Use of Inferior Venacaval Collapsibility Index in Spinal Anesthesia during Orthopedic Surgeries.

Background: Volume deficit is one of the predictors of hypotension. Inferior venacaval collapsibility index (IVCCI) can detect volume deficit and aids volume resuscitation in patients of intensive care unit. Aims: The primary aim was to compare the incidence of postspinal anesthesia hypotension (PSAH) in IVCCI measured and nonmeasured groups. The secondary aim was to determine IVCCI association with PSAH within IVCCI measured group in spite of fluid bolus. Settings and Designs: This was a prospective, randomized, controlled, single-blinded study. Methodology: One hundred patients posted for orthopedic surgery under spinal anesthesia (SA) were randomly divided as IVCCI measured (CI) and non-IVCCI measured (NCI) groups before SA. If IVCCI was more than 40% fluid bolus was given. Intraoperative hemodynamics was monitored. PSAH managed with fluids and vasopressors which were noted. Data collected were analyzed with unpaired t-test, Z-test, logistic regression test, and Pearson's correlation.
Results: PSAH incidence was 18% in group (CI) whereas 38% in group (NCI), and the difference was statistically significant. Vasopressors given were higher in group NCI. Perioperative fluids were more in group CI, but the intraoperative fluids were more in group NCI. There was no statistically significant association between PSAH after fluid preloading and IVCCI within the IVCCI measured group.
Conclusion: Prespinal anesthesia evaluation of IVCCI to optimize fluid therapy can reduce the incidence of PSAH in orthopedic surgeries and the vasopressor requirement, and hence, the association of IVCCI of more than 40% with PSAH. Copyright:

INTRODUCTION

Ultrasonography (USG) is a boon to modern anesthesia wherein many anesthetic procedures are made easy and accurate. Besides this, its use is even extended to guide fluid therapy in critical care patients through inferior venacaval collapsibility index (IVCCI). Muller et al. and Bortolotti et al. studies showed that the patients with IVCCI more than 40% can be considered as fluid responders in spontaneously breathing patients associated with acute circulatory failure and cardiac arrhythmias, respectively.[12] Huang et al.'s study concluded IVCCI moderate performance to detect hypotension in circulatory collapse patients with mechanical ventilation.[3] There are upcoming studies regarding IVCCI-guided fluid therapy in general and spinal anesthesia (SA).[45] Szabó et al. showed that IVCCI more than 50% can predict post induction hypotension with high specificity during general anesthesia.[5] Finnerty et al.'s study showed a lesser inter individual variation of IVCCI with subxiphoid long axis B-mode than short axis or coronal long axis.[6]

The incidence of post-SA hypotension (PSAH) is 15.3%–33%.[7] PSAH is due to sympathetic denervation which results in peripheral vasodilatation and hence redistribution of central blood volume which eventually decreases preload.[8] PSAH can cause hypoperfusion of several vital organs and its impaired functions. There are several predictors of PSAH of which preoperative volume status is important. This volume status is affected by general physical condition, associated comorbidities, fasting status, or drugs taken by patients.[9] Deficit in volume status can be attended by adequate fluid infusion either by preloading in obstetric cases or by coloading in nonobstetric cases.[1011] Monitored fluid infusion is gaining more attention over blind fluid infusion to avoid fluid overload-related complications. The volume status-based PSAH can be predicted by pulmonary arterial catheterization, PiCCO, heart rate variability, IVCCI, passive leg raise test, or perfusion index.[1213] Of all these IVCCI seem to be more safe, easy, noninvasive, and more economical to predict volume status. However, as there are limited studies on its significance in the prediction of PSAH, this study was conducted in orthopedic cases posted for surgery.

We used subcostal approach to calculate IVCCI before SA and guide the fluid therapy with following objectives. The primary objective was to compare the incidence of PSAH in IVCCI measured and nonmeasured groups. The secondary objective was to determine IVCCI association with PSAH, although preloading was done if IVCCI was more than 40%.

METHODOLOGY

Institutional ethical committee approval was taken (ECR/134/Inst/KA/2013/RR-19), study was conducted between March 2021 and July 2021. After taking written informed consent, 100 patients of American Society of Anesthesiologists (ASA) physical status classes I and II between the age group of 18–60 years posted for the orthopedic lower limb fractured bone surgeries were included in this prospective, randomized cohort study.

The exclusion criteria were patient refusal for consent, body mass index >40 kg.m−2, mean arterial pressure (MAP) <60 mmHg, patients with multiple bone fracture, with expected blood loss more than 500 mL, inferior venacaval (IVC) not visualized, any intra-abdominal tumors, and history of hypersensitivity reactions to the local anesthetic agents.

These 100 patients were randomly subdivided into two groups with 50 patients in each group based on computer-generated randomized list. Allocation concealment was maintained by a person who was not involved with the enrolment.

Group CI: IVCCI was assessed and later followed by SA

Group NCI: SA was given without assessing IVCCI.

Preoperative fasting was advised for at least 6 h before surgery for both solids and liquids. Patients were shifted to the preanesthetic evaluation room. Monitors were attached and pulse rate (PR), basal MAP and arterial oxygen saturation were noted (SPO2). Intravenous (i.v.) line was secured. No fluids were given.

In group CI, preoperative IVCCI was measured in supine position using curvilinear probe of 2–5 MHz through portable USG machine. IVC diameter was measured in spontaneous breathing patients using M-mode modality at subcostal view around 2–3 cms from the right atrium in long axis. IVC maximum diameter measured at maximum end expiration, whereas IVC minimum diameter was measured at end inspiration [Figure 1]. Finally, IVCCI is calculated using the following formula:

Figure 1

Inferior venacaval visualization and inferior venacaval collapsibility index measurement in USG with B-mode and M-mode in the subcostal view

If IVCCI was more than or <40% will be assessed. IVCCI more than 40%, were considered fluid responders and i.v. bolus fluids with 500 mL crystalloid was infused over 15 min. Then, IVCCI measurement was repeated. If still IVCCI was more than 40%, another 500 mL crystalloid was infused. This was repeated till the IVCCI measured was <40%.

After noting IVCCI patients were shifted to the operation theaters. ASA recommended monitors were attached, and the basal readings were taken. Then SA was given.

In group NCI, SA will be given without IVCCI measurement.

The person giving the SA was blinded regarding the IVCCI assessment being done or not, who further checked the spinal level attained and did the hemodynamic monitoring related to our study. SA was given under aseptic precaution, at lumbar L-3 and L-4 level in sitting position, as giving lateral decubitus position would be difficult due to lower limb bone fractures. 12–15 mg bupivacaine heavy and buprenorphine 60 mμ (0.2 mL) was injected with 25 gauge Quincke's spinal needle. After SA, the patient positioned in the supine position. Motor and sensory level assessed. Significant hypotension was considered if fall in systolic blood pressure will be more than 25% or MAP <60 mmHg. Patients were excluded from study if adequate level was not attained after SA [Figure 2].

Figure 2

Consort flow chart

In both the groups, maintenance fluid was started. If hypotension develops, 500 mL bolus crystalloid was given initially and then if still hypotension persists i.v. ephedrine 6 mg bolus given. After two doses of ephedrine, again fluid bolus of 500 mL is rushed and then i.v. ephedrine 6 mg bolus repeated till hypotension is corrected. The hemodynamic variation and total doses of ephedrine received in both the groups were noted and analyzed. The preoperative fluids given in CI group if IVCCI were more than 40% was noted. The total intraoperative fluids which include maintenance and bolus fluids in both the groups, received within first 30 min of surgery were recorded. Total perioperative fluids which include preoperative and intraoperative fluids were also noted. Total intraoperative and perioperative fluids were compared and analyzed among both the groups.

IVCCI measured for the first time in each patients and the statistical significance of its association with PSAH, although preloading was done till IVCCI was <40% as well as IVCCI correlation with total fluids infused both within the group CI were also analyzed.

Sample size calculation: In Ayyanagouda et al.'s study, the incidence of hypotension in IVCCI measured and nonmeasured group was 20% and 50%, respectively.[14] Applying the formula ([p0q0 + p1q1] × [z1−α/2 + z1−β]2/[p1 − p0]2), we derive the sample size of 35 in each group. Considering 10% as drop out, we took total of 100 as sample size with 50 in each group having 95% confidence level and power of 0.8.

Statistical analysis

Statistical analysis was performed using the Statistical Package for Social Sciences (SPSS) software version 18, Chicago, Illinois, USA. Mean ± standard deviation was used for the continuous variables with normal distribution, whereas median or interquartile range was used for nonnormally distributed variables. Numbers or percentage was used for the categorical variables. Unpaired t-test and Z-test analysis was done for continuous data. The data on the nominal scale were compared using the Chi-square test. IVCCI association with hypotension within CI group was analyzed with binary logistic regression analysis and Chi-square test was used to detect statistical significance. IVCCI correlation with total fluids infused within CI group was done with Pearson's correlation. r2 value was analyzed for correlation. P < 0.05 was considered statistically significant with 95% confidence interval.

RESULTS

Our study was of 100 patients with 50 patients in each group of CI and NCI. Both the groups were comparable with respect to demographic characters, surgical parameters, baseline PR, and MAP [Table 1].

Table 1

Patients demographic; surgical and baseline mean arterial pressure, and pulse rate characteristics in group collapsibility index and noncollapsibility index

Parameters	CI (n=50), n (%)	NCI (n=50), n (%)	P
Age, mean±SD	37.86±10.56	37.12±11.19	0.746
Sex
Male	48 (96)	47 (94)	0.646
Female	2 (4)	3 (6)
ASA grade
I	18 (36)	20 (40)	0.680
II	32 (64)	30 (60)
BMI (mean±SD)	24.26±1.84	24.57±1.35	0.348
Type of surgery
Femur	17 (34)	17 (34)	0.950
Tibia	1 (2)	2 (4)
Knee	3 (6)	3 (6)
Ankle/foot	29 (58)	28 (56)
Duration of surgery, mean±SD	89.7±25.78	94.7±19.23	0.274
Blood loss, mean±SD	300±96.36	294±100.83	0.762
Baseline MAP, mean±SD	94.37±11.13	96.92±11.45	0.262
Baseline PR, mean±SD	81.24±13.53	82.93±12.73	0.529

SD=Standard deviation, ASA=American Society of Anesthesiologist, BMI=Body mass index, MAP=Mean arterial pressure, PR=Pulse rate, CI=Collapsibility index, NCI=Non-CI

Overall, the incidence of hypotension was 28%. The incidence of PSAH was 9 (18%) in group CI whereas 19 (38%) in group NCI. The difference in both the groups were statistically significant (P = 0.03). The relative risk reduction of PSAH was 52% in group CI [Table 2].

Table 2

Variation in postpinal anesthesia hypotension, fluids, and vasopressors given in group collapsibility index and noncollapsibility index

Parameters	Group-CI (n=50)	Group-NCI (n=50)	P
Number of patients with PSAH, n (%)	9 (18)	19 (38)	0.03
Preoperative fluids if IVCCI >40% among 26 patients in mL, mean±SD	615±214 (n=26)
Total intraoperative fluids in mL, mean±SD	637±271.95	784±369.97	0.026
Total perioperative fluids in mL, mean±SD	957±478.51	784±369.97	0.046
Total ephidrine doses	16	38	0.003

PSAH=Postspinal anesthesia hypotension, IVCCI=Inferior venacaval collapsibility index, SD=Standard deviation, CI=Collapsibility index, NCI=Non-CI

In CI group, 26 (52%) patients had IVCCI more than 40%. They were preloaded with the crystalloids. Another 24 (48%) patients had IVCCI <40%. Average preoperative fluid in CI group among 26 patients was 615 ± 214 mL. This was not given in NCI group. Difference in the total intraoperative fluids was significantly higher in NCI group compared to CI group, whereas total perioperative fluids were significantly higher in CI group compared to NCI group [Table 2].

Ephedrine doses given are higher in group NCI than CI which is of statistical significance [Table 2].

There was no statistically significant association between IVCCI and hypotension among the patients in the CI group as assessed by binary logistic regression analysis with odds ratio– 1.0074; P = 0.7421 and 95% CL 0.9642–1.0525 [Figure 3].

Figure 3

Binary logistic regression analysis to detect association between inferior venacaval collapsibility index and postspinal anesthesia hypotension

There was weak correlation between the IVCCI assessed and total fluids infused in CI group r2 = 0.4132.

DISCUSSION

Average sensory level was between thoracic segment of 6–9 and average blood loss was <300 ml in both the groups which were minimal and ruled out as a possible cause of PSAH [Table 1].

We have chosen IVCCI more than 40% as cutoff to consider fluid responders. This is based on Zhang et al. systemic review.[15] In their review, the IVCCI cutoff ranged from 12% to 40% across the eight studies involving 235 patients. In overall population, its sensitivity was 0.76 (95% CI: 0.61–0.86) and specificity was 0.86 (95% CI: 0.69–0.95).

In our study, the total incidence of PSAH was 28%, and it was statistically significant more in group NCI with 38% than in group CI with 18% [Table 2]. Ceruti et al. and Ayyanagouda et al. both were the studies to determine if preoperative IVCCI measurement with fluid preloading among high IVCCI could reduce PSAH.[414] In both these studies, the incidence of PSAH was more in non-IVCCI measured group as in our study. In Ceruti et al.'s study, PSAH was 42.5% in IVCCI nonmeasured group and 27.5% in IVCCI measured group.[4] In Ayyanagouda et al.'s study, PSAH was 50% and 20% in IVCCI nonmeasured and measured group, respectively.[14] We have got relative risk reduction pf 52%, whereas Ceruti et al. and Ayyanagouda et al. had a relative risk reduction of PSAH of 35% and 40%, respectively, in IVCCI measured group.[414] The IVCCI cutoff value for considering fluid responders was 36% in the above two studies, whereas we considered 40% which was slightly higher. A number of doses of vasopressors were also higher in IVCCI nonmeasured group in both these studies similar to our study because of higher incidence of PSAH [Table 2].

Salama and Elkashlan et al. also derived that preoperative USG IVCCI measurement predicted PSAH.[12] Here preoperative fluids were not given depending on IVCCI unlike our study, but PSAH and its association with preoperatively measured IVCCI was analyzed. Receiver Operating Curve (ROC) analysis showed area under curve (AUC) as o. 86 with IVCCI cutoff at 44.7% having high sensitivity of 84% and specificity of 77%.

Marcell et al. and Zhang and Critchley both concluded in their studies that preoperative IVCCI can predict postinduction hypotension in general anesthesia.[59] In Zhang and Critchley, the ROC analysis showed AUC of 0.9 and IVCCI cutoff value of 43% had high sensitivity and specificity of 78.6% and 64.8%, respectively.[9] Sazbo Marcell et al. ROC analysis showed AUC 64.8% and IVCCI cutoff of 50% had low sensitivity of 45.5% but very high specificity of 90%.[5] Purushothaman et al. also derived similar result with IVCCI cutoff 43% having high sensitivity of 86.67% and high specificity 94.2%.[16] Most of these studies on general anesthesia show IVCCI of 40% have high sensitivity and specificity to detect fluid responders. In our study, where we chose IVCCI of 40% as cutoff, PSAH was more in IVCCI not measured group compared to IVCCI measured group in whom fluids were preloaded if IVCCI was more than 40%.

Mačiulienė et al. derived different results from our study. They studied if IVCCI can predict PSAH in knee replacement surgery at five points.[17] IVCCI was measured before and immediately after SA, then 15, 30, and 45 min after SA. Their study showed no correlation between PSAH and IVCCI at any point. The absence of PSAH in IVCCI more than 40% could be possibly because patients were allowed to drink water up to 2 h before surgery resulting in adequate fluid balance unlike our study where patients were nil orally for solids and liquids up to 6 h before surgery. Furthermore, in their study, one of the limbs had to be continuously kept flexed during surgery. It might have increased the venous return and decreased PSAH incidence.

Even in Singh et al.'s study, there was no association between IVCCI and PSAH in women posted for cesarean section.[18] This difference in the result might be because of the physiological changes associated with the pregnancy on IVC, and there was maintenance fluids received preoperatively by all the pregnant women in their study. In our study, patients preoperative fluid was given only if IVCCI was greater than 40% otherwise not.

Intraoperative fluids which include maintenance fluids and bolus fluids given if PSAH develops were statistically significantly higher in group NCI compared to group CI as group NCI had higher incidence of PSAH requiring greater volume of fluid to be rushed [Table 2]. Total perioperative fluids include preoperatively preloaded fluids if IVCCI was more than 40% and total intraoperative fluids. This was obviously statistically significantly more in group CI than NCI due to our study protocol as 26 out of 50 patients in group CI had IVCCI more than 40% who were preloaded with fluids before SA [Table 2]. Our study protocol was to some extent similar to Ceruti et al. and Ayyanagouda et al.[414] Total perioperative fluids given were statistically significantly higher in IVCCI measured group in both these studies and the intraoperative fluid was higher in IVCCI non measured group.

In spite of fluid preloaded in group CI, hypotension was noticed. We tried to detect any association of this hypotension with IVCCI detected for the first time through binary logistic regression analysis within group CI only. This was to determine if patients with IVCCI more than 40% measured at first time could have developed higher incidence of PSAH, although fluid preloading was given till IVCCI was < 40%. The analysis showed no statistically significant association. This lack of association might be due to fluid loaded preoperatively decreasing PSAH [Figure 3]. Some other factors might have contributed to PSAH in group CI and possibly not just fluid deficit

There was a weak correlation (r2 = 0.4132) between first measured IVCCI and total fluids infused assessed in group CI only which was similar as in Ceruti et al.'s study.[4] This weak correlation was because of our study design where the total fluid includes not just preoperative bolus when IVCCI exceeds 40% but also intraoperative bolus and maintenance fluids.

Limitations

Our study had some limitations. Patient blinding could not be done as ultrasound was done for patients in CI group and not in NCI group. However, the person giving SA and monitoring hemodynamic was blinded regarding IVCCI measurement. Possibility of interindividual variation in IVCCI measurement was tried to be minimize by taking average of three readings. Some of our orthopedic surgeries at knee or below knee joint used tourniquet. The impact of this tourniquet on IVCCI or PSAH was not done. However, both the groups were comparable with respect to the different surgical sites.

CONCLUSION

Pre SA evaluation of IVCCI to optimize fluid therapy can reduce the incidence of PSAH and the dose of vasopressors needed. It increases the overall perioperative fluids given to the patients posted for orthopedic surgery of lower limb fractured bones. More studies in different kind of surgeries and in elderly patients are needed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.