Height Versus Height and Weight Based Spinal Bupivacaine on Maternal Haemodynamics for Elective Cesarean in Short Stature Patients

Height Versus Height and Weight Based Spinal Bupivacaine on Maternal Haemodynamics for Elective Cesarean in Short Stature Patients

Effect of Height Versus Height and Weight Based Intrathecal Bupivacaine Dose on Maternal Haemodynamics for Elective Caesarean Section in Short Stature Patients: A Randomized Trial

Doses of intrathecal bupivacaine based on patients either height or height and weight has shown to lower the risk of maternal hypotension with similar quality of anesthesia compared to conventional doses. In clinical practice there is a tendency of reducing the dose of bupivacaine as either low fixed dose or using the doses based on either height and weight or height (0.06mg/cm) alone in parturient with short stature. However, there is lack of evidence regarding the appropriate dose required in this group of patients. Therefore, our aim is to compare the height versus height and weight based intrathecal bupivacaine dose for elective caesarean on maternal haemodynamics in short stature patients.

Spinal induced hypotension in women undergoing caesarean section (CS) is the most common unwanted effect. The dose of intrathecal local anesthetic is the main determining factor that balances between successful block and an incidence of maternal hypotension. Although lowering the doses of intrathecal bupivacaine provides better maternal hemodynamic stability it compromises the quality of anesthesia. Moreover, there is no consensus regarding the cut-off at which the dose can be defined as low. Doses based on patients either height or height and weight has shown to lower the risk of maternal hypotension with similar quality of anesthesia compared to conventional doses. In clinical practice there is a tendency of reducing the dose of bupivacaine as either low fixed dose or using the doses based on either height and weight or height (0.06mg/cm) alone in parturient with short stature. However, there is lack of evidence regarding the appropriate dose required in this group of patients. Our aim is to compare the height versus height and weight based intrathecal bupivacaine dose for elective caesarean on maternal haemodynamics in short stature patients. Doses of intrathecal bupivacaine for elective caesarean section based on Harten chart is available from the following reference- Harten JM, Boyne I, Hannah P, Varveris D, Brown A. Effects of a height and weight adjusted dose of local anaesthetic for spinal anaesthesia for elective Caesarean section. Anaesthesia 2005; 60: 348-53. Consent for the participation in the study will be obtained during pre-anaesthetic assessment visits in the evening before surgery. The investigator will also educate the patients regarding the use of numeric rating scale scores. Preoperative anxiety will be recorded in numerical rating scale scores where 0 is no anxiety and 10 is maximum anxiety patient reported. The enrolled subjects will be randomly assigned to 2 equal groups (allocation ratio, 1:1) according to the codes generated from the website (www.sealedenvleop.com) using the variable block size of 4, 6 and 8. The group allocation will be concealed in sequentially numbered, sealed opaque envelopes that will be opened by the anaesthesia assistant not involved in the study only after the patient arrives in the operating room. The patient will be fasted for at least eight hours and will receive antibiotics, ranitidine 50 mg and metoclopramide 10 mg intravenously via 18-gauge cannula before transfer to the operation room. In the operating table patient will be laid supine with a wedge under right buttock and standard monitors (electrocardiography, pulse oximetry, and noninvasive BP) will be applied. Thereafter, successive three readings of heart rate (HR) and systolic blood pressure (SBP) will be taken at 2 minutes interval with difference not exceeding 10%. The average of these recordings will be documented by the investigators as baseline parameters. To maintain blinding, the investigator will leave the operating room and will return immediately once the spinal injection is initiated. Subarachnoid block will be performed by the attending anesthesiologist not involved in the study in the sitting position at the L3-L4 or L4-L5 vertebral interspace using a 25-gauge spinal needle via midline approach. The study solution will be administered according to the group allocated. In Group A the dose of heavy bupivacaine will be based on height and weight and in group B the dose will be based on patient's height (0.06 mg/cm). 10 microgram fentanyl will be added to bupivacaine in both groups.

Patients in "Height and weight based group" will receive intrathecal hyperbaric bupivacaine based on patients height and weight according to Harten chart with 10 μg of fentanyl (0.1 ml)

Patients in "Height based group" will receive intrathecal hyperbaric bupivacaine based on patients height i.e. (0.06mg/cm) with 10 μg of fentanyl (0.1 ml)

In this group patient will receive intrathecal hyperbaric bupivacaine based on patients height and weight according to Harten chart with 10 μg of fentanyl (0.1 ml)

In this group will receive intrathecal hyperbaric bupivacaine based on patients height (0.06mg/cm) with 10 μg of fentanyl (0.1 ml)

Number of patients with post spinal hypotension (defined as systolic blood pressure in mmHg, <10% of the baseline reading or SBP < 100 mm Hg observed from spinal injection until delivery of baby

Number of patients with post delivery hypotension (defined as systolic blood pressure in mmHg, <10% from the baseline reading or systolic blood pressure < 100 mm Hg observed after delivery of the fetus and starting oxytocin infusion until end of surgery

Number of patients with post spinal hypotension (defined as systolic blood pressure in mmHg, <20% of the baseline reading or SBP < 100 mm Hg observed from spinal injection until delivery of baby

Number of patients with post delivery hypotension (defined as systolic blood pressure in mmHg, <20% of the baseline reading or systolic blood pressure < 100 mm Hg observed after delivery of the fetus and starting oxytocin infusion until end of surgery

lowest systolic blood pressure (SBP) recorded in mmHg from spinal injection until delivery and then end of surgery.

Hypotension associated without bradycardia will be treated with phenylepinephrine. Hypotension associated with bradycardia (HR 50/min) will be treated with IV ephedrine 6 mg and followed by IV atropine 0.5 mg.

Number of patients complaining nausea and vomiting. Patients will be instructed to report intraoperative nausea based on an 11-point Numeric Rating Score (NRS), where 0 describes "no nausea" and 10 describes nausea "as worst as it could be". Score more than 0 will be considered as nausea. Patients reporting NRS score > 3 for nausea or vomiting will be managed with IV ondensetron 4 mg. If nausea and vomiting persisted after 5 min, IV dexamethasone 4 mg will be administered.

Number of patients with shivering. Intraoperative shivering will be graded as : 0 no shivering, 1 one or more of the following: piloerection, peripheral vasoconstriction, peripheral cyanosis without other cause, but without visible muscular activity; 2 visible muscular activity confined to one muscle group; 3 visible muscular activity in more than one muscle group; and 4 gross muscular activity involving the whole body. If the shivering score is ≥3, IV meperidine 20 mg will be administered.

Number of patient requiring intraoperative supplemental analgesia. Patients will be instructed to report intraoperative pain based on an 11-point Numeric Rating Score (NRS), where 0 describes "no pain" and 10 describes worst pain "as worst as it could be". It will be assessed using NRS scores at the following intervals: skin incision, delivery, uterine exteriorization, peritoneal closure, and skin closure. If patients reported pain or discomfort (if NRS is mild i.e scores between 1-3), then IV fentanyl 20 microgram will be given and second dose will be repeated if needed. If pain still persists then IV ketamine 0.25 mg/kg will be given.

Assessed using a four-point scale: 1=excellent, 2=good; some feelings but no discomfort, 3=fair; some discomfort but rescue analgesia unnecessary, 4=poor; major discomfort and rescue analgesia required.

Assessed at 5 min interval after IT injection using a 5-point ordinal scale, where 0 = Awake and alert; 1 = resting with eyes closed; 2 = drowsy and responsive to verbal stimuli; 3 = drowsy and responsive to physical stimuli and 4 = unarousable.

It will be recorded before discharge from PACU using a NRS with "very dissatisfied" at 0 cm and "very satisfied" at 10 cm.

Number of patients with pruritus. Intraoperative pruritus will be assessed using NRS scale (0 - 10 scale, with 0, no pruritus, and 10, worst pruritus imaginable). NRS score > 3 will be treated with IV chlorpheniramine 10 mg.

Duration of analgesia in hours (time elapsed between intrathecal injection and the first perception of pain) will be noted

Time to Bromage scale 3. Motor block will be assessed using the Bromage scale (0-3): 0, able to straight leg raise (SLR) and flex both feet and knees; 1, unable to SLR, able to flex knees and feet; 2, unable to SLR or flex knees, able to flex feet; and 3, unable to move legs or feet.

Time to Bromage scale regression to 0. Motor block will be assessed using the Bromage scale (0-3): 0, able to straight leg raise (SLR) and flex both feet and knees; 1, unable to SLR, able to flex knees and feet; 2, unable to SLR or flex knees, able to flex feet; and 3, unable to move legs or feet.

Neonatal Apgar scores after delivery assessed by attending pediatrician. It is determined by evaluating the newborn baby on five criteria(Appearance, Pulse, Grimace, Activity, Respiration) on a scale from zero to two, then summing up the five values thus obtained. The resulting Apgar score ranges from zero to 10. Scores 7 and above are generally normal; 4 to 6, fairly low; and 3 and below are generally regarded as critically low requiring immediate resuscitation.

Inclusion Criteria: Women with full-term gestation undergoing planned Caesarean section under spinal anesthesia Who provide consent . Height less than 150 cm Exclusion Criteria: Patients with height <140 cm, Hypertensive disorders of pregnancy, Placental disorders, Body mass index ≥ 40 kg/m2, Diabetes mellitus Cardiovascular Cerebrovascular Hormonal disorder Renal disease Polyhydramnios Known case of bad obstetric history Fetal abnormalities Baseline systolic blood pressure (SBP) less than 100 mmHg Contraindication to spinal anaesthesia Allergy to any drug used in the study and Those unable to understand and sign the consent form

The final research data will be stored in Mendeley. The final data will be released and shared during the publication process of the manuscript.

The final research data and study protocol will be shared with the journal accepting the article for publication. It will be available simultaneously after publication of the article.

The IPD link will be accessed from the link provided in the published manuscript. The IPD may also be available to other researchers by the investigators upon request.