Remember me
ORIGINAL ARTICLE
Year : 2022 | Volume
: 12
| Issue : 2 | Page : 133-139
Effect of abdominal girth, vertebral column length, and hip/shoulder width ratio on the spread of spinal anesthesia in term parturients undergoing elective cesarean section: A prospective observational non-randomized study
Anil K Bhiwal1, Heena A Bhatt2, Lalita Jeengar2, Karuna Sharma1, Aditi S Baghel1, Sunanda Gupta1
1 Department of Anaesthesiology Geetanjali Medical College and Hospital, Udaipur, Rajasthan, India
2 Department of Anaesthesiology and Critical Care, American International Institute of Medical Sciences, Bedwas Udaipur, Rajasthan, India
Correspondence Address:
Dr. Karuna Sharma
Associate Professor, Address-E-704, Krishnangan, New Vidhya Nagar, Sector 4 Hiran Magri, Udaipur - 313 002, Rajasthan
India
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/JOACC.JOACC_68_21
Background: Spinal anesthesia is the preferred technique for cesarean section, and a suitable level of spinal anesthesia is essential, which may be variable in every parturient. The aim of this study was to evaluate the correlation of abdominal circumference (AC), vertebral column length (VCL), hip shoulder width ratio (HSR), and vertebral column length (VCL)/Abdominal Circumference (AC)2 with the spread of spinal anesthesia in term parturient undergoing elective cesarean section. Methods: Two hundred term parturients undergoing elective cesarean section were enrolled in this prospective observational study. Spinal anesthesia was performed with 10 mg (2 ml) of 0.5% hyperbaric bupivacaine in L2-L3 or L3-L4 interspace using a 25 G Quincke needle. The cephalad spread (loss of pinprick discrimination) was assessed up to 30 minutes after intrathecal injection. Linear regression analysis was used to analyze the relationship between age, weight, height, body mass index (BMI), AC, VCL (C7-Sacral hiatus and C7-iliac crest), HSR, VCL/AC2, and the spread of spinal anesthesia. Results: The maximum sensory level showed a significant correlation with AC (P < 0.001), VCL [C7-SH and C7-IC] (P < 0.039 and P < 0.025) and VCL/AC2 (P < 0.001). Individually, hip width and shoulder width showed a significant correlation with cephalad spread of spinal anesthesia (P < 0.05); however, HSR had no significant correlation with the spread of anesthesia (P > 0.05). Conclusion: AC, VCL, and VCL/AC2 have a significant correlation with cephalad spread of spinal anesthesia when a fixed dose of hyperbaric bupivacaine is used in term parturients undergoing elective cesarean section, while HSR did not show any significant correlation.
Keywords: Abdominal girth, cesarean section, spread of spinal anesthesia, vertebral column length
A desirable level for spinal anesthesia during cesarean delivery is a bilateral block between Thoracic dermatome (T4) to Thoracic dermatome (T6) assessed by pinpricks.[1] However, this spread of spinal anesthetic block may be variable and can lead to hemodynamic instability with excessive spread or unsatisfactory surgical condition and pain.[2],[3]
Previously, many variables like age, height, weight, abdominal girth, body mass index (BMI), and vertebral column length (VCL) have been used to predict the spread of spinal anesthesia with inconsistent results.[4],[5],[6],[7] Anatomical and hormonal factors along with individual variations have been found to influence the uniform intrathecal spread of local anesthetics.[8] Body shape metrics influence the anatomy of the spinal canal and intra-abdominal pressure resulting in significant effects on the cephalad spread of spinal anesthesia.[9]
An increase in the maternal abdominal circumference during pregnancy which correlates with the intra-abdominal volume, influences the fetus size, volume of amniotic fluid, and size of the uterus. These factors, along with supine position, cause the gravid uterus to have a compressive effect on the inferior vena cava (IVC), diverting blood into the vertebral venous system and displacing the lumbosacral cerebrospinal fluid (CSF) in a cranial direction, which causes enhanced cephalad spread of local intrathecal anesthetic.[10],[11],[12]
VCL/AC2 is considered as the most relevant among various parameters, as Lee et al.[13] postulated that Trunk Length (TL)/ Abdominal circumference (AC)2 simulated the ratio of the long axis and transaction area of the abdomen and had more power to predict the spread of spinal anesthesia. The anatomical widening of hips and laxation of symphysis pubis due to gestational hormones and the increased hip/shoulder width (HSR) also play a role in the cephalad spread of spinal anesthesia.[14]
Based on these facts, we designed a prospective observational study to evaluate the relationship of abdominal circumference, vertebral column length, and hip/shoulder width ratio with the spread of a fixed dose of hyperbaric bupivacaine during spinal anesthesia in term parturients undergoing cesarean section. The primary outcome of this study was the relationship of the spread of spinal anesthesia with abdominal circumference, vertebral column length, and hip/shoulder width ratio. The secondary outcome measures evaluated sensory and motor block characteristics, the incidence of hypotension, the requirement of vasopressor, and side effects.
Material and MethodsAfter obtaining approval from the Institutional Research Ethical board (GU/HREC/EC/2019/1576) and written informed consent, this prospective observational study was conducted from January 2019 to June 2020. A total of 220 parturients aged 18–40 years, at term (≥ 37 weeks gestation), American Society of Anaesthesiologists (ASA) physical status I and II, undergoing elective cesarean section under spinal anesthesia, were assessed for eligibility [Figure 1].
Parturients with medical comorbidities (hypertension, cardiac disorders, renal and hepatic disorders), obstetric comorbidities (preeclampsia/eclampsia, gestational diabetes mellitus, twin pregnancy), and fetal abnormalities were excluded from the study. Patients having a contraindication to spinal anesthesia and known allergy to study drugs were also excluded from the study.
Parturients were explained about anthropometric measurements and spinal anesthesia (SA) a day prior to surgery. Parturients were kept fasting for eight hours for both solids and liquids. On the day of surgery, intravenous (IV) cannulation was done with an 18-gauge cannula in the pre-anesthetic room, and anthropometric measurements were taken by the anesthesiologist who was not involved in giving spinal anesthesia and data collection. The abdominal girth was measured at the level of the umbilicus at the end of expiration in the supine position. Vertebral column length was measured from the C7 prominence to Sacral hiatus (C7-SH) and to Iliac crest (C7-IC) in a sitting position. Hip width was measured as the highest point between two iliac crests, and shoulder width was measured between the two acromion processes. Hip/shoulder width ratio and VCL/AC2 were calculated [Figure 2]. Ringer Lactate solution @10 mL/kg was infused over 30 minutes before SA in the pre-operative room. Patient was shifted to the operating room, and baseline values of hemodynamic variables [Heart rate (HR), Systolic blood pressure (SBP), Diastolic blood pressure (DBP), Mean arterial pressure (MAP)] were recorded.
Figure 2: Anatomical landmarks for the anthropometric measurements. C7: spinous process of C7 vertebra, (a): acromion process, (b); distance from acromion process to midline, (c): distance from the iliac crest to midline, IC: iliac crest, SH: sacral hiatus, C7-IC: distance from C7 vertebra prominence to the iliac crest, C7-SH: distance from C7 vertebra prominence to sacral hiatusSpinal anesthesia was performed by an anesthesiologist who was not involved in anthropometric measurements in the left lateral position at L2-L3 or L3-4 with 2 ml 0.5% hyperbaric bupivacaine after the free flow of cerebrospinal fluid was obtained by a 25 G Quincke spinal needle. The parturient was placed in the supine position with left uterine displacement and the operating table at 10° Trendelenburg position. Oxygen (6 L/min) was administered to all parturients through a face mask intraoperatively. Vital parameters and spinal anesthesia characteristics were recorded by the same anesthesiologist who had given spinal anesthesia and was blinded to parturients measurement data. The cephalad spread of spinal anesthesia was assessed by loss of pinprick discrimination bilaterally in the midclavicular line using a 24 G needle at 1 min interval following spinal anesthesia. The onset of sensory block was recorded as the time to achieve a sensory block level up to T10, and the surgery was allowed to commence after the T4 level was achieved. Maximum sensory block was defined as the highest level of sensory block, which remained unchanged for three consecutive assessments. Time to reach maximum sensory block and time to reach T4 level was recorded.
Motor block was assessed using Modified Bromage score at 1 min interval till score 3 was achieved (0 = no motor loss, 1 = inability to flex the hip, 2 = inability to flex the knee, and 3 = inability to flex the ankle). Hemodynamic parameters like Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and oxygen saturation (SpO2) were recorded at the time of drug administration and at 2-min intervals up to 10 min, followed by 5-min interval till the end of surgery.
Hypotension was defined as a decrease in SBP >20% from baseline or SBP <90 mmHg and was treated with a bolus dose of ephedrine 3 mg intravenously along with a bolus of 200 ml of Ringer Lactate. Bradycardia was defined as HR <50 beats/min and was treated with atropine 0.6 mg intravenously. Tramadol (100 mg) was used to treat intraoperative shivering and pain, whereas nausea and vomiting were treated with ondansetron (4 mg IV). For failed spinal anesthesia where the parturient could not achieve any sensory and motor block even after 5 min of spinal anesthesia, General Anesthesia (GA) was administered, and these patients were excluded from the study.
Statistical analysis
The sample size calculation was based on the need to detect an anticipated effect size (P = 0.15) for the regression equation with a 95% confidence level, power of study of 80%, and 5% absolute error, so the minimum number required was 196. We increased the sample size to 220 patients to take care of attrition rates.
Data was presented as mean, standard deviation, median (range), or percentage as appropriate. Statistical analysis was performed using the Statistical Package for Social Sciences (SPSS) package (version 17, SPSS, Chicago, IL). The correlation between the cephalad spread of spinal anesthesia and the age, height, weight, BMI, abdominal circumference, HSR, and VCL (C7-SH and C7-IC) were analyzed using linear regression analysis. R2 was the coefficient of determination of linear regression analysis, and P value < 0.05 was considered significant.
ResultsOut of 205 parturients enrolled for the study, five parturients underwent GA and were excluded from the study. So a total of 200 parturients were included in this study and analyzed [Figure 1]. The demographic and anthropometric variables are summarized in [Table 1]. Sensory and motor block characteristics are shown in [Table 2]. Sensory block height of T4 was achieved in maximum parturients (n = 171, 85.5%), while T5 and T3 were achieved in nine parturients (4.5%) and 20 parturients (10%), respectively.
There was a significant correlation (P < 0.05) between the cephalad spread of spinal anesthesia and height, weight, and BMI of parturients, while age did not have a significant correlation (P > 0.05) [Table 3].
Table 3: Correlation between parturients variables and cephalad spread of spinal anesthesiaThe hip and shoulder-width ratio (HSR) individually had no significant correlation with the cephalad spread of spinal anesthesia (P > 0.05) [Figure 3], while the abdominal circumference was significantly correlated (P < 0.05) to the height of the block [Table 3] and [Figure 4].
Figure 3: Linear regression analysis of Hip shoulder width ratio and cephalad spread of spinal anesthesia
Figure 4: Linear regression analysis of abdominal circumference and cephalad spread of spinal anesthesiaThe correlation between vertebral column length (C7-SH and C7-IC) and the cephalad spread of spinal anesthesia was found to be significant with the onset of sensory block, the maximum level of sensory block, and time to reach the maximum level of sensory block (P < 0.05), whereas it was found to be non-significant with the time to reach the T4 level (P > 0.05) [Table 3] and [Figure 5] and [Figure 6].
Figure 5: Linear regression analysis of VCL (C7-SH) and cephalad spread of spinal anesthesia
Figure 6: Linear regression analysis of VCL (C7- IC) and cephalad spread of spinal anesthesiaThe correlation between VCL/AC2 and the cephalad spread of spinal anesthesia was found to be significant with the maximum level of sensory block, time to reach the maximum level of sensory block, and the time to reach the T4 level (P < 0.05), whereas it was found to be non-significant with the onset of sensory block (P > 0.05) [Table 3] and [Figure 7].
Figure 7: Linear regression analysis of VCL/AC2 and cephalad spread of spinal anesthesiaThe incidence of hypotension was found in 85.5% of the parturients, while one had bradycardia.
DiscussionThe spread of spinal anesthesia is unpredictable, so a higher level of block may cause hemodynamic instability, while inadequate block may increase the incidence of general anesthesia leading to higher rates of morbidity and mortality.[15] Several factors such as the dose and characteristics of local anesthesia, parturients anthropometric measurements, intraabdominal pressure, and changes in the anteroposterior diameter of the spine affect the extent of spinal anesthesia in obstetric patients.[16] Other factors include pregnancy-induced physiological, biochemical, hormonal, and anatomical changes, which can also influence the spread of spinal anesthesia.[9] Excessive block or incomplete surgical anesthesia highlights the importance of finding appropriate individualized doses of local anesthetic.
The correlation of the spread of spinal anesthesia with demographic data (weight, height, and BMI) was found to be significant (P < 0.05), while age had no significant correlation in our study, as also seen by other authors.[17],[18] However, Seyhan TO et al.[19] and Norris et al.[4] did not find any correlation with height, which might be due to variation in sample size, racial differences causing differences in demographic measurements, and higher dose used (12.5 mg and 15 mg hyperbaric bupivacaine, respectively).
The increased abdominal circumference can be associated with increased intra-abdominal pressure, which might reduce lumbosacral cerebrospinal fluid volume, which is one of the most important determinants of cephalad spread of spinal anesthesia.[20] Various studies have also proven that soft tissues in parturients may migrate into the vertebral canal through the intervertebral foramina along with engorgement of extradural venous plexus, which occurs due to obstruction of the inferior vena cava by the gravid uterus when the parturient lies in the supine position, which is also one of the major causes of cephalad spread of spinal anesthesia.[8],[10],[11] The correlation of abdominal circumference and vertebral column length (both C7-SH and C7-IC) with the onset of sensory block, the maximum level of sensory block, and time to reach the maximum level of sensory block level was found to be highly significant in our study. Zhou QH et al.[21] and Wei CN et al.[22] also noted similar results in two separate studies conducted in pregnant and non-pregnant patients. In their study on non-pregnant patients,[21] they found that abdominal circumference (AC) correlated more with the spread of spinal anesthesia as compared to VCL (0.821 vs. -0.243), while a study on pregnant patients by the same authors found that VCL correlates more than AC with the spread of spinal anesthesia (0.711 vs. 0.372). They attributed this to the larger individual variation in AC in non-pregnant patients compared to VCL, while in pregnant patients, lesser individual variation was observed in AC. Similarly, another study also showed a statistically significant correlation between the abdominal circumference and the cephalad spread of spinal anesthesia (P < 0.05).[17] Other authors have also found that the parturient's vertebral column length (C7-SH) had a significant predictive value in determining the cephalad spread of spinal anesthesia.[5],[18],[23]
No significant correlation between the spread of anesthesia and AC was found by Ahad B et al.[23] but they found a trend towards a higher level of anesthesia being associated with increased AC though it did not reach statistical significance. The authors used isobaric ropivacaine (0.75%; 15 mg) with fentanyl (15 μg), and correlation was done with the maximum height of the spinal block.
In contrast to our findings, some authors have found no significant correlation between VCL and cephalad spread of spinal anesthesia.[4],[13],[14],[24],[25] These differences could be due to racial differences in vertebral column anatomical configuration, the physiological spread of hyperbaric or isobaric solutions, and their doses.
Physiological and hormonal factors affect the bony structures of the parturients pelvis during pregnancy, resulting in an increased hip size and laxation of symphysis pubis for the passage of the fetus. This increase in hip-width causes the trunk to gain a relative Trendelenburg position. Thus, increased HSR may result in a greater cephalad spread of local anesthetic drug during spinal anesthesia, which has been found to be an important variable altering the cephalad spread of spinal anesthesia.[14],[26]
The hip width (HW) and shoulder width (SW) in our study had a significant positive correlation with the characteristics of sensory block (P < 0.05) and a highly significant positive correlation with time to reach the T4 level (P < 0.001). The hip/shoulder width ratio (HSR) had no significant correlation with the cephalad spread of spinal anesthesia (P > 0.05). Hip width was also found to have a positive correlation with the cephalad spread of spinal anesthesia (P = 0.037) by Cantürk et al.[14] but they also found a significant correlation of HSR with the spread of spinal anesthesia (0.009) which could be because they correlated HSR only with the maximum sensory block height.
The correlation of VCL/AC2 was found to have a highly statistically significant correlation with the maximum level of sensory block and time to reach the maximum level of sensory block (P < 0.0001), while a weak correlation with the time to reach the T4 level (P = 0.04) and non-significant with the onset of sensory block (P = 0.206). Similarly, Lee YH et al.[13] found that VCL/AC2 had a positive correlation with the maximum level of sensory block (P < 0.02).
Limitations of our study: Firstly, fixed doses of local anesthetics were used in this study; individualized doses according to patient variables in the parturient may provide better predictive power for the spread of spinal anesthesia. Secondly, the height of the block is not the only measure of adequate anesthesia; hence, further studies should also include time to two-segment regression of the block and correlate it with different patient variables and individualized doses of local anesthetics. Thirdly, the measurement of intraabdominal pressure and its correlation with demographic characteristics will provide more information along with abdominal girth regarding the spread of spinal anesthesia.
ConclusionThe abdominal circumference, Hip width, Shoulder width, VCL, and VCL/AC22 was found to have a significant correlation with the spread of spinal anesthesia with a fixed dose of hyperbaric bupivacaine in term parturients undergoing elective cesarean section. There was no significant correlation between Hip/shoulder width ratio (HSR) and the spread of spinal anesthesia.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
Comments (0)