Intraoperative administration of systemic/epidural/intrathecal morphine on the quality of recovery following substitutional urethroplasty with buccal mucosal graft: A randomized control trial.

Background and Aims: Substitutional urethroplasty with buccal mucosal grafting for urethral stricture is associated with significant pain, and thus inappropriate perioperative pain management could delay postoperative recovery. The objective of our research was to determine the effects of analgesia with systemic or epidural or intrathecal morphine on quality of recovery (QoR) in patients undergoing substitutional urethroplasty with buccal mucosal grafting. Material and Methods: This prospective, double-blinded, randomized control trial was conducted over 2 years in ASA I and II patients who underwent substitutional urethroplasty with buccal mucosal graft. Patients were randomized into three groups, and Group A received systemic morphine (0.1 mg/kg), Group B received epidural morphine (3 mg), and Group C received intrathecal morphine (150 µg). The QoR between the groups were compared postoperatively using the 40-item QoR questionnaire, and the hemodynamic variations, time taken for ambulation, resumption of oral intake, and incidence of complications were also compared. Results: Out of the recruited 93 patients, 88 patients were analyzed. The QoR score for each domain was comparable between the three groups. The total QoR score for systemic, epidural, and intrathecal morphine groups were 189 (185-191), 189 (187-191), and 185 (183-189), respectively. Additionally, the hemodynamic variations, time taken for ambulation, and resumption of oral intake were comparable between all three groups except the incidence of postoperative nausea and vomiting (PONV) and pruritis, which were higher in the intrathecal group. Conclusion: All three modalities, namely systemic morphine (0.1 mg/kg), epidural morphine (3 mg), and intrathecal morphine (150 µg), offer similar QoR after substitutional urethroplasty. However, the incidence of PONV and pruritis was higher with the administration of intrathecal morphine.

An Unusual Cause of Chronic Headache in an Adolescent Boy: A Case Report.

Spontaneous intracranial hypotension (SIH) is an under-diagnosed cause of headache in children and adolescents. SIH results from cerebrospinal fluid (CSF) leak due to breach in the dura mater and the etiology for dural breach is often diverse. We report an adolescent boy who presented with chronic episodic headache that later progressed to daily headache. There was a typical history of worsening of headache on upright position and relief of headache on lying down. He was treated with migraine prophylaxis in another hospital but there was no response. Marfanoid features and brisk deep tendon reflexes were observed on clinical examination. Brain magnetic resonance imaging (MRI) revealed sagging of the brain stem, pachymeningeal enhancement, and tonsillar herniation. MRI of spine myelogram confirmed multiple levels of CSF leak. He was initially managed with supportive measures and fluoroscopic-guided fibrin glue injection. Although child remained symptom-free for the next 6 months, he again developed headache. MRI and computed tomography spine myelogram revealed a meningeal diverticulum in the lumbar spine. He was managed with an autologous epidural blood patch and he has been well since then. In this report, we highlight the clinical and radiological pointers to the presence of SIH in children with recurrent headache.

Effect of superficial cervical plexus block on postoperative quality of recovery after anterior cervical discectomy and fusion: a randomized controlled trial.

PURPOSE: Spine surgeries are increasingly being performed as a day or short-stay surgery programs. Peripheral nerve block provide site-specific pain relief with few side effects, thereby reducing surgical stress and enhancing quality of recovery. The aim of our study was to determine the effect of a superficial cervical plexus block (SCPB) on postoperative quality of recovery and analgesia in patients undergoing elective anterior cervical discectomy and fusion (ACDF). METHODS: After Research Ethics Board approval, we enrolled adults (> 18 yr) scheduled for elective single- or two-level ACDF in this randomized double-blind clinical trial. Participants were randomized to receive either a SCPB (0.25% bupivacaine, 10 mL) or No Block. The primary outcome measure was the quality of recovery at 24 hr, measured using the 40-item quality of recovery questionnaire (QoR-40). In addition, comparisons between groups were also made for postoperative opioid consumption and discharge times. RESULTS: Forty-six patients were randomized to receive either a SCPB block (n = 23) or No Block (n = 23). Median [interquartile range] aggregated global QoR-40 scores at 24 hr were significantly greater in the SCPB group, indicating good quality of recovery compared with the No Block group (179 [116-195] vs 157 [97-196], respectively; median difference, 22; 95% confidence interval [CI], 7 to 34; P = 0.002]. There were no differences between the SCPB and the No Block group with regard to mean (standard deviation) postoperative opioid consumption at 24 hr [22.9 (13.6) mg vs 24.6 (9.5) mg, respectively; mean difference 1.7; 95% CI, -5.2 to 8.7; P = 0.620] and the number of patients discharged within 24 hr (15 vs 12, respectively; P = 0.550). CONCLUSION: We showed that preoperative SCPB is an effective strategy for improving the early quality of recovery in patients undergoing single- or two-level ACDF. Nevertheless, there was no impact on opioid consumption or discharge times. This trial was registered at www.clinicaltrials.gov (NCT01662219).

Comparison of propofol and volatile agents for maintenance of anesthesia during elective craniotomy procedures: systematic review and meta-analysis.

BACKGROUND: Both propofol and volatile anesthetics are commonly used for maintenance of anesthesia in patients undergoing neurosurgical procedures. The effects of these two classes of drugs on cerebral hemodynamics have been compared in many clinical trials The objectives of this review were to evaluate the cerebral hemodynamic effects, operative conditions, recovery profiles, postoperative complications, and neurological outcomes of propofol-based vs volatile-based anesthesia for craniotomy. METHODS: MEDLINE®, EMBASE™, Cochrane, and other relevant databases were searched for randomized controlled trials that compared propofol-maintained anesthesia with volatile-maintained anesthesia in adult patients undergoing elective craniotomy. The primary outcome measure was the intraoperative brain relaxation score. Secondary outcome measures included intraoperative cerebral hemodynamics (intracranial pressure [ICP], cerebral perfusion pressure [CPP]), cardiovascular changes, recovery profiles, postoperative complications, and clinical outcomes (neurological morbidity, mortality, quality of life). A meta-analysis was conducted using a random effects model to compare the outcomes of the two anesthetic techniques. RESULTS: Fourteen studies (1,819 patients) met inclusion criteria and were analyzed. Brain relaxation scores were similar between the two groups after dural opening; however, ICP was lower (weighted mean difference of -5.2 mmHg; 95% confidence interval -6.81 to -3.6) and CPP was higher (weighted mean difference of 16.3 mmHg; 95% confidence interval 12.2 to 20.46) in patients receiving propofol-maintained anesthesia. Postoperative complications and recovery profiles were similar between the two groups, except for postoperative nausea and vomiting being less frequent with propofol-maintained anesthesia. There were inadequate data to perform a meta-analysis on clinical outcome. CONCLUSION: Propofol-maintained and volatile-maintained anesthesia were associated with similar brain relaxation scores, although mean ICP values were lower and CPP values higher with propofol-maintained anesthesia. There are inadequate data to compare clinically significant outcomes such as neurological morbidity or mortality.

Entropy as an indicator of cerebral perfusion in patients with increased intracranial pressure.

Changes in electroencephalogram (EEG) patterns correlate well with changes in cerebral perfusion pressure (CPP) and hence entropy and bispectral index values may also correlate with CPP. To highlight the potential application of entropy, an EEG-based anesthetic depth monitor, on indicating cerebral perfusion in patients with increased intracranial pressure (ICP), we report two cases of emergency neurosurgical procedure in patients with raised ICP where anesthesia was titrated to entropy values and the entropy values suddenly increased after cranial decompression, reflecting the increase in CPP. Maintaining systemic blood pressure in order to maintain the CPP is the anesthetic goal while managing patients with raised ICP. EEG-based anesthetic depth monitors may hold valuable information on guiding anesthetic management in patients with decreased CPP for better neurological outcome.

Perioperative management and complications in patients with obstructive sleep apnea undergoing transsphenoidal surgery: Our institutional experience.

BACKGROUND AND AIMS: Patients with endocrine diseases such as acromegaly and Cushing's disease have a high prevalence of obstructive sleep apnea (OSA). There is controversy regarding the use of continuous positive airway pressure (CPAP) following transsphenoidal surgery. The aim of this study was to compare the perioperative management and complications, in patients with or without OSA undergoing transsphenoidal surgery. MATERIALS AND METHODS: After Research Ethics Board approval, we retrospectively reviewed the charts of all patients who underwent transsphenoidal surgery in our institution from 2006 to 2011. Information collected included patients' demographics, pathology of lesion, history of OSA, anesthetic and perioperative management and incidence of perioperative complications. Patients with sleep study proven OSA were compared with a control group, matched for age, sex and pathology of patients without OSA. Statistical analysis was performed using t-test and Chi-square test and the P < 0.05 was considered to be significant. RESULTS: Out of a total 469 patients undergoing transsphenoidal surgery, 105 patients were found to be at risk for OSA by a positive STOP-BANG scoring assessment. Preoperative sleep study testing was positive for OSA in 38 patients. Post-operative hypoxemia (SpO2 < 90) occurred in 10 (26%) patients with OSA and was treated with high-flow oxygen through face mask (n = 7) and by CPAP mask (n = 3). In the OSA-negative group, 2 patients had hypoxemia and were treated with low-flow oxygen using face mask. There were no differences between the groups with respect to post-operative opioid use, destination, hospital stay or other complications. CONCLUSIONS: Post-operative hypoxemia in patients with OSA following transsphenoidal surgery can be treated in most but not all patients with high flow oxygen using the face mask. We were able to safely use CPAP in a very small number of patients but caution is needed to prevent complications. Further prospective studies are needed to determine the safe use of CPAP in patients after transsphenoidal surgery.

Challenges of anaesthetising a child with Bow Hunter's syndrome and dilated cardiomyopathy for occipitocervical fusion.

Paediatric Bow Hunter's syndrome (BHS), or rotational vertebral artery syndrome, is a rare cause of posterior circulation insufficiency in children. It results from mechanical obstruction of the vertebral artery by the transverse process of cervical vertebrae resulting in vertebrobasilar insufficiency during the neck rotation to the sides. Paediatric dilated cardiomyopathy (DCM) is a rare myocardial disease that presents with ventricular dilatation and cardiac dysfunction. This case report describes the successful anaesthetic management of an boy with BHS due to atlantoaxial dislocation and DCM. The child was anaesthetised by keeping the following anaesthetic goals in mind such as maintenance of the heart rate, rhythm, preload, afterload and contractility close to the baseline for both DCM and BHS. Haemodynamic management with optimal fluids, inotrope and a vasopressor and titrating its volume and doses using multimodal haemodynamic monitoring while keeping both cardio and neuroprotective strategies, and the multimodal analgesia techniques helped the child for faster recovery.

Recent advancements in the practice of neuroanaesthesia and neurocritical care: An update.

The practice of neuroanaesthesia has expanded significantly in recent years to keep up with various challenges posed in the perioperative care of patients for neurosurgical, interventional, neuroradiological, and diagnostic procedures. Technological advancements in neuroscience include the intraoperative use of computed tomography scans and angiograms for vascular neurosurgery, magnetic resonance imaging, neuronavigation, expansion of minimally invasive neurosurgery, neuroendoscopy, stereotaxy, radiosurgery, the performance of increasingly complex procedures, advancements in neurocritical care, etc. Recent advancements in neuroanaesthesia that can meet these challenges include the resurgence of ketamine, opioid-free anaesthesia, total intravenous anaesthesia, techniques to facilitate intraoperative neuromonitoring, awake neurosurgical and spine surgeries, etc. The current review provides an update on the recent advancements in neuroanaesthesia and neurocritical care.

Comparing two techniques of performing an epidural catheter-assisted epidural blood patch using a 20 ml syringe versus a 5 ml syringe and its effect on clotting time, the strength of clot retraction and haemolysis - A prospective in vitro study (EC-EBP study).

Background and Aims: Epidural blood patch (EBP) is performed by injecting autologous blood into the epidural space using a Tuohy needle. Certain clinical scenarios mandate an epidural catheter (EC)-assisted EBP. Collecting blood in a 20-ml versus 5-ml syringe appears to influence the quality of the clot. This in vitro study compared the techniques of performing the EC-assisted EBP using 20-ml versus 5-ml syringe on clotting time (CT), clot retraction (CR) and haemolysis. Methods: This in vitro study was performed in a haematology laboratory. Five consented adult healthy male volunteers donated blood. In the 5-ml syringe technique, blood was injected through an EC, and as it flowed out of the tip, it was collected at the beginning and the end of 1 min. With the 20-ml technique, blood was collected at the beginning and end of the first, second and third minute. The samples were tested for CT, CR and haemolysis by measuring the plasma-free haemoglobin (PFHb). Results: Five injections were made using a 5-ml syringe, and another five with a 20-ml syringe. Injection time was shorter in the 5-ml technique (80.80 ± 5.89 vs. 272 ± 28.4 s, P < 0.0001). With the 20-ml technique, CT progressively increased (>15 min), whereas, with the 5-ml syringe, the CT was normal. Both techniques caused mild, insignificant haemolysis (PFHb >0.005 g/dl), without affecting the quality of CR. Conclusion: EC-assisted EBP using a 5-ml syringe technique shortens the injection time and deposits fresh blood quickly without affecting CT and CR.

The Utility of COMPASS-31 Questionnaire to Predict Autonomic Dysfunction in Patients With Cervical/Upper Thoracic Compressive Myelopathy.

BACKGROUND: Patients with cervical/upper thoracic compressive myelopathy may have autonomic dysfunction. The composite autonomic severity score (CASS) is the gold standard test to detect autonomic dysfunction, and the self-rated composite autonomic system scale (COMPASS-31) questionnaire is a screening tool to diagnose autonomic dysfunction. This study compared the COMPASS-31 and modified CASS scores for the detection of autonomic dysfunction in patients with compressive myelopathy. METHODS: Patients with cervical/upper thoracic compressive myelopathy scheduled for decompressive surgery completed a COMPASS-31 questionnaire and underwent autonomic function tests to calculate the modified CASS score before surgery. RESULTS: Forty-two patients were included in the study; 19 (45.2%) had mild autonomic dysfunction, 5 (11.9%) had moderate autonomic dysfunction, and 18 (42.9%) had severe autonomic dysfunction. Median (interquartile range) of modified CASS and COMPASS-31 scores were 19 (6.33) and 3 (2.5), respectively. There was a positive correlation between modified CASS and COMPASS-31 scores ( r =0.43; P =0.004). Receiver operating characteristic curve analysis confirmed that COMPASS-31 had fair accuracy for prediction of moderate to severe autonomic dysfunction (area under the curve, 0.74; 95% confidence interval, 0.64-0.82; P =0.009). A cut-off of 30 for total COMPASS-31 score had a sensitivity of 52.2% and specificity of 89.5% to detect moderate to severe autonomic dysfunction, with positive and negative predictive values of 85.7% and 60.7%, respectively. CONCLUSION: Patients with cervical/upper thoracic compressive myelopathy had varying degrees of autonomic dysfunction based on the modified CASS. There was a positive correlation between the modified CASS and COMPASS-31 questionnaire. A COMPASS-31 score of >30 30 could be utilized to predict moderate to severe autonomic dysfunction in patients with compressive myelopathy.

Adding Ketamine to Epidural Morphine Does Not Prolong Postoperative Analgesia After Lumbar Laminectomy or Discectomy.

BACKGROUND: Epidural opioids provide effective postoperative analgesia after lumbar spine surgery. Ketamine has been shown to reduce opioid-induced central sensitization and hyperalgesia. We hypothesized that adding ketamine to epidural opioids would prolong the duration of analgesia and enhance analgesic efficacy after lumbar spine surgery. METHODS: American Society of Anesthesiologists physical status class I to II patients aged between 18 and 70 years with normal renal function undergoing lumbar laminectomy were recruited into this single-center randomized trial. Patients were randomized to receive either single-dose epidural morphine (group A) or epidural morphine and ketamine (group B) for postoperative analgesia. The primary objective was to compare the duration of analgesia as measured by time to the first postoperative analgesic request. Secondary objectives were the comparison of pain scores at rest and movement, systemic hemodynamics, and the incidence of side effects during the first 24 hours after surgery. RESULTS: Fifty patients were recruited (25 in each group), of which data from 48 were available for analysis. The mean±SD duration of analgesia was 20±6 and 23±3 hours in group A and group B, respectively (P=0.07). There were 12/24 (50%) patients in group A and 17/24 (71%) patients in group B who did not receive rescue analgesia during the first 24-hour postoperative period (P=0.07). Pain scores at rest and movement, systemic hemodynamics, and postoperative complications were comparable between the groups. CONCLUSIONS: The addition of ketamine to epidural morphine did not prolong the duration of analgesia after lumbar laminectomy.

The effect of continuing versus withholding angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers on mortality and major adverse cardiovascular events in hypertensive patients undergoing elective non-cardiac surgery: study protocol for a multi-centric open-label randomised controlled trial.

BACKGROUND: Angiotensin-converting enzyme inhibitors (ACEIs)/angiotensin receptor blockers (ARBs) are commonly prescribed to patients with hypertension. These drugs are cardioprotective in addition to their blood pressure-lowering effects. However, it is debatable whether hypertensive patients who present for non-cardiac surgery should continue or discontinue these drugs preoperatively. Continuing the drugs entails the risk of perioperative refractory hypotension and/or angioneurotic oedema, while discontinuing the drugs entails the risk of rebound hypertension and myocardial ischaemia. The aim of this study is to evaluate the effect of continuation vs withholding of ACEIs/ARBs on mortality and other major outcomes in hypertensive patients undergoing elective non-cardiac surgery. METHODS: The continuing vs withholding of ACEIs/ARBs in patients undergoing non-cardiac surgery is a prospective, multi-centric, open-label randomised controlled trial. Two thousand one hundred hypertensive patients receiving ACEIs/ARBs and planned for elective non-cardiac surgery will be enrolled. They will be randomised to either continue the ACEIs/ARBs including on the day of surgery (group A) or to withhold it 24-36 h before surgery (group B). The primary endpoint will be the difference in the composite outcome of all-cause in-hospital/30-day mortality and major adverse cardiovascular and non-cardiovascular events. Secondary endpoints will be to evaluate the differences in perioperative hypotension, angioneurotic oedema, myocardial injury, ICU and hospital stay. The impact of the continuation vs withholding of the ACEIs/ARBs on the incidence of case cancellation will also be studied. DISCUSSION: The results of this trial should provide sufficient evidence on whether to continue or withhold ACEIs/ARBs before major non-cardiac surgery. TRIAL REGISTRATION: Clinical Trials Registry of India CTRI/2021/01/030199. Registered on 4 January 2021.

Lumbar Erector Spinae Plane Block for Posterior-Superior Iliac Spine Bone Graft Site Pain in Patients Undergoing Occipitocervical and C1-C2 Fusion for Atlantoaxial Dislocation/Odontoid Fracture-A Case Series.

Pain at the autologous bone graft site from the posterior-superior iliac spine (PSIS) is severe enough to affect the postoperative ambulation. It adds to the morbidity of the surgical procedure. Inadequate pain management at the graft site not only affects the postoperative recovery but also can lead to chronic pain. We report the use of ultrasound (US)-guided lumbar erector spinae plane block (ESPB), to deliver effective analgesia for this pain. Patients who underwent occipitocervical fusion (OCF) and C1-C2 fusion using PSIS for atlantoaxial dislocation (AAD)/odontoid fracture from January to March 2020 and who received US-guided lumbar ESPB were retrospectively studied. All the necessary data were collected from the inpatient hospital, anesthesia, and the acute pain service records. A total of six patients received lumbar ESPB, of which one received a single shot injection, and the rest five had a catheter placement for postoperative analgesia. The average volume of intraoperative and postoperative bolus was 27(range: 15-30) and 21 (range: 15-30) mL of 0.2% ropivacaine, respectively. All patients achieved a unilateral sensory blockade ranging from L1 to L3 dermatomes. None of our patients had a numerical rating scale of > 4 on movement at any time point during the first 48 hours except in one, in whom only a single shot bolus was given. No complications related to ESPB were noted. All were ambulated on the second postoperative day except one. The average length of hospital stay was 6 (range: 4-10) days. US-guided lumbar ESPB provides excellent analgesia for PSIS bone graft site pain and promotes early ambulation.

An observational case-control study comparing the recovery profile in patients receiving additional dose of anticonvulsant vs. regular dose during supratentorial craniotomy.

BACKGROUND AND AIMS: Anticonvulsants are used routinely for seizure prophylaxis in patients with supratentorial tumour who present with/without seizures. Excessive use of prophylactic anticonvulsant may delay the recovery from anaesthesia. We have studied the recovery profiles of patients who received an additional dose of anticonvulsant in comparison with those who received only the regular dose. METHODS: In this prospective observational study, patients were anaesthetised using standard anaesthesia protocol. An additional dose of anticonvulsant was administered in one group, while the other group received only the regular dose. Time taken for extubation, eye opening, obeying commands and orientation were compared between the two groups. Haemodynamics, depth of anaesthesia, the plasma anticonvulsant levels and the incidence of seizures were compared between the two groups. RESULTS: A total of 36 patients were studied, of which 19 received regular dose and 17 received an additional dose. There was no significant difference in recovery time between the two groups. Subgroup analysis was performed for phenytoin and sodium valproate. There was a clinically significant delay in recovery in patients who received an additional phenytoin compared to those who received regular dose (time to obey commands >15 min and orientation time >1hour) but, it was not statistically significant. Administration of an additional dose of valproate did not prolong the recovery time. CONCLUSION: An additional dose of sodium valproate did not cause a delay in recovery both, clinically and statistically. However, the administration of an additional dose of phenytoin caused a clinically significant delay in recovery but was not statistically significant.

Measurement of non-invasive blood pressure in lateral decubitus position under general anaesthesia - Which arm gives more accurate BP in relation to invasive BP - dependent or non-dependent arm?

BACKGROUND AND AIMS: Non-invasive blood pressure (NiBP) varies with the arm and body position. In the lateral decubitus position (LDP), the non-dependent arm reads lower, and the dependent arm reads higher pressure. We aimed to study the correlation between the NiBP and invasive arterial blood pressure (ABP) as anaesthesia progressed and its correlation in different BP ranges. METHODS: American Society of Anesthesiologists (ASA I-III) patients, between 18-70 years undergoing neurosurgical procedures in the LDP were studied. All were anaesthetised using a standard protocol, positioned in the LDP. NiBP was measured every 15 min in both dependent and non-dependent arms and correlated with the ABP. RESULTS: Intra-class correlation (ICC) done between the dependent arm NiBP and ABP showed good correlation for mean and systolic BP and moderate correlation for diastolic BP. ICC was 0.800, 0.846 and 0.818 for mean and 0.771, 0.782, 0.792 for systolic BP at 15 min, 1 h, and 2 h, respectively. The ICC between the non-dependent arm NiBP and the invasive ABP showed poor correlation for all BP (systolic, diastolic and mean). As anaesthesia progressed, the mean difference between the NiBP and the ABP decreased in the dependent arm and increased in the non-dependent arm. The strength of agreement between the NiBP and the ABP in various BP ranges showed moderate correlation for the dependent arm NiBP (0.45-0.54) and poor correlation (0.21-0.38) for the non-dependent arm. CONCLUSION: The NiBP of the dependent arm correlated well with ABP in LDP under general anaesthesia (GA). It is better to defer measuring NiBP in the non-dependent arm as the correlation with ABP is poor.

Anesthetic challenges of a patient with the communicating bulla coming for nonthoracic surgery.

Management of a patient with a giant bulla coming for a nonthoracic surgery is rare, and its anesthetic management is very challenging. It is imperative to isolate only the subsegmental bronchus, in which the bulla communicates to avoid respiratory morbidities such as pneumothorax, emphysema or atelectasis of the surrounding lung parenchyma, and postoperative respiratory failure. Herewith, we want to report the anesthetic challenges of a patient with giant bulla communicating into one of the subsegmental right upper lobe bronchus for splenectomy.

Cerebrovascular reactivity to carbon dioxide under anesthesia: a qualitative systematic review.

INTRODUCTION: Controlling the arterial carbon dioxide tension (PaCO2) to reduce the cerebral blood flow (CBF) and the intracranial pressure is a common practice in neuroanesthesia. A change in CBF in response to change in PaCO2 is termed as cerebrovascular reactivity to carbon dioxide (CVR-CO2). Studies have shown that, both inhalational and intravenous anesthetic agents have variable effects on CVR-CO2 and the effect of anesthetic agents on CVR also varies with many physiological and pathologic conditions. The objectives of this review were to evaluate the effect of anesthetic agents on the CVR-CO2 in adults and to determine how this response is modified by other physiological and pathologic factors. METHODS: We conducted a systematic search of the databases of Medline, Embase, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews using related term components for both CVR-CO2 and anesthesia. Our primary outcome of this review was to determine whether the CVR-CO2 is maintained under anesthesia. The other endpoints of this review are to determine the effect of other factors (age, sex, medical comorbidities, and cerebrovascular pathology) on the CVR-CO2 under anesthesia. Because of the methodological heterogeneity in the primary studies, quantitative analysis of the data was not possible, and therefore, we have summarized the data qualitatively. RESULTS: Our search strategy yielded 1356 citations. After excluding nonpertinent papers, 38 studies were included for the systematic review. Nineteen randomized controlled trials and 19 observational studies met inclusion criteria and a total of 793 patients were studied. Transcranial Doppler was the most commonly used method for measuring CBF and changing the respiratory rate and/or minute ventilation were the most commonly used method to change the CO2 tension. CVR-CO2 is maintained with both inhalational and intravenous anesthetic agents within the range of concentrations used in clinical anesthesia. At doses leading to a broadly equivalent depth of anesthesia, the reactivity value was highest with isoflurane and the least with propofol. Individual agents differ in their degree of reactivity to hypercapnic and hypocapnic stimuli. CVR-CO2 is impaired in elderly patients when compared with young patients with both sevoflurane and propofol anesthesia. In patients with medical comorbidities, the CVR-CO2 impairment under anesthesia was associated with the severity of the underlying diseases and not the anesthetic agents. CONCLUSIONS: Our systematic review showed that within the clinical anesthesia concentrations, CVR-CO2 is maintained under both propofol and inhalational agents. However, most of the information available is from non-neurosurgical patients and these studies also suffer from significant methodological heterogeneity. Therefore, we were limited by the amount and the quality of data available for this review.