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ORIGINAL ARTICLE
Year : 2023 | Volume
: 17
| Issue : 2 | Page : 155-162
Supraclavicular block evaluation in oncoorthopedic patients under general anesthesia using perfusion index: A prospective cohort study
Shagun Bhatia Shah1, Jiten Jaipuria2, Mamta Dubey1, Gunjan Vishnoi1, Rajiv Chawla1, Ajay Kumar Bhargava1
1 Department of Anaesthesia and Critical Care, Rajiv Gandhi Cancer Institute and Research Centre, Rohini, Delhi, India
2 Department of Surgical Oncology, Rajiv Gandhi Cancer Institute and Research Centre, Rohini, Delhi, India
Correspondence Address:
Shagun Bhatia Shah
174-175 Ground Floor, Pocket-17, Sector-24, Rohini, Delhi - 110 085
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/sja.sja_620_22
| Date of Submission | 31-Aug-2022 |
| Date of Decision | 07-Sep-2022 |
| Date of Acceptance | 19-Sep-2022 |
| Date of Web Publication | 10-Mar-2023 |
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Background: Supraclavicular brachial plexus blocks (SCBPB) are routinely placed prior to anaesthetic induction for post-operative pain relief after prolonged orthopaedic oncosurgery, since patients are required to remain awake for sensorimotor evaluation of block. If the window period after surgery but before anesthesia-reversal is employed for administering SCBPB, it bestows the quadruple advantage of being painless, not augmenting surgical bleed, longer post-operative analgesia and reduced opioid-related side effects. The problem spot is assessing SCBPB-efficacy under general anesthesia.
Methods: This prospective, single-centric, observational cohort study included 30 patients undergoing upper limb orthopaedic oncosurgery under general anesthesia. Perfusion index (PI) was assessed using two separate units of Radical-7™ finger pulse co-oximetry devices simultaneously in both the upper limbs and PI ratios calculated. Skin temperature was noted.
Results: After successful block, PI values in blocked limb suddenly increased after 5 min, progressively increasing for next 10 min, whereas PI failed to increase further above that attained post anaesthetic-induction in unblocked limb. PI values in the blocked limb were 4.32, 4.49, 4.95, 7.25, 7.71, 7.90, 7.94, 7.89, and 7.93 at 0, 2, 3, 5, 10, and 15 min post block-institution at reversal and 2 min, 5 min post-reversal, respectively. PI ratios at 2, 3, 5, 10, and 15 min post block-administration in the blocked limb, taking PI at local anaesthetic injection as denominator were 1.04, 1.15, 1.67, 1.78, and 1.83, respectively. Correlation between PI and skin temperature in the blocked limb gave a repeated measures correlation coefficient of 0.79.
Conclusion: Monitoring trends in PI and PI-ratio in the blocked limb is a quantitative, non-invasive, inexpensive, simple, effective technique to monitor SCBPB-onset in anaesthetised patients.
Keywords: Anesthesia, brachial plexus block, cancer, orthopaedic surgery, perfusion index
How to cite this article:
Shah SB, Jaipuria J, Dubey M, Vishnoi G, Chawla R, Bhargava AK. Supraclavicular block evaluation in oncoorthopedic patients under general anesthesia using perfusion index: A prospective cohort study. Saudi J Anaesth 2023;17:155-62 |
How to cite this URL:
Shah SB, Jaipuria J, Dubey M, Vishnoi G, Chawla R, Bhargava AK. Supraclavicular block evaluation in oncoorthopedic patients under general anesthesia using perfusion index: A prospective cohort study. Saudi J Anaesth [serial online] 2023 [cited 2023 Mar 30];17:155-62. Available from: https://www.saudija.org/text.asp?2023/17/2/155/371447 |
| Introduction | |  |
Peripheral nerve blocks, including supraclavicular brachial plexus block (SCBPB), produce varying degrees of discomfort when administered to awake patients, notwithstanding any sedation given. When used in conjunction with general anesthesia, SCBPB may be employed even in uncooperative and paediatric patients and gives enhanced post-operative pain relief.[1] Vasodilatation produced due to block-induced sympatholysis may potentially increase surgical bleed in the limb being operated. The duration of analgesia provided by brachial plexus block spans 5–7 h, while an oncosurgery generally lasts 4–5 h. Hence, if the window period after surgery but before reversal of anesthesia is employed for administering SCBPB, it bestows the triple advantage of being painless, not augmenting surgical bleed and providing longer duration of post-operative analgesia for the patient. A fourth advantage is reduced opioid-related side effects due to opioid-sparing effect of nerve blocks given for post-operative pain relief.[1],[2]
Methods of assessing block adequacy include conventional sensory (cold sensation/pin-prick) and motor assessment[3] that is impractical in anaesthetised patients, and advanced techniques like thermographic temperature measurement,[4] laser Doppler perfusion imaging,[5] and skin electrical impedance testing,[6] which are either not commercially available or not a component of the standard OT-milieu. The problem spot is that although SCBPB provides profound analgesia, there are no objective criteria for early assessment of onset of block in patients under general anesthesia. In the present study, non-invasive pulse co-oximetry technology[7] was used to evaluate changes in the perfusion index/pulsatility index (PI) in both blocked and unblocked upper limbs for patients receiving SCBPB for post-operative pain relief after upper limb oncosurgery before reversal of general anesthesia.
We hypothesized that PI can be used as an indicator of successful block placement in patients under general anesthesia where testing of sensory and motor activity is not possible and only rise in skin temperature is available as an indicator of successful block.
Our aim was to ascertain if any correlation exists between PI and the onset of supraclavicular brachial plexus block, if any correlation exists between PI and reversal of general anesthesia, and also PI and skin temperature in the blocked limb, and to find the strength of this correlation.
The primary outcome measure was PI recorded in the blocked and unblocked upper limb at 10 successive time points (T0 = baseline (before induction of anesthesia); T1 = at the time of administration of supraclavicular block (after induction of anesthesia), at T2, T3, T4, T5 and T6 (2, 3, 5, 10, and 15 min post-block, respectively), T7 = at the time of reversal of general anesthesia, and at T8 and T9 (2 and 5 min post reversal). PI-ratio was calculated from PI for each time point. The secondary outcome measures were skin temperature (both arms), at the same time points described above, postoperative Numeric Rating Scale (NRS) score, time to first analgesic requirement, and degree of sensory and motor block.
| Methods | | |
This is a prospective, two-arm, single-centric, observational, cohort study gauging the usefulness of PI in ascertaining the establishment of SCBPB. Thirty ASA I-III patients of either sex, aged 15–80 years, weighing 30–90 kg, undergoing upper limb orthopaedic oncosurgery under general anesthesia were included in this study conducted between May 2017 and October 2019 at a tertiary-care oncology setup. The exclusion criteria comprised patient refusal, local anaesthetic allergy, infection/tumour at SCBPB-site, hand-amputation, arrhythmias and severe peripheral vascular disease. Written informed consent from all patients and ethical clearance (RGCI 491/AN/AKB-05) was obtained from the institutional Ethical Committee. The study was registered prospectively with the Clinical trial registry of India (CTRI/2017/04/008375).
After application of standard monitors including two co-oximeters, one each clipped onto the blocked, and unblocked upper-limb, all patients were pre-medicated with intravenous (IV) glycopyrrolate 4 μg/kg, IV midazolam 0.03 mg/kg, and IV fentanyl 2 μg/kg. Anesthesia was induced with propofol 1–2 mg/kg titrated to loss of response to verbal command and endotracheal intubation was facilitated with peripheral nerve stimulator guided atracurium boluses. After completion of surgery, but before reversal of general anesthesia, an ultrasound guided supraclavicular brachial plexus block for post-operative pain relief was administered to the operated upper limb of the patient. A high frequency linear transducer (8–18 MHz) ultrasound probe (Sonosite, Bothell, Washington) was used for brachial plexus localization and guiding real time delivery of a mixture of 5 ml 2% lignocaine plus 15 ml 0.5% bupivacaine perineurally around the hypoechoic round to oval nerves superficial and lateral to the pulsating subclavian artery. The PI values were assessed using two separate units of Radical-7™ finger pulse co-oximetry devices (Masimo Corp., Irvine, CA, USA)[7] simultaneously in both upper limbs of the orthopaedic patients. PI in unblocked limb (UL) served as control for PI in blocked limb (BL) of the same patient. The heart rate (HR) and mean arterial pressure (MAP) was recorded. Data was evaluated at baseline (pre-induction), on block administration (post-induction of GA) 2, 3, 5, 10, and 15 min after administration of local anaesthetic for brachial plexus block and at 2 and 5 min after reversal of general anesthesia. Conventional parameters of assessing establishment of supraclavicular block include skin temperature, limb sensation, and limb movement, out of which only skin temperature could be used as a comparator agent under general anesthesia for self-evident reasons.
PI is a numerical dimensionless value denoting the ratio of pulsatile (arterial) to non-pulsatile (venous, capillary, tissue) component of blood. Dual wavelengths were used, and PI was calculated from the strength of infrared rays (960 nm) returning from the finger.[8] The finger with the highest PI-value was chosen as the specific monitoring site. Degree of peripheral perfusion was indirectly and non-invasively gauged by PI which ranges from 0.02 (very feeble pulse) to 20% (very strong pulse strength).
PI = (AC/DC) × 100[%][9]
Here, AC is the arterial component or pulsating signal and DC is the non-pulsating signal. Changes in sympathetic nervous system tone as after sympathectomy/brachial plexus block reduces the smooth muscle tone influencing the blood vessel calibre, and hence regional perfusion. After successful peripheral nerve/plexus/neuraxial blockade, local vasodilation resulting from blockade of sympathetic nerve fibres enhances local blood flow/perfusion, raising the PI.
Postoperative numeric rating scale (NRS) score was noted. IV paracetamol 1 g was instituted to all patients 5 min before end of surgery and 12 hourly thereafter for postoperative pain relief. In addition, IV morphine 3 mg was instituted in patients <70 kg and 4.5 mg in patients weighing >70 kg, for NRS score >3 in the postoperative period, followed by another 1.5 mg if pain persisted after 10 min with a capping of 0.1 mg/kg in 6 h. Time to first analgesic dose of morphine (injection of LA till NRS >3) was noted and constituted the end of follow-up. Sensory and motor activity in both the upper limbs was tested 5 min post reversal of anesthesia. Sensory block was evaluated with a blunt needle pin-prick test in the radial, median, ulnar, and musculocutaneous nerve dermatomes (2 = normal sensation, 1 = loss of sensation to pinpricks, and 0 = loss of sensation to light touch).[10] Motor block was evaluated for radial (thumb abduction), median (thumb opposition), ulnar (thumb adduction), and musculocutaneous (elbow flexion) nerves (2 = normal power; 1 = power less than contralateral arm; 0 = no movement against gravity).
Statistical analysis
Continuous variables were expressed as mean ± standard deviation (SD) and the categorical variables as absolute numbers and percentages. Paired sample t-test and the Mann–Whitney U test were utilized for normally distributed and skewed continuous variables, respectively. P value of less than 0.05 was considered statistically significant. Assessing correlation by conventional statistical tests like the Pearson's test assumes independence of error between paired observations. This caveat is breached when repeated measurements are obtained from the same patient. To statistically regulate intra-individual variability, and account for non-independence among paired observations, repeated measures correlation (rmcorr) was utilized to analyse covariance. Rmcorr coefficient (rrm) is tethered at −1 and 1 and represents the strength of linear association between two variables. The closer r is to +1 or −1, the greater shall be the strength of the association. Descriptive statistics were analysed using Medcalc (version 15.8). Repeated measures correlation was analysed and drawn using R-program (v3.6.1).
Data is presented as multiple comparison graphs comprising serial dotted box-whisker plots (dots represent the specific PI values; boxes representing median and interquartile range [IQR]); whiskers show range or extend to 1.5 times the IQR, whichever is smaller).
Sample size was calculated as 28 observation-pairs taking Type-I (Alpha) error as 0.05, Type-II (Beta) error as 0.2, mean difference as 2.2 and SD of differences as 4 from a study by Sebastiani et al.[11] Accommodating dropouts we arrived at a sample size of 30 patients.
| Results | | |
The STOBE-diagram depicts the flow of participants [Figure 1]. The demographic profile included a mean age of 42.8 ± 18.4 years, sex ratio of 17:13 in favour of males, mean body-weight 63.9 ± 13.8 kg and a mean height 162.0 ± 11.1 cm, respectively [Table 1].
Out of the 30 patients studied, 16 had lesions above/at the elbow and 14 had lesions below the elbow. The commonest lesion was a giant cell tumour/osteoclastoma (10 patients) followed by soft tissue sarcoma (6 patients), chondrosarcoma and pathological fracture (3 patients each), squamous cell carcinoma (2 patients) and synovial cell sarcoma, Ewings sarcoma, fibrous histiosarcoma, pigmented villonodular synovitis, infected, impacted peripherally inserted central catheter, finger disarticulation (one patient each).
The baseline PI-values were 3.29 and 3.19 in the blocked and unblocked limbs, respectively (P = 0.03). Nine patients had a higher baseline PI (difference >0.2) in BL, while only one patient had higher baseline PI in UL, while the remaining twenty patients had a baseline PI difference ranging from 0 to 0.1 in the upper limbs. Out of the nine patients, with higher baseline PI in BL, six had below-elbow tumours and three had tumours just above the elbow.
Thereafter, the PI-values recorded in the BL were 4.32, 4.49, 4.95, 7.25, 7.71, 7.90, 7.94, 7.89, and 7.93 at 0, 2, 3, 5, 10 and 15 min post-block-institution and at reversal and 2 and 5 min post reversal of anesthesia, respectively. PI in UL was 4.44, 4.52, 4.45, 4.47, 4.51, 4.52, 4.56, 3.85, and 3.21 at corresponding time points [Table 2]; [Figure 2]. Multiple comparison dotted box-whisker plots with error bars and connecting lines have been plotted to show all data points [Figure 2]. | Figure 2: Multiple comparison dotted Box-whisker plots with error bars and connecting lines for Perfusion Index values in blocked and unblocked limbs (x-axis shows time points − 1, 0, 2, 3, 5, 10, 15, 70, 72, 75 corresponding with T1, T2, T3, T4, T5, T6, T7, T8, and T9 time points described in the manuscript; y-axis shows PI-values; BL = blocked limb; PI = perfusion index; UL = unblocked limb) and trends in perfusion index over time
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PI-ratios post-induction (taking pre-induction baseline as denominator) were 1.31 and 1.39 in BL and UL, respectively. PI-ratios at 2, 3, 5, 10 and 15 min post block-administration in the BL taking PI at the time of LA injection as the denominator were 1.04, 1.15, 1.67, 1.78, and 1.83, respectively [Table 2], whereas the corresponding PI-ratios in the UL were 1.02, 1.00, 1.01, 1.02, and 1.02, respectively. There was no missing data.
In patients with a successful block, PI-values in BL increased within 5 min of block-institution and increased progressively for next 10 min, whereas the values failed to increase further above those attained after induction of anesthesia in UL. After reversal of general anesthesia, the PI decreased in the UL but remained relatively constant in the BL, thus further increasing the difference in PI between the two arms.
Trends in skin temperatures for BL were plotted [Figure 3]. Correlation between PI and skin temperature in BL was calculated to obtain a repeated-measures correlation rmcorr coefficient of 0.79 [Figure 4]. | Figure 3: Trends in skin temperature over time for blocked limb (BL = blocked limb)
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 | Figure 4: Correlation between perfusion index (PI) and skin temperature in the blocked limb
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The baseline HR and mean arterial pressure were 76.06 beats/min and 102.2 mmHg, respectively.
The highest postoperative-NRS was between 0–3 for 28 patients and ranging from 3 to 6 in another two patients. None of the patients had an NRS 7–10 within the first 6 h of transfer to the surgical intensive care unit post-operatively. The same 28 patients neither experienced any touch sensation, nor displayed any movement of the BL, 5 min post-reversal of anesthesia. The remaining two patients retained touch sensation and partial motor activity in BL, suggesting partial effect of SCBPB. The first patient was administered IV morphine 3 mg followed by another 1.5 mg after 10 min, while the second patient was administered IV morphine 4.5 mg (for NRS 4–6). The remaining patients did not require any morphine in the first six postoperative hours. Time to first analgesic (end of follow-up) in the 30-patient cohort was 524 ± 104.8 min (8.73 ± 1.75 h) ranging from 205 to 700 min [Table 1]. Removing the two outliers, it was 9.09 ± 1.13 h.
| Discussion | | |
Changes in heart rate, arterial oxygen saturation, oxygen consumption, and ambient temperature do not have any impact on PI values, the major determinant for PI being the amount of blood present at the monitoring site which depends on local vasoconstriction/vasodilatation.[6]
Adding a vasoconstrictor (epinephrine 5 μg ml−1) to the local anaesthetic used for instituting BPB does not alter PI in the BL (prospective study; Kim et al).[12] Hence, PI is a stable parameter unaffected by numerous intraoperative variables.
Two recent studies have established PI as a novel method of assessing BPB in awake patients by comparing changes in PI with sensory and motor assessment. Sebastiani et al.[11] recorded PI in 25 patients with interscalene BPB, and found the difference between PI in BL and UL increased within 5 min of block-institution and increased progressively for 15 min. They concluded that PI can serve as an indicator of successful block in awake patients. Kus et al.[13] used PI to assess infraclavicular BPB in 44 patients and reported that at 10, 20, and 30 min, PI increased by 120 ± 119%, 133 ± 125%, and 155 ± 144% from baseline, respectively. They concluded that PI is a predictor of infraclavicular block success with largest changes occurring 30 min after BPB institution, although significant changes were detectable at 10 min. We extended the technique to patients under general anesthesia who received SCBPB for post-operative pain relief in orthoncosurgeries and found a sudden spurt in PI in BL at 4–6 min post-block-institution. Since baseline PI is highly variable in most patients, trends in PI are more reliable and so are PI-ratios obtained by keeping the PI at one particular time-point as numerator and baseline-PI as denominator. Hence, we calculated PI-ratios from PI.
SCBPB is instituted in anaesthetized patients either pre-emptively, before surgical incision or alternatively after wound closure. Former, although discomforting for the patient, provides pre-emptive analgesia and reduces intraoperative opioid requirement, but block-induced sympatholytic vasodilatation increases surgical bleed. The latter timing of BPB, is comfortable to all stakeholders: patient (no pain), anaesthesiologist (can perform block freely even in uncooperative patients/difficult anatomy), surgeon (does not contribute to increased surgical bleed when placed after wound closure) besides producing extended postoperative analgesia, reducing postoperative opioid requirement (reduced postoperative nausea-vomiting, constipation and other opioid-associated side-effects), translating into enhanced recovery.
The trendline for PI in the unblocked limb resembled a low-rise plateau. The initial upslope reflecting vasodilatation on administration of anaesthetic induction agents, the length of the flat plateau-top representing the duration of GA, followed by a downslope indicating anesthesia reversal. The trendline for PI in the blocked limb showed a step-ladder pattern: the same initial upslope as the UL, a flat line corresponding with onset of GA to onset of block, followed by a second upslope corresponding with establishment of SCBPB and a second horizontal line (higher than the first) corresponding with continued state of SCBPB [Figure 2].
None of our patients experienced complete block-failure while two of them exhibited a partial effect.
Solutions of levobupivacaine, ropivacaine and bupivacaine provide longer-acting anesthesia (5–7 h), while lignocaine is known to hasten the onset of anesthesia. Hence, we chose a combination of lignocaine and bupivacaine for administering BPB. Real time ultrasound guidance is known to reduce the volume of drug required for a successful block from 30 to 20 ml, besides augmenting the success rate. Hence, despite using a volume of 20 ml, we could establish a successful block in all 30 patients. Time to first analgesic requirement was 524 min which lies between 437 min reported by Gamo et al.[14] for 0.75% ropivacaine +2% lignocaine (1:1) and 11 and 12.2 h reported by Vaghadia et al.[15] for 0.75% ropivacaine and 0.5% bupivacaine respectively, for SCBPB. This is justified by the fact that we used a combination of 0.5% bupivacaine and 2% lignocaine for SCBPB, bupivacaine being longer-acting than both ropivacaine and lignocaine.
Skin temperature readings had a strong correlation with PI values in BL of our patients signified by an rmcorr coefficient of 0.79 between these two parameters. Skin temperature was established as a valuable predictor of correct infraclavicular plexus block placement by Minville et al.[16] which corroborates with our results. Increase in skin temperature is a late phenomenon occurring after loss of sensory and motor functions in patients administered interscalene nerve blocks as reported by Hermann et al.[17] Hence, PI is a quicker and less cumbersome index of successful block placement.
The laser Doppler peripheral flow index (LDPFI) is a reliable parameter to predict successful regional anesthesia after axillary/sciatic blocks but requires specialized equipment.[18]
Albertin et al.[19] studied the influence of sevoflurane (known to increase muscle blood flow and capillary pressure) on blood flow using a LDPFI and found rising PI values with increasing sevoflurane concentrations. This explains our findings of rise in PI in both limbs after anaesthetic induction and sevoflurane administration and a fall in PI only in the UL after reversal of GA (maximal vascular dilatation occurred after SCBPB in BL). Hence, absence of fall in PI in BL after reversal of anesthesia is another indicator of successful BPB.
Two studies have utilized PI for intraoperative identification of successful thoracic sympathectomy.[20],[21] All studies evaluating PI for BPB efficacy have been performed on awake patients so far.[12],[13],[22],[23] The strength of our study is that we have successfully instituted BPB and evaluated its effect in patients under GA for postoperative pain relief in onco-orthopaedic surgery which has not been reported earlier to the best of our knowledge. A limitation is that local anaesthetic injected in the vicinity of the subclavian artery (major blood vessel) will generate some vasodilation reflected as increased PI, regardless of BPB failure. The study is generalizable to all patients undergoing SCBPB under GA.
| Conclusion | | |
The PI increases after successful supraclavicular brachial plexus blockade and trends in PI and PI-ratio may be used as simple, cost-effective and reliable, quantitative indicators of successful block placement in onco-orthopaedic patients under general anesthesia.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]
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