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Perioperative management of diabetes mellitus
British Journal of Anaesthesia
866 the alkalinized mixture solution for both elective and emergency Caesarean section under extradural anaesthesia as it provides rapid anaesthesia, in addition to good analgesia. M. PATEL
Department of Anaesthesia Ealing Hospital Middlesex R. A. G. FERNANDO
Royal Free Hospital London
V. CLARK E. MCGRADY C. SUGDEN J. DICKSON G. MCLEOD
Royal Infirmary of Edinburgh Edinburgh Sir,—Thank you for the opportunity to reply to Drs Patel and Fernando. We will respond to the points in the order in which they were made. First, the authors suggest that spread of extradural anaesthesia is related to vertebral column length rather than body height. To support this, they reference two papers. Norris' paper investigated subarachnoid anaesthesia and found no correlation between spread of anaesthesia and vertebral column length. The study of Gambling and colleagues did not measure vertebral column length. Bromage demonstrated a weak correlation between body height and spread of sensory extradural block [1] and suggested this was relevant at extremes of height. Our "short" group was less than 1.52 m and our "tall" group was more than 1.71 m which gives a broad "normal" range; similar methods have been used by other authors [2]. The authors correctly observed that despite randomization, the women in the room temperature group were significantly taller than those in the other groups and they suggest that they therefore received larger volumes of lignocaine which contributed to blocks of faster onset. The volume of lignocaine received by the room temperature group was 22.6 ml which was less than the room temperature bupivacaine group (23.9 ml). Despite smaller volumes, onset time with room temperature lignocaine was faster than room temperature bupivacaine (27.0 min cf. 29.9 min). This finding is supported by other authors [2, 3]. Local anaesthetic solutions containing adrenaline, whether at room temperature or warmed, are unstable and we clearly stated in the methods section that adrenaline was added immediately before injection. We do not advocate the use of pre-mixed local anaesthetic with adrenaline because these contain high concentrations of sodium metabisulphate which are potentially neurotoxic. Drs Patel and Fernando thought that our extradural failure rate was high. Of the 120 patients, we had to resort to one general anaesthetic, and converted five extradurals to spinals. We do not consider our supplementary analgesia rate of 39 % to be excessive as the range of supplementary analgesia varies from study to study (11-48%) [2-4]. We have a low threshold for administration of
1. Bromage PR. Epidural Analgesia. Philadelphia: WB Saunders Co, 1978 2. Reid JA, Thorburn J. Extradural lignocaine or bupivacaine anaesthesia for elective Caesarean section: the role of maternal posture. British Journal of Anaesthesia 1988; 61: 149-153. 3. Norton AC, Davis AG, Spicer RJ. Lignocaine 2% with adrenaline for epidural Caesarean section. A comparison with 0.5% bupivacaine. Anaesthesia 1988; 43: 844-849. 4. Price ML, Reynolds F, Morgan BM. Extending epidural blockade for emergency Caesarean section. Evaluation of 2 % lignocaine with adrenaline. International Journal of Obstetric Anesthesia 1991; 1: 13-1. 5. Dell RG, Orlikowski CE. Unexpectedly high spinal anaesthesia following failed extradural anaesthesia for Caesarean section. Anaesthesia 1993; 48: 641. 6. Fernando R, Jones HM. Comparison of plain and alkalinized local anaesthetic mixtures of lignocaine and bupivacaine for elective extradural Caesarean section. British Journal of Anaesthesia 1991; 67: 699-703.
Perioperative management of diabetes mellitus Sir,—In his recent editorial on the perioperative management of the insulin-dependent diabetic patient [1], the author advocated the i.v. route, by continuous infusion, as a logical method of administering insulin. Two methods of continuous administration were mentioned: combined infusion of glucose-insulin-potassium (GIK regimen) described by Alberti and Thomas [2], and the use of variable-rate separate glucose and insulin infusions [3]. We feel that while the latter regimen is gaining in popularity, there are potential side effects, one of which was illustrated by a recent case at a hospital in this city. A 40-yr-old woman presented for a total abdominal hysterectomy and gave a 30-yr history of insulin-dependent diabetes treated by twice daily injections of insulin. Her preoperative haemoglobin A,c concentration was 6%, implying adequate
Downloaded from http://bja.oxfordjournals.org/ at University of Iowa Libraries/Serials Acquisitions on July 2, 2015
1. Clarke V, McGrady E, Sugden C, Dickson J, McLeod G. Speed of onset of sensory block for elective extradural Caesarean section: choice of agent and temperature of injectate. British Journal of Anaesthesia 1994; 72: 221-223. 2. Norris MC. Patient variables and the subarachnoid spread of hyperbaric bupivacaine in the term parturient. Anesthesiology 1990; 72: 478-482. 3. Gambling DR, Mayson K, McMorland GH, Moore R. Predictability of spread of epidural anesthesia for cesarean section using incremental dose lidocaine hydrocarbonate with epinephrine. Regional Anesthesia 1989; 14: 133-137. 4. Chen BJ, Kwan WF, Virtusio L. Comparison of body weight and vertebral column length in the term pregnant woman. Anesthesia and Analgesia 1990; 70: S55. 5. Dawson PJ, Bjorksten AR, Duncan IP, Barnes RK, Beemer GH. Stability of fentanyl, bupivacaine and adrenaline solutions for extradural infusion. British Journal of Anaesthesia 1992; 68: 414-^17. 6. Howell P, Davies W, Wrigley M, Tan P, Morgan B. Comparison of four local extradural anaesthetic solutions for elective Caesarean section. British Journal of Anaesthesia 1990; 65: 648-653. 7. Fernando R, Jones HM. Comparison of plain and alkalinized local anaesthetic mixtures of lignocaine and bupivacaine for extradural Caesarean section. British Journal of Anaesthesia 1991; 67: 699-703.
supplementary anaesthesia, reflected in the high patient satisfaction scores. Drs Patel and Fernando asked who sited the blocks. The extradurals were all sited by the authors of our paper who were post-fellowship registrars with at least 3 yr anaesthetic experience, or consultants. The women who had inadequate blocks, denned as failing to reach analgesia to pinprick at T6 despite maximum local anaesthetic doses, received spinal anaesthesia. Drs Patel and Fernando expressed anxiety about spinal anaesthesia after failed extradural anaesthesia. While it is true that high blocks can occur, in the two case reports referenced, the mothers received large volumes of subarachnoid local anaesthetic (2.5-3 ml) after failed extradural anaesthesia. We agree with Dell and Orlikowski [5] that caution should be exercised in these circumstances. The dose of local anaesthetic should be reduced and the risks of general anaesthesia avoided. All five mothers who received a spinal anaesthetic in our series received a reduced dose of local anaesthetic with satisfactory results. Finally, they recommend the technique described by Fernando and Jones [6] who produced a fast onset time for extradural anaesthesia by alkalinizing a mixture of 2 % lignocaine and 0.5 % bupivacaine with adrenaline 1:200000, although the number of patients in this study was small (20 women). This study involved mixing the two local anaesthetics and then adding adrenaline and sodium bicarbonate. Each addition has a potential for error and is also time-consuming. The authors state that quality of analgesia produced by using this solution was "much better" than in our study. Methods of assessing quality of block differed in the two studies and cannot be compared. Warming 2% lignocaine is simple, and in an emergency situation, a top-up with warmed 2 % lignocaine with adrenaline results in rapid onset of block such that the patient is ready for skin incision by the time she has been transported to theatre.
867
preoperative control of blood glucose and there were no obvious side effects of diabetes, particularly renal dysfunction, autonomic neuropathy, eye disease or hypertension. On the morning of surgery, preoperative blood glucose concentration was 6 mmol litre"1 and she was commenced on an infusion of 10% glucose with potassium chloride 10 mmol and a separate infusion of insulin via a Graseby 300 infusion pump at a rate of 2 u. h"1. She was given a general anaesthetic and her postoperative pain was managed by extradural infusion of a local anaesthetic and opioid mixture. Blood glucose in the early postoperative period was within acceptable limits and she was transferred back to the surgical ward after 1 h in the recovery unit. Blood glucose measurements were carried out at 2-h intervals initially and there was a progressive increase over the subsequent 6 h to a concentration of 25 mmol litre"1 together with the development of ketonuria. The anaesthetist concerned was contacted by telephone and was informed of the patient's condition. Subsequent management consistent of i.v. boluses of soluble insulin given by syringe as opposed to bolus doses from the infusion pump and the patient's blood glucose concentration over the subsequent 4 h decreased to 15 mmol litre""1. It was at this point that the nursing staff became aware of the fact that the insulin infusion had been inadvertently switched off at some stage after return to the surgical ward. On restarting the insulin the patient's condition settled and her subsequent recovery was largely uneventful. We feel that human error in this case almost led to serious morbidity in that the patient's condition was deteriorating towards a keto-acidotic coma. This complication would have been unlikely to develop if a combined GIK regime had been used as failure to commence the infusion would have resulted in cessation of both insulin and glucose and for this reason we would advocate this regimen in the perioperative management of insulin-dependent diabetes. We also agree with Dr Hall that an important factor in good glycaemic control is frequent measurement of blood glucose concentration and its interpretation by well trained staff [4]. In this case, 2-hourly blood glucose measurement prevented an uncontrolled increase in blood glucose concentration. P. MCCONAGHY N. KENNEDY D . COLEMAN
Department of Anaesthesia Royal Perth Hospital Perth, Western Australia 1. Hall GM. Insulin administration in diabetic patients—return of the bolus? British Journal of Anaesthesia 1994; 72: 1-2. 2. Alberti KGMM, Thomas DJB. The management of diabetes during surgery. British Journal of Anaesthesia 1979; 51: 693-710. 3. Watts NB, Gebhart SP, Clark RV, Phillips LS. Perioperative management of diabetes mellitus: steady-stage glucose control with bedside algorithm for insulin adjustment. Diabetes Care 1987; 10: 722-728.
4. Milaskiewicz RM, Hall GM. Diabetes and anaesthesia: The past decade. British Journal of Anaesthesia 1992; 68: 198-206.
Anaesthetic simulators Sir,—In a recent editorial, A. J. Asbury described the present state of anaesthetic simulator development [1]. He suggested that currently available theatre-type simulators (TTS) require a secure training room, expensive computer hardware, a specially trained operator and the purchase of a new anaesthetic machine and monitors. The Anaesthetic Computer Controlled Emergency Situation Simulator (ACCESS) [2] has been designed to provide the same realistic training as the simulators mentioned. It is portable, can be used with unmodified anaesthetic machines and ventilators, uses a very basic computer and is relatively simple to operate. Furthermore, it has been used successfully to train junior staff for over a year and the scenarios used are based on current UK practice. I agree that simulators have the potential to lead to an improvement in patient care, but would suggest that ACCESS has already overcome many of the problems mentioned. A. J. BYRNE
Department of Anaesthesia Queen Elizabeth Hospital King's Lynn, Norfolk 1. Asbury AJ. Simulators for general anaesthesia. British Journal of Anaesthesia 1994; 73: 285-286. 2. Byrne AJ, Hilton PJ, Lunn JN. Basic simulations for anaesthetists—A pilot study of the ACCESS system. Anaesthesia 1994; 49: 376-381. Sir,—My view is that simulators will become more comprehensive in the facilities they offer, and will eventually include computationally intensive deep models of pharmacological effects. In addition, data will need to be collected from anaesthetic machines, particularly the well integrated ones, to indicate, for example, high airway pressure. In addition, it may be necessary to "introduce" faults (by electronic methods) into modified anaesthetic machines, faults which might be discovered during the cockpit check. All this is likely to be expensive and require dedicated equipment. The cost of the simulation supervisor is also relevant. The commendable work of Drs Byrne, Hilton and Lunn has the major advantage of allowing a first step in simulation, but if one wishes to go further, then dedicated equipment will be needed. A. J. ASBURY
University Department of Anaesthetics Western Infirmary Glasgow
ded from http://bja.oxfordjournals.org/ at University of Iowa Libraries/Serials Acquisitions on July 2, 2015
Correspondence
866 the alkalinized mixture solution for both elective and emergency Caesarean section under extradural anaesthesia as it provides rapid anaesthesia, in addition to good analgesia. M. PATEL
Department of Anaesthesia Ealing Hospital Middlesex R. A. G. FERNANDO
Royal Free Hospital London
V. CLARK E. MCGRADY C. SUGDEN J. DICKSON G. MCLEOD
Royal Infirmary of Edinburgh Edinburgh Sir,—Thank you for the opportunity to reply to Drs Patel and Fernando. We will respond to the points in the order in which they were made. First, the authors suggest that spread of extradural anaesthesia is related to vertebral column length rather than body height. To support this, they reference two papers. Norris' paper investigated subarachnoid anaesthesia and found no correlation between spread of anaesthesia and vertebral column length. The study of Gambling and colleagues did not measure vertebral column length. Bromage demonstrated a weak correlation between body height and spread of sensory extradural block [1] and suggested this was relevant at extremes of height. Our "short" group was less than 1.52 m and our "tall" group was more than 1.71 m which gives a broad "normal" range; similar methods have been used by other authors [2]. The authors correctly observed that despite randomization, the women in the room temperature group were significantly taller than those in the other groups and they suggest that they therefore received larger volumes of lignocaine which contributed to blocks of faster onset. The volume of lignocaine received by the room temperature group was 22.6 ml which was less than the room temperature bupivacaine group (23.9 ml). Despite smaller volumes, onset time with room temperature lignocaine was faster than room temperature bupivacaine (27.0 min cf. 29.9 min). This finding is supported by other authors [2, 3]. Local anaesthetic solutions containing adrenaline, whether at room temperature or warmed, are unstable and we clearly stated in the methods section that adrenaline was added immediately before injection. We do not advocate the use of pre-mixed local anaesthetic with adrenaline because these contain high concentrations of sodium metabisulphate which are potentially neurotoxic. Drs Patel and Fernando thought that our extradural failure rate was high. Of the 120 patients, we had to resort to one general anaesthetic, and converted five extradurals to spinals. We do not consider our supplementary analgesia rate of 39 % to be excessive as the range of supplementary analgesia varies from study to study (11-48%) [2-4]. We have a low threshold for administration of
1. Bromage PR. Epidural Analgesia. Philadelphia: WB Saunders Co, 1978 2. Reid JA, Thorburn J. Extradural lignocaine or bupivacaine anaesthesia for elective Caesarean section: the role of maternal posture. British Journal of Anaesthesia 1988; 61: 149-153. 3. Norton AC, Davis AG, Spicer RJ. Lignocaine 2% with adrenaline for epidural Caesarean section. A comparison with 0.5% bupivacaine. Anaesthesia 1988; 43: 844-849. 4. Price ML, Reynolds F, Morgan BM. Extending epidural blockade for emergency Caesarean section. Evaluation of 2 % lignocaine with adrenaline. International Journal of Obstetric Anesthesia 1991; 1: 13-1. 5. Dell RG, Orlikowski CE. Unexpectedly high spinal anaesthesia following failed extradural anaesthesia for Caesarean section. Anaesthesia 1993; 48: 641. 6. Fernando R, Jones HM. Comparison of plain and alkalinized local anaesthetic mixtures of lignocaine and bupivacaine for elective extradural Caesarean section. British Journal of Anaesthesia 1991; 67: 699-703.
Perioperative management of diabetes mellitus Sir,—In his recent editorial on the perioperative management of the insulin-dependent diabetic patient [1], the author advocated the i.v. route, by continuous infusion, as a logical method of administering insulin. Two methods of continuous administration were mentioned: combined infusion of glucose-insulin-potassium (GIK regimen) described by Alberti and Thomas [2], and the use of variable-rate separate glucose and insulin infusions [3]. We feel that while the latter regimen is gaining in popularity, there are potential side effects, one of which was illustrated by a recent case at a hospital in this city. A 40-yr-old woman presented for a total abdominal hysterectomy and gave a 30-yr history of insulin-dependent diabetes treated by twice daily injections of insulin. Her preoperative haemoglobin A,c concentration was 6%, implying adequate
Downloaded from http://bja.oxfordjournals.org/ at University of Iowa Libraries/Serials Acquisitions on July 2, 2015
1. Clarke V, McGrady E, Sugden C, Dickson J, McLeod G. Speed of onset of sensory block for elective extradural Caesarean section: choice of agent and temperature of injectate. British Journal of Anaesthesia 1994; 72: 221-223. 2. Norris MC. Patient variables and the subarachnoid spread of hyperbaric bupivacaine in the term parturient. Anesthesiology 1990; 72: 478-482. 3. Gambling DR, Mayson K, McMorland GH, Moore R. Predictability of spread of epidural anesthesia for cesarean section using incremental dose lidocaine hydrocarbonate with epinephrine. Regional Anesthesia 1989; 14: 133-137. 4. Chen BJ, Kwan WF, Virtusio L. Comparison of body weight and vertebral column length in the term pregnant woman. Anesthesia and Analgesia 1990; 70: S55. 5. Dawson PJ, Bjorksten AR, Duncan IP, Barnes RK, Beemer GH. Stability of fentanyl, bupivacaine and adrenaline solutions for extradural infusion. British Journal of Anaesthesia 1992; 68: 414-^17. 6. Howell P, Davies W, Wrigley M, Tan P, Morgan B. Comparison of four local extradural anaesthetic solutions for elective Caesarean section. British Journal of Anaesthesia 1990; 65: 648-653. 7. Fernando R, Jones HM. Comparison of plain and alkalinized local anaesthetic mixtures of lignocaine and bupivacaine for extradural Caesarean section. British Journal of Anaesthesia 1991; 67: 699-703.
supplementary anaesthesia, reflected in the high patient satisfaction scores. Drs Patel and Fernando asked who sited the blocks. The extradurals were all sited by the authors of our paper who were post-fellowship registrars with at least 3 yr anaesthetic experience, or consultants. The women who had inadequate blocks, denned as failing to reach analgesia to pinprick at T6 despite maximum local anaesthetic doses, received spinal anaesthesia. Drs Patel and Fernando expressed anxiety about spinal anaesthesia after failed extradural anaesthesia. While it is true that high blocks can occur, in the two case reports referenced, the mothers received large volumes of subarachnoid local anaesthetic (2.5-3 ml) after failed extradural anaesthesia. We agree with Dell and Orlikowski [5] that caution should be exercised in these circumstances. The dose of local anaesthetic should be reduced and the risks of general anaesthesia avoided. All five mothers who received a spinal anaesthetic in our series received a reduced dose of local anaesthetic with satisfactory results. Finally, they recommend the technique described by Fernando and Jones [6] who produced a fast onset time for extradural anaesthesia by alkalinizing a mixture of 2 % lignocaine and 0.5 % bupivacaine with adrenaline 1:200000, although the number of patients in this study was small (20 women). This study involved mixing the two local anaesthetics and then adding adrenaline and sodium bicarbonate. Each addition has a potential for error and is also time-consuming. The authors state that quality of analgesia produced by using this solution was "much better" than in our study. Methods of assessing quality of block differed in the two studies and cannot be compared. Warming 2% lignocaine is simple, and in an emergency situation, a top-up with warmed 2 % lignocaine with adrenaline results in rapid onset of block such that the patient is ready for skin incision by the time she has been transported to theatre.
867
preoperative control of blood glucose and there were no obvious side effects of diabetes, particularly renal dysfunction, autonomic neuropathy, eye disease or hypertension. On the morning of surgery, preoperative blood glucose concentration was 6 mmol litre"1 and she was commenced on an infusion of 10% glucose with potassium chloride 10 mmol and a separate infusion of insulin via a Graseby 300 infusion pump at a rate of 2 u. h"1. She was given a general anaesthetic and her postoperative pain was managed by extradural infusion of a local anaesthetic and opioid mixture. Blood glucose in the early postoperative period was within acceptable limits and she was transferred back to the surgical ward after 1 h in the recovery unit. Blood glucose measurements were carried out at 2-h intervals initially and there was a progressive increase over the subsequent 6 h to a concentration of 25 mmol litre"1 together with the development of ketonuria. The anaesthetist concerned was contacted by telephone and was informed of the patient's condition. Subsequent management consistent of i.v. boluses of soluble insulin given by syringe as opposed to bolus doses from the infusion pump and the patient's blood glucose concentration over the subsequent 4 h decreased to 15 mmol litre""1. It was at this point that the nursing staff became aware of the fact that the insulin infusion had been inadvertently switched off at some stage after return to the surgical ward. On restarting the insulin the patient's condition settled and her subsequent recovery was largely uneventful. We feel that human error in this case almost led to serious morbidity in that the patient's condition was deteriorating towards a keto-acidotic coma. This complication would have been unlikely to develop if a combined GIK regime had been used as failure to commence the infusion would have resulted in cessation of both insulin and glucose and for this reason we would advocate this regimen in the perioperative management of insulin-dependent diabetes. We also agree with Dr Hall that an important factor in good glycaemic control is frequent measurement of blood glucose concentration and its interpretation by well trained staff [4]. In this case, 2-hourly blood glucose measurement prevented an uncontrolled increase in blood glucose concentration. P. MCCONAGHY N. KENNEDY D . COLEMAN
Department of Anaesthesia Royal Perth Hospital Perth, Western Australia 1. Hall GM. Insulin administration in diabetic patients—return of the bolus? British Journal of Anaesthesia 1994; 72: 1-2. 2. Alberti KGMM, Thomas DJB. The management of diabetes during surgery. British Journal of Anaesthesia 1979; 51: 693-710. 3. Watts NB, Gebhart SP, Clark RV, Phillips LS. Perioperative management of diabetes mellitus: steady-stage glucose control with bedside algorithm for insulin adjustment. Diabetes Care 1987; 10: 722-728.
4. Milaskiewicz RM, Hall GM. Diabetes and anaesthesia: The past decade. British Journal of Anaesthesia 1992; 68: 198-206.
Anaesthetic simulators Sir,—In a recent editorial, A. J. Asbury described the present state of anaesthetic simulator development [1]. He suggested that currently available theatre-type simulators (TTS) require a secure training room, expensive computer hardware, a specially trained operator and the purchase of a new anaesthetic machine and monitors. The Anaesthetic Computer Controlled Emergency Situation Simulator (ACCESS) [2] has been designed to provide the same realistic training as the simulators mentioned. It is portable, can be used with unmodified anaesthetic machines and ventilators, uses a very basic computer and is relatively simple to operate. Furthermore, it has been used successfully to train junior staff for over a year and the scenarios used are based on current UK practice. I agree that simulators have the potential to lead to an improvement in patient care, but would suggest that ACCESS has already overcome many of the problems mentioned. A. J. BYRNE
Department of Anaesthesia Queen Elizabeth Hospital King's Lynn, Norfolk 1. Asbury AJ. Simulators for general anaesthesia. British Journal of Anaesthesia 1994; 73: 285-286. 2. Byrne AJ, Hilton PJ, Lunn JN. Basic simulations for anaesthetists—A pilot study of the ACCESS system. Anaesthesia 1994; 49: 376-381. Sir,—My view is that simulators will become more comprehensive in the facilities they offer, and will eventually include computationally intensive deep models of pharmacological effects. In addition, data will need to be collected from anaesthetic machines, particularly the well integrated ones, to indicate, for example, high airway pressure. In addition, it may be necessary to "introduce" faults (by electronic methods) into modified anaesthetic machines, faults which might be discovered during the cockpit check. All this is likely to be expensive and require dedicated equipment. The cost of the simulation supervisor is also relevant. The commendable work of Drs Byrne, Hilton and Lunn has the major advantage of allowing a first step in simulation, but if one wishes to go further, then dedicated equipment will be needed. A. J. ASBURY
University Department of Anaesthetics Western Infirmary Glasgow
ded from http://bja.oxfordjournals.org/ at University of Iowa Libraries/Serials Acquisitions on July 2, 2015
Correspondence