Anaesth Intens Care (1991),19,369-372
Level of Consciousness on Arrival in the Recovery Room and the Development of Early Respiratory Morbidity S. M. PARR,* B. J. ROBINSON,t P. w. GLOVER:!: AND D. c. GALLETLY§ Section of Anaesthesia, Wellington School of Medicine, Wellington, New Zealand SUMMARY An audit review of 16,065 patients undergoing operative procedures under general anaesthesia was carried out to examine the relationship between early postoperative respiratory complications and the level of consciousness of patients on arrival in the recovery room. In patients aged over ten years, the incidence of respiratory complications was significantly (P < 0.005) related to the level ofconsciousness independant of ASA grade or age. Since the level ofconsciousness ofpatients arriving in the recovery room could be modified by changes to anaesthetic practice it is concluded that a significant reduction in respiratory complications might be possible if anaesthetists used general anaesthetic techniques which returned patients awake to the recovery room. Key Words: ANAESTHESIA: recovery, level of consciousness; COMPLICATIONS: respiratory
Many factors are associated with early postoperative arterial hypoxaemia. These include obesity, 1,2 high ASA grade,2 cigarette smoking,3 increasing age,2,4,6 endotracheal intubation 5 and prolonged duration of anaesthesia. 2Although these factors are not under the direct control of the anaesthetist it is possible that other aspects of anaesthetic care might influence postoperative respiratory function and could be modified by changes to anaesthetic practice. While a relationship seems intuitively likely, studies in adults have found no correlation between consciousness in the recovery room and postoperative hypoxaemia,2,6,7 although in children two studies have found a positive correlation. 8,9 In this present study, we examined the postoperative recovery audit data base of a large number of patients over a thirty-month period at Wellington Hospital to determine whether such a correlation existed. Because of the potentially confounding effect of age, ASA and operative influences, we examined the relationship for patient groups of similar age range and ASA status, and for fifteen commonly performed inpatient surgical categories, °B.M., F.c.Anaes., Anaesthetic Registrar. tB.Sc., M.Sc., Research FeUow. fM.B., Ch.B., F.F.A.R.A.C.S., Consultant Anaesthetist. §F.F.A.R.A.C.S., F.C.Anaes., Senior Lecturer. Address for Reprints: Dr. D. C. GaUetly, Section of Anaesthesia, Wellington School of Medicine, P.O. Box 7343, Wellington South, New Zealand. Accepted for publication April 3,
1991
Anaesthesia and Intensive Care. Vol. 19. No. 3, August. 1991
METHODS The computerised data base at Wellington consists of prospectively gathered demographic and surgical information, preoperative condition, drugs used, monitoring, and intraoperative problems, all of which are recorded by the attending anaesthetist. On transfer to the recovery room, the level of consciousness (recorded as awake, responsive only to verbal command, responsive only to physical stimulation or nonresponsive), degree of airway support required, presence of pain and any postoperative problems are recorded by recovery room nursing staff. In addition to other non-respiratory complications, nursing staff note the presence of: laryngospasm, bronchospasm, stridor, hypoventilation (s9 breaths/min), residual paralysis, airway obstruction, cyanosis, and the need for re-intubation or IPPV. Data from 16,065 patients undergoing general anaesthesia for gynaecological, general, ENT, ophthalmic and orthopaedic surgery were included in the analysis. Patients were excluded if the level of consciousness in the recovery room could be unrelated to the anaesthetic, or where level of consciousness was difficult to assess. These included those patients who had undergone cardiothoracic, major vascular, neurosurgery, paediatric patients under one year of age and those patients transferred directly to the intensive care unit. In order to examine only the influence of
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S. M. PARR ET AL.
10 9
9 7 % Patients with 6 Complications
% Patients with Complications
6
1
I.-Complications and ASA Grade. The frequency of patients having one or more respiratory complication in relation to ASA grade and level of consciousness on arrival in the recovery room. Level of consciousness: I = awake, 2 = responsive only to verbal command, 3 = responsive only to physical stimulation, 4 = unresponsive. FIGURE
1
FIGURE 2.-Complications and Age. The frequency of
patients having one or more respiratory complication in relation to age and level of consciousness on arrival in the recovery room. Level of consciosuness: 1 = awake, 2 = responsive only to verbal command, 3 = responsive only to physical stimulation, 4 = unresponsive.
general anaesthesia, those receiving general with patients ten years of age or younger, level of additional regional anaesthesia were excluded. consciousness correlated significantly (P < 0.005 The relationship between the level of for each) with respiratory complications in all other consciousness and the incidence of respiratory age categories. The effect of consciousness on complications within ASA grades and age groups respiratory complications appeared particularly were tested using the Mantel-Haenszel test. This marked for patients over the age of 70 years, almost test examines the trend between the proportion of 10% of these patients having a respiratory problem respiratory complications with increasing ASA if returned unresponsive. grade or age group. The relationships were also The relationship between level of consciousness examined using the Mantel-Haenszel test with and respiratory complications for fifteen common analysis stratifying for level of consciousness. inpatient operation categories was also examined. With the exception of those operations (dilatation RESULTS Of the 16,065 patients, 474 (2.95%) were and curettage, cystoscopy) where the overall recorded as having one or more respiratory incidence of respiratory complications was low, the problems while in the recovery room (mean data was again consistent with a positive duration of recovery for all patients 71 minutes). relationship existing between level of The most common problems were those related to consciousness and respiratory complications for hypoventilation, airway obstruction and residual each operation category. paralysis following the use of neuromuscular TABLE 1 blocking drugs (Table 1). Respiratory complications in the recovery With increasing ASA grade there was an room (n = 16,065) increasing frequency of respiratory complications (P < 0.001; stratified by level of consciousness). Percentage of Number of Figure 1 shows the proportion of patients with one patients patients or more complications according to ASA grade and level of consciousness on arrival. For each ASA Hypoventilation 1.05% 169 0.74% 119 category there was a significant (P < 0.001) Obstruction 0.61 % 98 positive correlation between consciousness and Laryngolbronchospasm Residual paralysis 0.57% 92 incidence of respiratory morbidity. 0.44% 70 The proportion of patients with respiratory Cyanosis Stridor 0.27% 43 problems increased with advancing age IPPY 0.22% 35 (P < 0.001); stratified by level of consciousness). Re-intubated 0.09% 15 The relationship between level of consciousness Total 2.95% 474 and respiratory complications for different age (Patients with one or more respiratory complication.) groups is shown in Figure 2. With the exception of Anaesthesia and Intensive Care. Vol. 19. No. 3. August. 1991
CONSCIOUSNESS AND RESPIRATORY MORBIDITY DISCUSSION
The recovery period following a general anaesthetic has been divided into three phases; immediate, intermediate and 10ng-term. IO Immediate recovery has always been associated with a significant morbidity and mortality, lithe commonest preventable complication being respiratory obstruction. In 1947 Ruth and colleagues found that of 307 postoperative deaths, almost half were classified as preventable and in 63% of these, death was primarily a result of a combination of inadequate nursing care and respiratory obstruction in the immediate postoperative period. 12 In a more recent review of anaesthetic accidents reported to the medical Defence Union in the United Kingdom from 1970 to 1977 there were 33 cases of death or cerebral damage in the early recovery period; 29 of these were as a result of either an obstructed airway or respiratory depression. 13 In a prospective review of anaesthetic complications in France from 1978 to 1982, half the deaths and cases of coma totally attributable to anaesthesia were due to postoperative respiratory depression. 14 Studies of postoperative morbidity quote a 2 to 3% incidence of adverse respiratory events occurring in the recovery room,15.18 respiratory depression and obstruction being the most frequently observed problems. The results of our study, in terms of the overall incidence of respiratory complications (2.95%), and the distribution of complications are consistent with these observations. With the introduction of pulse oximetry, it has been appreciated that the low incidence of clinically apparent respiratory complications, as determined in this present study, make up only a small portion of those patients with recovery room hypoxaemia. Studies of oxygenation during patient transfer indicate that a significant number of patients arrive in the recovery room hypoxaemic. Approximately 30% of healthy adult l ,21 and pediatric8,9.19,20 patients develop arterial oxygen saturations of less than 90% during transfer from theatre to the recovery room despite breathing 100% oxygen before leaving theatre. In the recovery room, hypoxaemia (Sp02 < 90%) has a range of reported incidences from less than 10%2,6 to over 40%.4,9 Our results suggest that patients who arrive in the recovery room not having regained full consciousness have a higher incidence of respiratory complications than patients being returned awake. This relationship was observed irrespective of patient age over ten years and for each ASA category. Those aged over 70 years and those in ASA category 3-5 arriving in the recovery room unresponsive demonstrated an incidence of respiratory complications of approximately 9%. It Anaesthesia and Intensive Care, Vol. 19. No. 3, August, 1991
371
is notable however, that all patients, regardless of age or ASA category, who arrived in the recovery room awake demonstrated a uniformly low incidence of respiratory complications ofO. 7-1.8%. The relationship between state of consciousness and respiratory morbidity was less apparent in children and in patients undergoing minor procedures. This, in addition to inadequate case numbers, may explain why some previous studies have found no such relationship. Although conclusions drawn from retrospective analysis of audit data must be viewed with caution, our findings are consistent with the known respiratory effects of central nervous system depressants and with studies demonstrating fewer hypoxaemic episodes after regional, in contrast to full general anaesthesia. 22 Although certainly many other factors are important in the genesis of respiratory complications, our data suggests that if all patients were returned to the recovery room fully awake, the potential reduction in the incidence of respiratory problems is up to 55% (from 474 to 209). Any alteration to anaesthetic practice, which enabled patients to arrive in the recovery room awake however, could introduce difficulties and some potential hazards. The anaesthetist might be tempted to discontinue or reduce anaesthetic delivery while surgery is in progress (thereby increasing the possibility of awareness) and the sparing use of sedative opioids might cause awake patients to be returned to the recovery room in severe pain. A balance therefore would need to be achieved between pain, awareness and level of consciousness. In conclusion, a review of 16,065 patients undergoing general anaesthesia showed that patients returned to the recovery room unresponsive demonstrated a higher incidence of early postoperative respiratory complications in contrast to similar patients returned awake. We therefore suggest that the routine use of techniques which return patients awake to the recovery room could lead to a major reduction in early postoperative respiratory morbidity. ACKNOWLEDGEMENTS
This work was supported by the Wellington Anaesthesia Trust, leI New Zealand Limited, Janssen Pharmaceutica and Pharmaco (N.Z.) Ltd. We thank Barbara Kolacynski and the recovery ward staff for their co-operation in the conduct of this audit. REFERENCES
1. TyIer IL, Tantisira B, Winter PM, Motoyama EK. Continuous monitoring of arterial oxygen with pulse oximetry during transfer to the recovery room. Anesth Analg 1985; 64: 1108-1112.
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s. M. PARR ET AL.
2. Morris RW, Buschman A, Warren DL, Philip JH, Raemer DB. The prevalence ofhypoxemia detected by pulse oximetry during recovery from anesthesia. J Clin Monit 1988; 4: 16-20. 3. Tait AR, Kyff JV, Crider B, Santibhavank V, Learned D, Finch JS. Changes in arterial oxygen saturation in cigarette smokers following general anaesthesia. Can J Anaesth 1990; 37: 423-428. 4. Canet J, Ricos M, Vidal F. Early postoperative arterial oxygen desaturation; determining factors and response to oxygen therapy. Anesth Analg 1989; 69:207-212. 5. Tomkins DP, Gaukroger P. Oxygen saturation in children following general anaesthesia. Anaesth Intens Care 1987; 15: 111. 6. Scott Murray R, Raemer DB, Morris RW. Supplemental oxygen after ambulatory surgical procedures. Anesth Analg 1988; 67:967-970. 7. Dale S, Rowbotham DJ, Nimmo WS. Oxygen saturation in the recovery room. Br J Anaesth 1988; 60:341(P). 8. Motoyama EK, Glazener CH. Hypoxemia after general anesthesia in children. Anesth Analg 1986; 65:267-272. 9. Laycock GJA, McNicol LR. Hypoxaemia during recovery from anaesthesia - an audit of children after general anaesthesia for routine elective surgery. Anaesthesia 1988; 43:984-987. 10. Stewa~ DJ, Volgyesi G. Stabilometry: A new tool for the measurement of recovery following general anaesthesia for out-patients. Canad Anaesth Soc J 1978; 25:4-6. 11. Lowenthal PJ, Russell AS. Recovery room: Life saving and economical. Anesthesiology 1951; 12:470-476.
12. Ruth HS, Haugen FP, Grove DD, Anesthesia Study Commission; Findings of eleven years' activity. JAMA 1947; 135:881-884. 13. Utting JE, Gray TC, Shelley FC. Human misadventure in anaesthesia. Canad Anaesth Soc J 1979; 26:472-478. 14. Tiret L, Desmonts JM, Hatton F, Vourc'h G. Complications associated with anaesthesia - a prospective survey in France. Can Anaesth Soc J 1986; 33:336-334. 15. Beard MB, Jick H, Walker AM. Adverse respiratory events occurring in the recovery room after general anesthesia. Anesthesiology 1986; 64:269-272. 16. Zelcer J, Wells DG. Anaesthetic-related recovery room complications. Anaesth Intens Care 1987; 15:168-174. 17. Farman JV. The work of the recovery room. Br J Hosp Med 1978; 19:606-616. 18. Eltringham RJ. Complications in the recovery room. J Roy Soc Med 1979; 72:278-280. 19. Chripko D, Bevan JC, Archer DP, Bherer N. Decreases in arterial oxygen saturation in paediatric outpatients during transfer to the postanaesthetic recovery room. Can J Anaesth 1989; 36: 128-132. 20. Pullerits J, Burrows FA, Roy WL. Arterial desaturation in healthy children during transfer to the recovery room. CanJ Anaesth 1987; 34:470-472. 21. Smith DC, Crul JF. Early postoperative hypoxia during transport. Br J Anaesth 1988; 61 :625-627. 22. McKenzie PJ, Wishart HY, Dewar KMS, Gray I, Smith G. Comparison of the effects of spinal anaesthesia and general anaesthesia on postoperative oxygenation and perioperative mortality. Br J Anaesth 1980; 52:49-54.
Anaesthesia and Intensive Care. Vol. 19, No. 3, August, 1991
Level of Consciousness on Arrival in the Recovery Room and the Development of Early Respiratory Morbidity S. M. PARR,* B. J. ROBINSON,t P. w. GLOVER:!: AND D. c. GALLETLY§ Section of Anaesthesia, Wellington School of Medicine, Wellington, New Zealand SUMMARY An audit review of 16,065 patients undergoing operative procedures under general anaesthesia was carried out to examine the relationship between early postoperative respiratory complications and the level of consciousness of patients on arrival in the recovery room. In patients aged over ten years, the incidence of respiratory complications was significantly (P < 0.005) related to the level ofconsciousness independant of ASA grade or age. Since the level ofconsciousness ofpatients arriving in the recovery room could be modified by changes to anaesthetic practice it is concluded that a significant reduction in respiratory complications might be possible if anaesthetists used general anaesthetic techniques which returned patients awake to the recovery room. Key Words: ANAESTHESIA: recovery, level of consciousness; COMPLICATIONS: respiratory
Many factors are associated with early postoperative arterial hypoxaemia. These include obesity, 1,2 high ASA grade,2 cigarette smoking,3 increasing age,2,4,6 endotracheal intubation 5 and prolonged duration of anaesthesia. 2Although these factors are not under the direct control of the anaesthetist it is possible that other aspects of anaesthetic care might influence postoperative respiratory function and could be modified by changes to anaesthetic practice. While a relationship seems intuitively likely, studies in adults have found no correlation between consciousness in the recovery room and postoperative hypoxaemia,2,6,7 although in children two studies have found a positive correlation. 8,9 In this present study, we examined the postoperative recovery audit data base of a large number of patients over a thirty-month period at Wellington Hospital to determine whether such a correlation existed. Because of the potentially confounding effect of age, ASA and operative influences, we examined the relationship for patient groups of similar age range and ASA status, and for fifteen commonly performed inpatient surgical categories, °B.M., F.c.Anaes., Anaesthetic Registrar. tB.Sc., M.Sc., Research FeUow. fM.B., Ch.B., F.F.A.R.A.C.S., Consultant Anaesthetist. §F.F.A.R.A.C.S., F.C.Anaes., Senior Lecturer. Address for Reprints: Dr. D. C. GaUetly, Section of Anaesthesia, Wellington School of Medicine, P.O. Box 7343, Wellington South, New Zealand. Accepted for publication April 3,
1991
Anaesthesia and Intensive Care. Vol. 19. No. 3, August. 1991
METHODS The computerised data base at Wellington consists of prospectively gathered demographic and surgical information, preoperative condition, drugs used, monitoring, and intraoperative problems, all of which are recorded by the attending anaesthetist. On transfer to the recovery room, the level of consciousness (recorded as awake, responsive only to verbal command, responsive only to physical stimulation or nonresponsive), degree of airway support required, presence of pain and any postoperative problems are recorded by recovery room nursing staff. In addition to other non-respiratory complications, nursing staff note the presence of: laryngospasm, bronchospasm, stridor, hypoventilation (s9 breaths/min), residual paralysis, airway obstruction, cyanosis, and the need for re-intubation or IPPV. Data from 16,065 patients undergoing general anaesthesia for gynaecological, general, ENT, ophthalmic and orthopaedic surgery were included in the analysis. Patients were excluded if the level of consciousness in the recovery room could be unrelated to the anaesthetic, or where level of consciousness was difficult to assess. These included those patients who had undergone cardiothoracic, major vascular, neurosurgery, paediatric patients under one year of age and those patients transferred directly to the intensive care unit. In order to examine only the influence of
370
S. M. PARR ET AL.
10 9
9 7 % Patients with 6 Complications
% Patients with Complications
6
1
I.-Complications and ASA Grade. The frequency of patients having one or more respiratory complication in relation to ASA grade and level of consciousness on arrival in the recovery room. Level of consciousness: I = awake, 2 = responsive only to verbal command, 3 = responsive only to physical stimulation, 4 = unresponsive. FIGURE
1
FIGURE 2.-Complications and Age. The frequency of
patients having one or more respiratory complication in relation to age and level of consciousness on arrival in the recovery room. Level of consciosuness: 1 = awake, 2 = responsive only to verbal command, 3 = responsive only to physical stimulation, 4 = unresponsive.
general anaesthesia, those receiving general with patients ten years of age or younger, level of additional regional anaesthesia were excluded. consciousness correlated significantly (P < 0.005 The relationship between the level of for each) with respiratory complications in all other consciousness and the incidence of respiratory age categories. The effect of consciousness on complications within ASA grades and age groups respiratory complications appeared particularly were tested using the Mantel-Haenszel test. This marked for patients over the age of 70 years, almost test examines the trend between the proportion of 10% of these patients having a respiratory problem respiratory complications with increasing ASA if returned unresponsive. grade or age group. The relationships were also The relationship between level of consciousness examined using the Mantel-Haenszel test with and respiratory complications for fifteen common analysis stratifying for level of consciousness. inpatient operation categories was also examined. With the exception of those operations (dilatation RESULTS Of the 16,065 patients, 474 (2.95%) were and curettage, cystoscopy) where the overall recorded as having one or more respiratory incidence of respiratory complications was low, the problems while in the recovery room (mean data was again consistent with a positive duration of recovery for all patients 71 minutes). relationship existing between level of The most common problems were those related to consciousness and respiratory complications for hypoventilation, airway obstruction and residual each operation category. paralysis following the use of neuromuscular TABLE 1 blocking drugs (Table 1). Respiratory complications in the recovery With increasing ASA grade there was an room (n = 16,065) increasing frequency of respiratory complications (P < 0.001; stratified by level of consciousness). Percentage of Number of Figure 1 shows the proportion of patients with one patients patients or more complications according to ASA grade and level of consciousness on arrival. For each ASA Hypoventilation 1.05% 169 0.74% 119 category there was a significant (P < 0.001) Obstruction 0.61 % 98 positive correlation between consciousness and Laryngolbronchospasm Residual paralysis 0.57% 92 incidence of respiratory morbidity. 0.44% 70 The proportion of patients with respiratory Cyanosis Stridor 0.27% 43 problems increased with advancing age IPPY 0.22% 35 (P < 0.001); stratified by level of consciousness). Re-intubated 0.09% 15 The relationship between level of consciousness Total 2.95% 474 and respiratory complications for different age (Patients with one or more respiratory complication.) groups is shown in Figure 2. With the exception of Anaesthesia and Intensive Care. Vol. 19. No. 3. August. 1991
CONSCIOUSNESS AND RESPIRATORY MORBIDITY DISCUSSION
The recovery period following a general anaesthetic has been divided into three phases; immediate, intermediate and 10ng-term. IO Immediate recovery has always been associated with a significant morbidity and mortality, lithe commonest preventable complication being respiratory obstruction. In 1947 Ruth and colleagues found that of 307 postoperative deaths, almost half were classified as preventable and in 63% of these, death was primarily a result of a combination of inadequate nursing care and respiratory obstruction in the immediate postoperative period. 12 In a more recent review of anaesthetic accidents reported to the medical Defence Union in the United Kingdom from 1970 to 1977 there were 33 cases of death or cerebral damage in the early recovery period; 29 of these were as a result of either an obstructed airway or respiratory depression. 13 In a prospective review of anaesthetic complications in France from 1978 to 1982, half the deaths and cases of coma totally attributable to anaesthesia were due to postoperative respiratory depression. 14 Studies of postoperative morbidity quote a 2 to 3% incidence of adverse respiratory events occurring in the recovery room,15.18 respiratory depression and obstruction being the most frequently observed problems. The results of our study, in terms of the overall incidence of respiratory complications (2.95%), and the distribution of complications are consistent with these observations. With the introduction of pulse oximetry, it has been appreciated that the low incidence of clinically apparent respiratory complications, as determined in this present study, make up only a small portion of those patients with recovery room hypoxaemia. Studies of oxygenation during patient transfer indicate that a significant number of patients arrive in the recovery room hypoxaemic. Approximately 30% of healthy adult l ,21 and pediatric8,9.19,20 patients develop arterial oxygen saturations of less than 90% during transfer from theatre to the recovery room despite breathing 100% oxygen before leaving theatre. In the recovery room, hypoxaemia (Sp02 < 90%) has a range of reported incidences from less than 10%2,6 to over 40%.4,9 Our results suggest that patients who arrive in the recovery room not having regained full consciousness have a higher incidence of respiratory complications than patients being returned awake. This relationship was observed irrespective of patient age over ten years and for each ASA category. Those aged over 70 years and those in ASA category 3-5 arriving in the recovery room unresponsive demonstrated an incidence of respiratory complications of approximately 9%. It Anaesthesia and Intensive Care, Vol. 19. No. 3, August, 1991
371
is notable however, that all patients, regardless of age or ASA category, who arrived in the recovery room awake demonstrated a uniformly low incidence of respiratory complications ofO. 7-1.8%. The relationship between state of consciousness and respiratory morbidity was less apparent in children and in patients undergoing minor procedures. This, in addition to inadequate case numbers, may explain why some previous studies have found no such relationship. Although conclusions drawn from retrospective analysis of audit data must be viewed with caution, our findings are consistent with the known respiratory effects of central nervous system depressants and with studies demonstrating fewer hypoxaemic episodes after regional, in contrast to full general anaesthesia. 22 Although certainly many other factors are important in the genesis of respiratory complications, our data suggests that if all patients were returned to the recovery room fully awake, the potential reduction in the incidence of respiratory problems is up to 55% (from 474 to 209). Any alteration to anaesthetic practice, which enabled patients to arrive in the recovery room awake however, could introduce difficulties and some potential hazards. The anaesthetist might be tempted to discontinue or reduce anaesthetic delivery while surgery is in progress (thereby increasing the possibility of awareness) and the sparing use of sedative opioids might cause awake patients to be returned to the recovery room in severe pain. A balance therefore would need to be achieved between pain, awareness and level of consciousness. In conclusion, a review of 16,065 patients undergoing general anaesthesia showed that patients returned to the recovery room unresponsive demonstrated a higher incidence of early postoperative respiratory complications in contrast to similar patients returned awake. We therefore suggest that the routine use of techniques which return patients awake to the recovery room could lead to a major reduction in early postoperative respiratory morbidity. ACKNOWLEDGEMENTS
This work was supported by the Wellington Anaesthesia Trust, leI New Zealand Limited, Janssen Pharmaceutica and Pharmaco (N.Z.) Ltd. We thank Barbara Kolacynski and the recovery ward staff for their co-operation in the conduct of this audit. REFERENCES
1. TyIer IL, Tantisira B, Winter PM, Motoyama EK. Continuous monitoring of arterial oxygen with pulse oximetry during transfer to the recovery room. Anesth Analg 1985; 64: 1108-1112.
372
s. M. PARR ET AL.
2. Morris RW, Buschman A, Warren DL, Philip JH, Raemer DB. The prevalence ofhypoxemia detected by pulse oximetry during recovery from anesthesia. J Clin Monit 1988; 4: 16-20. 3. Tait AR, Kyff JV, Crider B, Santibhavank V, Learned D, Finch JS. Changes in arterial oxygen saturation in cigarette smokers following general anaesthesia. Can J Anaesth 1990; 37: 423-428. 4. Canet J, Ricos M, Vidal F. Early postoperative arterial oxygen desaturation; determining factors and response to oxygen therapy. Anesth Analg 1989; 69:207-212. 5. Tomkins DP, Gaukroger P. Oxygen saturation in children following general anaesthesia. Anaesth Intens Care 1987; 15: 111. 6. Scott Murray R, Raemer DB, Morris RW. Supplemental oxygen after ambulatory surgical procedures. Anesth Analg 1988; 67:967-970. 7. Dale S, Rowbotham DJ, Nimmo WS. Oxygen saturation in the recovery room. Br J Anaesth 1988; 60:341(P). 8. Motoyama EK, Glazener CH. Hypoxemia after general anesthesia in children. Anesth Analg 1986; 65:267-272. 9. Laycock GJA, McNicol LR. Hypoxaemia during recovery from anaesthesia - an audit of children after general anaesthesia for routine elective surgery. Anaesthesia 1988; 43:984-987. 10. Stewa~ DJ, Volgyesi G. Stabilometry: A new tool for the measurement of recovery following general anaesthesia for out-patients. Canad Anaesth Soc J 1978; 25:4-6. 11. Lowenthal PJ, Russell AS. Recovery room: Life saving and economical. Anesthesiology 1951; 12:470-476.
12. Ruth HS, Haugen FP, Grove DD, Anesthesia Study Commission; Findings of eleven years' activity. JAMA 1947; 135:881-884. 13. Utting JE, Gray TC, Shelley FC. Human misadventure in anaesthesia. Canad Anaesth Soc J 1979; 26:472-478. 14. Tiret L, Desmonts JM, Hatton F, Vourc'h G. Complications associated with anaesthesia - a prospective survey in France. Can Anaesth Soc J 1986; 33:336-334. 15. Beard MB, Jick H, Walker AM. Adverse respiratory events occurring in the recovery room after general anesthesia. Anesthesiology 1986; 64:269-272. 16. Zelcer J, Wells DG. Anaesthetic-related recovery room complications. Anaesth Intens Care 1987; 15:168-174. 17. Farman JV. The work of the recovery room. Br J Hosp Med 1978; 19:606-616. 18. Eltringham RJ. Complications in the recovery room. J Roy Soc Med 1979; 72:278-280. 19. Chripko D, Bevan JC, Archer DP, Bherer N. Decreases in arterial oxygen saturation in paediatric outpatients during transfer to the postanaesthetic recovery room. Can J Anaesth 1989; 36: 128-132. 20. Pullerits J, Burrows FA, Roy WL. Arterial desaturation in healthy children during transfer to the recovery room. CanJ Anaesth 1987; 34:470-472. 21. Smith DC, Crul JF. Early postoperative hypoxia during transport. Br J Anaesth 1988; 61 :625-627. 22. McKenzie PJ, Wishart HY, Dewar KMS, Gray I, Smith G. Comparison of the effects of spinal anaesthesia and general anaesthesia on postoperative oxygenation and perioperative mortality. Br J Anaesth 1980; 52:49-54.
Anaesthesia and Intensive Care. Vol. 19, No. 3, August, 1991
