Effect of scalp block on early Hemodynamic responses during Craniotomy under general Anaesthesia
Suzanna Varghese1, Karuna Taksande2, Amol Singam3
1Junior Resident, Department of Anaesthesiology, Jawaharlal Nehru Medical College,
Datta Meghe Institute of Medical Sciences, Sawangi, Wardha, Maharashtra.
2Professor, Department of Anaesthesiology, Jawaharlal Nehru Medical College,
Datta Meghe Institute of Medical Sciences, Sawangi, Wardha, Maharashtra.
3Professor and Head of Department, Department of Anaesthesiology,
Jawaharlal Nehru Medical College, Datta Meghe Institute of Medical Sciences, Sawangi, Wardha, Maharashtra.
*Corresponding Author E-mail: suzanna1003@gmail.com, karunahp1878@gmail.com
ABSTRACT:
Aim: To study the effect scalp block given with 0.5% bupivacaine on early hemodynamic changes in patients who were to undergo craniotomy. Methods: The study was conducted as a randomized experimental prospective Study on 40 adult patients of both sexes till 70yrs of age with an American Society of Anaesthesiologists (ASA) physical status I, II who were to undergo elective craniotomy. After obtaining institutional ethical clearance and written consent of the patients, they were then randomly grouped into 2 using a computer generated table of numbers. Group S, received 20ml 0.9% normal saline, n=20 and Group B received 20ml 0.5% bupivacaine, n=20. Patients were intubated and scalp block was performed 15 minutes prior to craniotomy. The mean arterial pressure (MAP), heart rate (HR) of the patients were recorded prior to and till half an hour post craniotomy. Chi- square test was used to analyse data. Statistical significance was considered if P value was less than 0.05. Result: During the infliction of a painful stimulus, Group S showed a significant difference (p<0.05) in comparison to group Bin terms of the MAP, the HR and also with the baseline within the same group. Conclusion: To conclude, we can say that scalp block ensures the stabilization of hemodynamic responses by reducing the sympathetic response during early craniotomy. We think that Injection Bupivacaine 0.5% can be effectively used for achieving this early haemodynamic stability in scalp block procedures.
KEYWORDS: Scalp block, Craniotomy, Bupivacaine, Regional anaesthesia, Haemodynamic stability.
The need to maintain haemodynamic stability and adequate cerebral perfusion peri-operatively without distortion of the cerebral auto regulatory mechanism during elective neurosurgical procedures is one of the most important concerns for both the anaesthesiologist as well as the surgeon. Anaesthetic agents have an effect on the cerebral metabolism and blood flow, cerebrospinal fluid dynamics, intracranial volume and pressure.(1) The brain parenchyma itself does not perceive any pain due to lack of pain sensitive nociceptors.(2)
However the risk of haemodynamic instability during the early periods of a neurosurgical procedure due to pain responses during skin incision, placement of cranial pins, craniotomy and dural incision are very high despite the use of various anaesthetic techniques.(3) These painful stimuli are direct precipitants of tachycardia and arterial hypertension that lead to potential increase in morbidity due toits association with raised intracranial pressure.(4)
A scalp block involves regional anaesthesia to the nerves that innervate the scalp. These include the following nerves-greater auricular, greater and lesser occipital, supratrochlear supraorbital, zygomatico-temporal and auriculo-temporal. The blunting of noxious stimuli from relevant regions of the scalp could be valuable in reducing the tachycardia and hypertension in both adults and children, thereby providing haemodynamic stability. (8,9,10) After numerous studies since the early 1900s, Bupivacaine became the agent of choice as local anaesthetic for regional anaesthesia owing to its longer action and has been reported to be safe for usage on vascular scalp tissues.(11)
METHODS:
The study was conducted as a prospective randomized clinical study after approval of the ethics and screening committee in the department of Anaesthesiology, Jawaharlal Nehru Medical College and Acharya Vinoba Bhave Rural Hospital (AVBRH), Sawangi (M), Wardha from November 2018 to November 2019. 40 adult patients of both sexes till 70yrs of age with American Society of Anaesthesiologists (ASA) physical status I, II, who were to undergo the procedure of elective craniotomy were included after obtaining their written consent. Those with suspected or proven allergy to bupivacaine, history of severe cardiovascular, pulmonary, hepatic or renal disease, uncontrolled hypertension, past history of previous brain trauma or craniotomy and patients who were chronic alcoholics or chronic drug abusers were excluded from the study.
Pre-operatively, all patients underwent a pre-anaesthetic check-up a day before the procedure. Basic patient details, history and presenting complaints of the illness, general and systemic examination and routine blood and lab investigations were noted. They were asked to maintain a fasting status for a minimum of 8 hours prior to the surgery.
Anaesthesia protocol and monitoring was standardised for all patients. Electrocardiography, pulse oximeter and sphygmomanometer were used for monitoring. The rate of respiration, pulse, capnography, non invasive blood pressure and SpO2 were noted prior to induction. Heart rate, SBP, DBP and MAP were noted and considered as baseline values. An 18G venous cannula was secured and premedicated with Injection Glycopyrollate 0.004mg/kg to dry up secretions, 0.05mg/kg of intravenous Injection Midazolam for sedation and 2mcg/kg intravenous Injection Fentanyl for analgesia. Patients were adequately preoxygenated and then induced with 2-3mg/kg of intravenous Propofol. Tracheal intubation with appropriately sized endotracheal tube was facilitated with 0.1mg/kg of intravenous Injection Vecuronium. Bilateral equal air entry was confirmed, cuff inflated and tube secured in place. Anaesthesia was maintained with propofol infusion at the rate of 6mg/kg/hr, Sevoflurane within the range of 1-2% in 50% O2/50% air and intermittent top up of 0.01mg/kg vecuronium every 15-20 minutes.
Using a computer generated table of random numbers, patients were grouped into two. Group B, the study group consisting of 20 patients received 20ml 0.5% Bupivacaine and Group S, the control group of 20 patients received 20ml of normal saline. Drugs used for scalp block were prepared by an anaesthesiologist not attending the procedure. Scalp block was performed immediately after induction by direct infiltration of the test drug with a 23G needle at 45degree angle with the skin into the 6 sensory nerves each bilaterally, at the typical anatomical places where they emerge from skull. Negative aspiration was done prior to each infilteration to check for unintentional intravascular injection. Skull-pin head holder was placed 5 minutes after the block was done.
MAP value and HR values were measured at the following time intervals: (T0) Prior to anaesthesia induction, (T1, T2)-1 minute and 5 minutes after induction respectively, (T3, T4)- 1 minute and 5 minutes after scalp block respectively, (T5, T6)- 1 minute and 5 minutes after placement of head pins respectively, (T7, T8) 1 minute and 5 minutes after skin incision, (T9, T10) 1 minute and 5 minutes after craniotomy. Changes in heart rate and blood pressure values after painful stimuli (T5-T10) of more than 20% in contrast to baseline values (T0) were considered as hemodynamic instability and inadequate scalp block effectiveness for analgesia during painful stimuli. Hypertension and tachycardia were planned to be treated with 2μg/kg of intravenous fentanyl and by increasing the infusion dose of propofol to 9mg/kg/h. Nitroglycerin bolus of 0.01mg/kg intravenously was planned if SBP and HR were still 20% above the control values. Hypotension was accepted as an SBP value of 20% of the control value and less and 5-10mg of intravenous ephedrine was planned to be administered. Bradycardia was assessed as 20% below the control value or a value less than 40beats/minute and was planned to be treated with 0.5mg of intravenous atropine. Data are presented as average and median values in tables and figures.
STATISTICAL ANALYSIS:
For the statistical analysis of this study SPSS for Windows 21.0 package program, Graph Pad Prism 6.0 version and EPI-INFO 6.0 version were used. Student t test analysed the demographic data. Comparison of haemodynamic variables were applied using student t test, P value, Chi square test. Significant value was considered when values of P were below 0.05.
JUSTIFICATION FOR SAMPLE SIZE –
Assuming a mean heart rate of 80.50bpm with a standard deviation of 14.23 and keeping the power at 80% and confidence interval of 95% (α1 error at 0.05), a minimum of 20% difference is required to evaluate the effect of 0.5% Bupivacaine and a sample size of 15 patients are required in each group. We included 20 patients in each group to compensate for the possible drop outs. The total sample size is of 40 patients.
RESULTS:
All the patients were treated for either an intracranial mass or vascular lesion and underwent craniotomy. Significant differences in age, height, weight, gender and ASA Class could not be seen. The demographic data has been demonstrated in table no.1.
Table 2 shows that the mean heart rate is comparable at baseline values (T0) with non significant results (p=0.54). The HR values after painful stimuli (T5-T10) were significantly higher in group S than values of group B (p<0.05). When the HR at different time intervals was measured intragroup and compared to the baseline value, it was observed that the average HR values were almost the same and did not exceed the 20% change in group B but a significant increase in group S from the time of skull pin placement (T5) onwards was seen.
Table 3 compares the mean arterial pressures. The baseline MAP values of the 2 groups were insignificant (p=0.84). On measuring the intragroup MAP at various time intervals, there was significant difference which existed between the baseline values (T0) and the MAP values after infliction of painful stimuli (T5-T10) in group S while group B remained relatively more stable. On comparing the intergroup MAP values, the saline group (group S) showed a significant rise in MAP as compared to the group receiving Bupivacaine (group B) after painful stimuli. No complications associated with scalp block were noticed in any of the patients.
Table 1: Demographic characteristics of the patients, ASA classification, cause of (n, Avg ± SS).
|
|
Group B(n=20) |
Group C(n=20) |
p Value |
|
Age(years) |
54.78±11.05 |
57.15±10.91 |
0.49* |
|
Weight(kg) |
80.15±11.11 |
78.60±7.94 |
0.61* |
|
Height(cm) |
169.74±8.86 |
168±8.82 |
0.71* |
|
Gender(F/M) (n) |
12/8 |
11/9 |
0.74* |
|
ASA I/II(n) |
9/11 |
7/13 |
0.51* |
|
Cause(Vascular/Lesion) |
8/12 |
13/7 |
0.11* |
*- non significant (p<0.05)
Table 2-Distribution of the heart rate values (beat/min) of the groups according to time (Avg ± SS)
|
HR(Heart Rate) |
Group B(n=20) |
p |
Group S(n=20) |
p |
P |
|
T0-Before Induction |
82.00±11.30 |
|
78.55±10.88 |
|
0.54 |
|
T1-1 min post induction |
83.84±8.60 |
0.56 |
80.33±9.50 |
0.55 |
0.22 |
|
T2-5 min post induction |
82.61±8.20 |
0.84 |
79.54±9.38 |
0.75 |
0.22 |
|
T3-1 min post block |
84.70±7.80 |
0.38 |
82.25±9.11 |
0.25 |
0.36 |
|
T4-5 min post block |
83.55±7.60 |
0.38 |
80.46±8.66 |
0.54 |
0.23 |
|
T5-1 min post head pin placement |
80.12±7.33 |
0.53 |
85.62±8.62 |
0.02µ |
0.03* |
|
T6-5 min post head pin placement |
80.06±6.80 |
0.51 |
84.78±7.89 |
0.04µ |
0.04* |
|
T7-1 min post skin incision |
81.10±7.51 |
0.76 |
87.54±10.11 |
0.01µ |
0.02* |
|
T8-5 min post skin incision |
79.98±8.20 |
0.52 |
86.43±7.80 |
0.01µ |
0.01* |
|
T9-1 min post craniotomy |
79.99±9.60 |
0.54 |
87.19±11.90 |
0.02µ |
0.04* |
|
T10-5 min post craniotomy |
78.96±9.76 |
0.36 |
86.33±8.69 |
0.01µ |
0.01* |
*: p value of <0.05: when compared with Group B, µ: p value of <0.05 in comparison with baseline value
Table 3-Distribution of the MAP (Mean Arterial Pressure mmHg) of the groups according to time (Avg ± SS) (min-max)
|
MAP(Mean Arterial Pressure) |
Group B(n=20) |
p |
Group S(n=20) |
p |
P |
|
T0-Before Induction |
80.00±18.33 |
|
81.12±17.65 |
|
0.84 |
|
T1-1 min post induction |
79.12±18.17 |
0.88 |
80.32±17.41 |
0.88 |
0.83 |
|
T2-5 min post induction |
78.35±17.93 |
0.77 |
79.65±16.98 |
0.78 |
0.81 |
|
T3-1 min post block |
79.46±17.82 |
0.92 |
80.36±16.39 |
0.88 |
0.86 |
|
T4-5 min post block |
77.31±16.46 |
0.63 |
78.54±15.86 |
0.62 |
0.81 |
|
T5-1 min post head pin placement |
78.58±16.13 |
0.79 |
90.11±8.77 |
0.04 µ |
0.007* |
|
T6-5 min post head pin placement |
76.91±15.42 |
0.56 |
90.98±8.42 |
0.03 µ |
0.001* |
|
T71 min post skin incision |
77.35±15.11 |
0.62 |
90.17±8.50 |
0.04 µ |
0.002* |
|
T8-5 min post skin incision |
77.56±18.47 |
0.67 |
90.10±6.7 |
0.04 µ |
0.006* |
|
T9-1 min post craniotomy |
78.87±12.31 |
0.82 |
92.98±18.47 |
0.04 µ |
0.007* |
|
T10-5 min post craniotomy |
77.93±11.96 |
0.67 |
92.60±17.4 |
0.04 µ |
0.003* |
*: p value of <0.05 : when compared with Group B, µ: p value of <0.05 in comparison with baseline values
DISCUSSION:
An optimal neuro-anaesthesia technique aims at preventing the acute change in haemodynaimcs following noxious stimuli. Even after achieving sufficient depth of anaesthesia the application of skull pins, skin incision, periosteal and dural interventions may lead to an acute hypertensive response,(12,13) owing to the sympathetic response system that is activated by the efferent pain sensations generated from the skin and periosteum. The resulting tachycardia and hypertension lead to an eventual rise in intracranial pressure which is directly associated with a potential increase in morbidity. (4) This rise in ICP may be deleterious in patients with already raised ICP or cerebral aneurysms and a further increase imposes a risk for herniation, pulmonary oedema or the rupture of a cerebral aneurysm.(14,15) The brain tissue itself is not sensitive to pain as they do not possess any nociceptors owing to their embryonal development where the cells responsible for brain tissue formation and that of nociceptors are of different origins.(2) Therefore in our study we considered the haemodynamic changes owing to noxious stimuli only until dural intervention.
Various studies in the past have been conducted to find a solution to help overcome the issue of haemodynamic instability. The application of systemic opioids was one solution that could help blunt these stress responses, but its drawback lay in the fact that its high doses could adversely lower the blood pressure and cause delayed emergence from anaesthesia.(16) Over time, studies established the effectiveness of the use of regional anaesthesia to supplement general anaesthesia to offer advantages such as lower stress response and better haemodynamic stability.(17) This eventually led to the concept of blocking the nerves of the scalp, an age old technique, introduced over a century ago. The idea was explored in the past as an attempt to maintain haemodynamic stability during intraoperative period(18) especially in patients with brain injury in whom the effect of general anaesthesia was deleterious. The use of scalp block hasbeen studied earlier and has been increasingly used to attenuate the stress responses to pinning and incision in neuro surgery.(3) One major advantage of it is that the scalp is innervated by most nerves that are superficial terminal sensory branches and thereby the risk of damage to deeper motor nerves are lowered.
Girvin et al(19) originally described the technique of scalp block in 1986 for use in awake craniotomies to achieve haemodynamic stability which was later popularised in 1992 when Rubial et al(20) in their study suggested that the direct blockade of the occipital and frontal nerves was a useful method to maintain the hemodynamic stability during skull pin placement in neurosurgical cases. The one major drawback of this study was that it did not have a control group. Pinosky et al(9) in 1996 overcame this drawback by comparing the effect of ‘‘skull block’’ with normal saline to 0.5% Bupivacaine on the autonomic responses to painful stimuli and anaesthetic need. They demonstrated that scalp block was effective in controlling the haemodynamic responses to painful stimuli and lesser need for volatile anaesthetics. We followed the exact same description as Pinosky et al. in our study and blocked the same nerves and also included a control group who received 20ml of normal saline instead and obtained similar results. We found a significant difference in the haemodynamics of study group B and the control group S at the time of pin insertion, incision as well as craniotomy. The study group who received scalp block with 0.5% Bupivacaine showed no significant rise in MAP or heart rate after painful stimuli attributing to the successful blockade of the sympathetic response system. There was also no significant difference noted in the values within the study group B as compared to the baseline values, corroborating its relative haemodynamic stability.
The local infiltration of scalp with a local anaesthetic was initially used to curb the haemodynamic instability. However a major step in regional anaesthesia occurred with the transition from local scalp infiltration to blocking the nerves of the scalp. Geze et al.(21) carried out a prospective, randomized, placebo-controlled study to compare the effectiveness of scalp block and local infiltration, both with 0.5% bupivacaine on the stress responses (metabolic and endocrine) and hemodynamics (mean arterial pressure, heart rate) in craniotomy cases. The study reported that patients receiving scalp block showed decreased rise and variation in haemodynamic response with no requirement of an additional antihypertensive or anaesthetic agent, while local wound infiltration could only provide short lived analgesia around the wound area. In our study the effect of supplementing general anaesthesia with regional scalp block obtained well-matched results with that of Geze et al and we observed excellent haemodynamic stability and significant perioperative tachycardia and hypertension in patients included in the normal saline group (control group) as compared to the baseline values whenever a noxious stimulus was inflicted.
Various local anaesthetics such as Bupivacaine, Ropivacaine, Lidocaine with or without the combination of adrenaline could be used for scalp block. Schaffrainietz et al. (22) in their study reported no significant difference in the potency of either long acting bupivacaine or short acting lidocaine in preventing the haemodynamic response to the placement of Mayfield skull pin head holder. Hillman et al reported successful hemodynamic attenuation with 0.5% Bupivacaine without addition of a vasoconstrictor.(8) In Our study we administered 0.5% Bupivacaine slowly without the addition of a vasoconstrictor to avoid its unintentional intravascular injection, drug toxicity and subsequent adverse effects owing to large volumes of the drug used for the block.
Our results were found to be consistent with the results of other studies with no complications noted associated with the block. However the potential limitations of the study are firstly, the small sample size with only descriptive comparison of the results which should be confirmed on a larger group of patients with proper statistical analysis. Secondly the biological differences in perception of pain among patients could alter the measured values and hence future studies may have to consider the preoperative evaluation of pain potency sensation. Thirdly the incidences of complications may go under-recognized in such a small group of patients.
CONCLUSION:
To conclude, we can say that scalp block with 0.5% Bupivacaine when used in combination with general anaesthesia in neurosurgical cases provides haemodynamic stability in the early surgical period by decreasing the sympathetic responses intraoperatively. Therefore the technique should be considered in all neurosurgical cases to maintain a steady early haemodynamic state, reduce morbidity and to obtain better analgesic results.
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Received on 18.02.2020 Modified on 21.03.2020
Accepted on 19.04.2020 © RJPT All right reserved
Research J. Pharm. and Tech. 2020; 13(9):4409-4414.
DOI: 10.5958/0974-360X.2020.00780.5