Body habitus does not influence spread of sensory blockade after the intrathecal injection of a hypobaric solution in term parturients

Prospective observational investigation of body habitus measurements and relationship to epidural depth in term pregnant women

BACKGROUND

High body mass index (BMI) can predict difficult neuraxial block; however, fat distribution may also be important. The primary study aim was to identify body habitus and fat distribution measurements that correlated with ultrasound measured epidural depth. We hypothesized that measurements such as midarm and subscapular fatpad thicknesses and length of cervical spine may correlate better with ultrasound measured epidural depth than a global measure of BMI.

METHODS

Prospective IRB approved study of term pregnant women requiring neuraxial block. We measured height, weight (BMI, kg/m² ), subscapular, midarm fatpad thickness (digital caliper, mm), vertebral column length (C7 to sacral hiatus, cm) and epidural depth (ultrasound, mm). Four experts assessed photographs to assign anticipated difficult neuraxial block in sitting and lateral positions (5-point Likert scale, 1 = very easy, 5 = very difficult).

RESULTS

In all, 131 women completed body habitus measurements. Measured mean (standard deviation) BMI was 30.3 (5.4) kg/m² . Measured BMI, subscapular fatpad and midarm fatpad thickness were significantly correlated with ultrasound depth to epidural space (R² 0.733, 0.626 and 0.633, respectively, P < .0001) but vertebral column length was not. The experts had a high level of agreement (Cronbach's alpha >0.7) for assessment of anticipated difficult block in the sitting and lateral positions; however, anticipated difficult block was not correlated with epidural depth measured by ultrasound for sitting position, R²  = -0.015, P = .87; and lateral position, R²  = -0.087, P = .33.

CONCLUSIONS

Measurements of body habitus and fat distribution were no better than measured BMI to anticipate greater ultrasound measured depth to epidural space. Clinical trial number: Non-interventional observational study, not registered.

Abdominal girth and dorso-sacral distance can be used to estimate lumbosacral cerebral fluid volume

BACKGROUND

Patients' abdominal girth and vertebral column length are highly correlated with the spread of local anaesthetics after spinal anaesthesia. Lumbosacral cerebrospinal fluid volume is the primary determinant for spinal spread. Thus, we attempted to verify the hypothesis that abdominal girth and dorso-sacral distance are correlated with lumbosacral cerebrospinal fluid volume.

METHODS

Forty-five healthy volunteers were enrolled in this study to measure lumbosacral cerebrospinal fluid volume using magnetic resonance imaging. The age, height, weight, abdominal girth, dorso-sacral distance and lumbosacral cerebrospinal fluid volume of the volunteers were recorded. Multiple linear regression analysis was used to analyse the correlation between age, height, weight, abdominal girth, dorso-sacral distance and lumbosacral cerebrospinal fluid volume.

RESULTS

Two volunteers were excluded because of lumbar disc herniation, leaving 43 volunteers for analysis. Multiple linear regression analysis showed a strong correlation between abdominal girth, dorso-sacral distance and lumbosacral cerebrospinal fluid volume (both P < 0.01). The adjusted R² was 0.644. Volunteers with small abdominal girth showed clear images of cerebrospinal fluid in the nerve root cuff at the intervertebral foramen in the three-dimensional magnetic resonance imaging reconstruction of lumbosacral cerebrospinal fluid, while the images were vague in volunteers with large abdominal girth. Clearer images implied larger lumbosacral cerebrospinal fluid volume, while vaguer images, smaller lumbosacral cerebrospinal fluid volume.

CONCLUSIONS

Multiple regression analysis revealed that abdominal girth and dorso-sacral distance were correlated with lumbosacral cerebrospinal fluid volume. Smaller abdominal girths and larger dorso-sacral distances predict larger lumbosacral cerebrospinal fluid volume.

Pencil-point needle bevel direction influences ED50 of isobaric ropivacaine with fentanyl in spinal anesthesia for cesarean delivery: a prospective, double-blind sequential allocation study

BACKGROUND

There is little evidence on the influence of bevel direction of a pencil-point needle on the median effective dose (ED50) of isobaric ropivacaine and fentanyl in spinal anesthesia for cesarean delivery.

METHODS

In this prospective, double-blind, sequential allocation study, 82 parturients scheduled for elective cesarean delivery under combined spinal-epidural anesthesia were included. We sought to determine the median effective dose of intrathecal 0.75% isobaric ropivacaine plus fentanyl 15μg with two different bevel directions of a 26-gauge Whitacre needle using up-down sequential allocation. Parturients were randomly allocated to either Group Ce (needle aperture oriented in a cephalad direction) or Group Ca (aperture directed caudally). The initial dose was 0.75% ropivacaine 11.25mg plus fentanyl 15μg in both groups. Each dose was classified as effective if, after 15min and during the next 60min, there was inability to appreciate pin-prick as sharp at T4, a visual analogue pain score <2 and no requirement for an epidural rescue bolus.

RESULTS

Eighty patients were included in the analysis. The ED50 in group Ca was significantly higher (13.09mg, 95% CI 12.19-14.00) than in group Ce (10.10mg, 95% CI 9.54-10.65, P <0.001).

CONCLUSION

The orientation of the distal aperture of a 26-gauge Whitacre needle during induction of spinal anesthesia for cesarean delivery influences the ED50 of 0.75% ropivacaine.

Regional anaesthesia in the obese patient: lost landmarks and evolving ultrasound guidance

Obesity is associated with a number of anaesthetic-related risks. Regional anaesthesia offers many potential advantages for the obese surgical patient. Advantages include a reduction in systemic opioid requirements and their associated side effects, and possible avoidance of general anaesthesia in select circumstances, with a lower rate of complications. Historically, performing regional anaesthesia procedures in the obese has presented challenges due to difficulty in identifying surface landmarks and availability of appropriate equipment. Ultrasound guidance may aid the regional anaesthesia practitioner with direct visualisation of underlying anatomic structures and real-time needle direction. Further research is needed to determine optimal regional anaesthesia techniques, local anaesthetic dosage and perioperative outcomes in obese patients.

What’s new and novel in obstetric anesthesia? Contributions from the 2003 scientific literature

THE PREGNANT PATIENT: Age; maternal disease; prophylactic antibiotics; gastroesophageal reflux; obesity; starvation; genotyping; coagulopathy; infection; substance abuse; altered drug responses in pregnancy; physiological changes of pregnancy. THE FETUS: Fetal monitoring; intrauterine surgery. THE NEWBORN: Breastfeeding; maternal infection, fever, and neonatal sepsis evaluation. OBSTETRIC COMPLICATIONS: Embolic phenomena; hemorrhage; preeclampsia; preterm delivery. OBSTETRIC MANAGEMENT: External cephalic version and cervical cerclage; elective cesarean delivery; fetal malpresentation; vaginal birth after cesarean delivery; termination of pregnancy. OBSTETRIC ANESTHESIA: Analgesia for labor and delivery; anesthesia for cesarean delivery; anesthesia for short obstetric operations; complications of anesthesia. MISCELLANEOUS: Consent; ethics; history; labor support; websites/books/leaflets/journal announcements.