PREDICTING DIFFICULT NEURAXIAL BLOCK

Dr Divesh Arora

Consultant Anesthesiologist

INTRODUCTION

Anticipated technical difficulty can influence the anesthesiologist’s decision to perform neuraxial block.

Multiple attempts at needle placement might lead to:*•Patient discomfort•Higher incidence of spinal hematoma•PDPH•Trauma to neural structures*Horlocker TT et al. A retrospective review of 4767 consecutive spinal anesthetics:CNS complications. Anesth Analg 1997;84:578-84

• Limited work has been carried out to predict difficult neuraxial block

• Scoring system to predict difficult neuraxial block ?

• Reliability of the predictive factors and scoring systems

FACTORS PREDICTIVE OF DIFFICULT NEURAXIAL

BLOCK• Age• Sex• Weight• BMI• Body habitus• Spinal bony landmarks• Spinal bony deformity• Previous spine surgery• Radiological characteristics of vertebrae

PATIENT CHARACTERISTICS

• Age: degenerative changes, osteophytes

• Sex: Osteoarthritis and lordosis more prevalent in females

• BMI:Distribution of fat

Body Habitus*

• Normal

• Thin

• Muscular

• Obese*Sprung et al. Predicting the difficult neuraxial block: A

prospective study. Anesth Analg 1999;89:384-9.

Spinal Bony Landmarks*

• Grade I: Spinous processes visible

• Grade II: Spinous processes not visible but palpable

• Grade III: Spinous processes not visible and not palpable

• Grade IV: No Landmarks*Chien I et al. Spinal process landmark as a predicting factor

for difficult epidural block. Kaohsiung J Med Sci Nov 2003;19(11):563-8

SPINAL BONY DEFORMITY

LORDOSIS SCOLIOSIS

KYPHOSIS ANKYLOSING SPONDYLITIS

Previous Spine surgery

• Post operatively anatomical as well as degenerative changes occur in spine

• Limited spread of LA due to adhesions

• X Ray spine is of value

Radiological Characteristics of

Vertebrae

• Presence / Absence of osteophytes

• Ligament Calcification

• Narrow Intervertebral spaces

• Spinal bony deformity

• Identification of the entry point

• Skin crease serves as a landmark

• Approximate depth of epidural / subarachnoid space

DIFFICULTY SCORE FOR NEURAXIAL BLOCK *

0 1 2 3

Age(yr) 20-40 41-60 >60 ---

BMI(Kg/m2) <22 22-27 27-34 >34

Spinal Bony Landmarks

Clear Unclear --- ---

Spinal Bony Deformity

No Yes --- ---

Radiology Of Vertebrae

Easy Difficult --- ---

*Atallah et al. Development of a difficulty score for spinal anesthesia. Br J Anaesth 2004;92:354-60

TECHNICAL DIFFICULTY

• Each new skin puncture is counted as a new attempt

• Redirection of needle in the ligaments

• Change of intervertebral space

• Time required for the completion of procedure

• Patient Discomfort

RELEVANT STUDIES

Sprung et al. Predicting the difficult neuraxial block: A prospective study. Anesth Analg 1999;89:384-9.

• BMI weakly related

• Quality of landmarks correlates best

• Patient characteristics not associated with difficulty

Filho et al. Predictors of successful neuraxial block: A prospective study. Eur J Anaesthesiology 2002 June;19(6):447-51

• Anatomical landmarks, Patient positioning, Experience of Anesthetist are independent predictors of success.

• Patient characteristics are minor predictors.

Chien I et al. Spinal process landmark as a predicting factor for difficult epidural block. Kaohsiung J Med Sci Nov 2003;19(11):563-8

• Spinal landmark grading system is valuable.

• Deformed spinal anatomy and body habitus correlates with the number of attempts required.

OUR EXPERIENCE

• High volume joint replacement unit

• CSE is the mainstay anesthesia technique

• X Ray lumbosacral spine is routinely done

• Prospective study on this topic is being conducted by our unit

• Detailed analysis is yet to be completed

• Age: younger the better

• Sex: more difficult in females

• BMI: Distribution of fat is more important

• Spinal bony landmarks palpation in conjunction with radiological characteristics of spine correlates with technical difficulty

• Deformity of spine increases the number of attempts

How To Make Difficult Neuraxial Block Successful

As the quality of anatomical landmarks cannot be changed special attention should be given to the following:

• Explanation of the procedure to the patient

• Proper patient positioning• Experience of anesthesia provider• Paramedian or taylors approach

USE OF C ARM

USE OF USG

CONCLUSION

Examination of patients back for the:

• Quality of landmarks

• Spinal deformity

And radiology of spine are the most reliable methods of determining the ease or potential difficulty in performing the neuraxial block