Background

: Spinal anesthesia produces hemodynamic changes such as hypotension (described in up to 30% of patients) and bradycardia. The physiology of these changes was studied years ago in animal and experimental human models. At present, transthoracic echocardiography (TTE) can be a useful and modern noninvasive monitor to study what happens with cardiac output (CO) after a subarachnoid block in daily clinical practice.

Objective

: To evaluate the behavior of the CO with the use of TTE after the installation of a spinal anesthesia.

Material and Method

: We prospectively studied ASA I patients proposed for surgery under spinal anesthesia. The baseline CO was studied using the left parasternal window where the diameter of the left ventricular outflow tract was measured and its area was calculated. Then from the apical window in five chamber view the integral of the maximum velocity of the outflow tract (IVT) was measured with continuous Doppler. When IVT was multiplied by its area, the ejection volume (VE) was multiplied by heart rate (HR), obtaining the CO. Spinal anesthesia was then installed using a mixture standardized with 0.5% chirocaine and 20 micrograms fentanyl in a volume between 2.5 and 3 ml. The same echocardiographic examination was done once the installation of the spinal block was verified.

Results

: We studied 52 patients, in only 2 there were no satisfactory echocardiographic windows. The average age was 44.8 ± 11 years. In all cases, surgery was performed with the spinal block. The level of blockade reached was T6 in 36.36% of the cases and T4 in 32.73%. The variations of the systolic, diastolic and heart rate had a statistically significant decrease. No significant difference was observed in the CO before and after spinal anesthesia. The maximum sensory height of the subarachnoid block did not correlate with the decrease in MAP or echocardiographic parameters.

Conclusion

: Spinal anesthesia produced decreased hemodynamic parameters. The use of intraoperative transthoracic echocardiography allowed the direct and real study of cardiovascular physiology and showed that despite the drop in blood pressure and heart rate, the CO tended to remain, probably due to other compensation mechanisms such as increased myocardial contractility and improvement of diastolic function. In the future, TTE can be a study tool to evaluate what happens with different anesthetic drugs and different types of patients (obstetric, cardiopathic).

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