Cardio-vascular reserve index (CVRI) during exercise complies with the pattern assumed by the cardiovascular reserve hypothesis

Can cardiovascular reserve index (CVRI) on arrival to the trauma unit detects massive hemorrhage and predicts developing hemorrhage? observational prospective cohort study

BACKGROUND

The detection of haemorrhage in trauma casualties may be delayed owing to compensatory mechanisms. This study aimed to evaluate whether the cardiovascular reserve index (CVRI) on arrival detects massive haemorrhage and predicts haemorrhage development in trauma casualties.

METHODS

This was an observational prospective cohort study of adult casualties (≥18 years) who were brought to a single level-1 trauma centre, enroled upon arrival and followed until discharge. Vital signs were monitored on arrival, from which the CVRI and shock index were retrospectively calculated (blinded to the caregivers). The outcome measure was the eventual haemorrhage classification group: massive haemorrhage on arrival (MHOA) (defined by massive transfusion on arrival of ≥6 [O+] packed cells units), developing haemorrhage (DH) (defined by a decrease in haemoglobin >1 g/dl in consecutive tests), and no significant haemorrhage noted throughout the hospital stay. The means of each variable on arrival by haemorrhage group were evaluated using the analysis of variance. The authors evaluated the detection of MHOA in the entire population and the prediction of DH in the remainders (given that MHOA had already been detected and treated) by C-statistic predefined strong prediction by area under the curve (AUC) greater than or equal to 0.8, P less than or equal to 0.05.

RESULTS

The study included 71 patients (after exclusion): males, 82%; average age 37.7 years. The leading cause of injuries was road accident (61%). Thirty-nine (54%) patients required hospital admission; distribution by haemorrhage classification: 5 (7%) MHOA, 5 (7%) DH, and 61 (86%) no significant haemorrhage. Detection of MHOA found a strong predictive model by CVRI and most variables (AUC 0.85-1.0). The prediction of DH on arrival showed that only lactate (AUC=0.88) and CVRI (0.82) showed strong predictive model.

CONCLUSIONS

CVRI showed a strong predictive model for detection of MHOA (AUC>0.8) as were most other variables. CVRI also showed a strong predictive model for detection of DH (AUC=0.82), only serum lactate predicted DH (AUC=0.88), while all other variables were not found predictive. CVRI has advantages over lactate in that it is feasible in pre-hospital and mass casualty settings. Moreover, its repeatability enables detection of deteriorating trend. The authors conclude that CVRI may be a useful additional tool in the evaluation of haemorrhage.

The Cardiovascular Reserve Index-A Noninvasive Clinical Insight Into Heat Intolerance

OBJECTIVE

To noninvasively explore the heat intolerance condition during exercise-heat stress by assessing cardiovascular (CV) performance.

DESIGN

Prospective study of participants undergoing a standard heat-tolerance test (HTT).

SETTING

Institutional study.

PARTICIPANTS

Ninety-five young males: 16 heat-intolerant (HI) and 79 heat-tolerant (HT).

INTERVENTIONS

Cardiovascular performance during an HTT was estimated by heart rate (HR) and blood pressure measurements.

MAIN OUTCOME MEASURES

The sensitivity of the cardiovascular reserve index (CVRI) and the dynamic heart rate reserve (dHRR) index to predict heat intolerance was compared.

RESULTS

A significant difference in the CV reserve during exercise-heat stress was exhibited between the HI and the HT groups. Starting at a similar level, the reduction in the CV reserve at HTT endpoint was much greater in the HI than the HT individuals (P < 0.0001), as depicted by both the CVRI and the dHRR. This result indicates a greater utilization of the CV reserve by HI individuals. The CVRI is likely to be better predictor of heat intolerance than the dHRR because the partial area under the curve in the high sensitivity (>90%) region of its receiver operating characteristic curve is higher (93.2 vs 76.8).

CONCLUSIONS

More than being a predictor, the CVRI may provide a new clinical insight into heat intolerance because it noninvasively characterizes the efficiency of an individual's thermoregulatory mechanism and hints that an impaired CV reserve might underlie heat intolerance. The CVRI provides a noninvasive measurement of thermoregulation, which has been long awaited to enable on-field studies and dynamic monitoring of heat-exposed task forces.