446 Correspondence
Acknowledgements relating to this article Assistance with the audit: none. Financial support and sponsorship: none. Conflicts of interest: none.
References 1
Miller KA, Harkin CP, Bailey PL. Postoperative tracheal extubation. Anesth Analg 1995; 80:149–172. 2 Cook TM, Woodall N, Frerk C, Fourth National Audit Project. Major complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1: anaesthesia. Br J Anaesth 2011; 106:617– 631. 3 Spivey M, Phillips J. Airway problems. In: Colvin J, Peden C, editors. Raising the standard: a compendium of audit recipes. 3rd ed. London: RCOA; 2012. pp. 116–117. 4 Loadsman JA, Hillman DR. Anaesthesia and sleep apnoea. Br J Anaesth 2001; 86:254–266. 5 Visvanathan T, Kluger MT, Webb RK, Westhorpe RN. Crisis management during anaesthesia: laryngospasm. Qual Saf Healthcare 2005; 14:e3. 6 Australian and New Zealand College of Anaesthetists. PS04. Recommendations for the post anaesthesia recovery room Australian and New Zealand College of Anaesthetists Melbourne, Australia. 2006. http:// www.anzca.edu.au/resources/professional-documents. 7 Nze PU. A five- year review of upper airway obstruction in the immediate general anaesthetic post operative period in Enugu, Nigeria, 1990–1994. West Afr J Med 2006; 25:266–268. 8 Hines R, Barash PG, Watrous G, O’Connor T. Complications occurring in the postanesthesia care unit: a survey. Anesth Analg 1992; 74:503–509. 9 Parr SM, Robinson BJ, Glover PW, Galletly DC. Level of consciousness on arrival in the recovery room and the development of early respiratory morbidity. Anaesth Intensive Care 1991; 19:369–372. 10 Sinclair DR, Chung F, Mezei G. Can postoperative nausea and vomiting be predicted? Anesthesiology 1999; 91:109–118. DOI:10.1097/EJA.0000000000000227
Bag-mask ventilation in rapid sequence induction A survey of current practice among members of the UK Difficult Airway Society James P.R. Brown and Gavin C. Werrett From the BC Women’s Hospital, Vancouver, British Columbia, Canada (JPRB), and Derriford Hospital, Plymouth, UK (GCW)
preexisting respiratory disease, for example pneumonia; and those intolerant of a close-fitting mask, for example the distressed child. We hypothesised that expert operators modify their RSI technique, balancing risks of pulmonary aspiration with other considerations, frequently using BMV in patients at risk of hypoxaemia. We would like to report the results from a SurveyMonkey questionnaire of members of the UK Difficult Airways Society (DAS). Clinicians were given five scenarios: (1) Appendicectomy, BMI 50 (2) Healthy 50-year-old, with pneumonia and hypoxic respiratory failure (3) Stat caesarean section, parturient BMI 35 (4) Severe head injury (5) Six-year-old, emergency laparotomy Respondents were asked if they would undergo BMV after anaesthetic induction and prior to endotracheal intubation. Responses were analysed according to respondent level of training, and which regular clinical sessions they performed (critical care sessions, emergency operating, obstetric or paediatric lists). Eight hundred and twenty-four responses were received (24% registrars, 69% consultants, response rate 36%). Nine percent would always or frequently undergo BMV during RSI, and a further 67% would undergo BMV depending on the scenario (Fig. 1). Some clinicians who stated that they would never undertake BMV during RSI then considered BMV when presented with specific scenarios: 7% for scenario A, 46% for B, 5% for C, 3% for D and 33% for E. Clinicians were most likely to undergo BMV in the pneumonia (83%) and paediatric (60%) scenarios. Consultants were more likely to undertake BMV than junior trainees (Table 1), odds ratio (OR) 2.2 [95% confidence interval (95% CI) 1.5 to 3.4: P ¼ 0.00006]. Clinicians undertaking regular paediatric sessions were more likely to undertake BMV in all scenarios, not just the paediatric scenario [Table 2; OR Fig. 1
Correspondence to Dr James P.R. Brown, Department of Anesthesia, BC Women’s Hospital, 4500, Oak Street, Vancovuer, BC. V6H 3V5 Canada E-mail: [email protected] Published online 22 April 2015
Never (25%)
Editor,
Occasionally, if the clinical situation dictates (67%)
Traditional teaching dictates that bag-mask ventilation (BMV) is not recommended during rapid sequence induction (RSI) due to the concern of insufflating the stomach, precipitating reflux of gastric contents and potentially pulmonary aspiration. However, there are patient groups at risk of pulmonary aspiration who are challenging to preoxygenate. These include those with decreased functional residual capacity, for example the morbidly obese, or the term parturient; those with
Frequently (6%) Always (3%)
Pie-chart demonstrating responses to how frequently do you bag mask ventilate as part of a rapid sequence induction (n ¼ 813).
Eur J Anaesthesiol 2015; 32:439–450 Copyright © European Society of Anaesthesiology. Unauthorized reproduction of this article is prohibited.
Correspondence
Table 1
447
Respondents who would bag-mask ventilate in each scenario, analysed by grade of anaesthetist
ST4-7
Grade SAS
Consultant
Total
p value
167 (40) 26% (125) 82% (12) 8% (23) 15% (85) 56%
61 (18) 39% (35) 76% (15) 32% (13) 28% (23) 52%
563 (173) 39% (371) 84% (86) 20% (119) 27% (278) 63%
821 (235) 35% (552) 83% (116) 17% (156) 23% (396) 60%
0.004 0.4 0.0005 0.004 0.1
ST1-3 M
n¼ Appendicectomy BMI 50 Pneumonia with hypoxia Emergency caesarean Traumatic head injury Paediatric laparotomy
30 (3) 12% (19) 76% (2) 8% (1) 4% (10) 42%
Statistical testing with Fisher’s exact test with Holm correction. BMI, body mass index; SAS, staff grade and associate specialist; ST, speciality training/anaesthetics registrar.
1.4 (95% CI 1.2 to 1.6: P ¼ 0.00003)]. No significant difference was demonstrated when responses were analysed by whether or not clinicians regularly performed clinical sessions other than paediatric lists. Hunter (1776) was the first to observe the benefit of cricoid pressure in preventing gastric insufflation in recovery of ‘people apparently drowned’. The ‘larynx gently pressed against the oesophagus and spine’ prevents ‘stomach and intestines being too much distended by air’. Opposing views of whether to undertake BMV as part of RSI were first presented in the 1960s: Sellick (1961) stated that, with cricoid pressure, ‘lungs may be ventilated without the risk of gastric distension’, whereas Wylie (1963) put forward the alternate position: ‘inflation of the patient’s lungs . . . must not be carried out until endotracheal intubation’. Neither presented evidence to support their statements. Available evidence suggests that BMV, especially with cricoid pressure, is unlikely to cause significant gastric insufflation. In elective surgery, Lawes et al.1 demonstrated that, with cricoid pressure applied, gastric insufflation did not occur, even with airway pressures of up to 60 cmH20. Ruben et al.2 found that with cricoid pressure, airway pressures of more than 50 cmH2O were required to cause insufflation. Petito investigated the volume of gas in the stomach of patients ventilated with cricoid pressure (15 ml kg1): 92% were found to have less than 15 ml, and two patients who suffered stomach insufflation (355 and 500 ml) were noted to require ‘higher than usual inspiratory pressure . . . to deliver . . . 15 ml kg1. A cadaveric study demonstrated that 30 N cricoid pressure prevented regurgitation with oesophageal pressures up to 55 cmH2O.3
Respondents who would bag-mask ventilate in each scenario: those undertaking regular paediatric lists compared with those not undertaking regular paediatric lists
Table 2
Regular sessions Paediatrics No paediatrics n¼ Appendicectomy BMI 50 Pneumonia with hypoxia Emergency caesarean Traumatic head injury Paediatric laparotomy
M
298 (108) 42% (218) 86% (57) 23% (67) 26% (170) 66%
517 (126) 31% (332) 81% (58) 14% (87) 22% (223) 56%
p value 0.02 0.3 0.045 0.3 0.045
Statistical testing with Fisher’s exact test with Holm correction. BMI, body mass index.
Pulmonary aspiration was the commonest cause of death associated with anaesthesia in cases reported to the fourth UK National Audit Project (NAP 4).4 The majority of these were in cases in which risk factors for regurgitation were not identified, and RSI not undertaken, or they occurred intraoperatively in cases managed with a nondefinitive airway. Aspiration when RSI was undertaken was relatively rare; only two cases were reported in NAP 4, one in a patient with small bowel obstruction and another in an obstetric case following difficult intubation. A meta-analysis of the available literature on RSI concluded that ‘there is no evidence to support the avoidance of BMV. . . to decrease the incidence of aspiration (Grade B recommendation)’ and ‘keeping peak airway pressures below 15–20 cmH2O will allow for ventilation without increasing the risk of air entry into the stomach (Grade C recommendation)’.5 Some respondents suggested BMV in response to desaturation, as an alternative to routine BMV during RSI. A randomised simulation study comparing the two strategies demonstrated that those responding to desaturation were more likely to use higher pressures to BMV (>20 cmH2O), and more likely to attempt intubation before allowing adequate time for paralysis; in addition, operators had significantly elevated stress hormones compared with the group who electively used BMV.6 BMV after desaturation places patients at a greater risk of gastric insufflation, coughing and bucking (predictors of regurgitation) and raises operator stress (shown to reduce situational awareness). In light of the increased awareness of human factors in managing critical incidents, in our opinion, there is a potential advantage of performing at least one ‘gentle puff’ in all patientsundergoingRSI.Thiswill reassuretheanaesthetist that they are able to undergo BMV in the event of a difficult or failed intubation; the incidence of both of these is increased with RSI. Once the ability to BMV is confirmed, the operator can feel reassured and concentrate on securing the airway, improving performance. Similarly, if the practitioner was unable to perform BMV at this stage, it would prompt them to call for help earlier when faced with a ‘Can’t Intubate, Can’t Ventilate’ scenario. Many patient groups are at risk of hypoxaemia during RSI and would benefit from BMV. Where there is no higher
Eur J Anaesthesiol 2015; 32:439–450 Copyright © European Society of Anaesthesiology. Unauthorized reproduction of this article is prohibited.
448 Correspondence
level of evidence available, consensus opinion of experts is used as a basis for practice guidelines. Trainees are more likely to use ‘classical RSI’, as prescriptively taught. Is it time to review specific teaching of RSI technique in selected groups, reflecting current expert practice?
Acknowledgements relating to this article Assistance with the survey: we would like to thank all the DAS members who took the time to complete the survey. Thanks also to Andrew Bailey, Peninsula Medical School, for his assistance with the statistical analysis. Financial support and sponsorship: no external funding received. Conflicts of interest: none.
References 1 2 3 4
5
6
Lawes EG, Campbell I, Mercer D. Inflation pressure, gastric insufflation and rapid sequence induction. Br J Anaesth 1987; 59:315–318. Ruben H, Krudsen E, Carugati G. Gastric insufflation in relation to airway pressure. Acta Anaesthesiol Scand 1961; 5:107–114. Vanner RG, Pryle BJ. Regurgitation and oesophageal rupture with cricoid pressure: a cadaver study. Anaesthesia 1992; 47:732–735. Cook T, Woodall N, Frerk C. The Fourth National Audit Project. Major complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1: anaesthesia. Br J Anaesth 2011; 106:617–631. Neilipovitz DT, Crosby ET. No evidence for decreased incidence of aspiration after rapid sequence induction. Can J Anaesth 2007; 54:748– 764. Eich C, Timmermann A, Russo SG, et al. A controlled rapid-sequence induction technique for infants may reduce unsafe actions and stress. Acta Anaesthesiol Scand 2009; 53:1167–1172. DOI:10.1097/EJA.0000000000000262
Hyperostosis frontalis interna as a potential source of cerebral oximetry signal interference A case report Tina L. Doshi, Ivan Kangrga and Andrea Vannucci From the Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri, USA (TLD, IK, AV) Correspondence to Andrea Vannucci, MD, DEAA, Department of Anesthesiology, Washington University School of Medicine, Campus Box 8054, 660 South Euclid Avenue, St. Louis, MO 63110-1093, USA Tel: +1 314 362 2365; fax: +1 314 362 1185; e-mail: [email protected] Published online 22 April 2015
Editor, Cerebral oximetry is a noninvasive monitoring technique that uses near-infrared spectroscopy (NIRS) to measure tissue oxygenation in the brain (rSO2), providing an estimate of cerebral perfusion. However, variations in oximeter design, use of systemic vasoconstrictors and underlying skin pigmentation have all been cited as factors that may affect the accuracy of cerebral oximetry readings.1–3 A few authors have suggested that deeper anatomical structures, such as the skull and the frontal
sinus, may also play a role, but this hypothesis remains speculative. We suggest that the presence of hyperostosis frontalis interna (HFI) may interfere with cerebral oximeter accuracy. This case report is exempt from institutional review board (IRB) evaluation following an official review from the Washington University Human Resources Protection Office dated 11 February 2015. A 74-year-old woman was scheduled for left carotid pseudo-aneurysm repair. Prior to induction, a Somanetics INVOS 5100C cerebral oximeter (Troy, Michigan, USA) was connected to the patient’s forehead. Although she was awake and neurologically intact, initial bilateral rSO2 was 30 to 40% (normal range 60 to 80%), despite multiple adjustments in probe position (Fig. 1). These values improved only slightly after preoxygenation and induction of general anaesthesia, which proceeded uneventfully. Shortly after induction, the mean arterial pressure (MAP) decreased to 55 mmHg, and a phenylephrine infusion was titrated to maintain the MAP between 75 and 115 mmHg (baseline 80 mmHg) for the duration of the operation. Throughout this time, the cerebral oximeter not only continued to show bilateral values below normal but also still well above the preinduction baseline. Following carotid cross-clamp, there was a 25% decrease in rSO2 on the operative side, prompting immediate insertion of a carotid shunt. The rSO2 then improved to above baseline values, but the readings on the operative side were approximately 10% lower than on the nonoperative side. Oximeter readings on the operative side dropped briefly once more when the first shunt was replaced by a different type of shunt required to facilitate the surgical repair. The readings were again immediately restored to levels below the preclamping values but above the preinduction baseline. Upon removal of the crossclamp, bilateral readings returned to baseline. After completion of the surgery, the patient emerged from general anaesthesia, followed commands with motor strength intact and was successfully extubated. She was then transferred to the postanaesthesia care unit in a stable condition. Several hours later, the patient experienced an expressive aphasia. A computed tomographic (CT) scan of the head showed evidence of a new left middle cerebral artery stroke. The patient was admitted to the neurological ICU for postoperative care, where her symptoms gradually improved. She was eventually discharged to a skilled nursing facility and then lost to follow-up. Search of public records show that the patient has since died. The precise timing and cause of this patient’s stroke is unclear, but it is not our goal to explain the patient’s ischaemic event. Rather, our primary objective is to review the possible causes of the low intraoperative rSO2 readings observed and to discuss factors that can influence the detection of decreased cerebral oxygenation in this and other patients monitored with cerebral oximetry.
Eur J Anaesthesiol 2015; 32:439–450 Copyright © European Society of Anaesthesiology. Unauthorized reproduction of this article is prohibited.
Acknowledgements relating to this article Assistance with the audit: none. Financial support and sponsorship: none. Conflicts of interest: none.
References 1
Miller KA, Harkin CP, Bailey PL. Postoperative tracheal extubation. Anesth Analg 1995; 80:149–172. 2 Cook TM, Woodall N, Frerk C, Fourth National Audit Project. Major complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1: anaesthesia. Br J Anaesth 2011; 106:617– 631. 3 Spivey M, Phillips J. Airway problems. In: Colvin J, Peden C, editors. Raising the standard: a compendium of audit recipes. 3rd ed. London: RCOA; 2012. pp. 116–117. 4 Loadsman JA, Hillman DR. Anaesthesia and sleep apnoea. Br J Anaesth 2001; 86:254–266. 5 Visvanathan T, Kluger MT, Webb RK, Westhorpe RN. Crisis management during anaesthesia: laryngospasm. Qual Saf Healthcare 2005; 14:e3. 6 Australian and New Zealand College of Anaesthetists. PS04. Recommendations for the post anaesthesia recovery room Australian and New Zealand College of Anaesthetists Melbourne, Australia. 2006. http:// www.anzca.edu.au/resources/professional-documents. 7 Nze PU. A five- year review of upper airway obstruction in the immediate general anaesthetic post operative period in Enugu, Nigeria, 1990–1994. West Afr J Med 2006; 25:266–268. 8 Hines R, Barash PG, Watrous G, O’Connor T. Complications occurring in the postanesthesia care unit: a survey. Anesth Analg 1992; 74:503–509. 9 Parr SM, Robinson BJ, Glover PW, Galletly DC. Level of consciousness on arrival in the recovery room and the development of early respiratory morbidity. Anaesth Intensive Care 1991; 19:369–372. 10 Sinclair DR, Chung F, Mezei G. Can postoperative nausea and vomiting be predicted? Anesthesiology 1999; 91:109–118. DOI:10.1097/EJA.0000000000000227
Bag-mask ventilation in rapid sequence induction A survey of current practice among members of the UK Difficult Airway Society James P.R. Brown and Gavin C. Werrett From the BC Women’s Hospital, Vancouver, British Columbia, Canada (JPRB), and Derriford Hospital, Plymouth, UK (GCW)
preexisting respiratory disease, for example pneumonia; and those intolerant of a close-fitting mask, for example the distressed child. We hypothesised that expert operators modify their RSI technique, balancing risks of pulmonary aspiration with other considerations, frequently using BMV in patients at risk of hypoxaemia. We would like to report the results from a SurveyMonkey questionnaire of members of the UK Difficult Airways Society (DAS). Clinicians were given five scenarios: (1) Appendicectomy, BMI 50 (2) Healthy 50-year-old, with pneumonia and hypoxic respiratory failure (3) Stat caesarean section, parturient BMI 35 (4) Severe head injury (5) Six-year-old, emergency laparotomy Respondents were asked if they would undergo BMV after anaesthetic induction and prior to endotracheal intubation. Responses were analysed according to respondent level of training, and which regular clinical sessions they performed (critical care sessions, emergency operating, obstetric or paediatric lists). Eight hundred and twenty-four responses were received (24% registrars, 69% consultants, response rate 36%). Nine percent would always or frequently undergo BMV during RSI, and a further 67% would undergo BMV depending on the scenario (Fig. 1). Some clinicians who stated that they would never undertake BMV during RSI then considered BMV when presented with specific scenarios: 7% for scenario A, 46% for B, 5% for C, 3% for D and 33% for E. Clinicians were most likely to undergo BMV in the pneumonia (83%) and paediatric (60%) scenarios. Consultants were more likely to undertake BMV than junior trainees (Table 1), odds ratio (OR) 2.2 [95% confidence interval (95% CI) 1.5 to 3.4: P ¼ 0.00006]. Clinicians undertaking regular paediatric sessions were more likely to undertake BMV in all scenarios, not just the paediatric scenario [Table 2; OR Fig. 1
Correspondence to Dr James P.R. Brown, Department of Anesthesia, BC Women’s Hospital, 4500, Oak Street, Vancovuer, BC. V6H 3V5 Canada E-mail: [email protected] Published online 22 April 2015
Never (25%)
Editor,
Occasionally, if the clinical situation dictates (67%)
Traditional teaching dictates that bag-mask ventilation (BMV) is not recommended during rapid sequence induction (RSI) due to the concern of insufflating the stomach, precipitating reflux of gastric contents and potentially pulmonary aspiration. However, there are patient groups at risk of pulmonary aspiration who are challenging to preoxygenate. These include those with decreased functional residual capacity, for example the morbidly obese, or the term parturient; those with
Frequently (6%) Always (3%)
Pie-chart demonstrating responses to how frequently do you bag mask ventilate as part of a rapid sequence induction (n ¼ 813).
Eur J Anaesthesiol 2015; 32:439–450 Copyright © European Society of Anaesthesiology. Unauthorized reproduction of this article is prohibited.
Correspondence
Table 1
447
Respondents who would bag-mask ventilate in each scenario, analysed by grade of anaesthetist
ST4-7
Grade SAS
Consultant
Total
p value
167 (40) 26% (125) 82% (12) 8% (23) 15% (85) 56%
61 (18) 39% (35) 76% (15) 32% (13) 28% (23) 52%
563 (173) 39% (371) 84% (86) 20% (119) 27% (278) 63%
821 (235) 35% (552) 83% (116) 17% (156) 23% (396) 60%
0.004 0.4 0.0005 0.004 0.1
ST1-3 M
n¼ Appendicectomy BMI 50 Pneumonia with hypoxia Emergency caesarean Traumatic head injury Paediatric laparotomy
30 (3) 12% (19) 76% (2) 8% (1) 4% (10) 42%
Statistical testing with Fisher’s exact test with Holm correction. BMI, body mass index; SAS, staff grade and associate specialist; ST, speciality training/anaesthetics registrar.
1.4 (95% CI 1.2 to 1.6: P ¼ 0.00003)]. No significant difference was demonstrated when responses were analysed by whether or not clinicians regularly performed clinical sessions other than paediatric lists. Hunter (1776) was the first to observe the benefit of cricoid pressure in preventing gastric insufflation in recovery of ‘people apparently drowned’. The ‘larynx gently pressed against the oesophagus and spine’ prevents ‘stomach and intestines being too much distended by air’. Opposing views of whether to undertake BMV as part of RSI were first presented in the 1960s: Sellick (1961) stated that, with cricoid pressure, ‘lungs may be ventilated without the risk of gastric distension’, whereas Wylie (1963) put forward the alternate position: ‘inflation of the patient’s lungs . . . must not be carried out until endotracheal intubation’. Neither presented evidence to support their statements. Available evidence suggests that BMV, especially with cricoid pressure, is unlikely to cause significant gastric insufflation. In elective surgery, Lawes et al.1 demonstrated that, with cricoid pressure applied, gastric insufflation did not occur, even with airway pressures of up to 60 cmH20. Ruben et al.2 found that with cricoid pressure, airway pressures of more than 50 cmH2O were required to cause insufflation. Petito investigated the volume of gas in the stomach of patients ventilated with cricoid pressure (15 ml kg1): 92% were found to have less than 15 ml, and two patients who suffered stomach insufflation (355 and 500 ml) were noted to require ‘higher than usual inspiratory pressure . . . to deliver . . . 15 ml kg1. A cadaveric study demonstrated that 30 N cricoid pressure prevented regurgitation with oesophageal pressures up to 55 cmH2O.3
Respondents who would bag-mask ventilate in each scenario: those undertaking regular paediatric lists compared with those not undertaking regular paediatric lists
Table 2
Regular sessions Paediatrics No paediatrics n¼ Appendicectomy BMI 50 Pneumonia with hypoxia Emergency caesarean Traumatic head injury Paediatric laparotomy
M
298 (108) 42% (218) 86% (57) 23% (67) 26% (170) 66%
517 (126) 31% (332) 81% (58) 14% (87) 22% (223) 56%
p value 0.02 0.3 0.045 0.3 0.045
Statistical testing with Fisher’s exact test with Holm correction. BMI, body mass index.
Pulmonary aspiration was the commonest cause of death associated with anaesthesia in cases reported to the fourth UK National Audit Project (NAP 4).4 The majority of these were in cases in which risk factors for regurgitation were not identified, and RSI not undertaken, or they occurred intraoperatively in cases managed with a nondefinitive airway. Aspiration when RSI was undertaken was relatively rare; only two cases were reported in NAP 4, one in a patient with small bowel obstruction and another in an obstetric case following difficult intubation. A meta-analysis of the available literature on RSI concluded that ‘there is no evidence to support the avoidance of BMV. . . to decrease the incidence of aspiration (Grade B recommendation)’ and ‘keeping peak airway pressures below 15–20 cmH2O will allow for ventilation without increasing the risk of air entry into the stomach (Grade C recommendation)’.5 Some respondents suggested BMV in response to desaturation, as an alternative to routine BMV during RSI. A randomised simulation study comparing the two strategies demonstrated that those responding to desaturation were more likely to use higher pressures to BMV (>20 cmH2O), and more likely to attempt intubation before allowing adequate time for paralysis; in addition, operators had significantly elevated stress hormones compared with the group who electively used BMV.6 BMV after desaturation places patients at a greater risk of gastric insufflation, coughing and bucking (predictors of regurgitation) and raises operator stress (shown to reduce situational awareness). In light of the increased awareness of human factors in managing critical incidents, in our opinion, there is a potential advantage of performing at least one ‘gentle puff’ in all patientsundergoingRSI.Thiswill reassuretheanaesthetist that they are able to undergo BMV in the event of a difficult or failed intubation; the incidence of both of these is increased with RSI. Once the ability to BMV is confirmed, the operator can feel reassured and concentrate on securing the airway, improving performance. Similarly, if the practitioner was unable to perform BMV at this stage, it would prompt them to call for help earlier when faced with a ‘Can’t Intubate, Can’t Ventilate’ scenario. Many patient groups are at risk of hypoxaemia during RSI and would benefit from BMV. Where there is no higher
Eur J Anaesthesiol 2015; 32:439–450 Copyright © European Society of Anaesthesiology. Unauthorized reproduction of this article is prohibited.
448 Correspondence
level of evidence available, consensus opinion of experts is used as a basis for practice guidelines. Trainees are more likely to use ‘classical RSI’, as prescriptively taught. Is it time to review specific teaching of RSI technique in selected groups, reflecting current expert practice?
Acknowledgements relating to this article Assistance with the survey: we would like to thank all the DAS members who took the time to complete the survey. Thanks also to Andrew Bailey, Peninsula Medical School, for his assistance with the statistical analysis. Financial support and sponsorship: no external funding received. Conflicts of interest: none.
References 1 2 3 4
5
6
Lawes EG, Campbell I, Mercer D. Inflation pressure, gastric insufflation and rapid sequence induction. Br J Anaesth 1987; 59:315–318. Ruben H, Krudsen E, Carugati G. Gastric insufflation in relation to airway pressure. Acta Anaesthesiol Scand 1961; 5:107–114. Vanner RG, Pryle BJ. Regurgitation and oesophageal rupture with cricoid pressure: a cadaver study. Anaesthesia 1992; 47:732–735. Cook T, Woodall N, Frerk C. The Fourth National Audit Project. Major complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1: anaesthesia. Br J Anaesth 2011; 106:617–631. Neilipovitz DT, Crosby ET. No evidence for decreased incidence of aspiration after rapid sequence induction. Can J Anaesth 2007; 54:748– 764. Eich C, Timmermann A, Russo SG, et al. A controlled rapid-sequence induction technique for infants may reduce unsafe actions and stress. Acta Anaesthesiol Scand 2009; 53:1167–1172. DOI:10.1097/EJA.0000000000000262
Hyperostosis frontalis interna as a potential source of cerebral oximetry signal interference A case report Tina L. Doshi, Ivan Kangrga and Andrea Vannucci From the Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri, USA (TLD, IK, AV) Correspondence to Andrea Vannucci, MD, DEAA, Department of Anesthesiology, Washington University School of Medicine, Campus Box 8054, 660 South Euclid Avenue, St. Louis, MO 63110-1093, USA Tel: +1 314 362 2365; fax: +1 314 362 1185; e-mail: [email protected] Published online 22 April 2015
Editor, Cerebral oximetry is a noninvasive monitoring technique that uses near-infrared spectroscopy (NIRS) to measure tissue oxygenation in the brain (rSO2), providing an estimate of cerebral perfusion. However, variations in oximeter design, use of systemic vasoconstrictors and underlying skin pigmentation have all been cited as factors that may affect the accuracy of cerebral oximetry readings.1–3 A few authors have suggested that deeper anatomical structures, such as the skull and the frontal
sinus, may also play a role, but this hypothesis remains speculative. We suggest that the presence of hyperostosis frontalis interna (HFI) may interfere with cerebral oximeter accuracy. This case report is exempt from institutional review board (IRB) evaluation following an official review from the Washington University Human Resources Protection Office dated 11 February 2015. A 74-year-old woman was scheduled for left carotid pseudo-aneurysm repair. Prior to induction, a Somanetics INVOS 5100C cerebral oximeter (Troy, Michigan, USA) was connected to the patient’s forehead. Although she was awake and neurologically intact, initial bilateral rSO2 was 30 to 40% (normal range 60 to 80%), despite multiple adjustments in probe position (Fig. 1). These values improved only slightly after preoxygenation and induction of general anaesthesia, which proceeded uneventfully. Shortly after induction, the mean arterial pressure (MAP) decreased to 55 mmHg, and a phenylephrine infusion was titrated to maintain the MAP between 75 and 115 mmHg (baseline 80 mmHg) for the duration of the operation. Throughout this time, the cerebral oximeter not only continued to show bilateral values below normal but also still well above the preinduction baseline. Following carotid cross-clamp, there was a 25% decrease in rSO2 on the operative side, prompting immediate insertion of a carotid shunt. The rSO2 then improved to above baseline values, but the readings on the operative side were approximately 10% lower than on the nonoperative side. Oximeter readings on the operative side dropped briefly once more when the first shunt was replaced by a different type of shunt required to facilitate the surgical repair. The readings were again immediately restored to levels below the preclamping values but above the preinduction baseline. Upon removal of the crossclamp, bilateral readings returned to baseline. After completion of the surgery, the patient emerged from general anaesthesia, followed commands with motor strength intact and was successfully extubated. She was then transferred to the postanaesthesia care unit in a stable condition. Several hours later, the patient experienced an expressive aphasia. A computed tomographic (CT) scan of the head showed evidence of a new left middle cerebral artery stroke. The patient was admitted to the neurological ICU for postoperative care, where her symptoms gradually improved. She was eventually discharged to a skilled nursing facility and then lost to follow-up. Search of public records show that the patient has since died. The precise timing and cause of this patient’s stroke is unclear, but it is not our goal to explain the patient’s ischaemic event. Rather, our primary objective is to review the possible causes of the low intraoperative rSO2 readings observed and to discuss factors that can influence the detection of decreased cerebral oxygenation in this and other patients monitored with cerebral oximetry.
Eur J Anaesthesiol 2015; 32:439–450 Copyright © European Society of Anaesthesiology. Unauthorized reproduction of this article is prohibited.
