276
J. R. BRIMACOMBE
intubation is more appropriate if there is a risk of regurgitation. Payne has clearly shown that despite an unobstructed airway the oesophagus can occasionally be seen through the LMA using a fibreoptic laryngoscope. 3 Swallowing air during balanced regional anaesthesia with a LMA has not previously been reported and was only noted in this patient because the length of the procedure permitted gastric dilatation to occur. A light general anaesthetic, which has not obtunded the swallowing reflex, combined with a misplaced LMA, in which the oesophagus and laryngeal inlet are communicating, can allow this. This case demonstrates a rare but potentially
serious problem which can arise during light anaesthesia with a LMA. It also re-emphasises that the LMA does not reliably separate the respiratory from the gastrointestinal tracts and that constant vigilance is required during its use. REFERENCES I. Brain AI1. Laryngeal mask and trauma to uvula (a
reply to a letter). Anaesthesia 1989; 44: 1014-5. 2. Murdoch L, Rubin A. Use of the Brain laryngeal mask in balanced regional anaesthesia. Anaesthesia 1989; 44:616. 3. Payne J. The use of the fibreoptic laryngoscope to confirm the position of the laryngeal mask. Anaesthesia 1989; 44:865.
Intra- and Postoperative Anaesthetic Management of an Opioid Addict Undergoing Caesarean Section R. K. BOYLE*
Department of Anaesthesia, The Royal Women's Hospital, Brisbane, Queensland Key Words: ANALGESIA, OBSTETRIC: PCA, persistent uterine constriction, opioid addict
Drug addiction in the parturient harms mother and baby. Recognition and management of opioid abuse early in pregnancy may prevent some problems but other complications may arise unexpectedly. This report documents the avoidance of some potential difficulties and the mismanagement of an unpredicted problem during caesarean section in an opioid addict. CASE REPORT A 23-year-old, 58-kg woman, gravida 5, para 2, terminations 2, presented in labour at thirty weeks' gestation. She was transferred ninety-five kilometres by air ambulance helicopter with a twelve-hour history of moderate uterine contractions. The patient had used intravenous heroin until the seventeenth week of her pregnancy, when she changed to oral methadone 25 mg per day. Drug treatment of her premature labour included intramuscular dexamethasone 20 mg, then two daily doses of betamethasone 12 mg and intravenous salbutamol 3.3 f..lg.min - I increasing to *F.F.A.R.A.C.S., Staff Anaesthetist. Address for Reprints: Dr. R. Boyle, Department of Anaesthesia, Royal Women's Hospital, P.O. Royal Brisbane Hospital, Queensland 4029, Australia. Accepted for publication November 26, 1990
6.7 f..lg.min - I until maternal headache, tachycardia and foetal tachycardia occurred. Intravenous fluids were glucose-free and restricted to less than two litres per day. Sixteen hours after uterine contractions ceased, salbutamol was changed to oral administration, 3 mg having been administered over fifteen hours. Oral salbutamol was continued for ten days, 24 mg per day in divided doses. Bed rest proved difficult for this patient, who persuaded her husband and other patients to push her wheelchair outside the hospital so that she could continue to smoke. Laboratory assessment No abnormality was detected in serial serum electrolytes, platelets, white cells, liver function, creatinine, blood urea, and glucose. Cultures from high vaginal swabs grew normal vaginal flora with no haemolytic streptococcus B. A normochromic normocytic anaemia, haemoglobin 8.2 g/dl was noted. Twenty-four hours after cessation of parenteral salbutamol, two units of packed red cells were slowly infused. Antibodies were detected to Rubella and Hepatitis C viral antigen, but not to Hepatitis B, or Human Immunodeficiency viruses. A urinary drug screen was not performed. Anaesthesia and Intensive Care. Vol. 19, No. 2, May, 1991
277
CASE REPORT
The delivery and neonatal status At thirty-two weeks' gestation, labour recommenced. Examination revealed a footling breech presentation, a 7 cm dilated cervix and bulging forewaters. It was decided to deliver the infant by caesarean section under a general anaesthetic which consisted of thiopentone 8 mg.kg -!, suxamethonium, atracurium, 50% nitrous oxide in oxygen, and enflurane 2.5% until the umbilical cord was clamped. The technique included preoperative sodium citrate, left uterine displacement, preoxygenation, rapid sequence induction, cricoid pressure, tracheal intubation and intermittent positive pressure ventilation to maintain end-tidal CO 2 at 32 mmHg. A Pfannenstiel incision, then transverse lower uterine incision were performed. After membranes were ruptured, one infant leg was found flexed at the hip and knee, the other extended and surrounded by a constriction ring of uterine muscle. This persisted despite an inspired concentration of enflurane 2.5%. The uterine incision was extended vertically in a l-fashion before the trunk and head of the infant could be extracted. Uterine-incision to delivery time was eight minutes. Blood loss was estimated at 600 to 800 ml. The infant was flaccid, apnoeic, and had a heart rate of 70 per minute. The Apgar score was 3 at 1 minute. The infant's trachea was intubated and 100% oxygen given by intermittent positive pressure ventilation. The heart rate increased to 160 per minute and limbs became active. The Apgar score increased to 8 at 5 minutes, and within twenty minutes of delivery, the infant was extubated. Extensive bruising of the left leg was present. Birth weight was 1990 g, which was between the fiftieth and seventieth centiles for 32 weeks gestation. The baby required an intravenous 10% dextrose bolus in the first two hours, and became jaundiced with serum bilirubin 13 J,lmol.l-! on the fourth day. Nasogastric feeds and bottle feeds were established by day 2. No intracranial haemorrhages were demonstrated by ultrasound. The cerebral ventricles were normal in TABLE 1 PCA use during loading phase 2 Hours after operation Morphine requirement (mg/hr) 15 Demands per hr 7 Successful demands per hr 6 Respiratory rate (per min) 18 Cumulative dose morphine (mg) 30 Anaesthesia and Intensive Care. Vol. 19. No. 2. May. 1991
4
6
16 3
10
3
1
18 80
20 110
size and configuration. No signs of ne onataI opioid withdrawal occurred and the infant was discharged on day 11, weighing 1860 g. Postoperative analgesia Postoperative analgesia was provided by patientadministered intravenous boluses of morphine with a background infusion of 3 mg/hour. The method of use of patient-controlled analgesia, PCA, in this opioid addict is shown in Tables 1 and 2. No oral methadone was administered until bowel sounds became audible postoperatively. 1 Loading phase Initially the bolus dose was doubled because of persistence of severe pain, with the number of unsuccessful demands exceeding successful demands (Table 1).
2. Maintenance phase The background infusion was then decreased to 1.5 mg/hr, to allow ambulation while preventing symptoms of opioid withdrawal. Once a consistent reduction in hourly demand rate occurred, the morphine infusion was discontinued. (Table 2) Oral methadone was recommenced thirty-six hours postoperatively. DISCUSSION
This patient's outcome was improved by regular counselling, frequent antenatal obstetric review, and the substitution of oral methadone for selfadministered intravenous heroin. 1. Drug dependence The pregnant opioid addict is often malnourished, with suppressed pituitary adrenocorticotrophic hormone, and adrenocortical function. Common infective sequelae of intravenous drug abuse include cellulitis, superficial abscesses, septic phlebitis, tetanus. bacterial pneumonia, foreign body emboli, bacterial endocarditis. Pulmonary hypertension or acute pulmonary oedema may occur in the addicted parturient.! Opioid addiction produces up to a threefold TABLE 2 PCA use during maintenance phase Hours after operation Morphine requirement (mg/hr) Demands per hr Successful demands per hr Respiratory rate (per min) Cumu~ative dose morphine (mg)
8
12
16
20
9 6 5 6 2 2 3 2 1 2 3 18 18 16 16
158 178 202 238
278
R. K.
BOYLE
foetal manipulation. Unfortunately the general anaesthetic failed to achieve the required uterine relaxation and probably contributed to early neonatal depression. Volatile anaesthetics depress uterine contractility in proportion to the depth of anaesthesia. 9 Resting uterine tone is little altered at 0.5 MAC and haemorrhage from the placental site is unlikely. At 1 to 1.5 MAC, uterine tone, contractility and uterine vascular resistance are reduced and uterine perfusion increases. These concentrations are normally recommended for intra-uterine manipulation. At 2 MAC and larger doses there lU"ede.creases in maternal uterine perfusion and in foetal cardiac output, heart rate, base excess and oxygen saturation. 10 Excessive bleeding may occur after placental separation. It is uncertain why localised uterine constriction persisted. The 'constriction ring' may have been undilated cervix. Smooth muscle constitutes only 10% to 15% of total cervical tissue in most women, II the remainder are collagen and glycosaminoglycans. Therefore, whil~ the potent inhalational agents can achieve profound uterine relaxation, they may provide only limited cervical relaxation. In summary, general anaesthesia did not guarantee ideal conditions for abdominal delivery of a breech infant, but the excessive doses of general anaesthetics contributed to neontal depression (3 MAC enflurane,12,13 thiopentone 8 mg.kg- I , and foetal equilibration with nitrous oxide l4 subsequent to the long induction-to-delivery interval). 3. Postoperative analgesia for a methadone user Analgesia duration and dose cannot be preformulated according to the type of surgery undergone. 15 With this patient's history of opioid abuse, prior selection of an effective post-caesarean 2. The choice of general rather than regional analgesia regime was both inadvisable and anaesthesia Breech presentation occurs more frequently with impossible. Not only was a minimum analgesia increasing prematurity which carries its own high plasma concentration or other therapeutic endneonatal mortality rate. For vaginal delivery of point unpredictable, but also an effect other than breech, regional conduction techniques are the extinction of pain might have been demanded. preferable to general anaesthesia. 5 Properly The hourly nursing assessment of vital signs, conducted epidural analgesia avoids maternal and mental state, pain and analgesia use would readily foetal depression from parenteral opioids, which is have detected self-overdose with PCA. In addition analgesia supply and demand were important to the premature infant with respiratory sensitivity, underdeveloped blood brain barrier quantified by the PCA memory. For instance, an objective indication that the initial demand dose and impaired hepatic and renal clearance. In this patient a rapid induction of general was too small was the disparity between requested anaesthesia was chosen in view of the footling and satisfied demands. As in other studies, mean breech presentation, bulging forewaters and active hourly demand rates showed more detail than total labour, imminent membrane rupture and possible cumulative dose of opioid. 16 In summary, this case report describes the cord prolapse. In addition, the inhalational agent was expected to offer the potential for intrauterine persistence of a uterine constriction ring under
increase in perinatal mortality. Meconium aspiration, a high incidence of premature rupture of the membranes and premature labour, are associated with 50% of the foetal deaths. During pregnancy, foetal hypoxia and hypercarbia, during maternal opioid overdose, correlate with an increased incidence of congenital anomalies. A heroin addict may have repeated withdrawal throughout the pregnancy depending on availability and quality of her supply. During withdrawal, uterine contractions can occur and interfere with placental perfusion or progress to premature labour of short duration. Maternal withdrawal also carries the risk of foetal withdrawal, leading to foetal hyperactivity, increased oxygen consumption and possibly to _foetal_hJpoxia. Though this patient was still undernourished and anaemic, better obstetric care and neonatal monitoring were achieved after the change from parenteral heroin to oral methadone. The daily dose of methadone is important, correlating with the severity of neonatal withdrawal after delivery. Madden recommends 20 mg or less per day but cautions against too rapid detoxification and foetal distress. 2 Factors statistically associated with premature labour and present in this patient were anaemia and a urinary infection prior to admission. The pregnancy was prolonged to 32 weeks' gestation following treatment of anaemia, maternal infection and tocolysis, and avoidance of sideeffects deleterious to mother and infant.3 Dexamethasone probably accelerated in utero biochemical maturation of this baby's lungs. 4 The choice of dexamethasone or betamethasone over cortisol or prednisolone is based on greater in vitro placental extraction of the latter,5 but this, and the usefulness of steroids, are still controversia1. 6,7
Anaesthesia and Intensive Care. Vol. 19, No. 2, May, 1991
CASE REPORT
general anaesthesia and the successful use of postoperative PCA in a drug addict. REFERENCES
I. Rolbin SH, Rolbin SB. Drug addiction: anaesthetic considerations for the mother foetus and newborn. In: Obstetric anaesthesia: the complicated patient. James F, Wheeler AS, eds. FA Davis Co, Philadelphia 1982; 319-322. 2. Madden JD. Problems pertaining to the care of the newborn infants of drug-addicted women. J Reprod Med 1978; 20:303-306. 3. Spiel man FJ, Herbert W. Maternal cardiovascular effects of drugs that alter uterine activity. Obstet Gynecol Surv 1988; 43: 516-522. 4. Doyle LW, Kitchen WH et al. Effects of antenatal steroid therapy on mortality and morbidity in very low birthweight infants. J Pediat 1986, 108:287-292. 5. Blanford B, Pearson B, Murphy M. In vitro metabolism of prednisonlone, dexamethasome, betametasone and cortisol by the human placenta. Am J Obstet Gynecol 1977; 127:264-267. 6. Levitz M, Jansen V, Davis J. The transfer and metabolism of corticosteroids in the perfused human placenta. Am J Obstet Gynecol 1978; 132:363-366. 7. Avery ME, Aylward G, Creasy R, Little B, Stripp B. Update on prenatal steroids for prevention of respiratory distress. Report of a conference - Sept 26-28, 1985. Am J Ob stet Gynecol 1986; 155:2-5.
279
8. Breeson A, Kovacs G, Pickles B, Hill J. Extradural analgesia: the preferred method of analgesia for vaginal breech delivery. Br J Anaesth 1978;50: 1227-1229. 9. Munson E, Embro W. Enfurane, isoflurane and halothane and isolated human uterine muscle. Anesthesiology 1977; 46: 11-14. 10. Biehl DR, Gregory GA, Tweed A, Cote J, Wade JG, Sitar D. Effect of halothane on cardiac output and regional flow in the fetal lamb in utero. Anesth Analg 1983; 62:489-492. 11. Danforth DN. The distribution and functional activity of the cervical musculature. Am J Obset Gynecol 1954; 68:1261-1271. 12. Alfred Lee J, Atkinson RS, Rushman GB. A Synopsis of Anaesthesia, 10th ed. Wright Publishing Ltd. Bristol 1987; 105. 13. Palahniuk RJ, Schnider SM, Eger El. Pregnancy decreases the requirement for inhaled anesthetic agents, Anesthesiology 1974; 41 :82-83. 14. Gutsche BB, Samuels P. Anaesthetic considerations in premature birth. Int Anesthesiol Clin 1990; 28:33-43. 15. Portenoy RK. Mechanism of Clinical Pain: Observations and speculations. Neurol Clin 1989; 7:205-230. 16. Welchew EA. On-demand analgesis. A double blind comparison of on-demand intravenous fentanyl with regular intramuscular morphine. Anaesthesia 1983; 38: 19-25.
Nocturnal Nasal Mask CPAP and Ventilation: Two Case Reports JAMES TIBBALLS* AND LYNDALL YEOMANt
Intensive Care Unit, Royal Children's Hospital and Fairfield Infectious Diseases Hospital. Melbourne, Victoria Key Words: SLEEP: apnoea, obstructive, central alveolar hypoventilation syndrome, Ondine's curse, nocturnal nasal mask CP AP
Noninvasive continuous positive airway pressure (CPAP) and mechanical ventilation have been used in adults for conditions such as obstructive sleep apnoea, central alveolar hypoventilation syndrome (Ondine's curse) and chronic nocturnal hypo ventilation due to neuromuscular diseases since the early 1980s. The development of appropriate masks, ventilators and circuits has enabled the domiciliary use of CP AP *B.Med.Sci.(Hons.), F.F.A.R.A.C.S. tDip.Occ. Therapy. Address for Reprints: Dr. J. Tibballs, Intensive Care Unit, Royal Children's Hospital, Aemington Road, Parkville, Victoria 3052, Australia. Accepted for publication November 26, 1990
Anaesthesia and Intensive Care, Vol. 19, No. 2, May, 1991
and ventilation and obviated the need for longterm endotracheal intubation and tracheostomy. We present a case of a child with obstructive sleep apnoea relieved with nasal CPAP and a case of an adolescent with central alveolar hypoventilation treated with nocturnal nasal ventilation - in both cases delivered by custom-made masks. Case J A seventeen-month-old girl weighing 11 kg with achondroplasia and hydrocephalus presented with inspiratory stridor and cyanosis. The haemoglobin oxygen saturation measured using pulse oximetry was 50-60% during sleep. Arterial blood gas analysis, with oxygen therapy, yielded a P a02 of 50
J. R. BRIMACOMBE
intubation is more appropriate if there is a risk of regurgitation. Payne has clearly shown that despite an unobstructed airway the oesophagus can occasionally be seen through the LMA using a fibreoptic laryngoscope. 3 Swallowing air during balanced regional anaesthesia with a LMA has not previously been reported and was only noted in this patient because the length of the procedure permitted gastric dilatation to occur. A light general anaesthetic, which has not obtunded the swallowing reflex, combined with a misplaced LMA, in which the oesophagus and laryngeal inlet are communicating, can allow this. This case demonstrates a rare but potentially
serious problem which can arise during light anaesthesia with a LMA. It also re-emphasises that the LMA does not reliably separate the respiratory from the gastrointestinal tracts and that constant vigilance is required during its use. REFERENCES I. Brain AI1. Laryngeal mask and trauma to uvula (a
reply to a letter). Anaesthesia 1989; 44: 1014-5. 2. Murdoch L, Rubin A. Use of the Brain laryngeal mask in balanced regional anaesthesia. Anaesthesia 1989; 44:616. 3. Payne J. The use of the fibreoptic laryngoscope to confirm the position of the laryngeal mask. Anaesthesia 1989; 44:865.
Intra- and Postoperative Anaesthetic Management of an Opioid Addict Undergoing Caesarean Section R. K. BOYLE*
Department of Anaesthesia, The Royal Women's Hospital, Brisbane, Queensland Key Words: ANALGESIA, OBSTETRIC: PCA, persistent uterine constriction, opioid addict
Drug addiction in the parturient harms mother and baby. Recognition and management of opioid abuse early in pregnancy may prevent some problems but other complications may arise unexpectedly. This report documents the avoidance of some potential difficulties and the mismanagement of an unpredicted problem during caesarean section in an opioid addict. CASE REPORT A 23-year-old, 58-kg woman, gravida 5, para 2, terminations 2, presented in labour at thirty weeks' gestation. She was transferred ninety-five kilometres by air ambulance helicopter with a twelve-hour history of moderate uterine contractions. The patient had used intravenous heroin until the seventeenth week of her pregnancy, when she changed to oral methadone 25 mg per day. Drug treatment of her premature labour included intramuscular dexamethasone 20 mg, then two daily doses of betamethasone 12 mg and intravenous salbutamol 3.3 f..lg.min - I increasing to *F.F.A.R.A.C.S., Staff Anaesthetist. Address for Reprints: Dr. R. Boyle, Department of Anaesthesia, Royal Women's Hospital, P.O. Royal Brisbane Hospital, Queensland 4029, Australia. Accepted for publication November 26, 1990
6.7 f..lg.min - I until maternal headache, tachycardia and foetal tachycardia occurred. Intravenous fluids were glucose-free and restricted to less than two litres per day. Sixteen hours after uterine contractions ceased, salbutamol was changed to oral administration, 3 mg having been administered over fifteen hours. Oral salbutamol was continued for ten days, 24 mg per day in divided doses. Bed rest proved difficult for this patient, who persuaded her husband and other patients to push her wheelchair outside the hospital so that she could continue to smoke. Laboratory assessment No abnormality was detected in serial serum electrolytes, platelets, white cells, liver function, creatinine, blood urea, and glucose. Cultures from high vaginal swabs grew normal vaginal flora with no haemolytic streptococcus B. A normochromic normocytic anaemia, haemoglobin 8.2 g/dl was noted. Twenty-four hours after cessation of parenteral salbutamol, two units of packed red cells were slowly infused. Antibodies were detected to Rubella and Hepatitis C viral antigen, but not to Hepatitis B, or Human Immunodeficiency viruses. A urinary drug screen was not performed. Anaesthesia and Intensive Care. Vol. 19, No. 2, May, 1991
277
CASE REPORT
The delivery and neonatal status At thirty-two weeks' gestation, labour recommenced. Examination revealed a footling breech presentation, a 7 cm dilated cervix and bulging forewaters. It was decided to deliver the infant by caesarean section under a general anaesthetic which consisted of thiopentone 8 mg.kg -!, suxamethonium, atracurium, 50% nitrous oxide in oxygen, and enflurane 2.5% until the umbilical cord was clamped. The technique included preoperative sodium citrate, left uterine displacement, preoxygenation, rapid sequence induction, cricoid pressure, tracheal intubation and intermittent positive pressure ventilation to maintain end-tidal CO 2 at 32 mmHg. A Pfannenstiel incision, then transverse lower uterine incision were performed. After membranes were ruptured, one infant leg was found flexed at the hip and knee, the other extended and surrounded by a constriction ring of uterine muscle. This persisted despite an inspired concentration of enflurane 2.5%. The uterine incision was extended vertically in a l-fashion before the trunk and head of the infant could be extracted. Uterine-incision to delivery time was eight minutes. Blood loss was estimated at 600 to 800 ml. The infant was flaccid, apnoeic, and had a heart rate of 70 per minute. The Apgar score was 3 at 1 minute. The infant's trachea was intubated and 100% oxygen given by intermittent positive pressure ventilation. The heart rate increased to 160 per minute and limbs became active. The Apgar score increased to 8 at 5 minutes, and within twenty minutes of delivery, the infant was extubated. Extensive bruising of the left leg was present. Birth weight was 1990 g, which was between the fiftieth and seventieth centiles for 32 weeks gestation. The baby required an intravenous 10% dextrose bolus in the first two hours, and became jaundiced with serum bilirubin 13 J,lmol.l-! on the fourth day. Nasogastric feeds and bottle feeds were established by day 2. No intracranial haemorrhages were demonstrated by ultrasound. The cerebral ventricles were normal in TABLE 1 PCA use during loading phase 2 Hours after operation Morphine requirement (mg/hr) 15 Demands per hr 7 Successful demands per hr 6 Respiratory rate (per min) 18 Cumulative dose morphine (mg) 30 Anaesthesia and Intensive Care. Vol. 19. No. 2. May. 1991
4
6
16 3
10
3
1
18 80
20 110
size and configuration. No signs of ne onataI opioid withdrawal occurred and the infant was discharged on day 11, weighing 1860 g. Postoperative analgesia Postoperative analgesia was provided by patientadministered intravenous boluses of morphine with a background infusion of 3 mg/hour. The method of use of patient-controlled analgesia, PCA, in this opioid addict is shown in Tables 1 and 2. No oral methadone was administered until bowel sounds became audible postoperatively. 1 Loading phase Initially the bolus dose was doubled because of persistence of severe pain, with the number of unsuccessful demands exceeding successful demands (Table 1).
2. Maintenance phase The background infusion was then decreased to 1.5 mg/hr, to allow ambulation while preventing symptoms of opioid withdrawal. Once a consistent reduction in hourly demand rate occurred, the morphine infusion was discontinued. (Table 2) Oral methadone was recommenced thirty-six hours postoperatively. DISCUSSION
This patient's outcome was improved by regular counselling, frequent antenatal obstetric review, and the substitution of oral methadone for selfadministered intravenous heroin. 1. Drug dependence The pregnant opioid addict is often malnourished, with suppressed pituitary adrenocorticotrophic hormone, and adrenocortical function. Common infective sequelae of intravenous drug abuse include cellulitis, superficial abscesses, septic phlebitis, tetanus. bacterial pneumonia, foreign body emboli, bacterial endocarditis. Pulmonary hypertension or acute pulmonary oedema may occur in the addicted parturient.! Opioid addiction produces up to a threefold TABLE 2 PCA use during maintenance phase Hours after operation Morphine requirement (mg/hr) Demands per hr Successful demands per hr Respiratory rate (per min) Cumu~ative dose morphine (mg)
8
12
16
20
9 6 5 6 2 2 3 2 1 2 3 18 18 16 16
158 178 202 238
278
R. K.
BOYLE
foetal manipulation. Unfortunately the general anaesthetic failed to achieve the required uterine relaxation and probably contributed to early neonatal depression. Volatile anaesthetics depress uterine contractility in proportion to the depth of anaesthesia. 9 Resting uterine tone is little altered at 0.5 MAC and haemorrhage from the placental site is unlikely. At 1 to 1.5 MAC, uterine tone, contractility and uterine vascular resistance are reduced and uterine perfusion increases. These concentrations are normally recommended for intra-uterine manipulation. At 2 MAC and larger doses there lU"ede.creases in maternal uterine perfusion and in foetal cardiac output, heart rate, base excess and oxygen saturation. 10 Excessive bleeding may occur after placental separation. It is uncertain why localised uterine constriction persisted. The 'constriction ring' may have been undilated cervix. Smooth muscle constitutes only 10% to 15% of total cervical tissue in most women, II the remainder are collagen and glycosaminoglycans. Therefore, whil~ the potent inhalational agents can achieve profound uterine relaxation, they may provide only limited cervical relaxation. In summary, general anaesthesia did not guarantee ideal conditions for abdominal delivery of a breech infant, but the excessive doses of general anaesthetics contributed to neontal depression (3 MAC enflurane,12,13 thiopentone 8 mg.kg- I , and foetal equilibration with nitrous oxide l4 subsequent to the long induction-to-delivery interval). 3. Postoperative analgesia for a methadone user Analgesia duration and dose cannot be preformulated according to the type of surgery undergone. 15 With this patient's history of opioid abuse, prior selection of an effective post-caesarean 2. The choice of general rather than regional analgesia regime was both inadvisable and anaesthesia Breech presentation occurs more frequently with impossible. Not only was a minimum analgesia increasing prematurity which carries its own high plasma concentration or other therapeutic endneonatal mortality rate. For vaginal delivery of point unpredictable, but also an effect other than breech, regional conduction techniques are the extinction of pain might have been demanded. preferable to general anaesthesia. 5 Properly The hourly nursing assessment of vital signs, conducted epidural analgesia avoids maternal and mental state, pain and analgesia use would readily foetal depression from parenteral opioids, which is have detected self-overdose with PCA. In addition analgesia supply and demand were important to the premature infant with respiratory sensitivity, underdeveloped blood brain barrier quantified by the PCA memory. For instance, an objective indication that the initial demand dose and impaired hepatic and renal clearance. In this patient a rapid induction of general was too small was the disparity between requested anaesthesia was chosen in view of the footling and satisfied demands. As in other studies, mean breech presentation, bulging forewaters and active hourly demand rates showed more detail than total labour, imminent membrane rupture and possible cumulative dose of opioid. 16 In summary, this case report describes the cord prolapse. In addition, the inhalational agent was expected to offer the potential for intrauterine persistence of a uterine constriction ring under
increase in perinatal mortality. Meconium aspiration, a high incidence of premature rupture of the membranes and premature labour, are associated with 50% of the foetal deaths. During pregnancy, foetal hypoxia and hypercarbia, during maternal opioid overdose, correlate with an increased incidence of congenital anomalies. A heroin addict may have repeated withdrawal throughout the pregnancy depending on availability and quality of her supply. During withdrawal, uterine contractions can occur and interfere with placental perfusion or progress to premature labour of short duration. Maternal withdrawal also carries the risk of foetal withdrawal, leading to foetal hyperactivity, increased oxygen consumption and possibly to _foetal_hJpoxia. Though this patient was still undernourished and anaemic, better obstetric care and neonatal monitoring were achieved after the change from parenteral heroin to oral methadone. The daily dose of methadone is important, correlating with the severity of neonatal withdrawal after delivery. Madden recommends 20 mg or less per day but cautions against too rapid detoxification and foetal distress. 2 Factors statistically associated with premature labour and present in this patient were anaemia and a urinary infection prior to admission. The pregnancy was prolonged to 32 weeks' gestation following treatment of anaemia, maternal infection and tocolysis, and avoidance of sideeffects deleterious to mother and infant.3 Dexamethasone probably accelerated in utero biochemical maturation of this baby's lungs. 4 The choice of dexamethasone or betamethasone over cortisol or prednisolone is based on greater in vitro placental extraction of the latter,5 but this, and the usefulness of steroids, are still controversia1. 6,7
Anaesthesia and Intensive Care. Vol. 19, No. 2, May, 1991
CASE REPORT
general anaesthesia and the successful use of postoperative PCA in a drug addict. REFERENCES
I. Rolbin SH, Rolbin SB. Drug addiction: anaesthetic considerations for the mother foetus and newborn. In: Obstetric anaesthesia: the complicated patient. James F, Wheeler AS, eds. FA Davis Co, Philadelphia 1982; 319-322. 2. Madden JD. Problems pertaining to the care of the newborn infants of drug-addicted women. J Reprod Med 1978; 20:303-306. 3. Spiel man FJ, Herbert W. Maternal cardiovascular effects of drugs that alter uterine activity. Obstet Gynecol Surv 1988; 43: 516-522. 4. Doyle LW, Kitchen WH et al. Effects of antenatal steroid therapy on mortality and morbidity in very low birthweight infants. J Pediat 1986, 108:287-292. 5. Blanford B, Pearson B, Murphy M. In vitro metabolism of prednisonlone, dexamethasome, betametasone and cortisol by the human placenta. Am J Obstet Gynecol 1977; 127:264-267. 6. Levitz M, Jansen V, Davis J. The transfer and metabolism of corticosteroids in the perfused human placenta. Am J Obstet Gynecol 1978; 132:363-366. 7. Avery ME, Aylward G, Creasy R, Little B, Stripp B. Update on prenatal steroids for prevention of respiratory distress. Report of a conference - Sept 26-28, 1985. Am J Ob stet Gynecol 1986; 155:2-5.
279
8. Breeson A, Kovacs G, Pickles B, Hill J. Extradural analgesia: the preferred method of analgesia for vaginal breech delivery. Br J Anaesth 1978;50: 1227-1229. 9. Munson E, Embro W. Enfurane, isoflurane and halothane and isolated human uterine muscle. Anesthesiology 1977; 46: 11-14. 10. Biehl DR, Gregory GA, Tweed A, Cote J, Wade JG, Sitar D. Effect of halothane on cardiac output and regional flow in the fetal lamb in utero. Anesth Analg 1983; 62:489-492. 11. Danforth DN. The distribution and functional activity of the cervical musculature. Am J Obset Gynecol 1954; 68:1261-1271. 12. Alfred Lee J, Atkinson RS, Rushman GB. A Synopsis of Anaesthesia, 10th ed. Wright Publishing Ltd. Bristol 1987; 105. 13. Palahniuk RJ, Schnider SM, Eger El. Pregnancy decreases the requirement for inhaled anesthetic agents, Anesthesiology 1974; 41 :82-83. 14. Gutsche BB, Samuels P. Anaesthetic considerations in premature birth. Int Anesthesiol Clin 1990; 28:33-43. 15. Portenoy RK. Mechanism of Clinical Pain: Observations and speculations. Neurol Clin 1989; 7:205-230. 16. Welchew EA. On-demand analgesis. A double blind comparison of on-demand intravenous fentanyl with regular intramuscular morphine. Anaesthesia 1983; 38: 19-25.
Nocturnal Nasal Mask CPAP and Ventilation: Two Case Reports JAMES TIBBALLS* AND LYNDALL YEOMANt
Intensive Care Unit, Royal Children's Hospital and Fairfield Infectious Diseases Hospital. Melbourne, Victoria Key Words: SLEEP: apnoea, obstructive, central alveolar hypoventilation syndrome, Ondine's curse, nocturnal nasal mask CP AP
Noninvasive continuous positive airway pressure (CPAP) and mechanical ventilation have been used in adults for conditions such as obstructive sleep apnoea, central alveolar hypoventilation syndrome (Ondine's curse) and chronic nocturnal hypo ventilation due to neuromuscular diseases since the early 1980s. The development of appropriate masks, ventilators and circuits has enabled the domiciliary use of CP AP *B.Med.Sci.(Hons.), F.F.A.R.A.C.S. tDip.Occ. Therapy. Address for Reprints: Dr. J. Tibballs, Intensive Care Unit, Royal Children's Hospital, Aemington Road, Parkville, Victoria 3052, Australia. Accepted for publication November 26, 1990
Anaesthesia and Intensive Care, Vol. 19, No. 2, May, 1991
and ventilation and obviated the need for longterm endotracheal intubation and tracheostomy. We present a case of a child with obstructive sleep apnoea relieved with nasal CPAP and a case of an adolescent with central alveolar hypoventilation treated with nocturnal nasal ventilation - in both cases delivered by custom-made masks. Case J A seventeen-month-old girl weighing 11 kg with achondroplasia and hydrocephalus presented with inspiratory stridor and cyanosis. The haemoglobin oxygen saturation measured using pulse oximetry was 50-60% during sleep. Arterial blood gas analysis, with oxygen therapy, yielded a P a02 of 50
