TIME TAKEN TO ACHIEVE T4 LEVEL (Min)

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FACTORS AFFECTING THE SPREAD OF SPINAL ANESTHESIA IN PARTURIENTS UNDERGOING CASEAREAN SECTION – A

PROSPECTIVE OBSERVATIONAL STUDY

TAMIL NADU MEDICAL COUNCIL Regn. No.:110348

A DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE M.D. BRANCH X ( ANAESTHESIOLOGY) OF THE TAMIL NADU DR. M.G.R MEDICAL UNIVERSITY EXAMINATION

TO BE HELD IN MAY 2020

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CHRISTIAN MEDICAL COLLEGE, VELLORE

BONAFIDE CERTIFICATE

This is to certify that this dissertation titled ‘FACTORS AFFECTING THE SPREAD OF SPINAL ANESTHESIA IN PARTURIENTS UNDERGOING CASEREAN SECTION’ is the bonafide work of Dr.SheetalBabu(Emp. No 33891) completed under my supervision in the Department of Anaesthesiology, Christian Medical College, Vellore in partial fulfilment of the requirements for the M.D.

Anaesthesiology Examination Branch X of the Tamil Nadu Dr. M.G.R Medical University, Chennai to be held in May 2020. Certified further that to the best of my knowledge the work reported here is not part of any other dissertation on the basis of which a degree was awarded to any previous candidate.

Dr.Sajan Philip George Professor,

Department of Anaesthesiology,

Christian Medical College and Hospital, Vellore – 632004,

Tamil Nadu

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This is to certify that this dissertation titled ‘FACTORS AFFECTING THE SPREAD OF SPINAL ANESTHESIA IN PARTURIENTS UNDERGOING CASEREAN SECTION’is the bonafide work of Dr.SheetalBabu(Emp. No 33891) completed under the supervisionof Dr Sajan Philip George, Professor, Department of Anaesthesiology, Christian Medical College, Vellore in partial fulfilment of the requirements for the M.D. Anaesthesiology Examination Branch X of the Tamil Nadu Dr. M.G.R Medical University, Chennai to be held in May 2020. Certified further that the work reported here is not part of any other dissertation on the basis of which a degree was awarded to any previous candidate.

Dr. Raj Sahajananadan Professor and Head

Department of Anaesthesiology,

Christian Medical College and Hospital, Vellore – 632004,

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This is to certify that this dissertation titled ‘FACTORS AFFECTING THE SPREAD OF SPINAL ANESTHESIA IN PARTURIENTS UNDERGOING CASEREAN SECTION’is the bonafide work of Dr.SheetalBabu(Emp. No 33891) completed under the supervision of Dr Sajan Philip George, Professor, Department of Anaesthesiology, Christian Medical College, Vellore in partial fulfilment of the requirements for the M.D. Anaesthesiology Examination Branch X of the Tamil Nadu Dr. M.G.R Medical University, Chennai to be held in May 2020. Certified further that the work reported here is not part of any other dissertation on the basis of which a degree was awarded to any previous candidate.

Dr. Anna. B. Pulimood, Principal,

Christian Medical College, Vellore – 632004,

Tamil Nadu

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CHRISTIAN MEDICAL COLLEGE, VELLORE DECLARATION

This is to certify that this dissertation titled ‘FACTORS AFFECTING THE SPREAD OF SPINAL ANESTHESIA IN PARTURIENTS UNDERGOING CASEREAN SECTION’is a genuine record of research done by me,Dr.SheetalBabu(Emp. No 33891)completed under the supervision of Dr Sajan Philip George, Professor, Department of Anaesthesiology, Christian Medical College, Vellorein partial fulfilment of the requirements for the M.D. Anaesthesiology Examination Branch X of the Tamil Nadu Dr. M.G.R Medical University, Chennai to be held in May 2020 and to the best of myknowledge the work reported here is not part of any other dissertation on the basis of which a degree was awarded to any previous candidate of any university or institution.

Dr.SheetalBabu

Post Graduate Resident,

Department of Anaesthesiology, Christian Medical College, Vellore – 632004,

Tamil Nadu

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ACKNOWLEDGMENT

I would like to thank God for giving me the strength and theresources to complete my dissertation.

My guide, Dr.Sajan Philip George has been a source of constant motivation throughout this study.

I would also like to Miss Dona for the statistical help and Miss Poornima for her valuable inputs regarding data analysis.

My sincere thanks to all the Operation Room staff and technicians who helped me throughout my journey.

I want to thank my family especially my parents and brother for their prayers, moral support and technical support during this period of study.

I would like to make special mention of all my good friends who provided me motivation and courage and also valuable resources to enhance the impact of my thesis.

Last but not the least, I would like to thank all my patients, who despite their pain, willinglycooperated with me throughout my study.

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TABLE OF CONTENTS

The obstetric patient’s anatomical and physiological changes require a wider safety and efficacy in analgesic and anesthetic techniques used. Regional anaesthesia is the preferred technique used in the obstetric population owing to the various physiological changes that occur in pregnancy. (1) Most common regional techniques include spinal anaesthesia, epidural anaesthesia or combined spinal epidural (CSE) anaesthesia.

Single dose spinal anaesthesia is the most widely practiced technique in elective and emergency cases. (2) Hyperbaric bupivacaine is the drug used for spinal anaesthesia in our institution. Patient demographic variables are frequently used to predict spinal anaesthesia spread, but the results have been highly unreliable especially in parturients due to increased abdominal pressure and decreased lumbosacral subarachnoid space volume. Increased height of block can lead to hypotension and high spinal anaesthesia whereas low level of blockade can lead to patient discomfort. (3) The aim of this study is to investigate the effect of height, weight, body mass index, abdominal girth and vertebral column length on the spinal spread of bupivacaine and determine the most reliable predictor. (4)

AIM

To study the factors affecting the spread of spinal anaesthesia in pregnant women who underwent caesarean section

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OBJECTIVES

I. To measure time taken to achieve a T4 level blockade

II. To measure the different predictors, (namely height, weight, BMI, abdominal girth, vertebral column length) affecting the spread of spinal anaesthesia.

III. To compare the effect of different predictors on the spread of spinal anaesthesia with respect to the time taken to achieve T4 level blockade

IV. To decide whether the volume of hyperbaric bupivacaine used in our current practice in our institution is adequate or requires modification.

INCLUSION CRITERIA

All pregnant women posted for elective and emergency caesarean section.

EXCLUSION CRITERIA

1) Patients not giving consent for the study 2) ASA III and IV

3) Any contraindications to spinal anaesthesia (coagulopathy, local anaesthetic allergy or localised skin infection)

4) Caesarean sections planned under general anaesthesia.

5) Patients who are uncooperative.

MATERIALS AND METHODS

This prospective observational study enrolled a total of 180 term parturients(ASA I &

II) undergoing caesarean section. All consenting patients who fulfil the inclusion criteria were assessed pre operatively in the ward. The following parameters will be

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recorded - height (in cm), weight (kg), BMI, abdominal girth (at the level of umbilicus at end expiration in cm) and vertebral column length in cm (this was measured from the middle of the C7 vertebra to the sacral hiatus while the parturient was sitting on a flat surface with a straight back). These were recorded by the principal investigator to avoid any bias in measurement.The patient was taken to the operating room, standard monitors connected and intravenous access established. Preloading with Ringer’s lactate 500 mL wasdone. The L3-L4 interspace was identified and the spinal was administered with a 25- gauge Whitacre needle. The timer was started once the drug was administered. Parturientswere then positioned in a 10° left-lateral tilt with a wedge under the right hip and a10° Trendelenburg position. (13)

The spread of the drugwas assessed in the midclavicular lines on both sides using ice for loss of temperature sensation. Loss of temperature sensation at the T4 dermatome level was assessed every 5 minute after the drug was administered into the spinal space. The time taken for loss of temperature sensation at T4 level was noted.

General anaesthesia was administered if spinal administration failed to produce a satisfactory level of surgical anaesthesia.

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INTRODUCTION

The obstetric patient’s anatomical and physiological changes require a wider safety and efficacy in analgesic and anesthetic techniques used. Regional anaesthesia is the preferred technique used in the obstetric population owing to the various physiological changes that occur in pregnancy. (1) Most common regional techniques include spinal anaesthesia, epidural anaesthesia or combined spinal epidural (CSE) anaesthesia.

Single spinal anaesthesia is the most widely practiced technique in elective and emergency cases. (2) Hyperbaric bupivacaine is the drug used for spinal anaesthesia in our institution. Patient demographic variables are frequently used to predict spinal anaesthesia spread, but the results have been highly unreliable especially in parturients due to increased abdominal pressure and decreased lumbosacral subarachnoid space volume. Increased height of block can lead to hypotension and high spinal anaesthesia whereas low level of blockade can lead to patient discomfort. (3) The primary aim was to measure the different predictors, (namely height, weight, BMI, abdominal girth, vertebral column length) affecting the spread of spinal anaesthesia and time taken to achieve T4 level and for the level to fall from the highest point. The secondary aim was to compare the parameters with the time and has the greatest effect on the spinal anesthesia spread. As a corollary we also wanted to infer whether the volume of drug used in our institution was adequate or required to be modified. (4)

REVIEW OF LITERATURE

Anaesthetic technique preferred during Caesarean delivery requires a detailed understanding of the physiologic changes associated with pregnancy, labour and delivery. It starts early in the first trimester, peaks at term and during labour and return

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to pre-pregnancy state in 2-3 weeks postpartum. These changes are a result of alterations in the maternal hormone balance, biochemical shifts related to larger metabolic demands of the fetus and placenta, and mechanical forces from the gravid uterus. Although each organ system is affected by pregnancy, the changes to the cardiovascular, respiratory and gastrointestinal systems have specific anaesthetic implications. These changes have significant anaesthetic implications in deciding the anaesthetic technique for both obstetric and non – obstetric surgeries.

RESPIRATORY CHANGES Table -1

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LoMauro A, Aliverti A. Respiratory physiology of pregnancy: Physiology masterclass. Breathe (Sheff) 2015;11:297-301.

Figure (a)

23^rd edition William Obstetrics Cunningham. Leveno.Bloom.Hauth.Routh.Spong

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CARDIOVASCULAR CHANGES Table -2

Mushambi, M. (2016).Physiology of pregnancy. In C. Mowatt (Author) & T.

Lin, T. Smith, & C. Pinnock (Eds.), Fundamentals of Anaesthesia (pp. 512- 530). Cambridge: Cambridge University Press.

doi:10.1017/9781139626798.027

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GASTROINTESTINAL CHANGES Table -3

Mushambi, M. (2016).Physiology of pregnancy. In C. Mowatt (Author) & T. Lin, T.

Smith, & C. Pinnock (Eds.), Fundamentals of Anaesthesia (pp. 512-530). Cambridge:

Cambridge University Press. doi:10.1017/9781139626798.027

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HEMATOLOGICAL CHANGES Table - 4

Mushambi, M. (2016).Physiology of pregnancy. In C. Mowatt (Author) & T. Lin, T.

Smith, & C. Pinnock (Eds.), Fundamentals of Anaesthesia (pp. 512-530). Cambridge:

Cambridge University Press. doi:10.1017/9781139626798.027

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Table -5

Chapter 41 ObstetricAnaesthesia …..FerneR.Braveman, Barbara M. Scavone, Marcelle Blessing, Cynthia Wong…South Asian Edition of Clinical Anesthesia, 8^th Edition

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ELECTROCARDIOGRAM CHANGES Table -6

Sunitha M, Chandrasekharappa S, Brid SV. Electrocardiographic QRS axis, Q wave and T-wave changes in 2^nd and 3^rdtrimester of normal pregnancy. J

ClinDiagn Res 2014;8:BC17-21

NORMAL LABOUR

What constitutes normal labour?

• Contractions every 3 min lasting 45 sec each

• Progressive dilatation of the cervix

• Progressive descent of the presenting part

• Vertex presentation head flexed and anterior occiput

• Labour 4h – 18h

• Delivery of live healthy baby and complete placenta and membranes

• No complications

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FIRST STAGE OF LABOUR

Initially cervix effaces and then cervical dilatation begins at a rate of 1 cm/hr for a primiparous and 2 cm/hr for a multigravida woman. The woman is monitored every 4 hrs and the following details are recorded on the partogram : fetal heart rate every 15 min, maternal pulse rate every 30 min, blood pressure every 30 min, temperature every 4 hrs, urine analysis at each emptying of the bladder.

SECOND STAGE OF LABOUR

This stage begins at full dilatation of the cervix and ends at the delivery of the baby. At full dilatation of the cervix, the contractions intensify and there is a strong urge to push. In normal labour, Ferguson’s reflex occurs, where the vaginal distension by the presenting part causes increase in circulating oxytocin with consequent increase in intensity of the uterine contracts at full dilatation. The second stage of labour can be classified into active and passive stage and this is especially significant when epidural analgesia is used. With epidural analgesia, the normal sensation produced at the start of second stage of labour is abolished and hence the active stage begins only at the appearance of the vertex or when the woman has a strong urge to push. A normal active second stage of labour should not exceed 1 hras it causes fetal acidosis. At

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thedelivery of the anterior shoulder, IM oxytocin is given to augment the uterine contractions and to hasten the delivery of the placenta.

THIRD STAGE OF LABOUR

This stage is the completion of delivery of the placenta, membranes and the contraction of the uterus. It can be managed passively but is usually managed actively with oxytocin to reduce the risk of postpartum haemorrhage. In this stage there is a redistribution of the former placental blood flow which is about 15%. This is potentially dangerous in patients with prior cardiac disease as it can precipitate heart failure.

The anaesthetist should communicate with the obstetrician and understand how compromised the fetus is prior to giving anaesthesia to the patient. The degree of urgency and the anaesthetic modality planned depends on the maternal and the fetal condition. The urgency of Caesarean section delivery can be classified and 4 grades are proposed. This classification is applicable only at the time decided to take the patient up for Caesarean section:

Grade 1 – Emergency: immediate threat to mother or fetus

Grade 2 – Urgent: Maternal or fetal compromise not immediately life threatening.

Grade 3 – Scheduled: needing early delivery, no compromise to maternal or fetal condition

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Grade 4 – Elective: As per patient’s or treating medical team’s convenience.

PREOPERATIVE RECOMMENDATIONS:

• Substitute oral feeds by parenteral whenever possible during labour.

• Wider use of local anaesthesia where feasible

• If planned for general anaesthesia, alkalinisation and emptying of the stomach content prior to surgery

• Anticipate the dangers of aspiration during induction and emergence under general anaesthesia. Hence if planning for the same, to wait till the return of laryngeal reflexes.

PAIN PATHWAYS IN LABOUR AND CASEAREAN SECTION Pain pathways

The afferent nerve supply of the uterus and cervix is via A delta& C fibres of the thoracolumbar and sacro- sympathetic outflow. The pain of the first stage of labour is referred to segments T10-L1 (associated with uterus and the cervix). Second stage of labour pain associated with distension of the birth canal and the perineum is referred to S2-S4 segments. For Caesarean section anaesthesia all the layers up to the uterus including the perineum including theroots. (13)

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Figure (b)

Chapter 12. Spinal, epidural, caudal anesthesia: anatomy, physiology, technique.

Cynthia A. Wong, Naveen Nathan, David L Brown..Chestnut’s obstetric anesthesia – Principles and Practice.

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Figure (c)

ANATOMY OF SPINAL AND EPIDURAL SPACE

Anatomical configuration of the spinal column in the supine position. II. Comparison of pregnant and non-pregnant women .Br. J. Anesthesia Hirabayashi. Y. Shimizu,

Fukuha H.1995: 75: 6-8)

Spinal cord extends cephalad with the brainstem through the foramen magnum and caudally terminates at the lower border of L1 vertebrae or L2 vertebrae at the conusmedullaris. The conusmedullaris is attached to the coccyx by a neurofibrous band called filumterminale surrounded by the nerves of the lower lumbosacral roots known as caudaequina.

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Figure (d)

Netter’s Atlas of Neuroanatomy and neurophysiology. Special Edition

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Figure (e)

Cynthia A. Wong, Naveen Nathan, David L Brown..Chestnut’s obstetric anesthesia – Principles and Practice.

Spinal cord is surrounded by three membranes – the pia mater, the arachnoid mater and the dura mater. The pia mater, a highly vascular structure, closely invests the spinal cord and distally ends as the filumterminale. The arachnoid mater, a nonvascular membrane is attached to the dura mater, the third and outermost layer.

The dura mater, the outermost fibroelastic membrane is a direct extension of the cranial dura mater and extends from foramen magnum to S2.

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Figure (f)

The spinal cord is shown along with the dorsal root ganglia and ventral rootlets, spinal nerves, sympathetic trunk, rami communicantes and pia, arachnoid,anddura mater.

Chapter 13 Spinal Anaesthesia ….Text Book of Regional Anaesthesia and Acute Pain Management.AdmirHadzic

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Figure (g)

Aston-Bird G.Atlas of Regional Anaesthesia. In Miller RD (ed).Miller’s Anesthasia.Philadelphia, Elsevier, 2005

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Figure (h)

Neural blockade in Clinical Anaesthesia and management of pain.

Philadelphia, “Lippincott-Raven, 1998, PP 203-242

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There are three spaces within the vertebral canal surrounding the spinal cord. The subarachnoid space lies between the pia mater and the arachnoid space and continues till S2 level. It contains the cerebrospinal fluid (CSF), the spinal nerves, a trabecular network between the two membranes, blood vessels and the dentate ligament - extensions of the pia mater which offers lateral support to the spinal cord.

Unintentional subdural injection may explain failed spinal anaesthesia and the rare slow – to – develop cases of high spinal anaesthesia, thesubdural space, a potential space exists between the dura and the arachnoid mater. The epidural space, external to the dura mater, extends from the foramen magnum to the sacral hiatus. It is a segmented and discontinuous space. The boundaries of the epidural space are anteriorly, the posterior longitudinal ligament, laterally, the pedicles and the intervertebral foramina and posteriorly by the ligamentumflavum. The contents of this space are nerve roots, blood vessels, lymphatics, areolar tissue and fat.

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Figure (i)

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Figure (j)

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DERMATOMES FOR SPINAL ANESTHESIA

A dermatome is defined as a skin area innovated by sensory fibres from a single spinal nerve. The dermatomes T10 corresponds to umbilicus, T6 corresponds to the xiphoid, T4 the nipples. To achieve surgical anesthesia the extent of the spinal anaesthesia must reach the required dermatome level for that surgery.

Figure (k)

Chapter 13 Spinal Anaesthesia ….Text Book of Regional Anaesthesia and Acute Pain Management.AdmirHadzic

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Table -7

Chapter 17 Spinal and Epidural Anaesthesia.. Kenneth Drasner and Merlin D Larson..Basics of Anesthesia 6^th Edition

THE AIRWAY IN PREGNANCY

Incidence of difficult intubation in term parturients is approx. 1 in 300 compared to non pregnantpopulation where it is 1 in 2200.

The various physiological and anatomical changes in pregnancy may contribute to the difficulty observed in the management of maternal airway. Airway edema is the one of

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the major causes of difficult airway in pregnancy. The increase in maternal blood volume and higher levels of estrogen lead to capillary engorgement, mucosal edema and increased tissue friability in the nasal and oral pharynx,laryngopharynx and trachea. This is associated with complications like difficulty with nasal breathing, voice changes, an increased likelihood of nasal bleeding which is worsened by the distorted laryngeal anatomy and decrease in the laryngeal opening size caused by airway edema leading to trauma during airway instrumentation which necessitates the use of a smaller size endotracheal tube. In addition, during intubation, the enlarged tongue makes it difficult for its displacement into the mandibular space. Airway edema is significantly worsened during labor and delivery and in conditions like respiratory tract infection, eclamptic state, overzealous administration of intravenous fluids and straining during second stage of labor.

The other risk factors for airway related complications during pregnancy are decreased functional residual capacity, weight gain, enlarged breasts, full dentition, decreased lower esophageal sphincter tone and decreased gastric emptying during labor.

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The following table highlights the changes:

Table -8

LoMauro A, Aliverti A. Respiratory physiology of pregnancy: Physiology.

Breathe (Sheff) 2015;11:297-301.

ANESTHESIA IN PREGNANCY

In 1847, James Young Simpson used diethyl ether to anesthetize a parturient with deformed pelvis. Since then systemic drugs were used to reduce the pain of child birth.

In view of the adverse neonatal effects and the desire of expectant mothers to actively participate in child birth, heavy sedation has been abandoned during labor and general anaesthesia is deferred except for complicated deliveries. (15)

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Table -9

Chapter 26.Anesthesia for Cesarean delivery.Lawrence C.Tsen..Chestnut’s Obstetric Anesthesia. Fourth Edition

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Caesarean delivery is the Birth of an infant through abdominal incision ( Laparotomy) and uterine incision (Hysterotomy). The most common indications for Caesarean section delivery include failed induction, non-reassuringfetal status, maternal condition deterioration, cephalopelvic disproportion, malpresentation, and cord prolapse, prematurity and prior uterine surgery involving the corpus. The choice of anaesthesia depends on the urgency of the procedure in addition to maternal and fetal condition.

Before initiation of any anesthetic technique, resuscitation equipments should be checked and made available. (16)

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Anesthesia technique preference for Caesarean delivery:

Table -10

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REGIONAL ANESTHESIA FOR PARTURIENTS

Caesarean deliveries account for more than 17.2% of child births for India during the period from Jan 2015 to Dec 2016. (17)

Regional techniques have several advantages. They reduce the risk of aspiration, reduce the use of depressant anaesthetic drugs, allow the mother to remain awake during childbirth and breastfeed the neonate immediately, reduce the operative blood loss, decrease the risk to neonate. The main disadvantage is hypotension which will be more profound because sensory block must extend to at least the T4 dermatome.

However, the incidence can be reduced by preloading or co-loading with crystalloid.

SPINAL ANESTHESIA

Spinal anaesthesia is the preferred mode of anaesthesia in patients undergoing Caesarean section if no other contraindications are obvious. It is more rapid in onset and more reliable in providing surgical anaesthesia from the mid-thoracic level to the sacrum with a failure rate of <1% even though there is a risk of profound hypotension which can be improved with avoidance of aortocaval compression (left uterine displacement), hydration and appropriate use of vasopressors. (8, 9) A typical spinal anaesthetic includes a local anaesthetic such as bupivacaine or ropivacaine for the surgical anaesthesia with morphine added for post-operative pain control. Although either isobaric or hyperbaric preparations of local anaesthetic can be used as a spinal

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anaesthetic, hyperbaric solutions containing 8% dextrose are typically used to facilitate a more controlled block distribution. For a caesarean section, a T4 level of blockade is necessary for adequate anaesthesia. (9) A single dose spinal normally provides adequate surgical anaesthesia for >90 min but duration can be highly variable and depends on the agent used. The most commonly used drug is Bupivacaine with typical doses between 10 and 15 mg. Although successful Caesarean deliveries have occurred with doses <5 mg, logistic regression studies examining doses of intrathecal bupivacaine that provided a 95% rate of effective anaesthesia (ED95) for Caesarean delivery when combined with fentanyl (10 mcg) and morphine (0.2 mg) were 11.2 and 13.0 mg for hyperbaric and isobaric bupivacaine, respectively. (10-12)

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Drugs used for spinal anaesthesia during Caesarean:

Table -11

Although spinal anaesthesia is one of the most reliable forms of anaesthesia, occasional failures are seen. This has an adverse effect on the well- being of the parturient and the neonate. Broadly speaking any discomfort during the Caesarean section which warrants the use of additional measures to continue surgery is regarded as failed spinal. It is defined as ‘failure to provide satisfactory surgical conditions and/

Drugs Used for Spinal Anesthesia forCesarean Del

ive

ry

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or maternal comfort and satisfaction during caesarean section with or without conversion to general anaesthesia.’ The maximum time limit after which it is deemed as failed spinal is 15-20 min. (2)

EPIDURAL ANESTHESIA

This was the anaesthesia of choice till pencil- point needles were introduced. The problems faced was that the onset of block was longer and the spread of the block was patchy with sacral root sparing, The advantage is the excellent cardiovascular stability hence this is the anaesthesia of choice for patients with heart disease or pre-eclampsia.

When the epidural is in place anaesthesia can be achieved with local anaesthetic combined with an opioid. It is essential to check the extent of the block level to ensure that good anaesthesia has been achieved.

The standard prescription for an epidural anaesthetic:

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Table -12

COMBINED SPINAL EPIDURAL ANESTHESIA

There are various techniques for this though the ‘needle though needle’ technique is the most popular. It allows increased flexibility and more cardiovascular stability. The disadvantages are delay in starting the surgery, failure of the block and epidural may not achieve profound anaesthesia.

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In CSE, the same drug dose is used as for spinal anaesthesia and epidural ismainly for postoperative analgesia. Another technique is to use a small dose intrathecal local anaesthetic for sequential block followed by epidural top – up to achieve full anaesthesia. This is a better techniquesince it provides good cardiovascular stability as the onset of block is slower and excellent sacral block is achieved with the spinal anaesthetic.

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Table -13

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EMERGENCY CASEAREAN SECTION

Regional anaesthesia is preferred for emergency caesarean section also.

TOPPING UP EPIDURAL

A labour epidural may be topped up within 10-20 min with either lidocaine 2% with 1 in 200,000 epinephrine or bupivacaine 0.5 % with 1 in 200, 000 epinephrine. Sodium bicarbonate (1 – 2 ml of 8.4 % sodium bicarbonate) to increase the pH of the solution and to hasten the onset of action.The top up be incrementally and the patient should be monitored throughout and she should be explained what she would experience and reassured.

SPINAL ANAESTHESIA FOR EMERGENCY

This is for women who have no epidural in situ and who requires an emergency caesarean section. The procedure has to be explained to them as fully as possible in the time available and in detail later on. Follow – up is important in these cases.

Sometimes general anaesthesia may be given when indicated.

POST DELIVERY ANALGESIA

The anaesthetist is involved in the pain relief in women post delivery. Intrathecal and epidural opioids is the most routine practise nowadays. Combined with wound site local anaesthetic infiltration prior to surgical closure, NSAIDs, paracetamol and other analgesics enable women to mobilize earlier after surgery. Follow clear postoperative guidelines with close monitoring including the sedation scores. If good pain control is not achieved, other options available are epidural analgesia and PCA morphine.

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COMPLICATIONS OF REGIONAL ANAESTHESIA

• Hypotension

Small decrease in pressures are insignificant and may cause an improved uteroplacental circulation but a sudden drop in blood pressure of 25% or more from the baseline causes unpleasant dizziness and nausea in about 50% of the patients and should be treated with vasopressors until arterial pressure normalizes. Meanwhile, ensure there is no aortocaval compression and normovolemia is maintained.

• Post-dural puncture headache

This is mainly during epidural catheter insertion or later by the migration of the catheter into the intrathecal space. The complaints are usually occipital headache which radiates anteriorly and is aggravated by sitting and is associated with nausea, photophobia and occasionally diplopia. A thorough history and examination should be done and other differentials should be ruled out like meningitis, intracranial bleed and cerebral space-occupying lesions.

This is usually managed by injecting epidural normal saline around 60 ml or infusion over 12-24 hrs of normal saline postpartum, intravenous and oral fluids, adequate bed rest, analgesia for pain relief, caffeine 0.5% infusion (cerebral vasoconstriction), antidiuretic hormone. If no response, blood patch injected under aseptic condition in the epidural space to seal the CSF leak.

• Shearing of catheter

This also pertains to epidural anaesthesia.

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• High spinal anaesthesia

This occurs with excessive cephalad spread of local anaesthetic in the subarachnoid space. Other causes are unintentionalintrathecal administration of epidural drugs or catheter migration. Emergency control of airway and management of hemodynamic instability might be required.

• Systemic toxicity of local anaesthetic

Unintended intravascular injection or drug accumulation after repeated epidural injection or rapid absorption of local anaesthetic from highly vascular sites can result in high serum levels of local anaesthetic. IV access, airway resuscitation equipment, emergency drugs and suction equipments should be readily accessible when any block is performed.

• Backache

Spinal or Epidural may contribute to short-term back pain if it causes hematoma, infection causing abscess or meningitis or mild local bruising from poor technique. But long term backache is not caused by neuraxial anaesthesia.

• Hematoma

This is a potentially disastrous complication with epidural. The estimated incidence is < 1/250, 000. The signs of an epidural hematoma are new onset, severe back pain, prolonged profound motor weakness > 6 hrs after stop of

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MRI scan is warranted and if confirmed neurosurgical evacuation of the hematoma within 8 hrs of onset of symptoms result in good outcome.

• Abscess or meningitis

An abscess gives rise to a space occupying lesion in the epidural space resulting in compression of the spinal cord and its nutrient arteries leading to paraparesis or paraplegia. Another complication is bacterial or viral or fungal meningitis if adequate aseptic precautions are not followed.

• Neurological deficit

This is caused either by the drug used for the procedure or trauma from the needles or catheters. Persistent numbness or weakness more than one week’s duration is rare with an incidence of 1 / 150,000. This is due to nerve root injury. The patients need to be reassured that the symptoms will resolve over 3-6 months and regular follow up should be planned. Several nerve roots may be injured during delivery: Lateral popliteal nerve by stirrups causing foot drop, Lateral cutaneous nerve of the thigh by groin pressure from lithotomy present leading to anterolateral thigh numbness, Femoral nerve or sciatic nervelithotomy position causing weak quadriceps and loss of knee reflex or back of leg pain with loss of ankle reflex, Sacral plexus or obturator nerves injury.

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METHODOLOGY

DESIGN AND SUBJECTS

This prospective observational study was conducted after approval from Institutional Review Board. After obtaining written and signed consent,180 term stable parturients(ASA I & II) undergoing caesarean sections were recruited in the study.

Excluded from the study were non consenting or uncooperative parturients, ASA III and ASA IV patients, patients who had any contraindications to central neuraxial blockand patients who were considered for general anaesthesia.

STUDY PROTOCOL

All consenting patients who fulfilled the inclusion criteria were assessed pre operatively in the ward. A pre-procedure history and physical examination with a note of allergies, baseline vital signs and assessment of airway, body habitus and haematological system were noted. Parturient demographic variables, including age, parity and gravidity, gestational age number of fetuseswere also noted. The following parameters were specifically noted – height (in cm), weight (kg), BMI, Abdominal girth (at level of umbilicus at end of expiration in cm) and vertebral column length in cm (from the middle of the C7 vertebra to the sacral hiatus while the parturient sat on a flat surface with a straightened back). These weremeasured by principal

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Fig .Flow diagram outlining study procedure

Assessed for eligibility (n=186)

Enrolled and completed study (n=182)

Studied height, weight, BMI, abdominal circumference, vertebral column length and time taken to achieve T4 and level to fall in each patient and found the correlation

Excluded (n=4)

• Conversion to general anesthesia (n=3)

• Non consenting (n=1)

Includedin analysis (n=178)

Level never achieved (n=4)

Data analysed by Pearson correlation coefficient

(56)

The patient was taken to the operating room, standard monitors were connected and intravenous access was established and preloaded with Ringer’s lactate 500. The L3- L4 interspace was identified and skin infiltration with 2% lidocaine was given. Then spinal anaesthesia was administered with a 25- gauge Whitacre needle. The timer was started once the drug was administered. Parturientswere then positioned in a 10° left- lateral tilt and a10° Trendelenburg position.

MEASUREMENTS

The spinal spread was assessed in bilateral midclavicular lines using ice for loss of temperature sensation. The dermatome corresponding to the loss of temperature sensation was noted every 5 min from the time of administration of the drug and the respective vitals were also noted. The time taken to achieve the highest dermatome level and the corresponding vitals were also noted. After the delivery of the baby, the baby’s weight was also noted.

General anaesthesiawould be administered if spinal administration failed to produce a satisfactory level of surgical anaesthesia and the parturient excluded from the study.

(57)

STATISTICAL ANALYSIS

Sample size was calculated based on the study by Ting et. al (2018) in which the correlation coefficient between VCL and spinal anaesthesia-induced loss of temperature sensation (vertebral column length) was 0.68. Assuming in this study, the population correlation coefficient as 0.55 with 80% power and 5% alpha error, the required number of the study was estimated as 180. To account for loss to follow up, we intended to recruit 185 and more.Statistical analysis was performed with SPSS(version 21.0, SPSS Inc., Chicago, IL, USA). The linear categorical variables were reported as absolute numbers (n), percentages (%) and relative frequencies (%) whereas continuous variables were reported as means (standard deviation) or medians (interquartile ranges) as appropriate. Descriptive statistics for continuous variables such as age, height, weight, BMI, abdominal girth and VCL was expressed as mean values ± the standard deviation (SD) (median and interquartile range was used for variables having skewed distributions).

Pearson correlation coefficient was used to assess the strength of the predictor variables with spinal anaesthesia spread. P value < 0.05 was considered to be statistically significant. Pearson’s correlation coefficient is a test used to measure the statistical association between two continuous variables. It is based on the method of covariance hence it is one of the best methods which gives information about the strength and direction of association or correlation between variables.

(58)

The sig (2-tailed) is the two tailed p – value. This tells if the correlation was significant or not at a chosen alpha level. This study has 5% alpha error, hence if the p – value is </ = 0.05 the correlation is statistically significant.

RESULTS

During the study period, 186 patients were assessed for eligibility. Of these, 4 patients were excluded from the studydue to conversionto general anaesthesia (n = 3) and non- consenting for study (n=1). The remaining enrolled 182 patients completed the study as per the protocol and were included in the analysis.4 patients never achieved T4 level but were not converted to general anaesthesia. The data collection and the study were conducted by the principal investigator to avoid bias. The bupivacaine dosages administered was 1.8 for height <150 cm and 2 mlfor height > 150 cm. The demographic parameters of each patient and the time to achieve the required sensory level after giving spinal anaesthesia was compared

.

(59)

The characteristics of the parturientconsidered for the study are given below in table1.

Table1 . Characteristics of parturients(5)

Variable n Mean S.D. 0.25 0.75 HEIGHT 183 156.79 6.89 152.00 161.00

WEIGHT 183 71.82 13.60 62.00 81.00

BMI 183 29.27 5.09 25.89 32.40

Abdom_Cir 183 106.86 10.48 100.00 114.00 Vercanal_Len 183 56.77 3.90 54.00 59.00

Table 2 shows that majority (63.39%) of the parturients achieved T4 level within 0-5 min followed by 5-10 and 10-15 min.

Table2. Time taken to achieve T4 level (6)

(Min) Freq. Percent Cum.

<0 9 4.92 97.81

0-5 116 63.39 92.35

5-10 26 14.21 28.96

10-15 21 11.48 11.48

15-20 1 0.55 92.90

20-25 4 2.19 13.66

25-30 2 1.09 14.75

Never Achieved 4 2.19 100.00

Total 183 100.00

(60)

Table 3 shows that time taken to fall from the highest level is 25 – 30 min in 30% of the study group followed by 20-25 min.

Table3. Time taken for Level to fall (7)

(Min) Freq. Percent Cum.

0-5 1 0.55 8.20

5-10 3 1.64 7.65

10-15 11 6.01 6.01

15-20 21 11.48 19.67

20-25 32 17.49 37.16

25-30 54 29.51 66.67

30-35 19 10.38 77.05

35-40 18 9.84 86.89

40-45 4 2.19 89.07

45-50 1 0.55 89.62

>50 14 7.65 97.27

Ket 1 0.55 97.81

Never Achieved 4 2.19 100.00

Total 183 100

(61)

Table 4. Correlation table for Time to Achieve T4 level

Variables Pearson Correlation Sig.(2-tailed)

Height 0.158 0.046

Weight -0.086 0.0278

BMI -0.174 0.028

Abdominal Circumference -0.055 0.486

VCL 0.024 0.766

In the above table for time taken for the level to achieve T4, we see that sig(2 – tailed) is < 0.05 in the case of height and body mass index. And pearson correlation in the case of height is 0.158 and body mass index is – 0.178. This implies that there is a positive correlation between height and the time taken for the level to achieve T4, whereas there is a negative correlation between body mass index and the level for spinal anaesthesia to reach T4. P value is not < 0.05 hence there is no correlation between weight, abdominal circumference and vertebral column length.

(62)

Table 5. Correlation table for the level to fall

Variables Pearson Correlation Sig.(2-tailed)

Height 0.057 0.51

Weight 0.084 0.266

BMI 0.084 0.266

Abdominal Circumference 0.138 0.067

VCL 0.019 0.798

In the above table for time taken for the level to fall, we see that sig(2 – tailed) is not <

0.05 in any of the cases, hence there is no correlation between any of the parameters and the time taken for the level to fall.

(63)

The following are the graphical representation – scatter plot of the above data

• Height vs Time of spread of spinal anesthesia

y = 0.164x ‐20.41 R² = 0.043

0 5 10 15 20 25 30

130 135 140 145 150 155 160 165 170 175

Time Taken to achieve T4 Level

HEIGHT (cm)

TIME TAKEN TO ACHIEVE T4 LEVEL (Min)

(64)

Graphically, towards the right hand side of the graph there are more outliers and the distance of the scatter increases from the trend line. It shows the more the height of the patient the greater the time taken to achieve T4 and the lesser the height the T4 will be attained earlier. Similar results are seen with respect to fall from the highest point though the correlation is not as strong as the time to reach T4.

y = 0.102x + 11.48 R² = 0.003

0 10 20 30 40 50 60 70

130 135 140 145 150 155 160 165 170 175

Time taken for Level to fall (Min)

HEIGHT (cm)

(65)

• Weight vs Time of spread of spinal anaesthesia

y = ‐0.025x + 7.147 R² = 0.004

0 5 10 15 20 25 30

30 40 50 60 70 80 90 100 110 120 130

WEIGHT (kg)

(66)

In the above scatter plot, we see that greater the weight, the less the time taken for the T4 to be achieved and the lesser the time taken for the level to fall (indicated as we go towards the right hand side, the greater scatter around the trend line and below the trend line).

y = 0.074x + 22.18 R² = 0.007

0 10 20 30 40 50 60 70

30 40 50 60 70 80 90 100 110 120 130

WEIGHT (kg)

(67)

• Body Mass Indexvs Time of spread of spinal anaesthesia

y = ‐0.175x + 10.45 R² = 0.028

0 5 10 15 20 25 30

15 20 25 30 35 40 45 50 55

BODY MASS INDEX (wt/ht in m2)

(68)

Here we can see the more the body mass index, the lesser the time it takes to achieve T4 lesser the time taken for the level to fall (indicated by the greater scatter around the trend line and the downward scatter as one goes towards the right side of the graph).

This might be explained by the sudden decrease in the intra - abdominal pressure once the baby is delivered.

y = 0.200x + 21.64 R² = 0.007

0 10 20 30 40 50 60 70

15 20 25 30 35 40 45 50 55

BODY MASS INDEX (wt/ht in m2)

(69)

• Abdominal Circumferencevs Time of spread of spinal anaesthesia

y = ‐0.028x + 8.365 R² = 0.003

0 5 10 15 20 25 30

70 80 90 100 110 120 130 140 150 160

ABDOMINAL CIRCUMFERENCE (cm)

(70)

Based on the graph, we can see that greater the abdominal circumference, the less the time taken to achieve T4. Though in the time taken a fall, a general trend is not prominent.

y = 0.161x + 10.27 R² = 0.018

0 10 20 30 40 50 60 70

70 80 90 100 110 120 130 140 150 160

ABDOMINAL CIRCUMFERENCE (cm)

(71)

• Vertebral Canal lengthvs Time of spread of spinal anaesthesia

y = 0.039x + 3.051 R² = 0.000

0 5 10 15 20 25 30

45 50 55 60 65 70

VERTEBRAL CANAL LENGTH (cm)

(72)

There is not much graphical significance seen between vertebral canal length and time taken for the spread of spinal anaesthesia.

y = 0.060x + 24.13 R² = 0.000

0 10 20 30 40 50 60 70

45 50 55 60 65 70

VERTEBRAL CANAL LENGTH (cm)

(73)

0 20 40 60 80 100 120 140 160 180 200

0 5 10 15 20 25 30

TIME TAKEN TO ACHIEVE T4 LEVEL (Min)

BABY WT (Kg) HEIGHT (cm)

WEIGHT (kg) BODY MASS INDEX (wt/ht in m2) ABDOMINAL CIRCUMFERENCE (cm) VERTEBRAL CANAL LENGTH (cm)

(74)

0 20 40 60 80 100 120 140 160 180 200

0 10 20 30 40 50 60 70

Time taken for Level to fall (Min)

BABY WT (Kg) HEIGHT (cm)

WEIGHT (kg) BODY MASS INDEX (wt/ht in m2) ABDOMINAL CIRCUMFERENCE (cm) VERTEBRAL CANAL LENGTH (cm)

(75)

The above graphs shows all the variables plotted as a line graph. In graph 1, the time taken to achieve T4 is plotted on the x – axis, whereas in graph 2, n time taken for the level to fall is plotted on the x – axis.

In the above diagrams we note that the time taken for T4 to be attained is on an average 3 min and time taken for the level to fall from the maximum attained sensory block level is around 25 – 30 min.

DISCUSSION

In this prospective observational study, we considered five parturient characteristics (height, weight, body mass index, abdominal circumference, vertebral column length) to investigate the individual effect of the characteristics on the spread of spinal anaesthesia and to determine which among them was the most significant. In addition, as a corollary we also noted the combined effect of the characteristics on the spread.

Statistically, only height and body mass index were significant, as the height increases the time taken to achieve T4 increases and as the BMI increases the time taken to achieve T4 decreases.

Graphically, though we found that height, weight, body mass index and abdominal circumference strongly correlated with a peak sensory block. The findings suggests that parturients with decreased height, increased weight, increased body mass index and increased abdominal circumference often showed greater cephalad spread of spinal anaesthesia. This was more prominent with respect to the time taken to achieve

(76)

abdominal circumference and, weight and BMI, it was observed on the graph that though time taken to achieve T4 level was less, the time taken for the level to fall was more in some cases. This could be attributed to the sudden fall in abdominal pressure post-deliveryof the fetus. The enlarged uterus obstructs the IVC in the supine position leading to engorgement in the extradural venous plexus in the supine position.

Compression causes the displacement of the lumbosacral CSF to the upper regions.

The correlation of abdominal circumference was not as strong as the other factors like height, weight and body mass index unlike a previous study (4) by Ting-ting Ni, Ying Zhou where a strong correlation was seen. This difference could be the use of isobaric bupivacaine in their study.

Clinically, it was observed that the time taken for the target level of T4 to be achieved was more in taller parturients whereas it was lesser in obese patients, patients with higher BMI, higher abdominal circumference and shorter vertebral canal length. There was greater degree of hypotension in patients with higher BMI but bradycardia was not noted in any of the patients. In addition it was also observed that the time taken to achieve T4 was lesser in the case of a bigger baby. Hence clinically the results observed correlated with studies done earlier.

(77)

In the above table are highlighted a few patients whereT4 levels were reached within less than a min or 0-5 min and it took more than 50 min in most for the levels to fall.

Sr No.

Baby

wt Weight AbdCirc

um Height BMI VCL time to T4

time to fall

Baseline BP

Lowest BP

47 3.60 160 67.00 26.17 103 60 <0 >50 143/86 84/42 72 3.30 145 62.00 29.50 98 47 <0 20‐25 120/76 77/40 85 2.54 158 124.00 53.40 136 58 0‐5 >50 124/85 95/73 107 3.02 161 80.00 30.86 110 58 0‐5 >50 122/75 90/50 113 1.12 148 61.80 28.21 96 64 <0 >50 145/98 114/63 114 2.84 144 60.00 28.93 102 57 <0 35‐40 110/84 72/51 130 3.96 158 94.00 37.60 118 55 <0 35‐40 128/90 75/49 141 149 74.00 33.33 120 55 <0 25‐30 113/63 76/54 181 3.00 155 75.00 31.22 100 55 <0 25‐30 133/86 68/37 102 2.60

1.94 170 86.90 30.06 113 53 0‐5 25‐30 153/95 121/74

(78)

On analysing the data, we reach the following conclusions.

Sr

No. Baby wt Weight AbdCircum Height BMI VCL time to T4

47 3.60 160 67.00 26.17 103 60 <0 >50

In serial no 47, we note that it was a big baby hence the intra-abdominal pressure would be greater which will account for the earlier achievement of T4 level and a higher maximum sensory block level. The patienthad an above average height and vertebral canal length with a normal BMI, hence it took a longer time for the level to fall (>50 min).

Sr

72 3.30 145 62.00 29.50 98 47 <0 20‐25

In serial no 72, we note that the patient has short stature, short vertebral canal length and the patient falls in the BMI category ‘overweight’ hence the lesser time taken to achieve T4 level.

(79)

Sr No. Baby wt Weight AbdCircum Height BMI VCL time to T4 time to fall

85 2.54 158 124.00 53.40 136 58 0‐5 >50

In serial no 85, we see that the patient is overweight and falls in obesity Class III. In addition the patient has a much greater than average abdominal circumference. This accounts for the faster achievement of T4 and greater time for the level to fall (which might also be contributed by the greater vertebral canal length).

Sr

107 3.02 161 80.00 30.86 110 58 0‐5 >50

In serial no 107, the patient has a higher BMI with an average abdominal circumference. This accounts for the faster spinal block levels. The greater vertebral canal length might account for the longer time required for the level to fall.

Sr No. Baby

wt Weight AbdCircum Height BMI VCL time to T4

time to fall

113 1.12 148 61.80 28.21 96 64 <0 >50

In serial no 113, the patient is of short stature and overweight. This might account for the earlier T4 levels and a high sensory block level. The longer vertebral canal length might account for the greater time for the spinal levels to fall.