BJA P-G. Guinot* J. Godart B. de Broca E. Bernard E. Lorne H. Dupont Amiens, France *E-mail: [email protected]

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17 Jin X, Weil MH, Tang W, et al. End-tidal carbon dioxide as a noninvasive indicator of cardiac index during circulatory shock. Crit Care Med 2000; 28: 2415– 9

doi:10.1093/bja/aeu431

Hazards of bone cement: for patient and operating theatre personnel Editor—We read with great interest the recent article by Schummer and colleagues,1 dealing with the administration of bone cement for vertebroplasty which may lead to pulmonary embolism and potentially devastating consequences if not treated correctly. This may also occur in patients having total knee/hip replacement. We would like to highlight several other less known, albeit dangerous hazards of bone cement. We believe that bone cement is a hazardous mixture when applied to bone fractures and metal prosthesis implants. The cement is dangerous to the patient, but may also be hazardous to the personnel in the room.2 3 These dangers should also be known to anaesthetists. Bone cement, when mixed before application, gives off a very pungent smell and cloud of fumes that operating theatre personnel near the operating table may inhale. This inhalation over time can lead to the nervous system side-effects (causing symptoms similar to drunkenness) with headache, drowsiness, nausea, weakness, fatigue, irritability, dizziness, and loss of appetite. Most people will not experience these nervous system side-effects without first experiencing local irritation to the skin, eyes, nose, or throat. Methyl methacrylate (MMA) vapour at a level of 125 ppm (just above Cal-OSHA’s Permissible Exposure limit) may cause teary eyes, sore throat, coughing, and irritation of the nose. In animal studies, prolonged exposure to 400 ppm damaged the surface of the trachea. It is not known whether this occurs in humans. Moreover, direct skin contact with MMA can cause itching, burning, redness, swelling, and cracking of the skin. Repeated skin contact can cause dermatitis. In some people, an allergic skin reaction can occur. There are reports that prolonged skin contact may cause tingling, numbness, and whitening of the fingers. MMA easily penetrates most ordinary clothing and can also penetrate surgical gloves. Some studies have suggested that MMA can cause birth defects when pregnant animals are exposed to extremely high levels. It is not known whether MMA can affect pregnancy in humans. However, MMA inhaled by a pregnant woman can reach the fetus and women who may be pregnant should avoid overexposure to MMA. Operating theatres should be well ventilated with a laminar flow system to take care of the cement odour and fumes. Rooms can also be constructed with a glass wall partition to separate the operating theatre table and the patient from the operating theatre nurse and other personnel.

Declaration of interest None declared.

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1 Guinot PG, Godart J, de Broca B, Bernard E, Lorne E, Dupont H. End-expiratory occlusion manoeuvre does not accurately predict fluid responsiveness in the operating theatre. Br J Anaesth 2014; 112: 1050–4 2 Valtier B, Cholley BP, Belot JP, de la Coussaye JE, Mateo J, Payen DM. Noninvasive monitoring of cardiac output in critically ill patients using transesophageal Doppler. Am J Respir Crit Care Med 1998; 158: 77– 83 3 Roeck M, Jakob SM, Boehlen T, Brander L, Knuesel R, Takala J. Change in stroke volume in response to fluid challenge: assessment using esophageal Doppler. Intensive Care Med 2003; 29: 1729– 35 4 Kim K, Kwok I, Chang H, Han T. Comparison of cardiac outputs of major burn patients undergoing extensive early escharectomy: esophageal Doppler monitor versus thermodilution pulmonary artery catheter. J Trauma 2004; 57: 1013– 7 5 Gan TJ, Soppitt A, Maroof M, et al. Goal-directed intraoperative fluid administration reduces length of hospital stay after major surgery. Anesthesiology 2002; 97: 820– 6 6 Dark PM, Singer M. The validity of trans-esophageal Doppler ultrasonography as a measure of cardiac output in critically ill adults. Intensive Care Med 2004; 30: 2060–6 7 Monnet X, Chemla D, Osman D, et al. Measuring aortic diameter improves accuracy of esophageal Doppler in assessing fluid responsiveness. Crit Care Med 2007; 35: 477– 82 8 Schober P, Loer SA, Schwarte LA. Perioperative hemodynamic monitoring with transesophageal Doppler technology. Anesth Analg 2009; 109: 340– 53 9 Cariou A, Monchi M, Joly LM, et al. Noninvasive cardiac output monitoring by aortic blood flow determination: evaluation of the Sometec Dynemo-3000 system. Crit Care Med 1998; 26: 2066– 72 10 Singer M. ODM/CardioQ esophageal Doppler technology. Crit Care Med 2003; 31: 1888– 9 11 Leather HA, Wouters PF. Oesophageal Doppler monitoring overestimates cardiac output during lumbar epidural anaesthesia. Br J Anaesth 2001; 86: 794–7 12 Weil G, Suria S, Monnet X. Prediction de la reponse au remplissage par un test de pause tele-expiratoire pendant une chirurgie abdominale. Ann Fr Anesth Reanim 2013; 32(Suppl. 1): A287 13 Frumin J, Epstein RM, Cohen G. Apneic oxygenation in man. Anesthesiology 1954; 20: 789– 98 14 Young A, Marik PE, Sibole S, Grooms D, Levitov A. Changes in end tidal carbon dioxide and volumetric carbon dioxide as predictors of volume responsiveness in hemodynamically unstable patients. J Cardiothorac Vasc Anesth 2013; 27: 681– 4 15 Monnet X, Bataille A, Magalhaes E, et al. End-tidal carbon dioxide is better than arterial pressure for predicting volume responsiveness by the passive leg raising test. Intensive Care Med 2013; 39: 93 – 100 16 Guzman JA, Lacoma FJ, Najar A, Kruse JA. End-tidal partial pressure of carbon dioxide as a noninvasive indicator of systemic oxygen supply dependency during hemorrhagic shock and resuscitation. Shock 1997; 8: 427–31

Correspondence

BJA

Correspondence

S. A. Bahlool London, UK E-mail: [email protected]

C. Kakazu* M. Lippmann A. Karnwal Torrance, USA *E-mail: [email protected] 1 Schummer W, Schlonski O, Breuer M. Bone cement embolism attached to central venous catheter. Br J Anaesth 2014; 112: 672–4 2 Leggat PA, Smith DR, Kedjarune U. Surgical applications of methyl methacrylate: a review of toxicity. Arch Environ Occup Health 2009; 64: 207– 12. doi: 10.1080/19338240903241291 3 Scolnick B, Collins J. Systemic reaction to methylmethacrylate in an operating room nurse. J Occup Med 1986; 28: 196– 8

Respiratory stroke volume variation and fluid responsiveness: how applicable is this? Editor—I would like to thank Guinot and colleagues1 for their nicely thought out and conducted study. Their study showed that delta respiratory stroke volume (SV) determined by oesophageal Doppler monitor is a highly sensitive and specific tool (impressive AUROC of 0.92) for predicting fluid responsiveness in pneumoperitoneum. I would like to ask two things about the methodology and applicability of the findings of this study. It would be interesting to find how much fluid in total these patients had in each group. It was clear from the results table that responders had a significantly lower cardiac output (CO) and SV with approximately the same arterial pressure at baseline. In the absence of hypotension or bleeding, I wonder what the trigger to give volume expansion was. In the very same issue of BJA, it has been mentioned that increasing the SV should be judged to be beneficial before volume expansion and not all ‘fluid responsive’ patients are necessarily hypovolaemic.2 Secondly, in this cohort of patients, the average respiratory system compliance (which I calculated as Vt divided by the plateau pressure minus the PEEP) was about 84, something we hardly ever see in anaesthesia for laparoscopic surgery. We well know that pneumoperitoneum significantly affects lung compliance (up to 50% reduction during pneumoperitoneum).3 This will further reduce with time as the ventilation demand increases by 10 – 25% to manage the hypercapnoea. Again in the BJA, we learnt how the validity of dynamic variables used to assess volume responsiveness becomes questionable when certain criteria are not met.4 One of the factors that significantly affects such validity is pulmonary system compliance. This will make me slightly sceptical about the applicability of these results in everyday practice.

Declaration of interest None declared.

doi:10.1093/bja/aeu427

Reply from the authors Editor—We would like to thank Dr Bahlool for his comments. We constructed the study1 to investigate the ability of respiratory variation of stroke volume (SV) to predict fluid responsiveness. For this purpose, we included patients for whom the physician had decided to infuse fluid. The reasons for fluid infusion were cardiac output (CO) optimization, haemorrhage, and arterial hypotension. In the case of CO optimization, fluid was infused when SV decrease was more than 10%. Unfortunately, we included the first fluid infusion and did not record the total of fluid infused during the surgery. We agree with the fact that fluid responsiveness is not synonymous with hypovolaemia. However, we believe that laparoscopy is a specific haemodynamic setting for which assessment of preload responsiveness may help the physician in the case of heart rate or arterial pressure changes. In this way, our objective was to test respiratory variation of SV as an indicator of fluid responsiveness. We agree with the fact that a high respiratory compliance may decrease the ability of respiratory derivate indicators.2 However, we calculated the average respiratory compliance that was 35 (8) ml cm H2O21. Equally, the mean respiratory compliance calculated from our data (mean tidal volume, pressure plateau, PEEP) was about 37 ml cm H2O21. These values are close to those observed in the operating theatre or intensive care unit, in which dynamic preload indicators have been demonstrated to predict fluid responsiveness.3 4

Declaration of interest None declared. P-G. Guinot* E. Lorne Amiens, France *E-mail: [email protected]

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doi:10.1093/bja/aeu433

1 Guinot P-G, de Broca B, Bernard E, Abou Arab O, Lorne E, Dupont H. Respiratory stroke volume variation assessed by oesophageal Doppler monitoring predicts fluid responsiveness during laparoscopy. Br J Anaesth 2014; 112: 660–4 2 Marik PE, Lemson J. Fluid responsiveness: an evolution of our understanding. Br J Anaesth 2014; 112: 617–20 3 Rauh R, Hemmerling TM, Rist M, et al. Influence of pneumoperitoneum and patient positioning on respiratory system compliance. J Clin Anesth 2001; 13: 361–5 4 Mahjoub Y, Lejeune V, Muller L, et al. Evaluation of pulse pressure variation validity criteria in critically ill patients: a prospective observational multicentre point-prevalence study. Br J Anaesth 2014; 112: 681–5

Hazards of bone cement: for patient and operating theatre personnel.

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