Optimization of crystalloid co-loading speed to stabilize haemodynamics in patient undergoing elective Lower Segment Caesarean section under spinal anaesthesia: A Randomized Control Trial

Background

Spinal anaesthesia is established anaesthesia technique for management of elective lower segment caesarean section (LSCS). However post spinal hypotension is common  and may affect maternal and foetal outcomes adversely. Intravenous fluid loading at peak sympathetic blockade (5-7 minutes) is critical to prevent post spinal hypotension. Crystalloid preloading is ineffective and crystalloid co loading though effective and routinely used to prevent post spinal hypotension show contradictory results to mitigate post spinal hypotension  may be due to inadequate crystalloid co loading infusion speed during peak sympathetic block. The optimal speed of crystalloid co loading fluid infusion is under research to prevent post spinal hypotension in obstetric patients undergoing lower segment caesarean section under spinal anaesthesia during perioperative period in this study.

AIMTo optimize crystalloid co-loading flow rate/speed to achieve desired co loading volume to stabilize haemodynamic in patient undergoing elective LSCS under spinal anaesthesia to prevent maternal hypotension.

OBJECTIVES

Primary objective -

·       To assess effect of optimizing flow rate/speed of crystalloid co loading to prevent incidence of maternal hypotension in patient undergoing elective LSCS under spinal anaesthesia.

Secondary objective-

·       To calculate the requirement of vasopressor and anticholinergic drug during peri-operative period to prevent the maternal hypotension**.**

·       To document the side effects of crystalloid co loading.

·       To evaluate the APGAR score of new born.

RATIONALE

Peak sympathetic blockade induced vasodilatation occurs at 5-7 minutes of post spinal anaesthesia.Crystalloid co loading during LSCS with 16 G and 18 G cannula unable to reach in vitro infusion rate in patients at 5-7 minutes, resulted in hypotension.Increasing the pressure gradient across iv infusion bag and tip of catheter by applying constant 300 mmhg of pressure increases the fluid transfusion rate in vitro as per Hagen Poiseuille Equation.Optimized crystalloid co loading speed and volume by pressure bag (pressurized to 300mmhg constant pressure) at 5-7 minutes likely to prevent post spinal hypotension.

STUDY DESIGN

Prospective, randomized, controlled, double blind, single centre, parallel group comparative clinical trial.

SAMPLE SIZE

The required sample size is determined to be 68 patients with 34 patients in each group.

STUDY DESIGN, MATERIAL AND METHODS

 STUDY DESIGN Single Centre Prospective randomized controlled double blind parallel group comparative clinical trial.

STUDY SETTING- Department of Anaesthesiology, VCSGGIMSR Garhwal, Srinagar, Uttarakhand.

STUDY DURATION 10 to 12 months

After pre-anaesthetic evaluation and informed consent American Society of Anaesthesiologists Grade 2 pregnant patients undergoing elective LSCS under spinal anaesthesia will be taken for study and randomised into two groups by double blind method.

GROUP A -INTERVENTION 16 Gauge intravenous cannula with optimization of crystalloid co loading speed.

GROUP B – COMPARATOR 16 Gauge intravenous cannula without optimization of crystalloid co loading speed.

Intravenous cannula   Intravenous cannula of 16 Gauge with flow rate 200 ml per minute will be used in both group A and group B.

Crystalloid fluid

Ringer lactate is co loading fluid in dose of 20ml per kg which  will be started in both the groups immediately after giving spinal anaesthesia.

Optimization

In group A optimization of crystalloid fluid flow rate or speed will be done by constant pressure application of 300mmhg by pneumatic pressure infuser bag cuff sleeve wrapped around 500 ml bag of ringer lactate hanging on drip stand creating the pressure gradient across chamber spike of intravenous drip set and tip of intravenous cannula at patient end.

In group B intravenous crystalloid co loading will be done by gravity dependent method with 500 ml of ringer lactate bag attached on drip stand without pressure optimization.

The distance between spike of intravenous drip set and patient intravenous cannula end is 100 to 120 cm in both the groups intravenous ringer lactate co loading will be done by conventional intravenous set of internal diameter 3mm and length of 150 cm.

Randomization will be done by chit box envelope method. Patient cannula hub will be white taped. Blinding or masking will be done by hiding the pressure dial of pressure infusion bag cuff wrapped around 500 ml bag of ringer lactate hanging on drip stand

Spinal anaesthesia will be given using 2 ml hyperbaric 0.5 percent bupivacaine heavy in sitting position in L3  L4 intervertebral space using 25G Quincke’s spinal needle under all aseptic conditions and all the parturient will be placed in supine position with slight inclination.

The extent of sensory block will be checked every minute using pin-prick method till a sensory block level of T6-T4 is achieved. Co loading with crystalloids(ringer lactate) 20ml per kg will be started just after spinal anaesthesia.

Hypotension will be defined as fall in MAP equal or more than 20% of baseline.

Crystalloid co loading will be started just after giving the spinal anaesthesia with ringer lactate 20 ml per kg. Spike of intravenous drip set at height of 100 to 120 cm from patient cannula end in both the group. In group A constant 300mmhg  pressure will be created with pneumatic pressure sleeve wrapped around the 500 ml ringer lactate bag creating pressure head or gradient between the spike of fluid infusion set and patient intravenous cannula end . This will be done by repeatedly pressing the pump bulb of pneumatic pressure infusion bag by nursing staff or anaesthesia technician or resident doctor not aware of study. In Group B pneumatic pressure infuser pump bulb will be pressed repeatedly with open valve of  pump bulb of pneumatic pressure sleeve wrapped around the 500 ml ringer lactate bag without creating the pressure gradient across chamber spike of intravenous drip set and tip of intravenous cannula at patient end to ensure blinding of study. Investigator will not be aware of group A or B.

Perioperative hypotension will be treated with inj ephedrine-3 mg bolus if there is fall in MAP equal or more than 20 percent of baseline. Total dose of ephedrine will be calculated during perioperative period.

Bradycardia will be defined as heart rate  less than 60 bpm, intervened by inj atropine 0.6 mg.

Patient observation, monitoring and data recording

Perioperative monitoring toolsECG, NIBP, SPO2 will be used to monitor haemodynamic indices SBP, DBP, MAP, Heart Rate, urine output, perfusion indexnoted from basal to the interval of 2 minutes, up to 30 minutes. Induction to incision time, incision to delivery time, duration of surgery, co loading volume 20ml per kg infusion time, requirement of vasopressor- total dose will be noted.

Total fluid volume and time taken to infuse the crystalloid co load will be noted in both the groups. Apgar score will be evaluated at 1 min and 5 min by paediatrician unaware of group allocation.

STATISTICAL ANALYSIS Statistical analysis using unpaired t test and ANOVA test by SPSS OR Open EPI software.