Regional blocks for pre-emptive anti-emesis
It was immensely interesting to read the original research article by Bansal et al. that presents the critical and innovative perspective of peri-anesthesia management. It has been my subjective understanding based on my observations that the surgical handling and stimulation of the eye globe, breasts and testicles elicit nauseating responses in the patients. This leads to postoperative nausea and vomiting (PONV) in these patients in varying degrees depending on the pre-existent variable sensitivities of these organs in different individuals and the variable degrees of surgical handling-related stimulation based on the extent of the underlying anatomical disease as well as the proficiency of the surgical team. The existent facts that the incidence and severity of oculo-cardiac reflex are dependent on the variable and graded mechanical stimuli on the extra-ocular muscles reaffirm that mechanical stimuli to these sensitive organs can only be modified but not completely prevented by the surgical team. It seems prudent to assume that these critical, exteriorized (superficial) and hence sensitive organs have evolutionary in-situ dual protective mechanisms: nausea with or without bradyarrhythmia, and pain in response to stimuli. However, there is one aspect that still remains to be investigated whether the afferent output from eyes, breasts and testes primarily elicit either nausea or pain as primary efferent phenomenon to incite individual's attention and protect themselves against unwarranted stimuli or injuries. Therefore, except for the pre-emptive regional blocks instituted universally for the eye, breast and testicular surgeries, there appears to be no other way to abolish the surgically stimulated reflexes: well-known oculo-cardiac as well as (in my words) unappreciated mammo-vagal and orchio-vagal responses. Additionally, these responses cannot be blocked with postoperative regional blocks as the physiological changes and reflexive mechanisms have been initiated to varying degrees intraoperatively that will present as PONV in pre-emptively untreated patients. As wound infiltrations and surgical field/incision local anesthetic blocks can only be accomplished at the end of the surgeries, the clinically significant pre-emptive anti-emesis can only be achieved with pre-incision paravertebral/epidural blocks for mastectomies and pre-incision caudal/epidural/spinal/spermatic cord blocks for adult or pediatric testicular surgeries; however, peri-bulbar/retro-bulbar blocks for eye-muscle surgeries may have a concern for counter-productive surgical results in terms of the inadequate corrections of heterotropia. In summary, the observations of Bansal et al. present a landmark research that will instigate the initiatives for regional nerve blocks in high-risk surgeries as a pre-emptive anti-emetic technique relegating the analgesia achieved as a secondary gain from these blocks.
1. Bansal P, Saxena KN, Taneja B, Sareen B. A comparative randomized study of paravertebral block versus wound infiltration of bupivacaine in modified radical mastectomy J Anaesthesiol Clin Pharmacol. 2012;28:76–80
2. Khurana I, Sharma R, Khurana AK. Experimental study of oculocardiac reflex (OCR) with graded stimuli Indian J Physiol Pharmacol. 2006;50:152–6
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3. Mennella JA, Pepino MY. Breast pumping and lactational state exert differential effects on ethanol pharmacokinetics Alcohol. 2010;44:141–8