Ramamani Mariappan

Circulatory collapse after topical application of vancomycin powder during spine surgery.

A hypersensitivity reaction, either anaphylactic or anaphylactoid, is a well-known adverse effect following intravenous and oral administration of vancomycin. The authors report a case of circulatory collapse and its management after the topical application of vancomycin powder during spinal instrumentation surgery. A 52-year-old woman with breast cancer and metastasis to her spine underwent a vertebrectomy of the T-10 vertebra with instrumented reconstruction from T-8 to T-12. The patient was hemodynamically stable during most of the procedure despite a 2-L blood loss requiring administration of crystalloids, colloids, packed red blood cells, and fresh-frozen plasma. During closure of the subcutaneous layer, there was a sudden drop in blood pressure from 120/60 to 30/15 mm Hg and an increase in heart rate from 95 to 105 bpm. No skin erythema or rash was visible, and there was no bronchospasm or increase in airway pressure. The patient was treated with fluids, boluses of ephedrine, phenylephrine, and adrenaline. The operation was completed and the patient woke up neurologically intact but did require blood pressure support with a norepinephrine infusion for the next 4 hours. She was discharged from hospital in a good clinical state on the 4th postoperative day. It was speculated that the rapid absorption of vancomycin powder applied on the surgical wound caused an anaphylactoid reaction and the circulatory collapse. With an increase in the use of topical vancomycin in surgical wounds, communication and awareness among all intraoperative team members is important for rapid diagnosis of an adverse reaction and for appropriate management.

Comparing the effects of oral clonidine premedication with intraoperative dexmedetomidine infusion on anesthetic requirement and recovery from anesthesia in patients undergoing major spine surgery.

Background: Clonidine, an &agr;2 agonist, has been used in anesthesia for many years to provide sedation, anxiolysis, analgesia, controlled hypotension, and to provide opioid-sparing anesthesia. Recently, there has been a great interest in using the newer &agr;2 agonist, dexmedetomidine, because of its more selectivity toward &agr;2 adrenoreceptors. We compared the effects of clonidine with dexmedetomidine on anesthetic requirement and recovery from anesthesia. Methods: Seventy-four patients undergoing major spine surgery were randomly allocated to receive either oral clonidine premedication followed by an intraoperative saline infusion (group A) or placebo premedication followed by dexmedetomidine infusion in the intraoperative period (group B). Standard anesthesia protocols were followed for induction and maintenance. Heart rate, blood pressure, and end-tidal concentrations of isoflurane were noted every 15 minutes after proning. Hypertensive responses were treated with bolus doses of propofol and fentanyl. Hypotensive episodes were treated with bolus doses of ephedrine or phenylephrine. Primary outcomes were the comparisons of the effect of these 2 drugs on anesthetic requirement and recovery from anesthesia. Secondary outcomes were the comparisons of the hemodynamic response, intraoperative analgesic requirement, and blood loss during surgery. Results: Demographic data, duration of surgery, total dose of fentanyl and propofol requirement, blood loss, and the recovery time were comparable between the 2 groups. Both drugs reduced the isoflurane requirement during surgery. However, the reduction was more and statistically significant with dexmedetomidine compared with clonidine group at 1 and 2 hours after proning (P=0.001, 0.039 at 1 and 2 h). Both drugs are equally effective in controlling the hemodynamics, and the number of episodes of hypotension, hypertension, and bradycardia were comparable between the 2 groups. Conclusions: Both clonidine and dexmedetomidine have anesthetic-sparing effect; however, it was more with dexmedetomidine than with clonidine. Recovery from isoflurane anesthesia was similar between both groups. Both are equally effective in controlling the hemodynamic response and reducing the blood loss during spine surgery.

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.

Serum lactate as a potential biomarker of malignancy in primary adult brain tumours

Lactate, a by-product of glycolysis, is an indicator of poor tissue perfusion and is a useful biomarker with prognostic value in risk-stratifying patients in several diseases. Furthermore, elevated lactate production is observed in tumour glycolysis, also known as the Warburg effect, and is essential in promoting tumour cell invasion, metastasis, and immune system evasion, promoting resistance to cell death. However, there are no studies of elevated serum lactate in brain tumour patients as a potential biomarker, to our knowledge. The aim of this study is to determine possible correlations between the malignancy of tumours and pre- and intraoperative serum lactate elevation in patients undergoing craniotomy for tumour resection. We provide initial evidence that a rise in serum lactate can be used as a non-invasive biomarker that correlates with brain tumour grade. The results from this study and future prospective studies may allow for determination of tumour progression and response to therapy using serum lactate as a biomarker.

Serum lactate as a potential biomarker of non-glial brain tumors

We assess whether serum lactate is a potential biomarker for non-glial cell brain tumors. Rapidly growing tumor cells typically have glycolytic rates up to 200 times higher than those of their normal tissues of origin and produce lactate even in the presence of oxygen. This phenomenon is called the Warburg effect. We recently showed that serum lactate levels can be used as a potential non-invasive biomarker in glial cell brain tumors, which correlates with both tumor grade and the extent of malignancy. In the present study, we found that patients with metastatic brain tumors had significantly higher baseline serum lactate levels compared to patients with meningioma and pituitary tumors. There was a statistically significant association between metastatic brain tumors and elevated serum lactate. We demonstrate that lactate can be used as a non-invasive biomarker to determine malignancy for brain tumors. Further analyses of larger populations will be needed to establish the value of serum lactate in determining the response to therapy or early recurrence.

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 Cushings 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.

Intracarotid etomidate is a safe alternative to sodium amobarbital for the Wada test.

Background: The Wada procedure (the intracarotid amobarbital procedure) has been used widely to evaluate the hemispheric dominance of language and memory before temporal lobe surgery in patients with medically refractory seizures. Because of repeated shortage of sodium amobarbital, attempts have been made to find a suitable alternative to sodium amobarbital. The aim of our study was to review our experience with the use of etomidate as an alternative to sodium amobarbital for Wada testing in patients with medically refractory seizures. Methods: After the ethics approval, we retrospectively reviewed the charts of 29 consecutive patients who underwent Wada test with etomidate. Data from a total of 50 hemispheric injections were reviewed and analyzed. This included the electroencephalographic and motor effects of etomidate injection and their time course (onset and recovery), Wada test results (language laterality and memory performance), and all adverse events during the procedure. Results: Intracarotid administration of etomidate produced a predictable electroencephalographic and motor effects in all patients. The desirable effect was seen with a single bolus dose of 2 mg followed by an infusion. Shivering was the most common side effect, seen in all the patients. Successful testing was possible in nearly all patients without any major side effects. The “pass rate” of valid tests was in good accord with our previous experience with the use of sodium amobarbital. Conclusion: From our experience, etomidate is a safe alternative to sodium amobarbital for the Wada test for determining the hemispheric dominance for speech and in predicting the memory outcome.

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.

An uncommon cause for severe hypophosphataemia after transsphenoidal pituitary surgery

Her anaesthetic management consisted of intravenous induction with midazolam (1 mg), fentanyl (150 μg), propofol (150 mg) and rocuronium (50 mg), followed by endotracheal intubation. Anaesthesia was maintained with air, oxygen, sevoflurane (1 MAC) and a low dose of remifentanil infusion (0.05‐0.1 μg/kg/min). Monitoring consisted of 5‐lead ECG, non‐invasive and invasive blood pressure, pulse oximetry, capnography, oesophageal temperature and urine output. Before surgery, nasal cavity was prepared by packing with epinephrine soaked pledgets (1 in 10,000) followed by sub mucosal infiltration of epinephrine (1 in 200,000). Intra‐operatively her vitals were stable and end tidal carbon dioxide was maintained within normal limit (32‐35 mm Hg). The blood loss (<250 ml) was very minimal. She received 2 L of crystalloids during surgery. Her urine output was 300 ml over 3 h. Intra‐operative blood work revealed hypokalaemia (K+ 2.5 mmol/l) and was treated with 40 mmols of potassium chloride (KCI) as an intravenous infusion over 2 h. Her repeat serum K+ level was 3.0 mmol/L. At the end of surgery, neuromuscular blockade was reversed and she was extubated awake in the operating room. In the post‐anaesthesia care unit (PACU), she was haemodynamically and neurologically stable and received further supplementation of 20 mmols of KCl. Repeat K+ revealed persistent hypokalaemia (2.4 mmol/L) and received another 20 mmol of KCl and was started with the maintenance fluid of 0.9% normal saline (NS) with 40 mmol of KCl at the rate of 100 ml/h. After 4 h of stay in PACU, she was transferred to neuro critical care step‐down unit (NCCU) for monitoring.

Haemodynamic and anaesthetic management of patients undergoing endovascular therapy for cerebral vasospasm

Background: Cerebral vasospasm is a common and devastating complication after a subarachnoid haemorrhage (SAH). Current guidelines for treatment recommend hypertension with euvolaemia. Endovascular therapy with cerebral angioplasty and possible administration of intra-arterial vasodilators is indicated in patients who fail medical treatment. The objective of our study was to review the haemodynamic management and anaesthetic care of patients undergoing endovascular therapy for cerebral vasospasm in our institution. Materials and Methods: The medical records of all patients who underwent endovascular therapy for cerebral vasospasm between, April 2006 and September 2012, were reviewed retrospectively. Patients with clinical vasospasm were treated initially by inducing hypertension to systolic pressures of 140 to 170 mmHg; Endovascular treatment was performed, if there was no clinical improvement. Data was collected on blood pressure measurements, anaesthetic management, duration and complications of hypertensive therapy and outcome. The differences in the pre- and post-angioplasty systolic blood pressure were statistically analysed. Results : A total of 45 patients had 47 endovascular interventions, with balloon angioplasty for proximal vessel spasm and 16 (34%) patients had additional intra-arterial injection of a vasodilator agent. Onset of vasospasm was 7 days (range 2-15 days) after SAH. Vasospasm was usually seen in multiple vessels in the same patient regardless of the site of ruptured aneurysm and was present unilaterally in 80% of the patients. All patients had a general anaesthesia for the procedure. Prior to endovascular treatment 68.9% patients required vasopressors, but post angioplasty 93.3% required them. Norepinephrine was the most commonly used (66.2%). Angioplasty was successful in reversing the cerebral vasospasm as assessed by angiography in all patients with no intra-procedure complications. Overall 80% of patients were discharged from hospital to home or to a rehabilitation centre. Conclusion: Cerebral vasospasm affects multiple vessels in the same patient. Despite endovascular therapy being a successful intervention for proximal vessel spasm, most patients still required induced hypertension with even higher levels post angioplasty compared to pre angioplasty.