Byrappa Vinay

An abrupt reduction in end-tidal carbon-dioxide during neurosurgery is not always due to venous air embolism: a capnograph artefact

Venous air embolism (VAE) is a well recognized complication during neurosurgery. Pre-cordial doppler and trans-esophageal echocardiography are sensitive monitors for the detection of VAE. A sudden, abrupt reduction in the end-tidal carbondioxide (ETCO2) pressure with associated hypotension during neurosurgery might suggest VAE, when more sensitive monitors are not available. We describe an unusual cause for sudden reduction in ETCO2 during neurosurgery and discuss the mechanism for such presentation.

Acute kidney injury in survivors of surgery for severe traumatic brain injury: Incidence, risk factors, and outcome from a tertiary neuroscience center in India

Abstract Background. Non-neurological complications like acute kidney injury (AKI) can affect outcome of traumatic brain injury (TBI). This study aims to analyze the incidence, predictive factors, and impact of AKI in operated patients with severe TBI. Methods. We retrospectively reviewed the data of 395 patients who underwent surgery for severe TBI and survived to be discharged from the hospital over a 1-year period. Of these, 95 patients were finally included in the analysis. Their demographic data, laboratory parameters, and clinical courses were reviewed. Diagnosis and staging of AKI was made using Acute Kidney Injury Network (AKIN) criteria. Results. The incidence of AKI was 11.6% (11 patients). Out of the11 patients who had AKI, 7 were in stage I (63.6%), 3 were in stage II (27.3%), and 1 in stage III (9.1%). Nine Patients (81.8%) developed AKI within 5 days of admission. Aminoglycoside therapy had an association with occurrence of AKI. There was no mortality and none of the patients required renal replacement therapy (RRT). Renal function of all these patients returned to baseline before hospital discharge. Hospital stay and intensive care unit (ICU) stay were longer and Glasgow coma scale (GCS) was lower in patients with AKI when compared with patients without AKI group at discharge. Conclusion. Reversible AKI without need for RRT occurred in nearly12% of patients with severe TBI requiring surgical intervention. Aminoglycoside therapy was the only predictive factor for the occurrence of AKI. Patients with AKI have a longer period of mechanical ventilation, longer ICU and hospital stay, and poorer GCS at discharge.

Fall in inspired oxygen and anaesthetic agent concentrations during change of soda lime absorber

Following an episode of reduction in inspired oxygen concentration (FiO2) and inhalational agent concentration (Fi agent) during the changing of a soda lime absorber, We conducted an in vitro experiment to understand the impact of disconnection of the absorber on inspired gas dilution at different fresh gas flows. We found that both in Dräger Fabius GS and Primus anaesthesia work stations, disconnection of the absorber caused progressive reduction in FiO2 and Fi agent as the FGF was decreased. The operating principle of fresh gas decoupling (FGD) valve is a potential source of this complication, which must be kept in mind while changing the soda lime during the course of surgery where an anaesthetic work stations utilizing FGD valves are used.

Anesthetic management of patients with Joubert syndrome: a retrospective analysis of a single-institutional case series.

To analyze the anesthetic techniques used for sedation during magnetic resonance imaging (MRI) study of patients with Joubert syndrome (JS) and assess the safety and efficacy of these anesthetic regimens in these children.

Dräger Fabius GS Ventilator Failure: An Unusual Cause.

Understanding the functioning of modern anesthesia workstations is very important because workstation failures in the intraoperative period may place the patient at risk of perioperative hypoxia and lead to unnecessary anxiety and confusion among anesthesia care providers. We present and simulate a critical event leading to Dräger Fabius GS ventilator failure.

Importance of education in interpretation of alarms.

March 2013 • Volume 116 • Number 3 www.anesthesia-analgesia.org 735 DOI: 10.1213/ANE.0b013e318280dff4 Greenhouse gas (GHG) emissions associated with inhaled agents may be larger than previously suggested. The estimate cited by Sulbaek Andersen et al.2 for the total worldwide contribution of inhaled anesthetics to global warming—0.01%—is problematic. The authors based their extrapolation on only 1 US institution that uses comparatively little desflurane (the volatile agent contributing the greatest GHG pollution), and admittedly failed to account for nitrous oxide (N2O)—effectively underestimating contributions.a Furthermore, the 0.01% estimate ignores all dental, veterinary, and laboratory medicine use, as well as other life cycle phases such as manufacturing and transportation.b The true contribution of inhaled anesthetics is likely much higher, and reduction could easily be accomplished using strategies discussed in a recent editorial.c,3 Mychaskiw and Eger1 also note cost as important in decision-making in health care, and I agree. Interestingly, many environmental improvements to the practice of health care are financially advantageous, such as reprocessing medical devices, recycling, and minimizing hazardous waste.d Feldman demonstrated how routinely minimizing fresh gas flows could compound significantly over a career to avoid waste.4 Sulbaek Andersen et al.5 state “(e)xercising care to avoid excessive use of anesthetic gases has the double benefit of reducing health care costs and protecting the environment.” Does a particular anesthetic reduce cost as well? While Eger and Shafer showed that desflurane could result in faster wake up times compared with that of other volatile agents in surgeries of short duration (<90 minutes), for longer surgeries, desflurane wake up times (time to 85% mean alveolar concentration decrement in vessel rich groups) are comparable with those of the other volatile agents.6 However, in this study, the volatile agent concentration was maintained at 1 MAC until the end of surgery instead of tapering it down as we do in actual practice, and therefore the difference between anesthetics was likely exaggerated. Whether shorter wake up times after shorter surgeries offset the higher cost of desflurane depends on many factors including: patient payor mix, efficiency of room turnover, staff reimbursement system, and availability of patients to fill potential operating room times.e A culture shift has begun in medicine (Healthier Hospitals Initiative, f CleanMedg national scientific meetings, Choose Wiselyh national campaign to reduce unnecessary laboratory testing). We as a specialty pride ourselves on flexibility and balance of multiple factors, including patient safety. Long-term public health impacts are also part of a more efficient health care practice. The specialty of anesthesia should open its collective mind to exploring a safe practice within a new, more sustainable paradigm.

An unusual cause of high peak airway pressure: Interpretation of displayed alarms

Airway pressure monitoring is critical in modern day anesthesia ventilators to detect and warn high or low pressure conditions in the breathing system. We report a scenario leading to unexpectedly very high peak inspiratory pressure in the intraoperative period and describe the mechanism for high priority alarm activation. We also discuss the role of a blocked bacterial filter in causing sustained display of increased airway pressure. This scenario is a very good example for understanding the unique safety feature present in the Dräger ventilators and the attending anesthesiologist must have an adequate knowledge of the functioning and safety feature of the ventilators they are using to interpret the alarms in the perioperative to prevent unnecessary anxiety and intervention.

Extreme hemodynamic fluctuations: Importance of understanding the principles of syringe pump function

Sir, Infusion devices remain high-risk devices capable of delivering drugs unpredictably leading to mortality and morbidity. The problem of performance, degradation, and quality was the cause for 20% of reported incidences relating to the infusion pump in UK between 1990 and 2000.[1] Thus, it is important for the clinician to be familiar with the features and function of the infusion device they are using. A 55-year-old lady with middle cerebral artery aneurysm underwent microsurgical clipping of the aneurysm under general anesthesia uneventfully. After clipping, with the target of raising systolic blood pressure (SBP) to 160 mm Hg, noradrenalin infusion was started at 1.6 μg/min. The solution was prepared in a 50 ml syringe with 8 mg of noradrenaline bitartrate diluted in 40 mL normal saline and infused at 2 mL/h. The solution was infused using Orchestra® DPS + (Fresenius Kabi) infusion pump. (Ref 082594/21126459) La Grand Chamin-38590 Brezins- France. Initially, there was a surge in SBP up to 240 mm Hg. No intervention was done as the surge was expected to settle down. However, after the blood pressure decreased to 110 mm Hg, there was another surge in SBP up to 200 mm Hg after approximately 5 min. This was followed by 4 similar cyclical surges at 10 min intervals [Figure 1]. We changed the syringe but again the fluctuations in blood pressure persisted. Figure 1 Snapshot showing graphical representation of fluctuation in invasive blood pressure Pulsatile flow of drug at low dose rates in syringe pump was then thought to be the cause and to smoothen the fluctuations, the drug in the syringe solution was double diluted (i.e. 4 mg in 40 mL) and the dose rate was also doubled (4 mL/h). Following this intervention, the surges flattened out considerably, and the SBP fluctuated between 170 and 150 mm Hg thereafter [Figure 1]. The Orchestra® DPS + pump uses stepper motors with the lead screw, and the flow rate accuracy of the motor is documented to be ± 1% on drive mechanism and ±2% on syringes.[2] However, at low flow rates, the flow may be discontinuous and pulsatile. Stepper motors are known to produce flow in a series of discrete fixed volume pulses. The volume and rate of pulses at fixed flow rates depend on the number of steps per revolution of the lead screw. If the time duration between the pulses is relatively large compared to the half-life of the drug, the result may be wide variation in effect of the drug.[3] Another reason may be stiction (i.e., the friction which tends to prevent stationary surfaces from being set in motion) between syringe plunger and barrel.[4] A similar problem was investigated by Capes et al. and they found Terumo syringes to be significantly associated with the noncontinuous flow.[5] In our case, the syringe change did not affect the fluctuations while increasing the flow rates with the same syringe caused smoothening of fluctuations. Thus, it appears that the motor mechanism to be at fault at low flow rates. This effect though occasionally observed is of serious concern and the technique described here may be easily employed to mitigate the problem.

Artery of Percheron infarct: An unusual cause for non-awakening from anesthesia.

Sir, Delayed awakening after general anesthesia is usually attributable to causes like hypothermia, metabolic disturbances, relative or absolute over dosage of medications and anesthetics used in the peri-operative period.[1] However sometimes in clinical practice, we encounter rare causes for nonawakening after general anesthesia. Here, we describe a rare cause for nonawakening from anesthesia due to bilateral thalamic infarcts after clipping of basilar top aneurysm. A 48-year-old male patient presented with 4 days history of swaying while walking. There was no history of headache, loss of consciousness, vomiting or seizures. No other co morbidities, on examination, patient was conscious and oriented. Contrast computed tomography (CT) scan revealed a small bleb seen at high mid brain region in posterior fossa. Digital subtraction angiography confirmed the diagnosis of basilar top aneurysm [Figure 1a]. Patient was posted for microsurgical clipping of aneurysm under general anesthesia. Patient was induced with fentanyl 150 mcg, thiopentone 250 mg and rocuronium 50 mg. Induction and intra operative period were uneventful and two clips of 9 mm standard straight and 3 mm mini straight were applied to aneurysm uneventfully. Immediately after the surgery, patients Glasgow Coma Scale (GCS) was E1VtM5. Postoperative CT scan head showed pneumocephalus [Figure 1b] and patient was shifted to Intensive Care Unit (ICU) for elective mechanical ventilation and observation. Even after 48 hrs postoperative, the patients sensorium did not improve and the magnetic resonance imaging (MRI) showed bilateral thalamic infarcts [Figure ​[Figure1c1c and ​andd]d] which explained the cause for nonawakening from anesthesia. Patient was managed in ICU; he was tracheotomized, weaned from ventilator and shifted out of ICU with a GCS of E2VtM5. Figure 1 (a) Digital subtraction angiography image showing basilar tip aneurysm, (b) postoperative computed tomography scan brain showing pneumocephalus involving bilateral frontal areas, (c and d) T2-weighted flair and T2-weighted coronal image showing hyper ... When the preoperative consciousness is good and surgery is relatively uncomplicated with minimal handling, extubation in the operating room is ideal, thus after uncomplicated surgery, normothermic, and normovolemic patients recover uneventfully with minimal hemodynamic changes.[1] But in neurosurgery sometimes we encounter uncommon complications such as cerebral hemorrhage,[2] cortical venous thrombosis,[3] pneumocephalus, which lead to delayed awakening after surgery. In our case, the surgery was uneventful and immediately postoperative period patient was E1VtM5 with pupils equal and reacting. Hypothermia, metabolic abnormalities, over dosage of opiods, muscle relaxants and other anesthetics were ruled out. Based on postoperative CT scan head, we suspected pneumocephalus as the cause for delayed awakening and kept the patient under observation for 48 h. However since his sensorium did not show any improvement, we did a MRI brain, which showed bilateral thalamic infarcts. The probable anatomical cause could be, involvement of artery of Percheron, which is a normal variant of thalamic perforating branches arising from P1 segment of the posterior cerebral arteries. This branch might have been blocked while clipping of the aneurysm leading to the infarct of the bilateral thalamus.[4] Though the thalamic infarcts following clipping of basilar top aneurysm has been described previously by Jin et al.,[5] but there is no description of its effect on patients consciousness in the immediate postoperative period. This case for the first time describes thalamic infarcts as an acute cause for nonawakening of the patient immediately after the surgery. This case demonstrates that the treating anesthetist should be aware of this entity as a cause for delayed emergence or nonawakening from anesthesia after clipping of basilar top aneurysm.

Hyperpyrexia following hemispherotomy and role of unconventional therapy

A 6‐year‐old girl, weighing 30 kg presented with left‐sided limb weakness and difficulty in walking. Her parents gave 4‐year history of seizures refractory to medical management. She was treated with oxcarbazepine 600 mg/d and sodium‐valproate 450 mg/d. Electroencephalogram (EEG) demonstrated background epileptiform slow‐wave discharges with phase‐reversal on right fronto‐temporal hemisphere. Magnetic resonance imaging (MRI) showed atrophy of right hemisphere, ipsilateral lateral ventricle dilatation and signal changes in subcortical white‐matter. A diagnosis of Rasmussen encephalitis was made based on European consensus criteria.[3] Sodium‐valproate dose was increased to 450 mg/d and methylprednisolone 500 mg/d was administered for 5 days, following which she was able to walk with support. As seizure persisted, clonazepam and leviteracitam were added. Video‐EEG showed seizures arising from right hemisphere. Right functional hemispherotomy lasting 8 hours was performed to control intractable seizures under standard anaesthetic management. She received 300 ml of packed red cells. EVD was placed at the end of surgery and elective ventilation instituted for 16 hours. At extubation, tracheal secretions were mucoid and leucocyte count was 11500 cells/mm3. One hundred and fifty millilitres of clear CSF was drained over 24‐hour period. Eighteen hours after surgery, patient had a temperature spike of