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The sitting position in neurosurgical anaesthesia: a survey of British practice in 1991†
British Journal of Anaesthesia 1994; 73: 247-248
The sitting position in neurosurgical anaesthesia: a survey of British practice in 199If R. J. ELTON AND R. S. C. HOWELL
SUMMARY
KEY WORDS Anaesthesia: neurosurgical. Position, effects. Position: sitting
The use of the sitting position for patients undergoing posterior fossa and cervical spinal surgery represents a unique physiological challenge and is associated with several important complications. In 1981, Campkin [1] reported that 19 (53%) of the 36 neurosurgical centres in the UK always used the sitting position for posterior fossa surgery and 11 (30%) always used it for posterior cervical spinal surgery. We set out to establish the extent of the use of the sitting position in the UK in 1991 and to compare this with the situation in 1981. METHODS AND RESULTS
At the end of 1991 we mailed a questionnaire with a reply paid envelope to all 160 members of the Neuroanaesthetists' Travelling Club, a UK society, the members of which have a major interest in the practice of anaesthesia for neurosurgery (the club has since been renamed the Neuroanaesthesia Society of Great Britain and Ireland). The respondents were asked to specify which position they currently used for patients undergoing posterior fossa or posterior cervical surgery, if they used spontaneous respiration or intermittent positive pressure ventilation (IPPV) and which monitoring techniques were used. We received 124 replies, a response rate of 78%, of which 109 replies were returned fully completed,
TABLE I. Patient pojttions used m neurosurgical centres for posterior fossa surgery and posterior cervical surgery m 1981 and 1991. * P < 0 05, ** P < 0.01 compared tvith 1981 Sitting posiuon always (" (%)) Posterior fossa surgery 1981 19 (53) 1991 8 (20)** Posterior cervical surgery 1981 11(31) 3(7)* 1991
Other positions always (" (%)) 13 (36) 22 (54) 17(47) 31 (76)**
All three positions (« (%)) 4(11) 11 (27)** 8(22) 7(17)
Total centres 36 41 36 41
R. J. ELTON, M.B., CH.B., F.R.C.A., R. S. C. HOWELL, M.B., B.S., D.OBST., R.C.O.G., F.R.C.A., Departments of Anaesthetics and
Neurosurgery, Walsgrave Hospital, Coventry, West Midlands CV2 2DX. Accepted for Publication: February 22, 1994. tThis paper was presented at the Registrars' Prize Meeting of the Midland Society of Anaesthetists in Birmingham in March 1992 and an abstract was published in the Midland Society of Anaesthetists Newsletter for Summer 1992. The data shown in the paper were used in a poster presentation at the Combined Meeting of the Neurosurgical Anaesthetists' Travelling Club and the American Society of Neurosurgical Anaesthesia and Critical Care in London, June 1992.
Downloaded from http://bja.oxfordjournals.org/ at Pennsylvania State University on May 25, 2015
A postal survey of 160 members of the Neurosurgical Anaesthetists' Travelling Club was conducted in 1991 to investigate the current use of the sitting position in neurosurgery. There was a 78% response rate; at least one reply was received from every neurosurgical centre in the UK. Patients were placed normally in the sitting position for posterior fossa surgery in eight (20%) of the centres, compared with 19 (53%) in 1981. For posterior cervical spinal surgery, only three (7%) centres routinely used the sitting position, compared with 11 (31%) in 1981. Thus in the period 1981-1991, the number of neurosurgical centres using the sitting position routinely, decreased by more than 50%. Current techniques of ventilation and monitoring for the sitting position are discussed briefly. (Br. J. Anaesth. 1994; 73: 247-248)
68 % of the original mailing. Replies were received from 41 centres, including all 39 in the UK and one each in Ireland and Hong Kong, which have been included in the analysis as they were considered to be representative of British practice. It was noted that 24 (15%) of the Club's members were not anaesthetists and that the non-responders were mainly from this group: we decided that as this questionnaire was not relevant to these individuals, it would be acceptable to proceed to analyse and draw conclusions from the questionnaires returned. From the replies the respondents were divided into three groups: (1) those who always used the sitting position; (2) those who always used other positions (prone or lateral) and never used the sitting position; (3) those who used any of the three positions, including the sitting position. As each anaesthetist's practice was usually the same as the others in the same centre, we aggregated the responses into their respective centres to facilitate close comparison with the situation in 1981. The chisquare test was used for statistical comparison between groups. P < 0.05 was considered statistically significant. The results are summarised in table I. Compared with 1981, there was a significant reduction in the
BRITISH JOURNAL OF ANAESTHESIA
248
COMMENT
The advantages of the sitting position are entirely surgical, in that it facilitates surgical access to some parts of the posterior fossa and can also lead to a reduction in the amount of venous bleeding during surgery. The disadvantages [2-4] are that the associated subatmospheric pressure in the veins at the base of the skull may encourage venous air embolism and that arterial hypotension may lead to a disproportionate reduction in cerebral blood flow because of the gravitational effect of the vertical
distance between the heart and the head. The potential complications of neurosurgery and of the sitting position in particular, have always made it appropriate to use extensive monitoring [2]. The standard equipment used by nearly all our respondents included an electrocardiogram for detecting rhythm disturbance, capnography with trend recording as a measure of adequate ventilation and an early detector of venous air embolism, intraarterial pressure for continuous accurate recording of arterial pressure and prompt detection of hypotension, and pulse oximetry as a indication of arterial oxygenation. Some of the additional monitoring techniques used for diagnosis and management of air embolism include Doppler ultrasound probe applied to the precordium and an oesophageal stethoscope. A catheter placed into the right atrium allows aspiration of an air embolism [5]. ACKNOWLEDGEMENTS We thank Dr J. Jenkinson, the Honorary Secretary of the Neurosurgical Anaesthetists' Travelling Club and Dr M. C. Clapham, Solihull Hospital, for statistical advice.
REFERENCES 1. Campkin TV. Posture and ventilation during posterior fossa and cervical operations. Current practice in the United Kingdom. British Journal of Anaesthesia 1981; 53: 881-884. 2. Broderick PM. The sitting position: monitoring, diagnosis and treatment of air embolism. In: Jewkes DA, ed. Balltire's Clinical Anaesthesiology, Volume 1, no. 2: Anaesthesia for Neurosurgery. London: Balliere Tindall, 1987; 419-440. 3. Shapiro HM, Drummond JC. Neurosurgical anesthesia and intracranial hypertension. In: Miller RD, ed. Anesthesia, 3rd Edn. New York: Churchill Livingstone, 1990; 1737-1789. 4. Cucchiara RF. Safety of sitting position. Anesthesiology 1984; 61: 790. 5. Bedford RF, Marshall WK, Butler A, Welsh JE. Cardiac catheters for diagnosis and treatment of venous air embolism. A prospective study in man. Journal of Neurosurgery 1981; 55: 610-614.
Downloaded from http://bja.oxfordjournals.org/ at Pennsylvania State University on May 25, 2015
number of centres which always used the sitting position for posterior fossa surgery and a significant increase in the use of the other positions. There was a significant reduction in the use of the sitting position for posterior cervical surgery. Several respondents commented that although the sitting position was retained as an option in their centres (i.e. the group which used all three positions), it was used only very occasionally. Among the 21 anaesthetists who routinely used the sitting position, 18 (86%) always used IPPV; one respondent (5%) used spontaneous respiration for posterior fossa surgery and two (10 %) used it for posterior cervical surgery. Among the 21 anaesthetists who always used the sitting position, all (100%) used an electrocardiogram, pulse oximeter and end-tidal carbon dioxide measurements and all but one (95%) used direct arterial pressure measurement. Fourteen (67 %) used a right atrial catheter, 13 (62%) a Doppler ultrasound probe over the precordium and 12 (57 %) used an oesophageal stethoscope, in addition to the other monitors; two (10%) of these anaesthetists also used pulmonary artery catheters, one (5 %) used auditory evoked potentials and one (5%) routinely measured arterial pressure with an oscillotonometer only.
The sitting position in neurosurgical anaesthesia: a survey of British practice in 199If R. J. ELTON AND R. S. C. HOWELL
SUMMARY
KEY WORDS Anaesthesia: neurosurgical. Position, effects. Position: sitting
The use of the sitting position for patients undergoing posterior fossa and cervical spinal surgery represents a unique physiological challenge and is associated with several important complications. In 1981, Campkin [1] reported that 19 (53%) of the 36 neurosurgical centres in the UK always used the sitting position for posterior fossa surgery and 11 (30%) always used it for posterior cervical spinal surgery. We set out to establish the extent of the use of the sitting position in the UK in 1991 and to compare this with the situation in 1981. METHODS AND RESULTS
At the end of 1991 we mailed a questionnaire with a reply paid envelope to all 160 members of the Neuroanaesthetists' Travelling Club, a UK society, the members of which have a major interest in the practice of anaesthesia for neurosurgery (the club has since been renamed the Neuroanaesthesia Society of Great Britain and Ireland). The respondents were asked to specify which position they currently used for patients undergoing posterior fossa or posterior cervical surgery, if they used spontaneous respiration or intermittent positive pressure ventilation (IPPV) and which monitoring techniques were used. We received 124 replies, a response rate of 78%, of which 109 replies were returned fully completed,
TABLE I. Patient pojttions used m neurosurgical centres for posterior fossa surgery and posterior cervical surgery m 1981 and 1991. * P < 0 05, ** P < 0.01 compared tvith 1981 Sitting posiuon always (" (%)) Posterior fossa surgery 1981 19 (53) 1991 8 (20)** Posterior cervical surgery 1981 11(31) 3(7)* 1991
Other positions always (" (%)) 13 (36) 22 (54) 17(47) 31 (76)**
All three positions (« (%)) 4(11) 11 (27)** 8(22) 7(17)
Total centres 36 41 36 41
R. J. ELTON, M.B., CH.B., F.R.C.A., R. S. C. HOWELL, M.B., B.S., D.OBST., R.C.O.G., F.R.C.A., Departments of Anaesthetics and
Neurosurgery, Walsgrave Hospital, Coventry, West Midlands CV2 2DX. Accepted for Publication: February 22, 1994. tThis paper was presented at the Registrars' Prize Meeting of the Midland Society of Anaesthetists in Birmingham in March 1992 and an abstract was published in the Midland Society of Anaesthetists Newsletter for Summer 1992. The data shown in the paper were used in a poster presentation at the Combined Meeting of the Neurosurgical Anaesthetists' Travelling Club and the American Society of Neurosurgical Anaesthesia and Critical Care in London, June 1992.
Downloaded from http://bja.oxfordjournals.org/ at Pennsylvania State University on May 25, 2015
A postal survey of 160 members of the Neurosurgical Anaesthetists' Travelling Club was conducted in 1991 to investigate the current use of the sitting position in neurosurgery. There was a 78% response rate; at least one reply was received from every neurosurgical centre in the UK. Patients were placed normally in the sitting position for posterior fossa surgery in eight (20%) of the centres, compared with 19 (53%) in 1981. For posterior cervical spinal surgery, only three (7%) centres routinely used the sitting position, compared with 11 (31%) in 1981. Thus in the period 1981-1991, the number of neurosurgical centres using the sitting position routinely, decreased by more than 50%. Current techniques of ventilation and monitoring for the sitting position are discussed briefly. (Br. J. Anaesth. 1994; 73: 247-248)
68 % of the original mailing. Replies were received from 41 centres, including all 39 in the UK and one each in Ireland and Hong Kong, which have been included in the analysis as they were considered to be representative of British practice. It was noted that 24 (15%) of the Club's members were not anaesthetists and that the non-responders were mainly from this group: we decided that as this questionnaire was not relevant to these individuals, it would be acceptable to proceed to analyse and draw conclusions from the questionnaires returned. From the replies the respondents were divided into three groups: (1) those who always used the sitting position; (2) those who always used other positions (prone or lateral) and never used the sitting position; (3) those who used any of the three positions, including the sitting position. As each anaesthetist's practice was usually the same as the others in the same centre, we aggregated the responses into their respective centres to facilitate close comparison with the situation in 1981. The chisquare test was used for statistical comparison between groups. P < 0.05 was considered statistically significant. The results are summarised in table I. Compared with 1981, there was a significant reduction in the
BRITISH JOURNAL OF ANAESTHESIA
248
COMMENT
The advantages of the sitting position are entirely surgical, in that it facilitates surgical access to some parts of the posterior fossa and can also lead to a reduction in the amount of venous bleeding during surgery. The disadvantages [2-4] are that the associated subatmospheric pressure in the veins at the base of the skull may encourage venous air embolism and that arterial hypotension may lead to a disproportionate reduction in cerebral blood flow because of the gravitational effect of the vertical
distance between the heart and the head. The potential complications of neurosurgery and of the sitting position in particular, have always made it appropriate to use extensive monitoring [2]. The standard equipment used by nearly all our respondents included an electrocardiogram for detecting rhythm disturbance, capnography with trend recording as a measure of adequate ventilation and an early detector of venous air embolism, intraarterial pressure for continuous accurate recording of arterial pressure and prompt detection of hypotension, and pulse oximetry as a indication of arterial oxygenation. Some of the additional monitoring techniques used for diagnosis and management of air embolism include Doppler ultrasound probe applied to the precordium and an oesophageal stethoscope. A catheter placed into the right atrium allows aspiration of an air embolism [5]. ACKNOWLEDGEMENTS We thank Dr J. Jenkinson, the Honorary Secretary of the Neurosurgical Anaesthetists' Travelling Club and Dr M. C. Clapham, Solihull Hospital, for statistical advice.
REFERENCES 1. Campkin TV. Posture and ventilation during posterior fossa and cervical operations. Current practice in the United Kingdom. British Journal of Anaesthesia 1981; 53: 881-884. 2. Broderick PM. The sitting position: monitoring, diagnosis and treatment of air embolism. In: Jewkes DA, ed. Balltire's Clinical Anaesthesiology, Volume 1, no. 2: Anaesthesia for Neurosurgery. London: Balliere Tindall, 1987; 419-440. 3. Shapiro HM, Drummond JC. Neurosurgical anesthesia and intracranial hypertension. In: Miller RD, ed. Anesthesia, 3rd Edn. New York: Churchill Livingstone, 1990; 1737-1789. 4. Cucchiara RF. Safety of sitting position. Anesthesiology 1984; 61: 790. 5. Bedford RF, Marshall WK, Butler A, Welsh JE. Cardiac catheters for diagnosis and treatment of venous air embolism. A prospective study in man. Journal of Neurosurgery 1981; 55: 610-614.
Downloaded from http://bja.oxfordjournals.org/ at Pennsylvania State University on May 25, 2015
number of centres which always used the sitting position for posterior fossa surgery and a significant increase in the use of the other positions. There was a significant reduction in the use of the sitting position for posterior cervical surgery. Several respondents commented that although the sitting position was retained as an option in their centres (i.e. the group which used all three positions), it was used only very occasionally. Among the 21 anaesthetists who routinely used the sitting position, 18 (86%) always used IPPV; one respondent (5%) used spontaneous respiration for posterior fossa surgery and two (10 %) used it for posterior cervical surgery. Among the 21 anaesthetists who always used the sitting position, all (100%) used an electrocardiogram, pulse oximeter and end-tidal carbon dioxide measurements and all but one (95%) used direct arterial pressure measurement. Fourteen (67 %) used a right atrial catheter, 13 (62%) a Doppler ultrasound probe over the precordium and 12 (57 %) used an oesophageal stethoscope, in addition to the other monitors; two (10%) of these anaesthetists also used pulmonary artery catheters, one (5 %) used auditory evoked potentials and one (5%) routinely measured arterial pressure with an oscillotonometer only.