Haemodynamic effects of central neural blocks

Measurements of Inferior Vena Cava Diameter for Prediction of Hypotension and Bradycardia during Spinal Anesthesia in Spontaneously Breathing Patients during Elective Knee Joint Replacement Surgery

Background and objective: Hypotension and bradycardia are the most common hemodynamic disorders and side effects of spinal anesthesia (SA) on the cardiovascular system. SA-induced sympathetic denervation causes peripheral vasodilatation and redistribution of central blood volume that may lead to decreased venous return to the heart. The aim of the study was to evaluate the changes of inferior vena cava collapsibility index (IVC-CI) during SA in spontaneously breathing patients during elective knee joint replacement surgery to prognose manifestation of intraoperative hypotension and bradycardia. Materials and methods: 60 patients (American Society of Anesthesiologists (ASA) physical status I or II, no clinically significant cardiovascular pathology) of both sexes undergoing elective knee joint replacement surgery under SA were included in the prospective study. Inspiratory and expiratory inferior vena cava (IVCin, IVCex) diameters were measured using an ultrasound device in supine position before and immediately after SA, then 15 min, 30 min, and 45 min after SA was performed. The heart rate, along with systolic, diastolic, and mean arterial blood pressures were collected. The parameters were measured at the baseline and at the next four time points. Results: There were no significant changes in IVCin, IVCex, and IVC-CI compared to baseline and other time point measurements in hypotensive versus nonhypotensive and bradycardic versus nonbradycardic patients (p > 0.05). Changes in IVC diameter do not prognose hypotension and/or bradycardia during SA: the area under the curve (AUC) of the receiver operating characteristic (ROC) curve for IVC-CI at all measuring points was <0.7, p > 0.05. Conclusions: Reduction in IVC diameters and increase in IVC-CI do not predict hypotension and bradycardia during SA in spontaneously breathing patients undergoing elective knee joint replacement surgery.

Lithotomy versus jack-knife position on haemodynamic parameters assessed by impedance cardiography during anorectal surgery under low dose spinal anaesthesia: a randomized controlled trial

BACKGROUND

Although the prone position providing better exposure for anorectal surgery is required it can cause a reduction of cardiac output and cardiac index. The goal was to compare haemodynamic changes assessed by impedance cardiography during anorectal surgery under low-dose spinal anaesthesia in lithotomy and jack-knife position.

METHODS

The prospective randomized controlled study included 104, ASA I-II adult patients admitted for elective minor anorectal surgery, assigned to be performed in lithotomy (groupL, n = 52) or jack-knife position (groupJ, n = 52). After arrival to operating room the standard monitoring, impedance cardiography device was connected to the patient, and the following variables were recorded: cardiac output, cardiac index, systemic vascular resistance, stroke index at times of arrival to operating room, placement for, start and end of surgery and placement to bed. Spinal block was made in the sitting position with 4 mg of 0.5% hyperbaric bupivacaine and 10 μg of Fentanyl injected over 2 min. Comparison was based on haemodynamic changes between and inside groups over time. Student's t, chi square tests were used for statistical analysis with p < 0.05 regarded as statistically significant.

RESULTS

The reduction of cardiac output was statistically significant after placement of the patient into the prone position: from baseline 7.4+/-1.6 to 4.9+/-1.2 after placement for and 4.7+/-1.2 at the start and end of surgery (mean +/-SD l/min). The difference of cardiac output between groups was 2.0 l/min after positioning for and the start of surgery and 1.5 l/min at the end of surgery (p < 0.05). Mean cardiac index reduced from baseline 3.9+/-0.8 to 2.6+/-0.7 and 2.4+/-0.6 (mean+/-SD l/min/m(2)) in groupJ and between groups: by 1.0 l/min/m(2) after placement for, 1.1 at the start and 0.8 at the end of surgery (p < 0.05). Systemic vascular resistance increased from baseline 1080+/-338 to 1483+/-479 after placement for, 1523+/-481 at the start and 1525+/-545 at the end of surgery in groupJ (mean+/-SD dynes/sec/cm(-5), p < 0.05).

CONCLUSIONS

According to impedance cardiography, jack-knife position after low-dose spinal anaesthesia produces transitory, but statistically significant reduction of cardiac output and cardiac index with increase of systemic vascular resistance, compared to insignificant changes in lithotomy position.

TRIAL REGISTRATION

Clinical Trials NCT02115178.