Comparative incidence of cardiovascular changes during venous air embolism as detected by transesophageal echocardiography alone or in combination with end tidal carbon dioxide tension monitoring.

The objective of our study was to compare the incidences of cardiovascular disturbance during venous air embolism (VAE) episodes detected using transesophageal echocardiography (TEE) and end tidal carbon dioxide (ETCO(2)) tension monitoring. We retrospectively analyzed the anesthesia records of patients who underwent posterior fossa surgery while in the sitting position and who were simultaneously monitored using both TEE and ETCO(2) tension monitoring. Data on the occurrence of VAE and the cardiovascular changes associated with it were recorded. Patients were divided into the ETCO(2)-positive group (both TEE and ETCO(2) tension monitoring indicated VAE) and the ETCO(2)-negative group (TEE alone indicated VAE, no significant drop in ETCO(2)). No instances of cardiovascular disturbance were detected in the ETCO(2)-negative group, whereas the incidences of tachycardia and hypotension were 20% and 30%, respectively, in the ETCO(2)-positive group. None of the episodes of VAE detected by TEE (without a fall in ETCO(2)) were clinically significant. We conclude that ETCO(2) monitoring is sensitive enough to detect hemodynamically significant VAE episodes.

Saline flush test for bedside detection of misplaced subclavian vein catheter into ipsilateral internal jugular vein.

BACKGROUND: The most common misplacement during subclavian vein (SCV) catheterization is into the ipsilateral internal jugular vein (IJV). Chest radiography is the gold standard for the confirmation of correct placement. However, it is time-consuming and has the disadvantage of radiation exposure. We assessed the sensitivity and specificity of our previously reported 'flush test' for confirming correct central line placement. METHODS: All neurosurgical patients who underwent successful SCV catheterization on the right side by an infraclavicular approach were enrolled in this study. The flush test was performed by injecting 10 ml of normal saline in the distal port of catheter, while anterior angle of ipsilateral neck was palpated by an independent observer. A thrill of fluid elicited on the palm of hand (positive test) was suggestive of misplaced catheter into ipsilateral IJV. This was confirmed with chest fluoroscopy. RESULTS: SCV catheterization was performed in 570 patients. The flush test was positive in 19 patients (3.3%) and negative in 551 patients (96.7%). There were 26 (4.6%) misplacements as detected by chest radiography; 19 entered the IJV (3.3%) and seven the contralateral SCV (1.2%). In all patients who had a misplaced catheter into the ipsilateral IJV, the flush test results were positive, whereas the results were negative in patients who had normally placed catheter or misplaced catheter elsewhere. It was found that the test had 100% sensitivity and specificity to detect misplacement of SCV catheter into the ipsilateral IJV. CONCLUSIONS: Saline flush test is a simple and sensitive bedside test that successfully detects misplaced SCV catheters into ipsilateral IJV.

Intra-ocular pressure changes associated with intubation with the intubating laryngeal mask airway compared with conventional laryngoscopy.

This open, prospective, randomised study was designed to evaluate the changes in intra-ocular pressure and haemodynamics after tracheal intubation using either the intubating laryngeal mask airway (ILMA) or direct laryngoscopy. Sixty adult patients, ASA physical status 1 or 2 with normal intra-ocular pressure were randomly allocated to one of the two techniques. Anaesthesia was induced with propofol followed by rocuronium. Tracheal intubation was performed using either the ILMA or Macintosh laryngoscope. Intra-ocular pressure, heart rate and blood pressure were measured immediately before and after tracheal intubation and then minutely for five minutes. In the laryngoscopy group there was a significant increase in intra-ocular pressure (from 7.2+/-1.4 to 16.8+/-5.3 mmHg, P<0.01), which did not return to pre-intubation levels within five minutes, and also in mean arterial pressure after tracheal intubation, which returned to baseline levels after five minutes. In the ILMA group there were no significant changes in intra-ocular pressure (from 7.6+/-1.8 to 10.4+/-2.8 mmHg, P >0.05) or mean arterial pressure after tracheal intubation. Time to successful intubation was longer with the ILMA, 56.8+/-7.8 seconds, compared with the laryngoscopy group, 33+/-3.6 seconds (P<0.01). Mucosal trauma was more frequent with the ILMA (eight of 30) compared with the laryngoscopy group (three of 30) (P<0.01). The postoperative complications were comparable. In terms of minimising increases in intra-ocular pressure and blood pressure, we conclude that the ILMA has an advantage over direct laryngoscopy for tracheal intubation.

Intracranial pressure changes during Valsalva manoeuvre in patients undergoing a neuroendoscopic procedure.

BACKGROUND: The Valsalva manoeuvre results in an increase in intrathoracic pressure which alters the systemic and cerebral circulations significantly. We decided to record changes in the intracranial pressure and cerebral perfusion pressure resulting from a Valsalva manoeuvre in anaesthetised patients. METHODS: 11 patients of either gender submitted to surgical neuroendoscopic procedures were studied. Standard general anaesthesia was maintained for the procedure in all the patients. Passive Valsalva manoeuvres were carried out by squeezing the bag of the closed breathing circuit to maintain an airway pressure of 20 cm H2O above peak inspiratory airway pressure for 10 seconds. The variables heart rate, mean arterial pressure, intracranial pressure and cerebral perfusion pressure were noted. The variables were recorded again after the surgical correction. All cardiovascular and cerebrovascular variables were compared using the Wilcoxon sign-rank test. We considered a value of p less than 0.05 to be statistically significant. RESULTS: The median age of the 11 patients was 22 years (range: 15-43) and median weight was 50 kg (range: 30-78). On comparing the variables during the two Valsalva manoeuvres, we found significant changes in HR, ICP and CPP after the surgical correction. No complications were encountered in any of the patients. CONCLUSION: There was a significant reduction in cerebral perfusion pressure during the Valsalva manoeuvre in both stages. This was a result of change in either the intracranial pressure or the mean arterial pressure. Although our patients did not suffer a clinically significant reduction in cerebral perfusion pressure and so had an uneventful recovery, the effect of Valsalva manoeuvre on cerebral perfusion pressure cannot be denied. The marked haemodynamic changes clearly warrant a cautious use of this manoeuvre in neurosurgical practice.

Complications related to positioning in posterior fossa craniectomy.

To compare complications associated with surgical position, a retrospective study was conducted on 260 patients who underwent posterior fossa craniectomy. Data collected from the records included demographic profile, American Society of Anesthesiologists' physical status score, neurological status, cranial nerve involvement, associated medical illnesses, anaesthetic technique, patient position, haemodynamic changes, duration of surgery, venous air embolism (VAE), blood loss/transfusion, postoperative complications, duration of ICU stay, and postoperative neurological status. Statistical analysis was done using the Chi-square test and independent t-tests. The demographic profile and preoperative associated medical illnesses of patients were comparable between groups. The incidence of end-tidal carbon dioxide (EtCO2) detected VAE was more (p=0.00) in the sitting position than the horizontal positions (15.2% vs. 1.4%). Blood loss/transfusion and the duration of surgery were significantly higher in the horizontal position (p<0.05). Brainstem handling was the most common cause of prolonged postoperative mechanical ventilation and was seen more in the sitting position. Lower cranial nerve functions were preserved better in the sitting position (p<0.05). Most postoperative complications (surgical or otherwise) were comparable between the groups (p>0.05). Most patients in both groups developed mild-to-moderate disability with independent lifestyle at the seventh postoperative day. To conclude, both sitting and horizontal positions can be used safely in posterior fossa surgeries.

Variations in cerebral haemodynamics during irrigation phase in neuroendoscopic procedures.

Not many centres measure intracranial pressure during an endoscopic procedure. However, if the irrigation fluid during endoscopy is not simultaneously drained, then some rise in intracranial pressure can be anticipated. This study was carried out to measure and monitor changes in intracranial pressure during the irrigation phase in a neuroendoscopic procedure using a Codman catheter placed in the parenchyma. Intracranial pressure was monitored in 13 patients undergoing surgical neuroendoscopic procedures under a standardised anaesthetic technique. Heart rate, mean arterial pressure, intracranial pressure and cerebral perfusion pressure were recorded at baseline and during the irrigation phase of the procedure. The heart rate during irrigation was comparable to baseline values, but the mean arterial pressure at the time of irrigation increased an average of 7 mmHg (P = 0.02). At the same time there was an average 34 mmHg increase in intracranial pressure (P < 0.001), producing an average 26 mmHg decrease in the cerebral perfusion pressure (P < 0.001) during irrigation. There was an average of four episodes of raised intracranial pressure (>25 mmHg) during the irrigation phase per patient. We suggest that the intracranial pressure be routinely monitored during neuroendoscopic procedures. Only then can the potential adverse effect of irrigation on intracranial pressure and cerebral perfusion pressure be assessed.

Scheduled prophylactic ondansetron administration did not improve its antiemetic efficacy after intracranial tumour resection surgery in children.

BACKGROUND AND OBJECTIVE: Postoperative nausea and vomiting after craniotomy may increase intracranial pressure and morbidity in children. This prospective, randomized, placebo-controlled and double-blinded study was designed to evaluate the antiemetic efficacy of prophylactic ondansetron after intracranial tumour resections in children. METHODS: Ninety children were divided into three groups and received saline (Group 1), ondansetron 150 microg kg-1 intravenously at dural closure (Group 2) or two doses of ondansetron 150 microg kg-1 intravenously, the second dose repeated after 6 h (Group 3). Episodes of nausea, emesis and side-effects were noted for 24 h postoperatively. RESULTS: Overall 24 h incidence of postoperative nausea and vomiting was not significantly different among the three groups (9 (37.5%) in Group 1 vs. 7 (27%) in Group 2 and 8 (32%) in Group 3, P = 0.73). No difference in rescue antiemetic treatment or postoperative nausea and vomiting at specific time intervals (0-6 and 6-24 h postoperative period) was seen among the three groups. No significant side-effects were noted in any of the three groups. CONCLUSIONS: Ondansetron, in this study of 90 children, was not very effective in preventing nausea and vomiting after neurosurgical operations.

Atypical presentations in Chiari II malformation.

Myelomeningocele with Chiari II malformation and hydrocephalus is a common association seen in infants with a congenital failure of neurulation. Here we report two cases of such an association presenting with different sets of problems. The first patient presented with severe inspiratory stridor due to bilateral abductor vocal cord paralysis, which was relieved completely within 24 h of definitive surgery. The second patient experienced intraoperative cardiac arrest. Definitive surgery was followed after successful cardiopulmonary resuscitation. The cause of the perioperative sequence of events in both cases is attributed to the associated pathologies of Chiari II malformation.

Lidocaine infiltration of the scalp does not completely abolish increased intraocular pressure due to skull pin insertion.

Insertion of skull pins results in haemodynamic perturbations, which can be blunted by local anaesthetic infiltration of the pin sites. No study has assessed the effects on intraocular pressure. General anaesthesia was induced in 71 patients undergoing cervical spine surgery with attachment of Gardner Wells tongs to the skull. Skull pins were attached five minutes after induction following either saline (group I, 35 patients) or lidocaine (group II, 36 patients) infiltration of scalp. Intraocular pressure, mean arterial pressure and heart rate were recorded before (baseline), immediately after, and 60 s following pin insertion and analysed statistically. Insertion of pins increased intraocular pressure in both groups (from 8.4+/-2.7 to 14.2+/-3.0 mmHg in group I, and from 8.8+/-2.3 to 12.7+/-2.7 mmHg in group II, P < 0.001), which persisted even at 60 s but the increase was significantly greater in group I. Insertion of pins significantly increased blood pressure in group I only. We conclude that lidocaine infiltration at the skull pin sites for Gardner Wells tong attachment fails to completely abolish increased intraocular pressure.

Effect of orientation of a standard polyvinyl chloride tracheal tube on success rates during awake flexible fibreoptic intubation.

We conducted a randomised study in 70 patients to assess the effect of orientation of a standard polyvinyl chloride tracheal tube on the ease of railroading the tube during awake fiberoptic orotracheal intubation. Conventional orientation of the tube (with the bevel of the tube directed to the patient's left) was compared with orientation of the tube with the bevel facing posteriorly. The success rate of intubation at the first attempt was higher with the bevel oriented posteriorly (35/35; 100%) than with the conventional orientation (21/35; 60%; p = 0.0001), and the intubating time was shorter (median (range) 7 (5-11) s and 11 (5-60) s, respectively; p = 0.0001). We recommend that the tracheal tube should be aligned in this manner when railroading it over the fibrescope during awake fibreoptic orotracheal intubation.

Severe bradycardia and hypotension after connecting negative pressure to the subgaleal drain during craniotomy closure.

Negative pressure drainage systems are often used after craniotomy for evacuation of potential bleeding. There are several reports of haemodynamic disturbances with epidural negative pressure drainage, but such reports are very few for subgaleal drains placed over the bone flap. We report a case in which a patient developed severe cardiovascular disturbances after the vacuum drainage was connected to a subgaleal drain after craniotomy for aneurysm clipping. The patient had no significant cardiac history, had an uneventful intra-operative course and yet developed bradycardia and hypotension, which were reproducible and severe enough to require atropine administration. Anaesthetists must be aware of these effects, so that they can anticipate and treat such complications.

Sudden asystole during surgery in the cerebellopontine angle.

We report a case of a 40-year-old lady undergoing surgery for a tumor in the cerebellopontine angle. Intraoperatively, patient had a sudden asystole without prior warning sign of bradycardia. It could have been the severe form of trigeminocardiac reflex. The cardiac rhythm returned spontaneously once the surgical manipulation stopped. The remainder of the operation was uneventful and no complication occurred afterwards. The possible mechanism of the event is discussed.

Intracranial pressure and haemodynamic changes during the tunnelling phase of ventriculoperitoneal shunt insertion.

BACKGROUND AND OBJECTIVE: The tunnelling phase of ventriculoperitoneal shunt insertion is the most painful part but patients are often given inadequate opioid analgesic for fear of post operative delayed recovery and/or respiratory depression. This may result in an increase in intracranial pressure. METHODS: Twenty adults scheduled to undergo ventriculoperitoneal shunt insertion were administered standard anaesthesia. Monitoring included heart rate, electrocardiogram, end-tidal carbon dioxide, invasive blood pressure, and oxygen saturation. Intracranial pressure was monitored by placing the ventricular end of shunt catheter in the dilated lateral ventricle. Five minutes before tunnelling, fentanyl 1 microg kg(-1) was administered. Mean arterial pressure, heart rate and intracranial pressure were recorded during tunnelling and subsequently at 1-min interval for 5 min. Data were analysed using t-test and repeated measured test. RESULTS: Tunnelling caused significant increase in mean arterial pressure (from 81.4 +/- 11.0 to 110.9 +/- 15.3 mmHg, P < 0.05), intracranial pressure (from 21.4 +/- 8.1 to 29.2 +/- 12.5 mmHg, P < 0.05) and heart rate (from 74.4 +/- 13.8 to 94.1 +/- 17.8 beats min(-1), P < 0.05). Whereas, the increase in haemodynamic parameters persisted for 3 min post-tunnelling, elevated intracranial pressure lasted for 2 min. CONCLUSION: Tunnelling significantly increases intracranial pressure and blood pressure despite prior fentanyl administration. This may be deleterious in the presence of intracranial pathology.

Anaesthetic management of Osler-Weber-Rendu syndrome with coexisting congenital methaemoglobinaemia.

A 9-year-old cyanosed child suffering from Osler-Weber-Rendu syndrome with bilateral pulmonary arteriovenous malformations (PAVMs) was posted for cerebral angiography under general anaesthesia. Careful preanaesthetic evaluation led to the diagnosis of coexisting congenital methaemoglobinaemia. There is no previous report of Osler-Weber-Rendu syndrome coexisting with congenital methaemoglobinaemia. This report emphasizes that a second contributory cause of cyanosis must be suspected and meticulously looked for if the symptomatology in a patient cannot be explained by a single established diagnosis. Positive-pressure ventilation was associated with reduction in arterial oxygenation despite an increasing inspired oxygen concentration, which returned to preanaesthetic levels only after extubation and resumption of spontaneous respiration.

Effects of stellate ganglion block on cerebral haemodynamics as assessed by transcranial Doppler ultrasonography.

BACKGROUND: Stellate ganglion block (SGB) causes vasodilatation in the skin of the head and neck because of regional sympathetic block. Its effects on cerebral haemodynamics, in health or in disease, are not clear. We evaluated the effects of SGB on ipsilateral middle cerebral artery flow velocity (MCAFV), estimated cerebral perfusion pressure (eCPP), zero flow pressure (ZFP), carbon dioxide reactivity (CO2R) and cerebral autoregulation using transcranial Doppler ultrasonography (TCD). METHODS: Twenty male patients, with pre-existing brachial plexus injury, and undergoing SGB for the treatment of complex regional pain syndrome of the upper limb, were studied. For SGB, 10 ml of plain lidocaine 2% was used and the onset of block was confirmed by presence of ipsilateral Horner's syndrome. The MCAFV, eCPP, ZFP, CO2R, and cerebral autoregulation were assessed before and after SGB using established TCD methods. The changes in these variables were analysed using Wilcoxon's signed rank test. RESULTS: The block caused a significant decrease in MCAFV from median (inter-quartile range) value of 61 (53, 67) to 55 (46, 60) cm s(-1), a significant increase in eCPP from 59 (51, 67) to 70 (60, 78) mm Hg, and a significant decrease in ZFP from 32 (26, 39) to 25 (16, 30) mm Hg. There were no significant changes in CO2R or cerebral autoregulation. CONCLUSION: The increase in eCPP, decrease in ZFP, and no changes in CO2R or cerebral autoregulation suggest that the SGB decreases cerebral vascular tone without affecting the capacity of the vessels to autoregulate. These effects may be of therapeutic advantage in relieving cerebral vasospasm in certain clinical settings.