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Effect of position during initial bolus injection
Correspondence The LMA Introducer as an aid to the passage of orogastric tubes The passage of an orogastric tube during abdominal surgery or caesarean section can often be an awkward procedure. In our experience it is not uncommon for it to coil up in the back of the oropharynx. We have found that the insertion of an LMA introducer (SIMS, Portex Ltd., UK) as a guide, aids the passage of an orogastric tube straight down the oesophagus. We have used it successfully for sizes up to the 40 gauge stomach lavage tube. A. Hallett, R. Marjot Department of Anaesthesia, Royal United Hospital, Bath, UK
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adrenaline, other workers3 have demonstrated that it is neither sensitive nor specific in the obstetric population in labour and may be harmful to the compromised fetus. Because of these limitations, many obstetric anaesthetists regard the test dose as only a means of excluding accidental intrathecal placement. A commonly used dose for subarachnoid block for elective caesarean section is 2.5 mL of hyperbaric bupivacaine (0.5%) with or without opioid. This dose (12.5 mg heavy bupivacaine) reliably produces a block to T4-6. Most obstetric anaesthetists are aware that the ensuing sympathetic block may be profound and use a combination of fluid and vasopressors (generally ephedrine) to minimize the potential drop in blood pressure. The literature abounds with examples of high and total spinals after accidental subarachnoid injection of 3 mL of 0.5% bupivacaine (15 mg plain bupivacaine) used as a test dose with the catheter inadvertently placed intrathecally.‘+6 Chan et al.’ used 20 mg plain bupivacaine as the epidural test dose. This dose confounds the principle of the test dose, which was conceived to identify a misplaced catheter without causing harm. The administration of a safe initial epidural dose is even more important when it is given in the labour room setting rather than theatre. This is because immediate access to dedicated, skilled anaesthetic assistance and facilities for safe endotracheal intubation might not be quite so immediately to hand. When will anaesthetists learn to use safe test doses in parturients? J. Tuckey Consultant Obstetric Anaesthetist, Royal United Hospital, Bath, UK
Effect of position during initial bolus injection I read with interest the paper by Chan et al.’ regarding the effect of position during initial bolus injection (horizontal or 10” head-up tilt) on perceived pain during elective caesarean section under epidural blockade. I was, however, concerned at Chan et al.‘s description of the initial management of the epidural block.’ The aspiration test to exclude accidental intrathecal or intravenous injection does not appear to have been performed after initial placement of the epidural catheter. Most would regard this a vital first safety manoeuvre. It is only mentioned prior to supplementary bolus injection. They then used 4 mL 0.5% plain bupivacaine as their initial test dose. Most would agree that the first epidural injection should cause no harm to the patient wherever the tip of the epidural catheter might be positioned. Following the work of Moore and Battra,2 it has long been considered necessary for the test dose to contain 15 pg of adrenaline in order to detect accidental intravenous placement of the epidural catheter. Using 15 pg of
REFERENCES
1. Chan YK, Ali A, Oh L. Pain during elective caesarean section under epidural anaesthesia: the effect of a 10” head-up tilt position. International Journal of Obstetric Anesthesia 1999; 8: 101-104. 2. Moore DC, Battra MS. The components of an effective test dose prior to epidural block. Anesthesiology 1981; 55: 693496. 3. Cartwright PD, McCarroll SM, Antzaka C. Maternal heart rate changes with a plain epidural test dose. Anesthesiology 1986; 65: 226-228. 4. Palkar NV, Boudreaux RC, Mankad AV. Accidental total spinal block: a complication of an epidural test dose. Can J Anaesth 1992; 39: 1058-1060. 5. Fine PG, Wong KC. Cranial nerve block after test dose through an epidural catheter in a pre-eclamptic parturient. Can Anaesth Sot J 1984; 31: 565-567. 6. Russell IF. Inadvertent total spinal for Caesarean section. Anaesthesia 1985; 40: 199-200.
In reply We appreciate Dr Jennifer Tuckey’s concern about the way we managed our epidural blockade. We agree completely that aspiration of the catheter before any
Fig. 1
293
adrenaline, other workers3 have demonstrated that it is neither sensitive nor specific in the obstetric population in labour and may be harmful to the compromised fetus. Because of these limitations, many obstetric anaesthetists regard the test dose as only a means of excluding accidental intrathecal placement. A commonly used dose for subarachnoid block for elective caesarean section is 2.5 mL of hyperbaric bupivacaine (0.5%) with or without opioid. This dose (12.5 mg heavy bupivacaine) reliably produces a block to T4-6. Most obstetric anaesthetists are aware that the ensuing sympathetic block may be profound and use a combination of fluid and vasopressors (generally ephedrine) to minimize the potential drop in blood pressure. The literature abounds with examples of high and total spinals after accidental subarachnoid injection of 3 mL of 0.5% bupivacaine (15 mg plain bupivacaine) used as a test dose with the catheter inadvertently placed intrathecally.‘+6 Chan et al.’ used 20 mg plain bupivacaine as the epidural test dose. This dose confounds the principle of the test dose, which was conceived to identify a misplaced catheter without causing harm. The administration of a safe initial epidural dose is even more important when it is given in the labour room setting rather than theatre. This is because immediate access to dedicated, skilled anaesthetic assistance and facilities for safe endotracheal intubation might not be quite so immediately to hand. When will anaesthetists learn to use safe test doses in parturients? J. Tuckey Consultant Obstetric Anaesthetist, Royal United Hospital, Bath, UK
Effect of position during initial bolus injection I read with interest the paper by Chan et al.’ regarding the effect of position during initial bolus injection (horizontal or 10” head-up tilt) on perceived pain during elective caesarean section under epidural blockade. I was, however, concerned at Chan et al.‘s description of the initial management of the epidural block.’ The aspiration test to exclude accidental intrathecal or intravenous injection does not appear to have been performed after initial placement of the epidural catheter. Most would regard this a vital first safety manoeuvre. It is only mentioned prior to supplementary bolus injection. They then used 4 mL 0.5% plain bupivacaine as their initial test dose. Most would agree that the first epidural injection should cause no harm to the patient wherever the tip of the epidural catheter might be positioned. Following the work of Moore and Battra,2 it has long been considered necessary for the test dose to contain 15 pg of adrenaline in order to detect accidental intravenous placement of the epidural catheter. Using 15 pg of
REFERENCES
1. Chan YK, Ali A, Oh L. Pain during elective caesarean section under epidural anaesthesia: the effect of a 10” head-up tilt position. International Journal of Obstetric Anesthesia 1999; 8: 101-104. 2. Moore DC, Battra MS. The components of an effective test dose prior to epidural block. Anesthesiology 1981; 55: 693496. 3. Cartwright PD, McCarroll SM, Antzaka C. Maternal heart rate changes with a plain epidural test dose. Anesthesiology 1986; 65: 226-228. 4. Palkar NV, Boudreaux RC, Mankad AV. Accidental total spinal block: a complication of an epidural test dose. Can J Anaesth 1992; 39: 1058-1060. 5. Fine PG, Wong KC. Cranial nerve block after test dose through an epidural catheter in a pre-eclamptic parturient. Can Anaesth Sot J 1984; 31: 565-567. 6. Russell IF. Inadvertent total spinal for Caesarean section. Anaesthesia 1985; 40: 199-200.
In reply We appreciate Dr Jennifer Tuckey’s concern about the way we managed our epidural blockade. We agree completely that aspiration of the catheter before any