Transversus Abdominis Plane (TAP) Blocks

A. Pain at rest was non-inferior to epidural, opioid consumption failed non-inferiority (ratio of geometric means 1.37, an absolute difference of about 21 mg morphine equivalents over 3 days), and mean arterial pressure below 65 mmHg occurred in 48% of epidural patients versus 31% of TAP patients

The trial stopped early for futility at the third interim analysis. It is the honest version of the enhanced-recovery recommendation: the blocks match the epidural for pain at rest, cost about 21 mg morphine equivalents over three days, and buy a meaningful reduction in hypotension. The authors' own conclusion is that clinicians should reconsider epidural analgesia in patients at risk from hypotension.

Pain control was comparable at rest and on movement. The block came out ahead on 24-hour and total opioid consumption, time to ambulation, urinary catheter duration, and the incidence of sensory disturbance and postoperative hypotension. When laparoscopic surgery was the only approach, the block additionally shortened time to first flatus and lowered the incidence of postoperative nausea and vomiting. The two were equivalent on 48-hour opioid consumption, on postoperative nausea and vomiting overall, and on hospital stay.

The advantages here are almost all downstream of what the epidural does to sympathetic tone and to the bladder — earlier walking, earlier catheter removal, less hypotension. In a minimally invasive operation those are the outcomes that decide the pathway, not the pain score.

The mean peak total ropivacaine concentration was 1.82 micrograms/ml (SD 0.69) and occurred 30 minutes after injection; the highest concentration in any patient was 3.76 micrograms/ml, at 10 minutes. Three patients reported symptoms of mild neurotoxicity, and their mean peak level was higher at 2.70 micrograms/ml (SD 0.46). What the study establishes is that a bilateral block — a large volume of local anaesthetic injected between the muscles of the abdominal wall, at a weight-based dose — can raise plasma ropivacaine to concentrations that may be associated with neurotoxicity. So the quantity to think about is the total dose across both sides rather than the dose per side, systemic absorption rather than needle placement is what limits it, and the patient is worth watching through the first half hour when the peak arrives. The authors also note pharmacokinetic reasons why pregnancy may increase susceptibility to local anaesthetic toxicity — background they cite for studying this population, not something this study measured.

The three symptomatic patients differed from the rest in plasma level; the study reports nothing to suggest they differed in technique. A fascial plane block has no aspiration test that protects you from absorption, and the mean peak arrived at about 30 minutes — often after the patient has left theatre.