Distance to epid space in partu (ppp) Dr tabatabi

Determination of the Distance From Skin to the Epidural Space in Parturients, and Correlation with Weight, Body Mass Index, Height, and Age Mahmood Tabatabai, MD, PHD

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The purpose of the study was to measure the distance between the skin and the epidural space in the lumbar area in parturients receiving epidural block during labor and delivery.

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This information helps to prevent or minimize the incidence of inadvertent dural puncture and subsequent post dural puncture headache (PDPH).

Purpose

 One

hundred patients in labor and delivery were included in this study.  Epidural block was performed in Sitting Position at the interspace between the 3rd and 4th Lumbar Vertebras, using a graduated Tuohy needle gauge 17, and Loss of Resistance (LOR) technique. Correct needle entry into the epid space was further confirmed by the relief of labor pain upon injection of Lidocaine into the space.  The Distance between the skin and the epidural space was measured.  The relation of the Body Weight, Body Mass Index (BMI), Height, and Age with the Distance was ascertained using Pearson Correlation Coefficient (r) and Linear Regression Analysis.  P<0.05 was considered statistically significant.

Patients and Methods

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Extends from Foramen Magnum to the 2nd sacral vertebra along the spinal cord dural sac.

Epidural Space

Epidural Space

Epidural Space

Anatomy of the Epidural Space

Anatomy of the Epidural Space

Epidural Block, Sitting Position

Epidural Block, Lateral Decubitus Position

Epidural Needle Insertion

Epidural Injection

Epidural Needles

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1. Single injection

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2. Continuous injection via the epidural catheter

Epidural Injection of the Local Anesthetic

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1. Loss of Resistance Technique

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2. Hanging Drop Technique

Technique of Epidural Block

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1. By Loss of Resistance after passing through the Ligamentum Flavum.

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2 . Relief of labor pain after injection of the local anesthetic into the epidural space.

Confirmation of the Needle Entry into the Epidural Space

Relevant Statistics: Descriptive Statistics: Mean, SD, SE, Median, Mode, etc Pearson Correlation Coefficient = r r value varies from (+1) to (-1) Equation for a Straight Line: Y=mX+b, where m=slope of the line, and b= Y intercept Statistical Significance is shown by the P value: P<0.05 is statistically significant, and P<0.01 is statistically extremely significant 95% Confidence Interval (95% CI) = Mean +/- (2 SE), where SE = SD/square root of N, and N is the Number of observations

Straight Line Equation Y = mX + b

Relevant Statistics: Descriptive Statistics: Mean, SD, SE, Median, Mode, etc Pearson Correlation Coefficient = r r value varies from (+1) to (-1) Equation for a Straight Line: Y=mX+b, where m=slope of the line, and b= Y intercept Statistical Significance is shown by the P value: P<0.05 is statistically significant, and P<0.01 is statistically extremely significant 95% Confidence Interval (95% CI) = Mean +/- (2 SE), where SE = SD/square root of N, and N is the Number of observations

Weight vs Distance Correlation Coefficient r = 0.7460, P<0.0001 Slope = 0.044, P<0.0001 Y = 0.044X + 1.442

BMI vs Distance r = 0.6958, P<0.0001

Height vs Distance r = 0.2242, P<0.05

Age vs Distance r = 0.09907, P = 0.3268

Relevant Statistics: Descriptive Statistics: Mean, SD, SE, Median, Mode, etc Pearson Correlation Coefficient = r r value varies from (+1) to (-1) Equation for a Straight Line: Y=mX+b, where m=slope of the line, and b= Y intercept Statistical Significance is shown by the P value: P<0.05 is statistically significant, and P<0.01 is statistically extremely significant 95% Confidence Interval (95% CI) = Mean +/- (2 SE), where SE = SD/square root of N, and N is the Number of observations

How to Find m and b?

Straight Line Equation Y = mX + b

Weight vs Distance Correlation Coefficient r = 0.7460, P<0.0001 Slope = 0.044, P<0.0001 Y = 0.044X + 1.442

Y = 0.044 X + 1.442

 Example

1: The parturient weighs 100 kg.

What is the estimated distance from the skin to the epidural space?  X = 100 kg, Y?  Y = (0.044 x 100) + 1.442 = 4.4 + 1.442 = 5.842 cm

 Example

2: The parturient weighs 75 kg. What is the estimated distance from the skin to the epidural space?  X = 75 kg, Y?  Y = (0.044 x 75) + 1.442 = 3.3 + 1.442 = 4.742 cm

Y = 0.044 X + 1.442

PDPH is believed to be due to the leakage of the CSF through a dural tear or defect, resulting in intracranial hypotension.  Usually it develops 12-72 hours after the epidural wet tap, though it may happen almost immediately.  Headache is usually bilateral, frontal, retro-orbital or occipital, and may extend into the neck. It may be associated with photophobia and nausea.  The hallmark of the PDPH is the association with the body position: intensified by sitting or standing up, and relieved or decreased by lying down flat. 

Postdural Puncture Headache (PDPH)

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1. Conservative: Bed rest in supine position, oral and intravenous fluids, analgesics (acetaminophen, NSAIDS, opioids), caffeine sodium benzoate 500 mg in 1000 ml crystalloid solution, given intravenously.

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2. Epidural blood patch: 15- 20 ml autologous blood injected at the initial site of the epidural block, or one level above or below. 10% of the patients may require a second epidural blood patch.

Treatment of PDPH

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The body weight and the BMI appear to be the major determinants of the distance between the skin and the epidural space.

Caution has to be exercised during induction of epidural block to avoid dural puncture and wet tap, which may result in PDPH. The results may be used as a guide in performing a safe epidural block and avoiding dural puncture.

Conclusions

Thank you for your attention.

Abstract

Intracranial Contents

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Brain accounts for 80% of the volume Blood accounts for 12% of the volume CSF accounts for 8% of the volume

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Volume: 150 ml in adults, and 50 ml in infants.

CSF production: 21-23 ml per hour, or 500-550 ml per day in adults.

CSF production is mainly by the choroid plexus of the cerebral ventricles, and absorption mainly via the arachnoid villi into the cerebral venous sinuses.

Cerebrospinal Fluid (CSF)

Brain  Intracranial

Pressure (ICP): 7-15 mm Hg  Cerebral Perfusion Pressure (CPP) = MAP-ICP, or  CPP = MAP-CVP  Normally, CPP = 90 – 10 = 80 mm Hg  In

the systemic circulation:  Driving Pressure = Mean Arterial Pressure (MAP) – CVP  Cerebral

Blood Flow = 50 ml/100 gm/min  Brain weight = 1400 gm

Epidural Space

Abstract

Weight vs Distance

BMI vs Distance

Age

Relevant Statistics: Descriptive Statistics: Mean, SD, SE, Median, Mode, etc Pearson Correlation Coefficient = r r value varies from (+1) to (-1) Equation for a Straight Line: Y=mX+b, where m=slope of the line, and b= Y intercept Statistical Significance is shown by the P value: P<0.05 is statistically significant, and P<0.01 is statistically extremely significant 95% Confidence Interval (95% CI) = Mean +/- (2 SE), where SE = SD/square root of N, and N is the Number of observations