230
BRITISH JOURNAL OF ANAESTHESIA TABLE I. Recent anaesthetic history of the patient
REFERENCE 1. Sharrock NE, Mineo R, Urquhart B. Haemodynamic effects and outcome analysis of hypotensive extradural anaesthesia in controlled hypertensive patients undergoing total hip arthroplasty. British Journal of Anaesthesia 1991; 67: 17-25.
Sir,-—Dr Delia Pupa questions the mechanism whereby reversal of hypotension can be achieved at the end of surgery when extensive neural block is still in effect. Our usual approach is to discontinue low-dose adrenaline slowly and change to ephedrine with or without a fluid challenge. This enables systolic pressure to be maintained typically in the range 100-120 mm Hg in the post-anaesthesia care unit. Ephedrine has both alpha and beta effects, so that arterial pressure can be maintained without causing tachycardia. Ephedrine and fluid as a means of maintaining circulatory stability for patients with high extradural block has been an accepted practice for some time, in both surgical [1] and obstetric patients. _ „ N. E. SHARROCK
New York
Anaesthetic
Date Oct 74
Gaseous induction halothane, spontaneous breathing July 86 Gaseous induction halothane, spontaneous breathing July 90 Ketamine induction, suxamethonium—vecuronium, ventilation with enfiurane Feb 91 Etomidate induction, suxamethonium-vecuronium, ventilation with isoflurane
TABLE II. Porphyrin screen results
Delta aminolaevulinic acid (mmol litre"'/24 h) Porphobilinogen (mmol litre-724 h)
Control
1h
8 h Normal range
59
28
42
0-40
64
63
62
0-16
REFERENCE 1. Engberg G, Wiklund L. The use of ephedrine for prevention of arterial hypotension during epidural blockade: A study of the central circulation after subcutaneous premedication. Acta Anaesthesiologica Scandinavica 1978; 66; 1—26.
PROPOFOL IN ACUTE INTERMITTENT PORPHYRIA Sir,—Acute intermittent porphyria (AIP) is the most common of the acute hepatic porphyrias occurring in the U.K. The condition arises from decreased activity of the enzyme, porphobilinogen deaminase, leading to the characteristic increase in the concentration of precursors before the block in the metabolic pathway. In common with other acute porphyrias, it is possible to precipitate an acute attack by administration of some drugs, and of particular concern to the anaesthetist is the choice of an appropriate i.v. induction agent. Thiopentone, methohexitone [1], Althesin [2], etomidate [3] and ketamine [4] have been reported to be porphyrinogenic. Most reports of the use of propofol involved patients with variegate porphyria (VP). We could find only one case report of the use of propofol and AIP [5]. Therefore, we would like to report the case of a patient with AIP in whom propofol was used. A 26-yr-old female with a documented history of AIP since 1982 was admitted for a minor gynaecological procedure. The patient had received no porphyrinogenic drugs in the previous 6 months. Since 1974 she had received four general anaesthetics before this admission (table I). On this occasion the patient received no premedication. On arrival in the anaesthetic room, she was given fentanyl 75 ug i.v. then propofol 2 mg kg"1. Anaesthesia was maintained with 1-2 % enflurane and 66 % nitrous-oxide in oxygen administered via a facemask and a Bain coaxial circuit. After an uneventful recovery, the patient returned to the ward and was discharged 8 h later. Urine samples were obtained before operation and 1 and 8 h after operation and a porphyrin screen carried out. The results (table II) showed no marked increase in porphobilinogen concentration in postoperative samples compared with the preoperative control, although a slight increase in aminolaevulinic acid concentration was detected. The patient reported no symptoms recognizable by her as attributable to her porphyria in the early postoperative period or subsequently. The use of propofol in the context of acute porphyrias has been studied [6], and conflicting reports exist as to its safety. The majority of the work involved patients with VP and not AIP [7].
Mitterschiffthaler and colleagues [5] reported the case of a 43-yrold female who underwent general anaesthesia using propofol as the induction agent, without subsequent biochemical or clinical adverse effects. These authors, while reporting the apparent safety of propofol in AIP, were guarded in their recommendation until further successful administrations had been documented. The assessment of the porphyrinogenicity of a drug depends usually on the ability to detect increased concentrations of porphyrin precursors following its administration. It is obvious, however, that the relationship between increased concentrations of porphyrin precursors and manifest clinical symptoms is not a simple one [8]. Despite this, and in accordance with current criteria, we feel this case provides additional evidence to support the use of propofol as an induction agent in AIP, and more generally its use in the context of acute porphyrias. M. A. TIDMARSH D. F. BAIGENT
Leicester
REFERENCES 1. Disler PB, Blekkenhorst GH, Eales L, Moore MR, Stragham J. Guidelines for drug prescription in patients with acute porphyrias. South African Medical Journal 1982; 61: 656-660. 2. Parikh RK, Moore MR. Anaesthetics in porphyria; intravenous induction agents. British Journal of Anaesthesia 1975; 47: 907-917. 3. Harrison GG, Moore MR, Miessner PN. Porphyrinogenicity of etomidate and ketamine continuous infusions. British Journal of Anaesthesia 1985; 57: 420-423. 4. Kostrzievska E, Cregor A. Ketamine in acute intermittent porphyria—dangerous or safe? Aneslhesiology 1978; 49: 376-377. 5. Mitterschiffthaler G, Thiener A, Herzel H, Frith LC. Safe use of propofol in a patient with acute intermittent porphyria. British Journal of Anaesthesia 1988; 60: 109-111. 6. Weir PM, Hodgkinson A. Is propofol a safe agent in porphyria? Anaesthesia 1988; 43: 1022-1023. 7. Meisner PN, Harrison G, Hift RJ. Propofol as an i.v. induction agent in variegate porphyria. British Journal of Anaesthesia 1991; 66: 60-65. 8. Mustajoki P, Heimonen J. General anesthesia in inducible porphyrias. Anesthesiology 1980; 53: 15-20.
BRITISH JOURNAL OF ANAESTHESIA TABLE I. Recent anaesthetic history of the patient
REFERENCE 1. Sharrock NE, Mineo R, Urquhart B. Haemodynamic effects and outcome analysis of hypotensive extradural anaesthesia in controlled hypertensive patients undergoing total hip arthroplasty. British Journal of Anaesthesia 1991; 67: 17-25.
Sir,-—Dr Delia Pupa questions the mechanism whereby reversal of hypotension can be achieved at the end of surgery when extensive neural block is still in effect. Our usual approach is to discontinue low-dose adrenaline slowly and change to ephedrine with or without a fluid challenge. This enables systolic pressure to be maintained typically in the range 100-120 mm Hg in the post-anaesthesia care unit. Ephedrine has both alpha and beta effects, so that arterial pressure can be maintained without causing tachycardia. Ephedrine and fluid as a means of maintaining circulatory stability for patients with high extradural block has been an accepted practice for some time, in both surgical [1] and obstetric patients. _ „ N. E. SHARROCK
New York
Anaesthetic
Date Oct 74
Gaseous induction halothane, spontaneous breathing July 86 Gaseous induction halothane, spontaneous breathing July 90 Ketamine induction, suxamethonium—vecuronium, ventilation with enfiurane Feb 91 Etomidate induction, suxamethonium-vecuronium, ventilation with isoflurane
TABLE II. Porphyrin screen results
Delta aminolaevulinic acid (mmol litre"'/24 h) Porphobilinogen (mmol litre-724 h)
Control
1h
8 h Normal range
59
28
42
0-40
64
63
62
0-16
REFERENCE 1. Engberg G, Wiklund L. The use of ephedrine for prevention of arterial hypotension during epidural blockade: A study of the central circulation after subcutaneous premedication. Acta Anaesthesiologica Scandinavica 1978; 66; 1—26.
PROPOFOL IN ACUTE INTERMITTENT PORPHYRIA Sir,—Acute intermittent porphyria (AIP) is the most common of the acute hepatic porphyrias occurring in the U.K. The condition arises from decreased activity of the enzyme, porphobilinogen deaminase, leading to the characteristic increase in the concentration of precursors before the block in the metabolic pathway. In common with other acute porphyrias, it is possible to precipitate an acute attack by administration of some drugs, and of particular concern to the anaesthetist is the choice of an appropriate i.v. induction agent. Thiopentone, methohexitone [1], Althesin [2], etomidate [3] and ketamine [4] have been reported to be porphyrinogenic. Most reports of the use of propofol involved patients with variegate porphyria (VP). We could find only one case report of the use of propofol and AIP [5]. Therefore, we would like to report the case of a patient with AIP in whom propofol was used. A 26-yr-old female with a documented history of AIP since 1982 was admitted for a minor gynaecological procedure. The patient had received no porphyrinogenic drugs in the previous 6 months. Since 1974 she had received four general anaesthetics before this admission (table I). On this occasion the patient received no premedication. On arrival in the anaesthetic room, she was given fentanyl 75 ug i.v. then propofol 2 mg kg"1. Anaesthesia was maintained with 1-2 % enflurane and 66 % nitrous-oxide in oxygen administered via a facemask and a Bain coaxial circuit. After an uneventful recovery, the patient returned to the ward and was discharged 8 h later. Urine samples were obtained before operation and 1 and 8 h after operation and a porphyrin screen carried out. The results (table II) showed no marked increase in porphobilinogen concentration in postoperative samples compared with the preoperative control, although a slight increase in aminolaevulinic acid concentration was detected. The patient reported no symptoms recognizable by her as attributable to her porphyria in the early postoperative period or subsequently. The use of propofol in the context of acute porphyrias has been studied [6], and conflicting reports exist as to its safety. The majority of the work involved patients with VP and not AIP [7].
Mitterschiffthaler and colleagues [5] reported the case of a 43-yrold female who underwent general anaesthesia using propofol as the induction agent, without subsequent biochemical or clinical adverse effects. These authors, while reporting the apparent safety of propofol in AIP, were guarded in their recommendation until further successful administrations had been documented. The assessment of the porphyrinogenicity of a drug depends usually on the ability to detect increased concentrations of porphyrin precursors following its administration. It is obvious, however, that the relationship between increased concentrations of porphyrin precursors and manifest clinical symptoms is not a simple one [8]. Despite this, and in accordance with current criteria, we feel this case provides additional evidence to support the use of propofol as an induction agent in AIP, and more generally its use in the context of acute porphyrias. M. A. TIDMARSH D. F. BAIGENT
Leicester
REFERENCES 1. Disler PB, Blekkenhorst GH, Eales L, Moore MR, Stragham J. Guidelines for drug prescription in patients with acute porphyrias. South African Medical Journal 1982; 61: 656-660. 2. Parikh RK, Moore MR. Anaesthetics in porphyria; intravenous induction agents. British Journal of Anaesthesia 1975; 47: 907-917. 3. Harrison GG, Moore MR, Miessner PN. Porphyrinogenicity of etomidate and ketamine continuous infusions. British Journal of Anaesthesia 1985; 57: 420-423. 4. Kostrzievska E, Cregor A. Ketamine in acute intermittent porphyria—dangerous or safe? Aneslhesiology 1978; 49: 376-377. 5. Mitterschiffthaler G, Thiener A, Herzel H, Frith LC. Safe use of propofol in a patient with acute intermittent porphyria. British Journal of Anaesthesia 1988; 60: 109-111. 6. Weir PM, Hodgkinson A. Is propofol a safe agent in porphyria? Anaesthesia 1988; 43: 1022-1023. 7. Meisner PN, Harrison G, Hift RJ. Propofol as an i.v. induction agent in variegate porphyria. British Journal of Anaesthesia 1991; 66: 60-65. 8. Mustajoki P, Heimonen J. General anesthesia in inducible porphyrias. Anesthesiology 1980; 53: 15-20.
![[Continuous propofol infusion in a patient with acute intermittent porphyria].](/assets/img/hold.png)
