Predicting Spinal Failure With Blunt Needle Pinprick Sensory Testing
Conditions: Cesarean Section, Anesthesia, Obstetric
Sponsor: Oregon Health and Science University

Unique Protocol ID: 25364 
Study Protocol & Statistical Analysis Plan 
 
Brief Title: Evaluation of the Typical Spinal Block During Cesarean 
Delivery 
 
Official Title: Predicting Spinal Failure With Blunt Needle Pinprick 
Sensory Testing 
 
OHSU IRB STUDY#: 00025364 
 
Document Date: 12/15/2023 
 
Study PI: Brandon M Togioka, MD 
Telephone: 503-494-4572 
Email: togioka@ohsu.edu 
 
Co-Investigator: Stephen Aldous, BS 
Email: aldous@ohsu.edu  
 
 
 
 
 
 

Minimal Risk Protocol Template  
 
1) Protocol Title: Evaluation of the typical spinal block during cesarean 
delivery 
 
Evaluation of the typical spinal block during cesarean delivery: A prospective observational study 
to evaluate the accuracy of sensory testing with blunt needle pinprick as a diagnostic tool for 
predicting spinal failure during non-emergent cesarean delivery 
 
2) Objectives 
 
The objective of this study is to evaluate the accuracy of sensory testing with blunt plastic 16-
gauge cannula during the 15 minutes after spinal injection for predicting spinal failure. Cephalad 
sensory dermatomal levels will be assessed at 1 (t1), 3 (t3), 5 (t5), 7 (t7), 9 (t9), 11 (t11), 13 
(t13), and 15 (t15) minutes after intrathecal 1.6 ml 0.75% bupivacaine in 8.25% dextrose 
combined with 15 mcg fentanyl and 150 mcg morphine (study solution). The primary outcome is 
spinal failure, which is defined as inability to achieve a T4 level to pinprick by the 15-minute 
timepoint or intraoperative pain (VAS > 0) requiring treatment.  Kinsella defined spinal failure 
similarly as preoperative failure to achieve an adequate dermatomal level plus intraoperative 
failure precipitating pain.1 
 
The secondary endpoints are conversion to another anesthetic technique (general anesthesia or 
activation of the epidural catheter) and inadequate anesthesia (analgesic supplementation with 
ketamine, > 20 mg propofol, > 2 mg midazolam, > 10 mg parental morphine equivalents, or 
intraperitoneal chloroprocaine). 
 
3) Background 
 
The vast majority of cesarean deliveries in the developed world are completed under regional 
anesthesia. The most common regional technique chosen to facilitate cesarean delivery is spinal 
anesthesia.1  While the majority of spinal anesthetics are successful, a significant minority are 
associated with inadequate anesthesia and intraoperative pain.1  Intraoperative pain and is a 
significant concern for anesthesia providers because pain during cesarean delivery is associated 
with maternal psychological distress and it is the most common cause of litigation against 
obstetric anesthesiologists.2  It is recommended that providers assess the adequacy of spinal 
block prior to surgical incision by checking sensory dermatomal level.  A sensory level below T4 
is associated with 12 times the odds of spinal failure.1  
 
The sensory level of a spinal block may be tested with different modalities: ice, cold spray, 
pinprick, and light touch.  Previous studies found significant intra-individual variability between 
the sensory level assessed by cold and the sensory level assessed by pinprick.3-5  The sensory 
level assessed by light touch has the least variability.6 Furthermore, sensory level assessed by 
light tight appears to have the smallest transition zone between the upper level of block (the 
dermatome where sensation transitions from normal to abnormal) and the lower level of 
sensation (where sensation is completely lost).  This zone of differential blockade can create 
confusion when assessing the block level and may, at times, explain how two diligent 

practitioners may identify a different level of sensory block.  Additionally, the anesthesia 
community is moving towards using light touch and away from using cold and pinprick to assess 
sensory level.7 Assessing the adequacy of spinal block with light touch is considered by some to 
be the medicolegal standard prior to surgical incision for cesarean delivery.7   
 
Kocarev et al. found that sensory testing with cotton wool was associated with a lower 
coefficient of variation than sensory testing for light touch with more expensive instruments.6  In 
light of this finding and because sterile surgical sponges are readily available in the operating 
room, we trialed assessing light touch with a 4 inch by 4 inch surgical cotton gauze. During the 
trial greater than 50% of patients had difficulty interpreting when they could feel light touch 
with a cotton swab. Furthermore, testing yielded significant intraindividual variability.  We 
concluded that light touch has low reproducibility and reliability in our surgical population 
undergoing cesarean delivery.  Standard practice within our institution now includes assessing 
dermatomal level with pinprick via blunt plastic 16-gague cannula.  For the aforementioned 
reasons it was determined sensory level should be assessed with blunt plastic 16-gague cannula 
in this study.  
 
The aim of this study is to evaluate the accuracy of sensory testing by blunt 16-gague plastic 
cannula for predicting spinal failure.  While previous studies assessed the minimal sensory level 
required for painless cesarean delivery at skin incision or delivery,8 no studies have assessed the 
accuracy of sensory testing at an earlier time point.  Earlier knowledge of which patients are 
likely to have unsatisfactory spinal anesthesia provides additional time to make changes to 
increase the probability of achieving a pain-free operation, such as placing the patient into the 
Trendelenburg position, administering intravenous anesthesia, or requesting surgeon 
administered skin infiltration local anesthetic. These interventions can increase the likelihood 
that a spinal block with a low sensory level will provide adequate intraoperative anesthesia.  
 
4) Study Design 
 
We will be performing a prospective, observational, cohort study involving patients undergoing 
cesarean delivery with intrathecal anesthesia at OHSU University Hospital.   
 
This is an open-label (unblinded) study.   
 
5) Study Population 
 
a) Number of Subjects 
 
Patients undergoing scheduled and urgent (orange or yellow) cesarean delivery at OHSU 
University Hospital will be eligible for inclusion.  
 
In order to evaluate the accuracy of sensory dermatomal testing as a diagnostic tool to predict 
which parturients will have spinal failure we will enroll a cohort with spinal failure and a cohort 
without spinal failure. At the time of enrollment, we will not know who will have spinal failure, 
defined as inability to achieve a T4 level to pinprick by the 15-minute timepoint or intraoperative 
pain (VAS > 0) requiring treatment.  We conducted an analysis of cesarean deliveries completed 

under spinal anesthesia at our institution in 2022. Among 247 deliveries completed under spinal 
anesthesia (excluding the CSE technique), 47 (19%) of patients had intraoperative pain that 
required treatment. Thus, we expect the prevalence rate of spinal failure to be 20%.  Each 
subject will have sensory testing at multiple time points, followed by prospective monitoring for 
pain.  Sample size calculations to assess the diagnostic performance of sensory testing are based 
upon the methods described in Negida et al.9  According to these methods, a total sample size of 
245 patients (196 spinal success group and 49 spinal failure group) is required to achieve 85% 
sensitivity and 85% specificity with 10% maximal acceptable width of the 95% confidence 
interval. We do not expect dropouts because the study period is very short and will occur shortly 
after enrollment.  However, we increased the sample size to 250 in order to account for missed 
data collection. 
 
The sample size of 250 will allow us to achieve a power of 88% and a 0.05 two-sided level of 
significance for detecting a 1 dermatome difference between subjects with spinal success and 
spinal failure, according to the assumption of the two independent sample t-test. 
To calculate the sample size we assumed a standard deviation of 2 dermatomes based upon the 
work of Russell et al.8 We choose 1 dermatome to be a minimal clinically meaningful difference.     
 
b) Inclusion and Exclusion Criteria  
 
Inclusion Criteria 
1. Patients undergoing cesarean delivery under spinal or combined spinal epidural 
anesthesia 
2. BMI between 20 and 40 kg/m2  
3. Height between 5 feet 2 inches and 5 feet 10 inches.  
4. English and non-English speaking patients, if interpretive services are available 
 
Exclusion Criteria 
1. Patient refusal 
2. Contraindications to neuraxial anesthesia (coagulopathy, CNS pathology, 
infection at site of needle puncture) 
3. Allergy to any study medications 
4. Use of epidural anesthesia 
5. Emergency (red) cesarean delivery 
6. Conditions that impact dermatomal sensory testing including spinal cord injury 
with sensory deficits and abdominoplasty 
7. Prison inmates 
8. Decisionally impaired individuals 
9. Pregnancies involving multiple fetuses 
 
c) Vulnerable Populations 
 
We will include pregnant women in this study given that the study focuses on neuraxial 
anesthesia administered to patients undergoing cesarean delivery. All subjects will be 

pregnant. Accordingly, fetuses will be exposed.  However, the medications used are 
standard of care at OHSU and considered safe for the fetus. 
 
Please note all study data will be de-identified. 
 
d) Setting 
 
The research team will conduct the study at OHSU University Hospital on labor and delivery 
(12C). 
 
e) Recruitment Methods 
 
Subjects will be recruited through a screen of the labor and delivery operating room schedule: 
patients scheduled for cesarean delivery under spinal anesthesia at OHSU University Hospital. 
 
There are no recruitment materials. Potential subjects will be recruited on labor and delivery, 
typically in the 12C triage area. 
 
No payment will be provided. 
 
f) Consent Process 
 
Eligible patients will be approached by study staff who will the explain the purpose and 
procedure of the study. This will occur in a timely manner before the cesarean delivery has 
begun, most commonly in the triage area of the labor and delivery unit. In all possible cases the 
consent process will take place when the cesarean delivery is planned. For urgent deliveries, the 
consent process will only be attempted if there is sufficient time for enrollment. If there is not 
sufficient time, the patient will not be consented and/or included. If the patient states they are 
willing to participate they will sign all necessary forms. To avoid coercion or undue influence, the 
study staff will assure all subjects their decision to participate or not participate in the study will 
not affect the level of care they receive. 
 
The use of this secure epic data will not adversely affect the rights and welfare of the subjects as 
the data will remain secure and no HIPAA protected information will be released with the review 
of the charts. 
 
Research procedures to be performed include review of Epic charts with secure log in.  
 
6) Procedures 
 
We will be performing a prospective, observational, cohort study involving patients undergoing 
cesarean delivery with intrathecal anesthesia at OHSU University Hospital. 
 
As standard care, and not for research purposes, all patients will receive a dose of 1.6 ml 0.75% 
bupivacaine with 8.25% dextrose, 15 mcg fentanyl, and 150 mcg morphine.  The spinal 

anesthesia will be placed in the sitting position and the injection will occur at the L2-L3, L3-L4, or 
L4-L5 interspace.  All patients will receive 0.5 mcg/kg/minute of phenylephrine to be started 
immediately after intrathecal injection.  Non-invasive blood pressure measurement will be set to 
a 1-minute frequency. Phenylephrine infusion will be titrated to maintain systolic blood pressure 
within 20% of baseline, per standard anesthetic practice on labor and delivery at OHSU.  
Additional vasopressor or anticholinergic medication administration will be at the discretion of 
the primary anesthesia team.   
 
The time of intrathecal medication administration will be identified as t0. Sensory pinprick 
testing will include use of a 1.5 inch blunt 16-gauge needless vial access cannula (Monoject 
SmarTipTM).  The patient will be educated on baseline (non-blocked) sensation to blunt pinprick 
via pinprick at the right shoulder.  Sensory level will be defined as the first dermatome where 
pinprick sensation is equivalent to baseline shoulder sensation—when is sensation “exactly the 
same.”  Sensory testing will be initiated at the lumbar 1 dermatome and testing will proceed in 
the caudad to cephalad direction.  This is will be standardized because the direction of testing 
(cephalad to caudad versus caudad to cephalad) has been shown to alter the level of sensory 
block identified.10 Sensory block level will be assessed at the midline, which has easily 
discernable key dermatomal landmarks.  Sensory block level has been shown to be symmetric 
with spinal anesthesia.3 Sensory pinprick testing will be conducted every 2 minutes starting 1 
minute after intrathecal medication administration: t1, t3, t5, t7, t9, t11, t13, t15.   
 
We will request that the anesthesia provider keep the patient supine for 15 minutes to allow the 
natural rise in sensory level to be measured.  If the anesthesia team alters the position of the 
patient prior to the 15-minute time point, the subject will remain in the study, but no 
dermatomal testing for the purpose of the study will be recorded thereafter.  After 15 minutes 
the anesthesia team will be free to adjust the patient position.  A sensitivity analysis will be 
completed at the conclusion of the study to assess for confounding from Trendelenburg 
positioning.  A 2-minute increment between assessments was chosen to balance precision with 
patient comfort and to reduce anxiety associated with repeated testing.11  
 
Clinician understanding of dermatomal levels has been shown to be poor.12 Therefore, a 
dermatomal map will be laminated and placed upon the anesthesia machine for the period of 
sensory assessment. 
 
During surgery subjects will be assessed for secondary endpoints: conversion to another 
anesthetic technique (general anesthesia or activation of the epidural catheter) and inadequate 
anesthesia (analgesic supplementation with ketamine, > 20 mg propofol, > 2 mg midazolam, > 10 
mg parental morphine equivalents, or intraperitoneal chloroprocaine).  The decision to convert 
to another anesthetic technique, or administer systemic medications will be at the discretion of 
the anesthesia team and in accordance with standard practice.   
 
7) Data and Specimens 
 
a) Sharing of Results with Subjects 
 
The results of this study will not be shared with participating subjects. 
 

b) Data and Specimen Banking 
 
 
Study subjects will be assigned a unique study number.  All data points, procedure related 
data, and electronic files for data analysis will be linked only to this unique study number.  
This study number will not contain any of the 18 HIPAA identifiers such as: geographic 
location, dates related to the individual, medical record number, account numbers, etc.  The 
key linking study subjects to study code will be kept in a cloud location with special protection 
for confidential and restricted health information (the OHSU ONEDRIVE).  Only the principal 
investigator and other study staff will have access to this key. 
 
Clinical data will be entered into Qualtrics, a 21 CFR Part 11-compliant electronic data capture 
system provided by the Department of Anesthesiology and Perioperative Medicine. This will 
be password protected. Secure data will be stored in Qualtrics for indefinite use.  Data in 
Qualtrics will be linked only to subject study code, not to any of the 18 HIPAA identifiers.   
 
Any data that is shared will be transmitted in an encrypted manner over a secure network.  
Transmitted data will be labeled only with the study code, none of the 18 HIPAA identifiers.  
When data is transmitted, the transmitter (research personnel with access to Qualtrics) will 
be responsible for sending the data in a protected manner.   Any person receiving data will 
then assume responsibility for patient confidentiality and data integrity.   
 
8) Data Analysis 
 
Baseline characteristics collected will include the following: 
a) Age 
b) Race and ethnicity 
c) Primary spoken language 
d) Height 
e) Weight 
f) Body mass index 
g) ASA physical status classification 
h) Hematocrit 
i) 
Gestational age 
j) 
Parity  
 
Intraoperative characteristics collected will include the following: 
a) Surgical duration 
b) Intravenous crystalloid volume 
c) Quantitative blood loss 
d) Intravenous opioids administered (reported as parenteral morphine equivalents) 
e) Bromage scale score at time of skin incision using the following scale: 0 (no motor block), 1 
(able to bend at knee, but unable to complete straight leg raise), 2 (able to dorsiflex at the 
ankle, but unable to bend at knee), 3 (no lower extremity movement).13 
f) Neonate weight 
 
Sensory Testing Endpoints 

a) Sensory level at 1 min 
b) Sensory level at 3 min 
c) Sensory level at 5 min 
d) Sensory level at 7 min 
e) Sensory level at 9 min 
f) Sensory level at 11 min 
g) Sensory level at 13 min 
h) Sensory level at 15 min 
 
Primary Endpoint: 
a) Spinal failure is a composite outcome that will be categorized as “yes” if there is either 
preoperative or intraoperative spinal failure.  Preoperative failure will be defined as failure 
to achieve a T4 level to pinprick by the 15-minute timepoint. Intraoperative failure will be 
defined as pain (VAS > 0) that requires anesthesia provider medication administration.    
1. Pain will be queried at time of skin incision, fetal delivery, uterine exteriorization, 
uterine interiorization or end of uterine closure, and end of skin closure. If VAS > 0, the 
anesthesia provider will ask the patient if they would like analgesic medication.  
2. Discomfort at any other time during the cesarean delivery that is treated with neuraxial 
or intravenous analgesia will also count.  
3. Pain will be rated according to the scale: 0 = no pain, 10 = worst pain imaginable 
 
Secondary Endpoints 
a) Conversion to another anesthetic technique (general anesthesia or activation of the epidural 
catheter)  
b) Inadequate anesthesia (analgesic supplementation with ketamine, > 20 mg propofol, > 2 mg 
midazolam, > 10 mg parental morphine equivalents, or intraperitoneal chloroprocaine) 
c) Patient satisfaction upon arrival to the postanesthesia care unit, rated on a 1-5 Likert scale 
 
Safety endpoints  
a) intraoperative phenylephrine (mcg) 
b) intraoperative hypotension will be defined as SBP <100 mm Hg or >20% drop from baseline, 
or symptoms consistent with hypotension (dizziness, nausea, lightheadedness) with 
administration of phenylephrine or ephedrine 
c) intraoperative dizziness 
d) intraoperative nausea 
e) intraoperative vomiting 
f) ephedrine administration (yes/no) 
g) anticholinergic drug administration (yes/no) 
h) 1-minute APGAR 
i) 
5-minute APGAR 
 
Descriptive data will be summarized with mean (standard deviation) for normally distributed 
continuous data and number (percentage) for categorical data.  Non-normally distributed data 
will be summarized with median (interquartile range).  Measures of central tendency for the 
level of sensory block will be plotted over time.  This data will be stratified according to the 
presence of spinal failure.  This plot will be used to identify the time points where trend lines 
have the greatest divergence.   
 

In separate analysis performed at each time point, the test cut-off line will be set at 85% 
sensitivity.  Sensitivity will be defined as the ability of sensory testing to correctly identify 
patients with spinal failure. Dermatome levels below the test cut-off line will count as a positive 
test result.  Accordingly, sensitivity will be expressed as: [number of subjects with a sensory level 
below the cut-off line that experience spinal failure] / [total number of spinal failures].  
Specificity will also be calculated.  Specificity will be expressed as: [number of subjects with a 
sensory level above the test cut-off line with spinal success] / [total number of spinal successes]. 
 
A sensitivity analysis will be completed to assess the impact of Trendelenburg position on the 
primary and secondary endpoints. 
 
Although we will be testing at multiple time point there will be no adjustment for multiple 
analyses. There are no planned interim analyses.  There are no a priori halting rules because this 
is an observational study.  
 
9) Privacy, Confidentiality, and Data Security 
 
The results of the study as well as all other information collected will be kept in the HIPAA 
compliant Qualtrics.  Clinical information will be linked to a unique study number.  The link 
between the study number and subject identifiers will be kept in a cloud location (the OHSU 
ONEDRIVE) with special protection for confidential and restricted health information.  No 
protected health information or other data collected during the completion of this study will 
be taken off campus.  All data gathered for this study will be coded before any analysis or 
publication occurs. 
 
Access to the study data file(s), linking file, and master list of subject identifiers will be restricted 
to only the study PI, Co-Investigators, and Research Coordinator. 
 
10) 
Risks and Benefits 
 
a) Risks to Subjects 
 
There is minimal to risk to subjects. There could be mild discomfort during sensory testing and 
multiple tests may produce anxiety in some subjects.  Additionally, loss of confidentiality is 
unlikely but possible.  As described above multiple steps will be taken to ensure that this does 
not occur.  Should loss of confidentiality occur the IRB will be notified within 72 hours. 
 
There are risks, unrelated to the research study, that occur with administration of the standard of 
care drug during spinal anesthesia. The subject will already have been informed and consented 
about these separate risks by their physician before cesarean delivery.  
 
b) Potential Benefits to Subjects 
 
There is no direct benefit to the subjects of this study. However, this study may help lead to the 

identification of methods that can more accurately predict spinal anesthesia success for 
cesarean sections, increasing patient safety and satisfaction. 
 
11) 
References 
 
 
1. 
Kinsella SM. A prospective audit of regional anaesthesia failure in 5080 Caesarean 
sections. Anaesthesia. Aug 2008;63(8):822-32. doi:10.1111/j.1365-2044.2008.05499.x 
2. 
McCombe K, Bogod DG. Learning from the Law. A review of 21 years of litigation for 
pain during caesarean section. Anaesthesia. Feb 2018;73(2):223-230. doi:10.1111/anae.14119 
3. 
Russell IF. A comparison of cold, pinprick and touch for assessing the level of spinal 
block at caesarean section. Int J Obstet Anesth. Jul 2004;13(3):146-52. 
doi:10.1016/j.ijoa.2003.12.007 
4. 
Ousley R, Egan C, Dowling K, Cyna AM. Assessment of block height for satisfactory 
spinal anaesthesia for caesarean section. Anaesthesia. Dec 2012;67(12):1356-63. 
doi:10.1111/anae.12034 
5. 
White JL, Stevens RA, Kao TC. Differential sensory block: spinal vs epidural with 
lidocaine. Can J Anaesth. Nov 1998;45(11):1049-53. doi:10.1007/BF03012390 
6. 
Kocarev M, Watkins E, McLure H, Columb M, Lyons G. Sensory testing of spinal 
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7. 
Hoyle J, Yentis SM. Assessing the height of block for caesarean section over the past 
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8. 
Russell IF. Levels of anaesthesia and intraoperative pain at caesarean section under 
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9. 
Negida A, Fahim NK, Negida Y. Sample Size Calculation Guide - Part 4: How to 
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10. 
de Souza Soares EC, Balki M, Downey K, Ye XY, Carvalho JCA. Assessment of sensory 
block during labour epidural analgesia: a prospective cohort study to determine the influence of 
the direction of testing. Can J Anaesth. Jun 2022;69(6):750-755. Evaluation du bloc sensoriel 
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l'influence de la direction des tests. doi:10.1007/s12630-022-02228-x 
11. 
Stanford SE, Bogod DG. Failure of communication: a patient's story. Int J Obstet Anesth. 
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12. 
Yentis SM. Height of confusion: assessing regional blocks before caesarean section. Int J 
Obstet Anesth. Jan 2006;15(1):2-6. doi:10.1016/j.ijoa.2005.06.010 
13. 
Bromage PR. A comparison of the hydrochloride and carbon dioxide salts of lidocaine 
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doi:10.1111/j.1399-6576.1965.tb00523.x