Rohini Surve

The effect of blood transfusion on central venous oxygen saturation in critically ill patients admitted to a neurointensive care unit

Literature suggests poorer outcomes during anaemia as well as following red blood cell transfusion (BT) in brain injured patients. Recently, central venous oxygen saturation (ScvO2) has been proposed as a physiological trigger to guide red BT. In this study, we looked at ScvO2 changes following BT in patients admitted to a neurointensive care unit (NICU).

Incidence and risk factors for oxygen desaturation during recovery from modified electroconvulsive therapy: A prospective observational study.

BACKGROUND AND AIMS Electroconvulsive therapy (ECT) is an established modality of treatment for severe psychiatric illnesses. Among the various complications associated with ECT, oxygen desaturation is often under reported. None of the previous studies has evaluated the predictive factors for oxygen desaturation during ECT. The objective of this study was to evaluate the incidence of oxygen desaturation during recovery from anesthesia for modified ECT and evaluate its risk factors in a large sample. MATERIALS AND METHODS All patients aged above 15 years who were prescribed a modified ECT for their psychiatric illness over 1 year were prospectively included in this observational study. The association between age, body mass index (BMI), doses of thiopentone and suxamethonium, stimulus current, ECT session number, pre- and post-ECT heart rate and mean arterial pressure, seizure duration, and pre- and post ECT oxygen saturation, was systematically studied. RESULTS The incidence of oxygen desaturation was 29% (93/316 patients). Seizure duration and BMI were found to be significantly correlated with post ECT desaturation. CONCLUSION In this prospective observational study, the incidence of oxygen desaturation during recovery from anesthesia for ECT was high. The study identified obesity and duration of seizure as the independent predictors of this complication. This knowledge is likely to help in identifying and optimizing such patients before subsequent ECT sessions.

Massive cerebral air embolism during stent-assisted coiling of internal carotid artery aneurysm

The clinical and radiological findings are given in Table 1. In both the patients, there was no desaturation throughout the procedure. Dexamethasone and mannitol was given to prevent cerebral edema and loading dose of phenytoin was administered for seizures prophylaxis. Both patients developed seizures within 24 h of Neurointensive Care Unit (NICU) stay. Case 1 received only benzodiazepine as treatment for seizures, whereas Case 2 received in addition low‐dose thiopentone infusion for seizures and vasopressors to induce hypertension (systolic BP ≥ 150 mmHg). In Case 1, there was no improvement in the neurological status. She had tracheostomy and weaned from ventilator and later transferred to a general hospital in a severely disabled state. Case 2 improved completely and was extubated on day 3. The exact source of air entry could not be identified in Case 1 and it was assumed that air might have entered during hand injection of the contrast agent. In Case 2, the pressurized nimodepine arterial flush bottle was found empty.

Papaverine is a confounding factor in neurological assessment after cerebral aneurysm clipping: Report of three cases and review of the literature

Intracisternal papaverine instillation is being used across many centers after cerebral aneurysm clipping to prevent and treat cerebral vasospasm. Pupillary dilatation secondary to papaverine can interfere with the neurological assessment postoperatively. This report describes pupillary changes in three patients following the papaverine application after craniotomy and aneurysm clipping, with one patient developing contralateral pupillary dilatation and the other two having bilateral pupillary dilatation. The pupillary changes resolved over 30 min to 4 h postoperatively. We conclude that pupillary changes following papaverine instillation could be a transient phenomenon and should not be considered ominous in absence of new onset neurological deficits. Intraoperative somatosensory evoked potential monitoring also helped in postoperative decision making in all our cases.

Electrocautery interference with intraoperative capnography during neurosurgery.

Patient function monitors used during anaesthesia such as the electrocardiogram and electroencephalogram, contain electrical signals that are vulnerable to contamination by high frequency signals like electrocautery. These monitors generally incorporate tools to detect, filter and reject these electromagnetic artefacts. But there is no documentation in the literature about the effect of electrocautery on capnography. We report an intraoperative use of monopolar electrocautery interfering with the capnogram waveforms causing artefactual change in its value. A 38-year-old male was undergoing evacuation of an acute subdural hematoma under general anaesthesia. A mainstream infra-red capnometer from an Ultra view SL monitor with 91517 capnography module (Space Labs Medical, Redmond, WA, USA) was used for measuring carbon dioxide. The adapter was (calibrated manually after stabilizing CO2 value to room air) zeroed to atmosphere before use. During the course of surgery, a monopolar cautery (Maestro Plus 100, Larsen and Toubro limited, India) was used for dissection of the muscles during craniotomy. The PETCO2 value, which was maintained between 30 and 32 mm Hg until that time, rose suddenly to 62 mm Hg with abnormal capnogram (Fig. 1a). Following cessation of its use, both the capnogram and PETCO2 value reverted back to normal in a few seconds (Fig. 1b). This distortion in the PETCO2 value and capnogram was reproducible with repeated use of monopolar cautery. The other possible causes for increases in PETCO2 were however, simultaneously excluded. The procedure was commenced and completed uneventfully by switching over to bipolar cautery, with no changes in PETCO2 values or capnogram. Continuous monitoring of PETCO2 is a standard of care during anaesthesia. Abnormal PETCO2 values are an important determinant of adverse outcome in patients with traumatic brain injury. Both low PETCO2 (causing reduction in cerebral blood flow and predisposing to cerebral ischemia) and high values (causing increased cerebral blood flow and thereby worsening of elevated intracranial pressure) are deleterious to the injured brain, especially in acute scenario. Hence accurate monitoring of PETCO2 during anaesthesia for such surgeries is critical. There is no published data or report on the effect of electrocautery on PETCO2 values or the capnogram. Hence, it is likely that an anaesthesiologist might be tempted to intervene when such acute changes in PETCO2 occur during a critical part of neurosurgery. Therefore, this report is an attempt to highlight that the use of monopolar cautery can falsely alter the PETCO2 values and the capnogram. Judicious interpretation and awareness about such possible artefacts can avert unnecessary interventions. Monopolar electrocautery generates high voltage electromagnetic fields, affecting the monitoring parameters which measure small electrical activities such as electrocardiogram [1] and electroencephalogram derived parameters as Bispectral index (BIS) [2] making them vulnerable to artefacts. However, the mechanism by which electrocautery interferes with PETCO2 is not known. The mainstream capnograph incorporates an infrared (IR) sensor which directly measures the absorbance of IR light due to the presence of CO2 and the electromagnetic interference from the electrocautery might have interfered with the measurement electronics in the capnograph leading to R. Surve S. Madhusudan K. Sriganesh (&) Department of Neuroanaesthesia, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore 560029, India e-mail: drsri23@rediffmail.com

Regional cerebral tissue oxygen saturation changes following blood transfusion in neuro-intensive care unit patients - a pilot observational study: Blood transfusion and cerebral tissue oxygen saturation

Although central venous oxygen saturation (ScvO2) is used to decide on red blood cell (RBC) transfusion, whether its improvement is associated with parallel improvement in cerebral oxygenation is not adequately studied. This study looked at changes in regional cerebral tissue oxygen saturation (rSO2) following RBC transfusion in neuro‐intensive care unit (ICU) patients.

Intraoperative aberrant bispectral index values due to facial nerve monitoring

Bispectral index is an accepted depth of anaesthesia monitor for guiding intraoperative hypnotic agent administration. Frontalis EMG displayed on BIS monitor may increase due to twitching of frontalis muscle. EMG increases are also known to cause artefactual increases in BIS values. We report a case of artefactual increase of EMG and subsequently BIS values, due to electrical artefact from cranial nerve stimulator being used to identify the facial nerve. An explanation of the effect of stimulator signal on BIS EMG and BIS values has been provided.

Anesthetic management of a paraparetic patient with multiple lung bullae.

To JNA Readers: A 60-year-old man presented with history of a fall 6 months back after which he developed neck pain, lower limb weakness, and urinary retention. There were no respiratory complaints. Medical history was not significant. Hypertonia was present in both the lower limbs with power of 3/5. The lungs were clear on auscultation. Magnetic resonance imaging of the spine revealed cord compression at the cervical (C3-C5) and thoracic (T10) levels. Laminectomy at T10T11 and excision of T10-T12 ossified ligamentum flavum were planned. X-ray reports of the chest showed bilateral upper-zone focal abnormalities with fibrotic bands and emphysematous changes. Computed tomography scan of the chest showed bilateral gross pleural thickening, upper-zone lesions with fibrotic strands, and calcified mediastinal lymph nodes (Fig. 1A). On the right side, multiple large emphysematous bullae were seen (Fig. 1B). Radiologic findings were suggestive of pulmonary tuberculosis. Pulmonary function test revealed severe restriction. In view of emphysematous bullae, general anesthesia (GA) with spontaneous respiration was planned to avoid positive pressure ventilation (PPV). Patient was premedicated with 0.2mg of glycopyrrolate and 1mg of midazolam intravenously. Airway was anesthetized with 4% lignocaine nebulization, topical 10% spray, and transtracheal block. A dosage of 50mg of propofol and a dosage of 40mg IV fentanyl were given to facilitate intubation. Anesthesia was maintained using 1% to 2% sevoflurane and O2 with air (35:75). Analgesia was provided with fentanyl boluses. Throughout the procedure, spontaneous respiration was maintained (respiratory rate 8 to 12/min, end tidal carbon dioxide 40 to 42mm Hg). Airway pressures and systemic parameters were monitored carefully to diagnose the occurrence of pneumothorax at the earliest. Postoperatively, patient was breathing comfortably with no new complications. Bulla is a pathologic entity caused by a confluence of 2 or more terminal elements of bronchial tree. It may get infected or enlarge progressively and may lead to pneumothorax. It exists frequently in conditions like tuberculosis. Various anesthetic techniques have been tried in patients with bullae presenting for extrathoracic surgery such as GA with double-lumen tube,1 inhalational anesthetics and spontaneous ventilation,2 and awake craniotomy using dexmedetomidine sedation. Iwakura et al used spontaneous ventilation, although initially succinylcholine was used to facilitate intubation. Because of preoperative paraparesis, we avoided succinylcholine. To blunt airway reflexes, we used topical anesthesia and airway blocks. In another case report, authors have used laryngeal mask airway with epidural catheter in a spontaneously breathing patient. We did not consider regional anesthesia, despite being a good option in patients with lung bulla, in view of preoperative limb weakness. Placing a patient in prone position presents significant challenges to the anesthetist. A decrease in the mean arterial pressure, stroke volume, and the cardiac index can occur. Abdominal compression can worsen the obstruction to inferior vena cava leading to an increased surgical-site bleeding. Accidental extubation and endotracheal tube obstruction are other feared complications. Prone position increases functional residual capacity and improves oxygenation by reducing the ventilation perfusion mismatch. Spontaneous breathing can have synergistic effect with prone position. Active

Influence of acute haemodynamic changes on the oxygen saturation during electro-convulsive therapy

Background: Electro-convulsive therapy (ECT) is a safe and effective treatment for various psychiatric disorders. Among the various complications associated with ECT, acute haemodynamic responses and decrease in the oxygen saturation are the most common. The current study is designed to evaluate the relationship between the haemodynamic response and oxygen de-saturation occurring during ECT. Materials and Methods: Patients undergoing modified ECT for their psychiatric illness over a one-year period were prospectively included in this observational study. The following parameters were collected from each patient: Age, body mass index (BMI), doses of thiopentone and suxamethonium, stimulus current, ECT session number, pre-and post-ECT heart rate, systolic, diastolic and mean arterial pressure, seizure duration and pre- and post-ECT oxygen saturation. Results: The incidence of oxygen de-saturation was 27% (139/507 sessions). The change in the heart rate and systolic blood pressure caused by ECT and the BMI of the patient were independently predictive of the change in the oxygen saturation. Conclusions: The current study identified ECT-induced acute haemodynamic changes as independent predictors of severity of oxygen de-saturation.