Description of the condition
Postoperative pain is a barrier to quality of paediatric care and the proper management of this experience is a challenge. Acute pain often leads to adverse functional and organic consequences that may compromise surgical outcome. During the postoperative period, acute pain can also lead to psychological, cardiorespiratory and metabolic repercussions (Helgadóttir 2000). The cleft lip is one of the most common craniofacial birth defects and requires surgical correction in early ages (Arosarena 2007).
The connective tissue and skeleton of the face form during the third week of embryonic life by the migration of neural crest cells. Cleft lip is caused by failure in the fusion of the frontonasal and maxillary processes which takes place between the fourth and eighth weeks of embryonic development (Shkokani 2013). The abnormal sequence of lip development can lead to abnormal positioning of the tongue and affect palatal development. Although often associated, cleft lip and palate are different malformations, both embryologically and etiologically. Cleft lip may be part of a genetic syndrome or associated with other birth defects (Sykes 2005). Orofacial clefting is estimated to affect one in 500 to 700 live births. It is more frequent in Asians and Native Americans and in boys (60% to 80%) (WHO 2004). Cleft lip is associated with cleft palate in 68% to 86% of cases (Arosarena 2007).
In 70% of the cases, cleft lip and palate are not associated with genetic syndromes. Genetic predisposition, environmental factors and teratogenic agents (e.g. maternal smoking, zinc and folate deficiency, alcohol, pesticides, chemical solvents, antiepileptic drugs, etc.) have been investigated as potential causes or risk factors for orofacial clefts (Mossey 2009). It is possible to identify cleft lip on prenatal ultrasounds, starting at approximately 18 weeks' gestation, although sensitivity is still low, especially on two-dimensional ultrasound. In cases of suspected cleft lip on ultrasound, the patient should be seen by maternal-foetal specialists, and genetic counselling is recommended (Gagnon 2009).
The varied morphology of facial clefts, which may involve four different structures (the upper lip, alveolar process, hard and soft palate) and the possibility of unilateral or bilateral, complete or incomplete involvement, are challenges to the creation of a single classification (Rodriguez 2001). Regardless of the extension of the clefts, early surgical repair must be planned to minimise physical, psychological and social consequences. Affected individuals may have feeding and speech problems, in addition to increased risks of middle ear infections. The condition is associated with increased mortality from many causes and the aesthetic defect may cause social rejection and decreased quality of life (Law 2002; Shkokani 2013).
Surgical correction of cleft lip can be performed during the neonatal period or later. The ideal period for surgery depends on the severity of the deformity, the child's health and other factors that may influence the efficacy and safety of the procedure (Shkokani 2013). There is a consensus that the correction should be carried out as early as possible and it is often performed between the third and sixth months of life (Delgado 2005; Sykes 2005). The management of cleft lip involves a multi-disciplinary team to ensure comprehensive care including functional and aesthetic issues. There are several different treatment plans for the surgical correction of the deformity (Mathes 2006).
As expected after a surgical intervention in such a sensitive and delicate area, the immediate postoperative period of cleft lip repair may be associated with moderate to severe pain (Augsornwan 2008; Biazon 2008). This pain will require adequate analgesia to prevent the child from becoming agitated and touching the surgical site. This behaviour could disrupt the process of wound healing and compromise the aesthetic results as well as extend the time of hospitalisation.
Description of the intervention
Treatment of acute postoperative pain usually involves the use of non-steroidal anti-inflammatory drugs (NSAIDs), analgesics and oral or intravenous opioids, which may be associated with adverse effects such as nausea and vomiting, drowsiness and respiratory depression. These treatments are frequently underutilised in children due to safety concerns and lack of experience in pain management (Jonnavithula 2007). Another option to control postoperative pain is the injection of local anaesthesia into the surgical incision, but the procedure may distort the margins of the cleft and interfere with the aesthetic repair (Prabhu 1999). In the last two decades there has been a growing interest in regional anaesthesia for paediatric surgical procedures. Several techniques have been evaluated and tested in several types of paediatric surgery, including cleft lip repair (Gaonkar 2004; Jonnavithula 2007; Simion 2008; Takmaz 2009).
Infraorbital nerve block associated with general anaesthesia has been used to reduce postoperative pain after cleft lip repair. The infraorbital nerve is the terminal branch of the second division of the trigeminal nerve which differentiates into the infraorbital nerve after entering the ocular area through the inferior orbital fissure. It emerges through the infraorbital foramen dividing into four branches (inferior palpebral, external nasal, internal nasal, and superior labial), innervating the skin of the upper cheek, the mucous membrane of the maxillary sinus, the incisor, canine and premolar teeth, upper gums, skin and conjunctiva of the lower eyelid, part of the nose, skin and mucosa of the upper lip (Simion 2008).
How the intervention might work
Infraorbital nerve block is performed by injecting an anaesthetic in the infraorbital foramen, either intra- or extraorally (percutaneous). In the percutaneous approach, the infraorbital foramen is identified as a point halfway between the midpoint of palpebral fissure and the angle of the mouth, approximately 7.5 mm from the alar base; then a needle is introduced perpendicular to the skin and advanced until bone resistance is felt. The needle is then withdrawn slightly and after a negative aspiration test for blood, the local anaesthetic is injected (Bosenberg 1995; Takmaz 2009). For intraoral infraorbital nerve block, a finger marks the approximate point of the infraorbital foramen externally, as described above, then the lip is everted and the needle is inserted into the mucobuccal fold above the second premolar toward the infraorbital foramen (Jonnavithula 2007). The injected anaesthetic blocks the generation and propagation of impulses in excitable tissues by blocking sodium channels in the cell receptors. The absence of this ion prevents the transmission of pain sensitivity. This results in effective regional blockage of pain when these drugs are deposited near peripheral nerves, nerve roots, or the spinal cord. The effect of this process will depend on the dose, concentration and type of anaesthetic used (Strichattz 1976).
Why it is important to do this review
There are several procedures to control acute postoperative pain associated with cleft lip repair to ensure the comfort of the child, and to preserve the integrity of the delicate surgical site. Infraorbital nerve block is frequently used because it can provide long-lasting pain relief and avoid the complications associated with pain relief drugs. There is a need to asses and synthesise the evidence available so far on the effectiveness and safety of this procedure.