Analysis of Changes in Right Ventricular Systolic Function by Point-of-Care Ultrasound in Patients Undergoing Corrective Surgeries for Femur Fracture.

BACKGROUND: Fat embolism syndrome (FES) following major orthopedic injuries and surgeries is a well-known phenomenon where acute depression of right ventricular (RV) systolic function is a potential possibility. Clinical presentation of FES may vary from mild self-limiting nature to severe life-threatening multiorgan dysfunction syndrome with pulmonary manifestations being most common. AIMS: This study was aimed to know whether perioperative assessment of RV function by measuring tricuspid annular plane systolic excursion (TAPSE) with point-of-care transthoracic echocardiogram will identify patients at risk of developing FES and its sequelae. SETTINGS AND
DESIGN: This was a prospective observational study.
MATERIALS AND METHODS: This study was carried out in 142 patients with femur fractures posted for correction surgeries of both genders who require intramedullary (IM) reaming. TAPSE was recorded four times perioperatively. Time taken for IM reaming was also recorded. STATISTICAL ANALYSIS USED: Recorded data were analyzed using professional statistics package Epi Info 7.0 version for Windows. Descriptive data were represented as mean ± standard deviation for numeric variables, percentages, and proportions for categorical variables. Repeated-measure ANOVA was applied to assess the changes in TAPSE from baseline to immediate postoperative, after 6-h postoperative, and after 24-h postoperatively. Pearson's correlation was utilized to be applied to assess the relationship between TAPSE and other numerical variables.
RESULTS: All four readings of TAPSE were well above 17 mm (mean of 19.06, 19.05, 19.04, and 19.04, respectively). Mean reaming time was found to be 6.92 min. None of the patients developed any postoperative pulmonary complications.
CONCLUSION: Assessment of RV function can be done with relative ease using TAPSE as a noninvasive method without any complications. Reaming time not exceeding 12 min did not produce any changes in RV function as measured by TAPSE as well as any postoperative pulmonary complications.

INTRODUCTION

Significance of assessing right ventricular (RV) systolic function is gaining importance due to its better prognostic value.[1] This is because unlike left ventricle, determination of chamber volume is not much reliable in RV owing to its complex anatomical shape, hence functional assessment becomes more important.[2]

Although routine perioperative monitoring of RV function is not necessary, it might be beneficial in few clinical conditions where alterations in RV function is likely to occur. Fat embolism syndrome (FES) following major orthopedic injuries and surgeries are one such condition where acute depression of RV systolic function is a potential possibility. Clinical presentation of FES may vary from mild self-limiting nature to severe life-threatening multiorgan dysfunction syndrome.[3] Clinical effects of FES can be attributed to altered pulmonary mechanics, especially to pulmonary vascular resistance (PVR). As PVR is the major determinant of RV systolic function, assessment of RV function may play a role in predicting pulmonary complications in patients with FES.[4] Alteration in RV systolic function due to changes in PVR has been well established.[5]

Although the gold standard method of assessment of PVR is by the right heart catheterization, it may not be practical to use it as a routine tool due to its invasiveness. Point-of-care echocardiogram to assess the RV systolic function may be an alternate option as it reflects the changes of PVR. Moreover, due to its noninvasive nature, it may be an attractive alternate. Thus, we hypothesize, assessment of RV systolic function, may provide newer insights in detecting altered pulmonary hemodynamics which may predict the occurrence of pulmonary complications during or after orthopedic surgeries involving the long bones.

The aim of the study is to evaluate the changes in RV systolic function pre- and postoperatively using tricuspid annular plane systolic excursion (TAPSE) in patients undergoing correction surgeries for femur fracture with intramedullary (IM) reaming and to estimate the incidence of pulmonary complications among these patients in the first 24-h postoperatively.

MATERIALS AND METHODS

This prospective observational study was carried out after obtaining approval from the Institutional Ethics Committee (IEC/PP/2017/27). Continuous 142 patients with femur fractures posted for correction surgeries, belonging to the American Society of Anesthesiologists physical status Classes I and II, with age above 18 years of both genders were included in the study. Patients with preexisting cardiac diseases were not included. First TAPSE values were measured and recorded in the preoperative holding area to note the basal RV systolic function through transthoracic echocardiogram (TTE) (model: M-Turbo Fujifilm sonosite, inc., USA) by anesthesiologist who has undergone special training in transthoracic echocardiogram.

After recording baseline TAPSE values, patients were shifted to operating room (OR). Inside OR, all of them were monitored for hemodynamic and respiratory parameters (electrocardiogram [ECG], noninvasive blood pressure [NIBP], SpO2, and respiratory rate) continuously and recorded every 5 min. All patients enrolled in the study received regional anesthesia in the form of subarachnoid block with 3 ml of hyperbaric bupivacaine 0.5% (injection Anawin Heavy™, Neon Laboratories, India) to achieve a sensory block up to of T8–T10 (Thoracic vertebral level). TAPSE measurements were repeated immediately after the procedure (T2). The third reading was done at 6 h (T3) and fourth reading was done at 24-h (T4) intervals after completion of the operative procedure. Intraoperative TAPSE measurement was also planned if there would be any hemodynamic or respiratory alterations which were defined as 25% deviation from baseline of hemodynamic parameters or fall in saturation below 94%. The duration of IM reaming was also noted.

TAPSE values were acquired by placing an M-mode cursor through the lateral tricuspid annulus and measuring the amount of longitudinal motion of the annulus in peak systole in apical four-chamber view as shown in Figure 1. A cutoff value of TAPSE >16 mm was considered as indicative of normal RV function and <16 mm was suggestive of impaired RV function as per the criteria suggested by the American Society of Echocardiography (ASE).[6] Postoperatively, all patients were observed with standard postoperative monitoring parameters for the subsequent 24 h. Alterations in hemodynamic or respiratory parameters during that period were noted and treated as per the standard guidelines.

Figure 1

Measuring tricuspid annular plane systolic excursion in apical 4 chamber view

Sample size

Sample size was calculated using n = ([Z1]2 (P [1 − P]))/d2 with proportion of patient developing pulmonary complication as 10.25%,[3] with precision of 5%. Estimated sample size for 95% confidence interval was found to be 142.

Statistical analysis

Data entry was done in MS Excel Spreadsheet 2010. Recorded data were analyzed using professional statistics package Epi Info 7.0 version (Epi Info™ a database and statistics program for public health professionals, CDC, Atlanta, GA, USA) for Windows. Descriptive data were represented as mean ± standard deviation for numeric variables, percentages, and proportions for categorical variables. Repeated-measure ANOVA was applied to assess the changes in TAPSE from baseline to immediate postoperative, after 6-h postoperative, and after 24-h postoperatively. Pearson's correlation was utilized to be applied to assess the relationship between TAPSE and other numerical variables. Values of P < 0.05 are considered statistically significant.

RESULTS

One hundred and forty-two consecutive patients with femur fracture undergoing correction surgeries to our tertiary care hospital between March 2017 and November 2018 were included in the study; the mean age of the study population was found to be 32.82 ± 10.516 (18–72), and 77 patients were female and 65 were male. [Table 1] All patients underwent successful surgery for femur fracture during hospitalization. The mean time to surgery from the day of admission was 3.22 ± 1.629. Preoperative arterial blood gas analysis was within normal limits in all the patients. The mean femur reaming time was 6.92 ± 2.355 min [Table 2]. All four readings of TAPSE were well above 17 mm [Table 3] (mean of 19.06, 19.05, 19.04, and 19.04, respectively). None of the patients had any significant deviation in hemodynamic or oxygenation status as measured by ECG, NIBP, and pulse oximeter.

Table 1

The demographic details and other observations

Patient characteristics	Observations
Age (mean)	18-72 (32.82)
Gender distribution (male/female)	65:77
Reaming time in minutes (mean)	3-12 (6.92)
Hemodynamic alterations	Nil
Pulmonary complications	Nil

Table 2

The values of tricuspid annular plane systolic excursion done through the study period

TAPSE readings	Mean±SD	P
T1	19.06±1.749	0.501
T2	19.05±1.727
T3	19.04±1.723
T4	19.04±1.725

The variations between the four values were not found to be statistically significant. TAPSE=Tricuspid annular plane systolic excursion, SD=Standard deviation

Table 3

The correlation between the tricuspid annular plane systolic excursion values with age, and mean reaming time values and the observations showed no significant correlation between them

Variables	Statistical correlation and significance	T 1	T 2	T 3	T 4
Age (n=142)	Pearson correlation	0.011	0.032	0.034	0.027
	P	0.897	0.704	0.691	0.753
Reaming time (n=142)	Pearson correlation	−0.054	−0.065	−0.060	−0.059
	P	0.523	0.440	0.475	0.489

DISCUSSION

Embolization of fat droplets is a common phenomenon following traumatic orthopedic injuries and surgeries, especially involving femur fractures.[37] Although IM nailing is considered as primary stabilization modality for long bone fractures, the procedure itself can result in rise of IM pressure causing further release of bone marrow and fat droplets into the venous system that can lead to potentially lethal consequences.[7]

FES is said to occur following an insult associated with the release of fat into the circulation and its incidence varies widely from 1% to 30%.[8] Although fat embolization is of little consequence in vast majority of patients, it can enter the pulmonary vasculature to cause mechanical obstruction in few patients which can lead to obstruction of blood flow in pulmonary capillaries producing ventilation-perfusion mismatch and altered pulmonary hemodynamic that can contribute to pulmonary complications and multisystem dysfunction at times.[9] As most common initial signs of FES are of pulmonary manifestations,[8] the same was considered as our secondary objective.

Although FES is a clinical entity, various investigative modalities ranging from hematological investigations to imaging techniques have been tried to confirm the diagnosis with varied success. However, not many techniques or tests have been proposed to detect or predict FES in perioperative period, especially during surgical intervention. Release of showers of emboli during IM reaming and nailing had been detected with transesophageal echocardiography (TEE) intraoperatively.[10] However, the availability and expertise needed for performing TEE as well as poor correlation of clinical impact and emboli load[11] preclude its routine use during the perioperative period. For these reasons, we designed this study to look at the effects of embolization on pulmonary hemodynamics rather than simply detecting them. The effects of embolization have been attributed, not only from the mechanical effects but also due to the effects of pro-inflammatory mediators released from pulmonary endothelium, secondary to embolization.[8] Although direct measurement of PVR by the right heart catheterization, is the best method, assessment of effects of elevated PVR (alteration of RV systolic function) at point-of-care by TTE due to its a noninvasive nature will be more acceptable to evaluate these type of patients, especially to direct the treatment strategies.

Several echocardiographic methods have been proposed to rapidly and routinely analyze RV performance such as two-dimensional evaluation of fractional shortening area in four-chamber view, M-mode measurement of TAPSE, and more. The measurement of TAPSE is a simple echocardiographic parameter which reflects RV systolic function. It is not dependent on either geometric assumptions or traceable endocardial edges. Despite its simplicity, utility of TAPSE by TTE has never been validated in the perioperative settings for assessment of RV function involving long bone fracture surgeries to the best of our knowledge. Hence, we undertook this study to assess the RV function and its alteration during the long bone fracture surgeries with TAPSE as point-of-care parameter.

TAPSE has been shown to correlate strongly with radionuclide angiography, with low interobserver variability in a study by Kaul et al.[12] It has also been validated against biplane Simpson RV ejection fraction and RV fractional area shortening in normal individuals.[1314] In a study of 750 patients with a variety of cardiac conditions, compared with 150 age-matched normal controls, a TAPSE cutoff value <17 mm yielded high specificity though low sensitivity to distinguish abnormality from normal individuals.[1] However, the ASE guidelines define that TAPSE of <16 indicates RV dysfunction. In total, there have been >40 studies with >2000 normal individuals being evaluated with the utility of TAPSE. Therefore, TAPSE can be used as a simple bedside method of assessing the RV function at point of care. Furthermore, TAPSE is simple, less dependent on optimal image quality, reproducible, and it does not require sophisticated equipment or prolonged image analysis.[6] The prognostic value of TAPSE at point of care has also been studied Zanobetti et al. in 120 consecutive patients presented to emergency department with acute pulmonary embolism with positive outcome.[15] Considering its simplicity, ease of performing at the bedside, reliable and minimal interobserver variability, we used this tool for assessing the RV function perioperatively.

In our study, TAPSE was used as a point-of-care parameter to detect RV dysfunction in the perioperative settings. The first observation made during the study was, ease of recording these values in OR, and we did not encounter any difficulty in performing TAPSE. The fact that the values were easily obtainable at any point of time during the study underlines that with reasonable training; anesthesiologists can very well perform point-of-care hemodynamic assessments with TTE. During the study period, none of the patients had any alteration in TAPSE values as well as clinical features suggestive of any type of pulmonary complications. It is notable from our analysis that unaltered RV function as observed with TAPSE values above 19.05 (mean) will be associated with good postoperative outcome. Although there are few controversies regarding the association of IM nailing with fat embolism, we found that IM reaming time of <12 min (mean of 6.92) did not produce any significant changes in RV systolic function and also not associated with any postoperative pulmonary complications. As none of our patients had low TAPSE values (<16), we could not comment about its utility in predicting postoperative pulmonary complications arising secondary to alteration in pulmonary mechanics following femur surgeries.

Limitations

The major limitation of this study is its relatively a small sample size and involving only a single center. Moreover, the positive predictive value of TAPSE for pulmonary complications could not be established as none of our patients had any alteration in RV systolic function or pulmonary complications. A large-scale or a multicentric study with more patients may help to identify the patients who are at risk of developing pulmonary complications, by using this simple bedside parameter which will provide useful information.

CONCLUSION

The availability of point-of-care ultrasonography has made it easier and simpler to assess the patients in real time in the perioperative period for RV systolic function. Assessment of RV function can be done with relative ease using TAPSE as a noninvasive method without any complications. IM reaming time of <12 min has not been shown to be associated with any change in RV systolic function or postoperative pulmonary dysfunction. Patients with normal RV function measured by TAPSE are unlikely to develop any postoperative pulmonary complications. Since none of our patients developed perioperative hemodynamic or pulmonary complications, association of changes in RV function in predicting pulmonary complications could not be commented.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.