Mamta Pandey

Short thyromental distance: a predictor of difficult intubation or an indicator for small blade selection?

Background:Short thyromental distance (TMD; < 5 cm) has been correlated with difficult direct laryngoscopic intubation in adult patients. The authors hypothesized that a smaller Macintosh curved blade (No. 2 MCB) would improve the predicted difficult laryngoscopy in short-TMD patients over that with a standard Macintosh curved blade (No. 3 MCB). Methods:In a preliminary study of 11 consenting adults (7 females and 4 males), American Society of Anesthesiologists physical status I and TMD ≤ 5 cm, lateral neck radiographs were recorded during laryngoscopy with a No. 2 and No. 3 MCB in sequential fashion. In a prospective clinical study, laryngoscopy and tracheal intubation were evaluated in 83 adult patients with TMD ≤ 5cm by randomly assigning them to two groups for the blade used at first intubation. Those who failed intubation with the first blade were switched to the alternate blade. In total 100 laryngoscopies and intubations were performed: the No. 2 MCB (n = 50) and the No. 3 MCB (n = 50). Results:Lateral neck radiographs recorded at the best laryngeal view revealed that the tip of the No. 2 MCB was proximal to the hyoid body with the No. 2 MCB and distal to it with the No. 3 MCB. The intubation distance (C5 to blade tip) on neck radiographs with the No. 2 MCB was significantly greater than it was with the No. 3 MCB for similar anterior jaw displacement. In the clinical study, the laryngoscopic grade with the No. 2 blade was considered easy (median, 2B), better than the grade with the No. 3 MCB (median, 3). When the No. 2 MCB was used, external laryngeal pressure improved the laryngoscopic grade (1, full glottic view) in 46% of patients. In contrast, when the No. 3 MCB was used, pressure improved the grade in only 10% of the patients. Intubation time with the No. 2 MCB was significantly (P < 0.05) less than it was in patients with No. 3 MCB. Overall, 14 patients who failed intubation with the No. 3 MCB were switched to the No. 2 MCB, and intubation was successful with an easy laryngoscopic grade. Three patients who failed intubation with the No. 2 MCB were switched to the No. 3 MCB. Conclusions:The predicted difficult laryngoscopy and intubation with the use of the adult No. 3 MCB in standard adult patients with a TMD ≤ 5cm is significantly easier with use of the smaller No. 2 MCB.

Atypical “Tails-up” Capnograph due to Breach in the Sampling Tube of Side-Stream Capnometer

Objective.An atypical “tails-up” capnograph pattern wasnoticed in a patient during the use of an accidentally crushed sampling tubewith a slit-like hole. We investigated the mechanics involved in the observedcapnograph pattern. Methods.Forty consenting ASA I patients of bothsexes presenting for tonsillectomy were included in this study. Afterintravenous induction of anaesthesia, intermittent positive pressureventilation (IPPV) using a mechanical ventilator was maintained for 20 min andthe capnograph trace, ETCO2, and inspiratory/expiratory sevofluranewere compared using a breached sampling tube and then an intact sampling tube.Similar comparisons were made during spontaneous breathing. Results.During IPPV, an atypical “tails-up” capnograph was noted usingthe breached sampling tubing. At similar inspiratory sevoflurane (2.0 ±0.03) levels, expiratory levels (0.9 ± 0.03) were significantly lowerwhen using the breached sampling tube than the intact tube (1.7 ±0.03). ETCO2 with the breached sampling tube (26.8 ± 0.30mmHg) showed significantly lower values than with the intact sampling tube (37± 0.3). During spontaneous breathing, the capnograph was normal inshape with both sampling tubes, but ETCO2 and both insp./exp.sevoflurane levels were lower with the breached sampling tube. Conclusion.During IPPV, pressure in the breathing circuit is lower during exhalation,thus allowing air to enter through the slit-like hole in the sampling tubecausing erroneously low ETCO2 and expiratory sevoflurane. Withinspiration, positive pressure in the breathing circuit, transmitted to thesampling tube, prevents air admixture and the upsurge in CO2 isdisplayed giving the capnograph an atypical “tails-up” appearance.During spontaneous breathing, since pressure in the breathing circuit barelybecomes positive during exhalation and is negative during inspiration, airmixes with the sampled gas during both phases and so the capnograph shape wasnormal but with lower values for ETCO2, insp./exp. sevoflurane, andnitrous oxide levels. If undiagnosed, this defect in the sampling tube canlead to significant errors in the measurement of inspired and expired gasconcentrations.

Modified anchoring maneuver using pilot puncture needle to facilitate internal jugular vein puncture for small children

Objectives:  Internal jugular vein (IJV) cannulation in infants has been reported with varied success using surface landmark. The aim is to share authors experience of modified anchoring technique used in infants.

Dilated ascending aorta is associated with the difficulty in correct placement of pulmonary artery catheter

The present case report highlights that a tense mega-sized aortic root and ascending aorta can mechanically resist the passage of fully inflated (1.5 ml air) balloon to wedge-trace position in the pulmonary artery. Any attempt to push the catheter rather predisposed its recoiling and rebutting into the right ventricle and the cardiac arrhythmia. Inflating continuous cardiac output catheter balloon with lesser volume of air (1 ml) is suggested to overcome this problem.

Heterogeneity in ventilation during positive end-expiratory pressure

We read with interest the commentary ‘Can heterogeneity in ventilation be good’ [1] and the related article by Zhao and colleagues [2]. We agree with the comments that instead of incremental positive end-expiratory pressure (PEEP) levels, a decremented PEEP titration might be an attractive option for determining optimal PEEP [1,3]. However, we feel that physiological inhomogeneity in ventilation and perfusion related to the gravitational eff ect in normal lungs occurs during spontaneous breathing, and during spontaneous breathing a negative alveolar pressure develops during inspiration and facilitates pulmonary blood fl ow. Contrary to when applying PEEP, the positive pressure remains throughout respira tion and paradoxically aff ects the pulmonary fl ow. We feel that it would be wiser not to compare the physiological inhomogeneity in ventilation with PEEPrelated inhomo genous ventilation. PEEP is a slow recruitment technique for aerating collapsed alveoli, which can happen in a non-uniform fashion. Hence, anticipating any good eff ect of inhomogeneity of ventilation during PEEP may give a false impression to physicians regarding mechanically ventilated patients in the ICU. Respiratory parameters such as lung mechanics and arterial blood gas refl ect global ventilation. Th e readily available bedside chest X-ray is useful to map the inhomogeneity of the alveolar recruitment during PEEP in acute respiratory distress syndrome patients. Th e lung infi ltration score for the diff erent lung zones can map heterogeneity in lung recruitment [4]. Th is heterogeneity between the two lungs (lung infi ltration score diff erence ≥3) was associated with postural hypoxemia when the worst lung was down in the lateral position and predisposed to skin sores on the worst lung side [4]. We opine that lung changes comprise a dynamic process in the ICU. Any PEEP level that is appropriate at one point of time may be required to be reevaluated at a later time or, for that matter, even after chest physiotherapy. Understandably, there cannot be a single ideal PEEP level that satisfi es all clinical objectives and situations.

Break Through Inspiration During IPPV is Seen as “Curare Crest" in Sevograph

Background: The break through spontaneous effort in anaesthetized and ventilated patients is seen as ‘curarecleft’ during expiratory plateau phase of the capnography. At the open position of the sevoflurane vaporizer, the sevograph displays a mirror image graph to the capnograph. We studied the sevograph changes corresponding to ‘curare-cleft’ in capnography. Methods: We have observed that during break through spontaneous breaths the sevograph complemented ‘curare-crest’ corresponding to ‘curare-cleft’ in six patients. In second part of study 25 consenting adult patients coming for surgery were given general anaesthesia using fentanyl, propofol and suxamethonium. After tracheal intubation, controlled ventilation was started under sevoflurane anaesthesia. We allowed the onset of spontaneous effort and observed for the onset time to ‘curare-cleft’ in capnograph, ‘curare-crest’ in sevograph, visible negative deflection of the needle in airway pressure gauge till negative airway pressure of 5 cm H2O. The onset time for the both changes were statistically analysed for agreement analysis using Blend and Altman test. Results: ‘Curare-crest’ in sevograph was visible at the same breath in majority (76%) of instances along with that of ‘curare-cleft’ in capnograph. Both appeared in respective graphs significantly earlier than the negative deflection of airway gauge needle by 5 cm H2O and disappeared after vecuronium. Onset time for both ‘curare-cleft’ in capnograph and ‘curare-crest’ in sevograph had significant (p<0.01) correlation (R=0.97) too. Conclusions: The authors feel that both changes ‘curare-crest’ in sevograph complemented ‘curare-cleft’ in capnograph and can be equivocally used as warning signal for lighter planes of anesthesia or diminishing effect of muscle relaxant.