Correspondence line insertion itself rather than insertion of the LMA. He also points out that laryngeal trauma may be avoided by use of an appropriate insertion technique and goes on to suggest how misplacement of the tip can be diagnosed. I was surprised that neither letter made mention of the potential of fibreoptic laryngoscopy in the diagnosis and management of these problems. Partial airway obstruction, such as occurred at the beginning of this case, can be rapidly and noninvasively assessed by passing a fibreoptic instrument down the LMA to the level of the mask aperture bars. Similarly, it can help diagnose misplacement of the LMA, allowing it to be repositioned if the tit, is lying in the laryngeal vestibule. The management of the airway in the presence of a bleeding disorder is always potentially hazardous. In circumstances where a facemask cannot be used, the LMA may be equally appropriate to a tracheal tube, or even a
1005
facemask plus oral airway, if airway maintainance is difficult. I would like to suggest that the presence of a bleeding disorder is only a relative contraindication to LMA insertion. When the L M A is used, it may be possible to reduce the risk of bleeding by inserting it slowly using the standard approach. Fibreoptic laryngoscopy, performed at insertion and regularly thereafter, will allow, the early detection of problems. Finally, this case serves to highlight the hazards of using the subclavian route for central line insertion in a patient with a bleeding diathesis. If the jugular veins had been used, persistent bleeding might have been simply managed with external pressure rather than general anaesthesia and surgical exploration. Royal Perth Hospital, Perth 6001, W . Australia
J. BRIMACOMBE
Laryngeal mask airway and radiotherapy in the prone position
I read with interest the correspondence by D r N. Kee (Anaesthesia 1992; 47: 446-7) on the use of the laryngeal mask airway (LMA) for radiotherapy in the prone position. There is no doubt that the LMA has simplified anaesthesia for radiotherapeutic and radiodiagnostic procedures in children and contributed greatly to the safety of these procedures where maintenance of the airway patency is made more difficult by the positions required during radiotherapy. The LMA eliminates the need for laryngoscopy and avoids the possible morbidity of frequent tracheal intubation. However, the LMA affords no protection against pulmonary aspiration. Dr Kee describes one episode of '. . . minor regurgitation at induction' and then proceeds with general anaesthesia in the prone position. T o continue using a LMA, a t least on this occasion, might be construed as hazardous. Rowbottom and Simpson [I], using fibreoptic laryngoscopy, have shown that partial respiratory
obstruction occurred in up to 50% of children when an LMA was used; this was difficult to detect clinically. As a result, gastric distension could occur if assisted ventilation were used, and combined with the increase in intraabdominal pressure caused by the prone position would increase the risk of regurgitation and pulmonary aspiration. The concept of using the LMA for radiotherapy seems simple, but is far from being totally safe, and anaesthetists should be careful in using this technique for the prone position. Queen Alexandra Hospital, Portsmouth PO6 3LY
M. ELIAS
Reference [ I ] ROWBOTTOM SJ, SIMPSONDL. Partial obstruction of the laryngeal mask airway. Anaesthesia 1990; 45: 892.
The laryngeal mask airway-suboptimal availability, a cause for concern The laryngeal mask airway (LMA) has revolutionised annaesthetic practice. Increasing numbers of reports of its use under various circumstances are appearing in the literature. Having worked at numerous hospitals, it is our impression that the LMA is not as freely available as it should be: it may not be available in the Accident and Emergency or X ray departments, or indeed in certain anaesthetic rooms in the main operating theatres. Not infrequently, the ODA has to borrow one from an adjacent operating theatre, and occasionally one has to go without. We are all aware of the scenario of a failed tracheal intubation in a patient in whom oxygenation cannot be maintained by facemask. Recently one of us (A.R.W.) was unable to intubate the trachea or maintain adequate
oxygenation via a face mask during a Caesarean section, but fortunately an LMA provided an excellent airway and the operation was completed with the patient breathing spontaneously. Had this not been available the consequences might have been catastrophic. Disasters due to loss of airway control are, fortunately, uncommon. However, is it not time that it becomes departmental policy that LMAs should be present, in suitable sizes, o n all intubation trolleys throughout the hospital?. Poole General Hospital, Dorset
A.R. WILLIAMS A. CONE
Combined spinal-extradural anaesthesia for Caesarean section We read with interest the article by Lyons (Anaesthesia 1992; 47: 199-201). Unlike the authors, we strongly recommend the use of single space combined spinal and
extradural anaesthesia (CSE) as the regional anaesthetic technique of choice for Caesarean section. Any regional technique that reduces the requirement for general
1006
Correspondence
anaesthesia has to be recommended and none of the patients in the single space group in the study mentioned required conversion to general anaesthesia. Failure rates ranging from as low as 0.46% to as high as 35% have been quoted for subarachnoid anaesthesia [I]. We were disappointed to see a failure rate of 16% for subarachnoid anaesthesia in the single space group. This, we feel can be reduced to more acceptable levels by greater attention to technical detail, namely by using not only needles of appropriate size and resistance, but also by waiting for cerebrospinal fluid (CSF) to appear a t the hub of the needle prior to injecting. When using a single space technique, Randalls et al. [2] reported a failure rate of 4%, with a 26 gauge Quincke point needle, while Carrie and Donald, using a 26 gauge pencil point needle, reported no failures [3]. We have recently finished conducting a study which compared the resistance to fluid flow of the 26 gauge, 120 mm long Braiin spinal needle with that of the 27 gauge, 120 mm long Becton Dickinson (BD) needle. This was done by using a pressure infusion monitor pump (IVAC 560), a technique previously described by Morris et al. [4]. Surprisingly, we found that the mean resistance to fluid flow for the 26 gauge needle was twice the mean resistance for the 27 gauge needle. The findings of this experiment were confirmed by a controlled randomised study in 100 obstetric patients who required regional anaesthesia. We found that the time taken from dural puncture to appearance of CSF was on average about three times faster with the 27 gauge needle. The failure rate for subarachnoid anaesthesia with the 27 gauge needle was 4% and with the 26 gauge needle was 10%. These failure rates are lower than the 16% reported by Lyons and his colleagues. We feel that needles of low resistance can greatly increase the success rate of subarachnoid anaesthesia for a number of reasons. Firstly, the time taken for CSF to appear a t the hub of the needle is decreased and secondly, not only is aspiration of CSF during and after injection much easier, but also loss of local anaesthetic during injection is less likely. Finally, they are less likely to suffer from blockage and the ability to inject quickly and easily reduces the incidence of patchy blocks. In fact, some of the problems associated with needles of high resistance have already been highlighted by the authors in their evaluation of the 30 gauge needle for single space CSE technique (51. Since the completion of the above study we have used the 27 gauge needle in 190 patients with a failure rate of only 3%. The Middlesex Hospital. London WIN 8AA
M. PATEL A. SWAMI
References [ I ] MANCHIKANT~ L, HADLEY C, MARKWELLSJ, COLLIVER JA. A retrospective analysis of failed spinal anesthetic attempts in a community hospital. Anesthesia and Analgesia 1987; 66: 363-6. [2] RANDALLS B, BROADWAY JW, BROWNE DA, MORGAN B. Comparison of four subarachnoid solutions in a needle through needle technique for elective Caesarean section. British Journal of Anaesthesia 1991; 66: 314-8. [3] CARRIE LES, DONALD F. A 26 gauge pencil point needle for combined epidural anaesthesia for Caesarean section. Anaesthesia 1991; 46: 230-1. [4] MORRISR, ALLENP, VAN RENSBURG M, PHILIP JM. Report of a problem with a spinal needle. Anesthesia and Analgesia 1987; 66: 1 3 4 3 4 . [5] LESSER P, BEMBRIDGEM, LYONSG , MACDONALD R. An evaluation of a 30 gauge needle for spinal anaesthesia for Caesarean section. Anaesthesia 1990; 4 5 767-8.
We were interested to read the account of combined epidural/spinal anaesthesia for Caesarean section from Drs Lyons, Macdonald and Mikl (Anaesthesia 1992; 47: 199-201). We wish to make two observations. When discussing the ‘double space technique’ employing separate epidural and spinal punctures, the authors d o not make clear which procedure is performed first. A recent experience in this unit has led us to advise performing the epidural puncture before dural puncture. A large woman was scheduled for elective Caesarean section, and had requested regional anaesthesia. A combined technique using separate punctures had been explained and agreed. Dural puncture was achieved uneventfully at the L,, interspace by a n experienced senior registrar, with the woman sitting up. After injection of heavy bupivacaine, several attempts were made to site the epidural at L2-3.This proved extremely difficult, and after achieving a bloody tap with the epidural catheter, assistance was sought from the consultant obstetric anaesthetist. The epidural space was cannulated via the L3-4 interspace. Despite appropriate positioning, the level of spinal anaesthesia remained at T,, and it proved impossible to extend it above T, with the epidural. The woman was offered a second spinal but declined, and was given a general anaesthetic. Although siting the epidural catheter before performing spinal block carries a theoretical risk of transfixing the epidural catheter with the spinal needle, we have been unable to do this in vitro when using 24 gauge Sprotte or 25 gauge Whitacre tipped spinal needles. Once the epidural catheter has been successfully inserted dural puncture can proceed in an unhurried manner, rendering the technique suitable for teaching juniors. We are surprised at the failure rate of the ‘through needle’ technique reported. Since this technique was introduced into our maternity unit 4 months ago we have performed 78 Caesarean sections (emergency and elective) using Tuohy guided spinalanaesthesia with a I19 mm 25 g Whiteacre needle. In only one case was dural puncture impossible, and in three women the epidural was used to extend the level of spinal anaesthesia before starting surgery. This represents a failure rate of 5 % using Dr Lyons’ criteria. None of the junior anaesthetists had previous experience of the technique, but it has been accepted enthusiastically. Neither we nor our patients would choose to return to the technique of separate spinal and epidural punctures. Southampton General Hospital, Tremona Road Southampton SO9 4 X Y
E. ROBERTS D. BRIGHOUSE
A reply
Thank you for the opportunity to reply to Drs Roberts and Brighouse. We agree with their comments on order of procedure. At the time of writing we have performed 956 Caesarean sections using combined spinal/epidural anaesthesia and twice have attempted to introduce the ‘through the Tuohy’ technique. In our hands separate punctures work best. The point t o emphasise is, that whichever of these techniques is used, failure of regional anaesthesia, and recourse t o general anaesthesia, is a very rare event. St James University Hospital, Leeds LS9 7TF
G . LYONS R. MACDONALD B. MIKL
1005
facemask plus oral airway, if airway maintainance is difficult. I would like to suggest that the presence of a bleeding disorder is only a relative contraindication to LMA insertion. When the L M A is used, it may be possible to reduce the risk of bleeding by inserting it slowly using the standard approach. Fibreoptic laryngoscopy, performed at insertion and regularly thereafter, will allow, the early detection of problems. Finally, this case serves to highlight the hazards of using the subclavian route for central line insertion in a patient with a bleeding diathesis. If the jugular veins had been used, persistent bleeding might have been simply managed with external pressure rather than general anaesthesia and surgical exploration. Royal Perth Hospital, Perth 6001, W . Australia
J. BRIMACOMBE
Laryngeal mask airway and radiotherapy in the prone position
I read with interest the correspondence by D r N. Kee (Anaesthesia 1992; 47: 446-7) on the use of the laryngeal mask airway (LMA) for radiotherapy in the prone position. There is no doubt that the LMA has simplified anaesthesia for radiotherapeutic and radiodiagnostic procedures in children and contributed greatly to the safety of these procedures where maintenance of the airway patency is made more difficult by the positions required during radiotherapy. The LMA eliminates the need for laryngoscopy and avoids the possible morbidity of frequent tracheal intubation. However, the LMA affords no protection against pulmonary aspiration. Dr Kee describes one episode of '. . . minor regurgitation at induction' and then proceeds with general anaesthesia in the prone position. T o continue using a LMA, a t least on this occasion, might be construed as hazardous. Rowbottom and Simpson [I], using fibreoptic laryngoscopy, have shown that partial respiratory
obstruction occurred in up to 50% of children when an LMA was used; this was difficult to detect clinically. As a result, gastric distension could occur if assisted ventilation were used, and combined with the increase in intraabdominal pressure caused by the prone position would increase the risk of regurgitation and pulmonary aspiration. The concept of using the LMA for radiotherapy seems simple, but is far from being totally safe, and anaesthetists should be careful in using this technique for the prone position. Queen Alexandra Hospital, Portsmouth PO6 3LY
M. ELIAS
Reference [ I ] ROWBOTTOM SJ, SIMPSONDL. Partial obstruction of the laryngeal mask airway. Anaesthesia 1990; 45: 892.
The laryngeal mask airway-suboptimal availability, a cause for concern The laryngeal mask airway (LMA) has revolutionised annaesthetic practice. Increasing numbers of reports of its use under various circumstances are appearing in the literature. Having worked at numerous hospitals, it is our impression that the LMA is not as freely available as it should be: it may not be available in the Accident and Emergency or X ray departments, or indeed in certain anaesthetic rooms in the main operating theatres. Not infrequently, the ODA has to borrow one from an adjacent operating theatre, and occasionally one has to go without. We are all aware of the scenario of a failed tracheal intubation in a patient in whom oxygenation cannot be maintained by facemask. Recently one of us (A.R.W.) was unable to intubate the trachea or maintain adequate
oxygenation via a face mask during a Caesarean section, but fortunately an LMA provided an excellent airway and the operation was completed with the patient breathing spontaneously. Had this not been available the consequences might have been catastrophic. Disasters due to loss of airway control are, fortunately, uncommon. However, is it not time that it becomes departmental policy that LMAs should be present, in suitable sizes, o n all intubation trolleys throughout the hospital?. Poole General Hospital, Dorset
A.R. WILLIAMS A. CONE
Combined spinal-extradural anaesthesia for Caesarean section We read with interest the article by Lyons (Anaesthesia 1992; 47: 199-201). Unlike the authors, we strongly recommend the use of single space combined spinal and
extradural anaesthesia (CSE) as the regional anaesthetic technique of choice for Caesarean section. Any regional technique that reduces the requirement for general
1006
Correspondence
anaesthesia has to be recommended and none of the patients in the single space group in the study mentioned required conversion to general anaesthesia. Failure rates ranging from as low as 0.46% to as high as 35% have been quoted for subarachnoid anaesthesia [I]. We were disappointed to see a failure rate of 16% for subarachnoid anaesthesia in the single space group. This, we feel can be reduced to more acceptable levels by greater attention to technical detail, namely by using not only needles of appropriate size and resistance, but also by waiting for cerebrospinal fluid (CSF) to appear a t the hub of the needle prior to injecting. When using a single space technique, Randalls et al. [2] reported a failure rate of 4%, with a 26 gauge Quincke point needle, while Carrie and Donald, using a 26 gauge pencil point needle, reported no failures [3]. We have recently finished conducting a study which compared the resistance to fluid flow of the 26 gauge, 120 mm long Braiin spinal needle with that of the 27 gauge, 120 mm long Becton Dickinson (BD) needle. This was done by using a pressure infusion monitor pump (IVAC 560), a technique previously described by Morris et al. [4]. Surprisingly, we found that the mean resistance to fluid flow for the 26 gauge needle was twice the mean resistance for the 27 gauge needle. The findings of this experiment were confirmed by a controlled randomised study in 100 obstetric patients who required regional anaesthesia. We found that the time taken from dural puncture to appearance of CSF was on average about three times faster with the 27 gauge needle. The failure rate for subarachnoid anaesthesia with the 27 gauge needle was 4% and with the 26 gauge needle was 10%. These failure rates are lower than the 16% reported by Lyons and his colleagues. We feel that needles of low resistance can greatly increase the success rate of subarachnoid anaesthesia for a number of reasons. Firstly, the time taken for CSF to appear a t the hub of the needle is decreased and secondly, not only is aspiration of CSF during and after injection much easier, but also loss of local anaesthetic during injection is less likely. Finally, they are less likely to suffer from blockage and the ability to inject quickly and easily reduces the incidence of patchy blocks. In fact, some of the problems associated with needles of high resistance have already been highlighted by the authors in their evaluation of the 30 gauge needle for single space CSE technique (51. Since the completion of the above study we have used the 27 gauge needle in 190 patients with a failure rate of only 3%. The Middlesex Hospital. London WIN 8AA
M. PATEL A. SWAMI
References [ I ] MANCHIKANT~ L, HADLEY C, MARKWELLSJ, COLLIVER JA. A retrospective analysis of failed spinal anesthetic attempts in a community hospital. Anesthesia and Analgesia 1987; 66: 363-6. [2] RANDALLS B, BROADWAY JW, BROWNE DA, MORGAN B. Comparison of four subarachnoid solutions in a needle through needle technique for elective Caesarean section. British Journal of Anaesthesia 1991; 66: 314-8. [3] CARRIE LES, DONALD F. A 26 gauge pencil point needle for combined epidural anaesthesia for Caesarean section. Anaesthesia 1991; 46: 230-1. [4] MORRISR, ALLENP, VAN RENSBURG M, PHILIP JM. Report of a problem with a spinal needle. Anesthesia and Analgesia 1987; 66: 1 3 4 3 4 . [5] LESSER P, BEMBRIDGEM, LYONSG , MACDONALD R. An evaluation of a 30 gauge needle for spinal anaesthesia for Caesarean section. Anaesthesia 1990; 4 5 767-8.
We were interested to read the account of combined epidural/spinal anaesthesia for Caesarean section from Drs Lyons, Macdonald and Mikl (Anaesthesia 1992; 47: 199-201). We wish to make two observations. When discussing the ‘double space technique’ employing separate epidural and spinal punctures, the authors d o not make clear which procedure is performed first. A recent experience in this unit has led us to advise performing the epidural puncture before dural puncture. A large woman was scheduled for elective Caesarean section, and had requested regional anaesthesia. A combined technique using separate punctures had been explained and agreed. Dural puncture was achieved uneventfully at the L,, interspace by a n experienced senior registrar, with the woman sitting up. After injection of heavy bupivacaine, several attempts were made to site the epidural at L2-3.This proved extremely difficult, and after achieving a bloody tap with the epidural catheter, assistance was sought from the consultant obstetric anaesthetist. The epidural space was cannulated via the L3-4 interspace. Despite appropriate positioning, the level of spinal anaesthesia remained at T,, and it proved impossible to extend it above T, with the epidural. The woman was offered a second spinal but declined, and was given a general anaesthetic. Although siting the epidural catheter before performing spinal block carries a theoretical risk of transfixing the epidural catheter with the spinal needle, we have been unable to do this in vitro when using 24 gauge Sprotte or 25 gauge Whitacre tipped spinal needles. Once the epidural catheter has been successfully inserted dural puncture can proceed in an unhurried manner, rendering the technique suitable for teaching juniors. We are surprised at the failure rate of the ‘through needle’ technique reported. Since this technique was introduced into our maternity unit 4 months ago we have performed 78 Caesarean sections (emergency and elective) using Tuohy guided spinalanaesthesia with a I19 mm 25 g Whiteacre needle. In only one case was dural puncture impossible, and in three women the epidural was used to extend the level of spinal anaesthesia before starting surgery. This represents a failure rate of 5 % using Dr Lyons’ criteria. None of the junior anaesthetists had previous experience of the technique, but it has been accepted enthusiastically. Neither we nor our patients would choose to return to the technique of separate spinal and epidural punctures. Southampton General Hospital, Tremona Road Southampton SO9 4 X Y
E. ROBERTS D. BRIGHOUSE
A reply
Thank you for the opportunity to reply to Drs Roberts and Brighouse. We agree with their comments on order of procedure. At the time of writing we have performed 956 Caesarean sections using combined spinal/epidural anaesthesia and twice have attempted to introduce the ‘through the Tuohy’ technique. In our hands separate punctures work best. The point t o emphasise is, that whichever of these techniques is used, failure of regional anaesthesia, and recourse t o general anaesthesia, is a very rare event. St James University Hospital, Leeds LS9 7TF
G . LYONS R. MACDONALD B. MIKL
