: CH3CH2CH2CH2NC C18H28N2O, HCL Physical and Chemical Properties :

a. It is a white, odourless, crystalline powder with a bitter numbing taste.

b. It is chemically synthesized. The hydrochloride salt is available in solution with and without epinephrine.

c. Intrathecal preparation specifically contains dextrose.

d. Chemically amide : 2-6 methyl amide.

e. Molecular weight : 325.

f. pH of saturated solution :5.2 g. pKa 8.1

h. Protein binding 96%

Mechanism of Action:

It prevents the generation and conduction of nerve impulses.it acts on the cell membrane, blocks the conduction by decreasing or preventing the increase in cell permeability of excitable membranes to Na + due to their direct interaction with voltage gated Na + channels.

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PHARMACOKINETICS Absorption:

It is rapidly absorbed from the site of injection, the rate of rise in plasma concentration and peak plasma levels depend on the particular anaesthetic technique employed.

Distribution:

It is explained by two compartment model.

a. The rapid distribution phase: It is by the uptake of rapid equilibrating tissue (i.e tissues that have high vascular perfusion).

b. The slow distribution phase: It is the distribution to slowly equilibrating tissue, biotransformation and excretion of the compound.

More highly perfused organs show higher concentrations of the drug. Though skeletal muscle does not show particular affinity for bupivacaine it is the largest reservoir of the drug.

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Distribution Characteristics:

1. T1/2a - 2.7 min 2. T1/2b - 2.8 min

3. Volume of distribution at steady state – 72 litres 4. Clearance (lit/min) – 0.47

Biotransformation and Excretion

a. Bupivacaine undergoes enzymatic degradation primarily in the liver.

b. It is excreted mainly through the kidneys. Renal perfusion and urinary pH affect urinary excretion. Renal clearance of this drug is related inversely to its protein binding capacity and pH of urine.

c. Less than 5% of unchanged drug is excreted via the kidney through urine. The major portion of injected agent appears in urine in the form of 2,6 pipecoloxylidide which is a N de- alkylated metabolite of Bupivacaine.

Dosage:

Maximal dose is 2mg/kg body weight (25-30ml 0.5% solution) and the strength used is 0.125%-0.75%.

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Toxicity:

It is relatively free of side effects if administered in an appropriate dosage. It is more cardiotoxic than Ropivacaine and this is made worse by hypoxia, hypercapnia and by pregnancy.

1. Central Nervous System Toxicity (CNS)

CNS is more susceptible to Bupivacaine. The symptoms are light headedness and dizziness followed by visual and auditory disturbance.

Disorientation and occasional feeling of drowsiness may occur. Objective signs are excitatory in nature which are shivering, muscular twitching and tremors, involving muscles of face (perioral numbness) and part of extremities. Acidosis increases the risk by increased levels of PaCo2 which eventually increases the cerebral blood flow, hence more of anaesthetic is delivered rapidly to brain. Higher doses results in cardiovascular and respiratory arrest.

2. Cardiovascular System²⁷

The primary cardiac effect of local anaesthetic is a decrease in the rate of depolarization in the fast conducting tissues of purkinje fibres and ventricular muscle. The reduction in rate is due to a decreased availability of fast sodium channels in cardiac membranes, action potential duration and refractory period. Bupivacaine depresses the rapid

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phase of depolarization (vmax) in purkinje fibres and ventricular muscle to a greater extent than ropivacaine does. It decreasesthe rate of recovery which lead to incomplete restoration of Na+ channel availability between action potentials particularly at high heart rates.

The ratio of dosage required for irreversible cardiovascular collapse and the dosage that will produce CNS toxicity (convulsion) (i.e, the CC/CNS ratio) is lower for bupivacaine than ropivacaine.

Pregnancy enhances cardiotoxicity of bupivacaine.

3. Respiratory System Toxicity:

Depression of medullary respiratory centre may be caused if excessive plasma level is reached.

4. Autonomic Nervous System Toxicity

Myelinated preganglionic beta fibres have a faster conduction time and are more sensitive to the action of local anaesthetics. When used for conduction blockade all local anaesthetics particularly bupivacaine produces higher incidence of sensory blockade than motor fibres.

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Figure-6 ROPIVACAINE CHEMICAL STRUCTURE

Figure -7 ROPIVACAINE HYDROCHLORIDE

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ROPIVACAINE28,29,30,26

Ropivacaine is a new long acting local anaesthetic belonging to amino amide group. It was synthesised by EKENSTAM in 1957. It belongs to the same group as bupivacaine, the pipecoloxylidide local anaesthetics. It was introduced into clinical practice in 1992³¹.

Historically Bupivacaine was used for its long duration of action, but it was found that propyl derivatives of pipecoloxylidide were less toxic than butyl derivatives. (i.e bupivacaine.)

It is the first local anaesthetic to be presented as an almost pure S- Enantiomer (greater than 99% pure). It is used for infiltration, nerve blocks, epidural and of late for intrathecal anaesthesia.

Physical and Chemical Properties:

a. It is a white crystalline powder.

b. Molecular formula - C17H26N2O.HCL.H2O.

c. Molecular weight is 328

d. pKa 8.1 (approximately same as bupivacaine)

e. Ropivacaine has a lower lipid solubility (owing to substitution of pipecoloxylidide with a 3 C side chain instead of 4 C side chain.)

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Dosage

Maximal dosage of Ropivacaine is 3mg/kg.

Ropivacaine is preservative free and is available as single dose containers in 2(0.2%), 5(0.5%), 7.5(0.75%) and 10(1%) mg concentrations.

Mechanism of Action

Ropivacaine reversibly interferes with the entry of sodium in nerve cell membranes leading to decrease permeability to sodium and thus

a. Block generation and conductance of nerve impulses b. Slows propagation of nerve impulses

c. Reduce the rate of raise of action potential

Most local anaesthetics block the unmyelinated „C‟ fibres and myelinated delta fibres that transmit pain impulses at the same rate.

However the rate of blockade of A delta and A beta (that carry motor impulses) depends on the physiochemical properties of the local anaesthetic. As Ropivacaine is less lipid soluble compared to Bupivacaine, the blockade of A delta and A beta is slow and hence produces less motor blockade than Bupivacaine.

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Clinically the order of blockade of nerve fibres is autonomic, sensory and motor while the disappearance occurs in reverse order. The order of the loss of nerve function is

1. Pain

2. Temperature 3. Touch

4. Proprioception 5. Skeletal muscle tone Pharmacokinetics

Absorbtion:

The systemic concentration of Ropivacaine is dependent on 1. Total dose and concentration of drug given

2. Route of administration

3. Patient‟s haemodynamic condition

4. Vascularity at the site of administration.

Distribution

After intravascular infusion Ropivacaine has a steady state of distribution of 417 litres. It is 94% protein bound mainly to alpha1 acid glycoprotein. Ropivacaine readily crosses the placenta.

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Metabolism

1. Ropivacaine is metabolised by aromatic hydroxylation in the liver, mediated by cytochrome p450 to 1alpha3 hydroxy Ropivacaine.

2. Rest is excreted in the urine as free and conjugated 3 hydroxy ropivacaine.

3. Low concentrations of 3hydroxy Ropivacaine is found in plasma.

4. An additional metabolite, 2-hydroxy-methyl-ropivacaine has been identified but not quantified.

Elimination:

Ropivacaine metabolites are excreted mainly through kidney.

After intravenous (iv) administration 86% of the dose is excreted in urine of which only 1% is in unchanged form.

Potency:

Lipid solubility determines the intrinsic anaesthetic potency.

Chemical compounds which are highly lipophilic tend to penetrate the nerve membrane more easily. So less number of molecules are required for conduction blockade. This results in increased potency of the drug.

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Adverse Effects:

Excessive plasma levels are due to over dosage, unintentional or slow metabolic degradation. The mean doses at which CNS symptoms or toxicity begin to occur are 4.3 mcg/ml of total and 0.6 mcg/ml of free plasma concentrations respectively. Various possible side effects include

a. Cardiovascular System- vasovagal traction, syncope, postural hypotension, nonspecific electrocardiographic abnormalities b. Gastro Intestinal – nausea, vomiting, fecal incontinence,

tenesmus

c. CNS – tremor, neuropathy, vertigo, convulsion and coma.

Because of depressant effect of ropivacaine on medulla, excitatory stage of CNS might not occur.

d. Liver and biliary- jaundice

e. Metabolic disorders- hypomagnesemia Management of Complications:

1. Discontinuation of Ropivacaine should be done at the first sign of toxicity.

2. No specific antidote is available.

3. Symptomatic and supportive management should be done promptly.

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31

4. Any change in mentation needs oxygenation. Secure airway and provide assisted ventilation if any signs of respiratory depression are observed.

5. Convulsions can be treated with barbiturates specific anticonvulsants or neuromuscular blockers.

6. In case of cardiac arrest prolonged resuscitative efforts might be required.

Advantages over other Local Anesthetics

1. Ropivacaine produces a more differential blockade allowing better separation between sensory and motor block . Hence it is a better choice for use in labour analgesia and postoperative pain.

2. When compared to bupivacaine it produces less motor blockade, shorter duration and hence permitting earlier mobilization and discharge.

3. It has low systemic toxicity than Bupivacaine and has a better cardio toxic profile

4. It is 40-50% less potent than Bupivacaine, Ropivacaine in an equipotent ratio of 1.5 :1 results in a similar clinical profile with good preservation of motor function.

(47)

32

Dosing of Local Anesthetics

Maximal dose of Bupivacaine is 2 mg/kg body weight and the strength used is 0.5%.

Maximus dose of Ropivacaine is 3 mg/kg and the strength used is 0.75%

The mean weight of the patients in the study is 60.0 kg and mean volume of LA used is 35 ml (20ml LA +20ml distilled water). The equipotent dosing of Ropivacaine and Bupivacaine is 1.5:1. It becomes clear that the total dose of local anaesthetic used lies within the recommended safe dosage.

(48)

33

Inclusion Criteria:

1. 18 - 60 years

2. ASA Physical status I & II 3. BMI 18-25

4. Co-operative patients 5. Unilateral hernia 6. Reducible hernia 7. Elective case

(49)

34

Exclusion Criteria:

1. Patients refusal

2. Hypersensitivity to local anaesthetics 3. BMI > 25

4. Chronic analgesic therapy 5. Giant inguinoscrotal hernias 6. Strangulated hernias

7. Hernia with hydrocele

8. Uncontrolled cardiovascular/respiratory/metabolic diseases

(50)

35

METHODOLOGY Source of Data:

A clinical study of Prospective Double blinding was undertaken with 60 patients aged 18-60 years who are posted for elective unilateral inguinal hernia repair, agreeing and co-operative for inguinal field block.

Study was conducted at Mahatma Gandhi Memorial Government Hospital, Trichy from period June 2015 – June 2016.

Sample Size:

Total of 60 cases.

30 cases of inguinal hernia repair under Field block with Bupivacaine (Group B)

30 cases of inguinal hernia repair under Field block with Ropivaciane (Group R)

Randomization:

Pre-anaesthetic evaluation was done a day prior to surgery and the procedure explained to the patients and consent obtained. The patients are randomised by coin toss method into two groups B-Bupivacaine and R- Ropivacaine.

(51)

36

Blinding technique:

1. Double blinding is done by selecting a researcher who will prepare the local solution and will not participate further in the study.

2. Block is performed by myself and the patients is assessed throughout in the due course of the surgery by me.

3. Observations were recorded by me throughout the study.

On the day of surgery, an intravenous line was secured with 18G iv cannula. Patients were given maintenance I.V fluid 20ml/kg 4hours before the procedure and they were asked to void prior to premedication.

Patients were pre-medicated with injection midazolam 1mg iv before performing the block. Patients were monitored continuously throughout the study every 5min during the procedure and then at an interval of 15min until the patient is shifted to the general ward. The pulse , heart rate ,oxygen saturation , blood pressure and a continuous ECG tracing were monitored.

Onset of block is assessed by pin prick test (22 gauge hypodermic needle) at the skin dermatomes involved in the surgical field from 30^TH seconds.

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Figure-8 VISUAL ANALOG SCALE

TABLE-1 PAIN SCORE WITH VISUAL ANALOG SCALE

VAS PAIN

0-1 NO PAIN

2-4 MILD PAIN

5-7 MODERATE PAIN 8-10 SEVERE PAIN

(53)

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TABLE- 2 ADEQUACY OF THE BLOCK

0 Adequate block requiring no supplementation

1 Analgesia and relaxation adequate with minimal discomfort and are comfortable with local anaesthetic at the neck of sac

2 Patient complains of pain and inadequate relaxation which needs a narcotic supplementation

3 Patient complains of severe pain and inadequate relaxation which warrants general anaesthesia

(54)

39

Adequacy of the block is assessed by the subjective pain perception by VAS score (Fig-8, Table-1), relaxation level by the surgeon‟s verdict and mobility of the patient. Accordingly the adequacy of the block is judged as adequate, inadequate or failed ( Table-2). The patients are supplemented with local infiltration for mild pain, a narcotic supplementation (inj.fentanyl 2mcg/kg iv) for moderate pain and GA for the block failure patients.

The haemodynamics were recorded throughout the study.

At the end of surgery patients were observed in the recovery room for 60min and will be assessed by recovery room nurse every 15 min by verbal rating score (VRS) (Table-3) before discharging to ward.

The surgeon satisfaction were also assessed by taking into account the following criteria cited in (Table-4) and a satisfaction score (Table-5) for the surgeon is also computed.

Postoperative pain relief is defined as time lasting from completing block to the first requirement for analgesia and pain score assessed by VRS (Table-3) by unit intern every 30min. Rescue analgesia was given with I.M. Diclofenac for severe pain and oral paracetamol 1gm for mild to moderate pain.

(55)

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Table – 3 VERBAL RATING SCORE (VRS)

VRS VAS

0 0-1

1 2-4

2 5-7

3 8-10

(56)

41

TABLE-4 SURGEON SATISFACTION SCALE

0 1 2

COMFORTNESS GOOD ADEQUATE INADEQUATE FIELD

CLARITY

CLEAR MESSY BLOODY

PATIENT’S MOVEMENTS

NIL FIDGETY

GROSS MOVEMENTS

Table -5 SURGEON SATISFACTION SCORE SATISFACTION

VERY SATISFIED 0-2 SATISFIED 3-4 DISSATISFIED 5-6

(57)

42

Statistical Analysis 1. Chi square test

2. Independent student „t‟ test

The results are analyzed statistically using SPSS (Statistical presentation system software) for Windows, version16.0 (SPSS, 1999.SPSS Inc.: New York) or EPI info.

Descriptive data included mean, standard deviation and percentage which were determined for both the groups.

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Graph -1 COMPARISON OF BMI

Table-6 COMPARISON OF BMI

Bupivacaine Ropivacaine Total Statistical inference (n=30) (100%) (n=30) (100%) (n=60) (100%)

BMI 18 to

20 16 53.3% 20 66.7% 36 60.0% X²=1.111 Df=1 .292>0.05

Not Significant 21 to

25 14 46.7% 10 33.3% 24 40.0%

(59)

44

RESULTS

1. Out of the 60 patients, 30 belong to the Bupivacaine group ( B group) and 30 to Ropivacaine group (R group).

2. The mean duration of the surgery was 40 min.

3. All of them were males.

4. B group had 53.5% patients and R group had 66.7% patients within the BMI range of 18-20 and within the BMI range 21-25, B group had 46.7% patients and R group had 40% patients. (Graph-1)

5. 76.7% of the patients in B group and 73.3% in group R belong to ASA I and 3.3% of the patients in B group and 26.7% in R group belong to ASA II (Graph-2)

6. Above values shows no significance among the BMI & ASA classification between the two groups. (Table-6 and 7).

(60)

45

Graph-2 COMPARISON OF ASA

Table-7 COMPARISON OF ASA

Bupivacaine % Ropivacaine % Total % SD

ASA X²=.089

Df=1 .766>0.05

Not Significant

Yes 23 76.7% 22 73.3% 45 75.0%

No 7 23.3% 8 26.7% 15 25.0%

(61)

46

Graph-3 COMPARISON OF ONSET OF BLOCK

Table-8 COMPARISON OF ONSET OF BLOCK

Onset in Min Mean S.D T df Statistical inference 0.5 min

Bupivacaine (n=30) .00 .000(a) - - - Ropivacaine (n=30) .00 .000(a) - - -

1min

1.5min

(62)

47

2min

Bupivacaine (n=30) .07 .254 1.439 58 .155>0.05 Ropivacaine (n=30) .00 .000 Not Significant

2.5min

3min

3.5min

4min

4.5min

5min

(63)

48

5.5min

6min

6.5min

7min

7.5min

8min

Bupivacaine (n=30) .07 .254 .584 58 .561>0.05 Ropivacaine (n=30) .03 .183 Not Significant

8.5min

(64)

49

9min

Bupivacaine (n=30) .07 .254 .000 58 1.000>0.05 Ropivacaine (n=30) .07 .254 Not Significant

9.5min

Bupivacaine (n=30) .03 .183 -.584 58 .561>0.05 Ropivacaine (n=30) .07 .254 Not Significant

10min

Bupivacaine (n=30) .00 .000 -1.439 58 .155>0.05 Ropivacaine (n=30) .07 .254 Not Significant

10.5min

11min

11.5min

12min

(65)

50

12.5min

13min

13.5min

14min

14.5min

15min

(66)

51

Table-9 AVERAGE ONSET OF TIME

Onset in Min Mean S.D T df Statistical inference Bupivacaine

(n=30) 5.6833 2.47220 -

8.647 58 .000<0.05 Ropivacaine

(n=30) 11.3333 2.58755 Significant

As seen from the above graph-9,

The average time for onset of block in the Bupivacaine group is 5.7min whereas in the Ropivacaine group it is 11.3min.

(Graph 10) shows, none of the patients in R group had onset of block in the first 5min inferring that it has a late onset compared to B group. None of the patients in B group had onset after 11.5min, the onset starts from 2min in the B group and completes within 11.5min showing its quicker onset.

The statistical inference shows significance of <0.05 (Table-9)

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TABLE-10 ONSET OF BLOCK IN ACTUAL NUMBERS OF PATIENTS

ONSET IN MIN

Bupivacaine Ropivacaine

N % N %

2min 2 6.70% 0 0.00%

2.5min 2 6.70% 0 0.00%

3min 2 6.70% 0 0.00%

3.5min 2 6.70% 0 0.00%

4min 2 6.70% 0 0.00%

4.5min 2 6.70% 0 0.00%

5min 1 3.30% 0 0.00%

5.5min 3 10.00% 1 3.30%

6min 3 10.00% 1 3.30%

6.5min 2 6.70% 0 0.00%

7.5min 3 10.00% 1 3.30%

8min 2 6.70% 1 3.30%

9min 2 6.70% 2 6.70%

9.5min 1 3.30% 2 6.70%

10min 0 0.00% 2 6.70%

10.5min 1 3.30% 0 0.00%

11min 1 3.30% 5 16.70%

11.5min 0 0.00% 1 3.30%

12min 0 0.00% 2 6.70%

12.5min 0 0.00% 2 6.70%

13min 0 0.00% 3 10.00%

13.5min 0 0.00% 1 3.30%

14min 0 0.00% 1 3.30%

14.5min 0 0.00% 2 6.70%

15min 0 0.00% 3 10.00%

(68)

53

Graph-4 COMPARISON OF ADEQUACY OF BLOCK

Table-11 COMPARISON OF ADEQUACY OF BLOCK Rescue

Analgesia Bupivacaine % Ropivacaine % Total % SD

Nil 19 63.3% 17 56.7% 36 60.0% X²=.365

Df=3 .947>0.05

Not Significant

Local 4 13.3% 4 13.3% 8 13.3%

Opioids 4 13.3% 5 16.7% 9 15.0%

GA 3 10.0% 4 13.3% 7 11.7%

(69)

54

Regarding the adequacy of block which is determined by the need for supplements (Graph-4)

In the Bupivacaine group,

1. 63.30% of the patients ( i.e.19 pts) had good analgesia without the need for any analgesia.

2. 13.30% of the patients complained of discomfort and got relief with local infiltration at the neck of the sac (4pts).

3. 13.30% of the patients had inadequate analgesia and relaxation needing narcotic supplementation (4pts).

4. 10.0% of the patients (3 pts) had a failed field block and were converted into GA.

In Ropivacaine group,

1. 56.7% of the patients had excellent analgesia (18pts) with no supplementation.

2. 13.3% of the patients required LA infiltration at the neck of the sac (4pts).

3. 16.7% of the patients needed narcotic supplementation (5pts) to proceed with the procedure.

4. In 13.0% patients technique failed and were converted into GA (4pts).

(70)

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Graph-5 COMPARISON OF SIDE EFFECTS

(71)

56

Graph-6 SIDE EFFECTS OBSERVED

(72)

57

Table-12 COMPARISON OF SIDE EFFECTS Side

effects Bupivacaine % Ropivacaine % Total % SD

No 25 83.3% 28 93.3

% 53 88.3% X²=1.456 Df=1 .228>0.05

Not Significant

Yes 5 16.7% 2 6.7

% 7 11.7%

1. No intraoperative complications were noted.

2. 83.3% of the patients in B group and 93.3% of the patients in R group had no side effects.

3. 16.70% (5 pts ) in the B group and 6.7 % (2 pts) in the R group had side effects.

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Graph-7 COMPARISON OF SURGEON SATISFACTION

(74)

59

Table-13 COMPARISON OF SURGEON SATISFACTION Satisfaction

level Bupivacaine % Ropivacaine % Total % SD

Dissatisfied 5 16.7% 8 26.7% 13 21.7

%

X²=1.218 Df=2 .544>0.05

Not Significan

t

Satisfied 20 66.7% 19 63.3% 39 65.0

% Very

Satisfied 5 16.7% 3 10.0% 8 13.3

%

1. The satisfaction level of surgeons fall mainly in the satisfied level, 66.7% in B group & 63.3% in R group.

2. Only 16.7% (5 surgeons) in B group and 10.0% ( 3 surgeons) in R group expressed dissatisfaction.

3. The statistical inference gives no significance between the two groups.

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Graph- 8 COMPARISON OF TIME REQUIREMENT FOR THE FIRST ANALGESIC

(76)

61

Table-14 – TIME PERIOD FOR THE FIRST REQUIREMENT FOR AN ANALGESIC

Time period for the first

analgesic req Mean S.D t Df Statistical inference 0.5hr

Bupivacaine (n=30) .00 .000 - - - Ropivacaine (n=30) .00 .000 - - -

1hr

1.5hr

2hr

2.5hr

3hr

3.5hr

Bupivacaine (n=30) .07 .254 .000 58 1.000>0.05 Ropivacaine (n=30) .07 .254 Not Significant

4hr

Bupivacaine (n=30) .13 .346 -

1.287 58 .203>0.05

(77)

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Ropivacaine (n=30) .27 .450 Not Significant 4.5hr

Bupivacaine (n=30) .13 .346 .851 58 .398>0.05 Ropivacaine (n=30) .07 .254 Not Significant

5hr

5.5hr

Bupivacaine (n=30) .10 .305 1.795 58 .008<0.05 Ropivacaine (n=30) .00 .000 Significant

6hr

6.5hr

Bupivacaine (n=30) .17 .379 1.736 58 .006<0.05 Ropivacaine (n=30) .03 .183 Significant

7hr

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Table-15 AVERAGE DURATION OF POST OP PAIN RELIEF DURATION

Time period for the first analgesic req (hr)

Mean S.D t df

Statistical inference Bupivacaine (n=30) 4.7167 1.61183 1.421 58 .161>0.05

Ropivacaine (n=30) 4.1500 1.47479

Not Significant

The postoperative analgesic need is the time period between the completion of the block and the first requirement of an analgesic. The block failure patients were excluded from the study (3in B group and 4 in R group). The average duration of pain relief in Bupivacaine group is 4.71 and with Ropivacaine is 4.15 (Table-15).

(Table-16) shows in the Bupivacaine group, post op analgesia is longer as evident from the data showing significant number of patients (12 patients) had analgesia even after 5 hours whereas in R group, only 5 patients had post op pain relief after 5 hrs.

A significance was noted between the two groups regarding the post-operative analgesic duration (Table-14) in the 5.5^th hour and 6.5^th hour. But the average duration does not show a significance.

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Table16- POST OP ANALGESIA DURATION WITH ACTUAL NUMBER OF PATIENTS

Time period for the first Analgesic Req

Bupivacaine Ropivacaine

n % n %

3 hrs 1 3.3% 2 6.7%

3.5hrs 2 6.7% 2 6.7%

4hrs 4 13.3% 8 26.7%

4.5hrs 4 13.3% 2 6.7%

5hrs 4 13.3% 7 23.3%

5.5hrs 3 10.0% 0 0

6hrs 3 10.0% 4 13.3%

6.5hrs 5 16.7% 1 3.3%

7hrs 1 3.3% 0 0

(80)

65

Table- 17 COMPARISON OF HEART RATE Mean S.D Statistical inference

Age t=-.687 Df=58

.495>0.05 Not Significant Bupivacaine (n=30) 44.07 11.104

Ropivacaine (n=30) 45.83 8.667 HR PRE OP

Bupivacaine (n=30) 74.07 9.951 t=-1.106 Df=58 .273>0.05 Not Significant Ropivacaine (n=30) 77.10 11.254

HR PRE 2min

Bupivacaine (n=30) 80.93 14.458 t=-.221 Df=58 .826>0.05 Not Significant Ropivacaine (n=30) 81.67 11.071

HR PRE 5min

Bupivacaine (n=30) 84.03 17.312 t=.043 Df=58 .966>0.05 Not Significant Ropivacaine (n=30) 83.87 12.684

HR PRE 10min

HR PRE 15min

(81)

66

Graph-9 COMPARISON OF HEART RATE

65 70 75 80 85 90

HR PRE OP HR PRE 2min

HR PRE 5min

HR PRE 10min

HR PRE 15min

HR PRE 20min

HR PRE 25min

HR PRE 30min

HR PRE 40min

HR PRE 50min

HR PRE 60min Bupivacaine Ropivacaine

(82)

67

Table-18 COMPARISON OF THE MEAN SYSTOLIC BLOOD PRESSURE

BP PRE 2min

Bupivacaine (n=30) 118.43 11.670 t=-1.129 Df=58 Ropivacaine (n=30) 122.57 16.307 .264>0.05

Not Significant BP PRE 5min

BP PRE 10min

BP PRE 15min

BP PRE 20min

BP PRE 25min

(83)

68

BP PRE 30min

BP PRE 40min

BP PRE 50min

Bupivacaine (n=30) 112.40 4.882 t=.193 Df=58 .848>0.05 Not Significant Ropivacaine (n=30) 112.13 5.800

BP PRE 60min

(84)

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Graph-10 COMPARISON OF THE MEAN SYSTOLIC BLOOD PRESSURE

105 110 115 120 125 130

BP PRE OP BP PRE 5min

BP PRE 10min

BP PRE 15min

BP PRE 20min

BP PRE 25min

BP PRE 30min

BP PRE 40min

BP PRE 50min

BP PRE 60min Bupivacaine Ropivacaine

(85)

70

The heart rate ( HR) and blood pressure (BP) in both groups were observed from the pre-operative period till the patient was discharged to the general ward (Table-17 & Table-18)

1. As seen from above (Graph-9), the mean value of the heart rate in both groups are computed. It is seen that there is no significant change in HR from the baseline in both the groups. Also there is no significance between both the groups.

2. Graph-10 shows the mean systolic BP in both the groups. Only the systolic BP is taken into account for convenience. It is found that the BP is stable throughout the study with local anaesthesia. It is also seen that there is no significance between the two groups of study.

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71

DISCUSSION

Inguinal hernia repair is one of the commonest surgeries in the world. In the advent of administering anaesthesia for the surgical correction, the technique employed should be cost effective, with adequate analgesia , minimal side effects and a speedy recovery³².

The advantage of field block is its safety, simplicity, cost effectiveness, easy technique, prolonged analgesia, early ambulation with no or minimal side effects ³³. Hence it can be employed in the day care surgeries reducing the need for post-operative narcotic supplements³⁴. Since local anaesthetics do not hinder the respiratory and cardiovascular system in allowed dosage, good respiratory stability and haemodynamic stability were maintained.

Large series of studies are available in surgical and anaesthesia literature regarding the usage of local infiltration alone or combined with ilioinguinal nerve block for inguinal hernia repair. Most of these were compared with GA or neuraxial anesthesia or monitored anaesthesia care under deep sedation.

The advantage of field block over local anaesthesia is the almost complete coverage of the skin dermatomes involved in the surgical area;

which is sometimes spared in local infiltration. The precise blocking of the nerves in field block provides adequate analgesia, avoiding multiple