Risk factors for hypotension in regional spinal anesthesia for cesarean section. Role of the Waist-to-Hip Ratio and Body Mass Index
Because of its incidence, hypotension under spinal anesthesia has been the subject of study and debate. Studies have been aimed at defining risk factors, clarifying pathophysiology, and creating prophylaxis and management protocols. There are no studies of anthropometric measurements, such as waist-to-hip ratio (WHR) and body mass index (BMI), associated with maternal hypotension. The higher the content of the abdominal cavity, the greater the likelihood of aorto-caval compression syndrome and the higher the risk of hypotension.
To determine if the WHR and the BMI correlate with the probability of developing hypotension in pregnant women undergoing cesarean section under subarachnoid anesthetic block.
Materials and methods:
A prospective cohort study of 231 women undergoing cesarean section under regional anesthesia. Anthropometric measurements were made before anesthesia, and vital signs were recorded during the procedure at predetermined time points to analyze the hemodynamic status. Hypotension was defined as a systolic blood pressure below 90 mm Hg.
The incidence of hypotension was 38%; 45.8% of the women had a WHR >0.99, with an incidence of 21.7% versus 15.2%, and a nonsignificant risk ratio of 2.12 (95% confidence interval [CI] 1.52-3.54, P = 0.021). Women with a BMI >29 had an incidence of 42.8% versus 57.14%, without a significant difference (P = 0.576). There was a significant association between the weight of the newborn >3900g and the risk of hypotension (relative risk 2.12, 95% CI 1.52-3.54, P = 0.021).
There was no positive correlation between WHR and BMI, and the risk of developing hypotension. The weight of the newborn must be further analyzed in future studies.
2. Rout CC, Rocke DA, Levin J, et al. A re-evaluation of the role of crystalloid preload in the prevention of hypotension associated with spinal anesthesia for elective cesarean section. Anesthesiol-ogy 1993;79:262-269.
3. KlOhr S, Roth R, Hofmann T, et al. Definitions of hypotension after spinal anaesthesia for caesarean section: literature search and application to parturients. Acta Anaesthesiol Scand 2010;54: 909-921.
4. Khaw KS, Ngan Kee WD, Wy Lee S. Hypotension during spinal anaesthesia for caesarean section: implications, detection prevention and treatment. Fetal Matern Med Rev 2006;17: 1-27.
5. Liu H, Huang Y, Diao M, et al. Determination of the 90% effective dose (ED90) of phenylephrine for hypotension during elective cesarean delivery using a continual reassessment method. Eur J Obstet Gynecol Reprod Biol 2015;194:136-140.
6. Mercier FJ, Augè M, Hoffmann C, et al. Maternal hypotension during spinal anesthesia for caesarean delivery. Minerva Anestesiol 2013;79:62-73.
7. Tawfik MM, Hayes SM, Jacoub FY, et al. Comparison between colloid preload and crystalloid co-load in cesarean section under spinal anesthesia: a randomized controlled trial. Int J Obstet Anesth 2014;23:317-323.
8. Ngan Kee WD. Prevention of maternal hypotension after regional anaesthesia for caesarean section. Curr Opin Anaesthesiol 2010;23:304-309.
9. Maayan-Metzger A, Schushan-Eisen I, Todris L, et al. Maternal hypotension during elective cesarean section and short-term neonatal outcome. Am J Obstet Gynecol 2010;202:56e1-56e5.
10. O'Brien TE, Ray JG, Chan W-S. Maternal body mass index and the risk of preeclampsia: a systematic overview. Epidemiology 2003;14:368-374.
11. Callaway LK, Prins JB, Chang AM, et al. The prevalence and impact of overweight and obesity in an Australian obstetrics population. Med J Aust 2006;184:56-59.
12. Baeten JM, Bukusi EA, Lambe M. Pregnancy complications and outcomes among overweight and obese nulliparous women. Am J Public Health 2001;91:436-440.
13. Saravanakumar K, Rao S, Cooper G. Obesity and obstetric anaesthesia. Anesthesia 2006;61:36-48.
14. Vasan RS. Cardiac function and obesity. Heart 2003;89:1127-1129.
15. Singla D, Kathuria S, Singh A, et al. Risk factors for development of early hypotension during spinal anaesthesia. J Anaesthesiol Clin Pharmacol 2006;22:387-393.
16. Racle JP, Haberer JP, Benkhadra A, et al. A comparison of cardiovascular responses of normotensive and hypertensive elderly patients following bupivacine spinal anesthesia. Reg Anesth 1989;14:66-71.
17. Chi-HangKuok,Chung-HsinHuang,Pei-ShanTsai,etal.Preoperative measurement of maternal abdominal circumference relates the initial sensory block level of spinal anesthesia for cesarean section: an observational study. TaiwanJ Obstet Gynecol 2016;55:810-814.
18. Russell IF. Levels of anaesthesia and intraoperative pain at caesarean section under regional block. Int J Obstet Anesth 1995;4:71-77.
19. Qiu MT, Lin FQ, Fu SK, et al. Combination of low-dose bupivacaine and opioids provides satisfactory analgesia with less intraoperative hypotension for spinal anesthesia in cesarean section. CNS Neurosci Ther 2012;18:426-432.